Ketogenic Diet in Pediatric N-Methyl-D-Aspartate Receptor Encephalitis Presenting with Refractory Epilepsy: A Novel Case Report

Autoimmune encephalitis, notably anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, presents with drug-resistant seizures and neurodevelopmental impairment, posing a therapeutic challenge. We report the first-of-its-kind case of pediatric NMDAR autoimmune encephalitis with refractory epilepsy successfully treated with a ketogenic diet (KD). The patient, a toddler aged 2 years diagnosed with NMDAR autoimmune encephalitis and pharmacoresistant epileptic spasms, despite triple anti-seizure medication (sodium valproate, brivaracetam, zonisamide). Positron emission tomography and computed tomography revealed left hemispheric hypometabolism. The electroencephalogram demonstrated bilateral fronto-centro-parietal epileptiform discharges. A non-fasting, South Indian-style KD was initiated in September 2024. Nutritional ketosis (4+ urine ketones) was achieved by day 3, with a 2:1 ratio maintained. The KD was individualized using the nutrition care process. Seizure frequency declined by 70% in the 1 st month, 90% by the second, and complete seizure remission by the 4 th month, sustained at 10 months. Concurrently, neurodevelopmental gains and normal growth were documented without nutritional deficiencies. This case highlights KD’s efficacy as an adjunctive metabolic therapy in autoimmune encephalitis with refractory seizures, offering a promising avenue for seizure control and improved functional outcomes in pediatric populations.