A rapid scan of the literature · 2010-01-04 · A rapid scan of the literature 26 March 2009...

A rapid scan of the literature

26 March 2009

Screening for the early detection of acoustic neuroma in patients with asymmetric sensorineural hearing loss: a

rapid literature scan of MRI and other surveillance methods

Dan Paech Adele Weston

This report should be referenced as follows:

Paech, D, and Weston, A. Screening for the early detection of acoustic neuroma in

patients with asymmetric sensorineural hearing loss: a rapid literature scan of MRI

and other surveillance methods

HSAC Report 2009; 2(1).

2009 Health Services Assessment Collaboration (HSAC), University of Canterbury

ISBN 978-0-9582973-5-6 (online)

ISBN 978-0-9582973-6-3 (print)

ISSN 1178-5748 (online)

ISSN 1178-573X (print)

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Screening in ASNHL for acoustic neuroma

Review Team

This review was undertaken by the Health Services Assessment Collaboration

(HSAC). HSAC is a collaboration of the Health Sciences Centre of the University of

Canterbury, New Zealand and Health Technology Analysts, Sydney, Australia. This

report was authored by Dan Paech who developed and undertook the literature search,

extracted the data, and prepared the report, and Dr Adele Weston who provided

guidance and reviewed the report.

The current review was conducted under the auspices of a contract funded by the New

Zealand Ministry of Health. This report was requested by Dr Sandy Dawson of New

Zealand’s Ministry of Health. We thank Dr Dawson for assisting in developing the

scope of the review and providing background material for the review.

Copyright Statement & Disclaimer

This report is copyright. Apart from any use as permitted under the Copyright Act

1994, no part may be reproduced by any process without written permission from

HSAC. Requests and inquiries concerning reproduction and rights should be directed

to the Director, Health Services Assessment Collaboration, Health Sciences Centre,

University of Canterbury, Private Bag 4800, Christchurch, New Zealand.

HSAC takes great care to ensure the accuracy of the information in this report, but

neither HSAC, the University of Canterbury, Health Technology Analysts Pty Ltd nor

the Ministry of Health make any representations or warranties in respect of the

accuracy or quality of the information, or accept responsibility for the accuracy,

correctness, completeness or use of this report.

The reader should always consult the original database from which each abstract is

derived along with the original articles before making decisions based on a document

or abstract. All responsibility for action based on any information in this report rests

with the reader.

This report is not intended to be used as personal health advice. People seeking

individual medical advice should contact their physician or health professional.

The views expressed in this report are those of HSAC and do not necessarily represent

those of the University of Canterbury New Zealand, Health Technology Analysts Pty

Ltd, Australia or the Ministry of Health.

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Contact Details

Health Services Assessment Collaboration (HSAC)

Health Sciences Centre

University of Canterbury

Private Bag 4800

Christchurch 8140

New Zealand

Tel: +64 3 345 8147 Fax: +64 3 345 8191

Email: [email protected]

Web Site: www.healthsac.net

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Executive Summary

Introduction

This report provides a brief scan of the literature available on the role of magnetic

resonance imaging (MRI) and comparative surveillance techniques in screening for

the early detection of acoustic neuroma (AN) in patients with asymmetric

sensorineural hearing loss (ASNHL). It was commissioned by the New Zealand

Ministry of Health.

Methods

A systematic method of literature searching and study selection was employed in the

preparation of this report. The literature was searched using the bibliographic

databases of EMBASE and Medline. The Cochrane Database of Systematic Reviews

and numerous health technology assessment websites were also searched to help

identify existing reviews or clinical practice guidelines. In addition, the bibliographies

of key included papers were examined for relevant studies. It is important to note that

as this was a brief scan of the evidence, and not a full systematic review, detailed

quality appraisal, data extraction and interpretation of the identified literature was not

performed. The review relies heavily upon material reported in each publication’s

abstract.

Key results

The search strategy identified a total of 451 citations, of which 289 were included for

title/abstract review. After consideration of titles and abstracts using the study

selection criteria, 53 citations were included in the review. Only the papers of the

citations considered most relevant to the topic of interest were retrieved for more in-

depth description. There was also one systematic review identified which is due for

publication in April 2009. All available details of this review are provided.

The literature gathered in this report suggests that MRI is considered the ‘gold

standard’ in detecting ANs in patients with ASNHL. Although auditory brainstem

response (ABR) testing is also widely used, it has been shown to have insufficient

sensitivity and specificity to be used as a sole screening test. There is particular

concern around its ability to identify small sized tumours. Nonetheless, there appears

to be significant variety in the way clinicians screen and manage patients presenting

with ASNHL. This may be due to the fact that there are no universally accepted

clinical practice guidelines, and because of the accessibility and cost issues of

screening all patients with MRI. Whether or not MRI maintains its superiority once

costs are taken into account has not been addressed in this report.

Conclusions

The review concludes with suggested directions of action and potential research

questions for this topic.

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Table of Contents

Review Team ................................................................................................................. i

Copyright Statement & Disclaimer ............................................................................. i

Contact Details ............................................................................................................. ii

Executive Summary .................................................................................................... iii

Introduction ............................................................................................................... iii

Methods ..................................................................................................................... iii

Key results ................................................................................................................. iii

Conclusions ............................................................................................................... iii

Table of Contents ........................................................................................................ iv

List of Tables ................................................................................................................ v

Introduction .................................................................................................................. 1

Literature Search ......................................................................................................... 3

Results ........................................................................................................................... 7

Review of screening techniques ................................................................................. 7

Systematic review ...................................................................................................... 7

Prospective studies ..................................................................................................... 8

Retrospective studies ................................................................................................ 10

Reviews, patient management or clinical practice papers ....................................... 14

Cost based studies .................................................................................................... 17

Key publications ....................................................................................................... 20

Published audiological screening protocols ............................................................. 24

Summary and Recommendations ............................................................................. 27

Conclusions .............................................................................................................. 27

References ................................................................................................................... 29

Appendix A: HTA websites searched ....................................................................... 35

Appendix B: Excluded studies annotated by reason for exclusion ....................... 37

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List of Tables

Table 1 Summary of the literature search .............................................................. 4 Table 2 Criteria for inclusion/exclusion in review ................................................ 4 Table 3 Prospective studies identified through the literature search ..................... 9 Table 4 Summary of retrospective cohort studies ............................................... 11

Table 5 Summary of publications classified as a review, patient management or

clinical practice paper ............................................................................. 14 Table 6 Summary of cost based studies ............................................................... 17 Table 7 Results of MRI and ABR screening tests ............................................... 22 Table 8 A description of published decision-support protocols for acoustic

neuroma .................................................................................................. 25

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Introduction

Hearing loss is the most prevalent sensory deficit reported by patients. In Australia,

10–20% of Australians have some hearing impairment and approximately 50% of

those over 65 years of age are hearing impaired. Hearing loss can be conductive,

sensorineural or mixed, with sensorineural occurring most frequently in adults

(Angeli et al. 2005). Sensorineural hearing loss indicates defects in either the cochlea

or in the neural transmission to the central nervous system. Asymmetric sensorineural

hearing loss (ASNHL) is defined as binaural difference in conduction thresholds of

>10 dB at two consecutive frequencies or >15 dB at one frequency (0.25–8.0 kHz)

(Sabini and Sclafani 2000).

One pathology which may present as ASNHL is acoustic neuroma (AN), also known

as vestibular schwannoma. Acoustic neuroma is a benign tumour arising from the

Schwann cells in the vestibular portion of the eighth cranial nerve. However, the

majority of patients who present with ASNHL do not have AN, the reported incidence

being approximately 2% of all patients with ASNHL (Urben et al. 1999). As a result,

selecting patients with ASNHL for further investigation continues to pose challenges,

given the disparity between the number of symptomatic patients, and the low

incidence of AN as the underlying cause (Nouraei et al. 2007).

When patients present with symptoms that may indicate an AN, magnetic resonance

imaging (MRI) is often considered the diagnostic test of choice. However, there are

some patients for whom MRI is inappropriate (e.g. patients with implanted electrical

devices or a cerebral aneurysm clip), and increasingly there are cost and accessibility

issues associated with MRI (Prasad and Cousins 2008). Contention also surrounds the

most efficient MRI protocol to use in the investigation of suspected AN.

Electrophysiological measurement of the auditory brainstem response (ABR) is

another diagnostic technique which has been used to diagnose AN (National Institute

of Health Research 2007). This report will gather the evidence on MRI, and the place

of any other screening tests, in the early detection of AN.

An extensive literature search was conducted as is described below. The aim of the

literature search was to provide a rapid overview of the available evidence for

screening ASNHL patients for AN, with a particular focus on MRI.

The results of each identified study should be considered with the year of publication

in mind, as significant advances in technology have occurred in AN diagnosis over

the last 20 years.

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3


Literature Search

A search of the EMBASE, Medline and Cochrane database as well as numerous HTA

websites (Appendix A) was conducted to identify any published guidelines,

systematic reviews or publications pertaining to the screening of patients with

ASNHL for the identification of acoustic neuromas. The literature source, search

terms, number of citations identified and date of the search is outlined in Table 1.

Many of the citations identified through the search of the Cochrane library and HTA

websites were duplicates already identified through the EMBASE/Medline search, or

were completely irrelevant to the topic of interest, and were therefore excluded before

downloading into the Reference Manager database.

