Estimating motor unit numbers from a CMAP scan: Repeatability study on three muscles at 15 centres.

OBJECTIVE: To assess the repeatability and suitability for multicentre studies of MScanFit motor unit number estimation (MUNE), which involves modelling compound muscle action potential (CMAP) scans. METHODS: Fifteen groups in 9 countries recorded CMAP scans twice, 1-2 weeks apart in healthy subjects from abductor pollicis brevis (APB), abductor digiti minimi (ADM) and tibialis anterior (TA) muscles. The original MScanFit program (MScanFit-1) was compared with a revised version (MScanFit-2), designed to accommodate different muscles and recording conditions by setting the minimal motor unit size as a function of maximum CMAP. RESULTS: Complete sets of 6 recordings were obtained from 148 subjects. CMAP amplitudes differed significantly between centres for all muscles, and the same was true for MScanFit-1 MUNE. With MScanFit-2, MUNE differed less between centres but remained significantly different for APB. Coefficients of variation between repeats were 18.0% for ADM, 16.8% for APB, and 12.1% for TA. CONCLUSIONS: It is recommended for multicentre studies to use MScanFit-2 for analysis. TA provided the least variable MUNE values between subjects and the most repeatable within subjects. SIGNIFICANCE: MScanFit was primarily devised to model the discontinuities in CMAP scans in patients and is less suitable for healthy subjects with smooth scans.

Muscle velocity recovery cycles in myopathy.

OBJECTIVE: To understand the pathophysiology of myopathies by using muscle velocity recovery cycles (MVRC) and frequency ramp (RAMP) methodologies. METHODS: 42 patients with quantitative electromyography (qEMG) and biopsy or genetic verified myopathy and 42 healthy controls were examined with qEMG, MVRC and RAMP, all recorded from the anterior tibial muscle. RESULTS: There were significant differences in the motor unit potential (MUP) duration, the early and late supernormalities of the MVRC and the RAMP latencies in myopathy patients compared to controls (p < 0.05 apart from muscle relatively refractory period (MRRP)). When dividing into subgroups, the above-mentioned changes in MVRC and RAMP parameters were increased for the patients with non-inflammatory myopathy, while there were no significant changes in the group of patients with inflammatory myopathy. CONCLUSIONS: The MVRC and RAMP parameters can discriminate between healthy controls and myopathy patients, more significantly for non-inflammatory myopathy. MVRC differences with normal MRRP in myopathy differs from other conditions with membrane depolarisation. SIGNIFICANCE: MVCR and RAMP may have a potential in understanding disease pathophysiology in myopathies. The pathogenesis in non-inflammatory myopathy does not seem to be caused by a depolarisation of the resting membrane potential but rather by the change in sodium channels of the muscle membrane.

Detecting peripheral motor nervous system involvement in chronic spinal cord injury using two novel methods: MScanFit MUNE and muscle velocity recovery cycles.

OBJECTIVE: To examine the peripheral nervous system (PNS) in spinal cord injured (SCI) patients using two novel methods: (1) MScanFit MUNE; a motor unit number estimation method detecting motor unit loss and (2) muscle velocity recovery cycles (MVRCs) measuring muscle membrane properties which has previously shown depolarization of the muscle membrane in denervated muscles. METHODS: Thirty chronic SCI patients (lesion above Th10) and twenty-five gender -and age matched healthy controls (HC) were examined. MScanFit was recorded from peroneal nerve to anterior tibial muscle (TA) and tibial nerve to abductor hallucis muscle after excluding localized mononeuropathies. MVRCs were recorded from TA. RESULTS: Nerve conduction studies showed mononeuropathy in 8 patients (27%) (sciatic (2), -or peroneal nerve (6)). SCI patients had in average reduced motor unit number compared with HC and prolonged muscle refractory period and reduced supernormality. SIGNIFICANCE: A high prevalence of nerve lesion and a diffuse affection of the PNS following SCI are highly relevant findings that should be accounted for when planning neurorehabilitation for persons living with SCI.

Evidence-based recommendations for examination and diagnostic strategies of polyneuropathy electrodiagnosis.

