Perform a neurological examination of this patient's arms.
· An intoxicated person sleeping with the head resting in the upper arm, causing compression of the nerve over the middle thirdof the humerus; this is known as Saturday night palsy.· Trauma to the nerve while it courses through the axilla, e.g. crutch palsy, shoulder dislocation, fractures of humerus or radius.· History of exposure to lead (lead neuropathy).
· There is weakness of extension of the wrist and elbow (wrist flexion is normal). · The patient is unable to straighten her fingers.· If the wrist is passively extended, however, the patient is able to straighten her fingers at the interphalangeal joints (due to theaction of interossei and lumbricals) but is unable to extend the metacarpophalangeal joint.· There appears to be a weakness in abduction and adduction of the fingers, but this is not present when the hand is kept flat ona table and the fingers are extended.Proceed as follows:· Test the brachioradialis, looking for weakened elbow flexion. When the patient attempts to flex the elbow against resistance,the brachioradialis no longer springs up.· Test the triceps.· Check sensation over the first dorsal interosseous.
1. The radial nerve gives off two branches at the elbow: -Superficial radial (entirely sensory). -Posterior interosseous (entirelymuscular).
2. If the injury is situated above the junction of the upper and middle thirds of the humerus, the action of triceps is lost.
3. If the lesion is situated in the middle third of the humerus (frequent site of fracture of the humerus), the brachioradialis isspared.
This patient has features of radial nerve palsy with the brachioradialis remaining unaffected (lesion) resulting from a fracture locatedin the middle third of the humerus (aetiology); she is disabled by the deficits (functional status).
What is the cutaneous supply of the radial nerve?Overlap in the areas supplied by the median and ulnar nerves means that only a small area of skin over the first dorsal interosseousis exclusively supplied by the radial nerve.
What do you know about the origin of the radial nerve?
The radial nerve is the termination of the posterior cord of the brachial plexus and is derived from the fifth, sixth, seventh and eighthcervical spinal nerves.
What are the branches of the radial nerve in the forearm?
The radial nerve enters the forearm and passes between the two heads of the supinator muscle to become the posteriorinterosseous nerve.
What muscles are supplied by the radial nerve?
The radial nerve supplies the triceps, anconeus, brachioradialis, extensor carpi radialis longus and, through the posteriorinterosseous nerve, extensor carpi radialis brevis, supinator, extensor digitorum, extensor digiti minimi, extensor ulnaris, the threeextensors of the thumb and extensor indicis.