Abstracts

Rationale: Seizure recurrence risk is one of the key management issues after a first seizure. If the risk is high, AED prophylaxis may be motivated and the new ILAE clinical definition of epilepsy allows for an epilepsy diagnosis if the risk of a subsequent unprovoked seizure exceeds 60% in the 10 years following a first seizure. This calls for more information on the risk of seizures recurrence in specific patient groups. Data from the Swedish dementia register (SVEDEM) was cross-referenced to the comprehensive National Patient Register (NPR) to investigate the risk of epilepsy following a first seizure in patients with dementia.  Methods: Among 81192 individuals in SVEDEM, we identified 1131 individuals without preexisting epilepsy that had a first diagnostic ICD9/10 code for seizure (R568, 780D) or status epilepticus (SE; G41, 345Q) after dementia diagnosis. Epilepsy was defined as occurrence of an epilepsy diagnostic code (G40 or 345) in the NPR. Comorbidities (stroke, trauma, and tumor) were identified in the NPR by relevant codes. Data were analyzed with Kaplan Meier analysis, with censoring at death or 31 December 2017. All calculations were performed in SPSS, version 23 for Mac. Results: Out of 1131 individuals with a first diagnostic code for seizure or SE, 223 (19,7%) had a subsequent seizure diagnosis in the NPR. The 10-year KM risk was 33.4% (95%CI:28.1-38.7). The 10-year risk was higher for patients <65 years of age at the time of the first seizure (54%, 95%CI: 39.3-68.7, n=115) than patients aged >65 (30.1%, 95CI:24.4-35.8, n=1016). Only 41 patients had SE as their first seizure code, but following SE the 10-year risk of an epilepsy diagnosis was 58.1% (95%CI:30.7-85.5), although not significantly different from the risk of patients with seizure as their first code (32.8%, 95%CI:27.3-38.3, n=1090). A sensitivity analysis in which patients with comorbidities were excluded demonstrated similar results. Conclusions: The crude risk of epilepsy after a first seizure in patients with dementia is not above the risk reported for general first seizure populations. However, younger patients and patients with SE as their first seizure could be at higher risk of subsequent epilepsy. Limitations include that acute symptomatic seizures and AED treatment is not yet analyzed in the cohort. More studies are also needed on prognostic factors after a first seizure in dementia patients, such as MMSE score and dementia type.  Funding: Region Västra Götaland ALF, Swedish Society of Medicine, Swedish Society of Medical Research, Linnea and Josef Carlsson foundation, Göteborg Medical Society, Magnus Bergvall foundation. Sara Garcia-Ptacek is supported by a postdoctoral stipend from the Swedish Society of Medical Research.