Posttraumatic Epilepsy Epidemiology
In general, the incidence of Posttraumatic Epilepsy varies with the time period after injury and population age range under study, as well as the spectrum of severity of the inciting injuries, and has been reported to be anywhere from 4 to 53% 1).
Generally posttraumatic epilepsy accounts for less than 10% of epilepsy 2).
In a cohort study, the incidence of self-reported PTE after TBI was found to be 2.8% and was independently associated with unfavorable outcomes 3).
In a large cohort of post-concussion patients Wennberg et al. found no increased incidence of epilepsy. For at least the first 5-10 years post-injury, concussion/mTBI should not be considered a significant risk factor for epilepsy. In patients with epilepsy and a past history of concussion, the epilepsy should not be presumed to be post-traumatic 4).
The Vietnam Head Injury Study (VHIS) is a prospective, longitudinal follow-up of 1,221 Vietnam War veterans with mostly penetrating head injuries (PHIs). The high prevalence (45%-53%) of posttraumatic epilepsy (PTE) in this unique cohort makes it valuable for study.
A standardized multidisciplinary neurologic, cognitive, behavioral, and brain imaging evaluation was conducted on 199 VHIS veterans plus uninjured controls, some 30 to 35 years after injury, as part of phase 3 of this study.
The prevalence of seizures (87 patients, 43.7%) was similar to that found during phase 2 evaluations 20 years earlier, but 11 of 87 (12.6%) reported very late onset of PTE after phase 2 (more than 14 years after injury). Those patients were not different from patients with earlier-onset PTE in any of the measures studied. Within the phase 3 cohort, the most common seizure type last experienced was complex partial seizures (31.0%), with increasing frequency after injury. Of subjects with PTE, 88% were receiving anticonvulsants. Left parietal lobe lesions and retained ferric metal fragments were associated with PTE in a logistic regression model. Total brain volume loss predicted seizure frequency.
Patients with PHI carry a high risk of PTE decades after their injury, and so require long-term medical follow-up. Lesion location, lesion size, and lesion type were predictors of PTE 5).
A study was undertaken to determine the risk of developing posttraumatic epilepsy (PTE) within 3 years after discharge among a population-based sample of older adolescents and adults hospitalized with traumatic brain injury (TBI) in South Carolina. It also identifies characteristics related to development of PTE within this population.
A stratified random sample of persons aged 15 and older with TBI was selected from the South Carolina nonfederal hospital discharge dataset for four consecutive years. Medical records of recruits were reviewed, and they participated in up to three yearly follow-up telephone interviews.
The cumulative incidence of PTE in the first 3 years after discharge, after adjusting for loss to follow-up, was 4.4 per 100 persons over 3 years for hospitalized mild TBI, 7.6 for moderate, and 13.6 for severe. Those with severe TBI, posttraumatic seizures prior to discharge, and a history of depression were most at risk for PTE. This higher risk group also included persons with three or more chronic medical conditions at discharge.
These results raise the possibility that although some of the characteristics related to development of PTE are nonmodifiable, other factors, such as depression, might be altered with intervention 6).
Using Taiwan’s National Health Insurance Research Database of reimbursement claims, Yeh et al. conducted a retrospective cohort study of 19 336 TBI patients and 540 322 non-TBI participants aged ≥15 years as reference group. Data on newly developed epilepsy after TBI with 5-8 years’ follow-up during 2000 to 2008 were collected. HRs and 95% CIs for the risk of epilepsy associated with TBI were analysed with multivariate Cox proportional hazards regressions.
Results: Compared with the non-TBI cohort, the adjusted HRs of developing epilepsy among TBI patients with skull fracture, severe or mild brain injury were 10.6 (95% CI 7.14 to 15.8), 5.05 (95% CI 4.40 to 5.79) and 3.02 (95% CI 2.42 to 3.77), respectively. During follow-up, men exhibited higher risks of post-TBI epilepsy. Patients who had mixed types of cerebral haemorrhage were at the highest risk of epilepsy compared with the non-TBI cohort (HR 7.83, 95% CI 4.69 to 13.0). The risk of post-TBI epilepsy was highest within the first year after TBI (HR 38.2, 95% CI 21.7 to 67.0).
