The acute deafness of definite multiple sclerosis: BAEP patterns

Hearing abnormalities in multiple sclerosis: clinical semiology and pathophysiologic mechanisms

Auditory manifestations from multiple sclerosis (MS) are not as common as the well-recognized sentinel exacerbations of optic neuritis, partial myelitis, motor weakness, vertiginous episodes, heat intolerance, and eye movement abnormalities. This paper discusses four cases of auditory changes, secondary to MS, and describes the first case, to our knowledge, of palinacousis, the perseveration of hearing, despite cessation of the sound stimulus. For each we characterize the initial complaint, the diagnostic work up, and ultimately, underscore the individualized treatment interventions, that allowed us to achieve a remission in all four cases. Individually codifying the treatment regimens served to mitigate, if not to abolish, the clinical derangements in hearing. Special attention is focused upon examination of the clinical manifestations and the pathophysiologic mechanisms which are responsible for them. We further emphasize the differential diagnostic considerations, and physical exam findings, along with the results of laboratory testing, neuro-imaging sequences, and lesion localization. Taken together, such information is germane to organizing cogently coherent strategic treatment plan(s). We believe that this small case series represents a clinically pragmatic example of 'precision medicine'; a principal theme and goal throughout this paper, the achievement of such in MS, but also as an illustration for the assessment and management schema for neuroimmunologic disorders in general.

Effectiveness of Brainstem Auditory Evoked Potentials Scoring in Evaluating Brainstem Dysfunction and Disability Among Individuals With Multiple Sclerosis

Purpose The brainstem dysfunction in multiple sclerosis (MS) often causes significant functional impairment leading to disability. This study aims to explore modified brainstem auditory evoked potential (BAEP) scores based on the pattern of BAEP abnormalities and relate with brainstem symptoms, brainstem functional system scores (BFSS), brainstem lesions, and disability. Method Forty-five participants with relapsing-remitting MS and 45 age- and gender-matched healthy controls underwent case history assessment, otoscopic examination, pure-tone audiometry, and BAEP testing. Also, neurological examination (Expanded Disability Status Scale, FSS scales) and magnetic resonance imaging were carried out on MS participants. Patterns of BAEP abnormalities were categorized and converted to BAEP scores. Results Out of 45 participants' brainstem symptoms, BFSS > 1, brainstem lesions (magnetic resonance imaging), and BAEP abnormalities were observed in 75.6%, 42.2%, 62.2%, and 55.56% of participants, respectively. Waves V and III abnormalities were more common among MS participants and showed a significant difference from the control group in the Mann-Whitney U test. Chi-square test did not show a significant association of BAEP abnormalities with brainstem symptoms and lesions but showed significant association with BFSS. The mean and standard deviation of BAEP scores in MS participants were 1.73 + 2.37. All healthy controls showed BAEP scores of 0. BAEP scores in MS participants showed significant correlation with BFSS scores and predict Expanded Disability Status Scale scores. Conclusion BAEP scores based on the pattern of BAEP abnormality can be a valid and useful measure in evaluating brainstem functions and predicting disability in MS.

The audiovestibular manifestations as early symptoms of multiple sclerosis: a scoping review of the literature

BACKGROUND

Multiple sclerosis (MS) is an immune-mediated, demyelinating disease of the nervous system, which may impact the audiovestibular pathway at different stages of the disease. The auditory and vestibular manifestations of MS as a presenting or early symptom are an area in which more investigation is needed.

AIMS

The aim of this review is to determine the auditory and vestibular symptoms, which may occur at the presenting stage of multiple sclerosis. This clinical knowledge will allow a clinician to facilitate early diagnosis and intervention of MS through appropriate onward referral. Audiological and vestibular test results, as well as magnetic resonance imagery results, will also be examined to try to determine the impact of MS on the auditory and vestibular pathways.

METHODS

A scoping search of the electronic databases PubMed, Scopus, Web of Science, ScienceDirect, and EBSCO was conducted in March 2020 to obtain studies specifically of patients with audiovestibular symptoms at the early or presenting stages of multiple sclerosis. Data was extracted from studies which met the inclusion criteria and studies were subsequently critically appraised and assessed for risk of bias.

