Causes of radial nerve palsy

At the level of the axilla: uncommon to occur as isolated radial nerve palsy, usually associated with other upper limb mononeuropathies or brachial plexopathy. There is weakness of the triceps (elbow extension) with this form of radial nerve palsy, as well as the typical wrist and finger drop.

Causes:

– improper use of crutches

– prolonged period of unconsciousness with arm extended + pressure applied to the axilla

At the level of the humerus: most common type, as the nerve can be easily compressed between the humeral shaft and a firm surface – also called Saturday night palsy or bridegroom’s palsy

Other causes:

– tourniquets

– trauma – direct injury (e.g. knife wound) or fracture of the humeral shaft

– direct infiltration by a malignant process

– ischaemia vasa nervorum

– as part of mononeuropathy multiplex due to

vasculitis

diabetes

paraneoplastic syndrome

HIV

sarcoid

lead toxicity

It can be complete – loss of wrist and finger extension and sensory loss on the dorsal surface of the base of the thumb, or incomplete with loss of wrist and finger extension only.

Treatment:

– surgical if secondary to trauma

– ~ 75% recover spontaneously – while waiting for recovery, the wrist should be splinted in 60 degrees dorsiflexion to prevent contractures / atrophy