精神運動発作にて発症した成人の右側頭葉Pilocytic Astrocytomaの1例

A Case of Adult Pilocytic Astrocytoma in the Right Temporal Lobe

I．はじめに

　pilocytic astrocytomaは小児の小脳半球，視神経に発生することが多く，時に脳幹，第III脳室周囲組織にも見られるが大脳半球に発生することは稀である．今回精神運動発作で発症した右側頭葉のpilocytic astrocytomaの1例を経験したので若干の文献的考察を加え報告する．

Abstract

A case of adult pilocytic astrocytoma in the right temporal lobe is reported here.

The patient was a twenty-four year old man, who came to the neurological division of our hospital on October 6, 1987 because of repeated consciousness-loss attacks accompanied with uncinate fit. He had no neu-rological deficits. However, an EEG revealed spike-and-wave complexes in the right temporal region, and a CT scan showed a small cystic lesion in the right temporal lobe. A diagnosis of psychomotor seizure was made, and the administration of anticonvulsants was started.The incidence of attack then decreased, but after approximately two years of drug therapy the attacks increased again. A CT scan was again performed, and revealed that the lesion in the right temporal lobe was enlarging. Also a noticeable enhanced lesion, identified as a mural nodule was found in the post-contrast en-hancement study. A brain tumor was then suspected, and he was admitted to the neurosurgical division on October 11, 1989.

He had no neurological deficits on admission. An MRI showed a low intensity lesion in the T1 weighted image, and a high intensity lesion in the T2 weighted image. A cystic lesion with a marked enhanced mural nodule was also found in the base of the right temporal lobe, according to the Gd enhancement study. Perifocal edema was not recognized. Cerebral angiography showed no positive findings. Positron emission tomography (PET) , using H₂¹⁵O, revealed low perfu-sion at or around the lesion, and PET using [¹¹C] -methionine revealed an accumulation of methionine at the lesion.

A diagnosis of low-grade glioma was made, and a right temporal craniotomy, for the purpose of totally re-moving the tumor was performed on October 26, 1989. The tumor was found in the subcortical region at the base of the right temporal lobe, just above the pyramid- al bone. A yellowish discoloration of the cortical sur-face was recognized. The tumor had a small cyst con-taining yellowish fluid, and a mural nodule of 1cm in diameter. The mural nodule was soft and grayish white. We completely removed the mural nodule and the cyst wall.

A histopathological investigation revealed that the tumor was pilocytic astrocytoma, and showed a few Rosenthal fibers and granular bodies.

Pilocytic astrocytoma is often seen in either the optic nerve or the cerebellum in children, but rarely seen in the adult cerebral hemisphere. According to the pub-lished literature, the incidence of lobar pilocytic astrocytoma is less than 1% of all brain tumors, and only 1% - 2% of all supratentorial gliomas. Some au-thors, however, have said that they are more frequent in children than in adults. Also, according to the litera-ture, the characteristics of lobar pilocytic astrocytoma are as follows : 1) The tumors are often seen in the temporal lobe of children or young adults, 2) cystic tumors are frequently found with a mural nodule, 3) the most frequent initial symptoms are epilepsy, or signs of increased intracranial pressure, 4) the prognosis is generally good, but only if the tumor is not deep seat ed, is not solid, and if total removal is possible. Radio-therapy and chemotherapy are both considered un-necessary as follow-up therapies. Our case is considered a typical case of lobar pilocytic astrocytoma of adult.