Conclusions: The risk of epilepsy after TBI varied by patient gender, age, latent interval and complexity of TBI. Integrated care for early identification and treatment of post-trauma epilepsy were crucial for TBI patients 7)
Christensen et al. aimed to assess the risk of epilepsy up to 10 years or longer after traumatic brain injury, taking into account sex, age, severity, and family history.
Methods: We identified 1 605 216 people born in Denmark (1977-2002) from the Civil Registration System. We obtained information on traumatic brain injury and epilepsy from the National Hospital Register and estimated relative risks (RR) with Poisson analyses.
Findings: Risk of epilepsy was increased after a mild brain injury (RR 2.22, 95% CI 2.07-2.38), severe brain injury (7.40, 6.16-8.89), and skull fracture (2.17, 1.73-2.71). The risk was increased more than 10 years after mild brain injury (1.51, 1.24-1.85), severe brain injury (4.29, 2.04-9.00), and skull fracture (2.06, 1.37-3.11). RR increased with age at mild and severe injury and was especially high among people older than 15 years of age with mild (3.51, 2.90-4.26) and severe (12.24, 8.52-17.57) injury. The risk was slightly higher in women (2.49, 2.25-2.76) than in men (2.01, 1.83-2.22). Patients with a family history of epilepsy had a notably high risk of epilepsy after mild (5.75, 4.56-7.27) and severe brain injury (10.09, 4.20-24.26) 8).
A total of 647 individuals (>/=16 y) with any of the following abnormal computed tomography (CT) scan findings: extent of midline shift and/or cisternal compression or presence of any focal pathology (eg, punctate, subarachnoid, or intraventricular hemorrhage; cortical or subcortical contusion; extra-axial lesions) during the first 7 days postinjury or best Glasgow Coma Scale (GCS) score of </=10 during the first 24 hours post-TBI. Subjects were enrolled from August 1993 through September 1997 and followed for up to 24 months, until death or their first late posttraumatic seizures.
Main outcome measures: Cumulative probability, relative risk, and survival analyses were used to stratify risks for development of late postttraumatic seizures on the basis of demographic factors, etiology of injury, initial GCS, early posttraumatic seizures, time post-TBI, types of intracerebral lesion by CT scan, and number and types of intracranial procedures.
Results: Sixty-six individuals had a late posttraumatic seizures; 337 had no late posttraumatic seizures during full 24-month follow-up; 167 had no late posttraumatic seizures during time followed (<24 mo); and 54 were placed on anticonvulsants without a late posttraumatic seizures, whereas 23 died before their first late posttraumatic seizures. The highest cumulative probability for late posttraumatic seizures included biparietal contusions (66%), dural penetration with bone and metal fragments (62.5%), multiple intracranial operations (36.5%), multiple subcortical contusions (33.4%), subdural hematoma with evacuation (27.8%), midline shift greater than 5mm (25.8%), or multiple or bilateral cortical contusions (25%). Initial GCS score was associated with the following cumulative probabilities for development of late posttraumatic seizures at 24 months: GCS score of 3 to 8, 16.8%; GCS score of 9 to 12, 24.3%; and GCS score of 13 to 15, 8.0%.
Conclusions: Stratification by CT scan findings and neurosurgical procedures performed were the most useful findings in defining individuals at highest risk for late posttraumatic seizures 9).
A cohort of 2747 patients with head injuries was followed for 28,176 person-years to determine the magnitude and duration of the risk of posttraumatic seizures. Injuries were classified as severe (brain contusion, intracerebral or intracranial hematoma, or 24 hours of eight unconsciousness of amnesia), moderate (skull fracture or 30 minutes to 24 hours of unconsciousness or amnesia), and mild (briefer unconsciousness or amnesia). The risk of posttraumatic seizures after severe injury was 7.1% within 1 year and 11.5% in 5 years, after moderate injury the risk was 0.7 and 1.6%, and after mild injury the risk was 0.1 and 0.6%. The incidence of seizures after mild head injuries was not significantly greater than in the general population 10)
The true incidence of PTE in children is still uncertain because most research has been based primarily on adults.
see Posttraumatic epilepsy in children.