No convincing evidence associates specific seizure types with stroke mechanisms, although location is clearly important. The semiology of late seizures usually parallels that of the early seizures,43 except that late seizures may be more likely to generalize.86
In one study of late seizures after infarction, simple partial seizures (most commonly with motor manifestations, with or without secondary generalization) accounted for 80% of the classifiable seizures, but it was not possible to determine the seizure type in half of the cases.39 Most of the remaining classifiable patients had what are considered to be generalized convulsions, although in the presence of a known focal lesion, often involving cortex, the likelihood of partial onset is very high, regardless of whether it is observed. Complex partial seizures, characterized by altered awareness with or without automatisms, would be expected, particularly with temporal and prefrontal lesions, but studies have not presented enough information to confirm this. Simple partial somatosensory or special sensory seizures are also likely to occur but can be difficult to diagnose unless the suspicion is high or a seizure later generalizes.
Because of involvement of posterior cerebral arteries, seizures resulting from posterior leukoencephalopathy due to hypertension, immunosuppressants, or eclampsia are often characterized by visual phenomena, including formed or unformed hallucinations or amaurosis, and seizures are often multiple.23
Any seizure type may present with status epilepticus (SE), and 8–17% of stroke patients with seizures have SE, often early in their course.75 Convulsive SE, although usually clinically obvious, can be subtle in a deeply comatose person after prolonged seizures and include only minor rhythmic face, limb, or eye movements.80 Nonconvulsive SE is difficult to diagnose and requires a high level of suspicion, especially in those who have not been known previously to have seizures.81–84 Diagnosis is easiest when there are recurrent, stereotyped complex partial seizures, characterized by unresponsiveness and automatisms and separated by incomplete recovery from the postictal state.
More difficult are patients in a continuous “twilight state,” classically associated with nonconvulsive generalized SE in those with idiopathic generalized epilepsy, but increasingly recognized as occurring de novo in elderly patients as a result of partial SE, often of frontal lobe origin.84 The diagnostic dilemma is particularly challenging in those with lesions of vascular or other origin that may in themselves impair cognition and awareness. If recovery does not occur as expected after a witnessed seizure, it is imperative to rule out nonconvulsive SE.85
Probably the most common form of simple partial SE after stroke is SE with focal motor manifestations. This can take the form of repeated brief tonic or clonic activity, or both, contralateral to the lesion, or sustained, somewhat irregularly repetitive movements, often confined to a very limited area such as the hand or the thumb, termed epilepsia partialis continua. This condition is notoriously difficult to treat and may persist for days or weeks. Newer drugs that act on the glutamate excitatory system, such as felbamate, may more effectively terminate this form of SE. Use of conventional antiepileptic drugs is still important, however, to prevent spread of the activity, which can involve wider areas of cortex and the corresponding hemibody, or produce complex partial or secondarily generalized seizures.
Reviewed and revised April 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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