September 15, 2009 (San Francisco, California) — A new study using electroencephalogram (EEG) readings in children with learning disabilities (LDs) and attention deficit disorder (ADD) adds new data to literature that indicates that EEG may be a promising diagnostic and assessment tool for these conditions, according to researchers here at the American Neurological Association 135th Annual Meeting.

In the retrospective analysis of 1198 EEG recordings in prepubescent students with LD and ADD, 218 (18%) had grade II or III (Mayo Clinic classification) EEG abnormalities. However, when follow-up was performed between 5 and 10 years later (mean, 3.6 years), the EEGs of some students — almost 30% of those tested — had normalized.

Although most of the students with normal EEGs at follow-up were on antiepileptic medications, the researchers hypothesized that another possible explanation could be the biological processes that underlie the passage through puberty, said presenter Heather Koch, from the Institute for Behavioral Neurology and Arizona State University in Scottsdale.

"It's possible that antiepileptic drugs could be a strong factor in the normalization of the EEGs, but we've also wondered whether it's possible that there's something about the developmental years that normalizes EEGs in children with LDs and ADD," she said.

Underlying Physiological Basis

Of the 218 patients who originally had abnormal EEGs, only a small percentage (27%; n = 59) returned for follow-up. Of those, 34 (62%) still had abnormal EEGs, and 25 had EEGs that had normalized. Nineteen of the 25 patients with normal EEGs on follow-up were on antiepileptic medication, according to the researchers.

"Our study hints at an underlying physiological basis for ADD and LD disorders, and reasons for improvement other than treatment, since the EEGs of some students in our study normalized spontaneously," Ms. Koch said.

The researchers plan to do further follow-up on the cohort tested in the study and assess the subjects with cognitive and behavioral testing, self-reports, and parent rating scales.

"We'd like to find out if their ADD or LD is persistent or showed improvement if their EEG normalized, or if there was no correlation at all," she said. "We'll be looking for patterns in their cognitive and behavioral development, as well as improvements that may be due to treatment."

Diagnostic Aid

The researchers called for more study on longitudinal and repeat EEGs in patients with ADD and LDs — a modest conclusion that could eventually contribute to understanding the developmental trajectory of brain changes in those with LDs and ADD, said Sandra Loo, PhD, associate professor of psychiatry at the Semel Institute for Neuroscience and Human Behavior at the University of California–Los Angeles, commenting for Medscape Medical News.

Dr. Loo is also conducting research on the use of EEGs in patients with ADD and ADHD (attention deficit hyperactivity disorder) but is using computerized analysis of the resulting EEG signals.

She cautioned that the Arizona State University study was limited by its retrospective nature and by the fact that information about the subjects' cognition and behaviors had not yet been collected.

She also pointed out that patients who are willing to come back for follow-up testing tend to be those who have more favorable outcomes, so that may have skewed the study's results. "Patients with ADD or ADHD who are doing horribly don't tend to come back for follow-up visits because they're not willing, they're too disorganized, or their lives are too chaotic," she noted.

However, Dr. Loo pointed out that her research indicates that there may be promise for using EEG as a tool for diagnosing and monitoring the progress of patients with ADD and ADHD on current treatments. She is now working to correlate changes on EEG with changes in behavior after treatment.

"We don't currently have a test for ADHD, and having that would be a great step forward," Dr. Loo said. "Some researchers feel very certain that EEG is very sensitive to ADHD, but I'm conservative, and I don't think we're at that point yet," she said.

"I think there's promise in EEG as a possible diagnostic aid, but a lot more work needs to be done to find the specific signal that's useful — one that could identify ADHD at a high rate without a lot of false positives or negatives," she said.

Ms. Koch and Dr. Loo have disclosed no relevant financial relationships.

American Neurological Association 135th Annual Meeting: Abstract M-120. Presented September 13, 2010.