Pseudo-conductive Hearing Pseudo-conductive Hearing LossesLosses

Bastaninejad, ShahinBastaninejad, Shahin, , MD, Assistant MD, Assistant Professor of ORL, TUMS, Amir’Alam Professor of ORL, TUMS, Amir’Alam

HospitalHospital

Definition

Apparent conductive hearing loss on

audiometric testing, that is notnot due to

pathology in the external or middle ear

of Pseudo-conductive Hearing Lossof Pseudo-conductive Hearing Loss

Case Presentation

• 10yr old boy

• CHL in Left ear, found during a routine school-hearing test

• Left side Rinne’s test was negative

• AR in Left ear: Ipsi.neg., Contra.Pos.

• CTnl.

• No history of trauma and…

Hamad Al Muhaimeed, et al. Conductive hearing loss: investigation of possible inner ear origin in three cases studies. The Journal of Laryngology & Otology November 2002, Vol. 116, pp. 942–945

Case Cont.

• The provisional diagnosis was ossicular

disruption medial to the neck of the stapes (to

explain the presence of the contralateral stapedial

reflex)�

• Exploration performed all ossiceles were

mobile, FP was mobile, but Round window

reflex was negative

Importance

Some causes of these pseudo-conductive

hearing losses can be diagnosed without

resorting to surgery

Bibliography

• The concept of inner ear conductive

hearing loss was proposed as early as the

1960s1960s by Gloris and Davis and by Nixon

and Glorig. They proposed stiffness of the

cochlear partition as a possible cause

Proposed Mechanisms for a True Pseudo-CHL

• Third window effect

• lesions in the:– Scala vestibuli– Helicotrema – Scala tympani– Basilar membrane

• Obliterated round window membrane

Transmission ProblemTransmission Problem

Inner ear conductive hearing lossInner ear conductive hearing loss

Normal Cochlear TransmissionsNormal Cochlear Transmissions

key discriminating features

• Presence of AR in the ear with CHL

– Exception: crossedcrossed or may be a normal

stapedial reflexes can be present if there is

fracture in the stapes crura or footplate medial medial

toto the insertion of the stapedius tendon

key discriminating features

• Round window reflex findings:

– Presence When Otosclerosis is suspected

– Absence In the presence of an obviously

mobile footplate

Other differentiating features

Sup.SCC Dehiscence - AudiogramSup.SCC Dehiscence - Audiogram

Differential Diagnosis

• Poor Masking Poor Masking and Poor AudiometryPoor Audiometry:

– Perhaps the most common cause of

pseudoconductive hearing loss is the presence of

a unilateral or asymmetric sensorineural hearing

loss in which the better hearing inner ear is poorly

masked perform tuning fork test in all subjects

– Collapsing ear canals

DDx Cont.

• Functional Hearing Loss:Functional Hearing Loss:

– Must be considered in any patient with an unusual

conductive hearing loss pattern:

• Some subjects who are exaggerating their hearing loss

have difficulty estimating the loudness level of the two

different stimuli different CHL in two consecutive

assessments…

• Also they may have an inverse air–bone gap!

DDx Cont.

• Third Window Third Window can arise from a fistula into the cochlea or the labyrinthine portion of the inner ear– Semicircular Canal Dehiscencies (Superior, Inferior

and Lateral)– LVA– X-Linked Deafness With Stapes Gusher– Dehiscence Between the Cochlea and Carotid Canal– Paget Disease of the Temporal Bone– Some inner Ear Malformations

Saumil N. Merchant and John J. Rosowski. Conductive Hearing Loss Caused by Third-Window Lesions of the Inner Ear. Otol Neurotol. 2008 April ; 29(3): 282–289

DDx Cont.

• Round Window Obliteration

• Inner Ear Mechanical Conductive Loss– One of the types of presbycusis (CHL with

Mixed loss at 4k and 8k)– Changes in BM pliability– Lesions in the scala vestibuli, helicotrema and

scala tympani– Co-existed with some forms of the congenital

hearing losses

DDx Cont.• Missed Middle Ear PathologyMissed Middle Ear Pathology

– Otosclerosis with a flexible suprastructure– Malleus or incus fixation or stiffness– Pathology at the lenticular process of the

incus– Floppy tympanic membrane– Adhesions lysed during the approach for

exploration– Transient pathology at the time of audiogram

Conclusion

Think about plausibility of Pseudo-

conductive hearing loss and include it’s

possibility in your pre-operative evaluation pre-operative evaluation

and patient consentpatient consent before proceeding to

the middle ear exploration