Introduction: The deep extensor neck muscles (DENM) are often impaired in patients with cervical disorders. This study aimed to examine the relationship between morphological changes of the DENM in patients with degenerative cervical myelopathy (DCM) and the level of maximum spinal compression and canal compromise.

Materials/Methods: A total of 171 patients from a Prospective DCM-International cohort study database were included in this study. Total cross-sectional area (CSA), functional CSA (fat free area, FCSA), ratio of FCSA/CSA (fatty infiltration) and asymmetry of the MF+SCer together and DENM as a group were obtained bilaterally from axial T2-weighted MR images at mid-disc, at the level of maximum cord compression and the level below. The level and degree maximum spinal cord compression (MSCC) and maximum canal compromise (MCC) was determined using the following formulas MSCC= [1 −di (da + db)/ 2] × 100, and MCC = [1 −Di (Da + Db)/ 2] × 100 as defined by Fehlings et al. The relative percent asymmetry in CSA, FCSA and FCSA/CSA was calculated using: [(L − S)/L] x100, where L is the larger side, and S is the smaller side. The relationship between the muscle parameters of interest, MSCC and MCC was assessed using multivariate linear regression models.

Results: Greater MF+Scer fatty infiltration was associated with greater MCC (P= 0.025) and MSCC (p=0.049) at the same level. Greater asymmetry in MF+SCer CSA was also associated with greater MCC (p=0.006). Similarly, greater asymmetry in FCSA and FCSA/CSA of the entire DENM group was associated with greater MCC (p=0.011, p=0.013). There was no significant association between muscle measurements obtained at the level below the level of maximum compression, MCC and MSCC.

Conclusion: Greater MCC is associated with increased fatty infiltration and greater asymmetry of the DENM in patients with DCM. Our findings also suggest that MCC is a better indicator of cervical muscle morphological changes than MSCC.