The purpose of this report is to recommend evidence-based strategies for polyneuropathy (PNP) electrodiagnosis based on a large cohort of patients examined prospectively. Nerve conduction studies (NCS) of bilateral tibial, peroneal and sural nerves, the latter with both near-nerve-technique (NNT) and surface recordings, were done in 313 patients with clinically suspected PNP. Bilateral dorsal sural and medial plantar nerves, and unilateral median and ulnar nerves were further examined in a subgroup of patients. The final clinical diagnosis retrieved from the patients medical records 1-6 years after the neurophysiological investigation served as diagnostic reference standard. The clinical follow-up diagnosis confirmed PNP in 219 patients. The tibial nerve was the most sensitive nerve (75%), with prolonged tibial F-wave as the most sensitive parameter (72%). Sural NNT recordings were more sensitive (66%) than surface recordings (49%) (p < 0.05), however, dorsal sural (68%) and medial planter (70%) nerves had similar sensitivities as NNT. There was no side difference in the incidence of abnormality for any nerve. Based on these results, we recommend a strategy starting with tibial and sural NCS on one side for electrophysiological screening for distal symmetric PNP. If one of these is abnormal, we recommend examining the other lower and upper extremity nerves, including distal sensory nerves, particularly if NNT is not applicable. While one abnormal parameter is sufficient to interpret a nerve as abnormal, we recommend at least two abnormal nerves for PNP diagnosis, preferentially one being the sural nerve. We believe that the strategies recommended in this study may improve PNP electrodiagnosis.

Muscle velocity recovery cycles in neurogenic muscles.

OBJECTIVE: To examine muscle membrane properties in neurogenic muscles using Muscle Velocity Recovery Cycles (MVRCs). METHODS: Forty-seven patients referred to Nerve Conduction Studies (NCS) and Electromyography (EMG) for peroneal nerve entrapment neuropathy were prospectively included. The patients were categorized as peroneal nerve entrapment neuropathy across knee (n = 22), L5-radiculapathy (n = 10), normal NCS/EMG (n = 9) and other disorders (n = 6) using NCS/EMG and neuroimaging results. Strength in anterior tibial muscle was measured by Medical Council Scale (MRC) and disease duration was recorded. In addition to conventional NCS/EMG, all subjects were examined with MVRCs in anterior tibial muscle. This provided parameters of muscle relative refractory period (MRRP) and early supernormality (ESN) and late supernormality (LSN). The results were compared with 29 age-matched healthy control subjects. RESULTS: MRRP was prolonged and ESN and LSN were reduced in neurogenic muscles. MRRP, ESN and LSN correlated to MRC and incidence of spontaneous activity but not to motor unit potential parameters or disease duration. CONCLUSIONS: MVRC changes provide in vivo evidence of depolarization in intact human muscle fibres that could underlie reduced muscle excitability and hence weakness in neurogenic muscles. SIGNIFICANCE: MVRCs appear to be a useful technique for revealing disease mechanism in a broad range of neuromuscular diseases.

MScanFit motor unit number estimation (MScan) and muscle velocity recovery cycle recordings in amyotrophic lateral sclerosis patients.

OBJECTIVE: Motor Unit Number Estimation (MUNE) methods, such as the recently developed MScanFit MUNE (MScan), may be valuable in tracking motor unit loss in ALS. Muscle Velocity Recovery Cycles (MVRCs) provide information about muscle membrane properties and can reveal disease-related changes. This study was undertaken to test the applicability of MScan to the anterior tibial muscle (TA) and to test whether the MVRCs could improve understanding of ALS pathophysiology. METHODS: Twenty-six ALS patients and 25 healthy controls were evaluated by quantitative electromyography, nerve conduction study and the two novel methods: MScan and MVRC; all in the TA and peroneal nerve. RESULTS: The estimated number of motor units for ALS patients (Median: 45, interquartile range: 28.5-76.5) was significantly lower than for the controls (117, 96.0-121.0) (P = 2.19 × 10-7). Unit size was increased only when amplitudes were expressed as percentage of CMAP. Of MVRC measurements, only relative refractory period was significantly abnormal in patients. CONCLUSION: MScanFit MUNE gives a sensitive and quantitative measure of loss of TA motor units in ALS. Muscle fiber membrane properties are mostly unaffected, despite substantial denervation, presumably due to collateral reinnervation. SIGNIFICANCE: MScan is suitable for detecting motor unit loss in TA. MVRCs do not provide new insights in ALS.

