Central nervous system involvement in Leber congenital amaurosis

Sixteen patients with ocular criteria of Leber congenital amaurosis (LCA) were studied. Neurological examination was normal in 11 of 16 patients. The electroencephalogram was normal in six of eight patients, while two had nonspecific theta slowing. Computerized tomography of the brain was normal in two of five; hypoplasia of the cerebellar vermis was seen in one, and mild to moderate ventriculomegaly was seen in two of five. Six patients underwent the verbal subtests of the Wechsler Intelligence Scale and a detailed battery of neuropsychological tests. Subtests dependent on early environmental influences were most severely affected, while culture-free subtests showed average or well above average performance. These results strongly support the hypothesis that children with LCA may be capable of normal cognitive functioning, although they perform poorly on standard IQ tests. This is related to their early environmental and sensory deprivation, rather than to a primary central nervous system dysfunction.