Muscle Matters: Decoding the Predictive Power of Cervical Muscle Morphology on DCM Surgical Outcomes

Degenerative cervical myelopathy (DCM) is a neurological disorder characterized by spinal cord compression in the neck due to age-related degenerative changes. It is the most common cause of spinal cord dysfunction in adults. The global aging population has resulted in an increase in the prevalence of conditions like DCM, presenting significant challenges to healthcare systems worldwide. Despite being a common condition, there is still much to learn about DCM, including its exact causes, the best ways to predict disease progression, and the most effective treatment strategies. Ongoing research is crucial to improving outcomes for patients with DCM. To address some of these challenges, a new study published in Frontiers in Neurology conducted by PhD candidate Neda Naghdi and Assistant Professor Maryse Fortin from Concordia University in collaboration with Professor James Elliott from University of Sydney and Assistant Professor Michael Weber from McGill University Health Centre and Professor Michael Fehlings from University of Toronto, the authors investigated the predictive value of preoperative cervical muscle morphology on the post-surgical outcomes in patients with DCM. The study also evaluated the relationship between the size, composition, and symmetry of cervical muscles, as observed through magnetic resonance imaging (MRI), and the recovery metrics post-surgery. The study included 171 patients diagnosed with DCM, selected from the Controlled Prospective AOSpine DCM-International cohort study, which comprises multiple international sites. The inclusion criteria were adults (18 years or older) with symptomatic DCM, good quality preoperative MR T2-weighted axial images, and no previous cervical spine surgery while the exclusion criteria included asymptomatic individuals, those with active infections, neoplastic diseases, rheumatoid arthritis, ankylosing spondylitis, or concomitant lumbar stenosis.

The research team used the T2-weighted axial MRI images to measure different parameters including the total cross-sectional area (CSA), functional CSA (FCSA), and the ratio of FCSA to CSA (indicating fatty infiltration) at specific cervical levels. The measurements focused on the multifidus (MF) and semispinalis cervicis (SCer) muscles, both individually and collectively, as well as the broader group of cervical muscles including semispinalis capitis and splenius capitis. They quantified the asymmetry in these muscles, and the relative total CSA (RCSA) was adjusted for inter-individual differences by considering the size of the disk at the level of interest.  The authors evaluated post-surgical outcomes using several scales including the modified Japanese Orthopedic Association (mJOA) score, Nurick Classification, Neck Disability Index (NDI), and SF-36 health survey at 6-month and 12-month intervals post-surgery. The team employed both univariate and multivariate linear regression analyses to explore the relationship between the baseline cervical muscle measurements and post-operative outcomes. They adjusted their analysis for potential covariates like age, body mass index, and sex.

The authors found lower RCSA of MF+SCer, reduced CSA asymmetry of MF+SCer, higher FCSA/CSA ratio for the cervical muscle group, and younger age were significantly associated with higher mJOA scores at both 6 and 12 months post-surgery, indicating less disability. Moreover, greater CSA asymmetry in MF+SCer and lower FCSA/CSA for the cervical muscle group were significant predictors of higher Nurick scores at both follow-up intervals, indicating more disability. Additionally, they reported lower FCSA asymmetry and FCSA/CSA asymmetry of the muscle group, along with greater RCSA MF+SCer, were significant predictors of higher NDI scores, suggesting more neck disability. Furthermore, greater FCSA/CSA asymmetry and CSA asymmetry of MF+SCer were significant predictors of lower SF-36 scores, indicating worse quality of life post-surgery.

The researchers’ study implications are significant and suggests that preoperative assessment of cervical muscle morphology could play a crucial role in predicting surgical outcomes for DCM patients. This new knowledge could significantly impact surgical decision-making, patient counseling, and the development of pre- and post-operative rehabilitation protocols aimed at optimizing muscle condition to enhance recovery. Moreover, the relationship between muscle morphology and functional outcomes in DCM patients aligns with existing literature on the role of cervical muscles in spinal stability and neck function. Furthermore, the findings that fatty infiltration and muscle asymmetry are indicative of worse outcomes post-surgery are particularly compelling, highlighting the need for a comprehensive preoperative evaluation that includes an assessment of muscle health. The new study also sheds light on the potential impact of age on surgical outcomes, with younger patients showing better recovery metrics. This aspect highlights the complex interplay between degenerative changes associated with aging and the capacity for post-surgical recovery, necessitating a more careful approach to the management of older patients with DCM. In conclusion, the study by Assistant Professor Maryse Fortin and colleagues successfully establishes a link between preoperative cervical muscle morphology and post-surgical outcomes, which paves the way for more personalized and effective treatment strategies. Future research should continue to explore the role of cervical muscle health in DCM, including the potential benefits of targeted muscle strengthening and rehabilitation interventions as part of enhanced recovery after surgery protocols.