RESULTS

Eighteen papers met the inclusion criteria for this study. Results of the study found that the most common audiovestibular manifestation as a presenting symptom of MS was unilateral, moderate-profound, fluctuating, and sudden sensorineural hearing loss across all frequencies (250 Hz-8000 Hz). Other symptoms include tinnitus, balance abnormalities, aural pain and aural fullness, which may accompany SSHL or occur independently. The peripheral involvement of the immune-mediated mechanisms of MS was suggested by peripheral findings in vestibular examination results and the involvement of wave I ABR in patients with irreversible hearing loss. Demyelinating lesions associated with MS were suggested by results obtained from evoked potentials measurements, including ABR, VEMPs, and MLR.

CONCLUSION

An understanding of the sensitivity of evoked potentials in the detection of demyelinating lesions as well as the most common audiovestibular presentations of the disease allows the practitioner to provide an appropriate onward referral for MRI which may lead to early diagnosis and intervention of MS. We suggest that there is enough evidence to include evoked potentials complementary to MRI in the detection and monitoring of MS. As the review suggests evidence of involvement of the immune-mediated mechanisms of MS on peripheral structures like the inner ear, further clinical research is recommended to explore this mechanism. Key points 1. The most common audiovestibular manifestation as an early symptom of MS was unilateral moderate to profound SSHL across all frequencies (250 Hz-8000 Hz). 2. Findings of the review indicated the involvement of the immune-mediated mechanisms of MS in the peripheral structures of the inner ear. 3. These findings included peripheral results in the vestibular test of the patients involved in the study and secondly, the three studies which reported an absence of full recovery of hearing loss were also three papers which within their ABR results showed abnormality of wave I 4. This is the first paper to support the theory (Di Stadio et al. 2018) [32] that immune-mediated processes of MS can spread to peripheral inner ear structures 5. The review highlighted the sensitivity of evoked potentials in detecting MS lesions in the presenting stage, particularly ABR which demonstrated that in instances in which hearing loss recovered ABR results remained abnormal.

Subjective hearing ability, physical and mental comorbidities in individuals with bothersome tinnitus in a Swedish population sample

OBJECTIVE

This study investigates associations of subjective hearing ability, physical comorbidities, and mental comorbidities with bothersome (vs. non-bothersome) tinnitus and mediating effects between these influences.

METHODS

The Swedish LifeGene cohort was used to sample cross-sectional survey data (collected 2009-2016) of 7615 participants with tinnitus, 697 (9.2%) of whom rated their tinnitus as bothersome. Associations between bothersome tinnitus and subjective hearing ability, physical and mental comorbidities were investigated by separate age- and gender-adjusted multiple logistic regression models. Interrelationships between these associations were investigated by logistic mediation models.

RESULTS

Compared to non-bothersome tinnitus, bothersome tinnitus was associated with higher age, reduced subjective hearing ability, hearing-related difficulties in social situations, cardiovascular disease, chronic shoulder pain, thyroid disease, Ménière's disease, depression, anxiety syndrome, and social anxiety. Subjective hearing impairment or hearing-related difficulties mediated 13-36% of the effects of mental comorbidities on bothersome tinnitus. Depression or anxiety syndrome mediated 5-8% of most relationships between physical comorbidities and bothersome tinnitus. Depression, anxiety syndrome, or social anxiety mediated 2-4% of the effects of subjective hearing impairment or hearing-related difficulties on bothersome tinnitus.

CONCLUSION

Psychological factors, subjective hearing impairment, and hearing-related difficulties in social situations play key roles in predicting bothersome (vs. non-bothersome) tinnitus in a large population sample. Psychological factors contribute to explaining the impact of physical comorbidities and hearing-related effects on bothersome tinnitus. This highlights their transdiagnostic importance for aggravating varied physical symptom clusters. Interventions to improve or prevent high tinnitus burden should be interdisciplinary/multimodal and target auditory, physical, and psychological factors.

Acute vestibular syndrome and hearing loss mimicking labyrinthitis as initial presentation of multiple sclerosis

Acute vestibular syndrome is most often caused by vestibular neuritis or stroke, although demyelinating diseases may be responsible for 4% of all AVS episodes. The authors present the case of a previously healthy 17-year-old female patient complaining of spontaneous vertigo and right-sided hearing loss. Otoneurological examination suggested a peripheral vestibular cause and video head impulse test revealed a reduced vestibulo-ocular reflex gain. The presence of sensorineural hearing loss raised the suspicion of a central cause and prompted imaging evaluation. A brain MRI evidenced demyelinating lesions in the right middle cerebellar peduncle and the patient was ultimately diagnosed with Multiple Sclerosis.

