Relationship between cervical muscle morphology evaluated by MRI, cervical muscle strength and functional outcomes in patients with degenerative cervical myelopathy.

ABSTRACT

BACKGROUND: Cervical muscle alterations have been reported in patients with chronic neck pain, but the assessment of muscle morphology and strength has been overlooked in patients with degenerative cervical myelopathy (DCM). OBJECTIVES: This study aimed to investigate the relationship between cervical muscle degenerative changes observed on MRI, muscle strength and symptoms severity in patients diagnosed with DCM. DESIGN: Observational study. METHODS: Cervical muscle measurements of total cross-sectional area (CSA), functional CSA (fat free area, FCSA) and ratio of FCSA/CSA (e.g. fatty infiltration) were obtained from T2-weighted axial MR images from C2-C3 to C6-C7 in 20 patients. Muscle strength was assessed manually using a microFET2 dynamometer. The association between cervical muscle morphology parameters, muscle strength, symptoms severity and functional status was investigated. RESULTS: Greater mean CSA and FCSA was associated with greater overall muscle strength. The mean FCSA explained 37%, 76%, 39%, 20% and 65% of the total variance in flexion, extension, right-side bending, left-side bending and overall muscle strength, respectively. The mean ratio of FCSA/CSA was not significantly associated with cervical muscle strength in any direction. However, greater FCSA/CSA ratio (e.g. less fatty infiltration) was associated with lower disability score (p = 0.02, R2 = 0.20). CONCLUSIONS: Cervical muscle lean muscle mass was positively associated with cervical muscle strength in patients with DCM. Moreover, greater fatty infiltration in the cervical extensor muscles was associated with lower functional score. Such findings suggest that clinicians should pay greater attention to cervical muscle morphology and function in patients with DCM.