Magnetic Resonance Imaging Anatomy for Surgical Application in Subtemporal Selective Amygdalohippocampectomy

ABSTRACT

Although subtemporal amygdalohippocampectomy is the ideal approach for pure mesial temporal lobe epilepsy from the view point that it can resect amygdala, hippocampusis, and parahippocampal gyrus selectively, this approach has not gained wide popularity due to shortcomings such as temporal lobe retraction and possible injury to temporal lobe draining veins. We analized surgical anatomy on MRI scan of 20 persons for the purpose of modifing the subtemporal approach to overcome the inherent shortcomings. The distance from temporal pole to anterior margin of temporal horn was 29.8+/-5mm(range, 28.5-31mm). Anterior margin of hippocampus was located 1.8+/-9mm(range, 1-3mm) anterior to dorsum sella. The length of hippocampus to the level of posterior margin of cerebral peduncle was 25.6+/-4mm. External auditary meatus divided the hippocampus, from anterior to the level of posterior margin of cerebral peduncle, in the ratio of 1.52 1. On the coronal image through interpeduncular cistern, the distance between lateral margin of temporal lobe and collateral sulcus was 40.6+/-.3mm(37-45mm). On the coronal image through interpeduncular cistern and through the external auditary meatus, the height from temporal base to the choroidal fissure was 30.0+/-.7mm and 21.3+/-.5mm, respectively, and the angle between temporal base line and a line from collateral sulcus to choroidal fissure was 45.7+/-.6 degree and 33.2+/-.9 degree, respectively. In conclusion, our results indicate that external auditary meatus(EAM) is anatomical landmark for subtemporal amygdalohippocampectomy, and skull base approach focused on either EAM or anterior to EAM is necessary to minimize morbidity due to temporal lobe retraction and draining vein injury.