Central Nervous System Impairment (developed by Veronique Bure)

 Autism seems to stem primarily from abnormalities in brain structure or activity.   Those abnormalities could be caused by a genetic susceptibility , which expression is probably, in part, triggered by environmental factors.

Sophisticated technologies (like Magnetic Resonance Imaging) have allowed researchers to associate autism with a perception and connection disorder.  It seems that brains of children with autism are wired differently which shape their specific perception of the environment, and impair their response to it.  

Dysfunction is affecting many regions of the brain: 

• The left hemisphere is showing more abnormalities in structure and activity than the right hemisphere.  The left hemisphere is involved in the processing of language and motor planning, two areas of development affected in subjects with autism.  The right hemisphere is involved in visual spatial processing and music skills which can account for the visual processing capacities and the responsiveness to music most children with autism display.

• The cerebellum appears to be affected in its activity. As compared to control group, in children with autism there is evidence of a reduced activity during tasks that encompass expressive communication. This low activity level could also   account for some deficits in manual coordination and motor learning.

• The temporal lobes show a difference in activity in an area called the fusiform gyrus. It is activated in non autistic children in response to the human face. This region is not active in children with autism when presented with pictures of faces, except in some cases, when the children are shown their mother ‘ s pictures.

• Apraxia, dyspraxia, perseverative behaviors, delusional thinking, mood changes are thought to be linked with atypical activity and neuronal structure in the frontal lobe.

• Children with autism spectrum disorder display abnormal inter hemispheric communication. The variation of interactions derives from an abnormally high density of connections rather than from a lack of them (study of Just and Colleague, 2004).  There are wider neuronal circuits but they seem less efficient. This could account for deficient motor and sensory motor integration skills.

• Brain volume is larger in boys from 2-4 years old than in the non autistic counterparts.  It seems than the head of infants are smaller than normal and shows a sudden and excessive growth in size in between the age of 2 to 4 years old.  It is predominantly an excess in white matter growth.  This acceleration in neuronal growth often coincides with the onset of behavioral symptoms. Studies show also an increase in the stacks of neurons known as mini columns which might result in an excess of stimulation

• A high percentage of children with ASD, 30-70%, have abnormal Electro Encephalogram (EEG).  EEG spikes are clinically evidenced. It is thought that early spike treatment may prevent further clinical epilepsy through lifespan.  A steroid, Prednisome has shown promising results in reducing the spikes and in some cases has been associated with behavioral improvements in one of the following areas:  sleep pattern, speech, social awareness.

 It is clear that autism crosses class and ethnic boundaries.  It is strongly determined by heredity. If parents have one child with autism the chance to have a second autistic child is 2 to 8 percent which is 100 times the general risk.   The risk is higher when the first diagnosed child is a girl.

Finding the involved genes is not an easy task as they seem to be located on many different chromosomes.  Most people with autism, lacking the necessary social skills required to initiate  and maintain a relationship, do not have children. This does not facilitate the study of the hereditary mechanisms of the disorder.  

In 70% of the cases it is associated with mental retardation ranging from mild to severe.