The axillary nerve has sensory and motor innervation. The
sensory portion innervates the upper lateral cutaneous nerve
of the arm. Patients with sensory deficits from involvement
of the axillary nerve therefore have neuropraxia involving
the lateral aspect of the upper arm. The axillary nerve
supplies motor function to the teres minor (an external
rotator) and to the deltoid muscle. Patients who have motor
involvement from axillary nerve lesions have weakness to
shoulder abduction and external rotation. In chronic or
neglected axillary nerve injury, significant deltoid atrophy
may be present.