Evaluation of the complexity of motor unit potentials in anal sphincter electromyography.
OBJECTIVE
Motor unit potential (MUP) morphology can be quantified using parameters describing electrophysiological size and shape (complexity). Traditionally, MUP complexity has been estimated using parameters number of phases and turns. Recently, 'irregularity coefficient' (IR), measuring the length of the MUP curve normalized with its amplitude, has been introduced. The aim of this study was to evaluate IR in the external anal sphincter muscle.


METHODS
Sensitivity was examined in 61 patients with chronic cauda equina lesions, and specificity in 75 controls using a standard concentric EMG needle and EMG system with multi-MUP analysis.


RESULTS
When evaluated separately the sensitivity of IR was 16% lower, and specificity 5% higher compared to number of turns, with both differences decreasing to only 2 and 1%, respectively, when each of these parameters was added to MUP area and duration.


CONCLUSIONS
Our present results suggest that IR provides a similar diagnostic usefulness, but a more appropriate description of MUP complexity compared to traditional MUP parameters.


CONCLUSIONS
IR seems to be suitable to complement one of MUP parameters measuring electrophysiological MUP size in the future quantitative EMG.
Podnar
Simon
S
Institute of Clinical Neurophysiology, Division of Neurology, University Medical Center Ljubljana, SI-1525 Ljubljana, Slovenia. simon.podar@kclj.si
Zalewska
Ewa
E
Hausmanowa-Petrusewicz
Irena
I
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001003:Anal Canal / Q000502:physiology*; D004576:Electromyography / Q000379:methods* / Q000592:standards*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012680:Sensitivity and Specificity