Neurophysiological and clinical aspects of nerve communications of the upper and lower extremities

Introduction: Anomalous innervations of the extremities are common and influence the interpretation of electrophysiologic studies in normal subjects and those with peripheral nerve lesions. The aim of this study was to describe the most common innervation anomalies in upper and lower extremities and to point out their clinical repercussions. Methods: Article has an analytical character and review of literature, including some personal articles. Results and Discussion: Double innervation and communications among nerves are causes of anomalies of innervation of the skin and muscles. The fact of communications of fibers among nerves is better called “nerve communication” than “nerve anastomosis”. Anomalous innervations of the upper and lower extremities are, therefore, common and influence on the interpretation of neurophysiological parameters during electromyoneurography. Namely, in the course of an electrodiagnostic investigation of a peripheral nerve lesion, the examiner may be confronted with unexpected findings in contradiction with the clinical picture. In this review, a description is given of the most common innervation anomalies in upper and lower extremities: median to ulnar nerve communication (Martin-Gruber anastomosis); ulnar to median nerve communication (Marinacci anastomosis/MA); variations in the innervation of intrinsic muscles of the hand (Riche-Cannieu anastomosis; Berrettini anastomosis); accessory deep peroneal nerve; and tibial to peroneal nerve communication. Conclusion: As anomalous innervations of the extremities are common and influence the interpretation of electrophysiological studies in normal subjests and those with peripheral nerve lesions, detailed anatomical knowledge is essential for accurate interpretation of physical examination, electrophysiological findings, diagnosis, prognosis and reducing the risk of iatrogenic injuries during surgical procedures. If these variations are not given due regard, errors and other consequences will be inevitable.