How to diagnose lumbar radiculopathy?

Diagnosing Lumbar Radiculopathy

The diagnosis of lumbar radiculopathy requires a combination of clinical history, physical examination, and appropriate imaging studies, with MRI being the preferred imaging modality for patients with persistent symptoms who are candidates for surgery or intervention.

Clinical Assessment

History and Physical Examination

• Lumbar radiculopathy should be suspected when patients present with pain radiating down the leg in a dermatomal distribution, often described as sharp, shooting, or lancinating 1
• The clinical evaluation should focus on identifying one of three categories: nonspecific low back pain, back pain potentially associated with radiculopathy or spinal stenosis, or back pain potentially associated with another specific spinal cause 2
• Key symptoms to assess include:
  • Location and distribution of pain (dermatomal pattern)
  • Presence of sensory changes (numbness, tingling)
  • Motor weakness in specific muscle groups
  • Changes in deep tendon reflexes 3

Red Flag Assessment

• Clinicians must evaluate for "red flags" that suggest serious underlying conditions requiring prompt evaluation:
  • Progressive neurologic deficits
  • Cauda equina syndrome (urinary retention has 90% sensitivity)
  • History of cancer (increases post-test probability from 0.7% to 9%)
  • Unexplained weight loss
  • Fever or signs of infection 2

Diagnostic Testing

Initial Approach

• For most patients with suspected lumbar radiculopathy without red flags, imaging is not recommended in the first 4 weeks as the natural history is improvement with noninvasive management 2
• There is no compelling evidence that routine early imaging affects treatment decisions or improves outcomes 2

When to Order Imaging

• Imaging is indicated for:
  • Patients with severe or progressive neurologic deficits
  • Suspected serious underlying conditions (cancer, infection, cauda equina syndrome)
  • Persistent symptoms despite 6 weeks of conservative management in patients who are candidates for surgery or intervention 2

Preferred Imaging Modalities

• MRI lumbar spine without contrast is the first-line imaging modality for evaluating persistent radiculopathy as it:
  • Provides excellent soft-tissue contrast
  • Accurately depicts disc disease and nerve root compression
  • Can assess vertebral marrow and spinal canal patency 2
• CT myelography is an alternative for patients who:
  • Have contraindications to MRI
  • Have implanted devices that are not MRI-compatible
  • Have significant artifact from metallic surgical hardware 2

Electrodiagnostic Studies

• Electromyography (EMG) and nerve conduction studies can be useful to:
  • Confirm the presence of radiculopathy
  • Determine the specific nerve root(s) involved
  • Differentiate radiculopathy from peripheral neuropathy or other conditions 3

Differential Diagnosis

• The clinical diagnosis of radiculopathy must be distinguished from:
  • Plexopathy (affects multiple peripheral nerve distributions)
  • Peripheral neuropathy
  • Referred pain from facet joints or sacroiliac joints
  • Non-spinal causes of leg pain 2

Diagnostic Pitfalls to Avoid

• Relying solely on imaging findings without clinical correlation - MRI findings often occur in asymptomatic individuals and should always be interpreted in combination with clinical findings 2
• Failure to recognize that pain radiating in a dermatomal distribution with sensory/motor loss in a spinal nerve root pattern indicates radiculopathy, while pain in multiple peripheral nerve distributions suggests plexopathy 2
• Overlooking serious underlying conditions that require urgent evaluation (cauda equina syndrome, infection, malignancy) 2
• Ordering unnecessary imaging for acute radiculopathy without red flags, as most cases improve with conservative management within 4 weeks 2

Diagnostic Algorithm

1. Perform focused history and physical examination to categorize as nonspecific low back pain, radiculopathy/stenosis, or specific spinal pathology 2
2. Assess for red flags requiring immediate imaging (progressive neurologic deficits, suspected cancer, infection, or cauda equina syndrome) 2
3. For patients without red flags, initiate conservative management for 4-6 weeks 2
4. For patients with persistent symptoms after 6 weeks of conservative management who are candidates for surgery or intervention, order MRI lumbar spine without contrast 2
5. Consider CT myelography for patients with contraindications to MRI 2
6. Use electrodiagnostic studies (EMG/NCS) when clinical diagnosis is uncertain or to confirm radiculopathy 3