Visual Neglect

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MAJOR REVIEW

Visual Neglect Following Stroke: Current Conceptsand Future Focus

Darren S.J. Ting, MBChB,1 Alex Pollock, PhD,2 Gordon N. Dutton, MD, FRCOphth,3,4,5

Fergus N. Doubal, MRCP,6 Daniel S.W. Ting, MBBS,7 Michelle Thompson, BSc (Hons),6

and Baljean Dhillon, FRCPS, FRCS, FRCOphth8

1Victoria Infirmary, Glasgow, UK; 2 Nursing, Midwifery, and Allied Health Professionals (NMAHP) Research Unit,Glasgow Caledonian University, Glasgow, UK; 3 Tennent Institute of Ophthalmology, Gartnavel General Hospital,Glasgow, UK; 4 Royal Hospital for Sick Children, Glasgow, UK; 5 Department of Vision Sciences, Glasgow Caledonian University, Glasgow, UK; 6 Western General Hospital, Edinburgh, UK; 7 Royal Perth Hospital, Western Australia, Australia; and 8 Princess Alexandra Eye Pavilion, Edinburgh, UK

Abstract. Visual neglect is a common, yet frequently overlooked, neurological disorder followingstroke characterized by a deficit in attention and appreciation of stimuli on the contralesional side of the body. It has a profound functional impact on affected individuals. A assessment and management of this condition are hindered, however, by the lack of professional awareness and clinical guidelines.

Recent evidence suggests that the underlying deficit in visual attention is due to a disruptedinternalized representation of the outer world rather than a disorder of sensory inputs. Dysfunction of the cortical domains and white-matter tracts, as well as inter-hemispheric imbalance, have beenimplicated in the various manifestations of visual neglect. Optimal diagnosis requires careful history-taking from the patient, family, and friends, in addition to clinical assessment with the line bisectiontest, the star cancellation test, and the Catherine Bergego Scale. Early recognition and prompt rehabilitation employing a multidisciplinary approach is desirable. Although no treatment has beendefinitively shown to be of benefit, those with promise include prism adaptation, visual scanningtherapy, and virtual reality--based techniques. Further high quality research to seek optimum short-and long-term rehabilitative strategies for visual neglect is required. (Surv Ophthalmol 56:114--134,2011. 2011 Elsevier Inc. All rights reserved.)

Key words. assessment dorsal stream neglect rehabilitation spatial representationstroke unilateral neglect ventral stream visual neglect

I. Introduction

Visual neglect (VN) is a neurological disordercharacterized by a deficit in attention to stimulion one side of the body, almost invariably contra-lateral to the side of the cerebral lesion.95 Theterm has been used loosely and interchangeably

with hemispatial neglect, unilateral neglect, and visual inattention. Its adverse impact on day-to-day

functioning and stroke rehabilitation outcome is well established.

Stroke, whether ischemic or hemorrhagic, is a de-bilitating and disabling condition that can impaircognition, visuospatial, language, and motor func-tion.36 Motor rehabilitation following stroke is wellrecognized, but rehabilitation for visual neglect,a common and dramatic consequence of stroke,105

114 2011 by Elsevier Inc.

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has received limited attention, as it can be difficult toidentify, and there is currently no consensus con-cerning optimal assessment and treatment of thiscondition.

II. Epidemiology A US study 141 of 1,281 stroke patients reported

a prevalence rate of VN of 43% and 20% followingright and left hemispheric stroke, respectively. Thisasymmetry in prevalence of VN is consistent withother literature4,13,21 and probably occurs becausethe right hemisphere tends to allocate attention toboth hemispaces, but the left hemisphere accordsattention more selectively to right hemispace.66,116

Also, VN patients with right hemispheric strokegenerally have a worse prognosis than those with left hemispheric stroke.13,46,131

Despite the high prevalence rate, 61% of patients with VN w ere overlooked during hospital admissionin the US,40 and only 13% of stroke patients wereassessed with standardized neglect assessments ina Canadian study.114 This low detection rate couldbe explained by insufficient awareness of thiscondition or may reflect inherent difficulties indiagnosing neglect in the presence of other moreacute and readily recognizable features of stroke likedysphagia, dysphasia, hemianopia, or hemiplegia.In the UK, the documented prev alence rates of

VN post-stroke vary between 8%164 and 82%162 asa result of heterogeneous patient cohorts, inconsis-tent definition, non-standardized assessment methods, and different timings of the assessment.

Increased age has also been shown to beassociated with a higher incidence and severity of

VN.57,141 This could be attributed to prior cerebralatrophy or a physiologically dampened reactiontime in the elderly population during visual search-ing activities, especiall y when intensive visual atten-tion is required.57,102 Other demographic factorslike sex111,141 and handedness141 have no significant influence on the occurrence of VN.

III. Varieties of Neglect

A wide range of neglect variants have beendescribed as a consequence of the discrepant classifications adopted. Conceptually, it can beconsidered under the following headings.169

A. MODALITY (INPUT/OUTPUT)

Neglect can be divided into sensory (input) andpremotor (output) neglect. Sensory neglect ischaracterized by unawareness of sensory stimuli of

different modalities—including tactile/somatosen-

sory, auditory, and visual or visuospatial in contrale-sional hemispace. Premotor neglect is described asfailure to orientate the limbs towards contralesionalhemispace despite awareness of the stimulus. VNhas been primarily considered part of the spectrumof sensory neglect; recent studies, however, suggest that the underlying deficit primarily is a disruptedinternal computation of the spatial representationof the external world rather than a true sensory deficit (see section V. Pathophysiology in thisreview) This has important implications in for-mulating optimal assessment and rehabilitationstrategies.

B. SPATIAL REPRESENTATION

Spatial representation, which depends on theframe of reference, has also been used to distinguishbetween different neglect subtypes, namely, egocen-

tric (viewer-centered) VN and allocentric (stimulusor object-centered) VN. Egocentric VN is described asfailure to orientate or attend to the stimuli on thecontralesional hemispace with respect to the mid-sagittal plane of the body, head and eye. In contrast,allocentric VN refers to the inability to attend to theone side of the stimulus irrespective of the relativeposition of the stimulus with respect to the viewer.

Egocentric VN has a higher reported incidencethan allocentric VN as a sequel to a cerebrovascularevent. As a result, the terms ‘‘visual neglect’’ or‘‘unilateral neglect’’ primarily refer clinically toegocentric VN; however, these neglect subty pes exist as separate entities with distinct neural bases58,109,113

(see section V.E Clinico-anatomical correlations of visual neglect, herein). VN is a heterogeneousdisorder that involves various neurocognitive re-gions, and broader consideration needs to be takenfor each neglect subtype.

C. RANGE OF SPACE

According to the classification by ‘‘range of space’’, VN can be divided into personal, periperso-nal, and extrapersonal neglect. This classification

has been widely adopted as part of VN assessment of the functional performance in clinical practice.

