Multiple sclerosis: a cause of sudden hearing loss

Management of Sudden Sensorineural Hearing Loss in Multiple Sclerosis: A Comprehensive Case Report of a Patient with Bilateral Loss and Literature Review

In multiple sclerosis (MS), the occurrence of sudden sensorineural hearing loss (SSNHL) is considered rare, with reported cases predominantly being unilateral. Bilateral cases are even rarer. Here, we report a case of bilateral SSNHL in a 20-year-old male diagnosed with MS. The patient, undergoing corticosteroid therapy for the management of MS, additionally received an intratympanic dexamethasone injection; however, it could not achieve significant improvement. Subsequently, the systemic dosage was increased for one week, resulting in substantial hearing improvement in both ears after three months. A review of MS-related SSNHL cases from 1987 to 2022 revealed 39 ears in the literature, with only five ears showing no hearing recovery. A remarkable 87.2% exhibited restored hearing, presenting a more favorable prognosis compared with idiopathic SSNHL. Although there were slight variations in administration methods and duration, all documented treatment approaches involve systemic corticosteroids. In some instances, SSNHL manifested as the initial symptom of MS. When SSNHL occurs in MS, auditory brainstem response (ABR) tests may reveal prolonged abnormalities, making ABR testing effective in cases where MS is suspected following SSNHL. In conclusion, the treatment of MS-related SSNHL appears appropriate with systemic corticosteroids, showing a significantly superior prognosis compared with idiopathic SSNHL.

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.

Auditory impairment in H-ABC tubulinopathy

Hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC) is a neurodegenerative disease due to mutations in TUBB4A. Patients suffer from extrapyramidal movements, spasticity, ataxia, and cognitive deficits. Magnetic resonance imaging features are hypomyelination and atrophy of the striatum and cerebellum. A correlation between the mutations and their cellular, tissue and organic effects is largely missing. The effects of these mutations on sensory functions have not been described so far. We have previously reported a rat carrying a TUBB4A (A302T) mutation and sharing most of the clinical and radiological signs with H-ABC patients. Here, for the first time, we did a comparative study of the hearing function in an H-ABC patient and in this mutant model. By analyzing hearing function, we found that there are no significant differences in the auditory brainstem response (ABR) thresholds between mutant rats and WT controls. Nevertheless, ABRs show longer latencies in central waves (II-IV) that in some cases disappear when compared to WT. The patient also shows abnormal AEPs presenting only Waves I and II. Distortion product of otoacoustic emissions and immunohistochemistry in the rat show that the peripheral hearing function and morphology of the organ of Corti are normal. We conclude that the tubulin mutation severely impairs the central hearing pathway most probably by progressive central white matter degeneration. Hearing function might be affected in a significant fraction of patients with H-ABC; therefore, screening for auditory function should be done on patients with tubulinopathies to evaluate hearing support therapies.

Audiovestibular Symptoms in Systemic Autoimmune Diseases

Immune-mediated inner ear disease can be primary, when the autoimmune response is against the inner ear, or secondary. The latter is characterized by the involvement of the ear in the presence of systemic autoimmune conditions. Sensorineural hearing loss is the most common audiovestibular symptom associated with systemic autoimmune diseases, although conductive hearing impairment may also be present. Hearing loss may present in a sudden, slowly, rapidly progressive or fluctuating form, and is mostly bilateral and asymmetric. Hearing loss shows a good response to corticosteroid therapy that may lead to near-complete hearing restoration. Vestibular symptoms, tinnitus, and aural fullness can be found in patients with systemic autoimmune diseases; they often mimic primary inner ear disorders such as Menière's disease and mainly affect both ears simultaneously. Awareness of inner ear involvement in systemic autoimmune diseases is essential for the good response shown to appropriate treatment. However, it is often misdiagnosed due to variable clinical presentation, limited knowledge, sparse evidence, and lack of specific diagnostic tests. The aim of this review is to analyse available evidence, often only reported in the form of case reports due to the rarity of some of these conditions, of the different clinical presentations of audiological and vestibular symptoms in systemic autoimmune diseases.

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.

Hearing disorders in multiple sclerosis

Multiple sclerosis (MS) is a disease that is both a focal inflammatory and a chronic neurodegenerative disease. The focal inflammatory component is characterized by destruction of central nervous system myelin, including the spinal cord; as such it can impair any central neural system, including the auditory system. While on the one hand auditory complaints in MS patients are rare compared to other senses, such as vision and proprioception, on the other hand auditory tests of precise neural timing are never "silent." Whenever focal MS lesions are detected involving the pontine auditory pathway, auditory tests requiring precise neural timing are always abnormal, while auditory functions not requiring such precise timing are often normal. Azimuth sound localization is accomplished by comparing the timing and loudness of the sound at the two ears. Hence tests of azimuth sound localization must obligatorily involve the central nervous system and particularly the brainstem. Whenever a focal lesion was localized to the pontine auditory pathway, timing tests were always abnormal, but loudness tests were not. Moreover, a timing test that included only high-frequency sounds was very often abnormal, even when there was no detectable focal MS lesion involving the pontine auditory pathway. This test may be a marker for the chronic neurodegenerative aspect of MS, and, as such could be used to complement the magnetic resonance imaging scan in monitoring the neurodegenerative aspect of MS. Studies of MS brainstem lesion location and auditory function have led to advances in understanding how the human brain processes sound. The brain processes binaural sounds independently for time and level in a two-stage process. The first stage is at the level of the superior olivary complex (SOC) and the second at a level rostral to the SOC.

[Idiopathic sudden deafness]

PURPOSE

Sudden idiopathic deafness is a sensorineural hearing loss with no recognized causes at the time of onset. The impairment site is usually localized in the cochlea, but some cases of retrocochlear lesions (e.g., cerebellopontine angle tumors, degenerative neural diseases, neuraxial ischemic lesions) can induce sensorineural deafness. The medical management of patients presenting with sudden deafness aims at detecting a causal mechanism, and at administering emergency therapeutic drugs. The diagnosis of idiopathic sudden deafness can be definitely made when no causes are found. Usually, the impairing mechanism involves the cochlea. The pathophysiology of this sensorineural alteration is still unknown. It is most likely that several mechanisms are associated together, their common point being an impairment to the feedback loop of the organ of Corti.

CURRENT KNOWLEDGE AND KEY POINTS

It is very likely that reactivation of neurotropic viruses and/or cochlear ischemia are frequent etiologies. Whatever the cause, the treatment is to be administered urgently, and consists of a high-dose corticotherapy at the least. Other treatments have never really proven to be effective. It is secondarily checked that no retrocochlear pathological processes, such as a cerebellopontine angle tumor, is present, in particular in young people.

FUTURE PROSPECTS AND PROJECTS

One of the current objectives is to determine when cochlear ischemia is involved, in a mini-invasive manner, such as with laser Doppler flowmetry, so that the treatment can be optimized. From a therapeutic point of view, early acoustic protection has been proven to be effective in cases of cochlear ischemia in small laboratory animals. Its efficacy in case of sudden deafness, non-exclusive of other causes than ischemia, is being assessed in a multicentric project.