Dr. Ebraheim’s educational animated video Part 2 educational video describing the condition known as radial nerve palsy.
Radial nerve palsy results from acute trauma or compression of the radial nerve. The radial nerve originates from the posterior cord of the brachial plexus.
Injury to the radial nerve affects the functions of the wrist and fingers differently depending on the area of injury.
The radial nerve supplies the extensor muscles allowing for extension of the wrist and fingers. Injury to the nerve will cause wrist drop.
High radial nerve injuries usually occurs due to fractures of the distal third of the humeral shaft. The fracture may cause injury to the radial nerve causing paralysis of the wrist and finger extensors. The patient will be unable to perform the “hitch hike “ sign.
Low radial nerve injury usually occurs around the elbow, affecting finger and thumb extension.
A high lesion above the brachioradialis nerve causes wrist drop and loss of finger extension.
In patients with radial nerve palsy, recovery of wrist and finger extension is estimated to be about 1 mm per day. The brachioradialis muscle is the first to recover.
Treatment
•Explore in open humeral fractures
•Observation in closed fracture
•Order EMG and nerve studies 3 weeks after the injury
•The brachioradialis muscle is the first muscle to recover
•Repeat EMG if necessary.
•Radial nerve recovery occurs in about 85% of the cases in about 4-5 months.
•Explore the nerve if there is no recovery
•Tendon transfer may be needed if there are no signs of radial nerve recovery.
•Pronator teres to extensor carpi radialis brevis is a basic transfer
•Splint the wrist in cock up position and order physiotherapy.
The nascent (just born ) polyphasic motor unit activity is the early evidence of nerve regeneration.
Bad prognosis: small polyphasic motor unit 6 months after injury.
Good prognosis: no P wave, no fibrillation in 3 weeks after injury.
Example of a patient recovering completely from radial nerve injury. With improvement od the injury, the patient will also be able to perform the “hitch hike” sign.
Example of a patient partially recovering from radial nerve injury. Recovery of the wrist extensors, but finger extensors are not yet recovered.
Patient example- the radial nerve is not yet recovered but appears recovers. The patient appears to have finger extension. This is an inaccurate examination.
With the wrist placed in extension, the patient cannot extend the fingers = the radial nerve did not recover.
