Lumbar Radiculopathy Definition
Lumbar radiculopathy is dysfunction of a lumbar nerve root characterized by pain, sensory impairment, weakness, or diminished deep tendon reflexes in a specific nerve root distribution. 1
Core Clinical Features
The diagnosis requires objective neurological findings, not just pain alone. 2 The American College of Physicians defines radiculopathy as nerve root dysfunction that must include demonstrable deficits such as:
- Motor weakness in a myotomal distribution 2
- Sensory deficits in a dermatomal pattern 2
- Diminished or absent deep tendon reflexes corresponding to the affected nerve root 1, 2
- Pain radiating in a nerve root distribution 1
Relationship to Sciatica
Sciatica is the most common symptom of lumbar radiculopathy, but they are not synonymous. 1, 2
- Sciatica describes pain radiating down the leg below the knee in the sciatic nerve distribution, suggesting nerve root compromise from mechanical pressure or inflammation 1
- A patient can have sciatica without radiculopathy if radiating leg pain exists but objective neurological findings (weakness, sensory loss, reflex changes) are absent 2
- Conversely, radiculopathy always involves nerve root dysfunction with demonstrable neurological deficits, not just pain 2
Distinction from Plexopathy
Radiculopathy must be distinguished from plexopathy, which involves abnormal symptoms localizing to a nerve plexus rather than a single nerve root. 1 Pain radiating in a dermatomal distribution with accompanying sensory or motor loss reflecting spinal nerve root innervation indicates radiculopathy, whereas plexopathy causes weakness and sensory loss in multiple peripheral nerve territories 1
Specific Nerve Root Examination Findings
The diagnosis requires comprehensive neurological examination targeting specific nerve roots 2:
- L4 nerve root: Assess knee extension strength and patellar reflex 2
- L5 nerve root: Test great toe and foot dorsiflexion strength 2
- S1 nerve root: Evaluate foot plantarflexion and ankle reflexes 2
- Dermatomal sensory testing in corresponding distributions 2
The combination of radicular pain pattern, dermatomal sensory changes, and motor weakness in a nerve root distribution establishes the diagnosis even without a positive straight leg raise test. 2
Common Pitfall
The straight leg raise test has high sensitivity (91%) but poor specificity (26%) for disc herniation, meaning many positive tests are false positives. 2 Do not rely on this test alone for diagnosis—objective neurological deficits are required 2