抄録
Nerve conduction velocity (NCV) measurements have been widely used to assess the electrophysiological properties of peripheral nerves and to detect neuropathies at a subclinical stage. But conventional NCVs are usually expressed as the NCV for the fastest conducting fiber and the current standard methods do not supply information on the slower conducting fibers, nor detect information in individual fiber groups.
A new analytical method is presented for estimating the distribution of conduction velocity (DCV), based upon the spectrum analysis of the waveforms of two compound action potentials (CAPs) recorded by surface electrodes from a nerve bundle.
If the spectrums of the two CAPs recorded at two different sites in response to supramaximal electrical stimulation at the distances l1 and l2 are given as Gl1(ω) and Gl2(ω) respectively, the spectrum representation of the latency distribution Pl2(ω) for the propagation distance l2 is expressed as follows:
Pl2(l1ω/l2)={Gl1(ω)/Gl2(ω)}Pl2(ω), where ω is an angular frequency.
For this formula, the algorithm which computes Pl2(ω) successively without using the iterative calculation methods is given.
Our estimation method is based upon the principle that the CAPs are recorded monopolarly to estimate the DCV, but in practical use, it is almost impossible to obtain appropriate CAP waveforms by the monopolar recording method, because of stimulation and muscle artefacts.
In order to evaluate the efficacy of bipolarly recorded two CAP waveforms for this computation algorithm, the CAP waveforms reconstructed by simulation techniques have been applied. As a result, it was found that the difference between the recording methods was reflected on the waveform of single fiber action potential but not on the latency distribution. The distance between bipolarly recorded electrodes did not affect the reproducibility of the latency distribution estimations.
It seems that this new method is non-invasive and could be used for evaluation of peripheral neuropathies.
