Myelopathy

Myelopathy is a clinical syndrome resulting from dysfunction of the spinal cord due to various pathological processes. It can lead to significant neurological deficits affecting motor, sensory, and autonomic functions. Early recognition and intervention are essential to prevent irreversible damage and improve outcomes.

Definition and Classification

Definition

Myelopathy refers to any neurological deficit related to the spinal cord. It encompasses a range of symptoms caused by compression, ischemia, inflammation, demyelination, or degenerative changes affecting the spinal cord tissue.

Types of Myelopathy

Myelopathy can be classified based on location, onset, and underlying cause:

• Cervical myelopathy: Involves the cervical spinal cord, often resulting in upper and lower limb dysfunction
• Thoracic myelopathy: Involves the thoracic spinal cord, potentially causing sensory and motor deficits in the trunk and lower limbs
• Lumbar myelopathy: Rare due to the termination of the spinal cord at the conus medullaris; usually affects nerve roots more than the cord
• Acute myelopathy: Rapid onset, often due to trauma or infarction
• Chronic myelopathy: Gradual progression, commonly from degenerative or compressive etiologies

Anatomy and Pathophysiology

Spinal Cord Anatomy

The spinal cord extends from the medulla oblongata to the conus medullaris and is organized into gray and white matter:

• Gray matter: Contains neuronal cell bodies and interneurons, organized into dorsal (sensory) and ventral (motor) horns
• White matter: Composed of ascending sensory tracts and descending motor tracts
• Vascular supply: Provided by the anterior and posterior spinal arteries, supplemented by segmental medullary arteries

Pathophysiological Mechanisms

Myelopathy results from various mechanisms that disrupt normal spinal cord function:

• Compression: Pressure from bone, disc herniation, tumors, or ligaments impairs neural conduction
• Ischemia: Reduced blood flow can cause infarction or chronic hypoxia of the spinal cord
• Demyelination: Loss of myelin in conditions like multiple sclerosis slows nerve conduction
• Inflammation: Immune-mediated or infectious processes lead to neuronal injury and edema

Etiology

Degenerative Causes

Degenerative changes are the most common cause of chronic myelopathy, particularly in older adults. They result from gradual wear and structural changes in the spine:

• Cervical spondylotic myelopathy: Degeneration of intervertebral discs and facet joints leading to cord compression
• Osteophyte formation: Bone spurs that can impinge on the spinal cord or nerve roots
• Disc herniation: Protrusion of the intervertebral disc into the spinal canal causing compression

Traumatic Causes

Trauma can produce acute myelopathy through direct injury to the spinal cord or its surrounding structures:

• Spinal cord injury: From hyperflexion, hyperextension, or axial loading
• Fractures or dislocations: Vertebral instability can compress or transect the cord

Vascular Causes

Vascular abnormalities can compromise spinal cord perfusion, resulting in myelopathy:

• Spinal cord infarction: Occlusion of spinal arteries leads to sudden neurological deficits
• Arteriovenous malformations: Abnormal vascular connections causing ischemia or hemorrhage

Infectious and Inflammatory Causes

Infections and autoimmune processes can inflame the spinal cord and disrupt function:

• Multiple sclerosis: Demyelinating plaques causing progressive myelopathy
• Transverse myelitis: Acute inflammation across one or more spinal cord segments
• Infections: Viral, bacterial, or fungal pathogens leading to spinal cord inflammation

Neoplastic Causes

Tumors may compress the spinal cord or infiltrate its tissue, producing myelopathic symptoms:

• Primary spinal cord tumors: Gliomas, ependymomas, or astrocytomas originating within the cord
• Metastatic lesions: Secondary tumors from systemic cancers impinging on the cord or epidural space

Clinical Features

Motor Symptoms

Myelopathy commonly presents with motor deficits due to corticospinal tract involvement:

• Weakness, often in the upper or lower limbs depending on cord level
• Spasticity and increased muscle tone
• Gait disturbances including unsteadiness and difficulty with fine motor tasks

Sensory Symptoms

Sensory pathways may be affected, resulting in:

• Numbness or tingling in the limbs
• Paraesthesia or abnormal sensations
• Loss of vibration or position sense, particularly in chronic cases

Autonomic Symptoms

Involvement of autonomic pathways can produce bowel, bladder, or sexual dysfunction:

• Urinary retention or incontinence
• Constipation or fecal incontinence
• Sexual dysfunction, including erectile or ejaculatory difficulties

Diagnosis

Clinical Examination

Diagnosis of myelopathy begins with a detailed neurological assessment:

• Neurological assessment: Evaluation of muscle strength, tone, and coordination
• Reflex testing: Assessment of deep tendon reflexes and presence of hyperreflexia
• Special signs: Babinski sign, Hoffmann sign, and clonus indicate upper motor neuron involvement

Imaging Studies

Imaging is crucial for identifying the underlying cause and extent of spinal cord involvement:

• MRI of the spinal cord: Gold standard for evaluating cord compression, edema, or demyelination
• CT myelography: Useful when MRI is contraindicated or for bony detail
• X-ray: Assessment of degenerative changes, fractures, or alignment abnormalities

Electrophysiological Tests

Electrophysiological studies help assess functional integrity of spinal cord pathways:

• Somatosensory evoked potentials (SSEPs): Measure conduction in sensory tracts
• Motor evoked potentials (MEPs): Evaluate corticospinal tract function and motor pathway integrity

Treatment

Conservative Management

Initial management may be non-surgical in mild or slowly progressive cases:

• Physical therapy: Exercises to maintain mobility and strengthen muscles
• Medications: Nonsteroidal anti-inflammatory drugs (NSAIDs) or short courses of corticosteroids to reduce inflammation

Surgical Management

Surgery is indicated in cases of significant or progressive cord compression:

• Decompression procedures: Laminectomy, laminoplasty, or discectomy to relieve pressure on the spinal cord
• Spinal fusion: Stabilization of the spine after decompression
• Indications: Progressive neurological deficits, severe pain, or radiographic evidence of cord compression

Rehabilitation

Post-treatment rehabilitation is essential to maximize functional recovery:

• Occupational therapy: Assistance with activities of daily living and adaptation strategies
• Assistive devices: Braces, walkers, or wheelchairs to improve mobility and safety

Prognosis and Complications

Factors Influencing Prognosis

The outcome of myelopathy depends on several factors, including:

• Severity and duration of spinal cord compression
• Age and overall health of the patient
• Promptness of diagnosis and treatment
• Underlying etiology, such as degenerative, traumatic, or neoplastic causes

Potential Complications

Untreated or severe myelopathy can lead to multiple complications, including:

• Permanent motor deficits or paralysis
• Chronic sensory disturbances such as numbness or pain
• Autonomic dysfunction including bladder, bowel, or sexual dysfunction
• Spinal deformities due to instability or chronic compression

References

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