Quantitative analysis of the effect of brainstem shift on surgical approaches to anterolateral tumors at the craniovertebral junction.

Many anterolateral craniovertebral junction (CVJ) tumors can safely be resected using a simple posterolateral approach given the surgical corridor provided by brainstem shift. We sought to study how increasing anterolateral CVJ lesion size affects exposure in the posterolateral and far lateral approaches. Six cadaveric heads were used. A posterolateral approach was performed on one side and a far lateral with one-third condyle resection on the other side. Clival and brainstem exposure and surgical freedom were measured. A balloon catheter was used to simulate 10, 15, and 20mm anterolateral mass lesions. Mean clival exposure was significantly greater with the far lateral approach (197.4 versus [vs] 135.0 mm(2), p=0.03) with no balloon, but this difference disappeared with lesion sizes of 10 mm (246.8 vs 237.9 mm(2), p=0.79), 15 mm (306.7 vs 262.4 mm(2), p=0.25), and 20 mm (360.0 vs 332.7 mm(2), p=0.64). Mean brainstem exposure was significantly greater with the far lateral approach for 0 mm (127.8 vs 65.8 mm(2), p<0.01), 10 mm (129.5 vs 87.5 mm(2), p=0.045), and 15 mm (140.1 vs 97.8 mm(2), p=0.01) lesions. There was no difference at 20 mm (146.7 vs 147.8 mm(2), p=0.97). Medial-lateral surgical freedom was greater with the far lateral approach for all sizes. The results of this study provide insight on one important variable in the decision-making process to select the optimal approach for anterolateral CVJ tumors.