Quantitative Anatomical Study of Tailored Far-Lateral Approach for the VA-PICA Regions.

Objective The extent of the far-lateral approach (FLA) has not yet been quantified for the region of the vertebral and posterior inferior cerebellar arteries (VA-PICA). We quantitatively analyzed six main sequential steps of the FLA. Methods A modified small FLA (msFLA) and a classic large FLA (clFLA) were performed sequentially on both sides of five cadaveric heads. A frameless navigational system was used to quantify the angle of attack for the origin (T1) and lateral medullary segment (T2) of the PICA and the surgical area of exposure above and below the vagus nerve (cranial nerve [CN] X). Results The total area of exposure above CN X increased significantly (p < 0.05) from the msFLA to the clFLA. However, the surgical exposure area below CN X did not change (p > 0.05). C1 hemilaminectomy increased (p < 0.05) the vertical angle of attack, and drilling the posteromedial third of the occipital condyle increased (p < 0.05) the horizontal angle of attack to the origin of the PICA. Conclusions For the VA-PICA region, the msFLA offered a similar practical surgical working area and similar angles of attack when compared with the clFLA. The FLA should be tailored based on the location, size, and pathology of lesions and on the exposure required for effective surgical treatment.