Minimally Invasive Direct Transcondylar Approach to the Foramen Magnum: Surgical Anatomy and Presentation of Two Clinical Cases

Introduction: Surgical approaches to the foramen magnum are usually large procedures with a high potential for associated morbidity and mortality. Minimally invasive approaches offer the same potential benefits while disrupting less tissue, providing patients with less pain and the chance for an earlier recovery. There is evidence that the resection of up to 50% of the occipital condyle does not create instability of the craniocervical junction. We present the surgical anatomy of a direct approach to the foramen magnum through the occipital condyle using a minimally invasive technique, as well as two surgical cases that illustrate the feasibility of the procedure.

Methods: A morphological study was performed in the cadaver laboratory to determine the best surgical corridor to perform a minimally invasive approach to the craniocervical junction. The incision is made at the level of the digastric fissure. A muscle-splitting technique is performed through the use of a minimally invasive retractor (MaXcess, NuVasive Inc.) directed over the occipital condyle. After obtaining institutional board approval and informed consent, the approach was later performed in two patients with tumors located in this region.

Results: Anatomical landmarks were identified to avoid damage of the hypoglossal nerve and the condylar emissary vein during the procedure. The vertebral artery was not an obstacle, and it was not necessary to manipulate it during surgery. Complete tumor removal was possible and no operative complications were noted. There was no secondary mechanical instability of the craniocervical junction after surgery. All neural structures were successfully decompressed.

Conclusions: It is possible to perform a minimally invasive direct transcondylar approach to the foramen magnum. This surgical technique requires deep knowledge of the surgical anatomy of the craniocervical junction and availability of specific instruments for skull base microsurgery. This technique potentially offers lower morbidity and mortality than conventional approaches, because there is no need to manipulate the vertebral artery, which poses a lower risk of hemorrhage.