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 Neural anomalies

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.[22

Magnetic resonance imaging !M"I# studies have suggested evidence for differences in

neuroanatomy and connectivity in people with autism compared with normal controls.

$pecifically, 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.

Importantly, some of the regional differences in neuroanatomy correlate significantly with the

severity of specific autistic symptoms.[2%, 2& 'or example, social and language deficits of peoplewith autism likely are related to dysfunction of the frontal and temporal lobes.[2(

In a study of postmortem brain tissue from )) children with autism and )) unaffected controls,

researchers found focal disruption of cortical laminar architecture in the cortexes of )* of the

children with autism and ) of the controls, suggesting that brain irregularities in autism may have

 prenatal origins. +he patches of abnormal neurons were found in the frontal and temporal lobes,

regions involved in social, emotional, communication, and language functions. $ince the changes

were in the form of patches, the researchers believe that early treatment could rewire the brain

and improve $- symptoms.[2, 2/

0n M"I scans, the brains of children with autism spectrum disorder demonstrate greater

myelination in bilateral medial frontal cortices and less myelination in the left temporoparietal

 1unction.[2 $imilarly, region3specific 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.[24

5ostmortem specimens of the brains of people with autism demonstrated reductions for gamma3

aminobutyric acid67 !877# receptors in the cingulate cortex, a key region for the evaluation

of social relationships, emotions, and cognition, and in the fusiform gyrus, a crucial region to

evaluate faces and facial expressions.[%* +hese findings provide the basis for further investigation

of autism and other pervasive developmental disorders.

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Metabolic anomalies

In animal studies, dysfunction of serotonin and the neuropeptides oxytocin and vasopressin has been associated with abnormalities in affiliative behaviors. 9europhysiologic dysfunction

involving ) or more of these substances may also be present in humans with autism

Elevations of blood serotonin levels occur in approximately one third of individuals

with autistic disorder and are also reported in the parents and siblings of patients.

Functional anomalies in other neurotransmitters (eg, acetylcholine, glutamate) have

also been identied in some people with autism spectrum disorder. [!, "#$

%erum biotinidase is reduced in some people with autistic disorder. &his en'yme is

reuired for the use and recycling of the vitamin biotin. *eciency of biotin has

been lin+ed with behavioral disorders.

mmunologic studies have identied abnormalities such as decreased plasma

concentrations of the - complement protein. %uch abnormalities may be the

source of the increased susceptibility to infection seen in some people with autism.

*iet is a controversial aspect of autism. &he greatest attention has been given to

gluten/ and casein/free diets0 anecdotal information suggests that these diets help

some children with autism.["$ &est ndings suggest that low/functioning children

with autism may have impairment in the metabolism of phenolic amines.[""$

 &herefore, symptoms of autistic disorder are possibly aggravated by the

consumption of dairy products, chocolates, corn, sugar, apples, and bananas0

however, no large population studies have conrmed this.

1xidative stress may play a role in the pathogenesis and the pathophysiology of

autism.["$ -ompared with normal children, children with autism have decrements in

the following["$ 2

• 3lasma levels of cysteine, glutathione, and methionine

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•  &he ratio of S /adenosyl/4/methionine (%56) to S /adenosyl/4/homocysteine

(%57)

•  &he ratio of reduced to oxidi'ed glutathione

%ome children with autism display hyperlacticacidemia["!$ as well as evidence of

mitochondrial disorders["!$

including carnitine deciency.["8$

 &hese abnormalities mayre9ect disturbed neuronal energy metabolism.