Pinpointing an Elusive Diagnosis: ADHD or Autism?

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Despite what some skeptics may think, attention deficit disorder (ADHD) and autism are very real disorders, with well-deserved spots in psychologists' diagnostic manuals. To diagnose ADHD and autism, experts in child development use well-tested assessment tools that rely on extensive observations of the children.

Yet too many children still cart around the wrong diagnosis for their behavioral and cognitive difficulties. Some children get misdiagnosed because they are seen by health professionals who are not developmental experts. Other children are simply difficult to diagnose, because their symptoms overlap different disorders. Children with autism, for example, sometimes have symptoms of ADHD; kids with an auditory-processing disorder, meaning they have trouble processing what they hear, may be misdiagnosed as having ADHD or autism.

But these disorders may become easier to diagnose and to differentiate. Researchers are using electroencephalograms (EEGs) in new ways to detect subtle but clear differences in the brain waves of children with and without autism. EEGs, which pre-date imaging devices such as magnetic resonance imaging, or MRI, tests, record the electrical activity of the brain (brain waves) through electrodes attached to the patient's head.

Doctors have traditionally used them to diagnose seizures, but are looking for ways to capture brain activity that indicates ADHD or autism.

Mapping the brain

Regular EEGs until now have not been shown to be very successful for assessing behavioral and cognitive problems in children. So researchers are tweaking the EEG tests and technology to make them more sensitive, sometimes using devices that have many additional electrodes.

EEGs map the brain waves of the resting brain, such as when a person is asleep or just thinking quietly. But researchers are now also recording the brain's response to an event or sensory stimulus. They measure, for example, what happens in the brain when it is processing the difference between word sounds or responding to a flash of light, said Katherine Martien, a neurodevelopmental specialist at MassGeneral Hospital for Children in Boston.

Researchers also use quantitative EEGs to map which types of brain waves are coming from what parts of the brain, and what parts of the brain are "talking" to each other.

Regular EEG tests are only useful for children with autism to test for epilepsy, which is common in children on the autism spectrum. But Martien is very excited about developing the use of the EEG to assess brain function. The EEGs in her research studies show clear differences, for instance, in the responses of children who do not have autism and in those that do. She and her colleagues are presenting preliminary data from their study "EEG Studies of Sensory Processing in Autistic Children" at the Society for Neuroscience conference this month.

The quantitative EEG "gets at some of the underlying brain mechanisms that might lead to the behavioral symptoms," said Patti Davies, an associate professor in the Department of Occupational Therapy at Colorado State University. "The advantage of [this type of] EEG is we can precisely measure to the milliseconds what is going on in the brain when a child is processing information." It's in the 50 to 100 milliseconds after a stimulus occurs where EEGs show differences between children with autism, ADHD, and/or sensory-processing disorders and those without, said Davies.

Watching for mistakes

Psychologist Yvonne Groen and colleagues at the University Medical Center Groningen in the Netherlands are also finding that subtle differences in brain waves correlate with symptoms typical of ADHD or autism, which they reported September 27, 2008, in the online version of Clinical Neurophysiology. In their study, 72 10- to-12-year-olds, including kids with ADHD and kids with symptoms of autism, tried to categorize computer images of fruit, sports and animals. The study indicated the children's' brain waves differed in response to error signals.

All the children had clear peaks in the EEG waves when the computer signaled that they had made a mistake. However, the children with ADHD showed much smaller peaks in their brain waves in response to errors. Interestingly, though, those peaks didn't get smaller as the children learned the task. This suggests that they remained dependent on the feedback, instead of learning to monitor their errors themselves, explained Groen. Children diagnosed with ADHD who were taking medication did better at monitoring their errors compared to those not taking medication.

While this study is important, researchers say EEGs will never totally eliminate the need for behavioral testing for ADHD or autism. "We may someday find one test that is always abnormal in autism, but even if we do, it will not tell the whole story of what is going on with the one child and how to treat him or her," said Martien.

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Health and science writer Tina Adler recently coauthored the Alzheimer's Action Plan, a book for families and friends of people with Alzheimer's disease. She writes for magazines and Web sites, reporting on health, including environmental health issues, and behavior. Places she has published include Environmental Health Perspectives, Additude magazine, The Washington Post and National Geographic World. Before becoming a freelancer, she was a staff writer at Science News magazine, where she covered animal behavior, biology and ecology. She lives outside Washington, D.C.