Cervical Myelopathy: The Silent Progression

Degenerative Cervical Myelopathy (DCM) is the most common cause of spinal cord dysfunction in adults worldwide. Yet, it is frequently missed in primary care because it is often painless. Patients present with "clumsiness" or "old age balance," only to be diagnosed when they have already suffered irreversible cord damage.

For the orthopaedic surgeon, detecting DCM early is a critical skill. This article outlines the pathophysiology, subtle clinical signs, and the surgical decision-making algorithms that define modern management.

Pathophysiology

The spinal cord in the cervical spine is a tight fit. The normal canal diameter is 17-18mm. Myelopathy typically occurs when this narrows to <13mm (Congenital or Acquired).

Two Mechanisms of Injury

1. Static Compression: Direct pressure from osteophytes, disc herniations, or OPLL (Ossification of the Posterior Longitudinal Ligament) causes ischemia to the cord.
2. Dynamic Compression: In extension, the ligamentum flavum buckles inward (shingling). In flexion, the cord is draped over anterior osteophytes. This repetitive micro-trauma leads to demyelination.

Visual Element: Cross-section diagram showing the cord flattened into a "banana shape" by anterior osteophytes and posterior ligamentum flavum buckling.

Clinical Presentation: The "Myelopathy Hand"

Pain is unreliable. Look for function.

Subjective

• Hands: "I can't button my shirt." "I drop my coffee cup." "My handwriting has changed."
• Legs: "I feel like I'm walking on cotton wool." "I'm unsteady in the dark." (Loss of proprioception).
• Bladder: Urgency/Frequency (Late sign).

Objective (Upper Motor Neuron Signs)

• Finger Escape Sign: Ask patient to hold fingers extended and adducted. The little finger spontaneously abducts due to weakness of the intrinsic muscles (ulnar nerve mimic, but without sensory loss).
• Grip and Release: Patient should be able to make a fist and fully extend fingers 20 times in 10 seconds. Myelopathic patients are slow and incomplete.
• Hoffmann's Sign: Flick the distal phalanx of the middle finger. Positive if the thumb/index finger flexes.
• Inverted Radial Reflex: Tapping the brachioradialis causes finger flexion instead of wrist extension.
• Hyperreflexia & Clonus: Lower limbs.
• Tandem Gait: Inability to walk heel-to-toe.

Classification Systems

We don't just say "Myelopathy." We grade it.

1. Nurick Grade

Focuses on gait.

• Grade 0: Signs, no symptoms.
• Grade 1: Symptoms, but walks normally.
• Grade 2: Mild disability, working.
• Grade 3: Disability prevents work, walks without aid.
• Grade 4: Needs walking aid.
• Grade 5: Chair bound / Bedridden.

2. Modified Japanese Orthopaedic Association (mJOA) Score

A 17-point scale assessing Upper Limb Motor, Lower Limb Motor, Sensory, and Sphincter function.

• Mild: 15-17
• Moderate: 12-14
• Severe: <12

Imaging Findings

MRI is the gold standard.

• T2 Signal Change: High signal within the cord indicates myelomalacia (edema/gliosis).
  • Faint/Fuzzy: Edema (Reversible).
  • Bright/Sharp ("Snake Eyes"): Cystic necrosis (Irreversible).
• T1 Signal Change: Low signal (Black) correlates with poor prognosis.

Management: To Cut or Not to Cut?

Natural History: DCM typically follows a stepwise deterioration. It rarely improves spontaneously.

• Guidelines:
  • Moderate/Severe (mJOA < 14): Surgery is recommended.
  • Mild (mJOA > 15): Controversial. Surgery is an option, or close surveillance. If progression occurs -> Surgery.

Surgical Approaches

The goal is to increase the space for the cord (Decompression).

1. Anterior (ACDF / Corpectomy)

• Indication: 1-3 level disease. Kyphotic alignment (need to restore lordosis). Anterior compression (large discs).
• Technique: Remove disc/body, place cage/plate.
• Pros: Direct decompression. Restores alignment. High fusion rate.
• Cons: Dysphagia (swallowing difficulty). Adjacent Segment Disease (2-3% per year).

2. Posterior (Laminoplasty)

• Indication: Multi-level disease (>3 levels). Congenital stenosis. OPLL. Preserved Lordosis.
• Technique: "Open Door" or "French Door". Hinge the lamina open to expand the canal without fusing.
• Pros: Preserves motion. Avoids fusion complications.
• Cons: Neck pain. C5 Palsy risk. Requires lordotic spine (if kyphotic, the cord won't drift back away from osteophytes).

3. Posterior (Laminectomy + Fusion)

• Indication: Multi-level disease WITH Kyphosis or Instability.
• Technique: Remove lamina completely, place lateral mass screws to fuse.
• Pros: definitive decompression and stabilization.
• Cons: Loss of motion. Higher infection/blood loss risk.

Clinical Trap: Do not perform a Laminoplasty in a Kyphotic spine. The cord acts like a bowstring; opening the back won't help if the cord is tethered over the anterior bone.

Complications: The C5 Palsy

A unique complication of cervical decompression (Anterior or Posterior).

• Presentation: Deltoid/Biceps weakness (cannot lift arm) occurring 2-5 days post-op.
• Cause: Tethering effect? Reperfusion injury?
• Prognosis: Most resolve spontaneously, but it can take 6-12 months.

Conclusion

Cervical myelopathy is a diagnosis that must not be missed. The window of opportunity to preserve function is narrow. If you see a patient with "clumsy hands" and hyperreflexia, think Cord, not Carpal Tunnel.

References

1. Fehlings, M. G., et al. (2017). "A Clinical Practice Guideline for the Management of Patients With Degenerative Cervical Myelopathy." Global Spine Journal.
2. Nurick, S. (1972). "The natural history and the results of surgical treatment of the spinal cord disorder associated with cervical spondylosis." Brain.
3. Kato, S., et al. (2016). "Comparison of Anterior and Posterior Approaches for the Treatment of Multilevel Cervical Spondylotic Myelopathy." Global Spine Journal.