Nerve conduction velocity distributions: a method for estimation based upon two compound action potentials.

A model was presented describing the nerve-bundle CAP in terms of its constituent SFAPs. The model has a general structure capable of accommodating a large variety of specific assumptions regarding the nature of the CAP. Using this model, several techniques were presented for estimating the DCV of a nerve bundle. One method, refered to as the 2CAP method, was presented in detail. This method does not require explicit knowledge of the SFAP waveshapes in order to yield an estimate of the DCV, but does require that the CAP be recorded at two sites along the course of the nerve. In order to evaluate the clinical utility of the 2CAP method of DCV analysis, the following factors were studied: reproducibility, sensitivity to temperature and stimulus intensity, and variation within a normal population. The results indicate that the 2CAP method, when controlled for stimulus intensity and temperature, provides a reproducible measure of nerve function with the capacity to distinguish subtle differences in conduction properties of normal human nerves. Further application of this technique to patients with diabetes mellitus indicates that the DCV can demonstrate subtle electrophysiologic abnormality, even in patients with normal conventional nerve conduction studies. Although DCV analysis cannot accurately characterize all types of nerve abnormalities (such as focal nerve lesions), it will likely become a tool for earlier detection and more accurate diagnosis of many nerve diseases, and provide a key to the better understanding of the dynamics of nerve growth, development, damage, healing, and response to treatment.