Abstracts

RATIONALE: In temporal lobe epilepsy (TLE), there is increasing evidence for the involvement of the parahippocampal region structures in seizure generation and propagation. Using high-resolution MRI, we previously demonstrated a decrease in volume of the parahippocampal region structures in intractable TLE (1,2).
The purpose of this study was determine whether there is an association between disease duration, presence of prolonged febrile convulsions and secondarily generalized seizures, and the amount of atrophy in the hippocampus, amygdala and entorhinal cortex in intractable TLE.
METHODS: We studied 82 consecutive patients (mean age, 36 yrs) with intractable, non-foreign-tissue TLE, and 48 neurologically normal controls (mean age, 32 yrs) in whom we performed volumetric measurements of the hippocampus, amygdala and entorhinal cortex on high-resolution MRI. Volumes were categorized as ipsilateral or contralateral to the predominant EEG focus. Association between ipsilateral and contralateral volumes and duration of epilepsy was assessed using Pearson[scquote]s correlation. Simple linear regression was used to assess the slope (rate of volume change across time) and the intercept (volumes at the onset of recurrent seizures). Differences in volumes and presence of secondary generalized seizures and history of febrile convulsions was assessed using Student[scquote]s t test.
RESULTS: There was no correlation between age and mesial temporal volumes in control subjects and patients. Volumes of the hippocampus (p=0.0001), the amygdala (p=0.0002) and the entorhinal cortex (p=0.03) ipsilateral to the seizure focus were negatively correlated with duration of epilepsy. Regression analysis showed that at the onset of recurrent seizures, volumes of both the entorhinal cortex (p[lt]0.00001) and the hippocampus (p=0.0003) were abnormally low ipsilateral to the focus, and that amygdalar volumes were normal. Patients with a history of febrile convulsions had significantly lower hippocampal volumes ipsilateral to the focus (p[lt]0.0001). No relationship was found between febrile convulsions and entorhinal cortex or amygdalar volumes. Comparing patients with and without secondarily generalized seizures, we found no difference in the volume of hippocampus, amygdala and entorhinal cortex.
CONCLUSIONS: Negative correlation between the volumes of the hippocampus, the amygdala and entorhinal cortex and duration of epilepsy indicates that progressive and widespread damage occurs in TLE. Furthermore, the presence of hippocampal and entorhinal cortex atrophy at the onset of epilepsy suggest that both these structures play a critical role in the pathogenesis of intractable TLE.
References
1. Bernasconi N, Bernasconi A, Andermann F, Dubeau F, Reutens DC. Entorhinal cortex in temporal lobe epilepsy: a quantitative MRI study. Neurology 52: 1870-76, 1999.
2. Bernasconi N, Bernasconi A, Caramanos Z, Dubeau F, Andermann F, Arnold DL. Morphometric MRI analysis of the parahippocampal region in temporal lobe epilepsy. Ann NY Acad Sci 911: 495-500, 2000.
[Supported by: Canadian Institutes for Health Research (CIHR) and Savoy Foundation]