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Higashihara M, Yamazaki H, Izumi Y, Kobayashi M, Nodera H, Oishi C, Iwata A, Murayama S, Kaji R, Sonoo M. Far-field potential of the compound muscle action potential as a reliable marker in amyotrophic lateral sclerosis. Muscle Nerve 2023; 68:257-263. [PMID: 37086196 DOI: 10.1002/mus.27829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 03/29/2023] [Accepted: 03/30/2023] [Indexed: 04/23/2023]
Abstract
INTRODUCTION/AIMS Reliable neurophysiological markers in amyotrophic lateral sclerosis (ALS) are of great interest. The compound muscle action potential (CMAP) amplitude has been a conventional marker, although it is greatly influenced by the electrode position. We propose the far-field potential of the CMAP (FFP-CMAP) as a new neurophysiological marker in ALS. METHODS Patients with ALS and age-matched healthy controls were enrolled. We used a proximal reference (pref) in addition to the conventional distal reference (dref). Routine CMAP was recorded from the belly-dref lead and FFP-CMAP from the dref-pref lead for the ulnar and tibial nerves. Multiple point stimulation motor unit number estimation (MUNE) was also examined in the ulnar nerve. Inter-rater reproducibility was evaluated by two examiners, and some patients were followed up every 3 mo for 1 y. RESULTS We tested 17 patients with ALS and 10 controls. The amplitudes of routine CMAP and FFP-CMAP in the ulnar and tibial nerves, and hypothenar MUNE value in the ulnar nerve were significantly decreased in ALS compared to controls. Ulnar FFP-CMAP achieved the highest inter-rater intraclass correlation coefficient (ICC) value (0.942) when compared with routine CMAP (0.880) and MUNE (0.839). The tibial FFP-CMAP had a higher ICC value (0.986) than the routine CMAP (0.697). In this way, the FFP-CMAP showed high inter-rater reproducibility because its shape was not much influenced by the electrode position. During 1-y follow-up, decline of CMAP, FFP, and MUNE showed significant correlations with the Amyotrophic Lateral Sclerosis Functional Rating Scale - Revised (ALSFRS-R). DISCUSSION The FFP-CMAP shows promise as a reliable marker for ALS.
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Affiliation(s)
- Mana Higashihara
- Department of Neurology, Tokyo Metropolitan Geriatric Hospital, Tokyo, Japan
| | - Hiroki Yamazaki
- Department of Neurology, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
| | - Yuishin Izumi
- Department of Neurology, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
| | | | - Hiroyuki Nodera
- Department of Neurology, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
- Department of Neurology, Tenri Hospital, Tenri, Japan
| | - Chizuko Oishi
- Department of Neurology, Kyorin University Hospital, Mitaka, Japan
| | - Atsushi Iwata
- Department of Neurology, Tokyo Metropolitan Geriatric Hospital, Tokyo, Japan
| | - Shigeo Murayama
- Department of Neurology, Tokyo Metropolitan Geriatric Hospital, Tokyo, Japan
| | - Ryuji Kaji
- Department of Neurology, Tokushima University Graduate School of Biomedical Sciences, Tokushima, Japan
- Department of Neurology, Utano National Hospital, Kyoto, Japan
| | - Masahiro Sonoo
- Department of Neurology, Teikyo University School of Medicine, Tokyo, Japan
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Hachisuka A, Ming Chan K. A modified multiple point stimulation method for motor unit number estimation of the hypothenar muscles. Muscle Nerve 2018; 59:337-341. [PMID: 30488459 DOI: 10.1002/mus.26391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 11/18/2018] [Accepted: 11/21/2018] [Indexed: 12/13/2022]
Abstract
INTRODUCTION The goal of this study is to test the hypothesis that single motor unit action potentials (SMUPs) originating from other ulnar nerve-innervated intrinsic hand muscles can inflate the motor unit number estimation (MUNE) of the hypothenar muscles. METHODS Using the multiple point stimulation method, SMUPs recorded over the hypothenar muscles from distant origins were characterized through multichannel recordings. The MUNE calculated using only the hypothenar SMUPs was compared with estimations based on the whole ensemble. RESULTS Of the 41 studies performed, distant SMUPs represented 17 ± 9.5% (mean ± SD) of the overall sample. MUNE calculated using only hypothenar SMUPs was 423 ± 204, compared with 537 ± 290 if all SMUPs were included (P < 0.05). The extent of increase in MUNE was highly correlated with the proportion of distant SMUPs found (r = 0.89, P < 0.05). DISCUSSION Erroneous inclusion of SMUPs from distant muscles can significantly distort the MUNE results. Muscle Nerve 59:337-341, 2019.
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Affiliation(s)
- Akiko Hachisuka
- Division of Physical Medicine and Rehabilitation, University of Alberta, 5005 Katz Group Centre, Edmonton, Alberta, T6G 2E1, Canada.,Department of Rehabilitation Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - K Ming Chan
- Division of Physical Medicine and Rehabilitation, University of Alberta, 5005 Katz Group Centre, Edmonton, Alberta, T6G 2E1, Canada.,Division of Plastic Surgery, University of Alberta, Edmonton, Alberta, Canada
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Higashihara M, Menon P, van den Bos M, Geevasinga N, Vucic S. Reproducibility of motor unit number index and multiple point stimulation motor unit number estimation in controls. Muscle Nerve 2018; 58:660-664. [PMID: 30194855 DOI: 10.1002/mus.26339] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/04/2018] [Indexed: 12/13/2022]
Abstract
INTRODUCTION Reproducibility of the multiple point stimulation motor unit number estimation (MPS-MUNE) technique was compared with the recently developed motor unit number index (MUNIX) technique. METHODS MPS-MUNE and MUNIX were performed on 15 healthy subjects at 3 different time-points by the same examiner. Reproducibility was analyzed using intraclass correlation coefficient (ICC) and coefficient of variation (CV). RESULTS ICC values for MUNIX and MPS-MUNE were excellent across 3 tests (0.80 and 0.77, respectively), although CV values were significantly lower for MUNIX than MPS-MUNE (P < 0.01). In addition, test-retest reproducibility was better for MUNIX, a finding largely attributable to poor reproducibility of the single motor unit action potential area. MUNIX (R = -0.48, P < 0.05) and MPS-MUNE (R = -0.53, P < 0.05) were significantly correlated with age. DISCUSSION MUNIX demonstrated better intrarater reproducibility and may be a more reliable neurophysiological biomarker than MPS-MUNE. Muscle Nerve 58: 660-664, 2018.
