Previously published cerebellar vermis measures of 78 autistic patients from 4 separate MRI studies have been reanalysed at the Neurosciences Department, School of Medicine, University of California at San Diego, La Jolla, CA. Abnormalities were in 2 groups: vermal hypoplasia in 80-90% and vermal hyperplasia in 8-16% patients. These subgroups also differed significantly from normal controls. Failure to recognize these variations in vermal structure among patients may have lead to disparate reports of cerebellar maldevelopment in infantile autism. 
COMMENT. Cerebellar pathology and hypoplasia have been reported in Rett and Down syndromes as well as autism. Attentional asynergia and dysfunction following cerebellar damage are linked to impaired social communication skills. Cerebellar mutism and personality changes have followed surgical removal of medulloblastoma. (Ped Neur Briefs Feb 1992;6:15-16). The finding of subtypes of neuroanatomic changes supports the belief that autism is a heterogeneous disorder.