| 1. |
- Chan, Young, et al.
(författare)
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Reinnervation as measured by the motor unit size index is associated with preservation of muscle strength in amyotrophic lateral sclerosis, but not all muscles reinnervate
- 2022
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Ingår i: Muscle and Nerve. - : John Wiley & Sons. - 0148-639X .- 1097-4598. ; 65:2, s. 203-210
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Tidskriftsartikel (refereegranskat)abstract
- Introduction/Aims: The motor unit size index (MUSIX) may provide insight into reinnervation patterns in diseases such as amyotrophic lateral sclerosis (ALS). However, it is not known whether MUSIX detects clinically relevant changes in reinnervation, or if all muscles manifest changes in MUSIX in response to reinnervation after motor unit loss.Methods: Fifty-seven patients with ALS were assessed at 3-month intervals for 12 months in four centers. Muscles examined were abductor pollicis brevis, abductor digiti minimi, biceps brachii, and tibialis anterior. Results were split into two groups: muscles with increases in MUSIX and those without increases. Longitudinal changes in MUSIX, motor unit number index (MUNIX), compound muscle action potential amplitude, and Medical Research Council strength score were investigated.Results: One hundred thirty-three muscles were examined. Fifty-nine percent of the muscles exhibited an increase in MUSIX during the study. Muscles with MUSIX increases lost more motor units (58% decline in MUNIX at 12 months, P <.001) than muscles that did not increase MUSIX (34.6% decline in MUNIX at 12 months, P <.001). However, longitudinal changes in muscle strength were similar. When motor unit loss was similar, the absence of a MUSIX increase was associated with a significantly greater loss of muscle strength (P =.002).Discussion: MUSIX increases are associated with greater motor unit loss but relative preservation of muscle strength. Thus, MUSIX appears to be measuring a clinically relevant response that can provide a quantitative outcome measure of reinnervation in clinical trials. Furthermore, MUSIX suggests that reinnervation may play a major role in determining the progression of weakness.
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| 2. |
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| 3. |
- Nandedkar, Sanjeev D., et al.
(författare)
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Experiment for teaching virtual cathode in nerve conduction studies
- 2021
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Ingår i: Muscle and Nerve. - : John Wiley & Sons. - 0148-639X .- 1097-4598. ; 64:1, s. 86-89
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Tidskriftsartikel (refereegranskat)abstract
- Introduction/AimsThe virtual cathode (VC) is a site near the anode where the nerve can be stimulated. Costimulation of neighboring nerves via the VC can affect recording and interpretation of responses. Hence, it is important to teach trainees the concept of the VC. The VC has been demonstrated previously with subtle changes in response latency, amplitude, and shape. Herein we describe an experiment that simply demonstrates a VC with its effects recognizable by gross changes in waveforms.MethodsCompound muscle action potentials of the abductor pollicis brevis were recorded using various placements of the cathode and anode at different stimulus intensity levels. Studies were performed in nine healthy subjects.ResultsThree patterns were observed that demonstrated no stimulation, partial stimulation, and complete nerve stimulation by the VC. Partial stimulation yielded responses with long duration and low amplitude. Response patterns also depended on stimulus strength and proximity of the nerve from the skin surface.DiscussionThis experiment demonstrates that nerve stimulation can occur near the anode when high-intensity stimulus is used. It also illustrates collision of action potentials. This exercise can help trainees understand potential pitfalls in nerve conduction studies, especially at very proximal stimulation sites or when high stimulus intensity is used.
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| 4. |
- Nandedkar, Sanjeev D., et al.
