Brain inflammation may play an important role in the development of autism (search), according to a new report published in the Annals of Neurology.

Carlos A. Pardo, MD, of Johns Hopkins University said in a press release that the findings reinforce the theory that inflammation in the brain is involved in autism, although it is not yet clear whether it is destructive or beneficial or both. Inflammation occurs when the immune system is activated, causing cells to rush into the area and produce swelling.

Despite all the marvels of modern medicine, the autistic brain is still highly uncharted territory. Doctors have struggled to determine the cause of autism since Leo Kanner, MD, first defined it in the 1940s, but the exact reasoning has remained elusive.

Autism is a complex neurological and development disorder that affects about 1 in 500 children. The disorder has become increasingly more common in recent years, although many researchers feel that improvements in diagnosis may account for this increase. It is estimated that as many as 1.5 million American children and adults have autism.

People with autism may repeat words or phrases continuously, have difficulty expressing their thoughts and feelings, are resistant to change, and may display aggressive or even self-injurious behavior.

In the study, researchers analyzed frozen brain tissue from 11 deceased autism patients aged 5 to 44 and found that inflammation is clearly a feature of the disease in certain regions of the brain. Compared with normal brains, the autistic brains showed evidence of active inflammation in various regions, although it was most prominent in the cerebellum.

They also found ongoing inflammation in the fluid surrounding the brain and spinal cord. And they found cytokines, or potent chemical messengers that are secreted by the immune system and lead to inflammation.

Scientists say their findings open up “new possibilities for understanding the dynamic changes that occur” in autistic brains. They speculate they could lead to new treatments and, potentially, specific diagnostic tests that look for inflammation in the spinal fluid of autistic patients. There is currently no blood or lab test to check for the disease.

By Kelli Miller Stacy, reviewed by Brunilda Nazario, MD

SOURCES: Vargas, Diana L., Annals of Neurology, January 2005, vol 57.Autism Society of America. News release, Wiley Research.