強い健忘症で発症した松果体部Germinomaの1例

Pineal Germinoma Presenting with Severe Amnesia

I．はじめに

　松果体部腫瘍の初発症状としては，閉塞性水頭症による頭蓋内圧亢進症状あるいは眼球運動異常が殆んどで^3,12,15）記銘力障害を初発症状とすることは極めて稀である^5,13）．われわれは頭蓋内圧亢進症状や眼球運動障害を伴うことなく，強い健忘症を初発症状とした松果体部germinomaの1例を経験したので報告する．

Patients who have a pineal germinoma usually pre-sent with symptoms of intracranial hypertension or dis-turbances in vertical ocular motion but rarely present with amnesia.

We recently encountered a case of pineal germinoma accompanied by severe amnesia, but not by hy-drocephalus. A 32-year-old, right-handed man was admit-ted with severe memory disturbance which had gra-dually worsened in the preceding three months. On admission, he was alert and cooperative. His speech was well preserved and not fabricated. He had neither symptoms of intracranial hypertension or visual dis-turbance. There was no manifestation of interhemi-spheric disconnection symptoms. His immediate and semantic memory was preserved, however, his recent and antegrade episodic memory was severely impaired. The amnesia involved both verbal and visual modali-ties. He could recall only 1 out of 5 objects in 5 mi-nutes. He was orientated to people, but not to time and place. And his motivation was severely affected. Magnetic resonance imaging (MRI) showed a hetero-geneously enhanced tumor in the splenium and pineal body that extended into the bilateral ventricular trigon through major forceps and was accompanied by edema in the retrosplenial region. The bilateral crura of the fornix was obscured by the tumor. The enlarged pineal body was slightly compressing the upper colliculus but hydrocephalus was not observed.

The tumor, which was partially excised through a right parietal corticotomy, had features typical of a ger-minoma. Adjuvant local irradiation administered with a linear accelerator to a total dose of 50Gy resulted in complete disappearance of the tumor, which has not re-curred for three years, but the amnestic state has con-tinued. Post treatment MRI showed low signal intensity in the splenium and retrosplenial cortex on T1 weight-ed images and severe atrophy of the bilateral fornices. The MRI and the neuropsychological characteristics strongly suggested that bilateral damages to the fornix and retosplenial region caused our patient's severe amnesia. This damage was brought about by unusual transsplenial extension of pineal germinoma.