Cervical Myelopathy

Cervical Myelopathy: A Comprehensive Clinical Guide

Cervical myelopathy (CM) represents one of the most significant clinical challenges in orthopedic spine surgery and neurology. It is defined as the functional impairment of the spinal cord resulting from compression within the cervical spine. Unlike cervical radiculopathy, which involves the compression of nerve roots, myelopathy involves the compression of the spinal cord itself, leading to potentially irreversible neurological deficits if left untreated.

1. Introduction and Clinical Definition

Cervical myelopathy is the most common cause of spinal cord dysfunction in patients over the age of 55. It is a progressive, degenerative condition characterized by the narrowing of the spinal canal (stenosis), which places mechanical pressure on the cervical spinal cord.

The clinical hallmark of this condition is a constellation of symptoms including gait instability, loss of fine motor skills, and sensory disturbances in the extremities. Because the spinal cord is a central nervous system structure with limited regenerative capacity, early diagnosis is paramount to preventing permanent disability.

2. Etiology and Pathophysiology

The pathophysiology of cervical myelopathy is multifactorial, generally categorized into static and dynamic mechanical factors.

Primary Etiological Drivers

• Spondylosis: The most common cause, involving age-related disc desiccation, osteophyte formation, and hypertrophy of the ligamentum flavum.
• Ossification of the Posterior Longitudinal Ligament (OPLL): More prevalent in Asian populations; involves the pathological bone formation behind the vertebral bodies.
• Congenital Stenosis: A narrow developmental spinal canal (Torg ratio < 0.8) predisposes individuals to myelopathy even with minor degenerative changes.
• Rheumatoid Arthritis: Causes atlantoaxial subluxation and pannus formation, leading to cord compression.

The Mechanism of Injury

The damage to the spinal cord occurs through two primary mechanisms:
1. Direct Mechanical Compression: Chronic pressure leads to ischemia of the cord and direct axonal compression.
2. Dynamic Microtrauma: Repetitive motion of the neck (flexion/extension) causes the cord to be "stretched" over osteophytes or compressed by the buckling of the ligamentum flavum (the "pincer effect").

3. Clinical Staging and Grading

The Modified Japanese Orthopaedic Association (mJOA) scale is the global standard for assessing the severity of cervical myelopathy.

The Nurick Classification

Often used to describe the functional status regarding gait:
* Grade 0: Signs of cord involvement, no gait abnormality.
* Grade 1: Signs of cord involvement, gait abnormality, but no difficulty with employment.
* Grade 2: Gait abnormality, difficulty with employment.
* Grade 3: Gait abnormality, ambulatory only with assistance.
* Grade 4: Unable to walk, wheelchair-bound or bedridden.

4. Standard Clinical Presentation

Patients typically present with an insidious onset of symptoms. The clinical picture is often described as a "myelopathic hand" and "gait ataxia."

Key Clinical Signs

• Upper Extremity: Loss of fine motor skills (difficulty buttoning shirts, handwriting changes), wasting of the intrinsic hand muscles (interossei atrophy), and clumsiness.
• Lower Extremity: Gait instability, described as "walking on cotton" or a "drunken gait."
• Reflexes: Hyperreflexia in the lower extremities, presence of Hoffman’s sign, and inverted radial reflex.
• Sensory: Non-dermatomal numbness, often described as a "glove-like" distribution.

5. Diagnostic Methodology

A systematic diagnostic approach is required to differentiate CM from other neurological conditions (e.g., ALS, Multiple Sclerosis).

Key Diagnostic Tests

1. Magnetic Resonance Imaging (MRI): The gold standard. T2-weighted images show high-signal intensity (myelomalacia) within the cord, indicating edema or gliosis.
2. Computed Tomography (CT) Myelography: Used for patients who cannot undergo MRI (e.g., those with pacemakers) or to better visualize bony anatomy/OPLL.
3. Electromyography (EMG) / Nerve Conduction Studies: Crucial for ruling out peripheral neuropathies or motor neuron disease.
4. Flexion/Extension X-rays: Used to evaluate for instability or subluxation.

