Prophylaxis of Posttraumatic Seizures

Abstract

The issue of routine anticonvulsant prophylaxis for early and late posttraumatic epilepsy (PTE) has received much attention in the medical literature. Such problems as lack of standard definitions for early and late PTE, the retrospective design of most studies, the wide variability of inclusion and exclusion criteria, and the varied duration of follow-up make this body of literature extremely difficult to evaluate. Severe head trauma appears to cause injured neurons to become hyperexcitable; this in turn brings about the formation of an epileptogenic focus during the time between trauma and seizure occurrence. Both military and civilian head injury populations have been used to evaluate the incidence of PTE. Early seizures (i.e., <7 days) occur in approximately 3–5 percent of the head injury patients in both the military and civilian groups. Factors increasing this incidence include intracranial hematoma, focal neurologic deficits, posttraumatic amnesia (PTA) lasting >24 hours, depressed skull fracture, and age <5 years. The incidence of late seizures is directly related to the extent of brain damage. The military population, composed primarily of cases with penetrating head injury, is associated with a late PTE incidence of approximately 30–50 percent. Closed head injuries in the military population involve a 5–15 percent seizure incidence. Late PTE incidence after head injuries in the civilian population is <5 percent. Risk factors associated with late PTE include loss of consciousness or PTA lasting >24 hours, dural lacerations, depressed skull fractures, and various computerized tomography deficits. These factors vary slightly between the military and civilian populations. Seizures typically present as focal or generalized, or as a mixed focal-generalized seizure that begins as a focal and progresses into a generalized seizure. Studies on the efficacy of prophylactic treatment have given equivocal results. Most studies to date have included insufficient numbers to show significance. Few well-controlled trials have been conducted. Based on these findings, prophylactic treatment of early seizures is recommended, especially if risk factors are present. Although the evidence supporting the use of anticonvulsants in late PTE is much weaker, treatment should be considered if risk factors exist. Duration of treatment will depend upon the severity of the injury and the number of risk factors present. There is need for a large cooperative trial to determine the usefulness of prophylactic therapy for the prevention of seizures in head trauma patients.