The study included 26 children with tuberous sclerosis complex (TSC), a genetic disorder that causes benign lesions or tumors to form in many different organs, including the brain where the lesions are called "tubers." Autism is a common occurrence in children with TSC.
Researchers used MRI and PET exams to study how the brain lesions resulted in common behaviors of autism including difficulties in social interaction and communication, and narrow and repetitive stereotyped behavior. "We wanted to know if where the tuber was located or what it was 'doing' in the brain could predict behaviors of autism," said Diane C. Chugani, PhD, a researcher at the PET Center at Children's Hospital of Michigan, Detroit, Michigan. "We found that in these children, autism results from a complex combination of events in different parts of the brain, rather than from one single source."
For example, Chugani said the study showed biochemical abnormalities in the brain's outer layer (the cortex) had a major impact on the children's communications skills. However, changes in the brain regions beneath the cortex (subcortical circuits) resulted in the development of stereotypical behaviors and lack of social interaction.
The study of autism in children with TSC and other specific genetic disorders will provide clues about the causes of autism in general, said Chugani.
Tuberous sclerosis is a genetic disorder that causes benign tumors to form in many different organs including the brain, eyes, heart, kidney, skin and lungs. According to the Tuberous Sclerosis Alliance (formerly the National Tuberous Sclerosis Association), the incidence of TSC has been estimated at 50,000 individuals in the United States and more than 1 million worldwide. It is the result of a genetic mutation and is often first recognized in children who have two neurological symptoms--epileptic seizures or varying degrees of mental handicap, or both.
Autism is a neurological disorder that affects 1 in 500 children and usually appears within the first three years of a child's life. It impacts the brain in the areas of social interaction and communication. Children who are autistic can be intelligent, yet they are unresponsive and have difficulty communicating with the outside world. For example, they have difficulty playing with other children or sharing. Some autistic children show self-destructive behavior, while others may repeat body movements such as rocking and arm flapping.
This study was supported by grants from the National Institute of Health and the National Tuberous Sclerosis Association.
The American Academy of Neurology, an association of more than 17,500 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. For more information about the American Academy of Neurology, visit its web site at www.aan.com.