An Approach to Spinal Cord Lesions

Introduction

• Spinal Cord Functionality: Acts as a major highway connecting the brain to the body.
  • Ascending tracts: Towards the brain.
  • Descending tracts: Away from the brain.
• Analogy: Impulses are like cars on a highway, with spinal nerves as slip roads.
• Obstructions: A spinal cord lesion acts like a traffic jam, preventing signals from moving past the obstruction.

Spinal Cord Anatomy

• Spinal Cord Termination: Ends at L1, then forms the cauda equina (a bunch of peripheral nerves).
• Ascending Tracts:
  • Dorsal Columns: Carry fine touch, vibration, and proprioception. Remain ipsilateral until the medulla.
  • Spinothalamic Tracts: Carry pain and temperature information. Decussate immediately, travel contralaterally.
• Descending Tracts:
  • Corticospinal Tract: Carries motor information, also travels contralaterally.
• Blood Supply: Anterior spinal artery supplies the anterior half, two posterior spinal arteries supply the posterior half.

Is the Lesion in the Spinal Cord?

• Mixed Motor Neuron Signs:
  • Upper motor neuron signs: Increased tone, clonus, hyperreflexia, extensor plantars.
  • Lower motor neuron signs: Muscle wasting, fasciculations, flaccid paralysis, reduced reflexes.
• Sensory Level: Abnormal sensation below a specific line (e.g., T10 lesion near umbilicus).
• Sphincter Involvement:
  • Spinal cord lesions: Urinary retention, increased sphincter tone.
  • Cauda equina lesions: Urinary/fecal incontinence.
• Autonomic Dysfunction: Severe dysfunction like autonomic dysreflexia suggests lesion above T6.
• Clinical Sign Patterns: Bilateral signs are common; asymmetry may occur due to different tract routes.
• Back Pain Red Flags:
  • Focal neurological deficit, trauma history, osteoporosis, pain at night, history of malignancy, fever, thoracic pain.

Where is the Problem in the Spinal Cord?

• Location Indicators:
  • Cervical lesions affect all limbs.
  • Thoracic lesions affect only lower limbs.
  • Respiratory difficulties suggest lesion above C3.

What is Causing the Problem?

• Surgical Sieve: Categorizes causes by type:
  • Vascular (e.g., spinal artery occlusion, aortic dissection)
  • Infection (e.g., abscess, viral infections like polio)
  • Trauma
  • Autoimmune (e.g., multiple sclerosis)
  • Metabolic/Nutritional (e.g., B12 deficiency)
  • Neoplastic (e.g., spinal cord compression)
  • Degenerative (e.g., disc disease)
  • Genetic (e.g., hereditary spastic paraplegia)
• Symptom Onset: Helps differentiate potential causes.

Pattern of Damage

• Complete Transection: Complete bilateral loss of motor/sensory function below lesion.
• Brown-Sequard Syndrome:
  • Ipsilateral paralysis, loss of fine touch/proprioception.
  • Contralateral loss of pain/temperature sensation.
• Anterior Cord Syndrome: Bilateral loss of pain/temperature, spastic paralysis. Preserved fine touch/proprioception.
• Posterior Cord Syndrome: Affects dorsal columns, often seen in B12 deficiency.
• Syringomyelia: Fluid-filled cyst around spinal canal, affects upper limbs first.
• Spinal Cord Concussion: Transient loss of function, resolves in 48 hours.
• Spinal Stenosis: Narrowing compresses spinal cord, affecting lower body functions.

Investigations

• Laboratory Tests: Full blood count, B12 levels, antibody screens, etc.
• Imaging: MRI is essential for visualizing lesions. Full spine imaging recommended.
• Lumbar Puncture: For infective/autoimmune causes.

Key Points

• The pattern of symptoms can infer the presence and location of a spinal cord lesion.
• Symptoms limited to lower limbs often indicate a spinal cord lesion.
• Mixed upper/lower motor neuron signs should prompt spinal cord investigation.
• Urinary retention suggests spinal cord problems; incontinence suggests cauda equina lesion.
• MRI is the primary imaging modality for spinal cord assessment.

References

1. NICE CKS on back pain.
2. Mariano et al., Practical approach to spinal cord lesions.
3. Chapman DJ, Teesneuro on spinal cord conditions.
4. Shenoy VS et al., StatPearls on Syringomyelia.
5. Tidy C. on spinal stenosis and compression.