結節性硬化症の徴候を呈さない上衣下巨細胞性星細胞腫

Solitary Subependymal Giant Cell Astrocytoma : A Forme Fruste of Tuberous Sclerosis Complex?

　要旨　上衣下巨細胞性星細胞腫（subependymal giant cell astrocytoma：SEGA）の多くは結節性硬化症（tuberous sclerosis：TS）に伴って発生するが，稀に孤発例の報告もある。本症例における画像所見はSEGAに特徴的なものであったが，明らかなTSの徴候を示さず術前診断に苦慮した症例であった。

　古典的にTSの診断はVogtの3徴（てんかん，顔面の血管線維腫，知能障害）の存在が重要視されてきたが，近年，多くの不全型の存在が認識されている。1998年にRoachらが提唱した診断基準では，本例はpossible TS complexに相当する。厳密な確定診断は遺伝子解析に委ねられるが，TS徴候の有無にかかわらずMonro孔近傍の脳室内腫瘍の鑑別疾患においてはSEGAは念頭に置くべき疾患である。

　Subependymal giant cell astrocytoma（SEGA） is usually associated with tuberous sclerosis（TS） and believed to originate from subependymal nodules. We report a rare case of SEGA in a patient lacking symptoms of TS. Radiological findings, including CT and MRI, were characteristic of SEGA, but the preoperative diagnosis was difficult due to the fact that no other features of TS were present. TS has been classically characterized by the clinical presence of Vogt's triad of seizure, facial angiofibroma and mental retardation, however, few cases present with all of these manifestations. In 1998, Roarch et al. proposed new clinical diagnostic criteria for the TS complex based on the clinical and radiographic features of TS. According to these criteria, our case is classified as a “possible” TS complex. There have been previous reports of SEGAs without any obvious features of TS, but it is still controversial as to whether these reports represent a forme fruste of TS. To determine a strict diagnosis of SEGA, additional genetic studies are needed.

　The possibility of SEGA should be considered whenever an intraventricular tumor near the foramen of Monro is found, regardless of other clinical features of TS.

（Received : February 24, 2004）