Brain MR imaging in children with developmental retardation of unknown cause: results in 76 cases.

Seventy-six children with developmental retardation of unknown cause underwent MR imaging of the brain. Twenty-one (28%) had positive MR findings, including nine with atrophy, six with delayed myelination, four with multiple focal white matter lesions, three with hypoplastic white matter, and three with migration abnormalities. The frequency of abnormality was highest in nonautistic children with associated neurologic physical findings (61%) but was also significant in nonautistic children without neurologic findings (23%). We did not detect abnormalities on MR images of autistic retarded children. Delayed myelination and migration abnormalities were the predominant abnormalities in children with associated neurologic findings, whereas focal white matter lesions were more common in children without neurologic findings. Abnormalities were significantly more common in children with a small head circumference. Although MR did not have any effect on treatment or prognosis, it did aid the clinician in family counseling. MR will reveal brain abnormalities in about one third of nonautistic children with developmental retardation of unknown cause, and more often in those with neurologic deficits, seizures, or a small head size.