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Table 1 Summary of the literature search

Source Search terms Citations Date

EMBASE.com (Includes EMBASE and Medline)

(('acoustic neuroma'/exp OR 'acoustic neuroma') OR 'vestibular schwannoma' OR ('neurinoma'/exp OR 'neurinoma')) AND ('asymmetric sensorineural hearing loss' OR 'asymmetric sensori-neural hearing loss' OR ('sensorineural hearing loss'/exp OR 'sensorineural hearing loss') OR 'sensori-neural hearing loss' OR 'asymmetrical sensorineural hearing loss' OR 'asymmetrical sensori-neural hearing loss' OR ('perception deafness'/exp OR 'perception deafness')) AND [english]/lim AND [humans]/lim

281 03/02/2009

Cochrane library ‘Sensorineural hearing loss’ OR ‘vestibular schwannoma’ OR ‘acoustic neuroma’

86 03/02/2009

CADTH ‘Sensorineural hearing loss’ OR ‘vestibular schwannoma’ OR ‘acoustic neuroma’

49 03/02/2009

EuroScan

‘Sensorineural hearing loss’ OR ‘vestibular schwannoma’ OR ‘acoustic neuroma’

20 03/02/2009

National guideline clearinghouse


7 03/02/2009

National Institute for Health Research


6 03/02/2009

NICE ‘Sensorineural hearing loss’ OR ‘vestibular schwannoma’ OR ‘acoustic neuroma’

2 03/02/2009

INAHTA ‘Sensorineural hearing loss’ OR ‘vestibular schwannoma’ OR ‘acoustic neuroma’

0 03/02/2009

MSAC ‘Sensorineural hearing loss’ OR ‘vestibular schwannoma’ OR ‘acoustic neuroma’

0 03/02/2009

ANZHSN ‘Sensorineural hearing loss’ OR ‘vestibular schwannoma’ OR ‘acoustic neuroma’

0 03/02/2009

AHRQ ‘Sensorineural hearing loss’ OR ‘vestibular schwannoma’ OR ‘acoustic neuroma’

0 03/02/2009

Total 451 03/02/2009

Abbreviations: AHRQ, Agency for Healthcare Research and Quality; ANZHSN, Australia and New Zealand Horizon Scanning

Network; CADTH, Canadian Agency for Drugs and Technology in Health; INAHTA, International Network of Agencies for

Health Technology Assessment; MSAC, medical Services Advisory Committee; NICE, National Institute for Clinical Excellence.

In addition, a general internet search was performed to identify any additional

publications, clinical practice guidelines or systematic reviews. There were 289

citations downloaded into the reference manager database from the various sources

described above. The titles and abstracts (where available) were reviewed using the

inclusion and exclusion criteria outlined below in Table 2.

Table 2 Criteria for inclusion/exclusion in review

Reason for exclusion Number of citations excluded

Incorrect study type: case study (<10 patients), opinion piece, letter 69

Incorrect patient population: not ASNHL 68

Incorrect disease: not acoustic neuroma 27

Incorrect intervention/outcomes: does not examine relevant screening technique for acoustic neuroma

72

Included 53

Abbreviations: ASNHL, Asymmetric sensorineural hearing loss.

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After reviewing the citations, there were 53 that qualified for inclusion. One of these

was a systematic review which is due for publication in April 2009. Further details on

the types of publications retrieved and an in-depth description of the forthcoming

systematic review is provided below. The excluded citations and reasons for exclusion

are provided in Appendix B.

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7


Results

Review of screening techniques

The identified studies assessed a number of different surveillance techniques. These

are discussed below.

The initial screening test for assessing patients with ASNHL was the pure tone

audiogram (PTA) (Wareing 2002). Whilst there is no characteristic shape of

audiogram, unexplained asymmetry between the ears warrants further investigation.

In the past, other audiological screening tests such as loudness recruitment, tone

decay, stapedial reflex thresholds and decay have been used as an initial screening

measure although these are now only of historical interest.

Auditory brainstem response testing was first introduced in 1970 and has been used to

identify retrocochlear lesions. It is a safe and painless test of the auditory pathway and

brainstem function in response to auditory stimuli. The ABR test is widely used by

audiologists as an initial screening tool in patients with sensorineural hearing loss.

However, its success rate in ASNHL has been shown to be dependent on tumour size,

with the test at its least sensitive in small and medially placed tumours, these being

the tumours that an early diagnostic strategy aims to detect (Wareing 2002).

Magnetic resonance imaging with gadolinium enhancement has been considered the

‘gold standard’ for detection of ANs since 1991. It has been shown to have a near

100% diagnostic accuracy, being able to detect tumours as small as 3mm. More

recently, screening scan procedures have been developed that either decrease the

gadolinium dose or remove the need for it all together, using T2 fast spin echo (FSE)

scanning protocols. However, some authors argue that using this approach is probably

not justified since other alternative diagnoses may be missed due to the lack of

contrast material. Nevertheless, high-resolution FSE T2-weighted MRI has proven to

be a cost-saving alternative to contrast-enhanced MRI (Vossough 2003). The

disadvantages of MRI relate to the cost of universal screening as well as access to the

scanner.

The use of contrast enhanced computerised tomography (CT) has also been reported

as useful in the diagnosis of AN. However, because bone has a positive signal, its

ability to diagnose intracanalicular tumours is limited and possibly no better than

ABR testing. Its role is currently limited to those patients in whom MRI is

contraindicated (Wareing 2002).

Systematic review

There was one systematic review identified through the literature search. It is

currently being undertaken by the National Institute of Health Research (NIHR) and is

due for publication in April 2009. According to the NIHR webpage, the project is in

the editorial review stage. The title of the systematic review is:

‘The role of magnetic resonance imaging in the identification of suspected acoustic

neuroma: systematic review of clinical and cost effectiveness, and natural history’

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The following summary of the project and proposed publication abstract are taken

from the NIHR webpage.

Summary

Some patients presenting to their general practitioner with unilateral hearing loss and/or tinnitus may have a small tumour called an acoustic neuroma growing on the hearing (acoustic) nerve; estimated to be 3-7.5%. How these tumours grow and the effect they have on an individual varies. Identification of such tumours and assessment of their rate of growth is important clinical information which contributes to decisions on whether or how to treat them.

There exist several different tests that can be used for this assessment, each of which has different accuracy and different costs. There are no current guidelines on which is the most clinically- and cost-effective to use.

We propose to identify existing published and unpublished literature and to extract all the relevant evidence which will contribute to answering questions on how acoustic neuromas grow and affect individuals, which diagnostic tests are better and what are the costs involved. Only by evaluating the existing evidence can we see if there are gaps in our knowledge which need to be answered by further research. The proposed research will not raise ethical issues and will not require NHS ethical approval.

The base for the research will be the University of Nottingham. Co-applicants are based in Birmingham, Liverpool, Cambridge, Belfast, and Athens. Our team comprises experts in various aspects of this field, including methodological experts who will reach a consensus based on the evidence. Each will review aspects of the evidence for which they have expert knowledge and each will contribute to the final report. The costs requested are to employ a research assistant to carry out the searches and identify the available evidence. In addition we are requesting funds for consultancy for the expert reviewers and co-ordinators to allow them to dedicate sufficient time to the project, travel costs for meetings of the whole team and for consultancy meetings between the researcher and the experts, and consumable costs of acquiring the literature that is not available on the internet.

Abstract

The aim of the study is to (i) evaluate the clinical- and cost-effectiveness of a range of diagnostic strategies for investigating patients with unilateral hearing loss and/or sudden-onset tinnitus with a view to confirming or eliminating a diagnosis of acoustic neuroma, (ii) to describe the natural history of acoustic neuroma and (iii) to synthesise the findings from these two elements of the study to formulate guidelines for clinical practice and to identify priorities for future primary research in this area.

We propose to identify existing published and unpublished literature and to extract all the relevant evidence which will contribute to answering the questions of how do acoustic neuromas grow and affect individuals, the diagnostic accuracy and performance (e.g. yield) of different tests and combinations of tests that investigate unilateral hearing loss/tinnitus (i.e. magnetic resonance imaging, hearing tests, computed tomography scans, auditory brainstem response testing) including the outcomes of interventions and the cost-effectiveness of MRI compared with other diagnostic tests for the investigation of unilateral hearing loss and/or tinnitus. These questions will be examined in terms of different case definitions, tumour size and different protocols of tests. Each review will be conducted in accord with contemporary methodological standards for systematic reviews (e.g. Cochrane diagnostic screening Methods Group, NHS Centre for Reviews & Dissemination systematic review guidelines).

Data source: National Institute of Health Research 2009

Abbreviations: MRI, magnetic resonance imaging; NHS, National Health Service

Prospective studies

There were eight prospective studies assessing a number of different surveillance

techniques identified through the literature search. The citation details for these, along

with a summary of each publication are provided in Table 3. Where possible,

publications are further grouped by screening intervention type.

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Table 3 Prospective studies identified through the

literature search

Reference Abstract / Summary

ABR

Cueva RA. (2004) Auditory brainstem response versus magnetic resonance imaging for the evaluation of asymmetric sensorineural hearing loss. Laryngoscope 114:1686-1692.

ABR vs MRI

ABR testing and MRI are compared for the evaluation of patients with ASNHL. This study is a prospective, nonrandomised comparison of ABR and MRI for the evaluation of patients with asymmetric SNHL. Further details are provided under the Key Publications section.

Ruckenstein MJ, Cueva RA, Morrison DH, and Press G. (1996) A prospective study of ABR and MRI in the screening for vestibular schwannomas. American Journal of Otology 17:317-320.

ABR vs ABR + MRI

This study reports on the preliminary results of an ongoing prospective study on the evaluation of patients with ASNHL. All patients with asymmetry in two or more pure-tone thresholds of (greater-than or equal to)15 dB or asymmetry in speech discrimination scores of (greater-than or equal to)15% or both entered the study and underwent both an ABR examination and an enhanced MRI scan. Further details are provided under the Key Publications section.

Swan IRC. (1989) Diagnostic vetting of individuals with asymmetric sensorineural hearing impairments. Journal of Laryngology and Otology 103:823-826.

ABR, acoustic reflex, alternative binaural loudness balance, ENG and caloric testing + CT

This study aimed to assess the efficiency of various tests in excluding CPA tumours with the minimum of unnecessary investigations. All patients received the full battery of ABR, acoustic reflex thresholds and decay, alternate binaural loudness balance and ENG and caloric testing. All patients who did not have normal ABR proceeded to high resolution CT scanning. The efficiency of these tests in a general ORL clinic is very much poorer than often suggested, due largely to the number of occasions on which the tests cannot be done, and to the very small proportion of the test population who have CPA tumours.

