What is the role of neural anomalies in the pathophysiology of autism spectrum disorder (ASD)?

Updated: Sep 30, 2019
  • Author: James Robert Brasic, MD, MPH; Chief Editor: Caroly Pataki, MD  more...
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Answer

In patients with autism, neuroanatomic and neuroimaging studies reveal abnormalities of cellular configurations in several regions of the brain, including the frontal and temporal lobes and the cerebellum. Enlargements of the amygdala and the hippocampus are common in childhood. Markedly more neurons are present in select divisions of the prefrontal cortex of autopsy specimens of some children with autism, compared with those without autism. [26]

Magnetic resonance imaging (MRI) studies have suggested evidence for differences in neuroanatomy and connectivity in people with autism compared with normal controls. Specifically, these studies have found reduced or atypical connectivity in frontal brain regions, as well as thinning of the corpus callosum in children and adults with autism and related conditions.

In a study that included 17 adults with high-functioning autism and 17 age- and IQ-matched control subjects, functional magnetic resonance imaging (fMRI) of the brain that showed neural representations of social interactions was able to accurately identify individuals with autism. Scans were performed as study subjects thought about a set of social interaction verbs from both an action and a recipient perspective. [27, 28]

Importantly, some of the regional differences in neuroanatomy correlate significantly with the severity of specific autistic symptoms. [29, 30] For example, social and language deficits of people with autism likely are related to dysfunction of the frontal and temporal lobes. [31]

In a study of postmortem brain tissue from 11 children with autism and 11 unaffected controls, researchers found focal disruption of cortical laminar architecture in the cortexes of 10 of the children with autism and 1 of the controls, suggesting that brain irregularities in autism may have prenatal origins. The patches of abnormal neurons were found in the frontal and temporal lobes, regions involved in social, emotional, communication, and language functions. Since the changes were in the form of patches, the researchers believe that early treatment could rewire the brain and improve ASD symptoms. [32, 33]

On MRI scans, the brains of children with autism spectrum disorder demonstrate greater myelination in bilateral medial frontal cortices and less myelination in the left temporoparietal junction. [34] Similarly, region-specific differences in the concentrations of gray matter, made up of neuronal cell bodies, dendrites, unmyelinated axons and glial cells, are also found in the brains of people with autism. [35]


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