RESUMEN
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. Often these aberrant findings may be the result of an innervation anomaly. In this review article, a description is given of the most common innervation anomalies in upper and lower extremities: communications between the median and ulnar nerves in the forearm, communications between the median and ulnar nerves in the hand, innervation of the median nerve territory in the forearm and hand by branches of the musculocutaneous nerve, the existence of an accessory deep peroneal nerve. Useful electrodiagnostic tests to identify these anomalies are described along with the clinical situations where these anomalies may be a source of misinterpretation. A few clinical cases are reported were these tests were useful to recognize an anomaly. Note: in this study all recordings during nerve conduction studies were done with surface electrodes.