1 research outputs found
Automatic jitter measurement in needle-detected motor unit potential trains
In an active motor unit (MU), the time intervals between the firings of its muscle fibers vary across successive MU
activations. This variability is called jitter and is increased in pathological processes that affect the neuromuscular junctions or terminal axonal segments of MUs. Traditionally, jitter has been measured using single fiber
electrodes (SFEs) and a difficult and subjective manual technique. SFEs are expensive and reused, implying a
potential risk of patient infection; so, they are being gradually substituted by safer, disposable, concentric needle
electrodes (CNEs). As CNEs are larger, voltage contributions from individual fibers of a MU are more difficult to
detect, making jitter measurement more difficult. This paper presents an automatic method to estimate jitter
from trains of motor unit potentials (MUPs), for both SFE and CNE records. For a MUP train, segments of MUPs
generated by single muscle fibers (SF MUP segments) are found and jitter is measured between pairs of these
segments. Segments whose estimated jitter values are not reliable, according to several SF MUP segment characteristics, are excluded. The method has been tested in several simulation studies that use mathematical models
of muscle fiber potentials. The results are very satisfactory in terms of jitter estimation error (less than 10% in
most of the cases studied) and mean number of valid jitter estimates obtained per simulated train (greater than
1.0 in many of the cases and less than 0.5 only in the most complicated). A preliminary study with real signals
was also performed, using 19 MUP trains from 3 neuropathic patients. Jitter measurements obtained by the
automatic method were compared with those extracted from a commercial system (Keypoint) and the edition and
supervision of an expert electromyographer. From these measurements 63% were taken from equivalent interval
pair sites within the time span of the MUP trains and, as such, were considered as compatible measurements.
Differences in jitter of these compatible measurements were very low (mean value of 1.3 μs, mean of absolute
differences of 2.97 μs, 25% and 75% percentile intervals of − 0.85 and 3.82 μs, respectively). Although new tests
with larger number of real recordings are still required, the method seems promising for clinical practice.This work has been supported by the Spanish Ministry of Science, Education, and Universities, under the “Salvador de Madariaga” 2018 Program and by the
Spanish Ministry of Education and Research, under the PID2019-109062RB-I00 project. Open Access funding provided by the Public University of Navarra