Diagnostic criteria for amyotrophic lateral sclerosis: A multicentre study of inter-rater variation and sensitivity.

OBJECTIVE: This study assesses inter-rater agreement and sensitivity of diagnostic criteria for amyotrophic lateral sclerosis (ALS). METHODS: Clinical and electrophysiological data of 399 patients with suspected ALS were collected by eleven experienced physicians from ten different countries. Eight physicians classified patients independently and blinded according to the revised El Escorial Criteria (rEEC) and to the Awaji Criteria (AC). Inter-rater agreement was assessed by Kappa coefficients, sensitivity by majority diagnosis on 350 patients with follow-up data. RESULTS: Inter-rater agreement was generally low both for rEEC and AC. Agreement was best on the categories "Not-ALS", "Definite", and "Probable", and poorest for "Possible" and "Probable Laboratory-supported". Sensitivity was equal for rEEC (64%) and AC (63%), probably due to downgrading of "Probable Laboratory-supported" patients by AC. However, AC was significantly more effective in classifying patients as "ALS" versus "Not-ALS" (p < 0.0001). CONCLUSIONS: Inter-rater variation is high both for rEEC and for AC probably due to a high complexity of the rEEC inherent in the AC. The gain of AC on diagnostic sensitivity is reduced by the omission of the "Probable Laboratory-supported" category. SIGNIFICANCE: The results highlight a need for initiatives to develop simpler and more reproducible diagnostic criteria for ALS in clinical practice and research.

Somatosensory function is impaired in patients with idiopathic REM sleep behaviour disorder.

BACKGROUND: Idiopathic REM sleep behaviour disorder (iRBD) has been recognised as a significant biomarker for developing a neurodegenerative alpha-synucleinopathy, which is why iRBD is considered to be a prodromal state for alpha-synucleinopathies including Parkinson's disease (PD). Many patients with PD suffer from complaints of pain and present impaired somatosensory function. We hypothesized that pain perception and somatosensory function could be altered already in a preclinical stage of PD including iRBD. Hence, the objective of this study was to investigate pain perception and somatosensory function in patients with iRBD. METHODS: Quantitative sensory testing (QST), laser evoked potentials (LEPs), and conditioned pain modulation (CPM) testing were performed in 13 iRBD patients without any clinical signs of PD or narcolepsy (11 males, 2 females, mean age 65.2 years) and 15 gender- and age-matched healthy control subjects (12 males, 3 females, mean age 65.8 years). RESULTS: Thermal detection thresholds were higher in the iRBD group compared with the control group (cold detection threshold (CDT) p = 0.020, thermal sensory limen (TSL) p = 0.001), indicating an impaired temperature sensation in iRBD patients. The N2/P2 LEPs amplitude was smaller in iRBD patients than controls, but not statistically significant (p = 0.053). CONCLUSIONS: This study found an impaired somatosensory function in iRBD patients, suggesting that somatosensory impairment might be an early feature in the neurodegenerative process of PD.

The utility of motor unit number estimation methods versus quantitative motor unit potential analysis in diagnosis of ALS.

OBJECTIVE: To compare the diagnostic utility of motor unit number estimation (MUNE) methods to motor unit potential (MUP) analysis in amyotrophic lateral sclerosis (ALS). METHODS: Twenty-five patients (1 definite, 11 probable, 9 possible ALS and 4 progressive muscular atrophy) and 22 healthy controls were prospectively included. Quantitative MUP analysis and three MUNE methods; Multiple Point Stimulation MUNE (MPS), Motor Unit Number Index (MUNIX) and MScanFit MUNE (MScan) were done in abductor pollicis brevis muscle. The sensitivities were compared by McNemar chi-square test. MUNE, MUP and revised ALS Functional Rating Scale (ALSFRS-R) parameters were correlated by regression analysis. RESULTS: The sensitivities of MPS (76%) and MScan (68%) were higher than MUP duration (36%) and amplitude (40%) in detecting motor unit loss (p < 0.05). MUNE methods increased the categorical probability from possible to probable ALS in 4 patients (16%). There was only significant correlation between ALSFRS-R and MScan (r = 0.443, p = 0.027) among the electrophysiological tests. MUNE methods did not correlate to MUP parameters. CONCLUSIONS: MUNE methods are more sensitive in showing abnormality than MUP analysis. SIGNIFICANCE: MUNE methods, in particular MScan, may have the potential to be implemented in the clinical practice for diagnosis and follow-up of neuromuscular disorders particularly ALS.

