02/04/2023
Pathophysiology of Degenerative Cervical Myelopathy 💡
https://link.springer.com/article/10.1007/s00701-023-05558-x)
👉 Degenerative cervical myelopathy (DCM) is a term used to broadly refer to a disease state characterized by chronic or subacute compression on the cervical spinal cord resulting in gradual and progressive neurologic dysfunction (https://pubmed.ncbi.nlm.nih.gov/25839387/, https://pubmed.ncbi.nlm.nih.gov/5385911/)
🌍 The estimated prevalence of DCM is reported to be about 2.3% worldwide, but this estimate is likely an underestimate of the true disease burden (https://pubmed.ncbi.nlm.nih.gov/32677521/).
🗜 DCM is considered the most common cause of spinal cord dysfunction worldwide and can have profound functional implications (https://pubmed.ncbi.nlm.nih.gov/26020847/). In a study that evaluated short-form 36 health survey results, the quality of life for patients with DCM was estimated to be worse than for patients who suffer from cancer or diabetes (https://pubmed.ncbi.nlm.nih.gov/28065875/).
👴 Since DCM is largely degenerative in nature, the prevalence is predicted to increase with an aging global population (https://pubmed.ncbi.nlm.nih.gov/26020847/, https://pubmed.ncbi.nlm.nih.gov/26378347/)
📍 DCM can present clinically with a combination of motor, sensory and autonomic deficits along with different gradations of somatic pain:
👉 Neck pain/stiffness,
👉 Increased lower and/or upper limb deep tendon reflexes
👉 Unilateral or bilateral limb/body pain
👉 Loss of superficial reflexes below the neck
👉 Upper limb weakness, numbness or loss of dexterity
👉 Positive Hoffman signs (thumb adduction and thumb and finger flexion after forced flexion and sudden release of the tip of the long finger)
👉 Lower limb stiffness, weakness or sensory loss
👉 Babinski and/or Chaddock signs
👉 Urgency of bladder more than bowel; urgency incontinence; frequency of urination
👉 Upper limb weakness beyond the bounds of a single nerve root on one or both sides
👉 Imbalance/unsteadiness
👉 vertigo and blurred vision (https://pubmed.ncbi.nlm.nih.gov/5385911/, https://pubmed.ncbi.nlm.nih.gov/35092814/)
👉 Weakness in the lower limbs in upper motor neuron distribution
👉 Paresthesias (pins and needle sensation)
👉 Sensory loss in lower and/or upper limbs and/or torso
👉 Spasticity in the limbs, especially the lower extremities
👉 Gait disturbance, especially if suggestive of spasticity
👉 Lhermitte’s sign (shock-like sensations extending down the spine and out into the limbs with neck flexion or extension)
☝️ There is evidence that the degree of cervical cord compression does not always correlate with the severity of the clinical presentation. In fact, in a study using high-resolution MRI, cervical cord compression was observed in many asymptomatic individuals, and on the opposite end of spectrum, some symptomatic patients may have very minimal evidence of compression on imaging (https://pubmed.ncbi.nlm.nih.gov/35255357/, https://pubmed.ncbi.nlm.nih.gov/2398088/, https://pubmed.ncbi.nlm.nih.gov/29654015/)
📍 DCM is a broad term that outlines multiple degenerative pathologies in the cervical spine which, among others, includes spondylosis, ossification of the posterior longitudinal ligament (OPLL) and degenerative disc disease (DDD) (figure. https://link.springer.com/article/10.1007/s00701-023-05558-x)
📍 Recently, the pathophysiology of DCM was further characterized to include the impact of multiple vector forces acting on the spinal cord. This paradigm supports that compressive factors are not the sole determinants of injury to the spinal cord, but are also largely influenced by tensile (due to elongation and/or effect of tethering) and shear forces (due to cranio-caudal oscillation of cord).
📍 These biomechanical changes trigger an inflammatory cascade similar to traumatic spinal cord injury, leading to a repeated cycle of endothelial cell dysfunction, breakdown of the blood-spinal cord barrier, accumulation of macrophages and microglia, and eventually neuronal and oligodendroglial cell death. This toxic environment leads to demyelination, astrogliosis and axonal degeneration. (https://pubmed.ncbi.nlm.nih.gov/32425740/, https://pubmed.ncbi.nlm.nih.gov/25839387/)
