Related Experiment Videos
Conduction block in carpal tunnel syndrome.
M C Kiernan1, I Mogyoros, D Burke
1Prince of Wales Medical Research Institute and Department of Neurology, Prince of Wales Hospital, Randwick, Sydney, Australia. Matthew.Kiernan@unsw.edu.au
Brain : a Journal of Neurology
|June 4, 1999
Summary
Wrist extension causes nerve conduction block and axonal depolarization in healthy individuals and carpal tunnel syndrome patients. This suggests focal nerve compression may explain some patient symptoms.
Area of Science:
- Neuroscience
- Electrophysiology
Background:
- Nerve conduction block and axonal excitability changes are key in neurological disorders.
- Carpal tunnel syndrome (CTS) symptoms are often intermittent and linked to nerve compression.
Purpose of the Study:
- To determine if wrist extension induces nerve conduction block.
- To compare excitability changes from wrist extension to focal nerve compression.
- To investigate the mechanism of conduction block in CTS.
Main Methods:
- Healthy subjects and CTS patients underwent maintained wrist extension (90 degrees).
- Electrophysiological measurements assessed nerve conduction and axonal excitability.
- Conduction block was induced by ischemic compression in separate experiments.
Main Results:
- Wrist extension caused >50% reduction in cutaneous afferent potential amplitude (conduction block).
- Axonal depolarization, indicated by prolonged latency and altered supernormality/refractoriness, occurred at the wrist.
- Similar conduction block and depolarization were observed in CTS patients.
Conclusions:
- Wrist extension induces a 'depolarization' block, similar to ischemic compression.
- This block is not solely due to axonal depolarization and may not always involve demyelination.
- Ischemic compression may explain intermittent symptoms and electrodiagnostic findings in mild to moderate CTS.