The size of the cerebellar hemisphere and vermal lobules was measured in ten autistic and eight normal control subjects at the Neuropsychology Research Laboratory, Children’s Hospital Research Center, and the Departments of Neurosciences and Radiology, School of Medicine, University of California at San Diego, LaJolla. On sagittal MRI’s the cerebellar hemispheres of the autistic subjects showed hypoplasia and a near total absence of the cerebellar tonsils in one. In contrast, a comparison of the average cerebellar width measured on axial images revealed no significant difference between the autistic group and the normal control group. The mean area of the superior-posterior vermis in the autistic subject group was 20% smaller than in the normal control group, while there was no significant difference between the mean anterior vermis areas of the two groups. The results indicated that the decreased size of the cerebellar hemispheres and the vermal lobules VI through VII was associated with autism. 
COMMENT. The results of this study confirm those of a previous study by the same authors that showed that hypoplasia of the superior-posterior vermis (lobules VI and VII) is frequently observed in autistic individuals. The nature of the link between cerebellar dysgenesis and autistic symptoms has not been determined. The authors refer to clinical and research observations indicating that the cerebellum also plays a role in a variety of cognitive functions, such as language, learning and memory, emotional behavior, and complex motivated behaviors. They believe that the hypoplasia of cerebellar hemispheres and vermis observed in many autistic individuals is linked with behavioral and cognitive symptoms.