MRI

Annesley-Williams DJ, Laitt RD, Jenkins JPR, Ramsden RT, and Gillespie JE. (2001) Magnetic resonance imaging in the investigation of sensorineural hearing loss: Is contrast enhancement still necessary? Journal of Laryngology and Otology 115:14-21.

FSE-T2W MRI vs Gd-T1W MRI

Over a 22-month period the use of axial turbo-spin echo T2-weighted images (T2w) were prospectively compared with contrast-enhanced T1-weighted spin echo scans in the evaluation of 513 patients presenting with audiovestibular symptoms. With the 3-D sequence three ANs were all identified correctly with no false positive and only one false negative result. Authors concluded that mass lesions of the IAM/CPA can be reliably identified on T2w TSE imaging but labyrinthine lesions may be missed without contrast enhancement.

Zealley IA, Cooper RC, Clifford KM, Campbell RS, Potterton AJ, Zammit-Maempal I, Baudouin CJ, and Coulthard AJ. (2000) MRI screening for acoustic neuroma: a comparison of fast spin echo and contrast enhanced imaging in 1233 patients. The British Journal of Radiology 73:247.

Gd-T1W MRI vs FSE-T2W MRI

In order to determine the utility of fast spin echo imaging, both gadolinium enhanced T1 weighted images and fast spin echo T2 weighted images were acquired in 1233 consecutive patients referred for exclusion of AN. Thirty three ANs were identified. Only 56% were confidently identified on fast spin echo T2 weighted images alone; gadolinium enhanced T1 weighted images were required to confirm the diagnosis in 44% of the cases, including 9 of the 10 intracanalicular tumours. It was concluded that an imaging strategy intended to identify small intracanalicular ANs cannot rely on fast spin echo T2 weighted imaging alone.

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Table 3 Prospective studies identified through the

literature search (continued)


Adler J, Atlas M and Shnier R. (1998) High resolution MRI and asymmetric sensori-neural hearing loss. Australian Journal of Oto-Laryngology. FindArticles.com. 09 Feb, 2009.

FSE-MRI vs Gd-T1W MRI

The present study examined the suitability of a high resolution fast spin echo (FSE) sequence, combined with a whole head FSE sequence, in the screening evaluation of 39 consecutive patient's referred with a diagnosis of ASNHL. The efficacy of the sequences was compared with standard MRI which included T1 weighted gadolinium enhanced scans. Whilst there were no significant differences in the imaging diagnoses achieved with the FSE sequences when compared to standard protocols, the incidence of acoustic tumour in this unselected series (4%) was too low to allow a definitive judgement with respect to the value of the FSE sequences as a stand-alone screening tool.

Soulie D, Cordoliani YS, Vignaud J, and Cosnard G. (1997) MR imaging of acoustic neuroma with high resolution fast spin echo T2-weighted sequence. European Journal of Radiology 24:61-65.

FSE-T2W MRI vs Gd-T1W MRI

The aim of this study was to assess the value of high resolution 2D fast spin echo T2-weighted sequence (HR 2D-FSE T2W) for evaluating the internal auditory meatus in patients with asymmetric or unilateral sensorineural hearing loss, vs. gadolinium-enhanced T1-weighted (T1w) sequence; to suggest a screening protocol to exclude the diagnosis of AN in a patient with isolated unilateral sensorineural hearing loss. Normal images using HR 2D-FSE T2w sequence can rule out the diagnosis of AN. Using this protocol authors could exclude the diagnosis of AN in case of normal HR 2D-FSE images and no additional gadolinium-enhanced T1w sequence is necessary.

Bassi P, Piazza P, Cusmano F, Menozzi R, Gandolfi A, and Zini C. (1989) MR cisternography of the cerebello-pontine angle and internal auditory canal in diagnosis of intracanalicular acoustic neuroma. Neuroradiology 31:486-491.

T1W + T2W MRI

115 patients, suffering from SNHL were tested with a 1.5 T superconducting magnet. The authors describe utility of both T1-weighted multiple slice and T2-weighted multiple echo images for the evaluation of cerebello-pontine angle, internal auditory canal and their neurovascular content. In 73 cases MR cisternography was normal. The remaining 42 cases were subdivided into twenty extracanalicular masses, eleven small intra-extracanalicular and nine purely intracanalicular lesions. All the lesions were histologically proven ANs, except one intracanalicular mass which was a meningioma. Examination was inconclusive only in two cases and decision was then made to follow the clinical course. Advantages of MR cisternography over CT and air CT cisternography are pointed out.

Abbreviations: ABR, audio brainstem response; ASNHL, asymmetric sensorineural hearing loss; CPA, cerebellopontine angle

CT; computed tomography; ENG, electronystagmogram; FSE, fast spin echo; IAM, internal auditory meatus; MRI, magnetic resonance imaging; ORL, ;T2W, T-2 weighted; TSE, turbo spin echo.

Retrospective studies

There were 17 studies which retrospectively assessed various surveillance techniques

for AN. The citation details and a summary for each are shown below in Table 4.

Again, publications have been grouped according to the screening intervention.

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Table 4 Summary of retrospective cohort studies

References Abstract / Summary

ABR

Montaguti M, Bergonzoni C, Zanetti MA, and Rinaldi Ceroni A. (2007) Comparative evaluation of ABR abnormalities in patients with and without neurinoma of VIII cranial nerve. Acta otorhinolaryngologica Italica: organo ufficiale della Societa italiana di otorinolaringologia e chirurgia cervico-facciale 27:68-72.

ABR

To contribute to the clinical use ABR, in particular with the aim of reducing the number of false positives, a retrospective study was carried out in two groups of patients affected by unilateral SNHL with ABR abnormalities: in the first group (50 cases: true positives) hearing loss was the expression of an AN shown by MRI, in the second group (130: false positives) MRI was negative. The study concluded it would not appear possible, based on current knowledge, to further improve the reliability of this test, and, therefore, its use in oto-neurological diagnostics remains limited.

Schmidt RJ, Sataloff RT, Newman J, Spiegel JR, Myers DL. (2001) The sensitivity of auditory brainstem response testing for the diagnosis of acoustic neuromas. Archives of Otolaryngology. Head and Neck Surgery 127(1):19-22.

ABR

The aim of this study was to determine the sensitivity of ABR testing for detecting ANs and to determine whether the test is less sensitive for detecting small tumours. Retrospective review of the medical charts of 58 patients with AN who had all of the data necessary for inclusion in the study. Authors concluded that ABR testing cannot be relied on for detection of small ANs and should not be used as a criterion to determine whether MRI should be performed when an AN is suspected clinically.

El Kashlan HK, Eisenmann D, and Kileny PR. (2000) Auditory brain stem response in small acoustic neuromas. Ear and Hearing 21:257-262.

ABR

The ABR has been criticised recently as an insensitive measure for the detection of small AN. This study was undertaken to evaluate the experience with the efficacy of ABR in detection of small tumours. Authors conclude that with strict adherence to optimal technique and evaluation criteria, the ABR remains a viable option for AN screening, especially in elderly patients or when there is a low index of suspicion.

Saunders JE, Luxford WM, Devgan KK, and Fetterman BL. (1995) Sudden hearing loss in acoustic neuroma patients. Otolaryngology - Head and Neck Surgery 113:23-31.

ABR + Gd-MRI

In a retrospective review of 836 cases of SHL, this study found 13 patients with ANs. The prevalence of ANs for those screened with ABR or MRI was 2.5%. In addition to these 13 patients, 79 AN patients treated in our clinic had well-documented sudden hearing loss as the initial symptom. Hearing loss in these 92 patients ranged from mild to profound. Associated symptoms of pain, facial paraesthesia, or unilateral tinnitus preceding the sudden hearing loss were suggestive of an AN, as was a mid frequency (U-shaped) hearing loss. Because there are no clinical findings that clearly distinguish those patients with ANs from other patients with SHL, authors recommend either an evaluation with ABR or gadolinium-enhanced for any patient with SHL.

Dornhoffer JL, Helms J, and Hoehmann DH. (1994) Presentation and diagnosis of small acoustic tumors. Otolaryngology - Head and Neck Surgery 111:232-235.

ABR

To assess ABR response results as well as clinical and audiologic presentations, a retrospective study of patients treated for small ANs (less than 1 cm) was conducted. Of the 70 patients included in the study, ABR was abnormal in 65 (93%), on the basis of wave V latency prolongation and interaural latency differences. This would indicate that ABR is a valid screening test for ANs, even in early stages of development. The clinical presentation of patients with small ANs was similar to that reported for ANs in general, but with vertigo occurring more frequently in patients with smaller tumours.

12



(continued)


Hashimoto S, Kawase T, Furukawa K, and Takasaka T. (1991) Strategy for the diagnosis of small acoustic neuromas. Acta Oto-Laryngologica, Supplement 481:567-569.

ABR vs CT

ABR has been believed as the most reliable test for the diagnosis of AN despite several reports of false-negatives. In this series, 4 tumours out of 18 tested had normal ABR. The false-negative rate was 22%, which is much higher than expected. In CT, only 11 tumours were recognised. Although the total number is not large, present results clearly suggest the limits of these examinations. At present, HR-MRI is the most reliable diagnostic method for ANs with no false-negative reported; ordinary MRI may have false-negatives.

Telian SA, Kileny PR, Niparko JK, Kemink JL, and Graham MD. (1989) Normal auditory brainstem response in patients with acoustic neuroma. Laryngoscope 99:10-14.