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Affiliation(s)
- Mana Higashihara
- Department of Neurology, Westmead Hospital, Sydney, New South Wales, Australia
| | - Parvathi Menon
- Westmead Clinical School, Cnr. Hawkesbury and Darcy Road, University of Sydney, New South Wales, 2145, Australia
| | - Mehdi van den Bos
- Westmead Clinical School, Cnr. Hawkesbury and Darcy Road, University of Sydney, New South Wales, 2145, Australia
| | - Nimeshan Geevasinga
- Westmead Clinical School, Cnr. Hawkesbury and Darcy Road, University of Sydney, New South Wales, 2145, Australia
| | - Steve Vucic
- Westmead Clinical School, Cnr. Hawkesbury and Darcy Road, University of Sydney, New South Wales, 2145, Australia
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Reproducibility, and sensitivity to motor unit loss in amyotrophic lateral sclerosis, of a novel MUNE method: MScanFit MUNE. Clin Neurophysiol 2017; 128:1380-1388. [DOI: 10.1016/j.clinph.2017.03.045] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/20/2017] [Accepted: 03/27/2017] [Indexed: 11/18/2022]
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Systemic, postsymptomatic antisense oligonucleotide rescues motor unit maturation delay in a new mouse model for type II/III spinal muscular atrophy. Proc Natl Acad Sci U S A 2015; 112:E5863-72. [PMID: 26460027 DOI: 10.1073/pnas.1509758112] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Clinical presentation of spinal muscular atrophy (SMA) ranges from a neonatal-onset, very severe disease to an adult-onset, milder form. SMA is caused by the mutation of the Survival Motor Neuron 1 (SMN1) gene, and prognosis inversely correlates with the number of copies of the SMN2 gene, a human-specific homolog of SMN1. Despite progress in identifying potential therapies for the treatment of SMA, many questions remain including how late after onset treatments can still be effective and what the target tissues should be. These questions can be addressed in part with preclinical animal models; however, modeling the array of SMA severities in the mouse, which lacks SMN2, has proven challenging. We created a new mouse model for the intermediate forms of SMA presenting with a delay in neuromuscular junction maturation and a decrease in the number of functional motor units, all relevant to the clinical presentation of the disease. Using this new model, in combination with clinical electrophysiology methods, we found that administering systemically SMN-restoring antisense oligonucleotides (ASOs) at the age of onset can extend survival and rescue the neurological phenotypes. Furthermore, these effects were also achieved by administration of the ASOs late after onset, independent of the restoration of SMN in the spinal cord. Thus, by adding to the limited repertoire of existing mouse models for type II/III SMA, we demonstrate that ASO therapy can be effective even when administered after onset of the neurological symptoms, in young adult mice, and without being delivered into the central nervous system.
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Simon NG, Ralph JW, Lomen-Hoerth C, Poncelet AN, Vucic S, Kiernan MC, Kliot M. Quantitative ultrasound of denervated hand muscles. Muscle Nerve 2015; 52:221-30. [DOI: 10.1002/mus.24519] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/10/2014] [Indexed: 12/12/2022]
Affiliation(s)
- Neil G. Simon
- Department of Neurology; University of California; San Francisco, San Francisco California USA
- Neuroscience Research Australia; PO Box 1165, Randwick NSW 2031 Australia
- Prince of Wales Clinical School, University of New South Wales; Australia
| | - Jeffrey W. Ralph
- Department of Neurology; University of California; San Francisco, San Francisco California USA
| | - Catherine Lomen-Hoerth
- Department of Neurology; University of California; San Francisco, San Francisco California USA
| | - Ann N. Poncelet
- Department of Neurology; University of California; San Francisco, San Francisco California USA
| | - Steve Vucic
- Neuroscience Research Australia; PO Box 1165, Randwick NSW 2031 Australia
- Westmead Clinical School; C24 Westmead Hospital; The University of Sydney; NSW 2006 Australia
| | - Matthew C. Kiernan
- Brain and Mind Research Institute, The University of Sydney; Mallett St Camperdown Australia
| | - Michel Kliot
- Department of Neurological Surgery; Northwestern Feinberg School of Medicine; Chicago Illinois USA
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Gooch CL, Doherty TJ, Ming Chan K, Bromberg MB, Lewis RA, Stashuk DW, Berger MJ, Andary MT, Daube JR. Reply to reflection on MUNE. Muscle Nerve 2015; 51:624. [PMID: 25620429 DOI: 10.1002/mus.24585] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 01/20/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Clifton L Gooch
- Department of Neurology, University of South Florida, Tampa, Florida, U.S.A
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Abstract
Motor unit number estimation (MUNE) is an electrophysiological method designed to quantify motor unit loss in target muscles of interest. Most of the techniques are noninvasive and are therefore well suited for longitudinal monitoring. In this brief review, we describe the more commonly used techniques and their applications in amyotrophic lateral sclerosis, poliomyelitis, spinal muscular atrophy and hereditary sensorimotor neuropathies. Findings in some of these studies offer important pathophysiological insights. Since conventional electrophysiologic methods are not sensible measures of motor neuronal loss, MUNE could play a potentially important role in the diagnosis, monitoring of disease progression and response to treatment in neuromuscular diseases in which motor unit loss is a major feature.
