Traumatic brain injury results in prolonged increase in risk of epilepsy in children

Christensen J, Pedersen MG, Pedersen CB, Sidenius P, Olsen J, Vestergaard M. Long-term risk of epilepsy after traumatic brain injury in children and young adults: a population-based cohort study. Lancet 2009;373:1105-10.

Question 

Among children with traumatic brain injury, how does the risk of epilepsy change over time?

Design 

Cohort study.

Setting 

Denmark.

Participants 

1,605,216 people born between 1977 and 2002.

Outcomes 

Relative risks (RR) of epilepsy over time.

Main Results 

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).

Conclusions 

The longlasting high risk of epilepsy after brain injury might provide a window for prevention of post-traumatic epilepsy.

Commentary 

Head trauma is an important cause of epilepsy and this study is an important contribution to our understanding of the problem. Using data from the Danish National Hospital Register, the investigators identified 78,572 persons who experienced at least one head injury and 17,470 persons with a diagnosis of epilepsy, of whom 1,017 persons had had a prior head injury, in a population of 1,605,216 persons born in Denmark. The relative risks of developing epilepsy in those with mild and severe head injury, with or without a family history of epilepsy, were compared with the risks of epilepsy in those without head injury at yearly time points after the injury and standardized for age, sex, and calendar year. Overall, the relative risks of epilepsy were found to be raised approximately two-fold (RR 2.2) after a mild and seven-fold after a severe head injury (RR 7.4). The risk of epilepsy increased with age and was highest for people older than 15 years at the time of injury for both mild (RR 3.5) and severe (12.2) head injuries. In children, the risk of posttraumatic epilepsy was highest in those aged 0-5 years after severe head injury (RR 7.2), and the risk following mild injury were similar for all aged 0-15. The rate of development of epilepsy was greatest in the few years immediately after head injury, with an over five-fold increase remaining for 2-3 years after a severe head injury, but the excess risk extended for 10 years after mild brain injury, longer than previously reported.1 This study is of commendable size and completeness, with an excellent and sophisticated statistical design, and in our opinion should be considered the reference study in the field.