The Contralateral Transfalcine Approach: An Anatomic Study Quantifying Its Superior and Lateral Limits of Exposure

BACKGROUND AND OBJECTIVES: Contralateral transfalcine approaches are widely used for interhemispheric/mesial cortical pathologies, even those extending beyond 2 cm lateral from the midline. Nevertheless, the superior limit of contralateral exposure through this approach is not defined. This anatomic study aims to characterize the maximal superior and lateral limits of contralateral exposure using a contralateral transfalcine approach. METHODS: Interhemispheric approaches in the anterior, middle, and posterior-thirds of the interhemispheric fissure were performed in 10 cadaveric head specimens. Rectangular falcine incisions were made and carried maximally superiorly. The contralateral hemisphere was maximally laterally resected from the superior point of visualization down to the level of the corpus callosum. Distances between the most superior point of visualization of the contralateral hemisphere and the superficial point of its cortex and between the midline and the most lateral point of visualization at the level of the corpus callosum were measured and are reported as averages. RESULTS: At the anterior-third of the interhemispheric fissure, the superior point of visualization was 4.8 mm inferior to the cortex. The lateral distance of visualization at the genu of the corpus callosum was 22.9 mm. At the middle-third, the superior point of visualization was 9.7 mm inferior to the cortex. The lateral distance visualized at the body of the corpus callosum was 22.4 mm. At the posterior-third, the superior point visualization of the mesial contralateral hemisphere was 12.6 mm inferior to the cortex. The lateral distance visualized at the splenium of the corpus callosum was 21.3 mm. CONCLUSION: Using the contralateral transfalcine approach, the superior limit of contralateral exposure progressively decreases more posteriorly along the interhemispheric corridor-ranging from 4.8 mm inferior to the cortex in the anterior-third to 12.6 mm inferior to the cortex in the posterior-third. The contralateral optimal view of exposure increases deeper along the interhemispheric corridor.