Sequential Bilateral Hearing Loss in Multiple Sclerosis

Objectives: We describe a case of multiple sclerosis presenting with sequential bilateral hearing loss.

Methods: A 46-year-old woman underwent a series of audiological and neurologic evaluations for sequential bilateral hearing losses that occurred 6 months apart.

Results: Initially, the patient suffered from sudden left hearing loss, and magnetic resonance imaging documented an enhancing lesion in the left middle cerebellar peduncle. Six months later, another episode of sudden vertigo, right hearing loss, and right facial palsy developed. Magnetic resonance imaging disclosed a new lesion in the right middle cerebellar peduncle.

Conclusions: Sequential bilateral hearing loss may be a manifestation of multiple sclerosis. In younger patients with sudden hearing loss, multiple sclerosis should be included in the differential diagnosis.

Association of multiple sclerosis and sudden sensorineural hearing loss

Background

Multiple sclerosis (MS) may affect other cranial nerves besides the optic nerve. Sudden sensorineural hearing loss (SSHL), possibly caused by a deficit in the auditory tract, including the vestibulocochlear nerve, is sometimes associated with MS.

Objectives

We aimed to assess the incidence of SSHL among MS patients, its frequency as an initial symptom of MS, and magnetic resonance imaging (MRI) findings associated with SSHL in MS.

Methods

We collected retrospectively all patients diagnosed with MS and SSHL at the Helsinki University Hospital between 2004 and 2014. Patients with both diagnoses were re-evaluated using hospital medical records, audiograms and head MRI scans.

Results

A total of 2736 patients were diagnosed with MS, 1581 patients with SSHL, and 18 patients (0.7% of all MS patients) with both; two patients presented with SSHL as an initial symptom of MS. The annual incidence of SSHL was 59.8/100 000 (95% confidence interval (CI) 37.7–94.9) in MS patients, and 12.4/100 000 (95% CI 11.8–13.0) in the normal population.

Conclusion

SSHL is a rare symptom of MS and is even less frequent as an initial symptom. Its incidence in MS patients, however, markedly exceeds that in the normal population.

Isolated deafness in multiple sclerosis patients

Isolated cranial nerve involvement in multiple sclerosis (MS) patients is not frequent. Deafness is considered to be uncommon in MS patients. We have reviewed the sensorineural hearing loss episodes that had been thoroughly investigated in our hospital in the last 5 years. We present three cases of sensorineural hearing loss in patients with MS and compare them with other previously reported and discuss this uncommon symptom. The cases that we present were firstly evaluated by an otolaryngologist. A lesion is seen at the root-entry zone of the eighth cranial nerve in only one case, but no lesions are seen in the other cases. A retrocochlear demyelinating disorder was demonstrated in the two patients in whom brainstem auditory evoked potentials were performed. All patients recovered at least partially their hearing functions.

Magnetic Resonance Imaging Findings in Children With Tinnitus

Objective:

Tinnitus in adults is generally investigated by contrast-enhanced magnetic resonance imaging (MRI) to rule out the diagnosis of acoustic neuroma. Acoustic neuroma is rare in children and, therefore, the role of MRI in children with tinnitus is unclear. This study was undertaken to determine the value of MRI in the investigation of tinnitus in children.

Methods:

Retrospective study of children younger than 18 years who underwent MRI for the investigation of tinnitus over a 10-year period.

Results:

Sixty-five patients were identified, but there were only 34 who had also undergone audiologic assessment. Among the 25 patients with normal audiology, MRI abnormalities were present in 9, but these were all thought to be nonspecific. Nine patients had abnormal audiograms and the MRI was abnormal in 4 of these cases, which included 3 children who were found to have multiple sclerosis.

Conclusion:

Magnetic resonance imaging would appear to be mandatory in the investigation of tinnitus in children who are found to have sensorineural hearing loss, particularly to rule out the diagnosis of multiple sclerosis. Although our study does not support the routine use of MRI in children with normal audiology, the numbers in our series are too small for a conclusive recommendation.

