1 Department of Health, Kinesiology & Applied Physiology, Concordia University, Montreal, QC, Canada.
2 The Kolling Institute, The University of Sydney, Sydney, NSW, Australia.
3 The Northern Sydney Local Health District, Royal North Shore Hospital, St Leonards, NSW, Australia.
4 Montreal General Hospital Site, Department of Orthopedic Surgery, McGill University Health Centre, Montreal, QC, Canada.
5 Department of Neurosurgery and Spinal Program, University of Toronto, Toronto, ON.
6 PERFORM Centre, Concordia University, Montreal, QC, Canada.
7 Centre de Recherche Interdisciplinaire en Réadaptation (CRIR), Montréal, QC, Canada.

Study design: Cross-sectional study.

Objectives: To examine the relationship between morphological changes of the deep extensor neck muscles in patients with degenerative cervical myelopathy (DCM) and the level of maximum spinal cord compression (MSCC) and canal compromise (MCC). A secondary objective was to examine the relationship between muscle morphological changes with neck pain and functional scores related to neck pain and interference.

Methods: A total of 171 patients with DCM were included. Total cross-sectional area (CSA), functional CSA (fat free area, FCSA), ratio of FCSA/CSA (fatty infiltration) and asymmetry of the multifidus (MF) and semispinalis cervicis (SCer) together, and cervical muscle as a group (eg, MF, SCer, semispinalis capitis, splenius capitis) were obtained from T2-weighted axial MR images at mid-disc, at the level of maximum cord compression and the level below. The relationship between the muscle parameters of interest, MSCC, MCC and functional scores including the Neck Disability Index (NDI) was assessed using multivariate linear regression models, adjusting for age, body mass index and sex.

Results: Greater MF + Scer fatty infiltration was associated with greater MCC (P = .032) and MSCC (P = .049) at the same level. Greater asymmetry in MF + SCer CSA was also associated with greater MCC (P = .006). Similarly, greater asymmetry in FCSA and FCSA/CSA of the entire extensor muscle was associated with greater MCC (P = .011, P = .013). There was a negative association between asymmetry in FCSA MF + SCer, FCSA/CSA MF + SCer and FCSA/CSA group muscles with NDI score at the level below.

Conclusion: Greater MCC is associated with increased fatty infiltration and greater asymmetry of the deep cervical muscles in patients with DCM. A negative association between muscle asymmetry and NDI scores was also observed which has implications for clinical prediction around axial neck pain.