MICROSURGICAL ANATOMY OF THE AMYGDALOID BODY AND ITS CONNECTIONS

Background: The amygdaloid body (AB) is an aggregate of grey matter nuclei of diencephalic origin located in the uncus of the temporal lobe, which presents extensive connections within the limbic system, with the thalamus and neocortex. When performing surgical approaches to the temporomesial structures, a detailed knowledge of this anatomical region and its connections is paramount in order to avoid relevant complications. The purpose of this study is to improve our understanding of the topographic anatomy of the AB and its afferent and efferent bundles. Methods: Nine cerebral hemispheres were dissected by using white matter dissection technique originally described by Joseph Klingler. We investigated the topographic anatomy of the AB and its connections. For each step of the dissection anaglyphic pictures were taken. Results: The AB is located in the antero-medial part of the uncus of the temporal lobe and presents a posterior or ventricular portion abutting the temporal horn and an anterior portion embedded in the uncus. The uncinate fascicle runs cranially to the AB. The stria terminalis is the main dorsal efferent bundle and runs in the roof of the temporal horn and connects the AB with the septal region. The anterior commissure runs dorsally and connects reciprocally the ABs of each temporal lobe. Ventrally, the amygdalofugal pathway connects the AB with the rostral portion of the diencephalon. The inferior thalamic peduncle presents some fibers connecting the AB with the mediodorsal nucleus of the thalamus. The Meyer’s loop runs in the roof of the temporal horn posterior to the inferior thalamic peduncle. Discussion: The analysis of the three-dimensional anatomy of the AB provides relevant information when planning a surgical approach to the temporomesial region. Surgical treatment of lesions located in the mesial temporal lobe may result in injury of the afferent and efferent fiber bundles of the AB. When approaching lesions of the temporal horn, the site of corticotomy and the resultant surgical corridor are crucial in hazarding selective lesions of AB connections. The approach through the middle temporal gyrus hazards injury of the Meyer’s loop, the inferior thalamic peduncle, and the stria terminalis. The Transsylvian approach can lead to the injury of the uncinate fascicle, the ventral amygdalo-fugal pathway and the Meyer’s loop. Conclusions: The knowledge gained by studying the AB and its connections is useful to accomplish appropriate surgical planning and to understand the repercussions of surgical treatment of lesions affecting this region.