(författare)
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Form factor analysis of the surface electromyographic interference pattern
- 2020
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Ingår i: Muscle and Nerve. - : WILEY. - 0148-639X .- 1097-4598. ; 62:2, s. 233-238
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Tidskriftsartikel (refereegranskat)abstract
- Introduction In contrast to needle electromyography (EMG), surface EMG recordings are painless. It is of interest to develop methods to analyze surface EMG for diagnostic purposes. Methods Surface EMG interference pattern (SIP) recordings from the abductor pollicis brevis muscle of healthy subjects and subjects with amyotrophic lateral sclerosis (ALS) were analyzed by measuring root-mean-square (RMS) voltage, mean rectified voltage, form factor (FF), and the clustering index (CI). The FF vs SIP area plot was used for analysis. Results The SIP FF was increased and abnormal in ALS subjects, especially when SIP area was less than 200 mVms. Power regression showed a faster FF decline with SIP area in ALS patients than in healthy subjects. The CI and FF showed a strong correlation. Discussion FF is easy to calculate and demonstrates abnormalities in ALS patients.
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| 5. |
- Nandedkar, Sanjeev D., et al.
(författare)
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MeRef : Multivariable extrapolated reference values in motor nerve conduction studies
- 2021
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Ingår i: Muscle and Nerve. - : John Wiley & Sons. - 0148-639X .- 1097-4598. ; 63:5, s. 737-744
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: In this study we describe a method called "multivariable extrapolated reference values" (MeRef) that derives reference values (RVs) using patient data and includes the dependence of these variables on multiple patient demographic variables, such as age and height. Methods: Computer simulations were used to generate "normal" and "patient" nerve conduction data. Median, ulnar, and tibial motor nerve conduction data from 500 patients studied were tabulated. Data were analyzed using the MeRef method. Results: The simulations showed great similarity between RVs obtained from MeRef of "patient" data and traditional analysis of "normal" data. In the real patient data, MeRef gave RVs as regression equations based on patient age and/or height. Discussion: MeRef can provide RVs by including patient demographic data and does not require subject grouping. It provides parameters of multivariable linear regression and standard deviation, and requires a few hundred patient studies to define reference values.
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| 6. |
- Nandedkar, Sanjeev D., et al.
(författare)
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Motor unit number index : Guidelines for recording signals and their analysis
- 2018
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 58:3, s. 374-380
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: This study proposes guidelines for motor unit number index (MUNIX) recording and analysis. Methods: MUNIX was measured in control participants and in patients with amyotrophic lateral sclerosis. Changes in MUNIX values due to E1 electrode position, number of surface electromyography interference pattern (SIP) epochs, SIP epoch duration, force of contraction, and outlier data points were investigated. Results: MUNIX depends on optimized compound muscle action potential (CMAP) amplitude. Individual muscles showed variations when the number of epochs was low or when the SIP duration was short. Longer SIP duration allowed better recognition of artifacts. MUNIX results were affected by SIP values at all force levels but was more affected when SIP area was low. Discussion: We recommend changing the E1 electrode position to maximize CMAP amplitude. Twenty or more SIP signals of 500-ms duration should be recorded by using force levels ranging from slight to maximum. Traces should be reviewed to identify and exclude signals with tremor or solitary spikes.
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| 7. |
- Nandedkar, Sanjeev D., et al.
(författare)
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Motor unit number index (MUNIX) : principle, method, and findings in healthy subjects and in patients with motor neuron disease
- 2010
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 42:5, s. 798-807
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Tidskriftsartikel (refereegranskat)abstract
- The motor unit number index (MUNIX) is a method for assessment of number and size (MUSIX) of motor units (MUs) using the compound muscle action potential (CMAP) and surface electromyographic interference pattern (SIP). This method was used to study the hypothenar muscle in 34 healthy subjects to define normal range, and to study reproducibility. Four healthy subjects and 13 patients with amyotrophic lateral sclerosis (ALS) were studied serially over a 1-year period. In healthy subjects, MUNIX showed good reproducibility. In serial studies, healthy subjects showed no change in the CMAP amplitude and MUNIX. ALS patients with minimal change in CMAP amplitude had a significant drop in MUNIX and increase in MUSIX, indicating MU loss compensated by reinnervation. When the CMAP changed significantly (>30%) in 1 year, the CMAP and MUNIX decreased in parallel. MUNIX would be useful to study MU loss in degenerative diseases of motor neurons.
