Abstracts

Rationale: Traumatic brain injury (TBI), affecting almost 2 million Americans annually, can lead to chronic and long-term disability including epilepsy. In persons with epilepsy, seizure activity or medication side effects may result in TBI depending on the epilepsy characteristics and the degree of seizure control. A major concern, especially in persons with epilepsy with poorly controlled seizures, is the cumulative effect of repetitive TBI in a short period of time resulting in insufficient recovery time between TBIs. Persons with epilepsy may be at higher risk of functional deficits and worsening of seizures owing to cumulative effects of repetitive TBI because signs and symptoms of TBI, especially mild TBI, may be confused with seizure effects. We hypothesize that those with pre-existing epilepsy or seizure disorder (ESD) are more likely to sustain repetitive TBI and higher severity than those without ESD. Methods: This is a retrospective cohort study of all TBI encounters in South Carolina non-federal emergency departments and hospitals from 1998 through 2011. Multiple admissions and late effects of the same TBI were excluded and the index TBI for each individual was identified. The presence of preexisting comorbid conditions, such as heart disease, hypertension and diabetes, was determined. Cases were persons with preexisting ESD at the time of index TBI and controls were persons with TBI without evidence of ESD. Demographic and clinical characteristics were compared between cases and controls using t-test for continuous variables and chi-square tests of association for categorical variables. Logistic regression was used to examine the association of the independent variables with ESD. Further, cases and controls were compared regarding the proportion of -selected comorbidities; significant differences in proportions were evaluated with confidence intervals. Results: From 1998 to 2001, 235,797 individuals sustained TBI and 5,637 (2.4%) had preexisting ESD. Higher proportions of cases were black, aged 25 years or older, covered by Medicare or Medicaid, have more than one comorbid condition, hospitalized, died in hospital, have repetitive TBI and have sustained TBI because of a fall. All chronic conditions occurred more often in the cases than in controls. After adjustment for these demographic and clinical characteristics, cases were more likely to have repetitive TBI (Odds Ratio=1.54; 95% Confidence Interval 1.41-1.69) and severe TBI (Odds Ratio=1.49; 95% Confidence Interval 1.38-1.60). Cases were twice as likely to have at least one comorbid conditions compared with controls (Odds Ratio=2.09; 95% Confidence Interval 1.95-2.25). Conclusions: The findings underscore the risk of sustaining severe and repetitive TBI in persons with preexisting ESD. Adequate control of seizures and use of protective equipment in those with intractable and atonic seizures and a propensity for falls are crucial to avoiding TBI. Future studies examining the long term cumulative effects of TBI in persons with ESD are needed to fully inform clinical decision making.