Can lumbar radiculopathy present with symptoms of polyneuropathy?

Lumbar Radiculopathy and Polyneuropathy: Overlap and Distinctions

Lumbar radiculopathy can present with some symptoms that overlap with polyneuropathy, but they are distinct clinical entities with different pathophysiological mechanisms and diagnostic findings. 1

Clinical Presentation Overlap

• The clinical diagnosis of plexopathy or radiculopathy can be challenging as there is considerable overlap in clinical presentations, making it difficult to determine whether neurologic signs and symptoms localize to a single nerve root (radiculopathy) or to the lumbosacral plexus (plexopathy) 1

• Lumbar radiculopathy may mimic polyneuropathy in some cases, presenting with sensory symptoms that can be confused with those of polyneuropathic conditions 2

• In patients with systemic conditions (like systemic sclerosis), both radiculopathy and polyneuropathy may coexist, further complicating the clinical picture 3

Key Distinguishing Features

• Sensory symptom profiles differ between radiculopathy and classical neuropathic pain syndromes (like painful diabetic polyneuropathy):

  • Touch-evoked allodynia and thermal hyperalgesia are relatively uncommon in radiculopathy compared to other neuropathic pain conditions 2
  • Radiculopathy typically presents with severe painful attacks and pressure-induced pain combined with mild spontaneous pain and mild mechanical allodynia 2

• Motor conduction abnormalities show distinct patterns:

  • In axonal polyneuropathies, compound muscle action potentials (CMAPs) are more likely to be unobtainable or of low amplitude with prolonged distal latency 4
  • In lumbosacral radiculopathies, CMAPs are more likely to be normal in both amplitude and distal latency 4
  • F-response abnormalities differ: polyneuropathies show abnormalities of minimal latency or persistence, while radiculopathies typically show a prolonged maximum-minimum latency range 4

Diagnostic Considerations

• Electrodiagnostic (EDX) examination with needle electromyography (EMG) is the most important test for radiculopathy, with high specificity but modest sensitivity 5

• Combination of nerve conduction studies and EMG is valuable in excluding entrapment neuropathies and polyneuropathy that may mimic radicular symptoms 5

• MRI is often necessary to differentiate between conditions:

  • MRI lumbar spine is typically performed first due to the higher prevalence of radiculopathy-related degenerative spine disease 1
  • MRI lumbosacral plexus may be needed when clinical uncertainty exists between plexopathy and radiculopathy 1
  • In some cases, lumbosacral plexus MRI can detect spinal causes of nerve root compression not visible on lumbar spine MRI, such as lateral disc herniations 1

• Combining multiple diagnostic modalities improves accuracy:

  • A comprehensive approach using clinical evaluation, ultrasound, and neurophysiology helps avoid misdiagnosis 6
  • MRI lumbosacral plexus combined with electromyography shows significant correlation between nerve signal abnormality on MRI and findings of active radiculopathy on EMG 1

Clinical Pitfalls and Caveats

• Tumors of peripheral nerves (such as sural or tibial nerve) may mimic radiculopathy symptoms, highlighting the importance of comprehensive nerve assessment 6

• In patients with systemic conditions, small-fiber polyneuropathy may coexist with radiculopathy but remain undetectable by standard electrodiagnostic testing 3

• Lumbar stenosis or lumbosacral radiculopathy can cause a similar pattern of numbness, pain, and weakness as polyneuropathy, but the clinical presentation differs:

  • Lumbar stenosis typically presents with neurogenic claudication that worsens with walking and standing but improves with sitting or lying down 1
  • This is opposite to polyneuropathy symptoms, which typically worsen when lying in bed and improve with walking 1

• Carpal tunnel syndrome and lumbar stenosis are distinct from polyneuropathy but may cause similar patterns of symptoms, leading to potential diagnostic confusion 1