Acute hemiplegia and cortical blindness due to moya moya disease: report of a case in a child with Down's syndrome.

We are reporting what we believe to be the first case of moya moya disease (hemiplegia associated with supraclinoid carotid stenosis and multiple cerebral telangiectasia) in a child with Down's syndrome. On cerebral angiography, multiple collateral vessels and rete mirabile (anastomosis of meningeal vessels with internal cerebral vessels) were noted, in addition to the supraclinoid carotid stenosis. Computerized tomography revealed nonobstructive hydrocephalus and findings consistent with multiple vascular insults or infarcts. It is not clear whether moya moya disease represents a true disease entity (congenital arterial dysplasia) or is a syndrome caused by nonspecific vascular reaction. Since abnormal vascular morphology has previously been described in children with trisomy 21, we suggest that the presence of these two disease entities may not be coincidental. It may represent a genetic predisposition in Down's syndrome toward vascular abnormalities, with variable expressivity which manifested itself in this case by abnormalities in the cerebral circulation.