Pure-tone auditory thresholds are not chronically elevated in multiple sclerosis

Despite the fact that acute cases of multiple sclerosis (MS)-related pure-tone hearing loss have been reported in the literature, consensus is lacking as to the chronic influences of MS on pure-tone thresholds. Most studies examining such influences have been limited by small sample sizes, lack of statistical comparisons between patients and controls, and confounding of the hearing measure with influences from sex and age. To date, associations between pure-tone thresholds and central MS-related brain lesions have not been assessed. In this study, pure-tone thresholds ranging from 0.5 to 8 kHz were measured in 73 MS patients and 73 individually age- and gender-matched normal controls. In 63 MS patients, correlations were computed between the threshold values and MRI-determined lesion activity in 26 central brain regions. Although thresholds were strongly influenced by sex, age, and tonal frequency, no meaningful influences of MS were discerned. Moreover, no significant association between the threshold values and central MS-related lesion activity was evident in any brain region evaluated. This study, the largest on this topic to use carefully matched control subjects and the sole study to assess relationships between auditory thresholds and central MS-related lesions, strongly suggests that (a) MS is not chronically associated with pure-tone hearing loss and (b) pure-tone thresholds are unrelated to MS lesion activity in higher brain regions. These findings, along with general reports from the literature, support the concept that when MS-related hearing threshold deficits are found, they are episodic and primarily dependent on lesions within the eighth nerve or brainstem.

Sudden sensorineural hearing loss in multiple sclerosis: clinical course and possible pathogenesis

OBJECTIVE - To assess the symptom of sudden hearing loss in multiple sclerosis (MS). METHOD - We reviewed patient files in our MS clinic between January 2004 and November 2009 for symptoms of sudden hearing loss. RESULTS - We were able to identify 11 of 253 patients (4.35%) with sudden hearing loss. In seven patients, the hearing decline was the presenting symptom of MS and in all 11 patients, it appeared early in the course of the disease. There was no residual hearing deficit in 9/11 patients. In no patient was the condition bilateral and in none did it recur. CONCLUSION - Episodes of hearing loss are not uncommon in MS and have a good chance of complete recovery.

Acute tinnitus and hearing loss as the initial symptom of multiple sclerosis in a child

Acute hearing loss with or without tinnitus has been reported in a number of adult series of multiple sclerosis (MS), but is considered a rare phenomenon. It generally occurs during disease exacerbations, rather than as an isolated finding or presenting feature. We present the case of an 11-year-old girl in whom persistent tinnitus and reversible hearing loss were the sole manifestation of MS at initial presentation.

Multiple sclerosis: a cause of sudden hearing loss

Sudden hearing loss is a clinical entity which has numerous aetiologies. In cases where the aetiology is not determined, evaluation and treatment of sudden hearing loss are very difficult. A case of probable multiple sclerosis with sudden hearing loss as the initial symptom is reported. The pure-tone audiometry showed a quasi-total sensorineural hearing loss in the left ear; the left side displayed only wave I in the auditory brainstem response (ABR). Electronystagmographic examination revealed hypometric dysmetria and saccadic pursuit abnormalities. Magnetic resonance imaging (MRI) showed high-intensity lesions with multiple foci. After steroid therapy, the patient's hearing loss, vertigo and visual problems improved, but the ABR findings remained unchanged. We have decided to present this case because of the interesting ABR finding revealing the presence of wave I and the absence of all other waves after the normalization of the hearing.

Role of acute cochlear neuritis in sudden hearing loss in multiple sclerosis

We report a patient with definite multiple sclerosis (MS) who developed unilateral sudden hearing loss coincident with exacerbation of central nervous system symptoms. Involvement of the peripheral cochlear nerve, suggested by auditory findings including auditory brainstem response, was confirmed by magnetic resonance imaging. The clinical, electrophysiological and neuroradiological abnormalities disappeared in response to steroid pulse therapy. These findings suggest that acute inflammatory demyelinative lesion of the peripheral cochlear nerve can occur in MS, manifesting sudden hearing loss.

