Imaging language networks before and after anterior temporal lobe resection: Results of a longitudinal fMRI study

Anterior temporal lobe resection (ATLR) for refractory temporal lobe epilepsy (TLE) (Wiebe et al., 2001) may be complicated by impairment of verbal memory (Hermann et al., 1995; Helmstaedter & Elger, 1996; Bonelli et al., 2010) and language, especially naming, after ATLR in the language dominant hemisphere (Davies et al., 1998). Many functional magnetic resonance imaging (fMRI) studies have identified typical language areas in healthy controls and in patients with TLE. Verbal fluency and verb generation tasks reliably activate the left inferior frontal gyrus (IFG) (Binder et al., 1996; Woermann et al., 2003; Gaillard et al., 2004), whereas the lateral temporal neocortex is activated by sentence comprehension tasks (Gaillard et al., 2002). Few studies have reported activation in the medial temporal structures. Naming typically involves the perisylvian cortex, and basal temporal regions potentially affected in TLE (DeLeon et al., 2007; Trebuchon-Da Fonseca et al., 2009). Twenty-five percent of patients with hippocampal sclerosis (HS) experience a clinically significant naming decline after left ATLR (Saykin et al., 1995; Davies et al., 1998) and there is evidence for direct involvement of the dominant hippocampus in naming (Hamberger et al., 2007). Few fMRI studies have systematically investigated functional reorganization of language after ATLR. Postoperatively, language activation may shift to the contralateral hemisphere in patients with seizures in the language dominant hemisphere (Hertz-Pannier et al., 2002). There is evidence for both intrahemispheric and interhemispheric reorganization of language function after ATLR (Noppeney et al., 2005). One longitudinal fMRI study showed that the language network was affected differently by left and right TLE and was reorganized after ATLR (Wong et al., 2009). Only a few studies considered the role of fMRI to predict postoperative language outcome. Preoperative language fMRI with a semantic decision task was used to predict language decline in patients with TLE (Sabsevitz et al., 2003). In the current longitudinal study we tested the hypotheses that:  Reorganization of language function will be different for patients undergoing left or right ATLR.  There is a relationship between preoperative language fMRI activation and language test proficiency in patients with TLE.  The relationship between language function and VF activation is affected by ATLR and differs between the dominant or nondominant hemispheres.  Preoperative language fMRI can predict postoperative language deficits, particularly naming decline, after left ATLR.