橋原発Medulloblastomaの1例

Medulloblastoma Originating in the Pons

I．はじめに

　橋発生のmedulloblastomaは稀といわれている．本邦の脳腫瘍統計ではmedulloblastomaのうち橋もしくは延髄発生のものは0.6％である^9）．世界的にみると，橋発生のmedulloblastomaに関する報告は渉猟し得た限りでは4例を一括してまとめている1報告だけである（組織診断はprimi-tive neuroectodermal tumor（PNET）であるが）^1）．本邦の発生率から推察すると，ある程度の報告例は期待されるのだが実際に症例報告されている例は殆どない．今回われわれは報告例が少ない稀な橋原発のmedulloblastomaを経験したので若干の文献的考察を加え，報告する．

Medulloblastoma usually originates in the cerebellum. We report here a case of medulloblastoma origi-nating in the pons. Pontine medulloblastoma is extremely rare, with only one report in the literature. An11-year-old girl was admitted to our hospital with vertigo. Magnetic resonance imaging (MRI) revealed atumor originating in the pons. On the 4th day after admission, the tumor bled. Because the patient's lifewas in danger from brain herniation, hematoma removal and tumor resection were carried out. The diagno-sis was medulloblastoma. After surgery, the patient received radiation therapy and chemotherapy. Unliketumors originating in the cerebellum, this tumor did not seem to be effectively reduced by these therapies.Radiation therapy and chemotherapy may not he effective for medulloblastoma originating in the pons. Weconsidered it necessary to make a histological diagnosis even though the tumor originated in the pons andresection was difficult technically.