Surgical Resection of Amygdala and Uncus.

The amygdala and uncus are located close to important neurovascular structures. We describe a safe technique for resection of amygdala and uncus. Under general anesthesia, the patient is positioned supine, with the head rotated approximately 20 degrees to the unoperated side and slightly extended. By using a trans-anterior T1 subpial approach, the inferior horn of the lateral ventricle is opened, and hippocampectomy is performed. We treat an imaginary plane formed by the inferior circular sulcus of the insula, the endorhinal sulcus, and the inferior choroidal point as the upper border of amygdalar resection. After confirming the position of the inferior choroidal point, the border between the temporal stem and uncus is exposed from anterior to posterior. This border is continuous with the endorhinal sulcus. By exposing the endorhinal sulcus, the anterior choroidal artery and optic tract can be visualized. The amygdala is disconnected through complete exposure of the endorhinal sulcus to the inferior choroidal point. After the lateral side of the uncus is disconnected, the amygdala and uncus are removed en bloc. Since April 2014, we have used the described procedure to remove amygdalar-uncal lesions in 15 patients. The lesion was completely removed in all cases without complications. Histological specimens were obtained in all cases. Our procedure enables safe and complete removal of amygdalar-uncal lesions. Imagining the plane formed by the inferior circular sulcus, inferior choroidal point, and endorhinal sulcus is essential for complete removal of the lesion and for preserving important structures.

Fetal sulcation and gyrification in common marmosets (Callithrix jacchus) obtained by ex vivo magnetic resonance imaging.

The present study characterized fetal sulcation patterns and gyrification in the cerebrum of the New World monkey group, common marmosets, using a 3D T2-weighted high-resolution anatomical magnetic resonance imaging (MRI) sequence from the fixed brain at 7-tesla ex vivo. Fetal sulcation in the marmoset cerebrum began to indent the lateral fissure and hippocampal sulcus in gestational week (GW) 12, and then the following sulci emerged: the callosal and calcarine sulci on GW 15; the superior temporal sulcus on GW 17; and the circular and occipitotemporal sulci on GW 18. The degree of cortical convolution was evaluated quantitatively based on 2D MRI slices by the gyrification index (GI) and based on 3D MRI data by sulcation index (SI). Both the mean GI and SI increased from GW 16, and were closely correlated with the cortical volume and the cortical surface area during fetal periods (their correlation coefficients marked more than 0.95). After birth, both the mean GI and SI decreased slightly by 2years of age, whereas the cortical volume and surface area continuously increased. Notably, histological analysis showed that the outer subventricular zone (oSVZ) in non-sulcal regions was thicker than that in the presumptive calcarine sulcal region on GW 13, preceding the infolding of the calcarine sulcus. The present results showed definite sulcal infolding on the cerebral cortical surface of the marmosets, with similar pattern and sequence of their emergences to other higher-order primates such as macaques and humans. Differential expansion of the oSVZ may be involved in gyral convolution and sulcal infolding in the developing cerebrum.