Abstracts

RATIONALE: Recent studies raise concerns that certain forms of partial epilepsy may be associated with progressive damage to medial temporal lobe structures. We sought to determine if a correlation exists between the duration of epilepsy and the severity of hippocampal damage and cognitive functioning in patients with TLE due to HS. METHODS: We studied 33 consecutive patients who underwent temporal lobectomy for medically intractable TLE associated with volumetric MRI evidence of HS. All patients underwent a comprehensive presurgical evaluation, and the severity of HS was graded pathologically using a previously described semi-quantitative schema. RESULTS: HS Grade correlated with seizure duration (r = .53) and age of onset (r = -.56). Subjects with onset prior to age 10 had significantly higher HS Grade (4.0 vs. 3.1) and more asymmetric HF Ratio (0.69 vs. 0.76). Patients with seizures more than half of their lifespan had higher HS Grade (3.8 vs. 2.5) and more asymmetric HF Ratio (0.71 vs. 0.80). There was evidence for longer duration being associated with worse performance on neuropsychological measures. Specifically, for all patients longer duration was associated with worse performance on verbal memory (r = -.38) and the Comprehension and Similarities subtests of the WAIS-R (r = -.40; r = -.42). Earlier age of onset was likewise related to the latter two measures (r = .37; r = .45). For the left onset patients, age of onset was related to immediate verbal memory (r = .52), verbal fluency (r = .45), and WAIS-R Similarities (r = .58). For right onset patients, duration was associated with immediate and delayed nonverbal memory (r = -.69; r = -.48), and the WAIS-R Comprehension, Similarities, and Picture Completion subtests (r = -.57; r = -.55; r = -.57). For these subjects, age of onset was also related to immediate nonverbal memory (r = .51). CONCLUSIONS: The results of this study suggest that patients with earlier seizure onset and longer duration of epilepsy have more severe HS, as determined by volumetric MRI and pathologic evaluation, and exhibit greater cognitive dysfunction. These findings support the concept of HS as a progressive epileptic disorder, which should be managed aggressively.