ABR

ABR testing has been a major breakthrough in audiologic screening for AN because of its high degree of sensitivity. Although it is not uncommon for other cerebellopontine angle masses to present with normal ABR findings, reports of eighth nerve tumours with false-negative ABR tests are quite rare. A series of 120 ANs re-sected at the University of Michigan was reviewed and revealed two such patients. These two patients presented with ASNHL and unilateral tinnitus and were found to have completely normal ABR. The diagnosis of AN would have been delayed if a comprehensive evaluation had not been pursued.

Kanzaki J. (1986) Present state of early neurotological diagnosis of acoustic neuroma. ORL 48:193-198.

SR and ABR test

The incidence of cases of AN that are manifested as sudden deafness or progressive sensorineural hearing loss was investigated. The findings of the SR test, the ABR test and the caloric test were analysed, and the procedure for the diagnosis of AN was discussed.

MRI

Mahrous AK and Kalepu R. (2008) Positive findings on MRI in patients with asymmetrical SNHL. European Archives of Oto-Rhino-Laryngology 265:1471-1475.

MRI

This is a retrospective study of 100 consecutive patients who attended an ENT outpatient clinic in a 6 month-period. All of them presented with ASNHL. They were all investigated with MRI scan of the IAM and CPA. The pickup rate was 1% for CPA lesion which was vestibular schwannoma. Further details are provided under the Key Publications section.

Nouraei SAR, Huys QJM, Chatrath P, Powles J, and Harcourt JP. (2007) Screening patients with sensorineural hearing loss for vestibular schwannoma using a Bayesian classifier. Clinical Otolaryngology 32:248-254.

MRI

This study developed and validated a diagnostic model using a generalisation of neural networks, for detecting vestibular schwannomas from clinical and audiological data, and compared its performance with six previously published clinical and audiological decision-support screening protocols. The Gaussian Process Ordinal Regression Classifier increased the flexibility and specificity of the screening process for vestibular schwannoma when applied to a sample of matched patients with and without this condition. If applied prospectively, it could reduce the number of 'normal' magnetic resonance scans by as much as 30% without reducing detection sensitivity. Further details are provided under the Key Publications section.

13



(continued)


Baker R, Stevens-King A, Bhat N, and Leong P. (2003) Should patients with asymmetrical noise-induced hearing loss be screened for vestibular schwannomas? Clinical Otolaryngology and Allied Sciences 28:346-351.

MRI

Those patients with ASNHL are routinely screened for vestibular schwannomas by MRI scanning. Scan reports from the past 5 years have been reviewed and out of 152 scans, four revealed vestibular schwannomas giving a pick-up rate of 2.5%, which compares favourably with other published pick-up rates. Review of the audiograms in these cases suggests that they can be misleading in this context. The conclusion is that patients with noise-induced ASNHL should be screened for ANs.

Kubo T, Sakashita T, Kusuki M, Kyunai K, Ueno K, Hikawa C, Wada T, and Nakai Y. (2000) Evaluation of radiological examination for sensorineural hearing loss. Acta Oto-Laryngologica, Supplement -:34-38.

X-ray, CT and MRI

In this study, the clinical significance of radiological examinations for SNHL was evaluated and the value of their utilisation was reconsidered. A total of 1,276 ears of 724 patients who demonstrated unilateral or bilateral SNHL was studied retrospectively. Findings of radiological examinations such as plain X-ray (X-p), CT and MRI of the brain or the temporal bone were investigated. Temporal bone X-p was usually performed to rule out acoustic tumours. CT was further performed in 119 patients (16.4%) and MRI in 84 patients (11.6%) in total. Of five cases with AN, two with a small tumour exhibited normal findings for the internal auditory canal on temporal bone X-p. These small tumours were finally confirmed by MRI. These findings confirmed that MRI is very useful for detecting small acoustic tumours and suggested that MRI also reveals cerebral vascular insufficiency in patients with SNHL.

Manfre L, Angileri T, Ferrara S, Accardi M, Raineri R, and Lagalla R. (1997) The role of magnetic resonance imaging in central hearing deficits: Beyond the acoustic schwannoma. Rivista di Neuroradiologia 10:409-416.

MRI

This study retrospectively examined 72 patients complaining of different clinical syndromes and SNHL or different kinds of acoustic impairment who underwent MRI brain study excluding the presence of acoustic schwannoma and other CPA masses. In conclusion, although AN was the most common cause of acquired hearing deficit, a lesion involving the neural centres of the acoustic pathway can also determine SNHL. Considering the high sensitivity of MRI in the detection of acoustic intra-axial pathway lesions, an in-depth MRI examination of the brain stem and the temporal lobe is mandatory when SNHL occur in patients not affected by acoustic schwannoma.

Levy RA and Arts HA. (1996) Predicting neuroradiologic outcome in patients referred for audiovestibular dysfunction. American Journal of Neuroradiology 17:1717-1724.

Audiovestibular testing and MRI

This study retrospectively reviewed the neuroimaging studies, results of audiometric and vestibular testing, and medical records of 118 patients to rule out AN. Patients' presentation and results of audiometric and vestibular testing were associated with either a positive or negative neuroimaging outcome. Clinical presentation and audiovestibular testing could not sensitively predict the outcome of neuroimaging in our cohort of patients referred for audiovestibular dysfunction.

Stack JP, Ramsden RT, Antoun NM, Lye RH, Isherwood I, and Jenkins JP. (1988) Magnetic resonance imaging of acoustic neuromas: the role of gadolinium-DTPA. The British Journal of Radiology 61:800-805.

Gd-MRI

MRI was performed in 20 patients with evidence on CT of 21 ANs before and after intravenous administration of gadolinium-diethylene-triamine-pentaacetic acid (Gd-DTPA). The authors concluded that MRI with gadolinium-DTPA is a relatively quick, safe, well tolerated and effective method for the diagnosis of AN.

14



(continued)


Curati WL, Graif M, Kingsley D, King T, Scholtz C, and Steiner R. (1986) MRI in acoustic neuroma: a review of 35 patients. Neuroradiology 28:208-214.

MRI vs CT

This retrospective study is aimed to assess the diagnostic efficacy of MRI in relation to contrast enhanced CT and air-CT-cisternography. The results suggested that MRI was the best non invasive technique for demonstrating ANs.

Chaimoff M, Nageris BI, Sulkes J, Spitzer T, and Kalmanowitz M. (1999) Sudden hearing loss as a presenting symptom of acoustic neuroma. American Journal of Otolaryngology - Head and Neck Medicine and Surgery 20:157-160.

DISC test, ABR, acoustic reflex

This paper describes the incidence of AN presenting as sudden hearing loss (SHL) and the effectiveness of the discrimination (DISC) test, the brainstem-evoked response, and acoustic reflex (AR) test in predicting AN in patients with SHL. The DISC test is a useful screening tool for acoustic tumour, whereas the brainstem-evoked response test shows poorer results in affected patients with sensorineural hearing loss than in other subgroups with different signs of AN. Authors recommend that young patients presenting with mild SHL who have normal results on the AR and brainstem-evoked response tests undergo MRI to rule out CPA tumour.

Abbreviations: ABR, audio brainstem response; AN, acoustic neuroma; ASNHL, asymmetric sensorineural hearing loss; CPA,

cerebellopontine angle CT; computed tomography; DISC, discrimination; ENT, ear nose throat; IAM, internal auditory meatus; MRI, magnetic resonance imaging; SNHL, sensorineural hearing loss; SHL, sudden hearing loss; SR, stapedius reflex; X-p, X-

ray.

Reviews, patient management or clinical practice papers

Of the 53 included citations, 15 were grouped under review, patient management, or

clinical practice associated with the diagnosis of AN. The reference for the

publication and a brief summary of the study is provided below in Table 5. Where

possible, similar publications have been grouped together.

Table 5 Summary of publications classified as a review,

patient management or clinical practice paper

Reference Abstract/Summary

Monsell EM and Rock JP. (1990) Sensorineural hearing loss and the diagnosis of acoustic neuroma. Henry Ford Hospital Medical Journal 38:9-12.

AN management (R)

ANs can now be detected when they are small, and early microsurgical removal results in the lowest overall morbidity. These authors examine the historical development of AN management; discuss current diagnosis and treatment, and present illustrative cases from recent experience. Complaints of tinnitus and hearing loss, especially when unilateral, require appropriate medical evaluation.

Morley S and Beale TJ. (2007) Imaging of deafness and tinnitus. Imaging 19:55-70.

Imaging acoustic neuroma (R)

This paper reviews the clinical features of hearing loss which suggest that imaging is warranted. The imaging features of the main causes of sensorineural deafness are reviewed, with particular focus on imaging vestibular schwannoma. The pathologies that result in tinnitus overlap with those causing sensorineural deafness. This article pays particular attention to the imaging of tinnitus caused by glomus tumours and vascular causes, such as aberrant vessels and arteriovenous malformations.

15




(continued)


Swartz JD. (2004) Lesions of the cerebellopontine angle and internal auditory canal: diagnosis and differential diagnosis. Seminars in ultrasound, CT, and MR 25:332-352.

Diagnostic review (R)

There is a wide variety of differential diagnostic possibilities that must be considered when viewing images of patients with sensorineural hearing loss, vertigo, and dizziness. This communication was intended to provide the reader with an approach to this problem. Detailed anatomy of the region is also included in this communication.

Isaacson JE and Vora NM. (2003) Differential diagnosis and treatment of hearing loss. American Family Physician 68:1125-1132.

Causes and diagnostic review (R)

This paper reviews causes of hearing loss, diagnostic techniques and treatment. It includes both conductive and sensorineural hearing loss.

Vossough A. (2003) Imaging evaluation of sensorineural hearing loss. Applied Radiology 32:6-14.

Diagnosis and management (PM)

This article reviews the diagnosis and management of hearing loss with a particular focus on imaging findings in patients with SNHL.

Spoelhof GD. (1995) When to suspect an acoustic neuroma. American Family Physician 52:1768-1774.