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Gooch CL, Doherty TJ, Chan KM, Bromberg MB, Lewis RA, Stashuk DW, Berger MJ, Andary MT, Daube JR. Motor unit number estimation: A technology and literature review. Muscle Nerve 2014; 50:884-93. [PMID: 25186553 DOI: 10.1002/mus.24442] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2014] [Indexed: 12/12/2022]
Affiliation(s)
- Clifton L. Gooch
- Department of Neurology; University of South Florida; Tampa Florida USA
| | - Timothy J. Doherty
- Department of Physical Medicine and Rehabilitation; University of Western Ontario; London Ontario Canada
- Department of Clinical Neurological Sciences; University of Western Ontario; London Ontario Canada
- Schulich School of Medicine and Dentistry; University of Western Ontario; London Ontario Canada
| | - K. Ming Chan
- Division of Physical Medicine and Rehabilitation/Centre for Neuroscience; University of Alberta; Edmonton Alberta Canada
| | - Mark B. Bromberg
- Department of Neurology; University of Utah; Salt Lake City Utah USA
| | - Richard A. Lewis
- Department of Neurology; Cedars-Sinai; Los Angeles California USA
| | - Dan W. Stashuk
- Systems Design Engineering; University of Waterloo; Waterloo Ontario Canada
| | - Michael J. Berger
- School of Kinesiology; University of Western Ontario; London Ontario Canada
- Schulich School of Medicine and Dentistry; University of Western Ontario; London Ontario Canada
| | - Michael T. Andary
- College of Osteopathic Medicine; Michigan State University; East Lansing Michigan USA
| | - Jasper R. Daube
- Department of Neurology; Mayo Clinic; Rochester Minnesota USA
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Unlusoy Acar Z, Yalinay Dikmen P, Yayla V, Başaran K, Emekli U, Öge AE. Decline of compound muscle action potentials and statistical MUNEs during Wallerian degeneration. Neurophysiol Clin 2014; 44:257-65. [PMID: 25240559 DOI: 10.1016/j.neucli.2014.04.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2012] [Revised: 01/21/2014] [Accepted: 04/12/2014] [Indexed: 12/12/2022] Open
Abstract
AIM OF THE STUDY In two previous studies, we found that the compound muscle action potential (CMAP) amplitude loss was significantly higher than the loss of estimated motor unit numbers in the course of Wallerian degeneration (WD). In order to overcome some drawbacks of the method previously used, we performed a similar CMAP vs MUNE comparison by using the statistical motor unit number estimation (MUNE) method. PATIENTS AND METHODS Initial electrophysiological studies on 6 patients were performed between 22 and 98 hours after the injuries; it was possible to make repeated examinations, four times in 1 nerve, twice in 1 nerve and three times in 4 nerves, before the eventual complete disappearance of the CMAPs. RESULTS The transected/intact (T/I) side CMAP ratios declined steeply as WD evolved. They were significantly lower than the relatively stable MUNE ratios 48 hours after the injury. CONCLUSION This study, performed with the use of statistical MUNE, strengthens our previous observation by the incremental method that might have some relevance to the pathophysiology of early WD. CMAP amplitude loss that is more than expected from the amount of axonal degeneration may indicate a considerable amount of inactive muscle fibers in the motor units innervated by the nerve fibers, which are undergoing degeneration but still retain their excitability. Although technical sources of error cannot be totally excluded, our findings could more likely be explained by the failing of neuromuscular synapses in an asynchronous order before complete unresponsiveness of the motor unit ensues.
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Affiliation(s)
- Z Unlusoy Acar
- Department of Neurology, TDV 29 May Hospital, 34091 Istanbul, Turkey
| | - P Yalinay Dikmen
- Department of Neurology, Acıbadem University School of Medicine, 34140 Istanbul, Turkey.
| | - V Yayla
- Department of Neurology, Dr. Sadi Konuk Bakırköy Education and Research Hospital, 34147 Istanbul, Turkey
| | - K Başaran
- Department of Plastic and Reconstructive Surgery, Istanbul University, Istanbul Faculty of Medicine, 34390 Istanbul, Turkey
| | - U Emekli
- Department of Plastic and Reconstructive Surgery, Istanbul University, Istanbul Faculty of Medicine, 34390 Istanbul, Turkey
| | - A E Öge
- Department of Neurology, Istanbul University, Istanbul Faculty of Medicine, 34390 Istanbul, Turkey
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Furtula J, Johnsen B, Christensen PB, Pugdahl K, Bisgaard C, Christensen MK, Arentsen J, Frydenberg M, Fuglsang-Frederiksen A. MUNIX and incremental stimulation MUNE in ALS patients and control subjects. Clin Neurophysiol 2013; 124:610-8. [DOI: 10.1016/j.clinph.2012.08.023] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2012] [Revised: 08/15/2012] [Accepted: 08/19/2012] [Indexed: 10/27/2022]
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Handgrip maximal voluntary isometric contraction does not correlate with thenar motor unit number estimation. Neurol Res Int 2012; 2012:187947. [PMID: 22649725 PMCID: PMC3357599 DOI: 10.1155/2012/187947] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2011] [Revised: 02/09/2012] [Accepted: 02/21/2012] [Indexed: 12/11/2022] Open
Abstract
In slowly progressive conditions, such as motor neurone disease (MND), 50-80% of motor units may be lost before weakness becomes clinically apparent. Despite this, maximal voluntary isometric contraction (MVIC) has been reported as a clinically useful, reliable, and reproducible measure for monitoring disease progression in MND. We performed a study on a group of asymptomatic subjects that showed a lack of correlation between isometric grip strength and thenar MUNE. Motor unit number estimation (MUNE) estimates the number of functioning lower motor neurones innervating a muscle or a group of muscles. We used the statistical electrophysiological technique of MUNE to estimate the number of motor units in thenar group of muscles in 69 subjects: 19 asymptomatic Cu, Zn superoxide dismutase 1 (SOD 1) mutation carriers, 34 family controls, and 16 population controls. The Jamar hand dynamometer was used to measure isometric grip strength. This study suggests that MUNE is more sensitive for monitoring disease progression than maximal voluntary isometric contraction (MVIC), as MUNE correlates with the number of functional motor neurones. This supports the observation that patients with substantial chronic denervation can maintain normal muscle twitch tension until 50-80% of motor units are lost and weakness is detectable.
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Shefner JM, Watson ML, Simionescu L, Caress JB, Burns TM, Maragakis NJ, Benatar M, David WS, Sharma KR, Rutkove SB. Multipoint incremental motor unit number estimation as an outcome measure in ALS. Neurology 2011; 77:235-41. [PMID: 21676915 DOI: 10.1212/wnl.0b013e318225aabf] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Improved outcome measures are necessary to reduce sample size and increase power in amyotrophic lateral sclerosis (ALS) clinical trials. Motor unit number estimation (MUNE) is a potentially attractive tool. MUNE methods previously employed in multicenter trials exhibited excessive variability and were prone to artifact. OBJECTIVE To evaluate a modification of standard incremental MUNE in a multicenter natural history study of subjects with ALS. METHODS Fifty healthy subjects were evaluated twice and 71 subjects with ALS were studied repeatedly for up to 500 days. Side and nerve studied was based on clinical examination findings. Nerves were stimulated at 3 specified locations and 3 increments were obtained at each location. Average single motor unit action potential (SMUP) amplitude was calculated by adding the amplitude of the third increment at each location and dividing by 9; SMUP was divided into maximum CMAP amplitude to determine the MUNE. RESULTS Test-retest variability was 9% in normal subjects. Average MUNE for normal subjects was 225 (±87), and was 41.9 (±39) among subjects with ALS at baseline. Subjects with ALS showed clear decrements over time, with an overage rate of decline of approximately 9% per month. SMUP amplitude increased with time in a fashion consistent with the known pathophysiology of ALS. CONCLUSION Multipoint incremental MUNE has a number of attributes that make it attractive as an outcome measure in ALS and other diseases characterized by motor unit loss. It can be rapidly performed on any EMG machine and has repeatability and rates of decline that favorably compare to other previously described methods.
