When do seizures usually improve with the ketogenic diet?

Purpose: Parents often expect immediate seizure improvement after starting the ketogenic diet (KD) for their children. The purpose of this study was to determine the typical time to seizure reduction as well as the time after which it was unlikely to be helpful in those children started on the KD. Methods: Records of all children started on the KD at Johns Hopkins Hospital, Baltimore (n = 83) and Children's Memorial Hospital, Chicago (n = 35) from November 2003 to December 2006 were examined to determine the first day in which seizures were reportedly improved. Results: Of the 118 children started on the KD, 99 (84%) had documented seizure reduction. The overall median time to first improvement was 5 days (range: 1-65 days). Seventy-five percent of children improved within 14 days. In those children who were fasted at KD onset, the time to improvement was quicker (median 5 vs. 14 days, p < 0.01) with a higher percentage improving within 5 days (60% vs. 31%, p = 0.01). No difference was identified between fasting and nonfasting in regards to long-term outcomes, however. Discussion: The KD works quickly when effective, typically within the first 1-2 weeks. Starting the KD after a fasting period may lead to a more rapid, but equivalent long-term seizure reduction, confirming prior reports. If the KD has not led to seizure reduction after 2 months, it can probably be discontinued.