Abstracts

Rationale: Brain surgery with anterior temporal lobe resection (ATLR) leads to seizure freedom in 60% to 80% of patients with medically refractory temporal lobe epilepsy (TLE), but up to 40% of these patients are also at risk of postoperative decline in memory and language function. Under this assumption, functional magnetic resonance imaging (fMRI) performed prior to epilepsy surgery is a key non invasive tool in the assessment of language and memory lateralization. This is done in order to minimize the risk of functional loss after surgery, as language and memory decline are one of the mayor limitations in indicating epilepsy surgery. The goal of the present study is to show, using fMRI, that differences exist in language lateralization among left (LTLE) and right (RTLE) temporal lobe epilepsy patients and a control group.Methods: We compared 17 right handed patients (7 men, mean age of 41.2 years), all of them being possible recipients of epilepsy surgery during years 2009 and 2010 (eight of patients were diagnosed with RTLE and nine with LTLE); and a control group of 16 healthy subjects matched by age, sex and level of studies. All patients and control group underwent to a specific fMRI paradigm. For the fMRI paradigm, a block designed task was used. Subjects had to listen to 30 seconds duration blocks of phrases separated by 15 seconds of rest. Lateralization index was calculated using the contrast phrases versus rest and an anatomical region of interest (ROI) which comprises the superior and medium temporal gyrus and the temporal pole Results: While all 16 controls and 7 out of 8 RTLE patients showed a bilateral activation of the superior temporal lobe (STL), 6 of the 9 patients with LTLE showed a higher activation of the right STL. The remaining patient from the RTLE group was left-lateralized, while the remaining 3 from the LTLE showed a bilateral activation. Five of the six patients with LTLE who were right-lateralized, have undergone surgery, none of them showing, under a neuropsychological study, a decline in language or verbal memory 3 months after the operation Conclusions: In patients with left TLE candidates for resective epilepsy surgery, unlike those with right TLE and controls, the language fMRI allows to identify a greater STL activation contralateral to the damaged hemisphere.