Motor Nerve Conduction Block Estimation in Demyelinating Neuropathies by Deconvolution

A deconvolution method is proposed for conduction block (CB) estimation based on two compound muscle action potentials (CMAPs) elicited by stimulating a nerve proximal and distal to the region in which the block is suspected. It estimates the time delay distributions by CMAPs deconvolution, from which CB is computed. The slow afterwave (SAW) is included to describe the motor unit potential, as it gives an important contribution in case of the large temporal dispersion (TD) often found in patients. The method is tested on experimental signals obtained from both healthy subjects and pathological patients, with either Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) or Multifocal Motor Neuropathy (MMN). The new technique outperforms the clinical methods (based on amplitude and area of CMAPs) and a previous state-of-the-art deconvolution approach. It compensates phase cancellations, allowing to discriminate among CB and TD: estimated by the methods of amplitude, area and deconvolution, CB showed a correlation with TD equal to 39.3%, 29.5% and 8.2%, respectively. Moreover, a significant decrease of percentage reconstruction errors of the CMAPs with respect to the previous deconvolution approach is obtained (from a mean/median of 19.1%/16.7% to 11.7%/11.2%). Therefore, the new method is able to discriminate between CB and TD (overcoming the important limitation of clinical approaches) and can approximate patients’ CMAPs better than the previous deconvolution algorithm. Then, it appears to be promising for the diagnosis of demyelinating polyneuropathies, to be further tested in the future in a prospective clinical trial.

Diaphragmatic Compound Muscle Action Potentials Recorded From Over the Sternum and Lateral Chest Wall: a Comparative Study

Objectives:To report normative data for diaphragmatic compound muscle action potentials (DCMAPs) recorded from over the sternum and lateral chest wall (LCW).Method:The phrenic nerve of seventy-three healthy subjects was bilaterally stimulated at the posterior border of the sternocleidomastoid muscle. DCMAPs from over the sternum and LCW were recorded (inspiration/expiration). Results: Normative values of sternal and LCW DCMAPs were presented. Significant differences were found between sternal and LCW potentials in the mean latency, amplitude, and area (p<0.001). The duration did not differ between the two sites. Differences were found between inspiration and expiration, right and left sides, and men and women. Regression analysis showed a relation between latency of sternal and LCW potentials and age. Latency (LCW potentials) and amplitude and area (sternal/LCW potentials) were related to gender. Amplitude (LCW potentials/inspiration) and area (sternal potentials/inspiration) were related to chest circumference (p=0.023 and 0.013 respectively). Area (sternal potentials/expiration) was related to the BMI (p=0.019). Conclusions: Our normative values for sternal and LCW DCMAPs are provided. Notable differences in the DCMAPs parameters were detected between the two recording sites, inspiration and expiration, right and left, and men and women. Significance:The technique of phrenic nerve should be standardized.

Effects of muscle shortening on single-fiber, motor unit, and compound muscle action potentials

Even under isometric conditions, muscle contractions are associated with some degree of fiber shortening. The effects of muscle shortening on extracellular electromyographic potentials have not been characterized in detail. Moreover, the anatomical, biophysical, and detection factors influencing the muscle-shortening effects have been neither identified nor understood completely. Herein, we investigated the effects of muscle shortening on the amplitude and duration characteristics of single-fiber, motor unit, and compound muscle action potentials. We found that, at the single-fiber level, two main factors influenced the muscle-shortening effects: (1) the electrode position and distance relative to the myotendinous zone and (2) the electrode distance to the maxima of the dipole field arising from the stationary dipole created at the fiber-tendon junction. Besides, at the motor unit and muscle level, two additional factors were involved: (3) the overlapping between the propagating component of some fibers with the non-propagating component of other fibers and (4) the spatial spreading of the fiber-tendon junctions. The muscle-shortening effects depend critically on the electrode longitudinal distance to the myotendinous zone. When the electrode was placed far from the myotendinous zone, muscle shortening resulted in an enlargement and narrowing of the final (negative) phase of the potential, and this enlargement became less pronounced as the electrode approached the fiber endings. For electrode locations close to the myotendinous zone, muscle shortening caused a depression of both the main (positive) and final (negative) phases of the potential. Beyond the myotendinous zone, muscle shortening led to a decrease of the final (positive) phase. The present results provide reference information that will help to identify changes in MUPs and M waves due to muscle shortening, and thus to differentiate these changes from those caused by muscle fatigue. Graphical abstract

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

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

Comparison of The Electrophysiological Characteristics of Tight Filum Terminale And Tethered Cord Syndrome

This study aims to characterize tight filum terminale (TFT) in motor evoked potential (MEP) testing by comparing TFT patients with both tether cord syndrome (TCS) patients and healthy subjects. Fifty TFT patients, 18 TCS patients, and 35 healthy volunteers participated in this study. We recorded MEPs following transcranial magnetic stimulation from the bilateral abductor hallucis muscles as well as compound muscle action potentials and F-waves evoked by electrical stimulation of the tibial nerve from the bilateral abductor pollicis brevis muscles. The peripheral conduction time (PCT) was calculated from the latency of the compound action potential and F-wave. Furthermore, the central motor conduction time (CMCT) was calculated by subtracting PCT from MEP latency. TFT and TCS patients had a significantly longer MEP latency than healthy subjects. PCT in TFT patients were significantly longer than those in TCS patients or healthy subjects. Using the cut-off values for PCT, we were able to diagnose patients with TFT patients with a sensitivity of 72.0% and a specificity of 91.4%. Prolonged PCT in the MEP test may be a useful indicator for TFT and suggests that MEP may be used as an adjunct diagnostic tool for TFT.

