MIZOI, K., YOSHIMOTO, T. and SUZUKI, J. Clinical Analysis of Ten Cases with Surgically Treated Brain Stem Cavernous Angiomas. Tohoku J. Exp. Med., 1992, 166 (2), 259-267-Ten cases of surgically treated brain stem cavernous angiomas are reported in this paper, and their clinical and radiological features are reported. There were 9 males and 1 female with ages ranging from 9 to 69 years (average 36 years). Four of the cavernous angiomas were located in the dorsal pons, two in the middle cerebellar peduncle, two in the hypothalamus, and one each in the cerebral peduncle and the superior colliculus. All the ten patients came to medical attention because of the sudden onset of neurological abnormalities following brain stem hemorrhage. Six of the 10 patients showed neurological deterioration due to rebleeding at various intervals ranging from 10 days to 2 years. After intravenous injection of iodinated contrast materials, negative contrast enhancement was commonly seen. In a few cases, there was faint enhancement of the nodule at the periphery of the hematoma. Serial computed tomography (CT) scans over a period revealed an unchanged hyperdense mass lesion, which was thought to be a most characteristic and indicative CT feature of the cavernous angioma. On magnetic rersonance imaging (MRI), the combination of a mixed signal intensity with a surrounding rim of decreased signal intensity (hemosiderin rim) suggested the presence of a cavernous angioma. Enhanced MRI, using gadopentate dimeglumine, was thought to be more sensitive than contrast enhanced CT in detecting cavernous angiomas. All these cases underwent surgery with good results. Abnormal vascular tissue in the wall of the hematoma cavity was recognized at operation and pathological confirmation was obtained in all cases. These data indicate that brain stem cavernous angiomas can be surgically removed with acceptable morbidity.