Abstracts

Functional magnetic resonance imaging (fMRI) of limbic mesial temporal lobe structures may help to taylor epilepsy surgery in patients with refractory mesial temporal lobe epilepsy (MTLE). We have shown earlier that a simple fMRI memory paradigm (Roland[rsquo]s Home Town Walk) well lateralizes the side of MTLE by activation of the parahippocampal gyri (Jokeit et al. Neurology 2001;57:1786). In addition, information about the integrity or dysfunction of the amygdala may influence the decision about the anterior extension of the resection. Although only in a minority of surgical patients, postoperative deficits in social and emotional cognition and behaviour can occur. We present data showing that activation of amygdala and parahippocampus can be dissociated in patients with MTLE by appropriate fMRI tasks. Five male patients (aged 25 to 45) with refractory MTLE (three left-sided) were investigated. Three patients had hippocampal sclerosis, the others a neoplasia or cavernoma. Using BOLD fMRI, we measured language related activity by a verbal fluency task, parahippocampal activity by Roland[rsquo]s Home Town Walking Task, and amygdala activity. Amygdala activation was induced by presentation of scenes from thriller and horror movies showing animated fearful faces. This paradigm has before been validated in fifteen healthy controls (10 males, 5 females, aged 23-57). All subjects elicited bilateral amygdala activation (p[lt].001). Reproducibility of the paradigm was demonstrated by restudying 5 of the control subjects after one week. Activation patterns were reproducible and the activation intensity did not differ significantly over both measurements. All patients predominantly activated left hemisphere regions during a verbal fluency task and demonstrated significant parahippocampal and amygdala activity. In three patients contralateral amygdalar and parahippocampal activity was higher compared to ipsilateral activity. In one patient with right-sided MTLE and questionable hippocampal sclerosis a comparable activity of both amygdala was detected while parahippocampal activity was asymmetric corresponding to the side of MTLE. In one patient with left-sided MTLE and a paraamygdala neoplasia only contralateral activity of the amygdala was detected while parahippocampal activity was symmetric. In three out of five patients parahippocampal and amygdalar activity were asymmetric corresponding to the side of MTLE. Two patients, however, demonstrate a double dissociation of amygdala and parahippocampal activation.
In patients with MTLE, the use of two simple paradigms allows an individual dissociation of amygdalar and parahippocampal activation within limbic mesial temporal lobe structures. The prognostic value of this information for surgery and counseling of patients has to be evaluated in prospective studies. (Supported by Novartis Pharma AG Schweiz)