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Affiliation(s)
- J M Shefner
- Department of Neurology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
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Ahn SW, Kim SH, Kim JE, Kim SM, Kim SH, Park KS, Sung JJ, Lee KW, Hong YH. Reproducibility of the motor unit number index (MUNIX) in normal controls and amyotrophic lateral sclerosis patients. Muscle Nerve 2010; 42:808-13. [PMID: 20976784 DOI: 10.1002/mus.21765] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Suk-Won Ahn
- Department of Neurology, Chung-Ang University Hospital, Chung-Ang University College of Medicine, Seoul, Republic of Korea
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Blok J, van Dijk J, Drenthen J, Maathuis E, Stegeman D. Size does matter: The influence of motor unit potential size on statistical motor unit number estimates in healthy subjects. Clin Neurophysiol 2010; 121:1772-80. [DOI: 10.1016/j.clinph.2010.03.048] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2009] [Revised: 02/17/2010] [Accepted: 03/27/2010] [Indexed: 12/12/2022]
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de Carvalho M, Chio A, Dengler R, Hecht M, Weber M, Swash M. Neurophysiological measures in amyotrophic lateral sclerosis: Markers of progression in clinical trials. ACTA ACUST UNITED AC 2009; 6:17-28. [PMID: 16036422 DOI: 10.1080/14660820410020600] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In this review we evaluate clinical neurophysiological methods, originally described for use in diagnosis that can be applied to measurement of change during the progress of amyotrophic lateral sclerosis (ALS). Such measurements are potentially important in clinical trials, and also in clinical practice. We have assessed methods for lower and upper motor neuron function, including conventional EMG, nerve conduction and F-wave studies, the derived Neurophysiological Index, motor unit counting methods (MUNE), and transcranial magnetic motor cortex stimulation. We have also addressed the validity of measurements of electromechanical coupling. Methods for measuring muscle strength are beyond the scope of this review. We conclude that MUNE, M-wave amplitude and the Neurophysiological Index are sufficiently reliable, sensitive, and relevant to the clinical problem of ALS, to be used in clinical trials in the disease. Transcranial magnetic stimulation is of limited value, but a combination of the measurements made as part of this technique may also be useful. We conclude that clinical neurophysiological techniques should now be used in measuring change in clinical trials in ALS.
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Affiliation(s)
- Mamede de Carvalho
- Department of Neurology at Hospital de Santa Maria, Institute for Molecular Medecine, University of Lisbon, Portugal.
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Sartucci F, Maritato P, Moscato G, Orlandi G, Calabrese R, Domenici GL, Murri L. MOTOR UNIT NUMBER ESTIMATION (MUNE) AS A QUANTITATIVE MEASURE OF DISEASE PROGRESSION AND MOTOR UNIT REORGANIZATION IN AMYOTROPHIC LATERAL SCLEROSIS. Int J Neurosci 2009; 117:1229-36. [PMID: 17654089 DOI: 10.1080/00207450600936304] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Motor Unit Number Estimation (MUNE), a technique allowing to estimate the number of functioning Motor Units (MU) in single muscles, was used to score the disease's severity and progression rate in a group of 58 patients with Amyotrophic Lateral Sclerosis (ALS). All patients underwent MUNE in the abductor digiti minimi (ADM) muscle during the diagnostic work-up (T0), after three (T1) and six (T2) months. A significant loss [p < .001] of MU and a decrease [p < .001] of the maximal M wave area at T0 was found, whereas mean step area was increased [p < .001]. During the follow-up (T1 and T2), MU loss continued, maximal M wave decreased, and mean step area increased significantly. The results confirm that MUNE is a suitable tool to quantify the pathological changes in MU in patients with ALS.
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Affiliation(s)
- F Sartucci
- Department of Neuroscience, Clinical Neurophysiology, Pisa University Medical School, Pisa, Italy.
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Shefner JM. Statistical motor unit number estimation and ALS trials: the effect of motor unit instability. MOTOR UNIT NUMBER ESTIMATION (MUNE) AND QUANTITATIVE EMG - SELECTED PRESENTATIONS FROM THE SECOND INTERNATIONAL SYMPOSIUM ON MUNE AND QEMG, SNOWBIRD, UTAH, USA, 18–20 AUGUST 2006 2009; 60:135-41. [DOI: 10.1016/s1567-424x(08)00013-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Change in excitability of motor axons modifies statistical MUNE results. SUPPLEMENTS TO CLINICAL NEUROPHYSIOLOGY 2009; 60:27-37. [PMID: 20715364 DOI: 10.1016/s1567-424x(08)00002-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Motor unit number estimation (MUNE) techniques--whether they reflect a true motor unit count or some related index--should not be confounded by changes in the neuromuscular system other than a decline in the number of functional motor units. In neurodegenerative conditions such as amyotrophic lateral sclerosis (ALS), there is evidence of changes in the excitability of motor axons. If changes in axon excitability confound a particular MUNE technique, this would influence the use of that technique in ALS patients. We hypothesized on the basis of computational models that changes in axon membrane excitability would change the outcome of a statistical MUNE test, even though the true number of motor units remained unchanged. To test the validity of the model predictions we induced changes in axon excitability of healthy control subjects by applying a polarizing current while simultaneously carrying out a statistical MUNE test. In a group of 7 subjects we found a significant difference in MUNE as a result of the change in axon excitability produced by the polarizing current (paired t-test, P < 0.05). We conclude that the statistical MUNE method is confounded by changes in axon excitability. Since increasing evidence shows that axon excitability is altered as part of the pathophysiological process underlying ALS, clinical researchers should be cautious when using statistical MUNE with this patient population.
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Abstract
Clinical trials in amyotrophic lateral sclerosis have significantly evolved over the last decade. New outcome measures have been developed that have reduced the sample size requirement as compared with survival studies. There has been increasing recognition that dose-ranging studies are crucial to full evaluation of experimental agents. While the requirements of late stage trials have not changed, many new designs have been suggested for earlier phase development. While no design achieves the perfect balance of sensitivity and efficiency, clinical trialists continue to work toward the goals of smaller and shorter trials so that more compounds can be studied concurrently.
