Metabolic testing in the pediatric epilepsy unit.

Unexplained mental retardation is noted in up to 3% of the general population, and upwards of 30% of these patients manifest epilepsy. There is no standardized approach to metabolic testing in these patients. In a first step toward a standardized approach for our center, we performed a retrospective evaluation of testing of our patients in the past. Records of 429 children admitted to our pediatric epilepsy-monitoring center in 2005 were reviewed. We noted whether they had developmental delay, their type of epilepsy, and the extent of metabolic testing. Ninety percent of our patients had developmental delay, and 20% received some form of metabolic testing. Abnormal results suggesting mitochondrial dysfunction were found in 28% of our patients without a previous underlying diagnosis. Metabolic abnormalities were found in 75% of those with multifocal interictal discharges. Secondary carnitine deficiency was identified in 22%; these patients were taking valproic acid. Primary or secondary metabolic abnormalities likely represent a prominent finding in these patients. Differential diagnoses involving mitochondrial dysfunction should receive serious consideration. Findings such as carnitine deficiency can be identified and treated. A systematic approach for such testing is needed. A prospective evaluation at our institution is planned.