Intradural retroclival chordomaの1例

A Case of Intradural Retroclival Chordoma

Ⅰ．はじめに

　脊索腫（chordoma）は胎生期の脊索の遺残から発生する稀な腫瘍であり，脊索の存在した頭蓋底から仙骨までに発生する^3,4,6-8)．頭蓋底では鞍背から斜台，大後頭孔に好発すると言われている．一般的に脊索腫は骨内部から発生し，骨を破壊して発育する硬膜外病変であることが多いが，今回われわれは硬膜下を主座とし，斜台と連続性をもたないintradural retroclival chordomaの1例を経験したので，文献的考察を加えて報告する．

　A 67-year-old woman was referred to our department with a retroclival lesion including a cyst on MRI. MRI revealed a lesion appearing as an isointense region on a diffusion-weighted image（DWI). Gadolinium（Gd）-DTPA T1-WI showed heterogeneous enhancement of the lesion in the prepontine cistern. Computed tomography（CT）revealed an isodense lesion with no invasion into the clival bone. Based on a preoperative diagnosis of retroclival chordoma, extended trans-sphenoidal surgery（TSS）was performed by a direct endoscopic endonasal approach via the left nostril. We found a round dural defect with a diameter of 5 mm, through which the tumor was incarcerated. However, the tumor had no connection to the clival bone. The lesion was totally removed and histologically diagnosed as a chordoma. Furthermore, the clival bone included no tumor cells. Based on those radiological and histological findings, we diagnosed the lesion as an intradural retroclival chordoma.

We should consider intradural retroclival chordoma as a candidate for the differential diagnosis of a retroclival lesion without clival bone invasion.