前庭機能評価を行ったムンプス難聴の2症例

抄録

　Mumps virus infection may cause acute sensorineural hearing loss, usually unilateral. It is sometimes accompanied by dizziness, and the vestibular dysfunction caused by mumps virus infection has not yet been well documented. We encountered two cases of mumps virus-induced hearing loss with vertigo, and conducted a series of vestibular function tests.

　Case 1, a 47-year-old man, presented with fever and bilateral subaural swelling. Two days later, he complained of left-sided hearing loss. Then, on day 7, he developed vertigo. Examination revealed total deafness on the left side. Serology revealed a positive result for anti-mumps IgM antibody, indicating that he did not have prior mumps infection or vaccination.

　Case 2, a 25-year-old man, presented with bilateral tinnitus and subaural swelling. On day 3, he visited our hospital, and audiometry showed total deafness on the right side. On day 6, he developed vertigo. Serology revealed a positive result for anti-mumps IgM antibody.

　We performed an infrared nystagmus test, caloric test, cervical and ocular Vestibular Evoked Myogenic Potential (VEMP), and video-Head Impulse Test (vHIT) in both cases.

　Both cases showed Canal Paresis (CP) on the affected side (Case 1, 94.5%; Case 2, 71.9%). vHIT showed decreased Vestibulo-Ocular Reflex (VOR) gain and Catch Up Saccade (CUS) in the affected semicircular canal in both. VEMP showed no response of c-VEMP on the affected side in Case 1, and no bilateral differences in either c-VEMP or o-VEMP in Case 2. The symptoms of vertigo disappeared about one month after the onset, but the findings of right CP on vHIT persisted, and in fact, became worse in Case 2.