Sudden hearing loss as the initial symptom in Japanese patients with multiple sclerosis and seropositive neuromyelitis optica spectrum disorders.

Sudden hearing loss may occur in rare cases of relapsing-remitting multiple sclerosis (RRMS). There have also been reports of idiopathic sudden sensorineural hearing loss (SNHL) in patients with neuromyelitis optica spectrum disorders (NMOSD), but the frequency of such cases is unclear. We conducted a retrospective analysis of the medical records of 173 consecutive patients with multiple sclerosis (MS) and 101 consecutive patients with NMOSD who tested positive for anti-aquaporin-4 antibodies in addition to 37 consecutive patients with clinically isolated syndromes (CIS) to investigate the frequency and onset timing of SNHL. SNHL was observed in six (3.5%) of the RRMS cases, one (1.0%) of the seropositive NMOSD cases, and three (8.1%) of the CIS cases. SNHL occurred ahead of onset in 4/6 MS patients and in all of 3 CIS patients. Patient with NMOSD exhibited SNHL 6years after the onset of NMOSD. Although SNHL is rare, these results suggest the risk of developing demyelinating lesions in the central nervous system and further conversion to MS in the future.