IV. Functional Impact

VN results in a range of functional impairments, with severe neglect being associated with a poorprognosis.79,163 Those with left VN fail to attend totheir left side, with features ranging from thoseaffecting personal, through peripersonal, to extrap-ersonal space (Table 1). Each subtype of neglect may either manifest as a separate entity or be

associated with other subtypes. For instance, a

VISUAL NEGLECT FOLLOWING STROKE 115



patient affected by peripersonal neglect does not necessarily also manifest extrapersonal neglect.59,173

It is important, however, to recognize that thisclassification concerns the external observers’ in-terpretation rather than the nature of the distur-bance of the internalized, virtual representation of

the external world that characterizes human vision/ visuospatial perception. Also, VN may be associated with other forms of neglect, including tactile,auditory, and motor neglect.

V. Pathophysiology

VN is a multifaceted disorder. The anatomical,physiological, and conceptual models of cortical

visual processing have always been highly conten-tious scientific issues. As mentioned, VN can beconceptually divided into several categories accord-

ing to the modality (input/output), the spatialrepresentation, and the range of space. Although various mechanisms and models have been pro-posed and examined, none has fully and successfully captured the entire spectrum of this heterogeneousdisorder. We attempt a systematic overview of pathophysiology and clinico-anatomical correlationsof VN from different perspectives.

A. PHYSIOLOGY OF VISUOSPATIAL PERCEPTION

It is becoming increasingly apparent that ourbrain operates and processes visual information via

two distinct, but complementary, higher neuralprocessing pathways, namely, the dorsal streamand ventral stream (as proposed by Milner andGoodale).56,119,120 They suggested that the dorsalstream, which connects the visual cortex with thesuperior parietal lobe and the intraparietal sulcus,subconsciously assimilates incoming visual informa-tion in order to bring about immediate ‘‘on-line’’,

visually guided movements through the virtualimages in the mind, which constitute an internaland subconscious egocentric spatial representationof the multidimensional external world. By contrast,

the ventral stream, which bridges the visual cortex

and the inferior temporal lobe, is accountable forour conscious, object-based visual perception andrecognition. Dysfunction of dorsal stream results inoptic ataxia (impaired visual guidance of move-ment), and dysfunction of ventral stream causes

visual agnosia (impaired recognition of visual

stimuli), respectively. Although this model providesa comprehensive explanation for various compo-nents of visuospatial perception and visuomotorfunction, the manifestation of VN, which normally follows the damage of inferior parietal lobe, has yet to be fully considered in the context of this dorsal--

ventral dichotomy.156 Also, the double dissociationbetween VN and optic ataxia or visual agnosia hassuggested separate underlying disorders of theneural substrates.73,133

Instead of the occipito-parietal and occipito-temporal pathways, the dorsal--ventral dichotom y

variant proposed by Corbetta and Shulman32

focused on the attentional basis of the frontopar-ietal networks, namely, the dorsal and ventralfrontoparietal pathways. The bilateral ‘‘dorsal’’pathways, which connect the superior parietal lobesand the intraparietal sulci with the dorsal frontallobes, including the frontal eye fields, are involvedin goal-directed, top--down attentional selection.32

This top--down attention facilitates visuospatialexploration in the context of prior knowledge of

what to search for or what the task is.33 In contrast,the right lateralized ‘‘ventral’’ pathway, which links

the temporal parietal junction (TPJ), inferiorparietal lobe (IPL), and ventral frontal lobe, isassociated with stimulus-driven, bottom--up atten-tional selection.32 This bottom--up attention simply refers to the ability to capture an event occurring inthe surrounding world—salience detection.33 In

view of the overlap between the neural basis of VNand their proposed ‘‘ventral’’ network, Corbetta andShulman infer that V N is associated with a bottom--up attentional deficit.32 Also, their proposed right lateralized ventral pathway helps explain the higherincidence of VN following right posterior parietal

damage.

TABLE 1

Definitions and Examples of Personal, Peripersonal, and Extrapersonal Neglect

Personal space—the space occupied by one’s body combing, grooming, shaving, recognizing the right half of the body only 17,90 and anosagnosia (a feature in which

the patient is unable to recognize his or her own deficit)14,18

Peripersonal space—the space surrounding one’s body, within arm’s reach eating food from therighthalfoftheplateandneglectingthefoodontheleft,readingtherighthalfofthetwopagesof

an open book28

Extrapersonal space—the space surrounding one’s body, beyond arm’s reach failing to identify meaningful stimuli and people on the left, colliding into objects on the left while mobilizing or

using a wheelchair138

116 Surv Ophthalmol 56 (2) March--April 2011 TING ET AL



In addition, consistent activation of both frontaland parietal regions, as evident from imagingstudies,52,134,157 during tasks requiring spatial atten-tion and visuomotor function have supported theneural basis of this fronto-parietal model. Nonethe-less, there is emerging evidence showing that patients with VN may exhibit deficits of bothattentional components, including sustaining atten-tion (goal-direct ed)24,74 and salience detection(stimulus-driven),23,33 which suggests that a combi-nation of both of the described conceptual frame-

works is required to explain this complex disorder.

B. SPATIALLY LATERALIZED DYSFUNCTION OF

VISUAL NEGLECT

According to the original definition, VN isa disorder characterized by the failure of orientatingor attending towards the stimuli on one side of the

hemispace; it is a form of spatially lateralizeddysfunction. For instance, patients with ‘‘egocentric’’

VN can exhibit complete inattention (perceptual/input neglect) or impaired visuospatial exploration(premotor/output neglect) confined to contrale-sional hemispace, with normal visuospatial percep-tion within ipsilesional hemispace. This spatially lateralized dysfunction of VN has been well demon-strated by both clinical observation and the VNassessment tools (see subsequent discussion).

Heilman et al66 hypothesized that the right posterior parietal cortex, which is highly specialized

for spatial attention, allocates attention to bothhemispaces, whereas the left posterior parietal cortexallocates attention, more selectively, to the right hemispace. This explains why VN is more commonly reported following right rather than left hemisphericdamage.13,21,141 This is also why the affected in-dividual exhibits deficits on the contralesional side as

well as the ipsilesional side, to a milder extent,12,149

when the right hemisphere is affected. Moreover, thecommon paradoxical observation of contralesionallimb apraxia (inability to activate limb) following left IPL damage, but the development of VN following

right IPL damage, underlines the organizational andfunctional asymmetry between both IPLs, at least inthe context of spatial attention.54

On the other hand, Kinsbourne96 suggested that allocation of spatial attention towards both hemi-spaces is balanced by the reciprocal inhibition fromeach hemisphere, with left hemisphere allocatingattention towards the right hemispace and vice

versa. Therefore, when there is a right hemisphericdamage, the unopposed left hemisphere becomesrelatively hyper-attentive towards the right hemi-space, subsequently leading to left VN. This model is

further reinforced by Koch et al

100

that describes

relative electroencephalographic hyperexcitability in the left posterior parietal cortex (PPC) of theneglect patients with right hemispheric stroke,resulting in rightward attention bias (or left visualneglect). Improvement of VN was observed in 7 of 10 patients following the application of repetitivetranscranial magnetic stimulation (r-TMS) over t heunaffected PPC. In a similar vein, Oliver et al128

reported beneficial effect in patients with VNfollowing the application of r-TMS on the un-affected PPC. An explanatory mechanism is that r-TMS disrupts the integrated neural activity of theintact side, dampening the attention to the ipsile-sional side, and thereby restoring the orientationbalance between both hemispheres.

