Thirteen patients with glucose transporter type 1 deficiency syndrome (Glut-1 DS) had repeated measures of attention, memory, fine-motor coordination and well-being during a 5-hour oral glucose tolerance test in a study at Baylor College of Medicine, Houston, TX, and Columbia University Medical Center, New York, NY. Following the glucose load, decrease in clinical seizures and EEG abnormalities within the first 30 minutes, and lasting up to 180 minutes, was associated with transient improvements in attention and motor coordination, without change in verbal learning and memory performance. Transient improvements in the EEG following glucose load included emergence of posterior alpha frequency, resolution of focal frontal and central slowing, and disappearance of interictal generalized spike-and-wave epileptiform discharges. 
COMMENT. Glucose transporter type 1 deficiency syndrome, first described by De Vivo DC et al in 1991, is characterized clinically by acquired microcephaly, infantile onset seizures, psychomotor retardation, choreoathetosis, dystonia, and ataxia. Low CSF glucose (<40mg/dl) is the hallmark of GLUT1 deficiency diagnosis (40-50mg/dl in milder cases). Ratio of CSF to blood glucose is a less reliable marker . Gene sequencing for SLC2A1 mutations that lead to GLUT1 deficiency, a non-invasive initial test, may be preferred to lumbar puncture in children with early-onset absence epilepsy suspected of having GLUT1 deficiency syndrome . GLUT1 deficiency may underlie a significant proportion (>10%) of early-onset absence epilepsies. The ketogenic diet, supplying an alternative fuel to glucose for brain energy metabolism, is an effective treatment for drug refractory seizures associated with GLUT1 deficiency. The transient improvement in attention and occipital alpha rhythm following glucose loading demonstrates the critical dependence of cerebral function and alpha EEG activity on glucose as brain fuel. Of interest, a trial of a chronic hyperglycemic diet failed to provide a protracted improvement in seizure control (Akman CI, De Vivo DC et al. Preliminary observation).