Abstracts

Rationale: Temporal lobe epilepsy remains the most common type of focal onset epilepsy, especially among people with pharmacoresistant epilepsy. While the understanding of this type of epilepsy is much advanced, with the large corpus of published research addressing its various aspects, most work focuses on treatment outcomes and their determinants. Detailed evaluation of causal factors has not been adequately addressed in most published studies. Structured data collection regarding antecedents forms a part of routine practice at our center. The proposed study aims to explore potential etiologic risk factors for temporal lobe epilepsy through a chart review of data, which was prospectively collected at a Canadian epilepsy clinic.

Methods: Consecutive patients diagnosed with temporal lobe epilepsy (TLE) by a single senior epileptologist at a Canadian comprehensive epilepsy center clinic, over a 3-year period, were included. Consecutive patients diagnosed by the same epileptologist as genetic generalized epilepsy (GGE) during this period, were also included as a comparison group. Following an initial training phase, the study database was populated through information on the hospital information system, initially by a student researcher and then independently checked for accuracy and completeness by a Neurology resident. The study database consisted of detailed information prospectively collected at the epilepsy clinic, including demographic and epilepsy details, specifically birth, development and past medical history along with seizure semiology, epilepsy course and EEG as well as brain imaging. Data from the TLE and GGE groups were analyzed to calculate odds ratios, for different antecedents.

Results: A total of 89 patients (average age 42.3±15.9 years, 45 males) in the TLE group and 69 patients (average age 32.8±14 years, 36 males) in the GGE group were included. Factors observed to be strongly associated with TLE compared to the GGE group were history of being active in outdoor sports (OR=2.15, p=0.03), history of head trauma (OR=5.9, p< 0.0001) and previous diagnosis of neuro-infections (OR=8.9, p=0.02). In addition, a history of a seizure during or immediately following acute neurological illness was also significantly associated with TLE (OR=3.2, p=0.045).  No significant association of TLE was observed with family history of epilepsy, history of birth-related brain insult or of febrile seizures. While MRI of 13 (14.6%) patients in the TLE group clearly demonstrated mesial temporal sclerosis, it was reported normal in 45 (50.5%), and in the remaining, focal cortical dysplasia, tumour and other abnormalities were found.