Abstracts

Rationale: Drug resistant epilepsy (DRE) affects a significant proportion of people with epilepsy. Studies have reported rates ranging from 16 to 60% depending of the center. Studies have explored the prevalence of DRE using different definitions. In this study we analyzed the prevalence of DRE in a Canadian center using four definitions, including the most recent definition provided by the ILAE. Methods: We randomly selected two hundred and fifty charts from 700 available at the epilepsy clinic of the University Hospital in the province of Saskatchewan, Canada (1 million population). Two independent chart reviewers underwent training regarding the application of the four definitions used in this study. The reviewers performed a pilot with 20 charts. The reviewers did not know the patients and the evolution of the cases over time. We used the definition of DRE published by Kwan and Brodie, Berg, Camfield and the one provided by the ILAE. The reviewers abstracted demographic data, diagnostic of epilepsy, ILAE classification parameters, evolution and used medications. After the extraction of the necessary clinical information, the four definitions were applied. We measure the prevalence of DRE using the four mentioned definitions. Results: Of the 250 charts of patient with epilepsy 53% were males, the age ranged between 17 and 83 years (mean 37 ± 15.6). With respect to classification of epilepsy, 59% had partial onset epilepsy and 23% were classified as idiopathic. For epileptic syndromes, 52% were symptomatic, 24% were unknown, 23.5 % were idiopathic and one was cryptogenic. The prevalence of drug resistant epilepsy using the definition of Berg was 27.5 %, Kwan and Brodie 33.5%, Camfield 36.3% and for the definition of the ILAE was 32.4%. There was no statistical difference between the rates provided by the four definitions (p>0.05). Using only the definition provided by the ILAE, the prevalence of DRE was 33.8% in patients with partial epilepsy vs. 30.4% in patients with generalized epilepsy (p= 0.57). The prevalence of DRE in patients with symptomatic epilepsy was 37.7% (p= 0.063), idiopathic 35.6% (p= 0.47), unknown 16.7% and for cryptogenic only one patient was in this category and also had DRE. More information will be displayed in the meeting. Conclusions: This is the first study of prevalence of DRE in a Canadian center. The prevalence of DRE was high, probably reflecting a reference pattern, being the only center to assess complex patients in the province of Saskatchewan. We found that the prevalence of DRE showed similar rates between focal and generalized epilepsy. No differences were seen between idiopathic and cryptogenic epilepsy. The four definitions showed similar rates, supporting their use in clinical studies.