C. NON-SPATIALLY LATERALIZED DYSFUNCTION

OF VISUAL NEGLECT

Until recently, VN was thought strictly to beattributable to lateralized disruption of the spatialattention on one side of the visual space; however,there is emerging evidence proposing that VN is not necessarily confined to one hemispace. It cancomprise both spatially lat eralized and non--spatially lateralized dysfunctions.74 In other words, patients

with VN may completely neglect the contralesionalhemispace (spatially lateralized) while demonstrat-ing global inattention to stimuli regardless of thelocation of the target (non-spatially lateralized).

Both the IPL and the ventral frontal region—

which, when damaged, are frequently associated with VN—have been shown to exhibit functionsrelated to non-spatial attention including sustainedattention and salience detection.74 Similarly, VNpatients, with damage to the IPL, may demonstratethese non-spatial attentional deficits. This can beassessed b y techniques including the oddball para-digm,31,38 which requires the patient to detect target stimuli interspersed with non-target stimuli at thesame area, and attentional blink paradigm,75 a mea-sure that assesses the ability of salience detectionand perception of each stimulus among a series of

rapidly changing stimuli at one spatial location. A delayed ‘‘attentional-blink’’ response is suggestive of an attentional deficit. Although non-spatial inatten-tion may be doubly dissociable from VN,150 thepresence of a non-spatial attentional deficit aggra-

vates the severity of VN.75

These intriguing findings enhance understandingof the pathophysiology of VN and, more impor-tantly, facilitate the development of potentially moreeffective therapies including sustained attentionmeasures and pharmacological intervention di-rected t ow ards improving general non-spatial

attention.

107




D. ROLE OF NON-VISUAL AFFERENT INPUTS

In addition to visual afferent input, egocentricmultidimensional internalized spatial mapping re-quires multiple afferent inputs from non-visualreceptors, including neck muscle19 and extra-ocular muscle proprioceptors,75 and the tactile

and the vestibular systems.125,127

This afferent pro-prioceptive feedback maintains the required stabil-ity and perception of the location of the visualimages by maintaining correct egocentric localiza-tion of the body despite head and eye movement.There is evidence that patients w ho have alteredextraocular muscle proprioception175—either fromsurger y,25,161 forced ductions with a suction contact lens,48 or dysfunction of the trigeminal nerve26,171—demonstrate errors in spatial localization and

visually guided movement.Karnath87 demonstrated the role of neck muscle

proprioception in maintaining egocentric spatiallocalization. He observed that the ipsilesional deviation of neglect patients when looking straight ahead can be ameliorated by the applicationof vibration to the contralesional neck,87,152 modi-fying the afferent input from the neck muscleproprioceptors.

In addition, the role of the vestibular system inbody orientation and egocentric spatial localizationhas long been recognized. The vestibular input contributes to spatial orientation mainly via the

vestibulo-ocular reflex, which involves the trans-mission of afferent inputs from the vestibular nucleito the ocular motor nuclei and higher corticalcenters via the medial longitudinal fasciculus.125,127

Following integration of the afferent inputs in thehigher cortical centers, efferent outputs are trans-mitted along vestibulospinal projections for head,eye, and body orientation—the internal ‘‘plumbline,’’ which accords balance and our knowledge of the vertical, and hence, spatial localization.125,127

This concept has been further reinforced by the useof vestibular caloric stimulation (irrigation of theear canal with either warm water ipsilaterally or cold

water contralaterally), which transiently reduces the

orientation bias in VN and can rest ore the egocen-tric spatial reference frame.88,147 Longer terminterventions, designed to ‘‘deceive’’ the sensory input of the visuospatial perception rather thanaddressing the underlying lack of awareness, re-mains elusive.

E. CLINICO-ANATOMICAL CORRELATIONS OF

VISUAL NEGLECT

Several factors challenge clinicians and researchersinvestigating the neural basis of VN. First, patients

with VN often manifest extensive brain damage, which

hinders precise anatomical correlation. Second, pureassessment of VN is problematic in the stroke patient

who has co-existing cognitive impairment, causingdifficulty in recruiting ‘‘ideal’’ VN patients for furtherinvestigation.Also, the lackof detailed classificationof the different neglect subtypes can lead to over-generalization of the neural basis of VN. For example,thedistinction betweenegocentricVN andallocentric

VN, which can occur independently,58,109 has not been made in many studies.

Various cortical regions serving visuospatial atten-tion have been identified by high quality functionalbrain imaging like functional magnetic resonanceimaging and positron emission tomography. Theseregions comprise, in particular, the inferior parietallobe and the TPJ,64,70,123,170 the superior temporalgyrus,85 and the frontal lobe, including the medialand inferior frontal gyri.75,76 In contrast, the pre-

viously controversial role of the subcortical regions

implicated in VN has been refuted by recent studies,suggesting that, instead of the subcortical infarctionitself, VN is associated with hypoperfusion of theoverlying cortex and that subcortical infarctionalone does not result in VN.70

The neuroanatomical findings can be influencedby the timing of assessment. For instance, Mort et al,123 who investigated the neural basis of VN duringthe chronic phase (63 days post-stroke), havereported that VN is most strongly associated withangular gyrus (part of the inferior parietal lobe)infarction. In contrast, Karnath et al84 examined

their patients at 8 days post-stroke and had observedthe superior temporal gyrus is the most commonimplicated region in VN.

Moreover, the development of diffusion tensorimaging, which provides the facility to track white-matter tracts, has led to a quantum leap in theunderstanding of the neuro-anatomical correlationof VN. Various white-matter tracts have beenident ified, particularly in the fronto-parietal net-

work,11,15,37 and their dysfunction can lead to the‘‘disconnection syndrome’’ underlying VN.11,37 Thisobservation is in accordance with the anatomical

and theoretical model proposed by Corbetta andShulman,32 who focused on the attentional basis of the fronto-parietal network. This suggests that spatial attention operates in a multi-level networkthat requires intact neurocognitive cortical regionsand the underlying connections between them.Interestingly, VN results from both anterior andposterior circulation strokes, depending on theaffected corresponding white-matter tracts.15,37

In addition, VN has been classified according tothe site of neuroanatomical damage, which chiefly comprises three areas: the parietal lobes, the frontal

eye fields, and the cingulate regions.

117

Each of the




neuro-anatomical neglect subtypes exhibits somedegree of site-specific variation (Table 2). Althoughthis classification provides useful insights into thecomplex neuroanatomical correlation of VN, it doesnot include the underlying complex disorders of function. Also, the differentiation of these subtypescan be difficult in clinical practice.

