Incidence of seizures in patients with multiple sclerosis: A population-based study

Objective: To determine whether multiple sclerosis (MS) is associated with occurrence of seizure activity. Patients and Methods: The medical records of all incidence patients with MS in Olmsted County, Minnesota, from 1935 to 1991 were reviewed. The incidence of seizures was calculated by using 3 methods: including only seizures that occurred after definite diagnosis of MS, including all seizures occurring after onset of the first symptoms of MS, and including any seizures regardless of the time of onset relative to MS. These incidences were age-adjusted to the 1970 US population and then compared with the age-adjusted incidence rate of seizures in the general population of Olmsted County. Results: The age-adjusted incidence of seizures among MS patients was not significantly higher than the age-adjusted incidence of seizures in the general population of Olmsted County. The age-adjusted incidence of first unprovoked seizures in Rochester, Minn, was 61 per 100,000 person-years. In patients with the definite diagnosis of MS, the age-adjusted incidence was calculated at 61 per 100,000 person-years (95% confidence interval [CI], 7-114). In the group with seizures after onset of symptoms, the age-adjusted incidence rate was 80 per 100,000 person-years (95% CI, 24-135). In the group with seizures at any time in their life, the age-adjusted incidence rate was 82 per 100,000 person-years (95% CI, 41-158). Conclusion: The present study does not suggest that occurrence of seizures is more common in MS patients than in the general population.