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Porter CL, Alvarez A, Jones KE, Ming Chan K. Test--retest reliability of a modified multiple point stimulation technique for motor unit number estimation. Clin Neurophysiol 2008; 119:2287-90. [PMID: 18768347 DOI: 10.1016/j.clinph.2008.07.219] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2007] [Revised: 07/09/2008] [Accepted: 07/24/2008] [Indexed: 11/17/2022]
Abstract
OBJECTIVE Multiple point stimulation (MPS) is a widely used technique to estimate the number of motor units in a muscle. Test-retest reliability must be high for the motor unit number estimates to be clinically useful. We hypothesized that the reliability of MPS can be improved by using a long stimulus pulse width (1ms), in addition to the standard 0.05ms pulse width. METHODS Median nerve innervated thenar muscles were examined in 11 young subjects, 27+/-3 (mean +/-SD) years old and in 5 elderly subjects, 71+/-11 years old. The experimenter conducted the studies twice on each subject. RESULTS Test-retest reliability, using the modified MPS technique, was substantially higher (Cronbach's alpha of 0.88) than using the standard method (Cronbach's alpha of 0.80) in the young subjects. In contrast, for the elderly subjects the test-retest reliability of MUNE was high for both the modified technique (Cronbach's alpha of 0.96) and the standard technique (Cronbach's alpha of 0.99). CONCLUSIONS Test-retest reliability of MPS can be significantly improved by using a long stimulus pulse width and the standard stimulus pulse width in younger subjects. However, this is not necessary in elderly subjects. SIGNIFICANCE The greater reliability of this modified MPS method should enhance its clinical utility.
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Affiliation(s)
- Cheryl L Porter
- Centre for Neuroscience, University of Alberta, 513 Heritage Medical Research Centre, Edmonton, AB, Canada T6G 2S2
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22
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Bromberg MB, Brownell AA. Motor unit number estimation in the assessment of performance and function in motor neuron disease. Phys Med Rehabil Clin N Am 2008; 19:509-32, ix. [PMID: 18625413 DOI: 10.1016/j.pmr.2008.02.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Motor unit number estimation (MUNE) is a unique electrophysiologic test used to estimate the number of surviving motor units in a muscle or group of muscles. It is used most frequently to monitor lower motor neuron loss in amyotrophic lateral sclerosis and spinal muscle atrophy. Of particular interest is its use as an endpoint measure in clinical trials for these diseases. This article describes the principles of MUNE and the factors that need to be considered, and reviews several techniques that have been used in clinical trials and in monitoring progression. It then reviews experience with MUNE in clinical trials for amyotrophic lateral sclerosis and spinal muscle atrophy and discusses how MUNE correlates with measures of function.
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Affiliation(s)
- Mark B Bromberg
- Clinical Neuroscience Center, Department of Neurology, University of Utah Health Sciences Center, 175 North Medical Drive, Salt Lake City, UT 84132, USA.
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23
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Shefner JM, Cudkowicz ME, Zhang H, Schoenfeld D, Jillapalli D. Revised statistical motor unit number estimation in the Celecoxib/ALS trial. Muscle Nerve 2007; 35:228-34. [PMID: 17058270 DOI: 10.1002/mus.20671] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Techniques to estimate motor unit number (MUNE) measure the number of functioning motor units in a muscle. As amyotrophic lateral sclerosis (ALS) is characterized by progressive motor unit loss, this disease offers an ideal setting for the use of MUNE. Statistical MUNE was employed in a recent multicenter trial of creatine in ALS, and was shown to be reliable, reproducible, and to decline with disease progression. However, motor unit amplitude stayed constant over 7 months, a finding believed to reflect an artifact of the method. The statistical method was revised to reflect more accurately the presence of larger motor units and employed in a 12-month study of Celecoxib in ALS. MUNE declined by 49% in 12 months; however, motor unit amplitude again stayed constant over the same period. Statistical MUNE estimates motor unit number based on the variability of response to a repeated stimulus of constant strength, with an underlying assumption that this variability is due solely to the number of motor units responding in an intermittent manner. Based on studies showing that single motor units in ALS display excessive amplitude variability when stimulated repeatedly, we show that response variability in ALS patients is in large part due to single unit changes. Thus, we conclude that the statistical method is not an appropriate measure of motor unit number in any disease associated with motor unit instability.
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Affiliation(s)
- J M Shefner
- Department of Neurology, SUNY Upstate Medical University, Syracuse, New York 13210, USA.
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24
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Critères électro-neuro-myographiques de la sclérose latérale amyotrophique. Rev Neurol (Paris) 2006. [DOI: 10.1016/s0035-3787(06)75163-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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25
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Quels sont les critères électro-neuro-myographiques requis pour le diagnostic de SLA ? Rev Neurol (Paris) 2006. [DOI: 10.1016/s0035-3787(06)75164-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Boe SG, Stashuk DW, Doherty TJ. Within-subject reliability of motor unit number estimates and quantitative motor unit analysis in a distal and proximal upper limb muscle. Clin Neurophysiol 2006; 117:596-603. [PMID: 16442341 DOI: 10.1016/j.clinph.2005.10.021] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Revised: 10/11/2005] [Accepted: 10/30/2005] [Indexed: 11/29/2022]
Abstract
OBJECTIVE To establish within-subject reliability of motor unit number estimates (MUNEs) and quantitative MU analysis using decomposition-based quantitative electromyography (DQEMG). METHODS Following the acquisition of a maximum M-wave, needle and surface-detected EMG signals were collected during contractions of the first dorsal interrosseous (FDI) and biceps brachii (BB). DQEMG was used to extract motor unit potential (MUP) trains and surface-detected MUPs associated with each train, the mean size of which was divided into the maximum M-wave to obtain a MUNE. Retests were performed following the initial test to evaluate reliability. RESULTS Subjects test-retest MUNEs were highly correlated (r=0.72 FDI; 0.97 BB) with no significant differences between test and retest MUNE values (P>0.10). Ninety-five percent confidence intervals were calculated to establish the range of expected retest MUNE variability and were +/-41 MUs for the FDI and BB. Quantitative information pertaining to MU size, complexity and firing rate were similar for both tests. CONCLUSION MUNEs and quantitative MU data can be obtained reliably from the BB and FDI using DQEMG in individual subjects. SIGNIFICANCE Establishing within-subject reliability of MUNEs and quantitative MU analysis allow clinicians to longitudinally follow changes in the MU pool of individuals with disorders of the central or peripheral nervous system in addition to assessing their response to treatments.
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Affiliation(s)
- Shaun G Boe
- School of Kinesiology, The University of Western Ontario, Ont., Canada
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27
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Chapter 2 Physiology and function. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/s1567-4231(09)70063-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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28
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Affiliation(s)
- K R Mills
- Department of Clinical Neurophysiology, King's College Hospital, Denmark Hill, London SE5 9RS, UK.