As discussed earlier, spatial representation takesinto account different frames of reference, primarily

viewer-centered (egocent ric) and stimulus-centered(allocentric). Hillis et al70 examined the neural basisof VN subtypes and observed distinct physiology andneural correlates underlying both subtypes with theaid of high quality functional brain imaging. They have reported that egocentric VN primarily followsdamage to the inferior parietal lobe69,70 and, to someextent, the posterior inferior frontal gyrus,70 whichare implicated in the ventral frontoparietal networkproposed by Corbetta and Shulman.32 Similar asso-ciation betweenegocentric VN and dysfunction of thesupramarginal gyrus (part of the inferior parietal

lobe) has been observed by Medina et al.113

On theother hand, allocentric VN is more commonly observed following injuries to the temporal regions,including the superior temporal gyrus,70 the ventro-medial temporal area,58 and the posterior inferiortemporal gyrus.113 This is consistent with Milnerand Goodale’s proposal that the temporal or

ventral pathway is highly accountable for object-based perception and recognition; therefore, dys-function of this pathway leads to allocentric VN. Thefunctional differences and the interactions among

various intra-temporal regions have yet to be further

investigated.

Although the neural correlates of left VN have been well studied, right VN following left hemisphericst roke has received limited attention. Kleinman et al98 focused on the neural correlates of VN subtypesfollowing left, instead of right, hemispheric strokeand reported a higher proportion of allocentric VNthan egocentric VN, which contrasts with the findingsof Hillis et al.70 These findings, once again, suggest that both hemispheres are organized and function in

distinct ways in the context of spatial attention.In view of the heterogeneity of VN, we emphasize

that all studies should be interpreted with cautionbecause they are influenced by the type of VNincluded in the study, the assessment methods used,and the timing and type of brain imaging instituted.

F. CLINICAL SYNDROMES ASSOCIATED WITH

VISUAL NEGLECT

VN has been found to be associated with othercomplex parietal lobe syndromes that affect visuo-

spatial comprehension and attention, such asGerstmann and Balint syndromes. Gerstmann syn-drome results from a focal lesion affecting theangular and supramarginal gyri near the TPJ,usually on the left, and is characterized by inability to perceive an object properly (agnosia), dy sgra-phia, dyscalculia, and left--right disorientation.132

Balint syndrome, first reported in the early 20thcentury,9 is an uncommon disorder that classically results frombilateralposteriorparietal pathology andcomprises a constellation of symptoms: unilateral

visuospatial inattention (left hemineglect), deficits in

visually guided movement despite normal limb

TABLE 2

Summary of Neuroanatomical Classification and the Functional Consequences of VN

Type Function of Each Area Presentation

Parietal neglect The posterior parietal lobes integrate afferent stimuli of any modality including visualstimuli, transforming external space into an

internalized representation

Loss of subconscious synthesis of theinternalized representational space,resulting in unawareness of the visual

stimuli in contralesional hemispace, evenone’s own body (a form of anosagnosia)

Frontal neglect The frontal eye fields interact with theparietal lobes in selecting salient information and filtering irrelevant information, thus planning meaningful visually guided movement

Failure of limb orientation towardscontralesional hemispace in the absence of hemiparesis, even when using theunaffected limb on the ipsilesional side, which suggests the abnormality lies inmotor output instead of sensory input;34,65

this is probably secondary to a defect in theinternalized representation of motor programming towards the contralesionalside

Cingulate neglect Provides limbic integration, responsible forallocating directed attention according tomotivation130

Spends a disproportionately long periodattending to the greater motivational event,omitting the others which have less impact

Data from Mesulam et al.117




strength (optic ataxia), and the inability to shift gaze voluntarily to objects of interest despite normal eyemovements (ocular apraxia).9,63 The spatial disorderof attention emphasized by Balint was furtherregarded as ‘‘disturbance of visual orient ation’’ by Holmes71 and simultanagnosia by Wolpert.177 Basedon his observation of six soldiers with bilateralparietal-occipital lobe injury particularly affectingthe angular gyri, Holmes concluded that damage tothe angular gyri can lead to w hat he called a ‘‘distur-bance of visual orientation’’71 and results in difficul-ties in precise determination of the multidimensionalposition of an object or relative positions of objects(optic ataxia) and in learning the new surroundingsand in transferring attention from one object toanother (ocular apraxia). On the other hand, theterm ‘‘simultanagnosia’’, coined by Wolpert,177 refersto the inability to perceive and integrate all thecomponents of a visual scene. Each element of Balint

syndrome—left hemineglect, optic ataxia, and ocularapraxia—may manifest independently.34

Refer to Rizzo and Vecera’s142 study for furtherelaboration.

VI. Assessment of Visual Neglect

A. CURRENT CLINICAL GUIDELINES

Recommendations concerning the specific assess-ment methods of VN remain limited. US39 andUK 77,154 guidelines consistently recommend that

visuo-perceptual function, including the potentialfor VN, should be assessed in patients in stroke unitsemploying a multidisciplinary approach. Mini-Mental State Examination and Addenbrooke’sCognitive Examination (2005) are the two most

well-recognized general cognitive assessment batter-ies in current clinical practice in the UK.47,121 Thelimitation of both tests is that VN is only assessed by drawing and copying objects (Table 3).

No specific assessment tool is recommended inthe US. On the other hand, the UK guidelines77

recommend the use of Behavioral Inattention Test

whereas the Canadian

27

guidelines recommend theuse of specific assessment tools for VN, comprisingthe Comb and Razor Test, the Line Bisection Test (LBT), and the Behavioral Inattention Test with thealternatives of the Rivermead, Ontario Society of Occupational Therapy Perceptual Evaluation andthe Motor Free Visual Perceptual Test.

B. HOW IS VISUAL NEGLECT ASSESSED?

The results of an extensive literature searchconcerning the assessment of VN and the underlyingrationale, assessment profiles, with strengths and

weaknesses of the more common tests of VN are

summarized in Table 3. The assessment methodscomprise four main groups: pencil-and-paper tests,behavioral assessment, clinical observation, and morerecent techniques.

1. Pencil-and-paper Tests

VN can be sought by the cancellation test, theLBT, and the copying and drawing test.144

The cancellation task (Fig. 1) requires the patient to delete multiple identical visual target symbols ona paper sheet. Incomplete or disproportionate de-letion on one side indicates VN. There is robust evidence showing that this type of test, particularly interspersed withdistracters,hasthebest sensitivity of the pencil-and-paper tests.60,61,97,110 Common vari-ants include the star cancellation test, the lettercancellation test, and the bell cancellation test.Moreover, structured observation of cancellation test

performance, taking into account the location of theinitial commencing point 2 (deemed to be the most sensitive measure) along with the scanning pattern,the search time, and the number of re-cancellationsof the same target,55,108,167 provide useful qualitativeinformation in addition to quantitative scores.

The LBT (Fig. 1) requires the patient to estimateand bisect the midline, thereby determining left-

ward/rightward orient ation bias. Despite limitations,the construct validity,110 reasonable sensitivity andreliability, and ease of administration render thisa good supplementary pencil-and-paper test.8 The

minimal time required for administration is a majoradvantage for clinicians.On the other hand, copying and drawing tasks

(Fig. 1) are the least satisfactory pencil-and-papertests in terms of sensitivity, reliability, and validity,8

but have a place in gaining an understanding of thenature of the morbidity.

