Congenital Cervical Fusion as a Risk Factor for Development of Degenerative Cervical Myelopathy

BACKGROUND: Congenital fusion of cervical vertebrae, including Klippel-Feil syndrome (KFS), is a suspected risk factor for development of degenerative cervical myelopathy (DCM). We aimed to establish prevalence and degenerative patterns of congenital cervical fusion (CCF) among a global cohort of patients with DCM. METHODS: Data from 3 prospective DCM studies were merged, including clinical data for 813 patients and imaging for 592 patients. CCF was diagnosed by presence of fused cervical vertebrae without signs of degenerative fusion. A wasp-waist sign was used to define a KFS subgroup. Characteristics of patients with CCF and the KFS subgroup were compared with the remainder of patients with DCM. RESULTS: Twenty-three patients with CCF (14 KFS) were identified, indicating a prevalence of 3.9% (2.4% KFS). Patients with CCF were older (P=0.02), had more operated levels (P=0.01), had higher rates of ossified posterior longitudinal ligament (P=0.02), and demonstrated worse degenerative changes at C3-4, including spinal cord compression (P=0.002) and T-2 weighted image T2WI signal hyperintensity (P=0.04). Levels adjacent to fusions showed a trend toward increased spinal cord compression (P=0.09), with fusions at C3-4 or above showing cord compression below in 9 of 10 patients, fusions at C5-6 or below having cord compression above in 8 of 8 patients, and fusions at C4-5 showed cord compression above and below in 2 of 2 patients. CONCLUSIONS: The prevalence of CCF and KFS is higher in DCM than for the general population, suggesting that these patients are predisposed to DCM development. Patients with CCF also have an altered pattern of degenerative changes, seemingly related to adjacent segment degeneration that preferentially affects midcervical levels.