Abstracts

Rationale: Functional magnetic resonance imaging (fMRI) has been used increasingly in recent years for preoperative language lateralization in epilepsy surgery patients. Language dominance shift is induced by brain lesions and also by epileptic dysfunction. Approximately 25% of epilepsy patients show atypical language lateralization. Evidence for reversal or reorganization of language following epilepsy surgery is not readily available. We wanted to determine language network changes in patients who underwent pre and post epilepsy surgery language fMRI compared to controls Methods: There were 14 intractable temporal lobe epilepsy patients (6 females, age range 23-57, mean 35 years, all except 1 right handed) who agreed to have repeat language studies. All except 1 had epilepsy surgery. The study was approved by the Austin Health Human Research Ethics Committee and informed written consent was obtained. We used the noun verb (NVG) and orthographical language retrieval (OLR) block design paradigm. Twelve control subjects and 14 patients underwent 3T GE fMRI using multi-slice gradient-recalled echo-planar imaging. The images were converted to Analyze format using in-house iBrain™ software and then pre-processed using Statistical Parametric Mapping software (SPM2) Results: Representative fMRI maps are shown for a patient and a control subject in figure 1. Prior to surgery 11 (79%) patients showed left hemisphere language, 1 bilateral and 1 right hemisphere and 1 no activation. Post surgery 9 (79%) showed bilateral language but in 6 left hemispheric dominant. In 6 patients language shifted from left hemisphere to bilateral. Pre-surgery 1 subject was not considered for analysis and post surgery 2 subject studies were disregarded because activations were inadequate. In the 12 control subjects 17 studies were left hemisphere lateralized, 6 were bilateral and 1 right hemisphere. In 11 (92%) control studies test re-test remained stable with no shift. Conclusions: It is not commonly known that there would be movements in language network arrangements within or between the hemispheres after epilepsy surgery. We used language fMRI to assess the neural correlates of brain plasticity through repeat studies. In our patients just over 50% language changed from left hemisphere dominance to bilateral but remained maximum left hemisphere. There was also more variability in language BOLD responses in patients. Test retest in the control subjects showed remarkable consistency. The bilateral language post surgery supports language reorganization. Our observations suggest that functional organization of language related neuronal networks are not only reorganized with atypical activations noted prior to epilepsy surgery but are also further modified after the surgical intervention. Functional language MRI studies of post-lesional epilepsy surgery plasticity in the literature are scarce. This study supports that there is potential for language plasticity post temporal lobe epilepsy surgery