Is Anatomic Reduction Better Than Partial Reduction in Patients with Vertical Atlantoaxial Dislocation?

OBJECTIVE: To describe lower cranial nerve (CN) palsy following vertical overdistraction when performing occipitocervical fusion (OCF) to treat vertical atlantoaxial dislocation (AAD) and basilar invagination (BI) and investigate its possible causes. METHODS: We report 4 cases with vertical AAD and BI who presented postoperatively with neurogenic dysphagia, dysarthria, and bucking after undergoing anatomic reduction. RESULTS: Patients underwent revision surgery to achieve partial reduction and demonstrated remarkable recovery of CN IX, X, and XI deficits. CONCLUSIONS: Performing OCF in the overdistraction position to treat vertical AAD may caudally displace the brainstem relative to the cranial base, resulting in traction injury to the CN IX, X, and XI where they exit the skull base through the jugular foramen.