Comparative assessment of MScanFit MUNE and quantitative EMG in amyotrophic lateral sclerosis diagnosis: A prospective study.

OBJECTIVE: Motor Unit Number Estimation (MUNE) techniques are crucial in assessing lower motor neuron loss. MScanFit MUNE (MScanFit) is a novel tool which estimates MUNE values from compound muscle action potential (CMAP) scans by considering the probabilistic nature of motor unit firing. We conducted a prospective study to evaluate the diagnostic utility of MScanFit compared to quantitative electromyography (qEMG) in ALS patients. METHODS: We enrolled 35 patients diagnosed with amyotrophic lateral sclerosis (ALS) and 14 healthy controls, assessing qEMG and MScanFit MUNE in abductor pollicis brevis, abductor digiti minimi and tibialis anterior muscles. RESULTS: We found higher sensitivity of qEMG in detecting abnormalities compared to MScanFit, with a high concordance rate between the two techniques. Notably, a few muscles exhibited abnormal MUNE but normal qEMG findings, suggesting a potential complementary role for MScanFit in ALS diagnosis. Neurophysiological parameters from MScanFit showed good correlations with qEMG measures. Subclinical neurophysiological involvement was observed in muscles with normal strength, emphasizing the importance of sensitive diagnostic tools. CONCLUSION: MScanFit demonstrated validity in distinguishing ALS patients from healthy subjects and correlated well with qEMG parameters. SIGNIFICANCE: Our study confirmed the diagnostic utility of MScanFit MUNE in ALS, highlighting its role as a supplementary diagnostic tool.

Exploring the peripheral mechanisms of lower limb immobilisation on muscle function using novel electrophysiological methods.

OBJECTIVE: To explore the effects of short-term immobilisation and subsequent retraining on peripheral nervous system (PNS) measures using two novel electrophysiological methods, muscle velocity recovery cycles (MVRC) and MScanFit motor unit number estimation (MUNE) alongside lower limb muscle strength, muscle imaging and walking capacity. METHODS: Twelve healthy participants underwent 1-week of ankle immobilisation and 2-weeks of retraining. Assessments before and after immobilisation, and after retraining, included MVRC [muscle membrane properties; muscle relative refractory period (MRRP), early and late supernormality], MScanFit, MRI-scans [muscle contractile cross-sectional area (cCSA)], isokinetic dynamometry [dorsal and plantar flexor muscle strength], and 2-minute maximal walk test [physical function]. RESULTS: After immobilisation, compound muscle action potential (CMAP) amplitude reduced (-1.35[-2.00;-0.69]mV); mean change [95%CI]) alongside reductions in plantar (but not dorsal) flexor muscle cCSA (-124[-246;3]mm2), dorsal flexor muscle strength (isometric -0.06[-0.10;-0.02]Nm/kg, dynamicslow -0.08[-0.11;-0.04]Nm/kg, dynamicfast no changes), plantar flexor muscle strength (isometric -0.20[-0.30;-0.10]Nm/kg, dynamicslow -0.19[-0.28;-0.09]Nm/kg, dynamicfast -0.12[-0.19;-0.05]Nm/kg) and walking capacity (-31[-39;-23]m). After retraining, all immobilisation-affected parameters returned to baseline levels. In contrast, neither MScanFit nor MVRC were affected apart from slightly prolonged MRRP in gastrocnemius. CONCLUSIONS: PNS do not contribute to the changes observed in muscle strength and walking capacity. SIGNIFICANCE: Further studies should include both corticospinal and peripheral mechanisms.

Assessing inter-rater reproducibility in MScanFit MUNE in a 6-subject, 12-rater "Round Robin" setup.

OBJECTIVE: To assess the inter-rater reliability of MScanFit MUNE using a "Round Robin" research design. METHODS: Twelve raters from different centres examined six healthy study participants over two days. Median, ulnar and common peroneal nerves were stimulated, and compound muscle action potential (CMAP)-scans were recorded from abductor pollicis brevis (APB), abductor digiti minimi (ADM) and anterior tibial (TA) muscles respectively. From this we calculated the Motor Unit Number Estimation (MUNE) and "A50", a motor unit size parameter. As statistical analysis we used the measures Limits of Agreement (LOA) and Coefficient of Variation (COV). Study participants scored their perception of pain from the examinations on a rating scale from 0 (no pain) to 10 (unbearable pain). RESULTS: Before this study, 41.6% of the raters had performed MScanFit less than five times. The mean MUNE-values were: 99.6 (APB), 131.4 (ADM) and 126.2 (TA), with LOA: 19.5 (APB), 29.8 (ADM) and 20.7 (TA), and COV: 13.4 (APB), 6.3 (ADM) and 5.6 (TA). MUNE-values correlated to CMAP max amplitudes (R2-values were: 0.463 (APB) (p<0.001), 0.421 (ADM) (p<0.001) and 0.645 (TA) (p<0.001)). The average perception of pain was 4. DISCUSSION: MScanFit indicates a high level of inter-rater reliability, even with only limited rater experience and is overall reasonably well tolerated by patients. These results may indicate MScanFit as a reliable MUNE method with potential as a biomarker in drug trials.

