Shape Variability of Potentials Recorded by a Single-Fiber Electrode and its Effect on Jitter Estimation

Abstract

Technical problems accompanying the recording of fiber pair potentials introduce certain instability in the peak-to-peak interval (rise-time, RT) of these potentials. This study aims (1) to measure the variability observed in RT of a large number of sets of consecutive potentials recorded by a single-fiber (SF) electrode and (2) to evaluate the effect of such variability on the jitter estimation. Using a SF electrode, 140 sets of consecutive potentials were recorded from the m. tibialis anterior of four healthy subjects. For each set, the rise-time variability (RTV) was calculated as the standard deviation of the RTs of the discharges within that set. The effect of RTV in the estimation of jitter from simulated fiber pairs with controlled values of neuromuscular jitter was analyzed. The RTVs of sets visually assessed as produced by a "single-fiber" were always less than 20 μs, whereas those of "composite" sets were normally higher than 20 μs. We found that the RTV always increased the estimated jitter of fiber pairs. Such increment depended on the amount of neuromuscular jitter. The RTV provides an estimate of the possible error introduced in jitter assessment. This could be important for the diagnosis of mild clinical manifestations of myasthenia gravis, myopathies, and Duchenne dystrophies.

Low conversion rate of ocular to generalized myasthenia gravis in Singapore

“…We also found that higher antibody titers were associated with higher generalization rates, also in agreement with previous studies . The relatively low incidence of positive RNS findings in our series is in agreement with previous work, and is consistent with the low rate of generalization in this subgroup. Presence of thymoma has been previously associated with more severe forms of myasthenia, especially in the setting of positive ryanodine receptor antibodies .…”

Prediction of generalization of ocular myasthenia gravis under immunosuppressive therapy in Northwest China

“…There are some limitations in this retrospective study. Restricted clinical condition and examination methods, unwillingness of partial patients and missing data from medical records resulted in small sample size of clinical variables, especially RNS tests in our cohort, but the percentage of patients who entered the final statistical analysis and of those with positive RNS tests were comparable to other studies [7,24,29]. This supported that the conclusions from statistical analysis in this study were reliable.…”

Influence on jitter measurement of components from distant fibres in potential recorded by single‐fibre electrode

“…Variability of the shape of potentials measured using SFE was also studied by Rodriquez et al who found that the rise time variability was a sensitive indicator of whether the shape of the second peak was stable or not. Our results corroborate their findings that in some cases, the presence of components from distant fibres may lead to either notch in the negative peak or an inflection in the rising part.…”