Development of progressive hearing loss and tinnitus in a patient with myasthenia gravis: an overlooked comorbidity?

PURPOSE: There is evidence of progressive antibody-mediated loss of acetylcholine receptors on outer hair cells in the inner ear that underlies hearing dysfunction in myasthenia gravis patients. In this paper, we present the case of a 35-year old patient with adult-onset myasthenia gravis and thymoma who experienced progressive hearing loss and bilateral high-pitched tone tinnitus worsening over time. MATERIALS AND METHODS: Patient underwent Pure Tone audiometry, Acoustic Immittance test, Decay test, Transient-Evoked and Distortion Product Otoacustic Emissions with and without Contralateral Acoustic Stimulation, somatosensory tinnitus screening maneuvers, and self-assessment questionnaires for tinnitus, hearing loss and hyperacusis, in addition to anamnestic interview and complete ENT visit. Questionnaires for psychiatric comorbidities (SCL90R - Symptom Checklist 90 Revisited) were also administered to the patient. The patient was studied in baseline condition and 1h after administration of the acetylcholinesterase inhibitor pyridostigmine bromide, a drug that has been reported to have a temporary effect on outer hair cell electromotility in myasthenia gravis patients. RESULTS: Pure-tone audiometry showed a progressive hearing loss for high frequencies. Consistently, Transient-evoked and Distortion Product Otoacoustic Emission amplitudes were significantly reduced for mid and, especially, high frequencies; after drug administration, a significant otoacoustic emission amplitude increase was recorded. CONCLUSION: Our findings documented a chronic dysfunction of outer hair cells consistent with acetylcholine receptor loss; these alterations could represent a basis for development of hearing loss and tinnitus.