Fasciculations in nerve and muscle disorders - A prospective study of muscle ultrasound compared to electromyography.

OBJECTIVES: We examined the clinical utility of muscle ultrasound (MUS) in detecting fasciculations in patients with nerve and muscle disorders (NMD) and investigated the impact on diagnostic sensitivity when combining electromyography (EMG) and MUS. METHODS: We included 58 consecutive patients suspected to have NMD and 38 healthy subjects (HS). Patients and HS underwent MUS in 14 skeletal and two bulbar muscles and the video recordings of the MUS were anonymised. Only patients underwent EMG. RESULTS: The follow-up diagnoses were: 15 Amyotrophic lateral sclerosis (ALS), 15 polyneuropathy, 14 patients had other diagnoses (disease-control group) and 14 patients had no pathological findings. MUS detected more muscles with fasciculations among ALS patients compared to all other groups. In ALS patients, the dominating pattern of fasciculations was continuous (45%). More proximal muscles showed fasciculations among ALS patients compared to all other patient groups. MUS was more sensitive than EMG in detecting fasciculations (58% vs. 48%). When combining the two methods, the sensitivity in detecting fasciculations increased to 65%. Fasciculations in nine muscles could predict the ALS diagnosis with high sensitivity and specificity. CONCLUSIONS: MUS is a sensitive tool in detecting fasciculations in patients with NMD and performs well compared to EMG in diagnosing ALS. SIGNIFICANCE: MUS may add valuable information in the clinic, especially in diagnosing ALS.

Modified automatic R-peak detection algorithm for patients with epilepsy using a portable electrocardiogram recorder.

Earlier studies have shown that short term heart rate variability (HRV) analysis of ECG seems promising for detection of epileptic seizures. A precise and accurate automatic R-peak detection algorithm is a necessity in a real-time, continuous measurement of HRV, in a portable ECG device. We used the portable CE marked ePatch® heart monitor to record the ECG of 14 patients, who were enrolled in the videoEEG long term monitoring unit for clinical workup of epilepsy. Recordings of the first 7 patients were used as training set of data for the R-peak detection algorithm and the recordings of the last 7 patients (467.6 recording hours) were used to test the performance of the algorithm. We aimed to modify an existing QRS-detection algorithm to a more precise R-peak detection algorithm to avoid the possible jitter Qand S-peaks can create in the tachogram, which causes error in short-term HRVanalysis. The proposed R-peak detection algorithm showed a high sensitivity (Se = 99.979%) and positive predictive value (P+ = 99.976%), which was comparable with a previously published QRS-detection algorithm for the ePatch® ECG device, when testing the same dataset. The novel R-peak detection algorithm designed to avoid jitter has very high sensitivity and specificity and thus is a suitable tool for a robust, fast, real-time HRV-analysis in patients with epilepsy, creating the possibility for real-time seizure detection for these patients.

Neurophysiological localisation of ulnar neuropathy at the elbow: Validation of diagnostic criteria developed by a taskforce of the Danish Society of clinical neurophysiology.

OBJECTIVE: This study validates consensus criteria for localisation of ulnar neuropathy at elbow (UNE) developed by a taskforce of the Danish Society of Clinical Neurophysiology and compares them to the existing criteria from the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM). The Danish criteria are based on combinations of conduction slowing in the segments of the elbow and forearm expressed in Z-scores, and difference between the segments in m/s. Examining fibres to several muscles and sensory fibres can increase the certainty of the localisation. METHODS: Diagnostic accuracy for UNE was evaluated on 181 neurophysiological studies of the ulnar nerve from 171 peer-reviewed patients from a mixed patient-group. The diagnostic reference standard was the consensus diagnosis based on all available clinical, laboratory, and electrodiagnostic information reached by a group of experienced Danish neurophysiologists. RESULTS: The Danish criteria had high specificity (98.4%) and positive predictive value (PPV) (95.2%) and fair sensitivity (76.9%). Compared to the AANEM criteria, the Danish criteria had higher specificity (p<0.001) and lower sensitivity (p=0.02). CONCLUSIONS: The Danish consensus criteria for UNE are very specific and have high PPV. SIGNIFICANCE: The Danish criteria for UNE are reliable and well suited for use in different centres as they are based on Z-scores.

