Is amygdalohippocampectomy really selective in medial temporal lobe epilepsy? A study using positron emission tomography with (18)fluorodeoxyglucose

Purpose: Selective amygdalohippocampectomy (SAH) is a surgical technique ef fective for the treatment of medial temporal lobe epilepsy, which selective ly removes the epileptogenic hippocampus and amygdala but spares the tempor al neocortex. However, the benefit of SAH in terms of functional outcome is debated. In this study, we aimed to assess the metabolic consequences of S AH. Methods: Volumetric magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography (PET) studies were performed in nine patients with medial temporal lobe epilepsy associated with hippocampal sclerosis b efore and after SAH. Regions of interest were delineated on MRIs and then r eplaced on PET images using an automatic 3D image registration. We calculat ed absolute metabolic rates of glucose and normalized metabolic values in e ach region of interest. Results: The comparison between preoperative and postoperative metabolic va lues showed a statistically significant worsening of the hypometabolism on the ipsilateral temporal pole on the superior and the hippocampal levels (p < 0.05 and 0.0045, respectively). A postoperative increase of the metaboli c activity also was noted in the contralateral anterior hippocampus (p < 0. 05) and the orbitofrontal cortex bilaterally (p < 0.002 and 0.001, respecti vely) Conclusions: SAH functional benefit is controversial. SAH worsened signific antly the hypometabolism of a temporal structure that was not surgically re moved (i.e., the temporal pole), and it improved postoperatively the metabo lic activity in the contralateral hippocampus and the orbitofrontal cortex. Whether this postoperative improvement is linked to the selectivity of the surgical procedure must be further clarified.