Ultrasound-guided five-point injection of botulinum toxin for patients with trapezius hypertrophy

Objectives Our study aimed to explore the clinical therapeutic effects of ultrasound-guided five-point injection of botulinum toxin type A for patients with trapezius hypertrophy. Methods Twenty female patients diagnosed with trapezius hypertrophy were enrolled in this study. The thicknesses of the trapezius muscle were measured by using the ultrasound scanner to locate the thickest point of trapezius, followed by labelling the other four points around the first point. Botulinum toxin type A was injected bilaterally (50 IU/side, 5 points/side) in the trapezius muscle of these patients. The surgery effects were evaluated by thicknesses of the trapezius muscle, intramuscular needle electromyographic and electroneurographic examinations, appearance changes and patients’ satisfactions. Results Statistically significant differences in thicknesses of the trapezius muscle were observed at 4 weeks (p < 0.001), 12 weeks (p < 0.001), 20 weeks (p < 0.001), 28 weeks (p = 0.011), 36 weeks (p = 0.022), and 44 weeks (p = 0.032) after surgery. The latencies of trapezius muscle became longer at 12 weeks after surgery (left: 2.40 ms, right: 2.53 ms vs. left: 1.75 ms, right: 2.00 ms). Electroneurographic results showed amplitude reduction of compound muscle action potentials (CMAPs) at 12 weeks after surgery (left: 1.91 uV, right: 3.10 uV vs. left: 15.00 uV, right: 15.40 uV). Obvious appearance changes were revealed at 12 weeks after surgery. All of 80% patients were very satisfied, 15% patients were relatively satisfied, and 5% patients were not satisfied with the surgery. Conclusion Ultrasound-guided five-point injection of botulinum toxin type A might be effective for patients with trapezius hypertrophy.

Clinical Features of Familial Amyloidotic Polyneuropathy With Transthyretin p.Ala117Ser Mutation in Mainland China

Objective: Our study aimed to report the clinical features of ATTR-PN with TTR p.Ala117Ser mutation in mainland China. Methods: Thirteen patients from 13 different families diagnosed with p.Ala117Ser ATTR-PN were identified from three centres. Clinical and laboratory data were retrospectively retrieved for analysis. Results: The male/female ratio was 11:2. All patients showed late onset, with the age of onset at 57.8 ± 5.8 years. The initial symptom was numbness of the lower or upper extremities in 9 patients (69.2%). Paraesthesia was present in all patients. Eleven patients (84.6%) had autonomic dysfunction. Cardiac, renal, hepatic, and ocular dysfunctions were noted in 8 (61.5%), 1 (7.7%), 2 (15.4%), and 3 (23.1%) patients, respectively. Nerve conduction studies have shown axonal-type sensorimotor polyneuropathy. The decline in sensory nerve action potentials was more noticeable than in compound muscle action potentials. The nerve damage present in the lower limbs was more severe than that in the upper limbs. Nerve biopsy revealed positive Congo red staining in 7/10 patients (70%). Conclusion: Our study is the largest population report on this rare p.Ala117Ser mutation in mainland China.

3,4-diaminopyridine treatment for Lambert-Eaton myasthenic syndrome in adults: a meta-analysis of randomized controlled trials

Background Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder of neuromuscular transmission. The objective was to examine the efficacy and safety of 3,4-diaminopyridine (3,4-DAP) in patients with LEMS. Methods We searched several databases to identify relevant studies, including PubMed, EMBASE, Web of Science, MEDLINE, Cochrane Neuromuscular Disease Group Specialized Register and the Cochrane Central Register of Controlled Trials(CENTRAL). The primary outcome, quantitative myasthenia gravis (QMG) score and the secondary outcome, compound muscle action potentials (CMAP) amplitude were pooled by meta-analysis. Results Six randomised controlled trials (RCTs) involving 115 patients with LEMS were included. QMG score showed a significant decrease (improvement) of 2.76 points (95 % CI, -4.08 to -1.45, p < 0.001) after treatment with 3, 4-DAP. Moreover, the overall mean CMAP amplitude improved significantly in LEMS patients with 3, 4-DAP treatment, compared with placebo treatment (mean difference 1.34 mV, 95 % CI, 0.98 to 1.70, p < 0.001). The overall assessment of all included trials showed a low risk of bias and low heterogeneity. Conclusions The pooled results of RCTs demonsrated with moderate to high evidence that 3,4-DAP has a significant effect on LEMS treatment, with improvements in muscle strength score and CMAP amplitude.