Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 2 1 2017 08 26 1 4 EN Mohammad reza Najafi Department of Neurology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. Roshanak Mehdipour-Dastjerdi Department of Neurology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. 2017 04 09 2017 07 03 Clinical presentation of demyelinating disorders is very heterogeneous, but initially isolated cranial nerve involvement, especially eighth nerve lesions, is extremely rare as the manifestation of clinically isolated syndrome (CIS) or multiple sclerosis (MS), so sudden sensory neural hearing loss (SNHL) is rarely a sole and presenting symptom of MS. A 31-year-old female presented with a history of left-sided ear fullness sensation and sudden hearing loss (without any history of trauma or infection); the pure-tone audiometry (PTA) showed unilateral SNHL pattern (high-frequency zone). The neurological and otolaryngologic examination was normal. Magnetic resonance imaging of the brain revealed several disseminated typical demyelinating plaques. The oligoclonal bands had been detected in the sample of cerebrospinal fluid. All of the routine laboratory data and serum autoantibodies were within normal ranges. Administration of high-dose corticosteroid improved her hearing. SNHL is a rare and atypical manifestation of CIS. Our case is assigned to be a high-risk CIS and may be developed to MS. It may be due to acute inflammatory demyelinating lesions of the cochlear nerve which could be a manifestation of CIS at first. https://crcp.tums.ac.ir/index.php/crcp/article/view/112 https://crcp.tums.ac.ir/index.php/crcp/article/download/112/64