Conventional Nerve Conduction Velocity Research Articles

Low sensitivity of F-wave in the electrodiagnosis of carpal tunnel syndrome

ObjectivePrevious studies showed “F-wave inversion” (F-INV) as a sensitive method in the electrodiagnosis of early stage of carpal tunnel syndrome (CTS). This study aimed at evaluating the sensitivity and specificity of F-wave and nerve conduction velocity (NCV) testing in CTS. MethodsWe consecutively enrolled 244 cases and 108 controls. F-waves analysis included: Fwave minimum and mean latencies, F-wave persistence and chronodispersion, mean-F/CMAP amplitude ratio, F-INV. Specificity and sensitivity of F-waves parameters were calculated in the whole sample of CTS patients and by grouping the patients according to CTS severity. Multivariate logistic regression was also performed using F-INV as a dependent variable. ResultsIn the whole sample the sensitivity of F-mean-INV and of median–ulnar NCV comparative testing was 50.8% and 93.7%, respectively. F-INV sensitivity dropped to 8% in CTS early stage. F-INV could be predicted only by distal motor latency of the median nerve. The sensitivity of all F-wave parameters increased only in the most severe stages of CTS. ConclusionsThis study does not confirm the electrodiagnostic usefulness of F-INV in early stage of CTS. All F-wave parameters, including F-INV, are much less sensitive than conventional NCV in CTS electrodiagnosis. F-wave does not add further useful information specifically related to CTS.

The value of contact heat evoked potentials for the early diagnosis of diabetic peripheral polyneuropathy

Objective To study the value of contact heat evoked potentials (CHEPs) for the early diagnosis of diabetic peripheral polyneuropathy. Methods Seventy-five diabetic patients were examined by conventional nerve conduction velocity studies and then divided into 2 groups: diabetics with normal nerve conduction and diabetics with abnormal nerve conduction. Thirty-three normal subjects were used as controls. Toronto Clinical Neuropathy Sco-ring System was used to evaluate the patients. CHEPs were recorded using different stimulation intensities at different temperatures. Results The peak latencies of 45℃ , 50℃, 53℃ in diabetics with normal nerve conduction group were longer than those in normal control group, with a significant difference between the 2 groups(P<0.05). The peak latencies of diabetics were positively related to Toronto scores. Conclusion CHEPs could detect the impair-ment of diabetic peripheral nerve and reveal the impairment earlier than conventional nerve conduction velocity exami-nation, The prolongation of peak latency in diabetics group was significantly and positively related to clinical condi-tion. Key words: Contact heat evoked potentials; Diabetes mellitus; Diabetic peripheral polyneuropathy

C-fibre function in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) frequently involves the central nervous system (CNS), but to a considerably lesser degree leads to peripheral neuropathy as measured by conventional nerve conduction velocity studies. Neuropathic symptoms are, however, frequently reported. Abnormalities of other nerve fibers than the large myelinated nerves might thus be responsible for such phenomena. Three age matched groups of 44 patients with SLE, 50 patients with rheumatoid arthritis (RA) and 45 healthy controls were investigated with quantitative sensory thermotesting. Warm detection thresholds (WDT) and heat pain detection thresholds (HPDT) were found significantly higher in SLE compared to RA and controls. There were no differences between the RA and the control group. In the SLE group no association to disease duration, medication or CNS abnormalities were found. Neuropathic symptoms and vibration thresholds showed weak associations to WDT. These findings imply that there is an impairment of C-fibre function in SLE. This small fibre neuropathy is probably not part of a generalized diffuse polyneuropathy also affecting large fibres, although this can not be ruled out completely by this study.

H reflexes as a measure for uremic polyneuropathy. A longitudinal study in patients treated with dialysis or renal transplantation

Assessment of peripheral nerve function in end stage uremia by clinical and conventional nerve conduction velocity studies was compared to that using H reflex measurements. The latter proved to be most sensitive technique. The results of the test correlated well with clinical and with other neuro-physiological measures. Nerve function as evaluated by H reflexes remained stable during the first 2 years of dialysis, but deteriorated later on. H reflex latencies shortened after renal transplantation. The results of H reflex measurements did not correlate with biochemical parameters, which makes the test a less attractive overall measure for the efficiency of therapy in uremia. In the follow-up of patients under treatment for uremic polyneuropathy, however, recording of H reflexes provides an important measure.

H reflexes as a measure for uremic polyneuropathy. A longitudinal study in patients treated with dialysis or renal transplantation

Assessment of peripheral nerve function in end stage uremia by clinical and conventional nerve conduction velocity studies was compared to that using H reflex measurements. The latter proved to be most sensitive technique. The results of the test correlated well with clinical and with other neuro-physiological measures. Nerve function as evaluated by H reflexes remained stable during the first 2 years of dialysis, but deteriorated later on. H reflex latencies shortened after renal transplantation. The results of H reflex measurements did not correlate with biochemical parameters, which makes the test a less attractive overall measure for the efficiency of therapy in uremia. In the follow-up of patients under treatment for uremic polyneuropathy, however, recording of H reflexes provides an important measure.

A new method for estimation of nerve conduction velocity distribution in the frequency domain

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. Conventional NCVs are usually expressed as the NCV for the fastest conducting fibers and the current standard methods do neither supply information about slower conducting fibers, nor detect information about individual fiber groups. We present a new analytical method, to estimate the distribution of conduction velocity (DCV), based upon spectral analysis of the wave forms of two compound action potentials (CAPs) recorded by surface electrodes from a nerve bundle. If the spectra of the two CAPs recorded at two different sites in response to supramaximal electrical stimulation at distances l 1 and l 2 are given as G 11(ω) and G 12(ω), the spectral representation of the latency distribution P 12(ω) for the propagation distance l 2 is expressed as follows: ▪ where ω is an angular frequency. We developed an algorithm that computes P 12(ω) successively without using iterative calculation methods. Our estimation method is theoretically 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 wave forms by monopolar recording methods, because of stimulation and muscle artefacts. In order to evaluate the efficacy of bipolarly recorded CAP wave forms for this computation algorithm, we examined the two CAP wave forms reconstructed by simulation techniques. We found that the difference between the monopolar and bipolar recording methods was reflected in the wave form extracted for the single fiber action potentials but not in the latency distribution. The distance between the bipolarly recorded electrodes (1.5 cm was the minimal distance used) did not affect the reproducibility of estimating the latency distribution. This new method is non-invasive and could be used for evaluation of peripheral neuropathies.

The diagnostic value of the F wave latency (author's transl)

The N. medianus was stimulated electrically in 44 healthy persons and in 30 unselected diabetics. Latencies of the F wave were measured, corrected for different lengths of the upper extremity, and used for computation of nerve conduction velocity. In comparison with conventional motor nerve conduction velocities the F wave latencies showed a more pronounced difference between the normal and the pathological (diabetic) range. The F wave nerve conduction velocities also varied less than conventional nerve conduction velocities. The explanation for this might be that the F wave recordings are the result of a full anti- and orthodromic impulse propagation which travels 5 to 6 times further than the impulse measured with conventional nerve conduction velocity methods. Therefore small delays of nerve conduction will be amplified and can be better recognized by F wave latency measurements. The present findings suggest that F wave latencies may be more sensitive than conventional nerve conduction velocities in evaluating mild cases and in identifying the initial phases of neuropathies.