Lindell et al104 and Jehkonen et al80 havehighlighted the benefit of combining several toolsin yielding a higher detection rate and bettercharacterization of VN. On the basis of the availableevidence, the star cancellation test, coupled with theline bisection test, are recommended as screeningtools for all patients with hemispheric stroke.

2. Behavioral Assessment Tools

Azuovi et al found that behavioral assessment hasa much higher sensitivity than pencil-and-paper tests(96% vs 65%).5 This finding is in accordance withother similar studies.6,61 Therefore, behavioralassessment is essential to enhance VN detectionrate and, more importantly, to determine andevaluate the nature and level of functioning.4

The BIT and the Catherine Bergego Scale (CBS)

are two of the most frequently used tests. The BIT

176

is




a 15-item checklist, which comprises six conventionaltests (line crossing, letter cancellation, star cancella-tion, figure copying, line bisection, and free drawing)and nine behavioral tests (picture scanning, tele-phone dialing, menu reading, article reading, tellingand setting the time, coin sorting, address andsentence copying, map navigation, and card sorting).There is consistent evidence showing that BIT servesas a good predictive measure of functional perfor-mance in daily living.62,115 The major limitation of this battery is that it does not formally assess thepersonal space. This is imperative because eachof theneglect subtypes (personal, peripersonal, and extrap-ersonal) can manifest as a separate entity.

On the other hand, the CBS7 is a 10-item checklist that focuses on functional performance of activitiesof daily living. These include grooming and shavingthe left part of the face, wearing the left sleeve orslipper, eating food on the left side of the plate,

cleaning the left side of the mouth after eating,spontaneous leftward gaze, ‘‘knowledge’’ of the left part of the body, auditory attention to stimuli fromthe left, collisions with objects on the left, leftwardnavigation in familiar places, and locating familiaritems on the left. Although this test was originally designed for the assessment of left VN, it should beapplicable to right VN. We prefer CBS over BITbecause CBS considers all three conceptual spaces,includes anosognosia scoring,7 and has fine psycho-metric properties, including validity, sensitivity, andreliability.5,115 Anosognosia scoring serves as an

important indicator of VN severity.51,137 We recommend that all patients who demonstrate

spatial orientation bias on VN screening test shouldundergo some form of behavioral assessment likeBIT or, preferably, CBS.

3. Clinical Observation and History-taking from

the Patient and the Near Contacts

Skilled clinical obser vation should increase thedetection rate of VN,81 which may be missedbecause of the false negative result of the standard-ized test s and VN’s inherently subtle and fluctuatingcourse.2 Family and friends who are familiar witha patient’s normal behavior may also play a signifi-cant role in picking up subtle neglect behavior. VNmay be missed during the acute phase of stroke but may be picked up later by other allied healthprofessionals or at home by the near contacts.

4. Recent Development of Assessment

Technique

One of the main shortcomings of the pencil-and-paper tests is the inability to differentiate between

sensory/input and premotor/output neglect, as

T a b l e 3 ( c o n t i n u e d

)

T

e s t s

B r i e f

D e s c r i p t i o n / R a t i o n a l e

S t r e n g t h

L i m i t a t i o n

O c u l o g r a p h y 3

0

R e q u i r e s t h e p a t i e n t t o

f o c u s a t t h e m i d p o i n t o f a g i v e n o b

j e c t ,

i m a g e o r t a s k

L o o k i n g f o r o r i e n t a t i o n b i a s t o w a r d s t h e i p s i l e s i o n a l s i d e w h i c h

i n d i c a t e s V N

A l l o w s p u r e a s s e s s m e n t o f V N

a s m a n u a l e x p l o r a t i o n

i s n o t r e q u i r e d

, w h i c h t h u s

e x c l u d e s t h e m o t o r

c o m p o n e n t / p r e m o t o r n e g l e c t

T h e r e i s n o

r o b u s t e v i d e n c e o n

t h e v a l i d i t

y , s e n s i t i v i t y , a n d

r e l i a b i l i t y

o f t h i s t e s t

D o e s n o t a s s e s s p e r s o n a l s p a c e

V i r t u a l r e a l i t y

R e q u i r e s a s e t o f h a r d w a r e ( i . e . ,

h e a d - m o u n t e d d i s p l a y ) , e y e

t r a c k e r s , a n d h e a d - p o s i t i o n s e n s o r

E n a b l e s t h e u s e r s t o e x

p l o r e r e a l - t i m e v i r t u a l i m a g e s w h i l e

r e l e v a n t i n f o r m a t i o n

i n c l u d i n g h e a d m o t i o n ,

s c a n n i n g p a t t e r n ,

a n d s p a t i a l o r i e n t a t i o n a r e r e c o r d e d a n d a n a l y z e d

A l l o w s a s s e s s m e n t i n a s i m u l a t e d e n v i r o n m e n t r e -

l a t i n g t o d a i l y l i f e

C r e a t e s a m o r e i n t e r a c t i v e , v e

r s a t i l e a n d s a f e r

e n v i r o n m e n t f o r a s s e s s m e n t

o f V N

P r e s e n c e o f e y e t r a c k e r s a i d t h

e a s s e s s o r t o r e c o r d

p a t i e n t ’ s v i s u a l s e a r c h p a t t e r n a n d d e v e l o p b e t t e r

u n d e r s t a n d i n g o f t h e n a t u r e o f V N

F o c u s e s o n p e r i p e r s o n a l s p a c e

V i s u o s p a t i a l

p e r c e p t i o n i n t h e

v i r t u a l e n v i r o n m e n t m a y v a r y

b e t w e e n i n d i v i d u a l s 7

8

F u r t h e r e v a l

u a t i o n o f v a l i d i t y ,

s e n s i t i v i t y ,

a n d r e l i a b i l i t y i s

r e q u i r e d

a T h e s e i n v e s t i g a t i o n s o n l y e v a l u a t e a t t e n t i o n f o r p e r i p e r s o n a l s p a c e a n d c a n n o t d i f f e r e n t i a t e b e t w e e n i n p u t a n d o u t p u t n e g l e c t .

T

h i s t a b l e i s m o d i fi e d f r o m P l u m m e r

e t a l .

1 3 7




these tests require both visual attention and manualexploration. Chiba et al30 have proposed the use of oculography for the midpoint-fixation task, whichremoves the manual component.

Virtual reality (VR) based techniques may poten-tially overcome the shortcomings of traditionalassessment methods.94 The use of VR systems not only helps to establish a better assessment andunderstanding of the nature of VN, but also createsa safe, versatile, and multimodal virtual environ-ment to assess the patient’s functional performance

in a range of daily living tasks. Conventional testsincluding the line bisection test, the cancellationtest, and daily living tasks ha ve all been incorpo-rated into a VR system.166 However, the VR assessment focuses on use of peripersonal and, toa certain extent, extrapersonal space and furtherevaluation is required to determine its sensitivity,cost-effectiveness, and practicability.

C. DISTINCTION BETWEEN VISUAL NEGLECT

AND OTHER VISUAL PROBLEMS

VN is commonly associated with other visual

problems, including visual extinction and homony-

mous hemianopia (HH). Therefore, understandingof the nature of these visual problems and thedistinct features of each visual condition shouldfacilitate assessment and diagnostic process.

