2019 年 78 巻 3 号 p. 185-191
Syphilis is a sexually transmitted infection caused by the bacterium Treponema pallidum. Otosyphilis is a type of neurosyphilis; in otosyphilis, cochleovestibular dysfunction could be due to a lesion of the inner ear itself or of the eighth cranial nerve. In most cases, otosyphilis manifests as sensorineural hearing loss. We report a rare case of a 56-year-old male patient who developed vestibular symptoms, including dizziness and vertigo, caused by otosyphilis. The patient was admitted to our hospital with a 3-week history of dizziness and vertigo. He did not have deafness or tinnitus. All the serological tests for syphilis, including the T. pallidum hemagglutination assay (TPHA), the rapid plasma reagin test, and the fluorescent treponemal antibody absorption (FTA-ABS) test, were positive. Tests for HIV antibody were negative. The TPHA and FTA-ABS tests on the cerebrospinal fluid were also positive. On clinical neurological examination, the Romberg test was positive, and he had spontaneous nystagmus toward the left side and direction-changing positional nystagmus. Caloric tests revealed no response on the right side, indicating canal paresis. No cervical vestibular evoked myogenic potential (c-VEMP) response was observed on the right side. Based on the findings, the patient was diagnosed as having otosyphilis, and treated with penicillin G (24 million units/day) for 14 days. Two months after the treatment, the vestibular symptoms resolved and the abnormal nystagmus disappeared completely.