RESUMO
INTRODUCTION: The innervation of the hand frequently differs from the usual description that we can find in text books. The most frequent anomalies consist on communications among the median and cubital nerves at level of either forearm (Martin-Gruber anastomosis) or to more distal level (Richie-Cannieu anastomosis), although they are not the only possibilities. OBJECTIVE: To study from a electrophysiological point of view or the variants of the normality in the innervation of the hand and to define their functional characteristics. PATIENTS AND METHODS: We performed an electromyographic and electroneurographic studies on patients that suffered wounded (fundamentally) or other pathologies in the forearm. RESULTS: The presence of double innervation in abductor pollicis brevis and opponens pollicis muscles has been verified in 2.48% of the patients. Although, it has not been possible to determine the prevalence of other anomalies, the presence of several types of anastomosis has been observed: Martin-Gruber types I and III, as well as the incomplete innervation on the part of the cubital nerve of the muscles of the tenar muscles (only of the opponens pollicis). The correct methodology is fundamental in the electrophysiological study, so several pitfalls can take place. It would be desirable to employ techniques that minimize the problems of dispersion of the current, by means of needles. CONCLUSION: It is very important to keep in mind these variations of the normality in the innervation of the hand, specially when pronostic and surgical treatment are considered.