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29
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Winhammar JMC, Rowe DB, Henderson RD, Kiernan MC. Assessment of disease progression in motor neuron disease. Lancet Neurol 2005; 4:229-38. [PMID: 15778102 DOI: 10.1016/s1474-4422(05)70042-9] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Motor neuron disease (MND) is characterised by progressive deterioration of the corticospinal tract, brainstem, and anterior horn cells of the spinal cord. There is no pathognomonic test for the diagnosis of MND, and physicians rely on clinical criteria-upper and lower motor neuron signs-for diagnosis. The presentations, clinical phenotypes, and outcomes of MND are diverse and have not been combined into a marker of disease progression. No single algorithm combines the findings of functional assessments and rating scales, such as those that assess quality of life, with biological markers of disease activity and findings from imaging and neurophysiological assessments. Here, we critically appraise developments in each of these areas and discuss the potential of such measures to be included in the future assessment of disease progression in patients with MND.
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Affiliation(s)
- Jennica M C Winhammar
- Department of Neurology and Multidisciplinary Motor Neurone Disease Clinic, Royal North Shore Hospital, NSW, Australia
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30
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Abstract
Motor unit number estimation (MUNE) is an electrodiagnostic procedure used to evaluate the number of motor axons connected to a muscle. All MUNE techniques rely on assumptions that must be fulfilled to produce a valid estimate. As there is no gold standard to compare the MUNE techniques against, we have developed a model of the relevant neuromuscular physiology and have used this model to simulate various MUNE techniques. The model allows for a quantitative analysis of candidate MUNE techniques that will hopefully contribute to consensus regarding a standard procedure for performing MUNE.
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Affiliation(s)
- Lora A Major
- Department of Biomedical Engineering, University of Alberta, Edmonton, Canada
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31
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Blok JH, Visser GH, de Graaf S, Zwarts MJ, Stegeman DF. Statistical motor unit number estimation assuming a binomial distribution. Muscle Nerve 2005; 31:182-91. [PMID: 15736298 DOI: 10.1002/mus.20256] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The statistical method of motor unit number estimation (MUNE) uses the natural stochastic variation in a muscle's compound response to electrical stimulation to obtain an estimate of the number of recruitable motor units. The current method assumes that this variation follows a Poisson distribution. We present an alternative that instead assumes a binomial distribution. Results of computer simulations and of a pilot study on 19 healthy subjects showed that the binomial MUNE values are considerably higher than those of the Poisson method, and in better agreement with the results of other MUNE techniques. In addition, simulation results predict that the performance in patients with severe motor unit loss will be better for the binomial than Poisson method. The adapted method remains closer to physiology, because it can accommodate the increase in activation probability that results from rising stimulus intensity. It does not need recording windows as used with the Poisson method, and is therefore less user-dependent and more objective and quicker in its operation. For these reasons, we believe that the proposed modifications may lead to significant improvements in the statistical MUNE technique.
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Affiliation(s)
- Joleen H Blok
- Department of Clinical Neurophysiology, Erasmus Medical Center, Rotterdam, The Netherlands.
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Shefner JM, Cudkowicz ME, Zhang H, Schoenfeld D, Jillapalli D. The use of statistical MUNE in a multicenter clinical trial. Muscle Nerve 2004; 30:463-9. [PMID: 15316983 DOI: 10.1002/mus.20120] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Techniques to estimate motor unit number (MUNE) measure the number of functioning motor units in a muscle. In diseases characterized by progressive motor unit loss, such as amyotrophic lateral sclerosis (ALS), MUNE may be useful to monitor disease progression or beneficial response to treatment. As part of a multicenter, placebo-controlled, randomized, double-blind clinical trial testing the efficacy of creatine in patients with ALS, statistical MUNE was measured in 104 patients tested monthly for 6 months. The objective was to determine whether MUNE was a reliable and sensitive outcome measure in the context of a multicenter trial. Formal training and reliability testing was required for all MUNE evaluators. Testing of normal controls showed a high degree of test-retest reliability. All patient data were combined as the experimental treatment showed no efficacy. There was a 23% decline in MUNE over 6 months. The technique as employed in this trial overemphasized the presence of small motor units; this problem was partially addressed by poststudy data monitoring and censuring. Thus, MUNE can be used reliably as an outcome measure in multicenter clinical trials; specific remedies are suggested for the difficulties encountered in this study.
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Affiliation(s)
- J M Shefner
- Department of Neurology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA.
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33
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Jillapalli D, Shefner JM. Single motor unit variability with threshold stimulation in patients with amyotrophic lateral sclerosis and normal subjects. Muscle Nerve 2004; 30:578-84. [DOI: 10.1002/mus.20147] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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34
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Cudkowicz M, Qureshi M, Shefner J. Measures and markers in Amyotrophic Lateral Sclerosis. Neurotherapeutics 2004. [DOI: 10.1007/bf03206611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Abstract
Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disorder characterized by loss of spinal and cortical motor neurons, leading to progressive weakness and ultimately, death. Clinically, there appears to be an anatomic focus at disease onset, from which the disease then spreads. Because the focus of initial symptoms and the subsequent direction of spread can vary from patient to patient, disease monitoring is difficult, especially in a clinical trial, in which outcome measures must be identical and able to capture progression of all types. Thus, the search for markers of disease progression is especially important in ALS. Many approaches have been taken, from voluntary strength assessment and functional rating scales to physiological and pathological sampling of affected portions of nervous system. No proposed marker has been demonstrated to meet the desired criteria of biological meaning, sensitivity to disease progression, clear relationship to overall prognosis and survival, and ease of measurement. However, progress is being made in all of these regards.
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Affiliation(s)
- Merit Cudkowicz
- Neurology Clinical Trial Unit, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
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36
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Kwon O, Lee KW. Reproducibility of statistical motor unit number estimates in amyotrophic lateral sclerosis: Comparisons between size- and number-weighted modifications. Muscle Nerve 2004; 29:211-7. [PMID: 14755485 DOI: 10.1002/mus.10530] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Motor unit number estimations (MUNEs) can directly assess motor unit populations in muscle and quantify the degree of physiological or pathological motor unit degeneration. A high degree of reproducibility and reliability is required of any effective quantitative tool. MUNE is being increasingly applied clinically, and statistical MUNE has several advantages over alternative techniques. Nevertheless, the optimal method of applying statistical MUNE with respect to its reproducibility has not been established. We performed statistical MUNE by selecting the most compensated compound muscle action potential (CMAP) area as a test area and modified the results obtained by using the weighted mean surface-recorded motor unit potential (SMUP). MUNE measurements made in patients with amyotrophic lateral sclerosis (ALS) showed better reproducibility after incorporating the size-weighted modification. Therefore, we suggest that the size-weighted MUNE in combination with the selection of testing "neurogenically compensated" CMAP areas is a more reliable method of statistical MUNE analysis in ALS patients.
