How is a prolapsed intervertebral disc diagnosed?

Diagnosis of Prolapsed Intervertebral Disc

MRI is the preferred diagnostic imaging modality for prolapsed intervertebral disc, recommended after 6 weeks of conservative management unless red flags are present. 1, 2

Clinical Evaluation

History

• Duration and pattern of back pain
• Presence of radicular symptoms (pain radiating to limbs)
• Neurological symptoms (numbness, tingling, weakness)
• Bowel/bladder dysfunction (suggests cauda equina syndrome)
• Red flags:
  • Cauda equina syndrome
  • Progressive neurological deficits
  • Suspected malignancy
  • Suspected infection
  • History of trauma/fracture

Physical Examination

• Neurological assessment (motor strength, sensory testing, reflexes)
• Straight leg raise test (positive in lumbar disc herniation with nerve root compression)
• Assessment for muscle weakness or atrophy
• Evaluation of gait and balance

Diagnostic Algorithm

Step 1: Initial Presentation Without Red Flags

• Conservative management for 6 weeks without imaging 1, 2
• Physical therapy, pain management, activity modification

Step 2: Persistent Symptoms or Red Flags Present

• Proceed to imaging studies

Step 3: Imaging Selection

1. MRI without contrast: First-line imaging modality 1, 2

   • Highly sensitive for soft tissue pathology
   • Can accurately assess vertebral marrow and spinal canal patency
   • Can identify disc herniation, nerve root compression, and annular fissures

2. MRI with and without contrast: Consider when suspecting:

   • Malignancy
   • Infection
   • Inflammation 1

3. CT scan without contrast: Alternative when MRI is contraindicated

   • Equal to MRI for predicting significant spinal stenosis
   • Can exclude cauda equina impingement 1

4. CT myelography: Consider when:

   • MRI is contraindicated
   • Patients have implanted medical devices not MRI-compatible
   • Significant artifact from metallic surgical hardware on MRI 1
   • Sometimes more accurate in diagnosing nerve root compression in lateral recess 1

Important Considerations

Cauda Equina Syndrome

• Requires urgent MRI assessment for all patients presenting with new-onset urinary symptoms in the context of low back pain or sciatica 1
• A single 3-D heavily T2-weighted fat-saturated sequence protocol has been shown to be a rapid, highly sensitive tool for evaluating CES in emergency settings 1

Post-Surgical Evaluation

• MRI with and without contrast is preferred to distinguish recurrent/residual disc herniations from scar tissue 1
• CT without contrast is helpful for assessing osseous fusion and hardware integrity 1

Correlation of Imaging with Clinical Findings

• Disc abnormalities are common in asymptomatic individuals 1, 2
• Disc protrusion prevalence increases with age (29% at age 20 to 43% at age 80) in asymptomatic populations 1
• Majority of disc herniations show some degree of reabsorption by 8 weeks after symptom onset 1

Pitfalls to Avoid

1. Early imaging without clinical indication: Leads to increased healthcare utilization and potentially unnecessary interventions 1

2. Relying solely on imaging findings: Morphological abnormalities don't always correlate with clinical complaints 1

3. Incomplete imaging in atypical presentations: For patients with atypical lower limb pain or sphincter disturbances, ensure thorough imaging of the conus region and lower thoracic cord 3

4. Missing upper lumbar disc herniations: Extend imaging to high lumbar metameres when symptomatology is equivocal, as these can present with atypical clinical features 4

5. Failure to recognize red flags: Cauda equina syndrome requires urgent MRI and potential surgical intervention 1, 5

By following this diagnostic approach, clinicians can accurately diagnose prolapsed intervertebral discs while avoiding unnecessary imaging and interventions in cases that can be managed conservatively.