Boston Children's Hospital: Autism and Asperger's are Different

from: VECTOR Boston Children’s Hospital’s science and clinical innovation blog.

Autism and Asperger’s are different… at least on EEG by Nancy Fliesler on August 15, 2013

Asperger’s syndrome vs. autism spectrum disorders:
This histogram separates children with Asperger’s (in red) from those with autism spectrum disorders (green) based on EEG coherence variables. Although there is overlap with high-functioning autism, the Asperger’s children clearly form a distinct group. (Courtesy BMC Medicine)

Is it Asperger’s syndrome or is it autism? Since there are no objective diagnostic measures, the diagnosis is often rather squishy, based on how individual clinicians interpret a child’s behavior. According to the Diagnostic and Statistical Manual, fourth edition (DSM-IV), early problems with language development are an indicator of autism; if there are behavioral symptoms but no early language problems, the child has Asperger’s. However, if the diagnosis is made late, parents’ recall of early language development may be fuzzy.

Under the new DSM-V, published in May, Asperger’s is included under the general “autism spectrum disorders (ASD)” umbrella. This has raised concerns among families who feel their children with Asperger’s have unique needs that won’t be met in classroom programs designed for autism.

Frank Duffy, MD, a neurologist at Boston Children’s Hospital, believes it’s possible to objectively differentiate Asperger’s from ASDs using a new wrinkle on an old technology. Originally trained as an engineer, Duffy is expert at interpreting electroencephalography (EEG) signals—the wiggly lines that represent electrical activity in the brain.

He’s devised computational techniques that measure the degree of synchrony among signals gathered from 24 different electrodes on different parts of the scalp.

These “coherence” patterns, though not evident to the eye, reflect how the brain is wired, and how it processes and integrates information. And they clearly reveal different patterns of brain connections in children with Asperger’s as compared to children with autism.

“It’s very easy to separate Asperger’s from autism patients by EEG measures,” Duffy asserts. “We could eventually come to the point where diagnostic differences are defined directly by differences in brain activity.”

First, we need to rewind to last year, when Duffy presented results from studying 430 children, ages 2 to 12, with “classic” autism and comparing them with 554 neurotypical controls. The autism diagnoses relied upon the DSM-IV, the Autism Diagnostic Interview, Revised and/or the Autism Diagnostic Observation Schedule. Children with Asperger’s syndrome or very low or high-functioning autism were excluded. In the end, Duffy computed EEG coherence readings for more than 4,000 possible combinations of electrodes.

In the autism group, coherence tended to be reduced in brain areas at short distances from each other, while long-distance coherence was sometimes reduced, sometimes increased. Ultimately, Duffy found several dozen coherence factors that consistently distinguished the children with autism from the controls with more than 90 percent sensitivity.