Intracranial ruptured aneurysm accompanying moyamoya phenomenon.

Three cases of moyamoya phenomenon associated with an aneurysm in the periphery of a lateral ventricle presenting with intracranial haemorrhage are reported. In case 1 the aneurysm was located in the right basal ganglia, and the patient improved under conservative management. The aneurysm had increased in size on the second angiogram, and disappeared on the third angiogram obtained nine months after the attack. In Case 2 the aneurysm was located in the peripheral portion of the left posterior cerebral artery, and was surgically excised. Pathological examination on surgical material revealed collagenous tissue and laminae only in part of the aneurysmal wall. In Case 3 the aneurysm was located in the peripheral portion of the right anterior choroidal artery. This patient died, and the autopsy revealed an angiomatous lesion in the choroid plexus of the right lateral ventricle, but the aneurysm itself could not be identified. These findings indicate that an aneurysm has formed in a portion of a weakened vascular group represented by an abnormally dilated collateral pathway, and that the most likely reason for this would be haemodynamic stress.