Microsurgical Anatomy of the Insular region, Operculoinsular association fibers and its neurosurgical application review

OBJECTIVE: To analyze the three-dimensional relationships of the operculoinsular compartments, using standard hemispheric and white matter fiber dissection and review the anatomy of association fibers related to the operculoinsular compartments of the Sylvian fissure and the main white matter tracts located deep into the insula. The secondary aim of this study was to improve the knowledge on this complex region to safely address tumor, vascular, and epilepsy lesions with an integrated perspective of the topographic and white matter fiber anatomy using 2D and 3D photographs. METHODS: Six cadaveric hemispheres were dissected. Two were fixed with formalin and the arteries were injected with red latex dye; the remaining four were prepared using the Kingler method and white fiber dissections were performed. RESULTS: The insula is located entirely inside the Sylvian fissure. The topographic hemispheric anatomy, Sylvian fissure, opercula, surrounding sulci and gyri, as well as the M2, M3, and M4 segments were identified. The anatomy of the insula, with the sulci and gyri and the limiting sulci, were also identified and described. The main white matter fiber tracts of the operculoinsular compartments of the Sylvian fissure as well as the main association and commissural fibers located deep in the insula were dissected and demonstrated. CONCLUSIONS: Complementing topographic anatomy with detailed study of white matter fibers and their integration can help the neurosurgeon to safely approach lesions in the insular region, improving postoperative results in the microsurgical treatment of aneurysmal lesions, insular tumors, or epilepsy surgery.