123 0361-803X/94/1621-0123 © American Roentgen Ray Society Abnormality of Cerebellar Vermian Lobules VI and VII in Patients with Infantile Autism: Identification of Hypoplastic and Hyperplastic Subgroups with MR Imaging Eric ,2 Osamu Saitoh 1-3 Rachel Yeung-Courchesne2 GaryA. Press4 Alan J. Lincoln2 Richard H. Haas1 Laura Schreibman5 Received June 1 4, 1 993; accepted after revision September 2, 1993. This work was supported by National institute of Neurological Diseases and Stroke grant 5-AOl -NS 19855 and National Institute of Mental Health 1- R01-MH-36840. 1 Neurosciences Department, School of Mcdi- cine, University of California at San Diego, La Jolla, CA 92093. 2Neunopsychology Research Laboratory, Chil- dren’s Hospital, 3020 Children’s Way, San Diego, CA 92123. Address correspondence to E. Courchesne. 3National Center Hospital for Mental, Nervous and Muscular Disorders, National Center of Neurol- ogy and Psychiatry, 4-1 -1 Ogawa Higashi-Cho, Ko- daira, Tokyo, 187 Japan. 4Department of Radiology, Kaiser Penmanente Hospital, 4647 Zion Ave., San Diego, CA 92120. 5Department of Psychology, University of Cali- fornia at San Diego, La Jolla, CA 92093. OBJECTIVE. Infantile autism is a neurobehavioral disorder that is widely believed to have etiologically distinct subtypes, including subtypes with a genetic basis, but no neuroanatomic evidence firmly supports this belief. To date, only one type of cere- bellar abnormality has been Identified In patients with autism: hypoplasia of the ver- mis and hemispheres. By using a large sample of autistic patients and healthy volunteers along with precise MR Imaging and quantitative procedures, we sought to replicate previous reports of cerebellar vermian hypoplasla In autism and to identify additional subtypes of cerebeilar abnormality. MATERIALS AND METHODS. Using MR technology, we imaged and measured pos- tenor and anterior vermian regions in 50 autistic patients (2-40 years old) and 53 healthy control subjects (3-37 years old). The autistic patients had social, language, cognitive, behavioral, and medical history characteristics that were typical of the gen- eral autistic population. By using precise procedures for positioning and aligning MR slices, we obtained comparable MR Images within and across subject groups. RESULTS. Statistical analyses showed two subgroups of autistic patients, one (86% of the patients) with findings consistent with vermian hypoplasia and another (i2% of the patients) with evidence of vermian hyperplasia. The hypoplasia subgroup included 43 patients whose mean midsagittal area for vermian lobules VI and VII was 237 ± 38 mm2, and the hyperplasia subgroup included six patients whose mean area was 377 ± 12 mm2. Thus, the area of lobules VI and VII in the hypoplasia subgroup was 16% smaller than the mean area in the control subjects (282 ± 42 mm2) (p < .0001), whereas that in the hyper- plasia subgroup was 34% larger (p < .0001). Analyses showed that these two subtypes of vermian abnormalities were present across all ages of autistic patients studied. CONCLUSION. Two different subtypes of autistic patients can be identified on the basis of the presence of vermian hypoplasia or hyperplasia as seen on MR images. Possible origins for vermian hypoplasia include environmental trauma and genetic factors. AJR 1994;162:123-i30 Infantile autism is a neunologic disorder of unknown cause that severely dis- mupts social, cognitive, and language development [1]. Qualitative MR studies have shown decreased volume of the panietal lobe in 43% of autistic patients examined, and electrophysiological and behavioral studies show abnormalities in these patients that are consistent with MR findings [2-4]; whether other autistic patients have pamietal abnormalities remains unknown. Quantitative MA studies have shown hypoplasia of cerebellar vemmian lobules VI and VII and cerebellar hemispheres in the majority, but not all, of autistic patients examined [5-10]; whether other autistic patients have some other type of cemebellar abnormality is unknown. To date, the only neurobiological abnormality known to precede the onset of autistic signs and symptoms is loss of cerebellar neurons, which is most severe in lobules Vl-Vll and VIll-X in the posterior part of the vemmis (50-60% Purkinje cell loss) and hemispheres (42-56% Purkinje cell loss) [ii-14; E. Ann, personal communication, February 1993], and undoubtedly leads to the cerebellar hypoplasia quantified by MR imaging [5-10]. Downloaded from www.ajronline.org by 54.162.69.248 on 06/03/20 from IP address 54.162.69.248. Copyright ARRS. For personal use only; all rights reserved