Diagnosis and treatment (PM)

This publication reviews diagnosis and treatment for patients with suspected AN. Patients with ASNHL or unilateral tinnitus should be evaluated expeditiously to prevent further neurologic damage. Gadolinium- enhanced MRI is the best tool for making the diagnosis of AN. Surgical removal using a translabyrinthine approach is the favoured treatment, although radiation therapy and expectant management may be chosen for patients at high surgical risk.

Obholzer RJ and Harcourt JP. (2004) Magnetic resonance imaging for vestibular schwannoma: analysis of published protocols. The Journal of Laryngology and Otology. 118:329-332.

Protocol for MRI selection (CP)

This study seeks to define the most appropriate guidelines for selection of patients for MRI to exclude a vestibular schwannoma. All MRIs of the internal auditory meatus, performed during 2000, were reviewed. Further details are provided under the Key Publications section.

Sheppard IJ, Milford CA, and Anslow P. (1995) MRI in the detection of acoustic neuromas- a suggested protocol for screening. Clinical Otolaryngology & Allied Sciences 21:301-304.

Protocol for MRI selection (CP)

Authors suggest, based on a retrospective review of AN cases, that the entry protocol for MRI screening be limited to patients up to 70 years of age presenting with unilateral audiovestibular symptoms in the absence of significant neurological symptoms or signs, with an average difference in hearing threshold of 15 dB between normal and symptomatic ears or unilateral tinnitus with normal hearing. Further details are provided under the Key Publications section.

Thomsen J and Tos M. (1993) Management of acoustic neuromas. Annales d'Oto-Laryngologie et de Chirurgie Cervico-Faciale 110:179-191.

Protocol for screening (CP)

A survey of the management of ANs in the broadest sense is given. The paper recommends all patients with hearing better than 70-80 dB should be subjected to ABR audiometry, and if there is any doubt about the normality of the response, the patient should proceed to MRI. Patients with poor hearing should go directly to MRI. The advantages and disadvantages of the different surgical approaches are described and an electric treatment algorithm is outlined.

Kanzaki J, Ogawa K, Tsuchihashi N, Yamamoto M, Ogawa S, and Uchi T. (1991) Diagnostic procedure for acoustic neuroma. Acta Oto-Laryngologica, Supplement 487:114-119.


The authors' diagnostic procedure for unilateral AN and the reasoning behind it are explained. At present, pure tone audiometry and simple radiographic imaging of the internal auditory canal are first carried out. Then, if the hearing level (average hearing at 4 kHz and 8 kHz) is 70 dB or lower, ABR audiometry is carried out. If it is 71 dB or higher, the patient is examined by MRI or CT. Contrast-enhanced CT is carried out when MRI is not available.

16




(continued)


Smith IM, Turnbull LW, Sellar RJ, Murray JAM, and Best JJK. (1990) A modified screening protocol for the diagnosis of acoustic neuromas. Clinical Otolaryngology and Allied Sciences 15:167-171.


This paper reviews current protocol for preliminary screening for AN. The current method is a combination of caloric tests, tomography of the internal auditory meati and ABR audiometry with 2 positive results indicating the need for further investigation. This protocol, although sensitive, lacks specificity and results in a high incidence of normal CT air meatograms. Authors’ devised a weighted system of scoring to avoid subjecting large numbers of normal patients to CT air meatography. The proposed system was derived from screening 61 patients with unilateral sensorineural hearing loss, 24 of whom had an AN. This method reduced the false positive rate of CT air meatography from 68%, using the 2 out of 3 criteria, to 18%, whilst the false negative incidence remained at 8%.

Wright A and Bradford R. (1995) Management of acoustic neuroma. British Medical Journal 311:1141-1144.

Early detection techniques (CP)

This article reviews the investigation of patients presenting with unilateral auditory symptoms including the diagnosis and treatment of abnormalities.

Wareing MJ, Baguley D, and Moffat DA. (2002) Investigations for vestibular schwannoma. CME Bulletin Otorhinolaryngology Head and Neck Surgery 6:12-15.

Early detection techniques (CP)

This review looks at the early detection of vestibular schwannoma. Treatment of smaller tumours results in better outcomes. Advances in imaging, in particular the refinement of MRI techniques, have been responsible for the detection of smaller tumours with near 100% sensitivity. The ABR, previously the mainstay of screening, has been superseded in this role. The optimal protocol for patients suspected of a having a vestibular schwannoma is an MRI scan.

Dawes PJD. (1999) Screening for vestibular schwannoma: Current practice in New Zealand. Australian Journal of Otolaryngology 3:307-310.

Survey of clinical practice (CP)

A clinical practice study surveying New Zealand otolaryngologists was conducted. Results indicated the preferred initial screening modality for diagnosing vestibular schwannoma is MRI. 57% proceed direct to MRI, 24% use ABR audiometry and/or CT to select for MRI, and 17% rely upon their clinical judgement supported by investigations such as speech audiometry, acoustic reflex thresholds and ABR audiometry before requesting further investigation. Further details are provided under the Key Publications section.

Kanzaki J, Ogawa K, Ogawa S, Yamamoto M, Ikeda S, and Uchi T. (1991) Audiological findings in acoustic neuroma. Acta Oto-Laryngologica, Supplement 487:125-132.

Audiological examination (CP)

This paper discusses audiological examinations in the diagnosis of AN. This paper proposes the most sensitive audiological examination is ABR audiometry. Its most useful parameter is the IT5. A U-shaped audiometric configuration suggests AN, since it is seen in 10% of patients with small tumours. Psychological audiometric tests can be excluded from the battery of screening tests since they have low rates of positive diagnosis. Nevertheless, the SR test can be employed as a screening device in cases in which the hearing level at 2 kHz and lower is 70 dB or lower, even if it is 71 dB or higher at 4 kHz and 8 kHz.

Abbreviations: ABR, audio brainstem response; AN, acoustic neuroma; ASNHL, asymmetric sensorineural hearing loss; (CP) =

clinical practice; CT, computed tomography; dB, decibel; KHZ, kilohertz; MRI, magnetic resonance imaging; (PM) = patient management; (R) = review; SNHL, sensorineural hearing loss; SR, stapedius reflex.

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Cost based studies

Retrieved citations that mentioned costing, cost containment or cost-effectiveness in

the diagnosis of AN were grouped together. These papers were identified through the

clinical literature search and are shown below in Table 6. These studies have been

further grouped by the type of screening intervention. The country that the study was

conducted in has also been shown in the reference column of the table.

Table 6 Summary of cost based studies


ABR and MRI

Rupa V, Job A, George M, and Rajshekhar V. (2003) Cost-effective initial screening for vestibular schwannoma: auditory brainstem response or magnetic resonance imaging? Otolaryngology--head and neck surgery: official journal of American Academy of Otolaryngology-Head and Neck Surgery 128:823-828.

Country of study: United States of America

ABR + Gd-MRI

This study aimed to determine the cost-effectiveness of including ABR testing in a screening protocol for the diagnosis of vestibular schwannoma. Patients were investigated prospectively with both ABR and gadolinum-enhanced MRI (GdMRI). A protocol involving screening of all patients with asymmetric audiovestibular symptoms using ABR and only subjecting those patients with no responses or retrocochlear pathology to GdMRI would effect a savings of $1200 for every patient detected to have a VS. Further details are provided under the Key Publications section.

Cheng G, Smith R and Tan AK. (2003) Cost comparison of auditory brainstem response versus magnetic resonance imaging of acoustic neuroma. J Otolaryngol 32(6):394-399.


ABR + MRI/CT

The cost-effectiveness of current diagnostic approaches employed in patients with suspected AN was evaluated. Currently, patients with signs and symptoms suggestive of AN, such as sudden unilateral hearing loss and/or tinnitus, undergo ABR screening tests to rule out this condition. If the ABR is normal, AN can be ruled out. However, if the ABR is abnormal, MRI or CT is necessary to confirm the diagnosis. The total costs of this approach were compared with the estimated costs of straight MRI screening performed on the same patient population.

Robinette MS, Bauch CD, Olsen WO, and Cevette MJ. (2000) Auditory brainstem response and magnetic resonance imaging for acoustic neuromas: costs by prevalence (Brief record). Archives of Otolaryngology. Head and Neck Surgery 126:963-966.


Gd-MRI vs ABR + Gd-MRI

To compare hypothetical costs for identification of ANs when using MRI with gadolinium Gd 64 (MRI-(64)Gd) as a sole diagnostic test and when using ABR testing followed by MRI-( 64)Gd (ABR + MRI-(64)Gd) for those with positive ABR findings. Authors concluded decisions regarding assessment of patients at risk for ANs must be made on a case-by-case basis. Use of ABR + MRI-(64)Gd allows considerable savings when patients are in the intermediate- or low-risk subgroups. New MRI and ABR testing techniques offer promise for reducing costs.

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Table 6 Summary of cost based studies (continued)


Urben SL, Benninger MS, and Gibbens ND. (1999) Asymmetric sensorineural hearing loss in a community-based population. Otolaryngology - Head and Neck Surgery 120:809-814.


ABR vs ABR + radiological examination

A retrospective study of all patients with ASNHL who were evaluated in a community-based general otolaryngology practice was performed. ASNHL was present in 325 patients The charge of diagnosis per AN was more than $41,000. In summary, a small percentage of patients with ASNHL have retrocochlear pathology, and the charge of diagnosis per AN can be excessive. A cost-containment approach for the evaluation and management of patients with ASNHL is proposed. Further details are provided under the Key Publications section.

MRI

Murphy MR and Selesnick SH. (2002) Cost-effective diagnosis of acoustic neuromas: a philosophical, macroeconomic, and technological decision (Brief record). Otolaryngology. Head and Neck Surgery 127:253-259.


Gd-MRI

This study aimed to define the most sensitive techniques of AN diagnosis, to examine their relative costs, and to propose diagnostic modality selection given the rarity of AN incidence and given the other costs that society faces in more commonly encountered diseases. The review found that although MRI with gadolinium remains the most sensitive diagnostic modality in the discovery of AN, its cost may be prohibitive for some societies. The study suggested the modality to use in AN diagnosis is just as much a philosophical and macroeconomic question as a technological one. The cost of a timely diagnosis of ANs must be weighed against using resources for other, more pressing, health concerns.

