Lateral approach to anterolateral tumors at the foramen magnum: Factors determining surgical procedure

OBJECTIVE: We discuss and evaluate surgical strategies and results in 42 patients with a variety of tumors involving the anterior and anterolateral foramen magnum and present factors affecting the degree of resection and patient outcomes. We describe our surgical techniques for resection of these tumors via the lateral approach, including consideration for occipital condylar resection and vertebral artery management. METHODS: A retrospective analysis was performed of 42 surgically treated patients with tumors involving the anterior and anterolateral foramen magnum. Patients received treatment between 1991 and 2002; patients' files, operative notes, and pre- and postoperative imaging studies were used for the analysis. RESULTS: The female-to-male ratio was 28:14. Mean patient age was 47 years. Pathological entities comprised 18 meningiomas, 12 chordomas, 3 glomus tumors, 3 schwannomas, and 6 miscellaneous tumors. We mobilized the vertebral artery at the dural entry point in all patients with meningiomas. The vertebral artery was mobilized at the C1 transverse foramen for the majority of extradural tumors. Partial condyle resection was performed in eight meningiomas and five extradural tumors. Complete condyle resection was required in 12 cases, including 9 chordomas, 2 carcinomas, and 1 bone-invading pituitary adenoma. Thirteen patients required occipitocervical fusion after tumor resection. CONCLUSION: In anterior or anterolaterally located foramen magnum tumors, we think the extreme lateral or far lateral approach affords significant advantages. Vertebral artery mobilization and occipital condyle resection may be needed depending on the extent and location of the foramen magnum tumor and its specific pathological characteristics. Tumor invading the occipital condyle or significant condylar resection may cause occipitocervical instability and require fusion.