Although hearing loss is considered a rare manifestation of MS, it is reported to occur at least once during the course of disease in 3.5% to 17% of patients with MS.¹,²,³,⁴ Rare reports of hearing loss as the initial symptom are also present in the literature.¹,⁵,⁶,⁷ A review of the case literature indicates a significant heterogeneity in the presentation of auditory abnormalities in MS, with cases describing patients presenting with different degrees of hearing loss, both unilateral and bilateral deficits, and temporal variation from sudden onset to progressive loss. Thus, no characteristic pattern of auditory abnormalities has been defined for MS. Still, certain more common features of MS-associated hearing loss can be extracted from the small cohort studies and cases in the literature.

Both vertigo and tinnitus are frequently associated with symptoms of hearing loss, although certain cases report hearing loss as a clinically isolated syndrome.⁷,⁸,⁹,¹⁰,¹¹ Presentations of progressive hearing loss in MS are likely a result of lesions in the auditory brainstem pathways, and symptoms are driven by the specific location of the patient’s lesions. Notably, one study identified a greater than 4.5 times increased annual incidence of sudden sensorineural hearing loss (SSNHL) in people diagnosed with MS compared with the normal population.⁵ Findings from other studies of SSNHL and acute deafness suggest that hearing loss associated with MS will have spontaneous recovery, often with no permanent audiological deficits.³,⁷,⁸,¹²

The workup and management of hearing loss in the setting of MS mirrors that of hearing loss in the typical patient without MS. These patients should undergo an otoscopic evaluation. If the hearing loss is persistent despite management of cerumen impaction, acute otitis media, tympanic membrane perforation, or other immediately apparent causes of hearing loss, the patient should be referred for complete audiometric evaluation. Brainstem auditory evoked responses are not routinely assessed but have been reported as frequently abnormal in patients with MS, even when hearing loss is not a reported symptom.¹⁰,¹³,¹⁴ If hearing loss has been established with audiometric evaluation, magnetic resonance imaging (MRI) is the imaging modality of choice to identify lesions in the auditory brainstem7,9 and should be performed whether the hearing loss recovers or not.

When a patient presents with acute, unilateral sensorineural hearing loss associated with tinnitus and/or vertigo, and no prior history of audiological symptoms, as with all cases of sudden sensorineural hearing
loss, this constellation of symptoms is considered an otologic urgency and should be evaluated and treated. However, the differential for this constellation of symptoms remains broad, including diabetes mellitus, medication ototoxicity, Meniere disease, Susac syndrome, Wolfram syndrome, and autoimmune disease of the ear, among others.¹⁵

In the presence of concurrent facial nerve and vestibular deficits with audiogram-proven sensorineural hearing loss, MRI of the brain and internal auditory canals with gadolinium contrast should be pursued to rule out mass lesion. Although it requires a high index of suspicion, MS remains a consideration in the presence of multiple acute cranial neuropathies, and brainstem involvement has previously been reported as the presenting feature of MS in up to 15% of cases.⁸,¹⁶

The management of hearing loss in patients with known MS mirrors that of patients without MS. A complete audiometric evaluation will determine the patient’s candidacy and likelihood of benefitting from amplification with a hearing aide. Deafness is an uncommon symptom in MS, reported to be less than 3% in large series of this patient population.¹³ However, if profound sensorineural hearing loss is present, the patient may require cochlear implantation.

As previously mentioned, it is important to note that sudden sensorineural hearing loss is an otologic urgency. As such, a patient who has sudden-onset unilateral hearing loss with or without concurrent vertigo or tinnitus requires urgent evaluation with audiogram and treatment as warranted based on those results. For patients with known MS and a new-onset sudden unilateral sensorineural hearing loss, the limited data available on sudden sensorineural hearing loss in MS portend a relatively good prognosis. In one series of 11 patients with sudden sensorineural hearing loss, 5 of the subjects had spontaneous recovery before complete audiometric evaluation.⁵ Thus, any patient with sudden unilateral hearing loss should undergo an urgent complete audiometric evaluation, and if medically able, consideration should be given to treatment with 1 week of high-dose oral steroids followed by a steroid taper.¹⁷ If the patient cannot receive oral steroids, intratympanic steroid injection by an otolaryngologist should be considered.

Tinnitus has not been evaluated in large-scale series in the population with MS but has nonetheless been reported in the literature as a component of MS.
In light of the prevalence of hearing loss as a symptom of MS and the close clinical association between tinnitus and all causes of hearing loss, this does not come as a surprise. In a report of 12 patients with unilateral hearing loss and MS, 9 had tinnitus.¹³ However, it is notable that there have been isolated case reports in which tinnitus was a primary symptom at the time of initial presentation. One such case was in an 11-year-old who was found to have persistent unilateral nonpulsatile tinnitus and remitting hearing loss.¹⁸ Thus, a high index of suspicion should be maintained for any patient with persistent unilateral otologic symptoms.