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Affiliation(s)
- Ohyun Kwon
- Department of Neurology, Eulji General Hospital, Eulji University School of Medicine, Seoul, Korea
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37
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Boe SG, Stashuk DW, Doherty TJ. Motor unit number estimation by decomposition-enhanced spike-triggered averaging: Control data, test-retest reliability, and contractile level effects. Muscle Nerve 2004; 29:693-9. [PMID: 15116373 DOI: 10.1002/mus.20031] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Decomposition-enhanced spike-triggered averaging (DE-STA) has been developed as a method for obtaining a motor unit number estimate (MUNE). We describe the method and report control data for the first dorsal interosseous/adductor pollicis and thenar muscles and reliability in the thenar muscles. Seventeen subjects (ages 20-50 years) took part in the study. The maximum M potential was elicited with supramaximal stimulation of the ulnar or median nerve at the wrist. Surface and intramuscularly detected electromyographic signals were then collected simultaneously during mild to moderate contractions. Decomposition algorithms were used to detect and sort the individual motor unit potential (MUP) occurrences of several concurrently active motor units in the needle-detected signals. The MUP occurrences were used as triggering sources to estimate their corresponding surface-detected MUPs (S-MUPs) using STA. The mean S-MUP size was calculated and divided into the maximum M-potential size to derive a MUNE. The MUNE values were consistent with those previously reported with other methods, and thenar MUNEs for the two trials were similar (249 +/- 78 and 246 +/- 90), with high test-retest reliability (r = 0.94, P < 0.05). DE-STA thus appears to be a valid and reliable method to obtain MUNEs.
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Affiliation(s)
- Shaun G Boe
- School of Kinesiology, University of Western Ontario, London, Ontario, Canada
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38
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Bromberg MB. Motor unit number estimation: new techniques and new uses. SUPPLEMENTS TO CLINICAL NEUROPHYSIOLOGY 2004; 57:120-36. [PMID: 16106613 DOI: 10.1016/s1567-424x(09)70350-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
MUNE is a unique neurophysiologic tool because it can quantitatively estimate the number of motor neurons innervating a muscle or group of muscles. All other neurophysiologic techniques are influenced by collateral reinnervation and provide only a qualitative estimate of motor unit loss. Further, the S-MUPs obtained with MUNE provide quantitative information about the whole motor unit. Other routine neurophysiologic techniques provide information restricted to a portion of the motor unit. These unique features of MUNE have been applied to neurogenic disorders to yield a better understanding of disease processes. Various modifications are being developed that will provide more data and ease of use. It is anticipated that the availability of MUNE on EMG machines will grow and it use will expand from a research tool to a routine neurophysiologic test.
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Affiliation(s)
- Mark B Bromberg
- Department of Neurology, University of Utah School of Medicine, Room 3R152, 50 North Medical Drive, Salt Lake City, UT 84109, USA.
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39
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Lomen-Hoerth C, Slawnych MP. Statistical motor unit number estimation: from theory to practice. Muscle Nerve 2003; 28:263-72. [PMID: 12929186 DOI: 10.1002/mus.10351] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Statistical motor unit number estimation (MUNE) is one of several experimental techniques used to estimate the number of lower motor neurons innervating a given muscle. All are fairly reproducible and have been applied successfully in monitoring neurogenic disease progression. Quantitating the number of lower motor neurons is important, since the compound muscle action potential (CMAP) and strength may not change as rapidly over time due to the confounding effect of reinnervation. MUNE techniques differ in the way they obtain samples of surface-recorded motor unit potentials (SMUP). Statistical MUNE is based on Poisson statistics, uses surface stimulation, and is useful in testing distal, superficial nerves. This review focuses on the theory behind the development of the technique, critiques the publications resulting from applying the technique in control and disease subjects, and discusses the future developments needed for clinical utility.
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Affiliation(s)
- Catherine Lomen-Hoerth
- Department of Neurology, University of California, San Francisco, 505 Parnassus Avenue, Room M348, San Francisco, California 94143, USA.
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40
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Jillapalli D, Bradshaw DY, Shefner JM. Motor unit number estimation in the evaluation of focal conduction block. Muscle Nerve 2003; 27:676-81. [PMID: 12766978 DOI: 10.1002/mus.10367] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Temporal dispersion and phase cancellation limit the utility of amplitude reduction in compound muscle action potential (CMAP) as a measure of focal conduction block but may not affect motor unit number estimation (MUNE). Hence, MUNE offers the potential of a specific measure of conduction block. We investigated the role of MUNE in 11 patients with ulnar neuropathy and conduction block at the elbow and also in 8 normal subjects. MUNE failed to detect motor unit dropout in the patient group because reduced values for surface-recorded motor unit potentials (SMUPs) were obtained at proximal locations, suggesting that focal compression selectively damages larger motor axons, an hypothesis that has support from animal studies. We conclude that, because MUNE is affected by the physiological characteristics of functional axons surviving the underlying pathological process, the utility of MUNE is limited to diseases in which the expected pathology affects motor axons uniformly.
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Affiliation(s)
- Devanand Jillapalli
- Department of Neurology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA.
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Abstract
Since its introduction 30 years ago, MUNE techniques have increasingly been refined and applied to a wide variety of neuromuscular disorders. Differences of opinion remain among MUNE investigators as to which method is best; however, statistical and MPS MUNE are currently the most widely used. Numerous methodologic issues remain, including the development of detailed universal standards for each technique and the implementation of modifications for the enhancement of reproducibility. These issues are the subjects of ongoing investigation. Despite technical variability, the MUNE values obtained using different methods show good agreement in studies of normal subjects and in patients with a variety of neurogenic processes. MUNE has been applied most successfully to patients with amyotrophic lateral sclerosis and to animal models of motor neuron disease, providing significant insight into the pathophysiology of these disorders. These techniques are increasingly being incorporated into clinical therapeutic trials. MUNE offers promise in the study of neuromuscular disease, enabling the collection of novel data in the living patient unobtainable by any other method.
