Neuropathology of autism

There are numerous reviews of the cellular neuropathology of autism (Bauman and Kemper, 1994, 2005 Kemper and Bauman, 1998 Bailey et al., 1998 Palman et al 2004 Casanova, 2007 Amaral et al., 2008). In this chapter I will discuss the relationship of the various pathologies to developmental events, a subject not covered in detail in these reviews. Emphasis will be placed on the timing and mechanisms of the known pathologies and their possible relationship to the well-documented abnormal pattern of brain growth seen in autistic individuals. 

Pickett J, London E (2005) The Neuropathology of autism a review. J Neuropathol Exp Neurol 64 925-935. 

Kemper T. Bauman ML.(1993) The contribution of neuropathologic studies to the understanding of autism. In Behavioral Neurology, volume 11 (Brumback RA, ed), pp. 175-187. Philadelphia W B Saunders. 

Kemper TL, Bauman ML (1998) Neuropathology of infantile autism. J Neuropathol Exp Neurol... 

Autism Neuropathology, Alterations of the GA-BAergic System, and Animal Models... 

The following section explores the five areas most consistently found to be abnormal in postmortem studies of autistic brains - amygdala, septal nucleus, hippocampus, anterior cingulate cortex, and cerebellum - and discusses their hypothetical relationship to emotional and interpersonal psychopathology in autism. Note that other brain areas, which are inconsistently abnormal in neuropathological studies, may express inconsistent associated symptoms, variations in psychopathological subtypes, or inconsequential anomalies and are not discussed in this section. 

Darby JK (1976) Neuropathologic aspects of psychosis in childhood. J Autism Childhood Schizophr 6 339-352. 

Martchek M, Thevarkunnel S, Bauman M, Blatt G, Kemper T (2006) Lack of evidence of neuropathology in the locus coeruleus in autism. Acta Neuropathologica 111 497-499. 

This chapter correlates emotions and attachment behavior in autism with the disturbed neuroanatomy found in the brains of these individuals. Neuropathological postmortem studies have consistently found abnormalities in the limbic system and the cerebellum of autistic individuals. Abnormal limbic structures include the amygdala, hippocampus, septal nucleus, and anterior cingulate cortex. In the cerebellum, abnormalities have been found in the cerebellar hemispheres and in the fastigial, emboliform, and globose nuclei. 

Neuropathological studies in autistic brains have also demonstrated smaller neuronal size and increased cell packing density in the hippocampus, another limbic system structure. The morphology of hippocampal neurons in two cases of infantile autism was studied and investigators found smaller cells with reduced perikaryon area and dendritic branching in comparison with neurons of age-matched control children [63], This result is consonant with MRI results evidencing a smaller area dentata of the hippocampus in autistic children from 2 to 4 years [64]. However, the density and distribution of some 5-HT receptors in the hippocampus were not statistically different between autistic children and controls [65]. 

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