Motor unit number index (MUNIX) in myopathic disorders: Clinical correlations and potential pitfalls

Sousa, Manoel Wilkley Gomes de; Escorcio‐Bezerra, Marcio Luiz; Pinto, Wladimir B.V.R.; Souza, Paulo Victor Sgobbi de; Braga, Nadia Iandoli de Oliveira; Oliveira, Acary Souza Bullé; Manzano, Gilberto Mastrocola

doi:10.1016/j.neucli.2019.07.002

Cited by 7 publications

(8 citation statements)

References 17 publications

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“…However, more significant results might be achieved with twenty or more SIP signals of 500‐ms duration . Furthermore, according to reports by Li et al and Gomes de Sousa et al, MUNIX drop can be due to motor unit loss and/or muscle fiber atrophy, and the latter may have impacted the results of this study. However, in contrast to the findings in the myopathic disorders, both increased MUSIX and reduced MUNIX were observed in almost all tested muscles, providing evidence that the decrease in MUNIX is mainly due to motor unit loss.…”

Section: Discussionmentioning

confidence: 71%

Motor unit number index in quantitatively assessing motor root lesions and monitoring treatment outcomes in patients with lumbosacral radiculopathy

et al. 2020

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Introduction:We investigated the feasibility of motor unit number index (MUNIX) in quantitatively assessing motor root lesions and tracking different treatment outcomes in lumbosacral radiculopathy (LR).Methods: Bilateral MUNIX was recorded from the abductor hallucis, extensor digitorum brevis, and tibialis anterior in 44 normal controls and 108 patients with LR, and this was repeated approximately 12 months after treatment in 60 patients with LR.

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Section: Discussionmentioning

confidence: 71%

Motor unit number index in quantitatively assessing motor root lesions and monitoring treatment outcomes in patients with lumbosacral radiculopathy

et al. 2020

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“…In this study, we applied the MUNIX for the assessment of a facial muscle; as demonstrated in previous studies exploring the MUNIX of limb muscles, this technique was well tolerated. 14,16 of normal individuals 21 (47.9 ± 19.1 compared to 42.40 ± 8.31 for MUNIX, and 2.4 ± 0.9 compared to 2.93 mV ± 0.53 for CMAP, respectively), supporting its reproducibility. Our results also provide neurophysiological evidence of facial muscle involvement in SMA patients.…”

Section: Discussionmentioning

confidence: 70%

“…Furthermore, it has a good inter‐rater reliability 11–13 and it can be applied to any muscle in which a CMAP can be obtained, 14 even in pediatric patients 15 . The evaluation of compensatory nerve sprouting has become possible by the detection of enlarged motor units that can be estimated by the motor unit size index (MUSIX) that is calculated by dividing the CMAP amplitude by the MUNIX value 16 . A reduction of the MUNIX in combination with an enlarged MUSIX can provide evidence of loss of spinal motor neurons or motor units.…”

Section: Introductionmentioning

confidence: 99%

“…15 The evaluation of compensatory nerve sprouting has become possible by the detection of enlarged motor units that can be estimated by the motor unit size index (MUSIX) that is calculated by dividing the CMAP amplitude by the MUNIX value. 16 A reduction of the MUNIX in combination with an enlarged MUSIX can provide evidence of loss of spinal motor neurons or motor units. Conversely, a reduction of MUNIX without significant MUSIX changes may imply either a decrease in the muscle fiber size, or a loss of the motor unit without compensatory muscle fiber reinnervation.…”

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confidence: 99%

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Facial nerve vulnerability in spinal muscular atrophy and motor unit number index of the orbicularis oculi muscle

et al. 2023

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Introduction/Aims Measures for assessing cranial nerve vulnerability in spinal muscular atrophy (SMA) have not yet been determined. Motor unit number index (MUNIX) studies have shown correlations with disease severity but have been used only in limb muscles. In the present study, we explore facial nerve response, MUNIX, and motor unit size index (MUSIX) of the orbicularis oculi muscle in a cohort of patients with SMA. Methods Facial nerve response (measured as compound muscle action potential, CMAP), MUNIX, and MUSIX of the orbicularis oculi muscle were cross‐sectionally recorded in patients with SMA and compared to healthy control subjects (HCs). Active maximum mouth opening (aMMO) was also measured at baseline in our SMA cohort. Results Thirty‐seven patients with SMA (21 SMA II; 16 SMA III) and 27 HCs were recruited. CMAP of the facial nerve and MUNIX of orbicularis oculi proved to be feasible and well tolerated techniques. CMAP amplitude and MUNIX scores were significantly lower in patients with SMA compared to HCs (p < .0001). Both MUNIX and CMAP amplitude were significantly higher in patients with SMA III compared to SMA II. No significant difference emerged comparing CMAP amplitude, MUNIX and MUSIX scores between those with different functional status or nusinersen treatment. Discussion Our results provide neurophysiological evidence of facial nerve and muscle involvement in patients with SMA. CMAP of the facial nerve and MUNIX of orbicularis oculi showed high accuracy in discriminating between the various subtypes of SMA and in quantifying the motor unit loss of the facial nerve.

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“…In their work, MUSIX did not change significantly and could be used to help determine whether the MUNIX decrease is indeed accompanied by motor neuron loss. Thus, although it is a marker of disease progression with proven value in primarily denervating disorders, it is recommendable to consider the underlying clinical context beforehand, as it could potentially influence the analysis/interpretation of MUNIX results ( 40 ). There are also studies on stroke patients, which indicates that it remains a dilemma to apply the MUNIX technique in stroke patients.…”

Section: Discussionmentioning

confidence: 99%

Application Value of the Motor Unit Number Index in Patients With Kennedy Disease

Zhang

Yang

et al. 2021

Front. Neurol.

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The aim of this study was to evaluate the usefulness of the motor unit number index (MUNIX) technique in Kennedy disease (KD) and test the correlation between the MUNIX and other clinical parameters. The MUNIX values of the bilateral deltoid, abductor digiti minimi (ADM), quadriceps femoris (QF), and tibialis anterior (TA) were determined and compared with the course of the disease. The MUNIX sum score was calculated by adding the MUNIX values of these 8 muscles. Disability was evaluated using the spinal and bulbar muscular atrophy functional rating scale (SBMAFRS). The MUNIX scores of patients with KD were negatively correlated with the course of the disease (p < 0.05), whereas their motor unit size index (MUSIX) scores were positively correlated with the course the of disease (p < 0.05). MUNIX sum scores were correlated with SBMAFRS scores (r = 0.714, p < 0.05). MUNIX was more sensitive than compound muscle action potentials or muscle strength as an indicator of neuron loss and axonal collateral reinnervation. The MUNIX sum score is an objective and a reliable indicator of disease progression, and it is a potential choice for therapeutic clinical trials. The MUNIX can assess the functional loss of motor axons and is correlated with disability. The MUNIX sum score may be especially suitable as an objective parameter.

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Motor unit number index (MUNIX) in myopathic disorders: Clinical correlations and potential pitfalls

Cited by 7 publications

References 17 publications

Motor unit number index in quantitatively assessing motor root lesions and monitoring treatment outcomes in patients with lumbosacral radiculopathy

Motor unit number index in quantitatively assessing motor root lesions and monitoring treatment outcomes in patients with lumbosacral radiculopathy

Facial nerve vulnerability in spinal muscular atrophy and motor unit number index of the orbicularis oculi muscle

Application Value of the Motor Unit Number Index in Patients With Kennedy Disease

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