Epilepsy in tuberous sclerosis patients in Sweden – Healthcare utilization, treatment, morbidity, and mortality using national register data

PURPOSE This study is designed to estimate the prevalence of epilepsy associated with TSC in Sweden and to describe treatment, morbidity, and mortality of TSC patients with epilepsy. METHODS Register data for 2004-2014 was obtained from the National Board of Health and Welfare in Sweden. Patients with TSC were identified using ICD-10 codes. Epilepsy was identified using ICD-10 codes, interventions aimed to treat epilepsy, or prescriptions for antiepileptic drugs. RESULTS The prevalence of TSC was 5.38 per 100 000 individuals. We identified 551 unique patients with TSC, of which 386 (70.1%) had epilepsy. The mean study period was 8.82 years. Antiepileptic drugs were dispensed to 97.9% of patients with epilepsy. The most prescribed antiepileptic drug was sodium valproate. Ketogenic diet was used in 6 (1.6%) patients, vagus nerve stimulation in 23 (6.0%) patients, and epilepsy surgery was performed in 25 (6.5%) patients. The mean number of outpatient visits per year was 4.70 (SD 4.17) and the mean number of inpatient days per year was 3.25 (SD 5.61). The mean number of outpatient visits per year with an ICD-10 code for epilepsy was 1.65 (SD 1.95) and the corresponding number of inpatient days was 2.06 (SD 4.50). A total of 30 patients with TSC and epilepsy died during the study period. CONCLUSIONS The prevalence of epilepsy in this study was in the lower range of previously reported numbers, suggesting that epilepsy may be overestimated in non-population based studies. A substantial part of the healthcare utilization was directly related to epilepsy.