Influence of pre-existing dementia on the risk of post-stroke epileptic seizures

Seizures occur in 10% of stroke patients, but their predictors have not been clearly identified. Pre-existing dementia is present in 12-16% of stroke patients and, at the community level, patients with dementia have increased risk of seizures. However, the question of whether pre-existing dementia is associated with a higher risk of seizures after stroke has never been studied.

To evaluate whether pre-existing dementia is associated with an increased risk of seizures after stroke.

The study was conducted on 202 consecutive stroke patients recruited to the Lille stroke/dementia study (97 men; median age, 75 years; range, 42-100). Pre-stroke cognitive functions were evaluated using the Informant Questionnaire on Cognitive Decline in the Elderly, with a cutoff value of 104 for the diagnosis of dementia. Seizures were defined as early seizures when occurring within seven days of stroke onset, and as late seizures when occurring more than seven days after stroke.

Of 202 patients, 33 (16.3%) met the criteria for pre-existing dementia, and 11 (5.4%) developed early seizures. During 289 person-years of follow up, 14 patients developed late seizures, resulting in an incidence rate of 4.8 new cases/100 person-years. Pre-existing dementia was not associated with the occurrence of early seizures, but was independently associated with the occurrence of late seizures (adjusted odds ratio, 4.66; 95% confidence interval, 1.34 to 16.21).

Stroke patients with pre-existing dementia have an increased risk of late seizures. Any factor increasing the risk of seizures (drugs, metabolic changes) should be avoided in these patients.