不衛生な口腔内環境が原因と考えられたFusobacterium nucleatumによる小脳膿瘍の1症例

A Case of Cerebellum Abscess due to Fusobacterium nucleatum that Developed Because of Poor Dental Hygiene

Ⅰ．はじめに

　Fusobacterium属はグラム陰性嫌気性桿菌で，口腔内などに存在する常在菌であり¹⁰⁾，なかでもFusobacterium necrophorum（F. necrophorum）とFusobacterium nucleatum（F. nucleatum）が重篤な感染症を引き起こす菌種として報告されている^3,8)．今回われわれは，不衛生な口腔内環境が原因と考えられたF. nucleatumによる小脳膿瘍の1症例を経験したので報告する．

　We report a case of cerebellum abscess due to Fusobacterium nucleatum（F. nucleatum） in a 60-year-old man. He was admitted to our hospital complaining of headache and dizziness. On admission, he was lucid with the following vital data:blood pressure, 136/89 mmHg;heart rate, 65 beats/min;body temperature, 37.0℃;and oxygen saturation, 100%. He had a moderate headache and could not walk straight. In general, there were no abnormal findings except for his poor dental hygiene. Laboratory findings revealed elevated white blood cell counts（10,900/mm³）and brain MRI revealed a mass shadow that was suspected to be an abscess in the left side of his cerebellum. Elective surgery was scheduled. However, consciousness of disorder was observed on the second hospital day and the size of mass shadow extended;hence, emergent drainage under craniotomy was performed. The diagnosis was cerebellum abscess, and F. nucleatum, which is a normal flora in the oral cavity, was isolated in his cerebellum abscess. After the surgery, his hospital course was positive under the treatment of antibiotics for F. nucleatum. The route of bacterial infection entry was unclear;however, it will be considered that abscesses in the central nervous system occur because of poor dental hygiene.