A direct correlation exists between the presence and severity of multiple sclerosis (MS) and the risk for epilepsy, according to study findings published in Neurology.
Investigators obtained patient data from the Swedish MS register (n=14,545) and compared these patients with 43,635 age- and sex-matched controls from the patient register.
Overall, the cumulative epilepsy incidence was 3.5% (95% confidence interval [CI] 3.17-3.76) in patients with MS vs 1.4% (95% CI, 1.30-1.52) in controls (risk ratio 2.5, 95% CI 2.19-2.76). The investigators found an increased risk for epilepsy in patients with MS compared with controls in a Cox proportional model (hazard ratio 3.2; 95% CI, 2.64-3.94). Progressive MS was associated with a higher cumulative incidence of epilepsy compared with relapsing-remitting MS (5.5% [95% CI, 4.89-6.09] vs 2.2% [95% CI, 1.88-2.50], respectively).
Patients with a longer MS disease duration also demonstrated greater cumulative epilepsy incidence. A 5.9% (95% CI, 4.90-7.20) cumulative incidence was observed in patients with an MS duration of 34 years or longer. Following a multiple logistic regression analysis, an Expanded Disability Status Scale (EDSS) score ≥7 and greater disease duration were found to correlate with a greater incidence of epilepsy (odds ratio [OR] 1.03; 95% CI, 1.01-1.04 per year, P =.001; and OR 1.2; 95% CI, 1.09-1.26 per Expanded Disability Status Scale [EDSS]step, P <.0001).
It is possible that the researchers had underestimated epilepsy prevalence in this cohort. In addition, the reliance on ICD codes for detecting epilepsy may have led to incorrect disease identification in some cases, considering the questionable validity of ICD codes for establishing an epilepsy diagnosis.
The finding that MS disease duration is associated with a higher risk for epilepsy “raises the possibility that mechanisms in addition to cortical lesion load, eg, long-standing neuroinflammation, could influence the risk of epilepsy.”
Burman J, Zelano J. Epilepsy in multiple sclerosis: A nationwide population-based register study. Neurology [published online November 8, 2017]. doi:10.1212/WNL.0000000000004740