Brain Imaging as a tool to diagnose Autism

Autism spectrum disorder (ASD) is a range of complex neurodevelopment disorders, characterized by social impairments, communication difficulties, and restricted, repetitive, and stereotyped patterns of behavior.  Autistic disorder, sometimes called autism or classical ASD, is the most severe form of ASD, while other conditions along the spectrum include a milder form known as Asperger syndrome, the rare condition called Rett syndrome, and childhood disintegrative disorder and pervasive developmental disorder not otherwise specified (usually referred to as PDD-NOS).  Although ASD varies significantly in character and severity, it occurs in all ethnic and socioeconomic groups and affects every age group.  Experts estimate that three to six children out of every 1,000 will have ASD.  Males are four times more likely to have ASD than females.

One major problem encountered in this form of neurodevelopmental disorder is the lack of a standard diagnostic test  that would help detect autism as early as infancy and put forward necessary intervention to slow its further progress.Currently medical professionals rely on clinical judgments such as prominent changes in behavior which are not quite evident until the child reaches school age.

Researchers at The Children’s Hospital of Philadelphia however have found that children with autism spectrum disorders (ASDs) show a fraction of a second delay in processing sound and language compared with their non-ASD counterparts. Timothy P.L. Roberts, Ph.D., vice chair of Radiology Research at Children’s Hospital say that this could be used as a standard diagnostic test for autism by measuring magnetic signals that mark this delay.He also claims that this delayed response detection could probably be developed into the first biomarker for autism and could also be used to differentiate between different forms of Autism. The findings of the study were published in an online article in the journal Autism Research.

For the current study Robert and colleagues took 25 children with ASDs, with an average age of 10 years, to 17 age-matched children who were in the initial stages of developing the disorder. They used Magnetoencephalography (MEG), which uses magnetic fields in the brain to detect delayed brain response. The team analyzed the response of children to a series of recorded beeps, vowels and sentences. As the child’s brain responds to each sound, noninvasive detectors in the MEG machine analyze the brain’s changing magnetic fields. The children with ASDs had an average delay of 11 milliseconds (about 1/100 of a second) in their brain responses to sounds, compared to the control children. Among the group with ASDs, the delays were similar, whether or not the children had language impairments.The 11 millisecond delay may sound as relatively short delay however the delay may cascade as a conversation progresses, and the child may lag behind typically developing peers. Robert suggests that the delayed response could be a sign of slow auditory system development and matures in children with ASDs.
Previous studies conducted by Robert demonstrated how the anatomy of the brain was involved in delayed auditory responses. They analyzed development of white matter in the brains of 26 typically developing children and adolescents. Because white matter carries electrical signals in the brain, signaling speed improves when neurons are better protected with an insulating sheath of a membrane material called myelin. Normal age-related development of greater myelination accounts for faster auditory responses.However in children with ASD there is delay in white matter development which is key to their display of a slow auditory response. Roberts says his team’s hope to improve their imaging techniques to determine the specificity of their new biomarker to ASD, and will work on other MEG patterns found in children with ASDs in addition to auditory delays.

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