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Affiliation(s)
- Jeremy M Shefner
- Clinical Neurophysiology Laboratory, MDA/ALS Research and Treatment Center, Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
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42
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Henderson RD, McClelland R, Daube JR. Effect of changing data collection parameters on statistical motor unit number estimates. Muscle Nerve 2003; 27:320-31. [PMID: 12635119 DOI: 10.1002/mus.10325] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The effect of number of samples and selection of data for analysis on the calculation of surface motor unit potential (SMUP) size in the statistical method of motor unit number estimates (MUNE) was determined in 10 normal subjects and 10 with amyotrophic lateral sclerosis (ALS). We recorded 500 sequential compound muscle action potentials (CMAPs) at three different stable stimulus intensities (10-50% of maximal CMAP). Estimated mean SMUP sizes were calculated using Poisson statistical assumptions from the variance of 500 sequential CMAP obtained at each stimulus intensity. The results with the 500 data points were compared with smaller subsets from the same data set. The results using a range of 50-80% of the 500 data points were compared with the full 500. The effect of restricting analysis to data between 5-20% of the CMAP and to standard deviation limits was also assessed. No differences in mean SMUP size were found with stimulus intensity or use of different ranges of data. Consistency was improved with a greater sample number. Data within 5% of CMAP size gave both increased consistency and reduced mean SMUP size in many subjects, but excluded valid responses present at that stimulus intensity. These changes were more prominent in ALS patients in whom the presence of isolated SMUP responses was a striking difference from normal subjects. Noise, spurious data, and large SMUP limited the Poisson assumptions. When these factors are considered, consistent statistical MUNE can be calculated from a continuous sequence of data points. A 2 to 2.5 SD or 10% window are reasonable methods of limiting data for analysis.
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Affiliation(s)
- Robert D Henderson
- Department of Neurology, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905, USA
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43
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Olney RK. Motor Unit Number Estimation (MUNE): pro. AMYOTROPHIC LATERAL SCLEROSIS AND OTHER MOTOR NEURON DISORDERS : OFFICIAL PUBLICATION OF THE WORLD FEDERATION OF NEUROLOGY, RESEARCH GROUP ON MOTOR NEURON DISEASES 2003; 3 Suppl 1:S91-2. [PMID: 12396820 DOI: 10.1080/146608202320374417] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Richard K Olney
- ALS Center, University of California, San Francisco, CA, USA
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44
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Shefner JM. Motor unit number estimation: summary. AMYOTROPHIC LATERAL SCLEROSIS AND OTHER MOTOR NEURON DISORDERS : OFFICIAL PUBLICATION OF THE WORLD FEDERATION OF NEUROLOGY, RESEARCH GROUP ON MOTOR NEURON DISEASES 2003; 3 Suppl 1:S97-102. [PMID: 12396823 DOI: 10.1080/146608202320374444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Gooch CL. Motor unit number estimation: pro. AMYOTROPHIC LATERAL SCLEROSIS AND OTHER MOTOR NEURON DISORDERS : OFFICIAL PUBLICATION OF THE WORLD FEDERATION OF NEUROLOGY, RESEARCH GROUP ON MOTOR NEURON DISEASES 2003; 3 Suppl 1:S93-4. [PMID: 12396821 DOI: 10.1080/146608202320374426] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Motor unit number index (MUNIX): a pilot study. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s1567-424x(02)55014-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Abstract
The neurophysiology of amyotrophic lateral sclerosis is important not only in relation to diagnosis, but also in the development of methods to follow progress, and the effects of putative therapies, in the disease. Quantitative techniques can be applied to the measurement of reinnervation using needle electromyogram. The methodology of motor unit number estimation may be useful in measuring loss of functioning motor units in groups of patients but variability in the measurement using current methods limits its sensitivity in the evaluation of individual patients. Conventional neurophysiological measurements, expressed as a multimetric index, may be useful in assessing progress. The cortical and upper motor neuron system can be assessed using transcortical magnetic stimulation protocols, and cortical excitability may be measured by the peristimulus histogram method. In this review the advantages, limitations and promise of these various methods is discussed, in order to indicate the direction for further neurophysiological studies in this disorder.
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Affiliation(s)
- A Eisen
- Neuromuscular Diseases Unit, Vancouver General Hospital, 1st Floor Willow Pavillion, 855 West 12th Avenue, British Columbia, V5Z 1M9, Vancouver, Canada.
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48
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Lomen-Hoerth C, Olney RK. Effect of recording window and stimulation variables on the statistical technique of motor unit number estimation. Muscle Nerve 2001; 24:1659-64. [PMID: 11745975 DOI: 10.1002/mus.1201] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A variety of methods are used for the selection of recording window sizes and stimulation current levels for statistical motor unit number estimation (MUNE). This study compares different recording window sizes and stimulation current levels within those windows in the same subjects to determine the effect on MUNE value and reproducibility. Four recording windows of 10% size were compared with four of 5%, with the stimulation current set in the lower quarter, middle half, and upper quarter of the recording window. MUNE for stimulation current set in the lower quarter of the window was 81 (62-103) for 10% recording windows and 120 (108-135) for 5% recording windows, and 91 (61-123) and 133 (120-154) for stimulation current set in the middle half. Increasing the recording window size from 5 to 10% lowers the MUNE value in controls, but tends to improve reproducibility; and setting the stimulation current in the lower quarter of the window, changes the MUNE value minimally, while tending to improve further reproducibility. Excellent reproducibility of MUNE was obtained when applied to a pilot group of 10 amyotrophic lateral sclerosis patients. Based on this study, we conclude that the ideal method for statistical motor unit estimation involves using 10% recording windows and setting the stimulation current in the lower quarter of the recording window.
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Affiliation(s)
- C Lomen-Hoerth
- Department of Neurology, University of California, San Francisco, School of Medicine, 505 Parnassus Avenue, Room M348, San Francisco, California 94143-0114, USA.
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Abstract
Motor unit number estimation (MUNE) was introduced in 1971 as a way of providing an objective and meaningful estimate of axon loss in diseases affecting the motor system. Over the last 30 years, different methods of MUNE have been proposed, with each having specific strengths and limitations. The goal of this paper is to review the available methods, and to present data generated using MUNE in a variety of disease entities. The incremental, multiple point stimulation, spike-triggered averaging, F-wave, and statistical methods of MUNE are reviewed, along with data obtained using these methods in patients with neuropathy, motor neuron disorders, and muscle disease. All methods reviewed have theoretical concerns associated with them. However, with the exception of the spike-triggered averaging method, all give results in normal subjects that are quite similar. MUNE has been of great value in assessing progression of motor neuron disease, and has also shown promise in the assessment of generalized neuropathy. Despite the lack of a perfect method for performing MUNE, it has great clinical value in the assessment of progressive motor axon loss. Further refinements in the method will likely increase its utility in the future.
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Affiliation(s)
- J M Shefner
- Department of Neurology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
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