第4脳室外に発生した脈絡叢乳頭腫の1例

Adult Choroid Plexus Papilloma of the Posterior Fossa ： Extraventricular Location

Ⅰ．はじめに

　脈絡叢乳頭腫（choroid plexus papilloma, CPP）は比較的稀な神経外胚葉性腫瘍であり，脳室内脈絡組織から発生する．全脳腫瘍の0.4～0.5％を占め^16,17)，成人では後頭蓋窩にみられ，第4脳室内に発生するものがほとんどである¹⁸⁾．稀に第4脳室外に大きく発育することがあり，この場合術前診断が困難である^{1,2,7,8,10,12,13,15,18-21)}．術前診断に難渋した第4脳室外に発育したCPPの成人例を経験したので，文献的考察とともに報告する．

Choroid plexus papillomas (CPPs) are rare neuroectodermal neoplasms accounting for 0.4％ of all intracranial neoplasms in adults. Most of them are located in the posterior fossa in adults. Although CPPs commonly arise from the 4th ventricle,they occasionally extend to extraventricular space. Furthermore some occur primarily in the extraventricular region. It is difficult to diagnose CPP preoperatively when the main portion of the tumor is not located in the 4th ventricle. We present a case of a 54-year-old male manifesting slurred speech,nystagmus and cerebellar ataxia. Magnetic resonance imaging demonstrated an intracerebellar solid tumor with multilocular cysts,extending towards both the right lateral medullary region and the foramen of Luschka. Computed tomography scans showed patchy calcification at the periphery of the solid component. Angiographically,via the right posterior inferior cerebellar artery revealed the tumor was faintly opacified. Preoperative diagnosis included meningiomas,low-grade astrocytomas,ependymomas or CPPs,but none of them had neuroradiologically decisive findings. Tumor was subtotally resected through a right suboccipital craniectomy. A calcified solid portion adhering to the lower cranial nerves was left unresected. The pathological finding was CPP. CPP should be considered among calcified and enhanced masses in the lateral medullary to cerebellopontine angle space in adults,even if the main portion of the tumor is not located in the 4th ventricle.