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| 8. |
- Nandedkar, Sanjeev D., et al.
(författare)
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Motor unit recruitment and firing rate at low force of contraction
- 2022
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Ingår i: Muscle and Nerve. - : John Wiley & Sons. - 0148-639X .- 1097-4598. ; 66:6, s. 750-756
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Tidskriftsartikel (refereegranskat)abstract
- Introduction/Aims: A prevailing concept of motor unit (MU) recruitment used for calculating recruitment ratio (RR) suggests a progressive linear increase in firing rate (FR). The objective of this study is to assess its validity. Methods: Concentric needle electromyography (EMG) recordings were made in normal muscle and abnormal muscle of patients with neurogenic findings. Signals recorded at low force were visually decomposed to study MU FR at onset, recruitment of a second MU, and recruitment of more MUs with further increases in force. Results: We observed one to six MUs discharging at a rate < 15 Hz in normal muscles at low force. The MU FR was 5-8 Hz at onset. With increasing force, FR increased by 3-5 Hz and then idled at <15 Hz while other MUs were recruited. The recruitment frequency (RF) and RR had low sensitivity and were abnormal mainly in moderately to severely weak muscles. Discussion: Our data are consistent with FR analysis results described by other investigators. It does not support a progressive linear increase in MU FR with recruitment. A revised model for MU recruitment at low effort during gradual increase in force is presented. On subjective assessment, the FR of the fastest firing MU can help detect MU loss in neurogenic processes.
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| 9. |
- Nandedkar, Sanjeev D., et al.
(författare)
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Reproducibility of munix in patients with amyotrophic lateral sclerosis
- 2011
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 44:6, s. 919-922
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: In this study we investigated the reproducibility of motor unit number index (MUNIX) in patients with amyotrophic lateral sclerosis (ALS). Methods: MUNIX was recorded in patients with ALS. Studies were performed in 18 thenar and 18 hypothenar muscles by two operators. The reproducibility was assessed using mean MUNIX values, linear regression, correlation coefficient, and coefficient of variation (COV) in individual studies. Results: The mean values showed no significant difference. The linear regression showed a strong correlation. Most patients had low COV. A high COV was seen when MUNIX was very low. The COV was higher in thenar than in hypothenar muscles. Conclusions: MUNIX has very good reproducibility in ALS patients. COV may exaggerate interoperator variation when MUNIX is very low. The higher variability in the thenar muscle is also due to variability in compound muscle action potential amplitude. Although both muscles show good reproducibility, the hypothenar is better suited for serial studies in individual patients.
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| 10. |
- Nandedkar, Sanjeev D., et al.
(författare)
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THE EXTRAPOLATED REFERENCE VALUES PROCEDURE : THEORY, ALGORITHM, AND RESULTS IN PATIENTS AND CONTROL SUBJECTS
- 2018
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Ingår i: Muscle and Nerve. - : Wiley. - 0148-639X .- 1097-4598. ; 57:1, s. 90-95
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Reference values (RVs) are required to separate normal from abnormal values obtained in electrodiagnostic (EDx) testing. However, it is frequently impractical to perform studies on control subjects to obtain RVs. The Extrapolated Reference Values (E-Ref) procedure extracts RVs from data obtained during clinically indicated EDx testing. We compared the E-Ref results with established RVs in several sets of EDx data.Methods: The mathematical basis for E-Ref was explored to develop an algorithm for the E-Ref procedure. To test the validity of this algorithm, it was applied to simulated and real jitter measurements from control subjects and patients with myasthenia gravis, and to nerve conduction studies from patients with various conditions referred for EDx studies.Results: There was good concordance between E-Ref and RVs for all evaluated data sets.Discussion: E-Ref is a promising method to develop RVs.
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