A seizure complication of infection can consist of a single seizure or can go on to become a chronic epilepsy. Seizures can arise as an acute, subacute, or long- term consequence of an infectious state. The type of epileptic complication and when it arises from an infection depend on the nature of the infectious illness, its duration, and the type and extent of damage to the CNS.

Quantitative data on seizure risk from infection would be extremely useful but there are few detailed studies. One reason is that retrospective analysis of seizure risk factors is complicated by the interdependence of the many multisystemic and iatrogenic events typically impacting patients during the course of their illness.

A retrospective study of survivors of encephalitis or meningitis between 1935 and 1981 was conducted to assess the risk of unprovoked seizures after CNS infection.5 The 20-year risk of developing unprovoked seizures was 6.8%, and the ratio of observed to expected cases of unprovoked seizures was 6.9. The increased incidence of unprovoked seizures was highest during the first 5 years after CNS infection but remained elevated over the next 15 years of follow-up.

In this study, the type of CNS infection and seizure occurrence during the acute phase of CNS infection greatly influenced the risk of subsequent unprovoked seizures:

  20-year risk of unprovoked seizures
Type of infection With acute-context seizures Without acute-context seizures
Viral encephalitis 22% 10%
Bacterial meningitis 13% 2.4%

The 20-year risk of 2.1% for patients with aseptic meningitis was not increased over the seizure incidence in the general population.

Adapted from: Goldstein MA and Harden CL. Infectious states. In: Ettinger AB and Devinsky O, eds. Managing epilepsy and co-existing disorders. Boston: Butterworth-Heinemann; 2002;83-133. With permission from Elsevier (www.elsevier.com).

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Reviewed By: 
Steven C. Schachter, MD
on: 
Wednesday, March 31, 2004