Appropriateness of Magnetic Resonance Imaging in Sudden Sensorineural Hearing Loss

Idiopathic sudden sensorineural hearing loss is an enigmatic condition of unknown cause. Although the treatment for sudden sensorineural hearing loss is controversial, the evaluation for a cause should not be. All patients are evaluated with a complete history, physical examination, audiologic examination, and blood draw to evaluate complete blood count, general chemistry screen, thyroid function test results, erythrocyte sedimentation rate, and fluorescent treponemal antibody absorbance. Magnetic resonance imaging with gadolinium contrast is essential in the evaluation of idiopathic sudden sensorineural hearing loss, even if there is a complete response to either treatment or no treatment. During the last year we treated 16 patients for idiopathic sudden sensorineural hearing loss with our protocol of intravenous dextran/Hypaque or oral high-dose steroids. Fifteen patients were evaluated immediately before treatment with a magnetic resonance imaging scan. An additional patient had been treated successfully with high-dose steroids at an outside institution and came in for an evaluation. Of these 16 patients, 3 (18.75%) were found to have significant pathologic conditions on magnetic resonance imaging scan. The patient who had been treated successfully on the outside was noted to have a 5-mm intracanalicular acoustic neuroma, the second patient was found to have a multiple sclerosis lesion at the level of the superior olive, and the third patient, who had had a normal magnetic resonance imaging scan 18 months previously, was now found to have a large 4- to 5-cm meningioma in the cerebellopontine angle. We believe it is essential that all patients with idiopathic sudden sensorineural hearing loss be evaluated at some point during their treatment with a magnetic resonance imaging scan with gadolinium contrast.

Hearing loss in multiple sclerosis: localization of the auditory pathway lesion according to electrocochleographic findings

Multiple sclerosis is known to affect the myelin of the auditory pathway resulting in acute hearing loss. Two cases of sudden deafness due to multiple sclerosis have been evaluated by conventional audiometry, brainstem auditory evoked response audiometry and transtympanic electrocochleography. The abnormalities of the compound action potential in both patients (enhanced latency, abnormal adaptation using fast stimulus rate) and the normal receptor potentials (cochlear microphonic, summating potential), as well as the absence of brainstem responses suggest a disturbance of synchronization at the level of the first auditory neurone. The electrocochleography provides valuable information for the topodiagnosis of this and other neural hearing losses, especially in the absence of reliable brainstem responses.

Evoked otoacoustic emissions and electrocochleography in a patient with multiple sclerosis

A 24-year-old woman with multiple sclerosis had right-sided hearing impairment with tinnitus. She underwent electrocochleography (ECochG) and examination of evoked otoacoustic emissions (EOAEs) to assess cochlear function. An acoustic probe to measure EOAEs was inserted into the external ear canal. The ECochG action potential and cochlear microphonics were recorded by a transtympanic needle electrode technique. Both fast and slow components of EOAEs appeared in either the period of deteriorated hearing acuity or when it was improved. They showed normal detection thresholds and input-output curves during both periods. Cochlear microphonics with almost normal detection thresholds and input-output functions were obtained during the period of deteriorated hearing acuity. Action potential (N1) input-output curves during relapse with hearing loss were notably lower in amplitude and longer in latency than those obtained at the time hearing impairment showed improvement. The EOAE and ECochG findings suggested that this patient had almost normal cochlear function, and we assumed from the magnetic resonance imaging and auditory brain stem response findings as well as the ECochG that the hearing impairment was caused by dysfunction of auditory pathways in the brain stem, including structures that contribute to generation of the N1 potential of the ECochG.

Effects of multiple sclerosis brainstem lesions on sound lateralization and brainstem auditory evoked potentials

Magnetic resonance (MR) imaging, brainstem auditory evoked potentials (BAEPs), and tests of interaural time and level discrimination were performed on sixteen subjects with multiple sclerosis (MS). Objective criteria were used to define MR lesions. Of the eleven subjects in whom no pontine lesions were detected and the one subject who had pontine lesions that did not encroach upon the auditory pathways, all had normal BAEPs and interaural level discrimination, although a few had abnormal interaural time discrimination. Of four subjects with lesions involving the pontine auditory pathway, all had both abnormal BAEPs and abnormal interaural time discrimination; one also had abnormal interaural level discrimination. Analysis of the data suggest the following: waves I and II are generated peripheral to the middle of the ventral acoustic stria (VAS); wave III is generated ipsilaterally in the region of the rostral VAS, caudal superior olivary complex (SOC) and trapezoid body (TB); and waves V and L are generated contralaterally, rostral to the SOC-TB. The region of the ipsilateral rostral SOC-TB is implicated as part of the pathway involved in the generation of waves V and L. Interaural time discrimination of both high and low frequency stimuli were affected by all brainstem lesions that encroached on auditory pathways. A unilateral lesion in the region of the LL affected interaural time discrimination for low-frequency stimuli less severely than bilateral lesions of the LL or a unilateral lesion of the VAS. The only interaural level discrimination abnormality occurred for a subject with a unilateral lesion involving the entire rostral VAS. It appears that detailed analysis of lesion locations coupled with electrophysiological and psychophysical data holds promise for testing hypotheses concerning the function of various human auditory brainstem structures.

