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(Abst. 3.322), 2014

Authors: Ian Walker and Rana Said
Content: Rationale: The ketogenic diet (KD) has proven to be an effective therapy for children with medically-refractory epilepsy. Numerous studies have consistently shown a significant reduction in seizures in patients regardless of seizure type or etiology. However, there is little data as to whether electrographic features are predictive of diet efficacy and how evolution of electroencephalogram (EEG) findings over time correlate with clinical improvement. We sought to determine the correlation between seizure reduction on KD and improvement in notable EEG characteristics. Methods: We collected data from the KD database, Neurophysiology database, and medical records of children on the KD at Children's Medical Center from July 2005 to July 2012. We aimed to identify possible predictors for clinical seizure reduction (efficacy) on KD as it correlates with baseline and serial follow-up EEGs. In particular, we examined characteristic electrographic patterns (spikes, spike density, organization of background, slowing, electrographic seizures, state variation) serially for the duration of treatment with the diet. We developed scoring criteria to analyze these EEG characteristics. Results: We reviewed 89 patients on the KD. 8 patients were excluded (2 did not have epilepsy, 4 were on the KD for <1 week, 1 had no EEGs, and 1 had incomplete data). Of 81 patients, 43 had both an initial and follow up EEG; all others only had 1 EEG or multiple follow up EEGs. We assessed overall positive response rate: 28% (23/81) had >95% reduction in seizures, 34.5% (28/81) had 75-95% reduction, and 17.2% (14/81) had 50-74% reduction. Of our patients, 19.7% (16/81) were non-responders (<50% reduction), with 6% (5/81) showing worsening of seizures on KD. The severity of encephalopathy on last follow up EEG strongly correlated with seizure reduction in those patients with >95% reduction in seizures in comparison to all other patients (p=.002). This association extended to the subset of patients who were seen to have moderate-severe encephalopathy on initial EEG (n=34, p=.009). No significant correlation was found between change in interictal spike frequency and seizure reduction in our overall patient population. Conclusions: Our results confirm past data indicating the efficacy of the KD in the most refractory group of patients with epilepsy, demonstrating a high responder rate with 79.7% of children demonstrating at least a 50% reduction in seizures. Electrographically, improvement in encephalopathy between initial and follow up EEGs predicted a profound response to treatment for those patients who achieved >95% reduction in seizures. These results support the theory that serial EEGs accompanied by appropriate tracking of electrographic patterns can be helpful in predicting positive therapeutic outcomes on the KD.