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

Abstract

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 conditions and 1 h 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.Conclusions: 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.