Repeater F-waves in amyotrophic lateral sclerosis: Electrophysiologic indicators of upper or lower motor neuron involvement?

OBJECTIVE: To extract insight about the mechanism of repeater F-waves (Frep) by exploring their correlation with electrophysiologic markers of upper and lower motor neuron dysfunction in amyotrophic lateral sclerosis (ALS). METHODS: The correlations of Frep parameters with clinical scores and the results of neurophysiological index (NI), MScanfit MUNE, F/M amplitude ratio (F/M%), single and paired-pulse transcranial magnetic stimulation (TMS), and triple stimulation technique (TST) studies, recorded from abductor digiti minimi (ADM) and abductor pollicis brevis (APB) muscles of 35 patients with ALS were investigated. RESULTS: Frep parameters were correlated with NI and MScanfit MUNE in ADM muscle and F/M% in both muscles. None of the Frep parameters were correlated with clinical scores or TST and TMS measures. While the CMAP amplitudes were similar in the two recording muscles, there was a more pronounced decrease of F-wave persistence in APB, probably heralding the subsequent split hand phenomenon. CONCLUSION: Our findings suggest that the presence and density of Freps are primarily related to the degree of lower motor neuron loss and show no correlation with any of the relatively extensive set of parameters for upper motor neuron dysfunction. SIGNIFICANCE: Freps are primarily related to lower motor neuron loss in ALS.

Detection of early motor involvement in diabetic polyneuropathy using a novel MUNE method - MScanFit MUNE.

OBJECTIVE: Detection of motor involvement in diabetic polyneuropathy (DPN) by nerve conduction studies (NCS) does not occur until there is substantial loss of motor units, because collateral reinnervation maintains compound muscle action potential (CMAP) amplitude. Motor unit number estimation (MUNE) methods may therefore be more sensitive. This study was undertaken to test whether the novel method, MScanFit MUNE (MScan) can detect motor involvement in DPN despite normal NCS. METHODS: Fifty-two type-2 diabetic patients and 38 healthy controls were included. The median nerve was examined in all participants using standard NCS and a detailed CMAP scan, used for MScan. Additional lower extremity NCS in patients were used for DPN diagnosis. RESULTS: Of 52 diabetic patients, 21 had NCS-defined DPN while lower extremity NCS were normal in 31 patients. MScan motor unit number and size showed higher sensitivity and incidence of abnormality than motor NCS parameters, and a similar sensitivity to sensory NCS. CONCLUSIONS: MScan is able to detect motor axonal damage at times when collateral reinnervation limits NCS changes. SIGNIFICANCE: MScan is a sensitive method to detect motor involvement in DPN, which our data suggests is present as early as sensory.

Parameters derived from compound muscle action potential scan for discriminating amyotrophic lateral sclerosis-related denervation.

INTRODUCTION: The objective of this study was to determine compound muscle action potential (CMAP) scan parameters and MScanFit motor unit number estimation (MUNE) in patients with amyotrophic lateral sclerosis (ALS) and to compare the results in the abductor pollicis brevis (APB) to those in the abductor digiti minimi (ADM). METHODS: CMAP scans were recorded from the APB and ADM in 35 patients with ALS and 21 controls. MScanFit MUNE, neurophysiological index (NI), step%, returner%, and D50 were calculated. RESULTS: CMAP scan parameters including the returner%, MScanFit MUNE, and NI can distinguish ALS with high sensitivity and specificity. The electrophysiological parameters, with the exception of D50 (the number of largest consecutive differences of recorded responses generating 50% of maximum CMAP), showed more pronounced changes in the APB than in the ADM, even though most of the patients had normal APB/ADM amplitude ratios. DISCUSSION: CMAP scan parameters and MScanFit MUNE can be used in the evaluation of denervation and reinnervation and may herald the "split hand" in ALS.