Glucose transporter type 1 deficiency: a study of two cases with video-EEG

Glucose transporter type 1 (GLUT1) deficiency is an inborn error of glucose transport. Clinical manifestations are presumed secondary to reduced gluco se transport across the blood brain barrier, and include seizures, abnormal tone, developmental delay and hypoglycorrhachia. A high index of suspicion is important as GLUT1 deficiency is a potentially treatable cause of menta l retardation. We studied two affected children by continuous video-EEG in order to better understand the cause of the clinical manifestations and imp rovement on a ketogenic diet. The EEG was characterized by generalized paro xysmal 2-2.5 Hz spike-wave discharges, although normal EEGs were also obtai ned. Atypical absence seizures were the most prominent clinical seizure. Ep ileptiform activity and clinical seizures occurred in both children while a cutely ketotic and non-ketotic, but were markedly more frequent in one chil d when non-ketotic. Discharges were not associated with a reduction in subs trate for brain metabolism in the blood at that time. Conclusion Atypical absence seizures are common in glucose transporter type 1 deficiency and should alert the clinician to the possibility of this tre atable disorder when present in a young child with developmental delay. Our data suggest that the therapeutic mechanism of the ketogenic diet in this disorder is more complicated than simply delivering ketones as an alternati ve substrate for brain metabolism.