Time dependent selective recurrent discharge of motor units in F-response

Single-fiber F waves compared with conventional surface F waves, and their utility in detecting early diabetic neuropathy

INTRODUCTION

The single-fiber F-wave (SFF-wave) technique assesses the entire length of single motor fibers using a concentric needle. Herein we investigated the utility of this approach in the detection of early diabetes-related neuropathy, and compared it with the use of conventional surface F waves (CF waves).

METHODS

Sixteen patients with diabetes and either no neuropathy or mild neuropathy were assessed and compared with 16 age- and height-matched control participants.

RESULTS

Both CF and SFF waves were abnormal in all 5 patients who had mild neuropathy. However, SFF waves demonstrated subclinical abnormalities in 7 of 11 patients (64%) with no neuropathy, whereas only 2 of these patients (18%) had prolonged CF waves. Minimum F-wave latency was comparable between techniques, but maximum SFF-wave latency was more frequently prolonged, as these delayed motor units were better isolated, rather than buried among summated CF-wave responses.

DISCUSSION

SFF waves highlight the segmental involvement in diabetic neuropathy, and use of the SFF-wave technique detects more abnormalities than with CF waves. Muscle Nerve 58: 665-670, 2018.

About the Neurobiological Foundations of the De-Qi — Stimulus-Response Relation

In acupunctural reflexotherapy, it is usually stated that no appreciable therapeutic effect is obtained under a certain stimulation level, which is determined by the appearance of a particular sensation known as De-Qi. Given that afference control actions of the central nervous system do not work in this way, but rather adapt, with some peculiarities, to a classical schedule of proportionality between stimulus and response, our aim is to evaluate the extent to which acupunctural stimuli of increasing intensity can also increasingly modify neurophysiological parameters, by focusing on quantification of metameric levels, by an F-wave study and by means of somatosensorial evoked potential in the telencephalus. Twenty-one healthy volunteers were studied; values corresponding to the parameters indicated in a basal situation were taken and both a non-acupunctural point and the classical 4IG point were punctured simply, until the De-Qi sensation was obtained, following which, electrical stimulation was applied. Clear progressiveness was observed in the modifications of both the F-value and somesthesic potential values with increasing stimuli. It is true that the main inflexion occurs where obtaining De-Qi, but when overstimulation is applied from that time, greater variations take place, which is particularly patent in the case of somesthesic potential latency. Furthermore, the puncture of an extrachannel point shows that the mere puncturing of the skin does not produce any of the aforementioned effects. Despite the classical postulates, it is observed that, the greater the intensity of the acupunctural stimulus, the greater the modifications in the neurophysiological parameters studied. Control of somesthesic afference by acupuncture has already been demonstrated and quantified; now, however, the direct relation between the intensity of this effect and that of the stimulus used to produce it, which is quite far removed from the classical energetic conceptions, is also observed. The effect of acupunctural stimulation is closely related to the intensity of the stimulus applied and the De-Qi sensation is not required to obtain neurofunctional modifications and stimulations that go beyond it producing greater effects.