A study of the effects of anomalous innervation on the diagnosis of median or ulnar nerve injury

Abstract

Objective To study the effects on the diagnosis of median or ulnar nerve injury by the presence of anomalous anastomosis between median and ulnar nerves in the forearm and the palm of the hand, including the anastomosis from median nerve in the forearm to the ulnar nerve (Martin-Gruber anastomosis, MGA), the anastomosis from ulnar nerve in the forearm to the median nerve(reversed Martin-Gruber anastomosis, RMGA), and the anastomosis from median nerve in the palm of the hand to the ulnar nerve (Riche-Cannieu anastomosis, RCA). Methods An 160 cases of median or ulnar nerve injury with the presence of anomalous anastomosis were assigned to three groups: 65 cases of ulnar nerve lesion with MGA, 8 cases of median nerve lesion with RMGA, and 87 cases of median nerve lesion with RCA. The anatomical bases, clinical manifestations, electrophysiological data and diagnosis were discussed. Results In the case of median or ulnar nerve lesion, the function of the muscle which was controlled by the injured nerve can be compensated due to the existence of the anomalous anastomosis. This could result in discrepancy between the clinical symptoms and the degree of nerve lesion and electrophysiological findings. Conclusion Thorough understanding of the characteristics of these three types of anomalous innervation between median and ulnar nerves is crucial to the clinical diagnosis and treatment of median or ulnar nerve injuries, as well as to the correct interpretation of the electrophysiological data. Key words: Electromyography; Median nerve; Ulnar nerve; Anomalous innervation