Hearing Loss in Neuromyelitis Optica Spectrum Disorder: Case Report and Systematic Review

Background: Sudden, non-traumatic hearing loss has been associated with vascular or inflammatory disorders. Hearing loss in Neuromyelitis optica spectrum disorder (NMOSD) is a very rare presentation. Methods: In this paper, we describe the case of a 58-year-old female patient with aquaporin-4-positive NMOSD exhibiting bilateral tinnitus and right-sided deafness in the context of a relapse. The auditory brainstem responses pointed to a lesion of the right peripheral auditory pathway (cochlea and/or auditory nerve). The patient's hearing failed to improve after high-dose intravenous steroids; however, it showed slight improvement after plasmapheresis. We also conducted a systematic literature review in databases MEDLINE and Scopus in English, searching for all reported cases of hearing loss in NMOSD. Results: We included 10 studies reporting 15 cases of NMOSD with hearing loss. The vast majority of patients were female (11 out of 15, 73.3%), with an age range of 26 to 70 years. Hearing loss, ranging from mild to severe, seems more frequent in AQP4-positive cases, and it can even be the presenting symptom. It can present isolated or in combination with tinnitus, ataxia, and/or intractable vomiting. The auditory pathway impairment in NMOSD seems to be localized either centrally, i.e., cochlear nuclei or higher brainstem levels, or peripherally, i.e., in the cochlea or cochlear nerve itself. Intravenous methylprednisolone in high doses, followed by oral tapering, was the most common treatment option, resulting in a gradual improvement. Conclusions: This paper describes a rare case of peripheral auditory pathway affection in NMOSD, which is an inflammatory astrocytopathy mainly affecting the central nervous system. Early recognition of hearing loss in the context of an NMOSD relapse and subsequent treatment have a crucial impact on the hearing outcome of NMOSD patients. This expands our knowledge of NMOSD as an autoimmune aquaporin-4 channelopathy.