Progressive focal deficit with porencephaly.

The association of porencephalic cysts with hydrocephalus was first cited in 1939. Subsequent descriptions of this combination in terms of fixed, nonprogressive neurological problems have been reported. We describe four patients with hydrocephalus who had progressive focal motor deficits secondary to porencephalic diverticulation of the lateral ventricle. Symptoms of increased intracranial pressure were not a consistent finding in all patients. Enlargement of the porencephalic cyst is related to either a generalized increase in intraventricular pressure or to "hydrostatic" forces that may act independently. Computerized axial tomography has provided a noninvasive technique that allows definition of the abnormality and its progression. Neurosurgical intervention has resulted in clinical improvement in all patients studied.