Technique of C2 Nerve Root Preservation in the Presence of Anomalous Vertebral Artery in Atlantoaxial Operations

While accessing the C1-C2 joint during posterior atlantoaxial fixation, the C2 nerve root along with its perineural venous plexus remains an obstacle for a panoramic visualization of the entry point of the C1 lateral mass and joint preparation. Therefore, many surgeons frequently advocate its intentional sectioning during this approach, with no related major complications.1,2 However, this sectioning has at times been associated with symptoms such as hypoesthesia, numbness, dysesthesia, and neuropathic ulcers.3 Thus C2 nerve root preservation during posterior approach for atlantoaxial dislocation (AAD) could potentially avoid such consequences.4 Its preservation has been described for AAD cases with relatively normal C1-C2 joint anatomy with no osseovascular abnormalities.2 In contrast, attempt at C2 nerve root preservation in patients with congenital AAD harboring bony and vascular anomalies poses a greater challenge owing to a restricted operative space and the potential for perineural venous bleeding during dissection. This is more so for young neurosurgeons in the initial part of their learning curve. Video 1 details the technique of C2 nerve root dissection and preservation in a case of congenital AAD with an anomalous vertebral artery (VA). Computed tomography (CT) of this 30-year-old male patient with spastic quadriparesis showed AAD/basilar invagination with an assimilated C1 -arch and right anomalous VA on CT angiography. He underwent C1-C2 joint manipulation and short-segment fixation. At 1-year follow-up, the patient's limb weakness had improved and CT showed good bony fusion. The salient operative steps involve gentle teasing and dissection of perineural soft tissues above and below the nerve root; the key to minimize venous bleeding is to dissect, coagulate, and divide them sequentially. A thorough release of the perineural soft tissues allows adequate nerve root mobilization, which in turn provides clear visualiza-tion of the C1-C2 joint space, preventing an undue nerve stretching during the C1 -lateral mass screw insertion. The anomalous VA usually lies anterior to the C2 nerve root, and careful imaging evaluation allows its anticipation.3 We do not prefer the easy alternative of C2 nerve root sacrifice because of its inherent complications we noticed in our earlier clinical practice.3