Visual extinction is described as the failure of identifying one of two simultaneous stimuli, whileretaining the perception of a stimulus presentedsingly in either hemispace.169 Unlike VN, theallocation of attention in the cont ext of visualextinction is largely task-dependent.172 For instance,the ability to localize stimuli on bilateral display can be

markedly impaired (similar to neglect), but withretained normal reporting of numerical stimuli onbilateral presentation.172 Extinction may also occur

when both stimuli are presented simultaneously within the same hemifield.172 Nonetheless, visualextinction has been described as a cardinal signindicative of a deficit in attention,16,139 or as part of neglect disorder.67 Clinically, visual extinction shouldbe sought during neurological examination, as visualextinction and neglect are commonly, but not in-

variably, associated.49 This can be done by asking thepatient to point to the examiner’s moving finger,

initially onesideat a time andthen bilaterally inmirror

Fig. 1. Examples of patient with VN neglecting the stimuli on the left hemispace in: (A ) a cancellation task; (B ) a linebisection task; and (C ) a copying and drawing task. (Adapted from http://ahsmail.uwaterloo.ca/waktse/assessment.html.)


http://ahsmail.uwaterloo.ca/~aktse/assessment.html








image quadrants. The ability to identify a singlestimulus, but not simultaneous stimuli, defines extinc-tion. In addition, Hillis et al68 have shown that visual,tactile, and motor extinction involve mainly the visualassociation cortex, the inferior parietal lobe, and thesuperior temporal gyrus, respectively. These anatom-ical findings, which considerably overlap with theneural underpinnings of VN, help explain thefrequent co-occurrence of both VN and extinction.

Involvement of ophthalmologists and orthoptistsis of potential value, as ‘‘egocentric’’ visual neglect may occasionally coexist with, or masquerade as,a visual field defect,101 despite their distinct patho-physiology. Egocentric VN is characterized by in-attention toward the contralesional hemispace,

which is independent of the direction of gaze, whereas HH is the actual loss of visual field of contralesional hemispace, which can be compen-sated by the head and eye movements. Scanning

behavior, which relies on spatial attention, serves asthe primary distinguishing factor. Patients with VNcan have profound difficulties in surveying andnavigating the visual scene in affected hemispaceand cannot consciously compensate for within theneglected hemispace. In contrast, HH poses a lesssignificant impact on the affected individual’sscanning behavior because spatial attention of oneside of the visuospatial world is retained, thereby allowing compensatory movement of the eye, head,and body towards the affected visual field. There-fore, behavioral assessment can be very useful in

differentiating these two disorders.In addition, VN, but not HH, is commonly

associated with visual extinction.49 Also, othermodalities such as somatosensory, auditory, andmotor neglect may coexist with VN, whereas HH isstrictly a visual deficit. Visual evoked potentials(VEPs) are increasingly used to differentiate VNand HH. Patients with VN usually have a nearnormal response on VEPs,160 whereas patients withHH commonly demonstrate marked disparity be-tween the normal and affected hemifields.90 Inaddition, various alternative methods hav e been

proposed to distinguish these conditions93

(Table4). Such differentiation may be difficult, as they may overlap or be compounded by a condition calledhemianopia anosognosia, which is characterized by unawareness of the visual field loss.18,29

D. SUMMARY AND RECOMMENDATIONS FOR THE

ASSESSMENT OF VISUAL NEGLECT

Despite a lack of consensus regarding neglect assessment, we recommend that health professionalsroutinely assess for personal, peripersonal, and

extrapersonal neglect, and, more importantly, the

level of independence in activities of daily living. Werecommend that the star cancellation test and theline bisection test should form part of the routinecognitive assessment battery. This approach is best coupled with the Catherine Bergego Scale andcontinuous clinical observation via multidisciplinary teamwork. Application of virtual reality--based assess-ment may be of potential value in future practice.In addition, it is imperative to distinguish VN fromother visual problems, especially homonymoushemianopia.

VII. Rehabilitation of Visual Neglect

There is an extensive body of literature concern-ing the effectiveness of the rehabilitation of VN. Inorder to minimize the selection bias and enhancethe level of evidence, we have, therefore, centered

analysis on high-quality literature such as systematicreviews and randomized controlled trials. Relevant evidence3,20,50,82,103,106,136,140 regarding the effec-tiveness of rehabilitation is summarized in Table 6.

A. CURRENT CLINICAL PRACTICE

Clinical guidelines77,154 recommend a multidisci-plinary approach in managing cognitive impairment including visual neglect but there is no clear andspecific guidance on the choice of interventions. Asa result, heterogeneous interventions are applied by different institutions, depending on the local

guidelines, health professionals’ clinical experience,and clinical resources.

B. TYPES OF REHABILITATION

Interventions include utilizing remaining intact brain function (compensation), adaptation to theimpairment by using prosthetic devices or environ-mental modification (substitution), or retraining of the impaired function (restitution).92 Althoughcertain interventions involve more than one mech-anism, some fall outside this classification. Wesummarize available interventions (Table 5) and

their effectiveness (Table 6). Traditionally, rehabil-itation focused upon the compensatory and sub-stitutive interventions as the brain was thought tohave limited regenerative ability. However, recent evidence suggests that the brain has the ability to reorganize and reconstruct following damage(neuroplasticity ),22,78,91,112 suggesting the possibility of success of restitutive rehabilitation.

1. Compensatory

Visuospatial perception relies on intact internalsubconscious computation of the outer world

along with feedback from different sensory




modalities.19,75,125,127,175 The compensatory, bot-tom--up approach of rehabilitation focuses on themodulation of the afferent inputs towards thecentral internalized process of the inner mind by utilizing the remaining intact brain function and

various afferent/sensory modalities, including vi-sual, tactile, vestibular, extraocular, and neck muscleproprioception. This type of intervention does not address the underlying lack of self-awareness of thedeficit by the affected individuals, resulting in only short-lived improvement. Some interventions, suchas feedback training and r-TMS, may involve morethan one mechanism (Table 5).

2. Substitutive

This form of rehabilitation involves neither mod-

ulation of afferent inputs nor enhancement of self-awareness, but rather adaptation to the underlying

visual neglect with the aid of rehabilitative measuressuch as prism adaptation, visual scanning therapy,and environmental modification. These methodspotentially impact VN more than pure compensatory interventions, as the improvement of VN relies onboth adaptation and subconscious activ e learning,taking advantage of neuroplasticity.145 Also, theaffected individuals may sometimes benefit from‘‘substitutive’’ measures rather than ‘‘restitutive’’methods as they are so severely affected that the

underlying deficit cannot be appreciated (Table 5).

3. Restitutive

This form of rehabilitation focuses on retrainingof the impaired function92 and the modulation of the internalized perception of the outer world,

rather than altering the afferent inputs. This may beachieved by increasing self-awareness with mentalimagery, transcranial magnetic stimulation, virtualreality--based space remapping, and, potentially,feedback training (Table 5).