Reproducibility, and sensitivity to motor unit loss in amyotrophic lateral sclerosis, of a novel MUNE method: MScanFit MUNE.

OBJECTIVE: To examine inter- and intra-rater reproducibility and sensitivity to motor unit loss of a novel motor unit number estimation (MUNE) method, MScanFit MUNE (MScan), compared to two traditional MUNE methods; Multiple point stimulation MUNE (MPS) and Motor Unit Number Index (MUNIX). METHODS: Twenty-two ALS patients and 20 sex- and age-matched healthy controls were included. MPS, MUNIX, and MScan were performed twice each by two blinded physicians. Reproducibility of MUNE values was assessed by coefficient of variation (CV) and intra class correlation coefficient (ICC). Ability to detect motor unit loss was assessed by ROC curves and area under the curve (AUC). The times taken for each of the methods were recorded. RESULTS: MScan was more reproducible than MPS and MUNIX both between and within operators. The mean CV for MScan (12.3%) was significantly lower than for MPS (24.7%) or MUNIX (21.5%). All methods had ICC>0.94. MScan and Munix were significantly quicker to perform than MPS (6.3mvs. 13.2m). MScan (AUC=0.930) and MPS (AUC=0.899) were significantly better at discriminating between patients and healthy controls than MUNIX (AUC=0.831). CONCLUSIONS: MScan was more consistent than MPS or MUNIX and better at distinguishing ALS patients from healthy subjects. SIGNIFICANCE: MScan may improve detection and assessment of motor unit loss.

Added value of electromyography in the diagnosis of myopathy: A consensus exercise.

OBJECTIVE: Currently, neurologists may primarily rely on blood biomarkers, muscle biopsy, MRI, and genetics in the diagnostic work-up of suspected myopathy. Using expert consensus as diagnostic reference standard, this study addressed the added value of electrodiagnostic medicine (EDX) in diagnosis of myopathies. METHODS: One hundred ninety-four EDX evaluations of patients with a peer-review consensus diagnosis of myopathy were collected by seven European centres. Each patient was given three different consensus diagnoses: (1) the EDX diagnosis solely based on EDX results, (2) the pure clinical diagnosis based on all available information except EDX results, and (3) the final diagnosis including EDX and all additional information. The myopathies were grouped as muscular dystrophy (45), inflammatory myopathy (46), other aetiology (36) or unknown aetiology (67). RESULTS: Higher diagnostic probabilities for myopathy were seen in the final diagnosis compared to the pure clinical diagnosis (p<0.001). Adding EDX information increased the diagnostic probability of myopathy in 67 patients (34.4%). The greatest increase was seen for myopathies of unknown aetiology. CONCLUSIONS: EDX has a major impact in the diagnosis of myopathies of unknown aetiology. In genetically or biopsy proven myopathies, EDX generally supports the diagnosis. SIGNIFICANCE: EDX is still a useful tool in the diagnostic work-up of most patients with suspected myopathy.

The electrophysiological response to immunoglobulin therapy in chronic inflammatory demyelinating polyneuropathy.

OBJECTIVE: To characterize changes in motor nerve conduction studies (MNCS) and motor unit number index (MUNIX) following treatment with subcutaneous immunoglobulin and to assess whether these changes are related to muscle strength. METHODS: Data from 23 patients participating in a randomized, controlled trial were analyzed. MNCS and MUNIX were performed before and after 12 weeks of treatment. Isokinetic strength (IMS) was measured in various muscles together with grip strength (GS). RESULTS: Proximally evoked compound muscle action potential (CMAP) amplitudes and MUNIX tended to be better preserved in treated patients (P=.049 and .045). Changes in other parameters did not differ between groups. There was no correlation between changes in electrophysiological parameters and IMS. Changes in GS were related to median nerve motor conduction velocity, distal motor latency, CMAP amplitudes, and distally evoked CMAP duration (P=.013-.035). CONCLUSION: Proximally evoked CMAP amplitudes appear to be the best MNCS parameter to assess treatment outcome in chronic inflammatory demyelinating polyneuropathy.

Pelvic floor electrophysiology in spinal cord injury.

