Abstracts

RATIONALE:_ The value of functional MR Imaging (fMRI) in assessing language lateralization in epileptic patients candidate for surgical treatment is increasingly recognized. However few data are available for left-handed patients. Moreover determining factors for right hemispheric dominance (HD) are rarely reported. METHODS:_ We studied 20 patients (14 males, 6 females; 9 right-handed = RH, 11 left-handed = LH) aged from 9 to 48 years, investigated for intractable partial epilepsy. Epileptic focus location was temporal in 14 cases, extratemporal in 6 and lateralized in left hemisphere in 11/20. Hemispheric dominance for language was evaluated by post-ictal clinical examination in 15 patients, Wada test and fMRI using a silent word generation paradigm in all patients. FMRI language lateralization index was calculated from the number of activated pixels (t test, p<0.0001) in the right and left hemispheres. RESULTS:_ Wada test showed that 8 patients had right HD (among them 6 were LH and 2 RH) and 12 patients had left HD (among them 5 were LH and 7 RH). These results were concordant with clinical post-ictal examination in 11/15 patients (73%). For the other patients clinical status did not allow to conclude. FMRI was concordant with the Wada test in 19/20 cases. For one LH patient, fMRI showed bilateral activation, whereas Wada test demonstrated a right HD. Right language lateralization was significantly correlated with a left lateralized epilepsy (p<0.05) but it was not correlated with age at epilepsy onset, early brain injury (before 2 years) and lobar localization of epileptogenic focus. CONCLUSIONS: Atypical language dominance was found in this series of refractory epileptic patients with 55% of right hemispheric dominance in left-handed patients and 22% in right-handed patients. This condition can be demonstrated by functional MRI.