SIGNIFICANCE: If successful, this personalized treatment approach may be extended to GLUT1-DS patients with other symptoms refractory to the KD, or those who cannot tolerate the diet, and ultimately will serve as a model for eliminating seizures and side effects in other medically refractory epilepsies. The data generated with this study will be essential to design future trials for a larger number of Glut1-DS patients to create high-grade evidence.