Abnormal Brain Connections Linked to AutismResearchers believe they have uncovered evidence of disorganized brain connections among people with autism spectrum disorders (ASDs).

Investigators used a new form of brain imaging technology to provide visual evidence associating autism with disordered brain connections, including defects in nerve conduction.

The problem in signal conduction stems from flaws in myelin — the fatty, insulating coating that helps nerve fibers conduct signals and that makes up the brain’s white matter.

Researchers say that genetic and cell studies provided clues that suggested abnormalities in how brain cells (neurons) connect to each other influence the development of ASDs.

The investigators used advanced magnetic resonance imaging (MRI) to image the brains of 40 patients (infants to age 25) with tuberous sclerosis complex and 29 age-matched, healthy controls.

Tuberous sclerosis is a rare genetic condition often associated with cognitive and behavioral deficits, including ASDs about 50 percent of the time.

“Patients with tuberous sclerosis can be diagnosed at birth or potentially before birth, because of cardiac tumors that are visible on ultrasound, giving us the opportunity to understand the circuitry of the brain at an early age,” explains Mustafa Sahin, M.D., Ph.D. from Children’s Hospital Boston and a co-author of the study.

“Our ultimate goal is to use imaging in infancy to find which tuberous sclerosis patients are at high risk for autism so we can intervene early. This may have implications for autism in patients without tuberous sclerosis as well.”

The team used a relatively new MRI technique called diffusion tensor imaging to trace the pathways of nerve fibers by measuring the diffusion of water in the brain.

Researchers followed 40 patients with tuberous sclerosis; 24 had clinically significant developmental delays or intellectual disability, and 12 had ASDs. ASDs were diagnosed clinically by a pediatric neurologist, and, in most cases, by the Autism Diagnostic Observation Schedule (ADOS).

In general, compared with controls, patients with tuberous sclerosis had findings consistent with abnormalities in the white matter (which is partly made up of myelin). Patients with both tuberous sclerosis and ASDs had both disorganized nerve pathways and nerve conduction problems.

The images showed that axons (nerves) in the control subjects followed well-defined directions in organized bundles, while the ASD patients’ axons tended not to orient together in common directions.

Tuberous sclerosis patients without ASDs showed only slight disorganization compared to controls.

“This study shows that we can use diffusion tensor imaging to differentiate tuberous patients with autism from those without autism,” said Sahin.

“Our advances in imaging and in image analysis are enabling us to identify and quantitatively characterize alterations in brain development that are not readily visible in conventional imaging,” said Warfield.

“Ultimately, imaging will play a crucial role in identifying who may benefit from treatment, and in seeing the changes in the brain in response to treatment.”

Source: Children’s Hospital Boston

neuron pathways photo by shutterstock.