Posttraumatic Epilepsy

Updated: Apr 04, 2014
  • Author: David Y Ko, MD; Chief Editor: Selim R Benbadis, MD  more...
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Overview

Background

Posttraumatic epilepsy (PTE) is a recurrent seizure disorder that apparently results from injury to the brain. This injury may be due to traumatic brain injury (TBI) or to an operation on the brain. There is an increase in PTE due to increasing TBI. [1]

PTE must be differentiated from posttraumatic seizures (PTS), which is a broader-spectrum term and signifies seizures that occur as a sequel to brain injury. Seizures that occur within 24 hours after brain injury are called immediate PTS. PTS that occur within 1 week after injury are termed early PTS, and seizures that occur more than 1 week after injury are termed late PTS. About 20% of people who have a single late posttraumatic seizure never have any further seizures, and these people should not be labeled as having PTE.

In a patient who is still hospitalized after a recent head injury, investigation of a seizure should focus on determining whether an intracranial bleed or a change in clinical condition (eg, hyponatremia) has caused the seizure (see Workup). Early PTS should be treated promptly, but treatment for late PTS is not mandatory (see Treatment and Management)

Go to Epilepsy and Seizures for an overview of this topic.

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Pathophysiology

The mechanism by which trauma to brain tissue leads to recurrent seizures is unknown. Cortical lesions seem important in the genesis of the epileptic activity. Early seizures are likely to have a different pathogenesis than late seizures; early PTS are thought to be a nonspecific response to the physical insult.

The PTE kindling model of epilepsy postulates that iron deposition from extravasated blood leads to damage by free radicals, and the accumulation of glutamate leads to damage by excitotoxicity. Animal studies suggest that disruption of the blood-brain barrier is likely to contribute to the generation of seizures in PTE. The TBI that leads to PTE in humans is probably the best model for studying epileptogenesis but even then it is difficult to do so.

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Etiology

By definition, PTE is a result of injury to the brain. Patient factors that increase susceptibility to PTE include the following [2] :

  • Age younger than 5 years or older than 65 years
  • Chronic alcoholism

Apolipoprotein E epsilon4 genotype has been proposed as a risk factor, [3, 4] but other studies have not found that to be the case. [5, 6]

Injury-related factors that increase the risk of PTE are as follows [7] :

  • Severe trauma
  • Penetrating head injuries
  • Intracranial hematoma
  • Linear or depressed skull fracture
  • Hemorrhagic contusion
  • Coma lasting more than 24 hours
  • Early PTS
  • History of prior TBI as it tends to be cumulative
  • Focal neuroimaging or electroencephalographic abnormalities in the acute postinjury period [8]
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Epidemiology

Although the incidence of epilepsy in the general population is estimated at 0.5-2%, the incidence of PTS for all types of head injuries is 2-2.5% in civilian populations. This incidence increases to 5% in hospitalized neurosurgical patients. When only severe head injuries (usually Glasgow Coma Scale score < 9) are considered, the incidence is 10-15% for adults and 30-35% for children.

In the United States, the incidence of brain injury is highest among young adults; this is reflected in the incidence of PTE in the relevant age group. Early PTS are more common in children, while late PTS are more common in older adults. [2, 3]

The incidence of PTS is as high as 50% in military series, as these studies include many patients with penetrating head injuries. [9] The incidence of seizures (excluding early seizures) after uncomplicated mild head injury is the same in the military population as in the general population.

In Japan, approximately 150,000 cases of PTE occur each year; this equals 10% of all hospitalized patients with head injury and 1% of all outpatients with head injury. In a study from Norway, the incidence of PTE in a mixed age group of patients with severe head injuries was 23%, and there was significant correlation with severity of injury and intracranial surgery. [10]

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Prognosis

Approximately 80% of first PTS occur within 2 years of the injury. The risk of PTS decreases with time and reaches the normal value for the population at 5 years after the head injury. About half the patients who develop late PTS have 3 or fewer seizures and go into spontaneous remission thereafter.

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Patient Education

As in any seizure disorder, patients must be warned to exercise caution during bathing, swimming, and climbing heights. They should never be alone during these activities. In all situations, appropriate steps should be taken to ensure the safety of the person if a seizure occurs. Patients must also be counseled about the limitations in obtaining or retaining a driver's license.

For patient education information, see the Brain and Nervous System Center, as well as Epilepsy.

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