What is Lumbar Radiculopathy?

What is Lumbar Radiculopathy?

Lumbar radiculopathy is a condition where neurologic symptoms and signs localize to a single spinal nerve root in the lumbar region, caused by irritation or compression of the nerve root, resulting in pain radiating down the leg in a dermatomal distribution with or without accompanying sensory loss or motor dysfunction. 1

Pathophysiology

The underlying mechanism involves more than simple mechanical compression—it represents a combination of:

• Compression that sensitizes the nerve root to mechanical stimulation 2
• Physical stretching of neural structures 2
• Chemically mediated non-cellular inflammatory reaction that causes ectopic nerve impulses perceived as pain in the distribution of the affected nerve root 2
• Irritation of the sensory root or dorsal root ganglion, leading to abnormal nerve signaling 2

Clinical Presentation

Pain Characteristics

• Sharp, shooting, or lancinating quality that radiates as a narrow band down the length of the leg, both superficially and deep 2
• Radiates in a dermatomal distribution below the knee, following the path of the affected nerve root 1, 3
• When the sciatic nerve is involved, the American College of Physicians and American Pain Society explicitly define this as "sciatica," which is "the most common symptom of lumbar radiculopathy" 3

Associated Features

• May coexist with radiculopathy (objective sensory and/or motor dysfunction from conduction block) 2
• Can occur alongside spinal or somatic referred pain 2
• Weakness, sensory loss, and flaccid loss of tendon reflexes in regions innervated by the affected nerve root distribution 1

Anatomical Distribution

The most commonly involved nerve roots are L3, L4, L5, and S1, with each producing distinct symptoms:

• Lumbar plexus involvement (L1-L4) causes weakness, sensory loss, and reflex changes in the anterior and medial thigh 1
• Sacral plexus involvement (L5-S3) produces abnormalities in the gluteal (motor only), peroneal, and tibial nerve territories 1

Distinguishing from Plexopathy

A critical clinical distinction exists between radiculopathy and plexopathy, though considerable overlap in clinical presentations makes diagnosis challenging 1:

• Radiculopathy: Pain radiating in a dermatomal distribution reflecting a single spinal nerve root innervation 1
• Plexopathy: Abnormal symptoms localizing to an anatomically defined network of nerves, manifesting as pain in more than one peripheral nerve distribution 1

Because of this overlap, MRI lumbar spine is often performed prior to MRI lumbosacral plexus due to the considerably higher prevalence of radiculopathy-related degenerative spine disease 1

Diagnostic Confirmation

• Clinical diagnosis is confirmed by electrodiagnostic studies (electromyography and nerve conduction studies) 1, 4
• Careful neurological evaluation examining strength, deep tendon reflexes, sensation, and muscular function is necessary 4
• MRI findings correlate with electrodiagnostic evidence: abnormal intraneural signal on MRI shows statistically significant correlation with findings of active radiculopathy on electromyography 1