Primary Axillary Nerve Injury: A Review of Diagnosis and Management

Primary axillary nerve injury is a clinically significant yet underrecognized cause of shoulder dysfunction, often leading to substantial morbidity when diagnosis or treatment is delayed. Despite extensive literature on brachial plexus pathology, guidance specific to axillary nerve injury remains limited. Owing to its anatomic course adjacent to the glenohumeral joint, proximal humerus, and quadrilateral space, the axillary nerve is particularly susceptible to traction, compression, and direct trauma. Classic presentation includes deltoid weakness and sensory deficits over the lateral shoulder; however, diagnosis is frequently obscured by concomitant conditions such as rotator cuff tears, fractures, or instability. This review synthesizes current understanding of axillary nerve anatomy, injury mechanisms, diagnostic strategies, and management principles. Common etiologies include glenohumeral dislocation—the most frequent cause—as well as proximal humerus fractures, upper brachial plexus traction injuries, ballistic trauma, and quadrilateral space syndrome. Each entity demonstrates distinct pathophysiology and clinical features, ranging from transient neurapraxia to complete nerve disruption. Accurate diagnosis relies on a combination of clinical evaluation, imaging, and electrodiagnostic studies. Magnetic resonance imaging and MR neurography are increasingly utilized but may yield false positives, while electromyography and nerve conduction studies remain essential for lesion characterization and prognostication. Electrodiagnostic testing is particularly valuable in differentiating neurapraxia from axonotmesis and neurotmesis and guiding operative decision-making. Most axillary nerve injuries demonstrate a high rate of spontaneous recovery with nonoperative management because most cases maintiain nerve continuity. However, absence of clinical or electrodiagnostic improvement by 3–4 months warrants surgical consideration. Operative strategies include neurolysis, nerve grafting, and nerve transfer, with timing tailored to injury severity and mechanism. Early intervention is critical in cases of confirmed transection or high-grade injury to optimize reinnervation before irreversible motor end plate degeneration. Quadrilateral space syndrome represents a distinct compressive neuropathy with both neurogenic and vascular subtypes, typically managed conservatively but occasionally requiring surgical decompression. Early recognition, appropriate diagnostic workup, and individualized management are essential to optimize functional outcomes in patients with primary axillary nerve injury.