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Tumors at the trigone of the lateral ventricles are relatively rare. The authors have operated on eight cases with trigonal tumors during a 10-year period. Four cases were true intraventricular tumors arising from the ventricular walls, consisting of two meningiomas, one cavernous angioma, and one choroid plexus papilloma. On the other hand, the remaining four cases were paraventricular tumors originating in the adjacent brain and consisted of three astrocytomas and one glioblastoma multiforme. Although these trigonal tumors were readily detected with computed tomographic (CT) scanning, differential diagnosis was difficult because of their similar appearances on CT scans. The initial symptoms were headache in seven, and the neurological examination revealed personality changes, choked disc, visual field defects, hemiparesis, etc., in four, and no deficits in the remaining four cases. All cases were operated on via superior or middle temporal gyrus incision, and the surgical results were good except for one case who died of postoperative brain edema. In the four cases with tumors located in the dominant hemisphere, two were left with sensory aphasia, dyslexia, dyscalculia, and hemianopsia which improved within 6 months. In these two cases, postoperative CT scans revealed cerebrospinal fluid retention with severe edema along the surgical route which disappeared spontaneously within 3 months. We consider that the temporal gyrus incision was the safest approach, even though the tumor was located in the dominant side.

Subependymal giant-cell astrocytoma (SGCA), a rare intraventricular tumor, occurs mainly in young patients in conjunction with tuberous sclerosis (TS). This tumor arises characteristically from the medial part of the floor of the lateral ventricle, occluding the foramen of Monro. This report presents a rare adult case of SGCA, not associated with TS, which arose from the trigone of the lateral ventricle. The patient, a 42-year-old male, was admitted with episodes of psychomotor seizure for the past 2 years. The seizures consisted of hot sensations in his throat while breathing and of amnesic attacks. Electroencephalography showed occasional spike discharges localized in the right temporooccipital region. Computed tomography revealed the presence of an ovoid high density mass in the right trigone of the lateral ventricle with intense contrast enhancement. Surgery revealed a dark red, highly vascularized soft friable tumor. Light microscopic examination of the tumor characteristically showed cells of 3 morphological types, i.e. swollen gemistocytic cells, ganglion-like cells, and elongated and spindle-shaped cells. Mitoses and endothelial proliferations were extremely infrequent. Immunoreactive glial fibrillary acidic protein was present in the cytoplasm and processes of some smaller cells. Phosphotungstic-acid haematoxylin-positive fibrils were present in the perinuclear region of the spindle-shaped cells. Nissl's substances were seen at the margin of the cytoplasm of the ganglion-like giant cells.