"Not always the magic bullet"-Insufficient seizure control by ketogenic dietary therapies in Glut1 Deficiency...

Ketogenic dietary therapies (KDTs) are the treatment of choice for Glut1 Deficiency Syndrome (Glut1DS), providing dietary ketones as an alternative fuel to the brain and effectively controlling seizures. Recent evidence indicates insufficient seizure control in Glut1DS patients despite adequate KDT and ketosis.

Fifty-three patients, diagnosed with Glut1DS and treated by KDT, were followed in a single-center outpatient clinic from 2000 to 2023. Epilepsy, present in 44 patients, was analyzed for seizure control, EEG changes, and potential correlations to clinical and genetic features. Epilepsy response to KDT was defined as a >90% seizure reduction on KDT monotherapy.

On KDT monotherapy 27/44 (61%) patients became >90% seizure free, rated as responders. 17/44 were non-responders. Within this group, 10/17 patients responded to KDT plus antiseizure comedication. In 7 patients, KDT plus antiseizure comedication failed to control seizures. No correlations of seizure control to gender, age at start or type of KDT, or SLC2A1 variants were observed. In responders (n = 27), EEG epileptic activity, evident in 15/27 patients, improved on KDT in 5 patients. In non-responders (n = 17), EEG epileptic activity was evident in 14/17 and improved on KDT in 9 patients. EEG background slowing prior to KDT normalized in KDT in all responders (4/27), but in none of the non-responders (4/17).

Epilepsy is a dominant feature of Glut1DS. KDT provides efficient seizure control, but failure to control epilepsy is more common than expected. KDT epilepsy response did not correlate with seizure type, clinical, or genetic features, emphasizing the complexity of this entity. Add-on antiseizure medication can be effective in some patients, without individual drug superiority. Epileptic activity on EEG did not prove a good marker for outcome, but reversible EEG background slowing on KDT might be predictive for favorable seizure control.

Impaired glucose transport into the brain causes a brain energy crisis termed Glut1 Deficiency. Ketogenic diets mimic fasting, provide ketones as an alternative fuel, and effectively restore brain function. In our study, this worked for ca. 60% of patients. To our surprise, epilepsy persisted in about 40% of patients despite ketogenic diets for reasons unknown. Additional medication against epilepsy randomly helped in some patients. We analyzed many parameters without finding obvious explanations. Electrical brain activity improvement on ketogenic diets might be a future marker for efficient seizure control.