Abstracts

Rationale: Localization of the brain areas involved in language function is critical for presurgical evaluation of the patient with medication resistant temporal lobe epilepsy (TLE).Methods: We used functional MRI (fMRI) to study language lateralization in 61 patients with intractable TLE that were seen at London Health Science Centre over 3 years. Twelve healthy control subjects were used for comparison (6 females), all right-handed with a mean age of 26.6±5.3 years. A box-car design verb generation paradigm was used in 1.5T GE MR scanner. The data were processed using SPM2 software and region of interest (ROI) analysis. Laterality index (LI) was calculated using the number of activated voxels for the inferior frontal gyrus (IFG, BA44,45,47), middle frontal gyrus (MFG, BA9,46), and posterior language area (PLA, BA21,21,39). LI<0.20 represented atypical language lateralization. Results: There were 27/61 male and 34/61 female patients: 37 (18 females) had left TLE, 19 (12 females) had right TLE and 5 (4 females) had bilateral TLE. All patients spoke English as their first language. For left TLE patients, the average age of onset was 20.6+14.2 years, age at time of fMRI 38.3+14.9, and epilepsy duration 16.6+11.6. Right TLE patients had an average age of onset of 17.3+11.7 years, age at fMRI 33.1+11.0, and epilepsy duration of 15.9+9.1. Bilateral TLE patients had an average age of onset 18.2+15.3 years, age at fMRI 33.4+13.3, and epilepsy duration of 15.2+11.4. Atypical representation for language among all the TLE patients included 32% for IFG, 36% for MFG, and 34% for PLA. The corresponding values for the left TLE patients were 34%, 33%, and 37%, for the right TLE patients 21%, 44.5%, and 27% and bilateral TLE patients 75%, 25%, and 40%. Healthy controls had 36%, 16%, and 20% atypical representation for IFG, MFG, and PLA, respectively. There was a weak correlation (r=0.3) between verbal IQ and LI for the MFG among the TLE patients.Conclusions: There was a high incidence of atypical language representation among the patients with left TLE and bilateral TLE for IFG and PLA, while the right TLE patients have the highest incidence of atypical representation for MFG. Greater activation of MFG in TLE patients with higher IQ was suggestive of brain plasticity.