Currently, there's no reliable medical test for diagnosing autism in children. The disorder is usually diagnosed only after parents or doctors observe developmental delays.

But researchers at Columbia University say functional magnetic resonance imaging could provide a more "objective" method of figuring out if children have the disorder -- possibly enabling an earlier diagnosis.

In a small study published online and in the August issue of Radiology, the researchers say an fMRI scan of a group of sedated autistic children was able to help doctors identify 96 percent of the children with the disorder.
Autism is a so-called spectrum disorder, and symptoms include language difficulties, lack of nonverbal communication and stereotyped, repetitive behaviors. As many as one in 110 children are affected by autism, according to the Centers for Disease Control and Prevention.

In the study, researchers scanned 15 healthy children and 12 age-matched autistic children with language impairments. The average age for both groups was around 12 years old, with an age range between 4 and 17.

While scanned, the children listened to recordings of their parents talking. The scientists then analyzed the activity in two brain regions: the primary auditory cortex (A1) and the superior temporal gyrus (STG), using statistical models to create maps of brain activation.

The scientists said activity in the A1 region - as measured by the fMRI scans - didn't differ between the autistic and control children. However, STG activation was greater for the control children compared with the autistic ones.

The STG region of the brain is associated with sentence comprehension, the researchers said.

"These findings first tell us that the autistic children in our study appeared normal with respect to the primary auditory system," Joy Hirsch, study author and professor of at Columbia University Medical Center and director of the Functional MRI Laboratory, said in a statement. "But it appears that the STG in the autistic brains was not as sensitive to the language narratives as was the STG in the brains of the typical children."

Hirsch and her colleagues also included in the study 27 autistic children undergoing routine MRI exams with sedation. Using the same fMRI technique, they were able to identify 26 of the 27 children with autism, or 96 percent of the autistic children.

However, there were several limitations to the study. Speaking with HealthDay, Dr. Andrew Adesman, a pediatrician with Steven and Alexandra Cohen Children's Medical Center of New York who specializes in developmental disorders, said as many of the children in the study were adolescents, it's not clear that the results would be seen in younger children and toddlers, when autism diagnoses are usually made. He also said the researchers haven't shown that the scans show patterns specific to children with autism, as they might apply to children with other language disorders.

Hirsch said more work needs to be done to refine the tests, which can be a bit pricey. The brain scan costs the same as a standard MRI, or around $1,500, according to HealthDay.

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