前庭水管拡大症候群の2症例

Large Vestibular Aqueduct Syndrome:A Report of Two Cases

　はじめに

　近年の画像診断学の進歩に伴い，以前には原因不明の感音難聴とされてきた患者の中に前庭水管の拡大をみる症例の存在が明らかになってきた。これらの症例は，その画像所見とともにそれぞれの臨床像が前庭水管拡大症候群（large vestibularaqueduct syndrome）として報告されている^1）。今回，われわれは本症候群の2症例を経験したので，その臨床像と画像所見との比較検討し，本症候群の病態に考察を加えて報告する。

Two patients with large vestibular aqueduct syn-drome (LVAS) were reported. A 11-year-old female developed a sudden hearing impairment in the right ear. She did not complain vertigo. Pure tone audiometry showed a profound sensorineural hearing loss in the right ear more than in the left ear. CT and MRI studies revealed enlargement of the vestibular aqueduct and endolymphatic sac bilaterally, indicating a larger change in the right ear than in the left ear. Despite the treatment with intravenous steroid hormone injection for 16 days,hearing level did not recover. Caloric test showed normal responses in bilateral ears.

The second case was a 22-year-old female with the chief complaint of vertigo. She had a severe deafness since her infancy. A pure-tone audiometry revealed a profound sensorineural hearing loss in both ears. CT and MRI studies demonstrated bilate-ral symmetrical enlargement of the vestibular aque-duct and endolymphatic sac. Normal responses were observed bilaterally in caloric test.

From the experiences in above two cases, we emphasize that CT and MRI are useful to diagnose LVAS in the patients who complained of severe hearing impairment from the infancy, and that the enlarged vestibular aqueduct and endolymphatic sac may relate to the degree of hearing loss.