OBJECTIVE: The study aimed to investigate sacral peripheral nerve function and continuity of pudendal nerve in patients with chronic spinal cord injury (SCI) using pelvic floor electrophysiological tests. METHODS: Twelve patients with low cervical or thoracic SCI were prospectively included. Quantitative external anal sphincter (EAS) muscle electromyography (EMG), pudendal nerve terminal motor latency (PNTML) testing, bulbocavernosus reflex (BCR) testing and pudendal short-latency somatosensory-evoked potential (SEP) measurement were performed. RESULTS: In EAS muscle EMG, two patients had abnormal increased spontaneous activity and seven prolonged motor unit potential duration. PNTML was normal in 10 patients. BCR was present with normal latency in 11 patients and with prolonged latency in one. The second component of BCR could be recorded in four patients. SEPs showed absent cortical responses in 11 patients and normal latency in one. CONCLUSIONS: Pudendal nerve and sacral lower motor neuron involvement are significantly associated with chronic SCI, most prominently in EAS muscle EMG. The frequent finding of normal PNTML latencies supports earlier concerns on the utility of this test; however, BCR and pudendal SEPs may have clinical relevance. SIGNIFICANCE: As intact peripheral nerves including pudendal nerve are essential for efficient supportive therapies, pelvic floor electrophysiological testing prior to these interventions is highly recommended.

The artificial somato-autonomic reflex arch does not improve bowel function in subjects with spinal cord injury.

STUDY DESIGN: Prospective cohort study. OBJECTIVE: Although introduced for neurogenic bladder dysfunction, it has been suggested that the artificial somato-autonomic reflex arch alleviates neurogenic bowel dysfunction (NBD). We aimed at evaluating the effects of the reflex arch on NBD. SETTING: Denmark. METHODS: Ten subjects with supraconal spinal cord injury (SCI) (nine males, median age 46 years) had an anastomosis created between the ventral part of the fifth lumbar or first sacral nerve root and the ventral part of the second sacral nerve root. Standardized assessment of segmental colorectal transit times with radiopaque markers, evaluation of scintigraphic assessed colorectal emptying upon defecation, scintigraphic assessment of colorectal transport during stimulation of the reflex arch, standard anorectal physiology tests and colorectal symptoms were performed at baseline and 18 months after surgery. RESULTS: No significant change was observed in colorectal emptying upon defecation (median 31% of the rectosigmoid at baseline vs 75% at follow-up, P=0.50), no movement of colorectal contents was observed during stimulation of the reflex arch. Segmental colorectal transit times, anal sphincter pressures and rectal capacity did not change, and no change was seen in NBD score (median 13.5 (baseline) vs 12.5 (follow-up), P=0.51), St Marks fecal incontinence score (4.5 vs 5.0, P=0.36) and Cleveland constipation score (6.0 vs 8.0, P=0.75). CONCLUSIONS: The artificial somato-autonomic reflex arch has no effect on bowel function in subjects with supraconal SCI.

Modulation of the muscle and nerve compound muscle action potential by evoked pain.

Background and aims To our knowledge there are no studies that have examined the effects of the experimental pain on muscle fibre excitability as measured by the amplitudes of the potentials evoked by direct muscle stimulation (DMS) in a muscle at rest. We hypothesized that evoked pain can modulate the muscle compound action potential (CMAP) obtained by DMS possibly due to changes in muscle fibre excitability. Methods Pain was evoked by intramuscular infusion of hypertonic saline in 50 men. Ten control subjects were infused with isotonic saline. The infusions were given distal to the motor end plate region of the dominant brachial biceps muscle (BBM) in a double-blind manner. The nerve CMAP was obtained by stimulating the musculocutaneous nerve and recording from the BBM using surface-electrodes. Muscle CMAPs were obtained by direct muscle stimulation with subdermal electrodes placed subcutaneously in the distal third of the muscle. A stimuli-response curve of the amplitudes from muscle CMAP was obtained by stimulating from 10 to 90 mA. Results There was a decrease of the nerve CMAP amplitudes after infusion of isotonic saline (from 13.78mV to 12.16 mV), p-value 0.0007 and of hypertonic saline (from 13.35 mV to 10.85 mV), p-value 0.0000. The percent decrease from before to after infusion was larger in the hypertonic saline group (19.37%) compared to the isotonic saline group (12.18%), p-value 0.025. There was a decrease of the amplitudes of the muscle CMAP after infusion of both isotonic (at 90 mA from 13.84mV to 10.32 mV, p value 0.001) and of hypertonic saline (at 90 mA from 14.01 mV to 8.19 mV, p value 0.000). The percent decrease was larger in the hypertonic saline group compared to the isotonic saline group for all the stimulations intensities. At 90 mA we saw a 42% decrease in the hypertonic saline group and 24.5% in the isotonic saline group, p value 0.005. There were no changes in conduction velocity. Conclusion We found a larger amplitude decrease of the muscle and nerve potentials following hypertonic saline infusion compared with that of isotonic saline. We suggest that this deferential outcome of hypertonic saline on muscle CMAP may be linked to the nociceptive effect on muscle fibre membrane excitability. Implications The study supplies with some evidence of the peripheral effect of muscle pain. However, further trials with other nociceptive substances such as capsaicin should be performed.

