Abstracts

Among patients with temporal lobe epilepsy (TLE), volumetric abnormalities have been reported in a variety of extrahippocampal structures including the thalamus, basal ganglia and cerebellum. The degree to which these abnormalities represent progressive losses over time versus fixed and static anomalies remains to be determined. This 4-year prospective investigation followed a cohort of patients with temporal lobe epilepsy along with age and gender matched controls. The question of interest here is whether patients with TLE exhibit greater declines over time in volumes of the basal ganglia, thalamus, and cerebellum compared to contrrols. To date, a total of 27 patients with TLE (mean age = 32.2 yrs) and 23 healthy controls (mean age = 33.4 yrs) have completed the follow-up procedures, including a follow-up MRI scan 4 years after their baseline evaluation. The TLE group suffered from chronic epilepsy (mean duration = 22.4 years). Quantitative MRI volumetrics were obtained for each subject. Measurement of the various regions of interest was performed using segmented image sets. These image sets were generated by sampling a large number of voxels from realigned and co-registered T1, T2 and PD images and were used as the basis for brain structure delineation. At baseline there were significant group differences in adjusted volumes (age, gender) of thalamus (p=0.03) and cerebellum (p=0.002), with a trend of reduced total basal ganglia volume (p=0.09). Prospectively, there was no differential loss between groups in the volumes of the thalamus (p=.57) or basal ganglia (p=.97). In contrast, there was a different trajectory between the TLE and control groups in regard to change in cerebellar volume, with significantly greater volume reduction in the TLE group (p=.02). TLE patients exhibited significant volumetric reductions in both the cerebellum and thalamus (with a similar trend for total basal ganglia volume) at baseline. These findings are consistent with previous reports indicating that that extra-temporal structures can be adversely affected in chronic TLE. Analyses of volumetric changes over time demonstrated significantly greater decline in cerebellar volume in chronic TLE patients over the 4-year interval. This differential change suggests that the cerebellum may be one structure that is adversely affected in a progressive fashion by chronic and unremitting TLE. (Supported by NIH NS RO1-37738 and MO1 RR03186 (GCRC).)