The radial nerve may become compressed at the lateral and posterior aspect of the humerus ( level with the lateral intermuscular septum).
A temporary external pressure to the radial nerve results in a so called "saturday's night palsy".
The patient has fallen asleep with the arm over the edge of the chair.
Most often the lesion is a "neuropraxis" – only
the myelin sheath and the Schwann cells are affected, without damage
to the axons.
The recovery of the Schwann cells will not take more than two weeks
where after complete recovery of the neural function is achieved.
More serious lesions of the radial nerve resulting in permanent palsy may occur after a fracture of the humerus or after a surgical procedure.>br>( open reduction and internal fixation of complex fractures).
Irreversible lesions of the nerve usually do not result from direct
squeezing against the bone but from indirect stretching under the hard
and immobile intermuscular septum.