Predictive power of motor unit potential parameters in anal sphincter electromyography

Abstract

The diagnostic utility of motor unit potential (MUP) parameters is usually based exclusively on their diagnostic sensitivity, disregarding specificity. In the present study, advanced statistical methods were used to determine MUP parameters with the highest predictive power for the separation of neuropathic and normal external anal sphincter (EAS) muscles. Using multi-MUP analysis, 3,720 MUPs from 138 muscles of 52 patients with cauda equina lesion and 2,526 from 112 muscles of 64 controls were obtained. Only two principal components (PCs), which put weight on the MUP area and amplitude, were needed to explain all the data variability. On logistic and probit regression analyses, MUP area, duration, and number of turns gave results identical to all MUP parameters. Our results suggest that only these three MUP parameters are needed, and that they are as effective as PCs, in MUP analysis of chronic neuropathic EAS muscles. Reduced number of MUP parameters is expected to simplify MUP analysis and increase its specificity.

Sensitivity of motor unit potential analysis in facioscapulohumeral muscular dystrophy

“…The sensitivities obtained with three MUP parameters (MUP thickness, duration, and number of phases), which were previously claimed to be most useful in myopathies, 7,10 were higher than those obtained with the three MUP parameters (MUP area, duration, and number of turns) most useful in neuropathic sphincter muscles. 17,18 The present study thus confirmed our previous notion that no uniform pattern of MUP parameters is optimal in all muscles and conditions. 15,17 In the present study, in both the biceps brachii and vastus lateralis muscles, we were able to identify a set of three MUP parameters (thickness and amplitude in both muscles, duration in the biceps brachii, and area or size index in the vastus lateralis) that provided the same sensitivity as all eight MUP parameters.…”

“…17,18 The present study thus confirmed our previous notion that no uniform pattern of MUP parameters is optimal in all muscles and conditions. 15,17 In the present study, in both the biceps brachii and vastus lateralis muscles, we were able to identify a set of three MUP parameters (thickness and amplitude in both muscles, duration in the biceps brachii, and area or size index in the vastus lateralis) that provided the same sensitivity as all eight MUP parameters. This points to an even higher correlation between MUP parameters in myopathy than neuropathy; in neuropathy, six MUP parameters were needed to obtain the same sensitivity as all eight MUP parameters.…”

“…[17][18][19] The low sensitivity of the number of turns is in even sharper contrast to our previous studies of neuropathic conditions in the anal sphincter muscle, 17,18 and was even lower than the number of phases, which had a very low sensitivity in neuropathy. 17,18 This can probably be at least partially explained by the different amplitude thresholds of the two parameters (number of turns, 50 V; number of phases, 20 V). Thus, Stewart et al, who used a 25-V criterion for number of turns, found that its sensitivity was surpassed only by MUP thickness in patients with different myopathies.…”

“…In our previous studies we validated in detail multi-MUP analysis for neuropathic conditions in the external anal sphincter (EAS) muscle. 15,[17][18][19] For other muscles and conditions such validation has not yet been performed.In the present study, we examined the utility of multi-MUP analysis in a specific myopathic disorder.The sensitivity of individual MUP parameters and the cumulative sensitivity of several combinations of MUP parameters were calculated in the biceps brachii and vastus lateralis muscles of patients with a genetic diagnosis of facioscapulohumeral muscular dystrophy (FSHD). …”

Criteria for neuropathic abnormality in quantitative anal sphincter electromyography

“…14,16 It is probably useful to apply both mean values and outlier criteria because they are complementary, with mean values disclosing diffuse, and outliers, focal pathology. 11,18 For the external anal sphincter (EAS) muscle, normative values of MUP parameters useful in quantitative EMG, 16 as well as an optimal set of MUP parameters for detection of muscle abnormality, 11 have been defined. However, the optimal diagnostic criteria for the diagnosis of neuropathic conditions in this muscle remain unknown.…”