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 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.