Entrapment syndromes (Syndromes of compression of peripheral nerves)
Peripheral nerves are vulnerable to chronic compression in many sites, these are listed below with some basic details
- Carpal tunnel syndrome - Median nerve at carpal tunnel
In this question we’ll look at all six of these common peripheral nerve compressions.
Median nerve compression at the wrist in the carpal tunnel
Known as carpal tunnel syndrome, this is compression of the median nerve through the carpal tunnel with the main symptoms being pain, numbness and tingling of the first three and a half digits on the hand (starting from the thumb). Patients will often present with weakened grip, and atrophy of the thenar muscles can occur after a sustained period.
Risk factors include obesity, repetitive wrist work, pregnancy, a family history and rheumatoid arteritis. Repetitive motion of the fingers is an exacerbating element, along with diseases that inflame the contents of the canal such as diabetes, rheumatoid synovitis and pregnancy. Diagnosis can be confirmed by identification of Tinel sign where tapping the carpal tunnel causes paresthesias in the median nerve distribution and Phalen sign where flexing the wrist causes a similar paresthesia.
Treatment is splinting of the wrist in slight dorsiflexion during sleep. Methylprednisolone provides short term relief, but most patients require operative release of the nerve.
Proximal compression of the median nerve
This is rare but includes the following:
- Compression at struthers ligament bridging the medial epicondyle that can compress both the brachial artery and the nerve as they pass beneath
- At the level of pronator teres leading to both motor and sensory symptoms
- In the upper forearm, compression due to anterior interosseous syndrome, causes weakness of the thener but nothing else is affected
Ulnar nerve compression
This is much less common than carpal tunnel syndrome, however potentially more severe if it happens proximately. In such cases there is intrinsic muscle failure and recovery is rare. Proximal compression of the nerve is more common than the distal form (compression in Guyon's canal). At the below the nerve is vulnerable to external pressure as it crosses the medial condyle, fractures of this region also commonly lead to disruption of the nerve.
Clinical onset is generally insidious, with motor and sensory symptoms depending on the site of compression: