Magnetic resonance imaging of the brain structures in the posterior fossa in retarded autistic children.

Midsagittal magnetic resonance images of the brains of retarded autistic children were compared to those of non-autistic mental retardation patients and controls. We found that the whole brain stem and particularly two of its components (the midbrain and medulla oblongata) were significantly smaller in retarded autistic children and mental retardation cases than in control children. The pons area was significantly smaller in mental retardation cases as compared to control children but did not differ between autistic and control children. Moreover, there was no difference in the brain stem between retarded autistic children and mental retardation cases. We also noted no difference in the cerebellar vermis area among retarded autistic children, mental retardation cases and control children. The ratio of the midbrain to posterior fossa area was significantly smaller only in autistic patients. Although the significance of these results is unknown, further examination of autistic children with a normal IQ is necessary.