The neuropathological literature and the prospects for future research in the genetics and pathology of autism are outlined in an inclusive review article from the University Medical Center Utrecht, The Netherlands. Increased head circumference, brain weight and brain volume in children with autism are well documented. The limbic system shows increased cell packing density and smaller neuronal size in 9 of 14 autism cases reported; the cerebellum shows a decreased number of Purkinje cells in 21 of 29 cases studied, and the cerebral cortex has features of dysgenesis. Small sample size, inconsistent findings, and comorbid conditions, including mental retardation in 70% and epilepsy in 40%, diminish the significance of the reports in regard to the pathogenesis of autism. Future neuropathological studies should include larger sample sizes, younger subjects free of comorbidities, and new techniques such as stereology, that permits precise measurement of number, size and spatial distribution of cells, and the study of gene expression, to uncover the molecular and cellular basis of the neuropathology of autism. [1]

COMMENT. Autism is a neurodevelopmental, genetically determined, disorder characterized by impairments in social interaction and communication skills, cognitive rigidity, abnormal language development, and repetitive, stereotypical behaviors. The prevalence of autistic spectrum disorders (ASD) in studies published before 1985 was 4-5 per 10,000 children. After 1990, the prevalence began to rise to as high as 50-70 per 10,000 in the USA [2]. Causative factors proposed for the apparent increase in prevalence of ASD have included more inclusive definitions, improved recognition of the symptoms, greater parental concern, and possible epigenetic factors and modifications of gene expression. The theory that the measles-mumps-rubella (MMR) vaccine and thimerosol were responsible for the apparent increased prevalence of autism has largely been put to rest [3, 4]. ASD has a strong genetic basis, and a specific medical cause or environmental trigger is found in only 6-10% of cases, eg. prenatal insult, metabolic and toxic disorders, tuberous sclerosis, and postnatal encephalitis (Ped Neur Briefs October 2003;17:79-80) [5]. The study of the etiology of autism is multifaceted, and future research will involve pediatric neurologist, psychiatrist, pathologist, and geneticist.

Oculomotor studies in autism. Pursuit eye movement deficits were observed in a study of 60 high-functioning autistic young adults compared to 94 normal control subjects, at the University of Illinois, Chicago [6]. The authors conclude that their findings are consistent with reduced functional connectivity within the visual pursuit system caused by abnormalities in brain maturation in autism.