特異な画像所見を呈した脳幹部星状細胞腫の1例

A Case of Pontine Astrocytoma with Unusual Neuroimaging Features

Ⅰ．はじめに

　脳幹部神経膠腫は全脳腫瘍の2.4％を占め，そのほとんどが小児期に発症する．15歳以下の小児に限れば，原発性脳腫瘍のうちで約20％に上り，全脳腫瘍中最も治療困難な腫瘍である．また，特徴的な画像所見に乏しく，診断の際には脳神経症状が重要であることが多い．腫瘍の進展形式や，画像所見と生命予後との相関関係については以前から報告されている^4,12)．今回，われわれは神経脱落症状を呈さず，水頭症で発症し特異な画像所見を呈した星状細胞腫の稀な1例を経験したので，若干の文献的考察を加え報告する．

　We would like to report a rare case of pontine glioma with unusual neuroimaging features. The patient was a 3-year-old girl who suffered from chronic nausea and gait disturbance for several months. Computed tomography (CT) demonstrated ventricular dilatation, and ventricular peritoneal (VP) shunt was performed for idiopathic hydrocephalus at another hospital. Fever of unknown origin continued for a month after the VP shunt. At our hospital, cerebrospinal fluid examination showed bacterial meningitis, and it was assumed that shunt infection lead to shunt failure. Magnetic resonance imaging (MRI) revealed hydrocephalus and pontine swelling, and serial MRI suggested brainstem tumor extending to the bilateral thalamus. The patient underwent stereotactic biopsy of the left thalamic tumor, under general anesthesia, and the histological diagnosis was anaplastic astrocytoma. Diffuse pontine glioma rarely increases without cranial nerve deficits. In the present case, pontine glioma extended to the bilateral thalamus symmetrically. It was difficult to diagnose the presented lesion as pontine glioma in the early period because of its unusual neuroimaging.