Quantitative Analysis of Variants of the Far-Lateral Approach

BACKGROUND The rationale for choosing between the condylar fossa and transcondylar variations of the far-lateral approach requires understanding of the relationships between the occipital condyle, jugular tubercle, and hypoglossal canal. OBJECTIVE We examined the anatomic relationship of these 3 structures and analyzed the effect that changes in these relationships have on the surgical exposure and angle of attack for these 2 approaches. METHODS Anatomic measurements of 5 cadaveric heads from 3-dimensional computed tomographic scans were compared with direct measurements of the same specimens. The condylar fossa and transcondylar approach were performed sequentially in 8 of 10 sides. Surgical exposure and angle of attack were measured after each exposure. RESULTS The jugular tubercle (JT) angle (JTA) measures the angle formed by reference points on the condyle, hypoglossal canal, and JT. When the JT and occipital condyle are not prominent (JTA > 180°), the transcondylar approach does not significantly increase petroclival or brainstem exposure compared with the condylar fossa approach; however, it does significantly increase the angle of attack to the junction of the posterior inferior cerebellar and vertebral arteries and the surgical angle for the medial part of the JT (P < .05). CONCLUSION The condylar fossa and transcondylar approaches provide similar exposures of the petroclivus and brainstem when the JT and occipital condyle are not prominent (JTA > 180° on 3-dimensional computed tomographic). However, for lesions below the hypoglossal canal, the transcondylar approach is preferred because it significantly increases the angle of attack.