Verret DJ, Adelson R, and Defatta R. (2006) Asymmetric sensorineural hearing loss evaluation with T2 FSE-MRI in a public hospital. Acta Oto-Laryngologica 126:705-707.


FSE-MRI vs Gd-MRI

The goal of this study was to determine if fast spin echo T2 MRI is similar to gadolinium-enhanced MRI in evaluating ASNHL in a county hospital population. This was a retrospective chart review of all outpatients who underwent gadolinium-enhanced MRI. Cost savings of over $100 000 would have been realised if only T2 FSE protocols had been used. Further details are provided under the Key Publications section.

Daniels RL, Shelton C, and Harnsberger HR. (1998) Ultra high resolution non-enhanced fast spin echo magnetic resonance imaging: Cost-effective screening for acoustic neuroma in patients with sudden sensorineural hearing loss. Otolaryngology - Head and Neck Surgery 119:364-369.


FSE-MRI

Cost analysis was done in the cases of 58 patients with sudden SNHL by comparing the costs for routine workup and screening of AN with the cost of fast spin echo MRI with the use of screening protocols based on literature review. The potential cost savings of evaluating patients with SSHL with fast spin echo MRI for AN was substantial, with a 54% reduction in screening costs. Authors state that fast spin echo MRI has become the most cost-effective method to screen suspected cases of AN at their institution. This is due to improved technology at reduced cost and through eliminating charges for impedance audiometry, ABR testing, and contrast- enhanced MRI.

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Carrier DA and Arriaga MA. (1997) Cost-effective evaluation of asymmetric sensorineural hearing loss with focused magnetic resonance imaging (Structured abstract). Otolaryngology. Head and Neck Surgery 116:567-574.


T1 and T2 MRI

This paper developed a focused MRI sequence for evaluation of patients with ASNHL. The protocol includes a T1-weighted sagittal localizer, pregadolinium and postgadolinium T1-weighted 3-mm contiguous axial slices through the internal auditory canal and the region of the cerebellopontine angle, and T2-weighted axial images through the entire brain. Total scanning time was about 12 minutes, and the estimated cost was $300 to $500. Authors suggested that by eliminating the need for follow-up audiometric or electrophysiologic studies, a focused MRI-based diagnostic scheme is more cost-effective on a cost-per patient basis.

Ravi K, V and Wells SC. (1996) A cost effective screening protocol for vestibular schwannoma in the late 90s (Brief record). Journal of Laryngology. and Otology. 110:1129-1132.

Country of study: United Kingdom

MRI

In a retrospective study, the clinical records of all the patients who presented to the ENT department of Taunton and Somerset NHS Trust with suspected symptoms of VS during the year 1994 were analysed. The cost of confirming or refuting the diagnosis of VS in each patient ranged from £220.72 to £580.31 depending on the number of hospital visits and investigations performed. This study shows that the routine use of MR scanning for detection of VS is cost effective and more effective than the use of conventional tests.

Allen RW, Harnsberger HR, Shelton C, King B, Bell DA, Miller R, Parkin JL, Apfelbaum RI, and Parker D. (1996) Low-cost high-resolution fast spin-echo MR of acoustic schwannoma: An alternative to enhanced conventional spin-echo MRI American Journal of Neuroradiology 17:1205-1210.


FSE-MRI vs T1W-MRI

This paper reviewed the records of 25 patients with pathologically documented acoustic schwannoma and 25 control subjects, all of whom had undergone both enhanced conventional spin-echo MRI and unenhanced fast spin- echo MRI of the cerebellopontine angle/internal auditory canal region. They found no statistically significant difference in the sensitivity and specificity of unenhanced high-resolution fast spin-echo imaging and enhanced T1-weighted conventional spin-echo imaging in the detection of acoustic schwannoma. Authors concluded that the unenhanced high- resolution fast spin-echo technique provides a cost-effective method for the diagnosis of acoustic schwannoma.

Robson AK, Leighton SE, Anslow P, and Milford CA. (1993) MRI as a single screening procedure for acoustic neuroma: a cost effective protocol. Journal of the Royal Society of Medicine 86:455-457.

Country of study: United Kingdom

Audiovestibular investigations vs MRI

A prospective study was set up in a specially designated screening session to audit the cost effectiveness and accuracy of audiovestibular investigations compared to MRI. The total cost of the audiovestibular protocol was £12,545 compared to £12,900 for the MRI protocol, which is a diagnostic and well-tolerated procedure. This study shows that MRI can be cost effective, as well as accurate, when used as a single screening procedure for ANs.

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OTHER

Bance ML, Hyde ML, Malizia K. (1994) Decision and cost analysis in acoustic neuroma diagnosis. J Otolaryngol 23: 109-120

Country of study: Canada

Variety of diagnostic tests

This study seeks to determine the most efficient testing strategy for patients with AN. They develop analytic techniques to allow analysis of diagnostic strategies that included multi-test protocols.

Mangham CA and Welling DB. (1992) Acoustic neuroma: Cost-effective approach [1]. Otolaryngology - Head and Neck Surgery 106:315-316.

Country of study: NA

NA

Abbreviations: ABR, audio brainstem response; AN, acoustic neuroma; ASNHL, asymmetric sensorineural hearing loss; CT;

computed tomography; dB, decibel; ENT, ear nose throat; FSE, fast spin echo; GdMRI, gadolinium enhanced MRI; MRI,

magnetic resonance imaging; NA = not available; NHS, National Health Service; SNHL, sensorineural hearing loss; VS, vestibular schwannoma.

Key publications

A selection of citations, which appeared to have the most relevance for the topic of

interest were requested in full text. Further detail of each study is provided below.

Positive findings on MRI in patients with asymmetrical SNHL (Mahrous and Kalepu 2008)

This was a retrospective study of 100 patients who attended an ENT outpatient clinic

in a six month period in 2006. All patients presented with ASNHL. The case notes of

patients audiograms and symptoms, on which the decision to scan with MRI was

made, were reviewed. There were no guidelines or protocols employed as to when to

request MRI. The mean age of participants was 53 years and there were 53% males

and 47% females. There was one patient diagnosed with acoustic neuroma which

equates to a pick up rate of 1%, a figure lower than that published in other series. The

patient diagnosed with AN was a 61 year old male, with gradual right SNHL for 3

years. The patient had audiogram asymmetry of >15 dB in the frequencies 500-4 kHz.

The MRI showed a 18 x 16mm lesion in the right internal acoustic meatus displacing

the cerebellum and pons. The authors suggest universal screening for AN is debatable

due to the low pick up rate and high expense of MRI. They suggest applying a

protocol to select patients for MRI is worth considering.

Screening patients with sensorineural hearing loss for vestibular schwannoma using a Bayesian classifier (Nouraei et al. 2007)

This study retrospectively examined records of 129 patients with a proven diagnosis

of vestibular schwannoma based on MRI scans, and an equal number of patients in

whom this diagnosis was suspected, but excluded on MRI. There were 130 males and

128 females and the average age at presentation was 53 ± 15 years (± sd; range 16–97

years). On direct questioning, 121 patients (46%) reported unilateral tinnitus and 79

(30%) episodic vertigo. There were significant overlaps in the degree of hearing

threshold asymmetry between patients with and without a vestibular schwannoma

across all frequencies. A Gaussian Process Ordinal Regression Classifier was used to

predict the likelihood of a patient having or not having a vestibular schwannoma on

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the basis of clinical and audiological data. Variables used for analysis included pure

tone thresholds at 250 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz and 8 kHz at the time of

presentation, as well as patient age and sex, and the presence or absence of unilateral

tinnitus or episodic vertigo. The study proved it possible to pre-select sensitivity and

specificity, with an area under the curve of 0.8025. At 95% sensitivity, the trained

system had a specificity of 56%, 30% better than audiological protocols with closest

sensitivities. Authors concluded that if applied prospectively, it could reduce the

number of ‘normal’ MRI scans by as much as 30% without reducing detection

sensitivity.

Asymmetric sensorineural hearing loss evaluation with T2 FSE-MRI in a public hospital (Verret et al. 2006)

The records of patients with ASNHL presenting in a country hospital who underwent

MRI evaluation were examined. As part of the screening process, a GD-enhanced

MRI scan sequence was obtained; however this also included a non-GD-enhanced

FSE T2 sequence. A total of 146 patients were identified with patients ranging from

20–84 years with a mean age of 55 years. There were 56 male and 90 female patients.

Of the 146 MRI scans performed, abnormalities were seen on 71 of them, the majority

of which were inconsequential (e.g. sinonasal disease, gray/white matter changes, and

previous cerebrovascular disease or intracranial procedures). However, none of the

abnormalities were retrocochlear or explained the etiology of the audiological

findings. The authors estimated that the cost of GD-enhanced MRI was US$1200,

with a T2 FSE protocol costing about $415. For this study population, a saving of

US$114 610 would have been realised if only a T2 FSE protocol had been used. The

authors concluded that T2-weighted FSE can be economically beneficial for screening

patients with ASNHL without other neurological findings in a public hospital

population.

Magnetic resonance imaging screening for vestibular schwannoma: analysis of published protocols (Obholzer and Harcourt 2004)

This was a retrospective review of radiology reports from all MRIs of the internal

auditory meatus, performed during the year 2000 at Charing Cross Hospital. The

notes of all patients who had vestibular schwannoma and those of the last 100

‘negative’ scans were requested. The presenting symptoms and pure tone audiograms

were extracted and data were analysed comparing the sensitivity and specificity of

differences in hearing loss at each specific frequency, at any two and any three

frequencies, and utilising six published protocols. Thirty-six patients with vestibular

schwannomas were included and 92 without, eight case notes were unavailable.

