Cervical Spondylotic Myelopathy¶
Definition¶
Cervical spondylotic myelopathy (CSM) is spinal cord dysfunction caused by degenerative narrowing of the cervical spinal canal. It typically presents with progressive gait difficulty, hand clumsiness, and upper motor neuron signs.
Pathophysiology¶
Cord compression occurs through a combination of:
- Static compression: disc-osteophyte complexes, ligamentum flavum hypertrophy, OPLL
- Dynamic compression: cord impingement during neck extension (ligamentum flavum buckling) and flexion (cord drapes over anterior osteophytes)
- Vascular compromise: compression of the anterior spinal artery or its branches, causing ischemia of the anterior cord
Clinical Features¶
- Gait disturbance: wide-based, spastic gait — often the earliest symptom
- Hand dysfunction: loss of fine motor skills (buttoning, writing) — "myelopathy hand"
- Upper motor neuron signs: hyperreflexia, Hoffmann sign, Babinski sign, clonus
- Lhermitte sign: electric shock sensation radiating down the spine with neck flexion
- May coexist with radiculopathy at the levels of compression
Imaging Findings¶
MRI — Essential for Diagnosis¶
| Finding | Sequence | Significance |
|---|---|---|
| Cord compression | Sagittal T2 | Loss of CSF around the cord; cord deformation |
| T2 hyperintensity in cord | Sagittal T2 | Myelopathy — edema, gliosis, or demyelination |
| T1 hypointensity in cord | Sagittal T1 | Myelomalacia — irreversible cord damage; poor prognosis |
| "Snake-eye" appearance | Axial T2 | Bilateral symmetric anterior horn T2 signal; indicates ischemic damage to the anterior gray matter |
| Cord atrophy | Sagittal/Axial | Decreased cord cross-sectional area; chronic severe compression |
Prognostic Imaging Markers¶
- T2 hyperintensity alone: moderate prognosis — may improve with surgery
- T2 hyperintensity + T1 hypointensity: poor prognosis — less likely to improve
- Cord atrophy: worst prognosis — irreversible loss of neural tissue
- Multilevel compression: worse outcomes than single-level
Clinical Pearl
The "snake-eye" sign (bilateral symmetric T2 hyperintensity in the anterior horns on axial MRI) is an important prognostic marker in CSM. It represents ischemic necrosis of the anterior horn gray matter — similar to the "owl eyes" pattern of anterior spinal artery infarction. Patients with the snake-eye sign tend to have worse surgical outcomes and more residual neurologic deficits. Its presence should be specifically reported to help guide surgical expectations.
Key Points¶
- CSM is the most common cause of spinal cord dysfunction in older adults
- Progressive gait difficulty and hand clumsiness are the hallmark symptoms
- MRI cord signal is the critical finding: T2 hyperintensity = myelopathy; T1 hypointensity = myelomalacia
- The snake-eye sign indicates anterior horn ischemia and predicts worse surgical outcomes
- Generally considered a surgical condition — the natural history is progressive decline
- Both static (osteophytes) and dynamic (flexion-extension) compression contribute
References¶
- Nouri A, Tetreault L, Singh A, Karadimas SK, Fehlings MG. Degenerative Cervical Myelopathy: Epidemiology, Genetics, and Pathogenesis. Spine (Phila Pa 1976). 2015;40(12):E675-93. doi:10.1097/BRS.0000000000000913. PubMed
- Fehlings MG, Tetreault LA, Riew KD, Middleton JW, Wang JC. A Clinical Practice Guideline for the Management of Degenerative Cervical Myelopathy: Introduction, Rationale, and Scope. Global Spine J. 2017;7(3 Suppl):21S-27S. PMC5684844
- Fehlings MG, Tetreault LA, Riew KD, et al. A Clinical Practice Guideline for the Management of Patients With Degenerative Cervical Myelopathy: Recommendations for Patients With Mild, Moderate, and Severe Disease and Nonmyelopathic Patients With Evidence of Cord Compression. Global Spine J. 2017;7(3 Suppl):70S-83S. PMC5684840
- Tetreault L, Kopjar B, Nouri A, et al. The modified Japanese Orthopaedic Association scale: establishing criteria for mild, moderate and severe impairment in patients with degenerative cervical myelopathy. Eur Spine J. 2017;26(1):78-84. PubMed
- Scalia G, Costanzo R, Brunasso L, et al. Correlation between "Snake-Eyes" Sign and Role of Surgery with a Focus on Postoperative Outcome: A Systematic Review. Brain Sci. 2023;13(2):301. PMC9954568
- Zhang Z, Wang H. Is the "snake-eye" MRI sign correlated to anterior spinal artery occlusion on CT angiography in cervical spondylotic myelopathy and amyotrophy? Eur Spine J. 2014;23(7):1541-7. PubMed
- Gaillard F, et al. Cervical spondylotic myelopathy. Radiopaedia.org. https://radiopaedia.org/articles/cervical-spondylotic-myelopathy