C. CURRENT EVIDENCE ON THE EFFECTIVENESS

OF REHABILITATION

As a result of our literature search, eight systematic reviews3,20,50,82,103,106,136,140 concerningthe effectiveness of rehabilitation were identified;they are summarized in Table 6.

Visual scanning therapy (VST) and prism adapta-tion are the two best-studied neglect rehabilitativeinterventions, probably on account of the ease of administration, cost-effectiveness, and easily repro-ducible positive results. Jutai et al,82 Luaute et al,106

and Pizzamiglio et al136 recommend the use of VST inpatients with VN. Generalization of task-specific effectst oa f unctional level hasbeen documented by Geusgenet al.50 However, the role of additional passive sensory stimulationin the context of VST is inconclusive.136,153

There is strong evidence demonstrating that prismadaptation helps rehabilitate VN.3,106 Long-term

beneficial effects can be achieved via a short period

TABLE 4

How to Distinguish Visual Neglect from Homonymous Hemianopia

Criteria Visual neglect Homonymous Hemianopia

Visual behavior Lack of attention to contralesionalhemispace, independent of thedirection of gaze

Loss of visual field of contralesionalhemispace, with respect to theposition of the head and eyes

Awareness of deficit Usually unaware of own deficit Usually retains awareness to acertain extent

Location of lesion Usually within the territory of themiddle cerebral artery

Usually within the territory of theposterior cerebral artery

Uni- vs multi-modal deficit May associate with other modalitieslike auditory, tactile and motor

Strictly confined to visual modality

Extinction Frequently associated49 Less commonly associatedDrawing from memory Commonly leave out the details on

the affected hemispaceNormal and symmetrical

Visuospatial disorder More commonly affected Usually not affectedLine bisection Ipsilesional deviation Usually contralesional deviation122

Attentional ‘‘cueing’’ strategies Presence of cueing may ameliorateneglect (usually transiently)

Presence of cueing does not modulate the disorder

Specific perimetric techniques Difficulty in maintaining centralfixation

Good control of central fixation

VEP and eye movement registration Near normal response to stimulationon both sides but prolongedlatency may be demonstrated onthe affected side160

Marked disparity between thenormal and affected hemifield90

VEP 5 visual evoked potentials.This table is modified from Kerkhoff et al.93




of prism adaptation42 and ongoing improvement hasbeen observed e ven 5 weeks after the active phase of rehabilitation.45 Such long-term effects do not occur

with passive Fresnel prism exposure,118 demonstrat-ing that improvement relies on more than just modulating the afferent inputs, and requires thefeedback loop of rewarded motor activity.

Nonetheless, the vast majority of the prism adapta-

tion studies are case reports or small case series. A

recent single-blind randomized controlled pilot t rialof 34 neglect patients conducted by Turton et al168 hasshown that prism adaptation does not provide any beneficial effect on the functional performance of the

VN patients, as measured by CBS and BIT, despite theimprovement of pointing behavior. The inconsistent effect of prism adaptation observed across different studies may be influenced by the inconsistency of

prism adaptation methods used, the disparity of

TABLE 5

Summary of Underlying Rationale/Concepts for Various Types of Rehabilitation for Unilateral Neglect

Types Interventions Brief Descriptions/Proposed Rationale

Compensation Visual scanning therapy 174,178 Re-develop an organized scanning pattern by learningsystematic right-to-left search

Optokinetic stimulation124 Induce left pursuit movement with the aid of leftward

moving background targetsLimb activation143 Improve attention on the neglected hemifield by moving

the contralesional limb in the neglected hemispaceTraining with ‘‘cueing’’174 Activate attention on the neglected side with ‘‘cueing’’

stimuli (visual, auditory or tactile)Neck muscle vibration86,88,152 Re-center the spatial egocentric frame of reference by

modifying the afferent neck proprioceptive inputsrelative to the position of the head to the trunk

Trunk rotation44,88 Re-center the spatial egocentric frame of reference by modifying the afferent information relative to theposition of the head to the trunk

Caloric stimulation147 Induce nystagmus towards the affected side with coldcontralesional or warm ipsilesional caloric stimulation

Eye patches44,179 Increase leftward saccades by occluding the unaffectedright hemifield

Fresnel prisms148 Shift the affected visual hemifield towards the unaffectedipsilesional egocentric frame of reference

Sustained attention training144 Improves spatial attention by generating general arousalsystem

Substitution Prism adaptation3,118,146 Recalibrate the midline of the egocentric reference frameby using prism adaptation and successive visuo-motoractions; an after-effect of leftward shift towards theneglected hemifield following prism removal may improve VN

Diminished backgroundpattern and foreground clutter35

Minimize the required visual attention during visual scenenavigation by reducing the background and foregroundenvironmental distracters

Restitution Pharmacological treatment 107 Improve general non-spatial attention by using dopamineand norepinephrine agonists

Mental imagery 158

Improve representational (imagery) neglect by using visual or movement imagery VR space remapping1 Remap the egocentric reference frame towards the

affected hemifield by using VR systemCompensation and

Restitution Feedback training159 Increase patients’ self awareness (restitution) with

feedback sessions (video, mirror, verbal, visuomotor)following certain tasks, point out their neglect behavior,and teach them the ‘‘compensatory’’ strategies toimprove functional performance

r-TMS/direct polarization99,128,129

Disrupt the integrated neural activity of the intact side,dampen the attention to the ipsilesional side andthereby restore the orientation balance between bothhemispheres (compensation),99,128 or alternativel y,induce the process of neuroplasticity (restitution)129

Unknown Music therapy 53 Stimulate cognitive function via sensory and emotional

stimulation

VR 5 virtual reality; r-TMS 5 repetitive transcranial magnetic stimulation.




TABLE 6

Synthesis of Reviews of Evidence of Effect of Interventions for Visual Neglect 3,20,50,82,103,106,136

Reviews Included Studies Aims Key Findings

Arene 20073 31 studies—mixed trials of different quality

Assess mainly the effectivenessof passive sensory stimulation, prism

adaptation, visual scanningtherapy, andpharmacological treatment

➢ Passive sensory stimula-tion only confers short-lived improvement

➢

Prism adaptation demon-strated long term func-tional gain

➢ Visual scanning therapy has no significant impacton overall function

Riggs 2007140 27 studies—11 RCTs, 3 non-RCTs, 13 case studies

Assess the effectiveness of visuoperceptual therapy,prism adaptation, eyepatches, and visuomotorfeedback

➢ Improvement was ob-served with hemifield eyepatching, prism adapta-tion, and visuomotorfeedback, mainly by means of standardizedneglect test like line bi-section tests and cancel-lation tests

Geusgen 200750

7 studies—1 RCT, 3 singlesubject, 2 pre-test post-test,1 case control

Evaluate the ‘‘transfer’’ of theeffect of visual scanningstrategies from trained tasksto daily tasks or daily living

➢ Almost all confer positiveimpact on daily tasks ordaily living but three of seven were not statisticallytested

Bowen 200720 12 studies—all RCTs Assess overall effectiveness of cognitive rehabilitation for visual neglect onindependence of activitiesof daily living

➢ Only spatiomotor cue-ing83 confers statistically significant improvement on performance instandardized neglect assessment

