Introduction

Ultrasound examination of the axillary nerve is particularly important in PMR in patients with shoulder pain, deltoid weakness, sensory symptoms over the lateral shoulder, or suspected nerve injury after trauma, dislocation, or surgery. It allows direct visualization of the nerve in relation to the posterior circumflex humeral artery, the quadrilateral space, the humeral neck, and the deltoid muscle.

Ultrasound can help detect changes in nerve caliber, loss of fascicular pattern, focal swelling, entrapment, or posttraumatic lesions, and may help differentiate axillary neuropathy from cervical radiculopathy, brachial plexus involvement, or rotator cuff-related shoulder dysfunction. A major advantage is the possibility of side-to-side comparison and targeted assessment of the nerve along its course through anatomically vulnerable regions, especially around the quadrilateral space and posterior shoulder.