The initial workup of both persistent bilateral and unilateral tinnitus in any patient should include complete audiometric evaluation. For persistent unilateral tinnitus, as in the case of any unilateral or elusive audiovestibular disorder, we further advocate for workup with an MRI of the internal auditory canals to rule out mass lesions or alternate diagnoses, even in the presence of a normal audiogram.¹⁹ In the case report referenced previously in this section, a complete audiometric evaluation demonstrated unilateral high-frequency sensorineural hearing loss and subsequent MRI was initially unremarkable owing to artifact from concurrent dental hardware. However, repeat imaging following removal of the hardware demonstrated multiple demyelinating lesions consistent with a diagnosis of MS.¹⁸

Of note, tinnitus is also a reported side effect of interferon-beta, which may be used in the treatment of MS. It has been reported in isolation or in conjunction with sensorineural hearing loss at cumulative doses greater than 100 MIU of interferon-beta.²⁰

In patients with known MS, new-onset tinnitus should prompt a complete audiometric evaluation to assess whether the tinnitus is occurring in isolation or in conjunction with hearing loss. If the patient is taking any ototoxic medications, consideration should be given to cessation of this medication if clinically able, particularly if the tinnitus is accompanied by true hearing loss, as this may be progressive and lead to permanent damage of the outer hair cells of the cochlea.

There is otherwise no special consideration in the management of tinnitus for the patient with MS. Management options parallel those that are available to patients without MS. When hearing loss is present, amplification with hearing aids may be beneficial in reducing the patient symptoms. Additionally, lifestyle and behavioral changes are helpful in the management of tinnitus, including optimization of sleep hygiene, limitation of caffeine intake, and white noise. However, it is important for any clinician to
note that tinnitus can be extremely disturbing for patients and has previously been associated with both depression and suicidality.²¹ For patients with severe, debilitating tinnitus, cognitive behavioral therapy has been shown to be efficacious in a systematic review of over 1000 patients.²²

Imbalance is a common presentation in MS that can result from either central or peripheral causes: affecting proprioceptive, visual, and/or vestibular pathways. The differential for vertigo is broad and includes benign paroxysmal positional vertigo (BPPV), vestibular migraine, labyrinthitis, or vestibular neuronitis. A thorough history regarding the frequency and duration of symptoms is critical, as well as the quality of symptoms themselves, to differentiate between symptoms that may be characterized as “dizziness” by a given patient. Frank vertigo (self or room spinning sensation) and disequilibrium may result from central lesions such as those seen in MS, masses of the internal auditory canal, or a vascular event of the posterior cerebral circulation, as well as peripheral vestibular issues such as vestibular neuronitis, labyrinthitis, Meniere disease, or BPPV. Syncope, or presyncopal symptoms, are more suggestive of neurocardiac etiologies, as a peripheral vestibular issue never causes these symptoms. Concurrent auditory symptoms, facial nerve symptoms, or other cranial neuropathies may be helpful in localizing symptoms and identifying the underlying etiology.²³

Vertigo is one of the more common otolaryngologic symptoms in MS with anywhere from 4% to 15% and 33% to 50% of patients experiencing vertigo at onset or after diagnosis, respectively.¹,¹⁵,²⁴ However, a study by Pula et al of a cohort of patients presenting with acute vestibular syndrome (AVS) found that only 4% of the subjects studied had AVS resulting from demyelinating disease.²⁵ Furthermore, multiple studies have suggested that vertiginous episodes in patients diagnosed with MS can often be attributed to peripheral causes of imbalance, such as BPPV.²⁶ If the vertiginous episode is provoked by head movement and is short in duration lasting seconds to minutes, it is likely to be of BPPV etiology. However, a more chronic presentation of vertigo lasting at least 24 hours that is associated with other brainstem findings is more suggestive of a brainstem lesion resulting from MS.²⁷,²⁸

Patients reporting vertigo should undergo a thorough clinical examination, including assessment of the extraocular movements for nystagmus, a full cranial nerve examination to screen for concurrent cranial neuropathies,
gait assessment, and Dix-Hallpike testing. The head thrust test is an additional bedside maneuver useful in assessing the vestibulo-ocular reflex. If the history of vertigo is unclear, consideration should be given to orthostatic blood pressure measurement.

For patients with vertigo, a complete audiometric evaluation is useful in the evaluation of subtle hearing deficits. There are a variety of options for thorough vestibular testing, including electronystagmography, vestibular evoked myogenic potential, and posturography, among others. Electronystagmography tests can be useful in differentiating and characterizing peripheral and central vestibular abnormalities and are thus potentially useful tests for guiding the diagnosis of patients presenting with vertigo.²⁹ Abnormal posturography scores have been identified in patients with MS with both high and low functional status.³⁰

The imaging modality of choice for the evaluation of vertigo and for the diagnosis of MS in this setting is MRI. Special attention to the internal auditory canal (IAC) is warranted to rule out a mass lesion of the IAC as causative of the patient’s symptoms. Vertigo in the patient with MS likely results from demyelinating lesions affecting the central vestibular pathways or associated fiber tracts in the lower pons and upper medulla.²⁴ In the study by Pula et al, of those patients whose AVS was determined to be caused by demyelinating disease, all but one patient was found to have at least one potentially causative posterior fossa lesion on MRI.²⁵