➢ None showed statisticalsignificance in functionalperformance

Lincoln 2006103 25 studies—12 RCTs of aboveand 13 CCTs

Assess overall effectiveness of various interventionsrelating to visual neglect

➢ Rehabilitation observedslight immediate andpersisting improvement on standardised neglect test

➢ Effect on functioning wasstatistically insignificant,for either immediate orpersisting effects



Table 6 (continued )

Reviews Included Studies Aims Key Findings

Luaute 2006106 54 studies -- RCTs, controlledtrials, crossover, case-control, single-case, andcase reports

Assess the effectiveness of various interventionsrelating to visual neglect

➢ Improvement has beenobserved following VST,mental imagery and videofeedback training

➢ TR and NMV is partially effective when coupled

with visual scanningtherapy

➢ Fresnel prism and passivesensory stimulation donot afford positive func-tional impact

Pizzamiglio2006136

12 studies— group studies andsingle cases

Assess the effectiveness of visual scanning therapy withand without additionalpassive sensory stimulation

➢ VST serves as a usefulneglect rehabilitativeintervention

➢ No beneficial effect gained with additionalperipheral sensory stimulation

Jutai 20038232 studies, including RCTs,

crossover, cohorts, andsingle group designs

Investigate effectiveness of a variety of interventionsrelating to visual neglect

➢ There is strong evidencethat rehabilitation specif-ically targeting visual ne-glect and visual scanningimproves functionalperformance

➢ There is moderate evi-dence that Fresnel prismsand hemifield patchingimprove performance instandardized neglect tests

➢ There is limited evidencein favor of TENS, limbactivation, dopamine ag-onist therapy, caloricstimulation improving vi-

sual neglect CCT 5 controlled clinical trial; NMV 5 neck muscle vibration; RCT 5 randomized controlled trial; TR 5 trunk rotation; VST

transcutaneous electrical nerve stimulation.



number and duration of therapeutic sessions in-stituted, and the difference in outcome measuresapplied. This study did not address the anatomicalregions involved in their neglect patients. This isimportant because some studies have suggested that any potential beneficial effects of prism adaptationmay be lesion site--specific.151,155

The effectiveness of rehabilitation based onpassive sensory stimulation, such as eye patches,Fresnel prism, trunk rotation, neck muscle vibra-tion, limb activation, vestibular stimulation, andoptokinetic stimulation, remain inconclusive orunsatisfactory.3,106

Although it seems logical that longer-term benefitsmay be achieved with restitutive rehabilitation, theevidence is limited. Within the context of restitutiverehabilitation, Luauteet al106considermentalimagery and feedback training, as Grade B interventions,135

largely because theevidence of benefitisonlybasedon

a case study of two patients.158 The efficacy of pharmacological treatment (dopamine and norad-renergic agonists), transcranial magnetic stimula-tion128 or direct current polarization,99 virtualreality--based space remapping,1 and music therapy mustbe deemed inconclusive.158Thereareconflictingresults from single case reports of the use of dopamineand norepinephrine agonists to improve generalattention.3,10,72 Virtual reality--based space remappinghas shown to be of potential value, but has beenrestricted to patients who hav e normal inferiorparietal/superior temporal lobes.1

The systemat ic reviews of Bowen et al20 andLincoln et al103 have concluded that none of theinterventions lead to a positive impact on functionalperformance. They excluded the majority of theresearch trials because of unsatisfactory levels of evidence, highlighting the pressing need for highquality research.

D. SUMMARY AND RECOMMENDATION FOR

REHABILITATION OF VISUAL NEGLECT

The overall efficacy of rehabilitation remainsuncertain. Based on the best available evidence, wefeel that visual scanning therapy and prism adapta-tion warrant consideration. In our experience,education and training of family and close friendsto understand the nature of VN and how to assist VNpatients on a daily basis are equally important.

VIII. Prognosis

A few studies have observed spontaneous recovery in patients with mild to moderate visual neglect,especially during the acute phase,41 and recov ery

has been seen up to 90 days post-stroke.

126

Unresolved visual neglect predicts poorer functionaland rehabilitation outcome in post-stroke pa-tients.79,89,163,165 Longer-term follow-up is required,as there has been no systematic reported evaluationof outcome beyond 1 year.79

IX. Conclusion VN is a common, but frequently overlooked,

condition. Greater awareness and understanding of this condition should improve the quality of life of post-stroke patients. Detection is by combination of pen-and-paper tests, behavioral assessment tools,clinical observation and history taking and, poten-tially, virtual reality assessment. Although there islack of robust evidence of the efficacy of VNrehabilitation, visual scanning therapy and prismadaptation warrant consideration. There is a press-ing need for well designed, high quality research,

particularly randomized controlled trials, todemonstrate the clinical efficacy of current rehabil-itation strategies. Increasingly sophisticated neuro-imaging tools, including magnetic resonancescanning coupled with detailed clinical observationand neuro-ophthalmic examination, will improveunderstanding of the nature of VN, enablinga deeper appreciation of how an individual with

VN recognizes, organizes, and orients ‘‘self’’ inrelation to the external environment.

X. Method of Literature Search

Multiple electronic databases (EMBASE, Cochranelibrary, and Medline) were searched, reference lists

were hand-searched, and experts in the field werecontacted to identify peer-reviewed literature con-cerning visual neglect. Key literature which addressesthe functional impact, neuroanatomical causes,assessment, and treatment of visual neglect wasidentified. Certain keywords were used during theliterature search, including visual neglect, unilateral neglect, visual inattention, and hemispatial neglect .

XI. DisclosureThe authors reported no proprietary or commer-

cial interest in any product mentioned or concept discussed in this article. Alex Pollock is employed by the Nursing Midwifery and Allied Health Profes-sionals (NMAHP) Research Unit, which is funded by the Scottish Government’s Chief Scientist’s Office.

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Outline

I. IntroductionII. Epidemiology

III. Varieties of neglect

A. Modality (input/output)

B. Spatial representationC. Range of space

IV. Functional impact V. Pathophysiology

A. Physiology of visuospatial perceptionB. Spatially lateralized dysfunction of visual

neglect C. Non-spatially lateralized dysfunction of vi-

sual neglect D. Role of non-visual afferent inputsE. Clinico-anatomical correlations of visual

neglect F. Clinical syndromes associated with visualneglect

VI. Assessment of visual neglect

A. Current clinical guidelinesB. How is visual neglect assessed?

1. Pencil-and-paper tests2. Behavioral assessment tools

3. Clinical observation and history-takingfrom the patient and the near contacts

4. Recent development of assessment technique

C. Distinction between visual neglect andother visual problems

D. Summary and recommendations for theassessment of visual neglect

VII. Rehabilitation of visual neglect

A. Current clinical practiceB. Types of rehabilitation

1. Compensatory 2. Substitutive3. Restitutive

C. Current evidence on the effectiveness of rehabilitationD. Summary and recommendation for reha-

bilitation of visual neglect

VIII. PrognosisIX. ConclusionX. Method of Literature Search

XI. Disclosure


Visual Neglect

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