Abstracts

OBJECTIVE: Participants should acquire a comprehensive understanding of the structural and functional integrity of the contralateral left hemisphere (LH) in unilateral right temporal lobe epilepsy (RTLE) patients, as well as an appreciation for possible mechanisms of these contralateral brain abnormalities.
Although ictal EEG monitoring in TLE patients typically identifies a unilateral seizure focus, recent research suggests that brain abnormalities in this population extend beyond this unilateral epileptogenic region. However, no study to date has comprehensively evaluated the integrity of the hemisphere contralateral to the seizure focus. In addition, the etiology of these extratemporal, contralateral abnormalities is unknown. Therefore, through utilization of quantitative MRI volumetrics and neuropsychological measures of LH functions, the purpose of the present study is two-fold: 1) to comprehensively evaluate the structural and functional integrity of the LH in RTLE patients in comparison to healthy controls, and 2) to examine the relationship between these abnormalities and clinical variables for the purpose of elucidating the etiology of these abnormalities.
METHODS: Subjects included: 1) 20 LH language-dominant, ictal EEG-monitored, RTLE patients with no other neurological conditions or mental retardation; and 2) 20 right-handed healthy controls matched for age, gender, height, and Beck Depression Inventory (BDI) total. All subjects underwent a brain MRI and completed a neuropsychological evaluation of LH functions including right hand dexterity, verbal memory, and language. LH regions of interest (ROIs) included the hippocampus, four lobes, gray matter, white matter, and total LH. Clinical variables included number if medications and epilepsy duration.
RESULTS: Relative to healthy controls, RTLE patients performed significantly worse on measures of letter fluency (t(32)=.276, p=.025), semantic fluency (t(32) = 3.216, p=.003), and right hand dexterity (Grooved Pegboard: t(32) = -2.308, p=.028). A trend toward significantly poorer performance (p[lt].01) in RTLE patients relative to controls was found on a measure of naming and verbal delayed memory. Measures of verbal intelligence and immediate verbal memory did not yield significant group differences. MRI volumes did not differ significantly between the groups; however, multiple significant correlations were found between MRI volumes and neuropsychological measures. Epilepsy duration was not found to correlate significantly with any of the measures. Number of medications correlated only with letter fluency (p=.442, p=.016).
CONCLUSIONS: Deficits on multiple measures of LH functions suggest that RTLE patients may present with abnormalities in the contralateral LH. Significant relationships between these functional measures and regions of the LH suggest LH brain dysfunction underlies observed functional deficits; however, group differences in LH regional brain volumes, if present, were not significant. Number of anti-epileptic drugs potentially play a minor role in the etiology of extratemporal abnormalities.
[Supported by: Epilepsy Foundation Behavioral Science Summer Grant 2001
NIH grants NS R0137738 and RR-03186]