Binaural auditory processing in multiple sclerosis subjects

In order to relate human auditory processing to physiological and anatomical experimental animal data, we have examined the interrelationships between behavioral, electrophysiological and anatomical data obtained from human subjects with focal brainstem lesions. Thirty-eight subjects with multiple sclerosis were studied with tests of interaural time and level discrimination (just noticeable differences or jnds), brainstem auditory evoked potentials and magnetic resonance (MR) imaging. Interaural testing used two types of stimuli, high-pass (> 4000 Hz) and low-pass (< 1000 Hz) noise bursts. Abnormal time jnds (Tjnd) were far more common than abnormal level jnds (70% vs 11%); especially for the high-pass (Hp) noise (70% abnormal vs 40% abnormal for low-pass (Lp) noise). The HpTjnd could be abnormal with no other abnormalities; however, whenever the BAEPs, LpTjnd and/or level jnds were abnormal HpTjnd was always abnormal. Abnormal wave III amplitude was associated with abnormalities in both time jnds, but abnormal wave III latency with only abnormal HpTjnds. Abnormal wave V amplitude, when unilateral, was associated with a major HpTjnd abnormality, and, when bilateral, with both HpTjnd and LpTjnd major abnormalities. Sixteen of the subjects had their MR scans obtained with a uniform protocol and could be analyzed with objective criteria. In all four subjects with lesions involving the pontine auditory pathway, the BAEPs and both time jnds were abnormal. Of the twelve subjects with no lesions involving the pontine auditory pathway, all had normal BAEPs and level jnds, ten had normal LpTjnds, but only five had normal HpTjnds. We conclude that interaural time discrimination is closely related to the BAEPs and is dependent upon the stimulus spectrum. Redundant encoding of low-frequency sounds in the discharge patterns of auditory neurons, may explain why the HpTjnd is a better indicator of neural desynchrony than the LpTjnd. Encroachment of MS lesions upon the pontine auditory pathway always is associated with abnormal BAEPs and abnormal interaural time discrimination but may have normal interaural level discrimination. Our data provide one of the most direct demonstrations in humans of relationships among auditory performance, evoked potentials and anatomy. We present a model showing that many of these interrelationships can be readily interpreted using ideas developed from work on animals, even though these relationships could not have been predicted with confidence beforehand. This work provides a clear advance in our understanding of human auditory processing and should serve as a basis for future studies.

The choice of ABR click polarity and amplitude variables in multiple sclerosis patients

Evoked brainstem responses (ABR) to 75 dB nHL condensation (C), rarefaction (R), and alternating (A = C+R) clicks were investigated in healthy subjects and in patients with multiple sclerosis. A new wave IV-V 'shape ratio' (SR IV-V) was most sensitive. SR IV-V correlated most strongly with clinical MS classification, and seemed to be rather specific for retrocochlear dysfunction. Wave IV-V amplitude was also more sensitive than the common IV-V amplitude ratio. The variability of latencies and interpeak latencies was lower in ABR to A clicks than in ABR to either R or to C clicks. In patients, fewer subcomponents were found in ABR to A than in ABR to R and C clicks. ABR to A clicks were on the average slightly more sensitive than either C or R click ABR. Our results suggest that both A-mode ABR and the 'dispersion' variable SR IV-V can be used without significant problems in the diagnosis of brainstem demyelination. A test protocol which requires ABR to both C and R clicks to be abnormal, will, however, be less sensitive, though probably more specific.

Eighth nerve signs in a case of multiple sclerosis

We evaluated a 25-year-old woman with multiple sclerosis who presented with the acute onset of a profound unilateral high-frequency, sensorineural hearing loss that resolved clinically within 10 days. Click-elicited brain stem-evoked responses were abnormal at the time of presentation and demonstrated only limited recovery over a follow-up period of 11 months. Magnetic resonance imaging disclosed a lesion in the eighth nerve root-entry zone and the cochlear nucleus. Our findings in this case support the hypothesis of eighth nerve root-entry zone involvement in sudden hearing loss in multiple sclerosis and reinforce the notion that click-elicited brain stem-evoked responses are useful primarily to evaluate the high-frequency regions of the auditory system.