NEW YORK, Feb 10 (Reuters) -- For the first time, according to researchers, a link has been found between a structural abnormality of the brain and autism.
The link was discovered by British scientists studying patients with tuberous sclerosis (TS) who were also suspected to have autism. Tuberous sclerosis is an inherited disorder that affects many parts of the body, causing lesions on the skin and in the heart, kidneys, eyes, and brain. It is also associated with mental retardation and autism.
Cambridge University researchers studied 18 TS patients with suspected autism. On testing, 9 were, in fact, found to have autism -- the other 9 where found to have other psychiatric disorders.
When the researchers examined the brain scans of the 18 patients, they found that 8 of them had tubers -- brain lesions commonly found in tuberous sclerosis -- in the temporal lobes. All of these 8 patients had autism. No tubers were identified in the temporal lobes of patients without autism.
"Our report provides the first clear evidence of an association between localized, gross structural abnormalities in the brain and the development of autism," write the study authors in this week's issue of The Lancet.
The authors also state that the number of tubers was significantly greater in patients with mental retardation than in those with a normal IQ. In addition, the degree of mental retardation was associated with the number of brain tubers. Those who were most retarded had more brain tubers than those with normal intelligence.
"Similarly, the number of tubers was significantly greater in individuals with a diagnosis of autism or atypical autism (autism that may differ in certain behavior patterns or which develops at a later age) than in those without this diagnosis," the researchers state.
"The results show the importance of (brain) scan findings in the prognosis of tuberous sclerosis," the authors state, adding that temporal lobe abnormalities present at birth may create a risk for developing autism.
In an accompanying editorial, Dr. Janet Lainhart of the University of Utah's Neuropsychiatric Institute in Salt Lake City writes that the findings leave a number of unanswered questions. These include determining the primary abnormal event in brain development that leads to autism, and whether abnormalities of the temporal lobe lead to abnormalities elsewhere in the brain that may cause autism.
"Do individuals with tuberous sclerosis and tubers exclusively in their temporal lobes develop autism, or are tubers in other areas of the brain also necessary?" Lainhart asks.
However, she says brain imaging techniques, including MRI, along with other studies, are expected to offer further evidence of inborn inabilities linked to the disorder.
Dr. Susan Smalley of the Neuropsychiatric Institute at the University of California, Los Angeles believes the study adds to growing evidence that the temporal lobe is involved in autism, but cautions parents of children with TS not to assume that their children will develop autism.
"The presence of a tumor does not suggest that a child will develop autism, and the absence of a tumor does not suggest that a child will not develop autism," said Smalley. "This study doesn't answer why or how these temporal lobe tumors lead to autism, but suggests that the temporal lobe, itself, is of critical importance."
SOURCE: The Lancet (1997;349:392-395)
