Abstracts

RATIONALE: Recent studies raise concerns that certain forms of partial epilepsy may be associated with progressive damage to medial temporal lobe structures. These studies, employing a variety of experimental and clinical methods, suggest that continuing seizures over time may result in progressive changes in hippocampal structure and function. To date, clinical studies have utilized a cross-sectional study design. Using a longitudinal study design, we studied patients with medically refractory temporal lobe epilepsy (TLE) due to unilateral hippocampal sclerosis (HS) to determine if progressive hippocampal atrophy was observed.
At the end of this activity, the participants should understand that patients with HS who continue to have seizures are at risk for progressive hippocampal damage.
METHODS: From a cohort of 67 consecutive patients with medically refractory TLE and with volumetric MRI evidence of unilateral HS, 47 underwent anterior temporal lobectomy (ATL), 5 were lost to follow-up, 1 died during a seizure, and 14 were recommended to have surgery by our epilepsy team but refused. Of the 14 patients refusing surgery, 3 became seizure-free on medication, and 11 continued to have seizures. These 14 patients underwent a repeat MRI scan after 2.5 to 5.2 years.
Measures included the interval between the two MRI scans, hippocampal volumes ipsilateral (IHV) and contralateral (CHV) to the side of seizure onset, and seizure status during the interval (seizure-free vs continuing seizures). Reliable Change Indices (RCI) for HV were calculated using CHV test-retest correlations as the basis for SEM.
RESULTS: The mean interval between MRI scans was 3.4 (SD = 0.70) years. A significant decline occurred in mean IHV from first (M = 2676) to second MRI (M = 2476, t(11) = 4.34, p [lt] .01). Mean CHV did not change. There was a significant interaction between mean IHV change and seizure status (F(1,10) = 17.4, p [lt] .01), with seizure-free patients showing no change in mean IHV, and patients with continuing seizures showing a decline in mean IHV. Regarding individual change, all of the 11 patients with continuing seizures showed declines in IHV in excess of the RCI, and the 3 seizure-free patients did not, indicating a relationship between seizure status and decline in IHV (X2lr(1) = 13.5, p [lt] .01). One patient who continued to have seizures showed a CHV decline greater than RCI. No correlations were found between the interval between MRI scans and changes in IHV or CHV.
CONCLUSIONS: These results demonstrate that patients with medically refractory TLE due to unilateral HS develop progressive hippocampal atrophy over time. This suggests that HS is a progressive disorder, which should be treated aggressively.