Functional MRI and the Wada test provide complementary information for predicting post-operative seizure control

AbstractPrediction of post-surgical seizure relief and potential cognitive deficits secondary to anterior temporal lobectomy (ATL) are important to pre-surgical planning. Although the intracarotid amobarbital test (IAT) is predictive of post-ATL seizure outcome, development of non-invasive and more precise means for determining post-ATL seizure relief are needed. We previously reported on a technique utilizing functional MRI (fMRI) to evaluate the relative functional adequacy of mesial temporal lobe structures in preparation for ATL . In the present study, we report follow-up outcome data on eight temporal lobe epilepsy (TLE) patients 1-year post-ATL who were evaluated pre-surgically using IAT and fMRI. Functional memory lateralization using fMRI predicted post-ATL seizure outcome as effectively as the IAT. In general, asymmetry of functional mTL activation favouring the non-epileptic hemisphere was associated with seizure-free status at 1-year follow-up. Moreover, when combined, fMRI and IAT provided complementary data that resulted in improved prediction of post-operative seizure control compared with either procedure alone

Hemispheric Specialization During Episodic Memory Encoding in the Human Hippocampus and MTL

Hemispheric specialization during episodic memory encoding was examined using three functional magnetic resonance imaging (fMRI) tasks. Stimuli for the three tasks differed in the degree to which they elicited subjects use of verbal and imagebased encoding strategies. Intentional encoding of visually presented scenes, sentences, and faces was associated with neural activity in the hippocampus and surrounding mesial Temporal Lobe (mTL) structures. Across tasks, materialspecific lateralization of neural activity was observed in the posterior mTL. In contrast, hippocampal activation did not lateralize according to material type for two of the three tasks. These results suggest a functional dissociation between the hippocampus and other mTL subcomponents, and indicate that material-specificity may not fully explain hemispheric specialization in the mTL memory system