Introduction: The far-lateral approach (FLA) is often used to access pathologies near the vertebral and posterior inferior cerebellar arteries (VA-PICA). The extent of craniotomy of this approach has not yet been quantified. We quantitatively analyzed six sequential steps of the FLA to help plan the extent of craniotomy and additional bone work that might be required to gain the necessary exposure.
Methods: Five silicone-injected cadaveric heads were dissected bilaterally. A modified small FLA (msFLA) and a classic large FLA (clFLA) were performed sequentially on both sides of all 5 heads. A frameless navigational system was used to quantify the angle of attack for the origin (T1) and lateral medullary segment (T2) of PICA and the surgical area of exposure above and below the vagus nerve (CN X).
Results: The total area of exposure above CN X increased significantly (p<0.05) from the msFLA to clFLA. However, the surgical exposure area below CN X, which was the practical working area for the VA-PICA region, 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 PICA.
Conclusions: While considering the surgical procedures in the VA-PICA region, the msFLA offered a similar practical surgical working area and similar angles of attack when compared to 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.
Patient Care: This will allow surgeons to tailor the far lateral approach, so that they can use a smaller craniotomy instead of the classic large far lateral craniotomy, therefore preventing operative morbidity.
Learning Objectives: By the conclusion of this session; participants should be able to: 1) Describe the importance of the modified small far lateral approach, 2) Discuss the various pathologies that can be treated with either the classic far lateral approach and the modified far lateral approach.