THE INFLUENCE OF THE REFERENCE ELECTRODE ON CMAP CONFIGURATION - LEG NERVE OBSERVATIONS AND AN ALTERNATIVE REFERENCE SITE

Peroneal and tibial compound motor action potentials (CMAP) recorded u sing the standard belly-tendon montage have different configurations. The peroneal CMAP is a smooth dome shape, while the tibial CMAP has a slow-rising initial component followed by a higher amplitude negative peak. To evaluate possible causes of these differences we investigated the individual activity recordable at the belly and tendon electrodes by using a referential montage with the opposite foot as the referenc e. This type recording shows that the peroneal belly site produces mos t of the nerve CMAP, whereas the tendon site generates most of the hig h tibial CMAP. Some features and technical problems of referential CMA P recording using an opposite limb reference are shown. An alternative method using an ipsilateral distal leg reference site is described, A montage which separately records the activity at the belly or tendon electrodes may provide new insight into mechanisms of commonly observe d nerve conduction phenomena. (C) 1996 John Wiley & Sons, Inc.