Peripheral Neuropathy, Radiculopathy, and Neuromuscular Junction Disease
Sorting the Peripheral Nervous System
Anatomic targets
Weakness and sensory loss can arise from peripheral nerve, nerve root, plexus, neuromuscular junction, or muscle. The pattern of deficits usually reveals the level.
Peripheral localization clues
Peripheral neuropathy
- Distal symmetric sensory loss
- May have burning pain and reduced reflexes
Radiculopathy
- Pain radiating in a dermatomal pattern
- Weakness and sensory changes follow a root distribution
Fluctuating ptosis and diplopia that worsen with use but spare sensation most strongly suggests:
Fatigable ocular weakness with preserved sensation is classic for neuromuscular junction disease.
Correct answer: Myasthenia gravis
What sensory pattern is typical of many peripheral neuropathies?
Length-dependent nerves are affected first, producing distal sensory symptoms.
Correct answer: distal symmetric stocking-glove loss
Radiculopathy and Plexopathy
Root vs nerve clues
| Feature | Root/plexus | Peripheral nerve |
|---|---|---|
| Pain | Often prominent and radiating | May be present or absent |
| Sensory pattern | Dermatomal or regional | Named nerve distribution |
| Reflexes | May be reduced in a root-specific pattern | Reduced in the affected nerve distribution |
| Motor findings | Myotomal weakness | Weakness in muscles supplied by one nerve |
Radiating back pain with weakness in a myotomal pattern suggests:
This is typical of a nerve root lesion.
Correct answer: Radiculopathy
Why is sensation often spared in pure neuromuscular junction disease?
The pathology is at the synapse between motor nerve and muscle, not in sensory pathways.
Correct answer: because the sensory neurons are not affected
Common Neuromuscular Junction Disorders
Myasthenia gravis vs Lambert-Eaton syndrome
Myasthenia gravis
- Postsynaptic acetylcholine receptor or related antibodies
- Ocular and bulbar weakness, fatigability
Lambert-Eaton syndrome
- Presynaptic calcium channel autoimmunity
- Proximal weakness that may improve with repeated use
Autoimmune postsynaptic acetylcholine receptor disease is called:
Myasthenia gravis is the classic postsynaptic neuromuscular junction disorder.
Correct answer: Myasthenia gravis
What is one hallmark of Lambert-Eaton syndrome?
Facilitation with repeated contraction is a helpful clinical clue.
Correct answer: improvement with repeated use