Introduction: Cervical spondylotic myelopathy (CSM) is among the most common spinal cord disorders of the elderly. Muscle fat infiltration (MFI), the pathological infiltration of fatty tissue into muscle, is known to contribute to pain and disability following in a variety of neurologic and spinal pathologies [1-7], but has never been studied in patients with CSM. We examined the relationship between MFI and clinical disability from CSM.

Methods: We prospectively enrolled nine CSM patients and five aged-matched controls to undergo MRI imaging of the cervical spine with MFI. A 3 Tesla, 3 dimensional dual-echo gradient echo acquisition was performed to collect fat and water data for the neck multifidi muscles (C3–C7) to calculate MFI. A blinded investigator manually traced regions of interest for each of the bilateral multifidii muscles from C3 to C7 on fat-water MRI images to calculate MFI percentages. Nurick scores and modified Japanese Orthopedic Association scores were collected for all patients.

Results: CSM patients and controls were equivalent with respect to age, height, weight, gender, race, smoking status, and employment status. CSM patients and controls differed with respect to both mJOA scores (14.6±0.6, 18.0±0.0, p=0.0017) and Nurick scores (1.9±0.3 v. 0.0±0.0, p=0.0008). MFI was higher in patients with CSM than in controls (31.7% v. 24.6%, respectively, p=0.0178). MJOA scores correlated linearly with MFI (R=0.542, p=0.0453). Higher MFI was associated with increased disability on the Nurick scale (p=0.0371).

Conclusions: Cervical spondylotic myelopathy is associated with increased MFI of the multifidus muscles, which play a critical role in biomechanical stability of the spine [8]. MFI is correlated with clinical disability, as measured by mJOA and Nurick scores. Spinal injury in CSM may lead to muscle fat infiltration, exacerbating the disability associated with the disease.

Patient Care: Although surgical techniques continue to advance and improve care, nearly 40% of CSM patients undergoing surgery achieve less than a 50% recovery using common clinical outcome metrics. As CSM is common in neurosurgical practice, a more detailed understanding of factors contributing to disability and outcomes in CSM is warranted. Knowing that MFI contributes to disability in CSM can allow providers to tailor care accordingly, including minimizing muscle dissection of the affected musculature and physical therapy exercises that are effective in addressing MFI.

Learning Objectives: • Muscle fat infiltration (MFI), the pathological infiltration of fatty tissue into muscle, may contribute to pain and disability in patients with CSM. • Patients with CSM have higher levels of MFI than age-matched controls. • Increased MFI of the multifidus muscles is associated with clinically significant changes in mJOA and Nurick scores. • Spinal injury in CSM may lead to secondary muscle loss and muscle fat infiltration

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