Thirty two of the 36 presented with ASNHL, 19 of whom also had tinnitus. Four

criteria had a sensitivity of > 95%; of these the highest specificity (49%) utilised an

interaural difference at two adjacent frequencies of 15 dB in unilateral hearing loss

and 20dB in bilateral asymmetric loss. The most sensitive criterion was a difference

of 15 dB at any frequency (sensitivity 100% and specificity 29%). The optimal

combination of sensitivity and specificity was achieved using a criterion of >15 dB

difference at two adjacent frequencies if the mean threshold in the better ear was ≤30

dB, and 20 dB if greater than 30 dB. This produced 97% sensitivity and 49%

specificity. The application of the best protocol would have reduced the number of

MRI scans requested from 392 to 168, saving 224 patients’ scans.

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Magnetic resonance imaging for the evaluation of asymmetric sensorineural hearing loss (Cueva 2004)

This was a multi-institutional, prospective, non-randomised comparison of ABR and

MRI with gadolinium for the evaluation of patients with ASNHL (defined as ≥15 dB

in 2 or more pure tone thresholds or an asymmetry of ≥15% on speech discrimination

score). There were 312 patients (between the ages of 18 and 87 years) who completed

the study. Patients prospectively underwent both ABR and MRI with the primary

outcome being the presence or absence of retrocochlear pathology. The results of the

two screening tests are shown below in Table 7.

Table 7 Results of MRI and ABR screening tests

MRI

+ Causative lesion - Causative lesion Total

ABR

Abnormal 22 73 95

Normal 9 208 217

Total 31 281 312

Thirty-one (9.94%) patients of the study population of 312 were found on MRI to

have lesions causing their SNHL. Of the 31 patients with causative lesions on MRI

there were 24 vestibular schwannomas. Twenty-two of the 31 patients had abnormal

ABRs, whereas 9 patients (7 with small vestibular schwannomas) had normal ABRs.

This gives an overall false-negative rate for ABR of 29%. The false-positive rate was

found to be 77%. Sensitivity of ABR as a screening test was 71%, and specificity was

74%. The ABR positive predictive value was 23% and negative predictive value was

96%. ABR was been demonstrated to have low sensitivity and specificity in the

evaluation of these patients and cannot be relied on as a screening test for patients

with asymmetric SNHL. Keeping the use of MRI conditional on the results of ABR

will annually result in missed or delayed diagnosis of causative lesions in 29 patients

per 1,000 screened. The author recommends abandoning ABR as a screening test for

asymmetric SNHL and adoption of a focused MRI protocol as the screening test of

choice.

Screening for vestibular schwannoma: current practice in New Zealand (Dawes 1999)

This study reported the results of a questionnaire survey of New Zealand

otolaryngologists. Sixty seven questionnaires were sent. Forty-two replies were

received, three other replies indicated that the member had retired from clinical

practice. The results indicated that 41 clinicians preferred MRI testing for screening

for AN. However, only 29 had locally available imaging equipment. Twenty-four

clinicians used MRI as their first screening test, 10 used ABR and then MRI, 7 used

clinical judgement and other investigations and one used CT scanning only. The

survey also indicated that many clinicians still use ABR and CT as a preliminary

screen to select for MRI because of financial or local political reasons. The author

believes New Zealand would be best served by a single set of vestibular schwannoma

screening guidelines.

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MRI in the detection of acoustic neuromas- a suggested protocol for screening (Sheppard 1996)

During the period September 1990 to September 1993, 920 requests for MRI imaging

of the IAM or cerebellopontine angle were made within the Oxford region. A total of

892 scans were successfully carried out. The symptoms of ENT patients scanned from

the Oxford Department of Otolaryngology included sudden and gradual sensorineural

hearing loss, tinnitus, vertigo, otalgia. Facial numbness and facial palsy. The decision

to scan was based on the presence of asymmetrical audiovestibular symptoms as

outlined by Robson et al. (1993). Initially, all patients had sagittal and axial T,

weighted interleaved images performed after the administration of gadolinium. The

current scanning protocol involves only 3 mm interleaved fast spin echo T, weighted

axial scans. Four millimetres T, weighted images with gadolinium-DTPA

enhancement are used if there is diagnostic doubt.

Of the total number of patients scanned (n = 892), an acoustic neuroma was detected

in 38 (4.26%). Of these patients, 16 were men and 22 women. Of the 38, 18 were

from non-Oxford clinics, 20 from oxford clinics. Those from the Oxford clinic all had

a degree of ASNHL ranging from 15 dB to 92 dB between normal and abnormal ears.

The study suggested a protocol for the selection of MRI which was: those patients up

to 70 years of age presenting with unilateral audiovestibular symptoms in the absence

of significant neurological symptoms or signs, with an average difference in hearing

threshold of 15 dB between normal and symptomatic ears or unilateral tinnitus with

normal hearing.

A prospective study of ABR and MRI in the screening for vestibular schwannomas (Ruckenstein et al. 1996)

This was a prospective study of 47 patients with ASNHL. Adult patients (18 years or

older) with asymmetry in two or more pure-tone thresholds of ≥15 dB were included.

The mean age of patients was 56 years with 19% older than 65 years. All patients

underwent an ABR and enhanced MRI scan. ABRs were considered abnormal if they

demonstrated asymmetric IT5 latencies (asymmetry >0.2ms), abnormal absolute wave

V latencies, or absent or poor waveform morphology. All MRI scans were reviewed

by a neuroradiologist for the presence or absence of retrocochlear disease. The

authors obtained a sensitivity of 63%, specificity of 64%, positive predictive value of

26%, and negative predictive value of 89% for the ABR test. The 3 ANs missed were

all less than 2 cm. The authors concluded that ABR testing was not an ideal screening

test, cautioning, however, that a larger sample size would be required for confirmation

of this assertion.

Cost-effective initial screening for vestibular schwannoma: auditory brainstem response or magnetic resonance imaging? (Rupa et al. 2003)

This study aimed to determine the cost-effectiveness of including ABR testing in a

screening protocol for the diagnosis of AN in patients with asymmetric auditory

symptoms at the Christian Medical College and Hospital, Vellore, India, where,

commonly, patients with AN have tumours greater than 2 cm at the time of diagnosis.

Ninety patients who presented to the ENT Department with asymmetric auditory

symptoms of hearing loss and tinnitus were prospectively evaluated by pure tone

audiometry, ABR testing, and gadolinium-enhanced MRI (GdMRI) of the temporal

bone and brain. Of a total of 90 patients enrolled in the study, 56 were males and 34

24


females (age range, 15 to 66 years). Of the 30 patients who were found to have

retrocochlear pathology on ABR, 4 patients were diagnosed as having AN.

The study indicated that the cost of GdMRI was approximately 15 times the cost of

ABR. Thus, if all 90 patients had undergone GdMRI alone, the total cost of

investigation would have been $18,000. If only the 48 patients who had either no

response or evidence of retrocochlear pathology on ABR underwent GdMRI, the cost

of screening would have been $9,600. Therefore, a protocol involving screening all

patients with ABR and only subjecting those patients with no response or

retrocochlear pathology on ABR to MRI would save up to $7,200 in total. Because 6

patients with AN were identified, the saving in cost per patient diagnosed correctly

was $1,200. This would be the approximate total cost of having the tumour surgically

excised at this hospital. The authors concluded that the financial burden of identifying

patients with AN could be considerably reduced with a screening protocol including

ABR.

Asymmetric sensorineural hearing loss in a community-based population (Urben et al. 1999)

This was a 5-year retrospective study that examined patients older than 17 years with

ASNHL (defined as an interaural difference in pure-tone thresholds ≥10 dB at 2

frequencies or ≥15 dB at 1 frequency. The study also conducted a cost analysis for

diagnosing AN. All patients’ medical records and audiograms were reviewed for

demographic, historic, and audiologic data and results from ABRs and radiologic

studies. Of all the audiograms reviewed, 193 (21%) met the audiological criteria for

ASNHL. Patients with ASNHL were a median age of 51 years, with 66% male and

34% female.

Among the 193 patients who had diagnostic studies, 4 were found to have ANs, for a

prevalence of 2.1%. ABR tests were performed in 179 patients (55%), and 92% (164

of 179) were normal. Patients with abnormal or inconclusive ABR and patients with

severe SNHL were evaluated with radiologic studies (46 patients). Of the 34 who had

an MRI, 30 were normal and four were abnormal. All 19 CT scans were judged as

normal.

To assess the cost of diagnosis per AN, the study determined the charges for

diagnostic studies. Charges may differ from patient costs. Because audiograms were

used in the inclusion criteria for the study, the charge for audiograms was excluded.

The charges for diagnostic studies were multiplied by the number of studies

performed, and a charge of $166,955 was incurred in identifying 4 patients with AN

and ASNHL. The charge of diagnosis per AN was more than $41,000. The authors

suggest a cost containment protocol for screening AN.

Published audiological screening protocols

Acoustic neuromas produce patterns of audiovestibular symptoms and in particular

ASNHL, which tends to be different between patients with and without an AN. This

difference has been used to develop a number of different decision-support protocols

for clinicians, to assist in risk-stratifying patients, with those at higher risk being

referred for an MRI. A brief description of published audiological screening protocols

for AN is shown in Table 8.

25


Table 8 A description of published decision-support

protocols for acoustic neuroma

Name Clinical criteria Asymmetry of thresholds

Seattle (Mangham 1991) Nil ≥15 dB between the average of 1-8 KHz

Charing cross (Obholzer et al. 2004)

Nil ≥15 dB in any two neighbouring frequencies if the average hearing threshold of the better ear ≤30

dB≥20 dB in any two neighbouring frequencies if the average hearing threshold of the better ear >30 dB

Nashville (Welling et al. 1990) Nil ≥15 dB at any frequency between 0.5 and 4 KHz

Oxford (Sheppard et al. 1996) Unilateral tinnitus, age < 70 years

≥15 dB between the average of 0.5 to 8 KHz

UK Department of Health (2002) Vertigo ≥ 20 dB at any frequency between 0.5 and 4 KHz

Sunderland (Dawes et al. 1998) Unilateral tinnitus or Meniere’s disease symptoms

≥ 20 dB between two neighbouring frequencies

Source: Nouraei et al. (2007), Table 1 page 251.

