Risk factors associated with drug resistant focal epilepsy in adults: A case control study

Purpose: Using an adult cohort of patients with focal epilepsy, we aimed to identify risk factors for development of drug-resistant epilepsy, which if identifiable would allow patients to receive appropriate counsel and earlier surgical treatment.

Methods: This is a case-control study nested within a cohort, 146 adult patients with focal epilepsy were included. Definitions were used in accordance with ILAE criteria. The odds ratio and its confidence interval were calculated. We performed a logistic regression analysis.

Results: Seventy-one [48.6%] patients met the criteria for drug-resistant epilepsy [cases] and 75 [51.4%] patients were controls. The mean age of patients was 44.5 ± 16.4 years. The most significant variables associated with developing drug-resistant epilepsy include younger age at diagnosis [18.75 vs. 32.2, p < 0.001], years of evolution of epilepsy [22.54 vs. 16.05, p < 0.001], number of AED [4.8 vs. 2.87, p < 0.001], complex partial seizures [51 vs. 35 OR 2.9, p = 0.002], having more than one seizure per month [51 vs. 38, p = 0.009], bi-temporal focus [14 vs. 4 p = 0.008] and mesial temporal sclerosis [23 vs. 11 p = 0.01]. Good response to first AED [7 vs. 29 OR 0.2, p = 0.001] and epilepsy secondary to encephalomalacia [8 vs. 20 OR 0.35, p = 0.018] might be protective factors against drug resistant epilepsy.

Conclusions: Longer time of epilepsy evolution, high frequency of seizures, complex partial seizure presentation, higher number of antiepileptic drugs, mesial temporal sclerosis and bitemporal epilepsy are predictive factors of subsequent pharmacoresistance.