Median Neuropathy
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Injury sites
- When the distal humerus suffers supracondylar fracture (fracture just proximal to the epicondyles), both the median and ulnar nerves can be injured (more rarely the superficial sensory branch of the radial nerve can be, as well).
- The median nerve can be ensnared in the humeral and ulnar heads of the pronator teres muscle as the median nerve exits the cubital fossa.
- When the anterior interosseous nerve is injured in isolation (anterior interosseous syndrome or neuropathy), patients exhibit the "OK" sign; wherein, they are unable to form a circle with the thumb and index finger.
- Neither the thumb's interphalangeal joint nor the index finger's distal interphalangeal joints will flex.
- The most common compression site for the median nerve is the carpal tunnel at the wrist: the nerve passes beneath the flexor retinaculum through the carpal tunnel and is compressed.
Carpal Tunnel Syndrome
- The median palmar cutaneous nerve, which enters the hand superficial to the carpal tunnel, so it's spared.
- Laceration of the palm can injure the recurrent branch of the thumb in isolation.
Weakness
- Median nerve injury produces lateral flexor weakness and thenar eminence (thumb pad) wasting, so-called "ape hand".