- See:
- Carpal Tunnel
- Cervical Disc Disease
- Cubital Tunnel Syndrome
- Nerve Entrapment:
- w/ entrapment, nerve fibers are not affected uniformly;
- superficially located fibers tend to bear the brunt of compression, while central fibers are relatively spared;
- large diameter, heavily myelinated fibers are more sensitive to compression than poorly myelinated fibers;
- thus fibers subserving light touch and motor fibers are more likely to be involved in compression neuropathy than unmyelinated pain fibers;
- Types of Compression:
- mild and brief compression produces a transient conduction block in nerve, which normalizes soon after the pressure is relieved;
- there are no major structural changes in the nerve, but axoplasmic flow is interrupted because extrinsic pressure;
- w/ acute severe compression one observes a characteristic sequential invagination of telescoping of the myelin sheath;
- chronic compression:
- segmental demyelination occurs (axonotmesis)
- this accounts for the slowing of the nerve observed clinically;
- w/ sustained compression, axolysis occurs in compressed segment, and wallerian degernation occurs distally;
- critical threshol pressure for initiating changes in nerve is 30 mm Hg
- neuroma in continuity: (spindle neuroma - eg Morton's neuroma)
- in most cases nerve has an intact perineural sheath
- may result from chronic nerve compression and irritation which causes nerve swelling;
- the proliferation of fibrous tissue causes nerve compression;
- Electromyography
- Motor Conduction Latency:
- Sensory latency
Current Concepts: Entrapment Neuropathies of the Upper Extremities.