Cranial computed tomography (CT) or magnetic resonance imaging (MRI), or both, of 143 patients with West syndrome were retrospectively reviewed. Twenty-four children had normal CT scans. The most striking findings on pathologic scans were cerebral atrophy, ventricular enlargement, and encephalomalacia. Of 78 children who underwent MRI, 14 had normal scans. Cerebral malformations, cerebral atrophy, and delayed myelination were the most common pathologic findings and were observed in 25, 20, and 16 of the cases, respectively. MRI was found to be more informative in 21 of the 27 patients who underwent both neuroimaging methods. In fact, in two patients with normal CT scans, MRI revealed delayed myelination and hyperintensity of the hippocampal area on T-2-weighted images in one and increased intensity of basal ganglia on T-1-weighted images in the other. On the basis of all data, four patients were classified as cryptogenic and 126 as symptomatic. The most frequent etiologic factors were perinatal asphyxia, cerebral malformations, and infections, encountered in 34, 25, and 24 of the children, respectively. Twenty-one cases could be classified solely on the basis of the data obtained with neuroimaging modalities. The data confirm and provide additional details of the ways in which neuroimaging, especially MRI, is useful in distinguishing between cryptogenic and symptomatic cases of West syndrome. (C) 1998 by Elsevier Science Inc. All rights reserved.