None of these protocols are universally accepted for screening AN in patients with

ASNHL.

26


27


Summary and Recommendations

Conclusions

This preliminary report presents the evidence for the early detection of AN using MRI

or other comparative diagnostic techniques in patients with ASNHL, albeit without

critical appraisal. It appears there is a significant clinical argument to support the

routine use of MRI. The test has been reported to have high sensitivity and specificity,

higher than that of the ABR test. However, the widespread use of MRI in this patient

population is problematic due to the high cost per diagnosis of AN (attributed to the

high cost of MRI and low incidence rate of AN in ASNHL presenting patients), and

issues surrounding accessibility to MRI equipment. Most papers suggest a protocol or

guidelines be implemented to help select patients for MRI screening. However this

approach accepts that there is a trade-off between cost efficiency, and the risk of

missing some tumours.

Points to consider

As mentioned previously there is a systematic review due for publication by the

NIHR in April 2009 titled:

‘The role of magnetic resonance imaging in the identification of suspected acoustic

neuroma: systematic review of clinical and cost effectiveness, and natural history’

Alternatively a full systematic review could be considered on the use of MRI in

screening patients with ASNHL for the early detection of AN.

28


29


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34


35


Appendix A: HTA websites searched

HTA and systematic review databases to be searched for this project are:

Health Technology Assessment Database (via the Cochrane Library):

http://www3.interscience.wiley.com/cgi-bin/mrwhome/106568753/HOME

INAHTA website database:

http://www.inahta.org/Search2/?pub=1

Note: Can search database and gain access to individual member websites.

Individual HTA groups:

MSAC: http://www.msac.gov.au/

ANZHSN: http://www.horizonscanning.gov.au/

NZHTA: http://nzhta.chmeds.ac.nz/

NICE: http://www.nice.org.uk/

AHRQ/USPSTF: http://www.ahrq.gov/

CADTH: http://www.cadth.ca/

http://www3.interscience.wiley.com/cgi-bin/mrwhome/106568753/HOME

http://www.cadth.ca/

36


37


Appendix B: Excluded studies annotated by reason for exclusion

Farrell III JT. (1983) Radiographic

evaluation of acoustic neuromas:

Comparison of high-resolution

computed tomography and

polytomography. Journal of the

American Osteopathic Association

83:61-66.

Reason for exclusion: Incorrect study

type

Adelman S. (1983) Identification of

acoustic neuroma in noise-exposed

workers. Scandinavian Audiology

12:247-250.


type

Flood LM and Brightwell AP. (1984)

Cochlear deafness in the presentation

of a large acoustic neuroma. Journal of

Laryngology and Otology 98:87-92.


type

Terry RM. (1985) An unusual

presentation of acoustic neuroma.

Journal of Laryngology and Otology

99:593-595.


type

David M and Trehub SE. (1989)

Perspectives on deafened adults.

American Annals of the Deaf 134:200-

204.


type

(1990) Docs' Discussion at OMG.

American Journal of Otology 11:141-

143.


type

Farrell ML, Harries MLL, Baguley

DM, and Moffat DA. (1991) Bilateral

acoustic schwannoma: Post-operative

hearing in the contralateral ear.


105:769-771.


type

Moon HH, Jabour BA, Andrews JC,

Canalis RF, Chen FH, Anzai Y, Becker

DP, Lufkin RB, and Hanafee WN.

(1991) Nonneoplastic enhancing

lesions mimicking intracanalicular

acoustic neuroma on gadolinium-

enhanced MR images. Radiology

179:795-796.


type

House H, Sheehy J, De la Cruz A,

House J, Nelson R, Luxford W,

Shelton C, and Linthicum J. (1991)

Docs' discussion at HEC. American

Journal of Otology 12:147-149.


type

Vellutini EAS, Cruz OLM, Velasco

OP, Miniti A, and Almeida GM.

(1991) Reversible hearing loss from

cerebellopontine angle tumors.

Neurosurgery 28:310-313.


type

Berenholz LP, Eriksen C, and Hirsh

FA. (1992) Recovery from repeated

sudden hearing loss with corticosteroid

use in the presence of an acoustic

neuroma. Annals of Otology,

Rhinology and Laryngology 101:827-

831.


type

Quester R, Menzel J, and Thumfart W.

(1993) Radical removal of a large

38


glossopharyngeal neurinoma with

preservation of cranial nerve functions.

Ear, Nose and Throat Journal 72:600-

611.


type

Ghobashy A and Van Loveren H.

(1993) Acoustic schwannoma

presenting as acute posterior fossa

hematoma: Case report and review of

the literature. Skull Base Surgery

3:136-140.


type

Kingdom TT, Lalwani AK, Pitts LH,

Chandler WF, and Salcman M. (1993)

Isolated metastatic melanoma of the

cerebellopontine angle: Case report.



type

Van Leeuwen JPPM, Cremers CWRJ,

Thijssen HOM, and Meyer HE. (1993)

Unchanged unilateral hearing loss and

ipsilateral growth of an acoustic

neuroma from 1 to 4 cm. Journal of

Laryngology and Otology 107:230-

232.


type

Shelton C. (1993) Doc's Discussion at

HEC. American Journal of Otology

14:199-202.


type

O'Donoghue GM. (1993) Acoustic

neuroma: triumph and disaster. British

Journal of Hospital Medicine 49:85-

87.


type

Levine RA, Bu-Saba N, and Brown

MC. (1993) Laser-Doppler

measurements and

electrocochleography during ischemia

of the guinea pig cochlea: Implications

for hearing preservation in acoustic

neuroma surgery. Annals of Otology,


136.


type

Kawaguchi T, Tanaka R, Kameyama

S, and Yamazaki H. (1994) Full

recovery from deafness after removal

of a large acoustic neurinoma

associated with neurofibromatosis 2:

Case report. Surgical Neurology

42:326-329.


type

Downie AC, Howlett DC, Koefman

RJ, Banerjee AK, and Tonge KA.

(1994) Case report: prolonged contrast

enhancement of the inner ear on

magnetic resonance imaging in

Ramsay Hunt syndrome. British



type

Linstrom CJ, Krajewski MJ, Shapiro

AL, and Caruana S. (1994) Outer table

graft in middle fossa surgery.

Otolaryngology - Head and Neck

Surgery 111:70-75.


type

Sakakibara A, Aoyagi M, and Koike

Y. (1994) Acoustic neuroma presented

as repeated hearing loss. Acta Oto-

Laryngologica, Supplement 511:77-80.


type

Donnelly MJ, Daly CA, and Briggs

RJS. (1994) MR imaging features of an

intracochlear acoustic schwannoma.


108:1111-1114.

39



type

Sells JP and Hurley RM. (1994)

Acoustic neuroma in an adolescent

without neurofibromatosis: case study.

Journal of the American Academy of

Audiology 5:349-354.


type

Schneider ML, Walker GB, and

Dormer KJ. (1995) Effects of magnetic

resonance imaging on implantable

permanent magnets. American Journal

of Otology 16:687-689.


type

Wall MP and Block R. (1995) Annual

meeting of the American

Laryngological, Rhinological, and

Otological Society. Archives of


Surgery 121:1065-1066.


type

Saeed SR, Woolford TJ, Ramsden RT,

and Lye RH. (1995) Magnetic

resonance imaging: A cost-effective

first line investigation in the detection

of vestibular schwannomas. British

Journal of Neurosurgery 9:497-503.


type

Minor LB. (1995) Neuro-otology:

Hearing. Current Opinion in

Neurology 8:89-94.


type

Peh WC and Yuen AP. (1995) Clinics

in diagnostic imaging. Singapore

medical journal 36:433-436.


type

Judkins RF and Rubin AM. (1995)

Sudden hearing loss and unstable

angina pectoris. Ear, Nose and Throat

Journal 74:96-99.


type

Gaffney RJ and McShane DP. (1996)

Bilateral acoustic neurofibromatosis

camouflaged by corticosteroid

treatment of sudden sensorineural

hearing loss. Leukemia 10:151-152.


type

Nishizawa S, Yokoyama T, Hinokuma

K, and Uemura K. (1997) Unilateral

sensori-neural hearing disturbance

caused by intramedullary cerebellar

tumors. Neurologia Medico-

Chirurgica 37:701-707.


type

Ishikawa K, Yasui N, Monoh K, Tada

H, Mineura K, Sasajima H, and

Togawa K. (1997) Unilateral acoustic

neuroma in childhood. Auris Nasus

Larynx 24:99-104.


type

Fitzgerald DC, Mark AS, and Shelton

C. (1999) Cost-effective screening for

acoustic neuroma [1] (multiple letters).


Surgery 121:846.


type

Shamboul KM and Grundfast K.

(1999) Hearing loss in

neurofibromatosis type 1: Report of

two cases. East African Medical

Journal 76:117-119.


type

Selesnick SH, Deora M, Drotman MB,

and Heier LA. (1999) Incidental

discovery of acoustic neuromas.

40



Surgery 120:815-818.


type

Tripathy LN, Forster DMC, and

Timperley WR. (1999) Adult primitive

neuroectodermal tumour. A case report

and review of the literature. British



type

Michaels L, Lee K, Manuja SL, and

Soucek SO. (1999) Family with low-

grade neuroendocrine carcinoma of

salivary glands, severe sensorineural

hearing loss, and enamel hypoplasia.

American Journal of Medical Genetics

83:183-186.


type

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A rapid scan of the literature · 2010-01-04 · A rapid scan of the literature 26 March 2009...

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Transcript of A rapid scan of the literature · 2010-01-04 · A rapid scan of the literature 26 March 2009...