Incidence of overnight EEG abnormality in Down's patients with comorbid diagnosis of autism

Background: Down's Syndrome may present  with autism as a secondary diagnosis.This may be the result of overlap, or it may have another medical cause. The author hypothesized that  patients may suffer from occult clinical epilepsy. 

Objectives:

Six Down's patients with autism as a secondary diagnosis were studied for an abnormal EEG as the cause of their autistic features. Treatment with valproic acid was also done for an abnormal EEG to see if clinical autistic features could be modified.

Methods:

Six patients with Down's were studied after presenting with onset of autistic features after age 2 years of age. There were 5/6 male patients, and the 1 patient had epilepsy for 1 year with regression. The patients were studied with ambulatory digital EEG for 24 hours. Patients were offered treatment with valproic acid if the EEG was abnormal. The patients were then evaluated  for observed improvement in their autistic features and EEG. Valproic acid trough serum levels were maintained > 80mg/ml < 120 mg /ml.

Results:

Epileptiform central-temporal or parietal discharges were seen in 4/5 patients (3male, 1 female). All were given valproic acid therapy and the EEG improved in 2/4 patients restudied at time of abstract submission. Behavior also showed improved autistic patterns.The single patient with seizures had a varient of continuous spike wave in sleep(CSWS).

Conclusions:

Abnormal EEG was seen in 80 percent of these patients. The other patient with seizures had a unique EEG associated with regression called CSWS. All patients to date have responded to treatment with valproic acid and EEG has responded to aggressive treatment in those restudied.The fact that a high percentage of Down's patients had abnormal EEG patterns that may be part of their comorbid autism supports the need for neurological evaluation for occult epilepsy. This would better define the relationship of EEG abnormality, epilepsy, and autistic behaviors in patients with Down's Syndrome.