Functional MRI Activation of Mesial and Anterior Temporal Lobe Structures in TLE

Background: The diagnostic procedure in temporal lobe epilepsy (TLE) and especially presurgical planning requires knowledge about the functional integrity of the areas to be resected. The mesial and anterior temporal lobe (TL) in humans are highly important in emotional, visual and memory processing. The amygdala itself is involved in the perception of emotional facial expression, particularly for fear. Methods: A new visual paradigm presenting animated fearful faces from movie scenes in alternation with landscape scenes was investigated using functional MRI. As a first step 12 healthy subjects (mean age 35 years, range 23 to 48) were scanned in a 1.5 Tesla MRI (blocked design, coronal EPI, voxel size 3.9×3.9×5 mm3). In ongoing experiments patients with unilateral mesial temporal sclerosis are investigated to look for possible lateralizing effects in anterior TL activation patterns. Imaging analysis is done with SPM99. To test for lateralization of anterior mesial temporal activity we compared the number of significantly activated voxels in the amygdala of both hemispheres. Results: In healthy subjects we found highly significant activation of the left and right amygdala, the anterior and mesial temporal lobe in single subjects as well as in group analysis. There was a mostly bilateral activation pattern of these regions with an averaged 0.93 left-to-right ratio of activated voxels in the amygdala. In contrast first results in 3 patients with right-sided TLE showed a strongly lateralized activation pattern to the left hemisphere with a left-to-right ratio of 2.4 in the amygdala. Conclusions: The new visual paradigm is highly effective to induce bilateral anterior TL activation in humans. In TLE patients with unilateral mesial temporal sclerosis the paradigm seems to effect a pattern that lateralizes the side of the mesial sclerosis and seizure onset. Further measurements will show whether the procedure can be of additional value in the diagnosis of TLE and whether it might improve the definition of eloquent brain areas prior to surgery and have predictive aspects for post surgical outcome (e.g., neuropsychological deficits).