Degenerative Cervical Myelopathy: Development and Natural History [AO Spine RECODE-DCM Research Priority Number 2]

Abstract

Study design: Narrative review.

Objectives: To discuss the current understanding of the natural history of degenerative cervical myelopathy (DCM).

Methods: Literature review summarizing current evidence pertaining to the natural history and risk factors of DCM.

Results: DCM is a common condition in which progressive arthritic disease of the cervical spine leads to spinal cord compression resulting in a constellation of neurological symptoms, in particular upper extremity dysfunction and gait impairment. Anatomical factors including cord-canal mismatch, congenitally fused vertebrae and genetic factors may increase individuals' risk for DCM development. Non-myelopathic spinal cord compression (NMSCC) is a common phenomenon with a prevalence of 24.2% in the healthy population, and 35.3% among individuals >60 years of age. Clinical radiculopathy and/or electrophysiological signs of cervical cord dysfunction appear to be risk factors for myelopathy development. Radiological progression of incidental Ossification of the Posterior Longitudinal Ligament (OPLL) is estimated at 18.3% over 81-months and development of myelopathy ranges between 0-61.5% (follow-up ranging from 40 to 124 months between studies) among studies. In patients with symptomatic DCM undergoing non-operative treatment, 20-62% will experience neurological deterioration within 3-6 years.

Conclusion: Current estimates surrounding the natural history of DCM, particularly those individuals with mild or minimal impairment, lack precision. Clear predictors of clinical deterioration for those treated with non-operative care are yet to be identified. Future studies are needed on this topic to help improve treatment counseling and clinical prognostication.

Keywords: cervical spondylotic myelopathy (CSM); cord compression; ossification of the posterior longitudinal ligament (OPLL); progression; risk factors.

Figure 1.

Spectrum of changes in DCM represented by T2 anatomical MRIs. A, A single-level disc degeneration resulting in spinal cord compression (D). Also shown here are hyperintensity changes of the vertebral body endplates consistent with type I or II modic changes (M). B, A patient with ossification of the posterior longitudinal ligament (OP) and disc degeneration (D). C, A patient with severe multi-level bone and disc degeneration and kyphotic deformity. D, A patient with congenital fusion between C4-5 (C). In addition, there is a retrolisthesis evident at the inferior end of the fused vertebrae (S) as well as enlargement of the ligamentum flavum (LF). Taken from Nouri et al.

Figure 2.

Cord-Canal mismatch measurement in 2 different patients based on sagittal T2 MRI. A, Represents a patient without a cord-canal mismatch with a SCOR calculated at 52.2% ([6.12 + 5.79]/[11.3 + 11.5]) × 100. B, The patient has a cord-canal mismatch as evidenced by an SCOR of 73.0% ([5.61 + 5.08]/[7.53 + 7.12]) × 100. Taken from Nouri et al.

Figure 3.

Klippel-Feil syndrome and degenerative cervical myelopathy. A and D, A single fusion of C4-5 seen on T1 MRI and lateral radiograph of the same patient. B and E, Two non-contiguous fusions between C2-3 and C6-7 on T2 MRI and lateral radiograph. C and F, Two contiguous fusions between C4-5 and C5-6 on CT and lateral radiograph. Adapted from Nouri et al.

Figure 4.

Dynamic cervical spinal cord compression on MRI. A neutral (A) and flexion (B) and extension (C) T2 MRI showing the effect of movement on spinal cord compression. Here flexion of the spine unmasks spinal cord compression not clear in neutral imaging. Taken from—Lao et al.

Figure 5.

Prevalence of asymptomatic spinal cord compression among different demographic groups. Taken from Smith et al.