Assessment of clinical and electrophysiological findings in axillary nerve injury

Abstract

Aims: This study investigated the association between clinical features and neurophysiological findings in patients with axillary nerve injury (ANI). Methods: Patients with isolated ANI were included in the study. Muscle strength was evaluated using the Medical Research Council (MRC) scale. Axillary nerve compound muscle action potential (CMAP) amplitude and latency, as well as the presence of positive sharp waves (PSWs), fibrillation potentials, and motor unit action potentials (MUAPs) in the deltoid muscle, were assessed. Results: Eleven patients with ANI were included in the study (7 men and 4 women). The causes of ANI were humeral fracture in two patients and shoulder dislocation in four patients. The remaining five patients had blunt trauma without any associated fracture or dislocation. A positive correlation was observed between axillary nerve CMAP amplitude and the deltoid muscle MRC score (p=0.016, r=0.700). A negative correlation was found between axillary nerve CMAP latency and the deltoid muscle MRC score (p=0.048, r=-0.670). All patients demonstrated PSWs, fibrillation potentials, or MUAP abnormalities in the deltoid muscle. Conclusion: This study demonstrated an association between axillary nerve CMAP latency and amplitude and the deltoid muscle MRC score in patients with ANI. These results suggest that axillary nerve CMAP latency and amplitude are valuable neurophysiological measures for the diagnosis and follow-up of ANI. It should also be noted that ANI may occur even in the absence of a fracture or dislocation.