Multiple sclerosis (MS) can affect other cranial nerves apart from optic nerve. We report an interesting case of Balo's concentric sclerosis (BCS) that presented with sensorineural hearing loss (SNHL).

BCS is a rare variant of MS. It derives its name from the concentric pattern of demyelination alternating with preserved myelin seen on magnetic resonance imaging (MRI). It typically has a fulminant monophasic clinical course with a fatal outcome although there has been an increasing number of cases reported with a benign clinical course.

48-year-old presented to our neuro-immunology clinic for evaluation of abnormal MRI which revealed non-enhancing T2 hyperintensities in juxta-cortical, peri-ventricular and infratentorial cerebellar lesions concerning for demyelination. He had tinnitus and SNHL of right ear ongoing for 3-4 months prior to presentation. Extensive workup was pursued to rule out MS mimics including nutritional, autoimmune, and infectious etiologies. LP revealed no evidence of oligoclonal bands. He was originally diagnosed with radiologically isolated syndrome with plans to monitor with MRI brain annually for surveillance. Repeat MRI brain a year later revealed new non-enhancing concentric juxta-cortical lesion along the right frontal operculum exhibiting a laminated appearance with surrounding perilesional edema consistent with BCS. He had no new neurological symptoms in the interim. On re-evaluation, his auditory symptoms were deemed as a clinical event, and he was diagnosed with MS with subsequent initiation of disease modifying therapy.  

BCS may occur simultaneously with MS like lesions or may herald the onset of MS. SNHL is a rare manifestation of MS with demyelinating lesion along the course of vestibulocochlear nerve or nucleus in brain stem. MRI brain can fail to reveal signs of demyelination either due to timing of MRI brain from symptom onset or sub-optimal diagnostic accuracy as vestibular evoked myogenic potentials have detected demyelinating lesions which are invisible on MRI brain.