A Technical Guide for Fiber Tract Dissection of the Internal Capsule.

AIM: Dissection of white fibers is important in identifying detailed neuroanatomical relationships. With tractrography it is possible to transport and apply this knowledge in a practical way to treat many diseases involving the white matter. MATERIAL AND METHODS: The Klingler method, subsequently disseminated by Türe with slight modifications was used. RESULTS: We review some historical aspects of white fibers and provide a guide for dissection of the internal capsule. The removal of gray matter allowed us to obtain a view of the white matter. We removed all U-shaped fibers to expose the insular cortex. The cortex of the insular lobe was removed, which exposed the extreme capsule. The removal of the claustrum exposed the external capsule, which covers the lentiform nucleus, specifically the putamen. During dissection, removing some fibers of the external capsule produced windows in which the putamen could be medially visualized. Since the internal capsule lies medial to the lentiform nucleus, it was necessary to remove the nucleus in order to expose the internal capsule. We identified five regions of the internal capsule: the anterior limb, genu, posterior limb, and sublenticular and retrolenticular parts. Finally, we determined that the fibers of the corona radiata condense into the internal capsule at the level of the superior border of the lentiform nucleus. CONCLUSION: Knowledge gained with the cadaveric fiber dissection technique can be applied in microsurgical practice and can be used to evaluate the surgical treatment for different tumors and vascular malformations.

Internal capsule: Seth of dissectors for an integral boarding of its fibers.

INTRODUCTION: Classically, the morphologic study of the internal capsule (IC) is made by two cuts: the coronal of Charcot and the axial of Fleschig. Recent neuroradiologic studies and clinical investigations contribute to the observation in the non-invasive form of this region. OBJECTIVE: The present work tries to complement the study of this important anatomical region, demonstrating it in integral and three-dimensional form. For that reason, the channeled soundings and instruments of manicurist and odontology were modified, and were conformed to a Seth of dissectors designed specifically to approach the IC. Each dissector presents particular characteristics, which allows the delicate dissections of the different anatomical structures to be made. MATERIALS AND METHODS: Twenty encephala of adult corpses were used for this investigation, fixed with a solution of formol to 10% in distilled water. They were approached at the external face of the cerebral hemisphere at level of the lateral fissure. The middle cerebral artery and the insula lobe were dissected and extirpated using the dissector no. 1, exposing the extreme capsule. The dissector no. 2 was used to dissect the fibers and the extreme capsule was extracted jointly with the claustrum, demonstrating the external capsule. The fibers were dissected using the dissector no. 3, thus exposing the lentiform nucleus. Then, the external face of the nucleus was delimited with the dissector no. 4 and then underwent exeresis, to allow for the entry of the genu of the IC. The genu constituted nervous fibers, laid out vertically and perpendicular to the greater axis the nucleus before mentioned. The fibers were dissected with the dissector no. 5, also appreciating the route of the lenticuloestriadas arteries that irrigate the region in the study. Using the dissector no. 6, nervous fibers of the corona radiata were dissected, as well as the short arciformes fibers and the endings in the cerebral cortex. Lastly, the dissector no. 7 was used to dissect the fibers of the pyramidal route and their route by the cerebral trunk, from above to below. CONCLUSION: With the use of the presented instruments, a selective boarding of the IC was obtained, and thanks to the specific characteristics of each dissector, the different anatomical structures related to the IC can be approached with facility. Also, the nervous fibers that compose it can be dissected, which expose the IC in an integral and three-dimensional way.