Human cerebellar hypoplasia: a syndrome of diverse causes.

Seven children had congenitally small cerebella. Perinatal asphyxia was not a factor. Clinical signs in infancy were generalized muscular hypotonia, delayed development, truncal titubation, and intention tremor. Most had fixation nystagmus and esotropia. Three had seizures and an abnormal EEG. Pneumoencephalography in each case revealed a small cerebellum with prominent folia, large fourth ventricle, wide vallecula, large cisterna magna, and normal lateral and third ventricles. A computerized tomography scan in one case showed similar findings. One patient had an absent corpus callosum. One patient died at 2 1/2 years. The cerebellar hemispheres and vermis were small. Granular cells were absent throughout. Purkinje's cells were preserved, but had dendritic swellings with radiating fibrils. Cerebellar, pontine, and inferior olivary nuclei showed mild neuronal loss. The clinical and pathologic findings resemble those of animal models of cerebellar hypoplasia produced by fetal exposure to certain viruses, toxins, or repeated low doses of radiation. Cerebellar hypoplasia is a clinical syndrome of several causes, but with many symptoms and signs in common.