Seizures, Fever, and Systemic Infection

The concurrence of fever and seizure in a patient raises many questions, the most immediate and important being whether or not the patient has an infection. If present, infection may either be intrinsic to the central nervous system (CNS), may have spread to the CNS from a systemic source, or may remain extracranial. About 5% of patients with CNS infections experience an acute symptomatic seizure (1,2). Infections of the CNS account for about 15% of all acute symptomatic seizures (1,3). Fever can occur for reasons other than infection, including inflammatory and connective tissue disorders, tumors, heat stroke, tissue ischemia, reactions to therapeutic drug use and vaccinations, drugs of abuse (such as ecstasy, amphetamines, and cocaine), factitious fever, and that of unknown origin. Rarely, primary lesions of the hypothalamic thermoregulatory center may lead to fever. Importantly, fever can also occur following prolonged convulsive activity in the absence of infection. In a retrospective study of the temperature curves of patients hospitalized after a seizure, Wachtel et al. found that 43% were febrile during their hospital course (4). Although no underlying infection was identified in two-thirds of these patients, fever persisting beyond 48 h after the seizure was a sensitive (100%) and specific (89%) indicator of infection. Furthermore, infection can result from a seizure (e.g., aspiration pneumonia), or be nosocomially acquired.