THURSDAY, Nov. 29, 2012 (HealthDay News) -- Brain scans done on groups of men with autism show distinct differences in both the volume of specific regions and the activity of cells that signal a possible immune response, two new studies suggest.
Scientists in England and Japan used MRI and PET (positron emission tomography) scans to examine brain-based anatomical and cellular variations in those with autism. But the disparities -- while offering a deeper glimpse into the little-understood developmental disorder -- raised more questions about its cause and treatment that only further research can answer.
"There's really strong evidence now that the immune system appears to be playing a role in autism, but we just don't know what that role is," said Geraldine Dawson, chief science officer of Autism Speaks, who was not involved in either study. "There is such an urgent need for more research to understand the causes and more effective treatment for autism. Autism has really become a public health crisis, and we need to respond to this by greatly increasing the amount of research conducted so we can help families find answers."
The studies were published online in this week's issue of the journal Archives of General Psychiatry.
Affecting one in 88 children in the United States, autism is characterized by pervasive problems in social interaction and communication, as well as repetitive and restricted behavioral patterns and interests.
The Japanese study examined the brains of 20 men with autism using PET scans to focus on so-called microglia. These are cells that perform immune functions when the brain is exposed to "insults" such as trauma, infection or clots. The PET images indicated excessive activation of microglia in multiple brain regions among those with autism when compared to a group of people without the disorder.
"This really raised the question about what the role is of these abnormalities," said Dawson, who also is a professor of psychiatry at the University of North Carolina, in Chapel Hill. "Is this something that could help us explain the causes of autism? Is it a reaction to autism, or the brain's response to developing in an unusual way?"
"We don't have the answers to these questions, but now they're showing up in multiple studies so it does suggest that understanding the role of the immune system in autism may be an avenue to understanding its treatment," she added.
The British study used MRI on 84 men with autism and a matched set of healthy participants. It suggested that those with autism have marked differences in cortical volume. These differences may be linked to its two components -- cortical thickness and surface area. Overall, participants with autism had greater cortical thickness within the frontal lobe regions of the brain and reduced surface area in other regions of the brain.
Study author Christine Ecker, a lecturer in neuroimaging at King's College London, discussed such brain differences.
"We also know that about 50 percent of individuals with autism have an abnormally enlarged brain, particularly during early childhood, which suggests that those with autism have an atypical developmental trajectory of brain growth," Ecker said. "[Anatomical brain differences in these areas] are highly correlated with the severity of autistic symptoms, but we still need to establish how specific differences in surface area and cortical thickness affect wider autistic symptoms and traits."
Dawson, who wrote an editorial accompanying the studies, noted that the last decade has brought an explosion of new research into autism, although she still feels funding for this work is lacking from federal agencies.
"It's been amazing to see not only the number of new scientists that are beginning to devote their careers to autism research, but also the quality of scientists," Dawson said. "But despite the fact that we're excited and encouraged by the numbers of publications increasing, we still feel the progress is far too slow."
The U.S. National Library of Medicine has more about autism.