Differential Diagnosis

• Amyotrophic Lateral Sclerosis (ALS): Characterized by fasciculations and progressive muscle wasting without sensory loss.
• Multiple Sclerosis (MS): Typically younger demographic, history of relapsing-remitting symptoms.
• Lumbar Stenosis: Can present with similar gait issues; requires careful spinal cord vs. cauda equina differentiation.

6. Treatment Paradigms and Prognosis

Non-Operative Management

Conservative care (physical therapy, NSAIDs, cervical collar) is generally reserved for patients with very mild symptoms (mJOA 16-17) who are unwilling to undergo surgery. However, studies show that most patients with symptomatic myelopathy will experience progressive decline without intervention.

Surgical Intervention

Surgery is the definitive treatment. The goal is decompression of the spinal canal.
* Anterior Approach (ACDF / Corpectomy): Ideal for 1-3 level compression or kyphotic deformities.
* Posterior Approach (Laminectomy with Fusion / Laminoplasty): Ideal for multi-level stenosis (3+ levels) or congenital narrowing.

Long-Term Prognosis

The prognosis is highly dependent on the duration of symptoms prior to surgery. The "window of opportunity" is critical; patients who undergo surgery within 6-12 months of symptom onset typically exhibit superior outcomes compared to those who wait until severe deficits are established.

7. Risks, Side Effects, and Contraindications

Surgery for cervical myelopathy is high-stakes. Risks include:
* C5 Palsy: A postoperative complication involving deltoid/biceps weakness, occurring in 5-10% of posterior decompression cases.
* Dural Tear: Risk of CSF leak during decompression.
* Hardware Failure: Pseudarthrosis or subsidence of cages in anterior approaches.
* Dysphagia: Common transient side effect following anterior cervical surgery.

8. Frequently Asked Questions (FAQ)

1. Is surgery always required for Cervical Myelopathy?
While mild cases can be monitored, myelopathy is generally a progressive condition. Because the spinal cord has limited ability to recover once damaged, surgery is the gold standard for most symptomatic patients.

2. What is the difference between Radiculopathy and Myelopathy?
Radiculopathy is a pinched nerve root (causing arm pain and numbness). Myelopathy is a pinched spinal cord (causing balance issues, hand clumsiness, and widespread neurological deficits).

3. Does physical therapy cure Cervical Myelopathy?
Physical therapy can help maintain range of motion and strength, but it cannot remove the physical compression on the spinal cord. It is rarely a curative treatment.

4. What is the "Hoffman’s Sign"?
It is a clinical test where the examiner flicks the middle finger. If the thumb and index finger flex involuntarily, it is a positive sign of upper motor neuron damage (myelopathy).

5. Can Cervical Myelopathy be reversed?
Surgery can stop the progression of the disease and often leads to significant improvement. However, "reversal" is not guaranteed; long-standing damage may result in permanent deficits.

6. What is Myelomalacia?
It refers to permanent changes within the spinal cord (softening) seen on an MRI as a bright white signal. It signifies that the cord has suffered structural damage.

7. How long is the recovery after surgery?
Most patients see improvement in symptoms over 6 to 12 months. Early rehabilitation is key to optimizing functional outcomes.

8. Is Cervical Myelopathy hereditary?
While some anatomical predispositions (like a narrow spinal canal) can be inherited, the degenerative changes are typically age-related.

9. What is an "Inverted Radial Reflex"?
It is a reflex abnormality where tapping the radial tendon causes finger flexion rather than the normal forearm contraction, indicating cervical cord involvement.

10. Why is balance affected in Cervical Myelopathy?
The spinal cord acts as the "highway" for electrical signals. When the neck is compressed, the signals meant for the legs are disrupted, leading to ataxia and poor balance.

9. Conclusion

Cervical Myelopathy is a serious, progressive diagnosis that necessitates expert clinical management. By recognizing the early signs—such as the loss of dexterity and gait instability—clinicians can advocate for timely intervention. The transition from diagnosis to surgical decompression is a critical juncture that defines the long-term quality of life for the patient. As practitioners, our goal remains the early identification of myelopathic signs to prevent the transition from a manageable clinical condition to a state of permanent neurological impairment.