Abstracts

RATIONALE: To test the hypothesis that cerebral reserve (brain-reserve capacity) modifies the risk of adverse cognitive outcomes associated with chronic and intractable early onset temporal lobe epilepsy. METHODS: Patients (n=110) had intractable complex partial seizures of unilateral temporal lobe origin with onset ?12 years, chronological age ?16, left-hemisphere speech dominance, were not intellectually impaired (IQ ?70) and were without MRI findings other than atrophy. Patients were divided into two groups on the basis of years of formal education (<12 years, ?12 years) to reflect low and high cerebral reserve. Duration of epilepsy was related to WAIS-R Verbal, Performance and Full Scale IQ scores. RESULTS: For patients with low cerebral reserve (< 12 years education), longer duration of epilepsy was associated with significantly (p < 0.05) declining Verbal (r= -0.50), Performance (r= -0.37) and Full Scale (r= -0.46) IQ. In contrast, for patients with greater cerebral reserve (?12 years education) there was no relationship between duration of epilepsy and Verbal (r= 0.10), Performance (r= -.03) or Full Scale (r= 0.06) IQ scores. Multiple regression analyses were conducted within the low and high cerebral reserve groups with duration of epilepsy, age of onset, gender and laterality of TLE as predictor variables which were entered in a backward fashion to control for collinearity. Dependent variables were Verbal, Performance and Full Scale IQ scores. Analyses were significant only for patients with low cerebral reserve and only duration of epilepsy was a significant predictor of decreasing Verbal (p = 0.004), Performance (p= 0.04) and Full Scale IQ (p= 0.008). These findings were replicated in an independent sample (n= 180) of similarly selected patients. CONCLUSIONS: The concept of cerebral reserve modifies the risk of adverse neuropsychological outcomes secondary to chronic and intractable early onset temporal lobe epilepsy. Patients with low cerebral reserve appear vulnerable to the adverse neurobiological consequences of increasing years of difficult-to-control epilepsy, while patients with high cerebral reserve are significantly less affected.