Magnetic resonance imaging and clinical features of 16 children with agenesis of the corpus callosum (ACC) are reviewed at UAE University, United Arab Emirates. Three groups of patients were recognized: Group 1). 8 patients without involvement of other brain areas, 3 having lipomas, or interhemispheric cyst, 3 with partial ACC, 5 with Probst bundles (aberrant longitudinal fiber bundles on medial hemispheral walls), and 4 with epilepsy; Group 2). 4 patients with ACC complicated by severe telencephalic dysgenesis (periventricular heterotopia, microcephaly with cortical dysplasia, microlissencephaly and cerebellar hypoplasia, diffuse agyria-pachygyria and pontocerebellar dysplasia), absent Probst bundles, and developmental delay and epilepsy in 3; Group 3). 4 children with ACC as part of a syndrome: 1 with Aicardi syndrome, 2 with L1 disease and mutations in the L1CAM gene, and 1 with Mowat-Wilson syndrome with mutation in the zinc finger homeo box 1B (ZFHX1B) gene; all 4 had severe developmental delay and mental retardation and 1 had infantile spasms. Severe handicaps, developmental delay, mental retardation, and neurologic deficit occurred in patients of groups 2 and 3. Two of the 8 patients in group 1 were developmentally delayed, mentally retarded, and had neurologic deficits. Parental consanguinity was present in 7 of the 16 patients, and genetic factors are involved in ACC cases associated with various syndromes. 
COMMENT. MRI is important in the evaluation of developmental delay or epilepsy. ACC is also recognized on prenatal ultrasound after the 20th week. Dobyns describes true types and secondary types of ACC . Those associated with major malformations or degeneration are considered secondary.