Strokes may be divided into ischemic and hemorrhagic strokes. Ischemic strokes can be further subdivided into embolic, thrombotic, and small vessel (“lacunar”) strokes. Hemorrhagic strokes may be categorized by location and etiology.7 Seizures are most likely to result from strokes that directly affect cortex.

All causes of ischemic strokes and most causes of hemorrhagic strokes show marked increases with aging. Some (but not all) studies have shown that the embolic type of ischemic stroke has the greatest tendency to produce both acute seizures and epilepsy,8 perhaps because it is the most likely to involve cortex directly. Also, embolic strokes often include at least a small hemorrhagic component. In experimental models, the direct application of iron increases cortical irritability.

Overall, 4% to 14% of infarcts are associated with early seizures, usually defined as occurring within 1 to 2 weeks of the insult, whereas 3% to 10% are associated with later seizures.8-13

Early seizures are a risk factor for late seizures.14 Late seizures developed in 10 out of 31 patients with early seizures, in contrast to 3 out of 31 matched stroke patients without early seizures.

The longer the interval between the insult and the first seizure, the more likely it is that the seizure represents a permanent change in neuronal connectivity predictive of further seizures if untreated. The occurrence of seizures within a week or two after stroke does not necessarily indicate that epilepsy will develop, however.

The risk of seizures after hemorrhagic stroke is more strongly linked to mechanism and location than for ischemic stroke:

• 17% of hemorrhages in one study, typically with cortical extension, were accompanied by seizures, all occurring at the onset of hemorrhage.15
• Hypertensive hemorrhage is most often subcortical, decreasing the likelihood that seizures or epilepsy will result.16
• Lobar hemorrhage and basal ganglia hemorrhage involving the caudate are associated with a significant risk of acute seizures.17

In a sense, seizures may represent a marker for cerebrovascular disease in older patients:

• New-onset seizures are associated with hypertension, presumably a marker for cerebrovascular disease, even in the absence of clinical or neuroimaging evidence of stroke.18
• Transient ischemic attacks (TIAs) lasting less than 24 hours have in some series been found to presage epilepsy.
• Seniors presenting with seizures were found to have an increased incidence of vascular disease compared with a control population.19
• A trend of declining incidence of idiopathic seizures in seniors parallels the decline in cerebrovascular disease over the years from 1935 to 1984.20

Reviewed and revised June 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.