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Brain Morphometry and Psychobehavioural Measures in Autistic Low-Functioning Subjects

In the last two decades neurological research has significantly increased knowledge on the neuroanatomic bases of autism. Several autopsy and quantitative magnetic resonance imaging (MRI) studies have reported central nervous system (CNS) abnormalities which may underlie the social, language and cognitive dysfunction typical of the autistic disorder.

Despite the wealth of evidence that the “autistic brain” is different from normal in a number of structures, the relationship between the severity of the developmental impairment in autism and the degree of the brain abnormality remains unknown.

The aim of the present study is to correlate the areas of some brain regions, as calculated on the basis of MRI morphometry, with the Childhood Autism Rating Scale (CARS) and with the Psychoeducational Profile Revised (PEP-R) scores in a group of 22 autistic mentally retarded male subjects.

Quantitative magnetic resonance image analysis of the cerebellum in macrocephalic and normocephalic children and adults with autism

A detailed morphometric analysis of the cerebellum in autism with and without macrocephaly. Four subject groups (N = 65; male; IQs > or = 65; age 7 to 26 years) were studied with quantitative MRI; normocephalic and macrocephalic individuals with autism without mental retardation were compared to normocephalic and benign macrocephalic typically developing individuals. Total cerebellum volumes and surface areas of four lobular midsagittal groups were measured. Independent t-tests between autism and control subjects matched for head size revealed no significant differences. Multivariate analyses of variance were also performed, using the diagnostic group as the fixed factor, cerebellar measures as the dependent variables and total intracranial volume, total brain volume, age, verbal IQ, and performance IQ as covariates. No significant differences were found; however, a trend was noted in which macrocephalic individuals with autism consistently exhibited slightly smaller cerebellar volume or surface area when compared to individuals with benign macrocephaly. In autism, with and without macrocephaly, cerebellar structures were found to be proportional to head size and did not differ from typically developing subjects.

Neuroimaging in disorders of social and emotional functioning: what is the question?

Social and emotional processing uses neural systems involving structures ranging from the brain stem to the associational cortex. Neuroimaging research has attempted to identify abnormalities in components of these systems that would underlie the behavioral abnormalities seen in disorders of social and emotional processing, notably autism spectrum disorders, the focus of this review. However, the findings have been variable. The most replicated anatomic finding (a tendency toward large brains) is not modular, and metabolic imaging and functional imaging (although showing substantial atypicality in activation) are not consistent regarding specific anatomic sites. Moreover, autism spectrum disorder demonstrates substantial heterogeneity on multiple levels. Here evidence is marshaled from a review of neuroimaging data to support the claim that abnormalities in social and emotional processing on the autism spectrum are a consequence of systems disruptions in which the behaviors are a final common pathway and the focal findings can be variable, downstream of other pathogenetic mechanisms, and downstream of more pervasive abnormalities.

Clinical correlates of brain morphometric features of subjects with low-functioning autistic disorder

Numerous neuropathologic and imaging studies have reported different structural abnormalities in the brains of autistic subjects. However, whether or not the degree of brain abnormality is correlated with the severity of developmental impairment in autistic disorder is still unknown. The midsagittal area of the cerebrum, corpus callosum, midbrain, cerebellar vermis, and vermal lobules VI and VII was measured by means of magnetic resonance imaging in 22 boys with low-functioning autistic disorder and in 11 age-matched normal controls. Morphometric measures were statistically compared between groups and correlated with age and scores on the Psychoeducational Profile-Revised and the Childhood Autism Rating Scale. A significant negative correlation was found between midsagittal area of the cerebrum and age in patients with autistic disorder, and a positive correlation was found between the midsagittal area of the midbrain and some subscales of the Psychoeducational Profile-Revised.