C2 Nerve Root Preservation during Posterior Fixation for Instability secondary to Congenital Craniovertebral Junction Anomalies: Feasibility Factors and Related Outcomes.

OBJECTIVE Patients with instability due to congenital craniovertebral anomalies often have complex C1-C2 osseo-vascular anomalies. C2 nerve root sacrifice has been described to address such difficult anatomy during posterior C1-C2 fixation, and has its own downsides. Its preservation as a recent alternative poses greater surgical challenge, and the considerations differ from other etiologies of craniovertebral junctional instability; the pertaining outcomes have been scarcely studied. The objective was to prospectively determine the feasibility and outcomes related to C2 nerve-root preservation in congenital atlantoaxial dislocation (CAAD) patients following posterior C1-C2 fixation. METHODS In this observational study, 63 patients (126 nerve roots) with CAAD following posterior fixation were prospectively assessed. Underlying osseo-vascular anomalies affecting the feasibility of C2 nerve root preservation, and C2 nerve related dysfunction at 12-month follow-up have been analyzed. RESULTS The overall C2 nerve root preservation rate was 89.7%. Even in the presence of extreme joint obliquity/spondyloptosis and anomalous vertebral artery, it was feasible in about three-fourths. Post-preservation, 28.3% patients developed new-onset C2 nerve root dysfunction: neuralgia in 2, dysesthesia in 6, and hypoesthesia/ paresthesia- 9. Notably, the symptoms were not disabling in the majority. CONCLUSIONS In most patients with CAAD, C2 nerve root preservation is feasible despite an aberrant bony and vascular anatomy. A few patients after nerve root preservation develop related symptoms that are conservatively manageable, with no significant adverse consequences. Given the current controversy on C2 nerve sacrifice-related outcomes in literature, we favor an attempt at C2 nerve root preservation.