Effects of PTH(1-84) therapy on muscle function and quality of life in hypoparathyroidism: results from a randomized controlled trial.

UNLABELLED: The effects of treatment with 100 µg parathyroid hormone (PTH) (1-84) or an identical placebo on muscle function and quality of life (QoL) was studied in hypoparathyroid patients. At baseline, we found reduced QoL but no myopathy in the patients. Six months of treatment did not improve QoL, and muscle strength decreased slightly. INTRODUCTION: A reduced quality of life (QoL) and myopathy that may be due to the absence of PTH have been reported in patients with hypoparathyroidism (hypoPT). METHODS: Sixty-two patients with chronic hypoPT were randomized to 6 months of treatment with either PTH(1-84) 100 µg/d s.c. or placebo, given as add-on therapy to conventional treatment. Muscle function and postural stability were investigated using a dynamometer chair, a stadiometer platform, the repeated chair stands test, the timed up and go test, and electromyography. QoL was assessed using the 36-item Short Form Health Survey and the WHO-5 Well-Being Index. RESULTS: The mean age of the patients was 52 ± 11 years, and 85 % were females. At baseline, QoL was significantly reduced in comparison with norm-based scores. Compared with placebo, PTH did not improve QoL or muscle function. Rather, max force production decreased significantly by 30 % at elbow flexion in the PTH group compared with the placebo group. Moreover, there was a nonsignificant trend for muscle strength to decrease in the upper extremities and on knee extension in response to PTH. Treatment did not affect postural stability. Electromyography showed a slight decrease in the duration of motor unit potentials in the PTH group, indicating a tendency toward myopathy, which, however was not symptomatic. CONCLUSIONS: Overall, our data do not support an immediate beneficial effect of PTH replacement therapy on muscle function or QoL. A high frequency of hypercalcemia among our patients may have compromised the potential beneficial effects of reversing the state of PTH insufficiency.

Effect of training on corticomotor excitability in clinical neck pain.

BACKGROUND: Corticomotor excitability has been shown to correlate with motor learning and functional recovery. The aim of the present study was to monitor changes in excitability of the corticomotor pathways induced by neck training and to compare the effects in patients with neck or knee pain and pain-free participants. METHODS: Corticomotor excitability was assessed using transcranial magnetic stimulation and electromyography at baseline, after 30 min and 1 h, and at a 1-week follow-up visit. The primary outcome measures were changes in amplitudes and latencies of motor evoked potentials (MEPs) at 1-week follow-up. RESULTS: MEP responses induced by neck training yielded significantly different outcomes in the three groups. In the group with neck pain and training, MEP amplitudes were significantly reduced between baseline and 30 min (p ≤ 0.05), but with no significant difference between baseline, 1 h (p = 0.178) and 1 week (p = 0.067). In the group with knee pain and training, MEP amplitudes significantly increased between baseline and 30 min (p ≤ 0.01) and 1 h (p < 0.001), but not after 1 week (p = 0.524) compared with baseline. In the pain-free group, there were no changes over time. CONCLUSION: Neck training reduced neuroplastic responsiveness of corticomotor pathways in neck pain patients in contrast to knee pain patients and pain-free participants. Increased attention to adaptive and maladaptive neuroplastic responses induced by training may prove valuable in the process of optimizing clinical outcomes.