Compound Muscle Action Potential Area Research Articles

Pathologic classification of a late-onset peripheral neuropathy in a spontaneous Labrador retriever dog model.

Late-onset peripheral neuropathy (LPN) is a heritable canine neuropathy commonly found in Labrador retrievers and is characterized by laryngeal paralysis and pelvic limb paresis. Our objective was to establish canine LPN as a model for human hereditary peripheral neuropathy by classifying it as either an axonopathy or myelinopathy and evaluating length-dependent degeneration. We conducted a motor nerve conduction study of the sciatic and ulnar nerves, electromyography (EMG) of appendicular and epaxial musculature, and histologic analysis of sciatic and recurrent laryngeal nerves in LPN-affected and control dogs. LPN-affected dogs exhibited significant decreases in compound muscle action potential (CMAP) amplitude, CMAP area, and pelvic limb latencies. However, no differences were found in motor nerve conduction velocity, residual latencies, or CMAP duration. Distal limb musculature showed greater EMG changes in LPN-affected dogs. Histologically, LPN-affected dogs exhibited a reduction in the number of large-diameter axons, especially in distal nerve regions. In conclusion, LPN in Labrador retrievers is a common, spontaneous, length-dependent peripheral axonopathy that is a novel animal model of age-related peripheral neuropathy that could be used for fundamental research and clinical trials.

Normative parameters of motor nerve conduction studies in infants

Introduction. Electromyography (EMG) is a modern method of instrumental neurophysiological diagnostics, which includes two main techniques as nerve conduction studies and needle EMG. Parameters of motor nerve conduction studies have been used in a number of clinical studies to evaluate the effectiveness of treatment in children with spinal muscular atrophy (SMA) during the use of pathogenetic therapy (nusinersen). Now, in our country there are no verified normative parameters of motor nerve conduction studies in infants. It is also worth saying that neonatal screening for identifying SMA patients started in 2023 in our country, and currently gene therapy for this disease is increasingly used, so improving methods for instrumental assessment of the dynamics of the condition during treatment, including using EMG, is relevant. 
 Objective: to determine the normative parameters of motor nerve conduction studies in 1–6 months, 7–12 months, and 13–24 months infants without neurological pathology.
 Materials and methods: The motor nerve conduction studies were carried out using a 2-channel electromyograph Neuro-MVP-Micro (Russia) with electrical stimulation of the ulnar nerve and registration of the compound muscle action potential (CMAP) from the abductor digiti minimi muscle. This made it possible to determine the main parameters of the negative peak of the CMAP — distal latency, amplitude and area, and calculate the motor nerve conduction velocity (MNCV) along the distal part of the ulnar nerve. The obtained data for each parameter were subject to normal distribution and presented in the form of mean and standard deviation (M±SD), minimum and maximum values (min – max).
 Results: In the age range of 1–6 months, the amplitude of the CMAP (mV) was 5.0±1.0 (3.0–8.0); CMAP area (ms∙mV) — 9.1 ± 2.1 (5.5–12.9); distal latency (ms) — 2.2 ± 0.2 (1.6–2.5), MNCV (m/s) — 37.5 ± 5.4 (27.5–48.9).
 In the age range of 7–12 months, the amplitude of the CMAP (mV) was 6.2 ± 1.3 (3.8-9.3); CMAP area (ms∙mV) — 11.7 ± 3.0 (6.5–18.6); distal latency (ms) — 2.0 ± 0.2 (1.4–2.4), MNCV (m/s) – 48.4 ± 4.1 (42.1–55.2).
 In the age range of 13-24 months, the amplitude of the CMAP (mV) was 6.4 ± 0.6 (5.0-7.3); CMAP area (ms∙mV) — 13.3 ± 2.8 (9.8–18.2); distal latency (ms) — 2.2 ± 0.2 (1.8–2.5), MNCV (m/s) – 52.6 ± 3.8 (41.8–57.3).
 Conclusion. For the first time, normative parameters of motor nerve conduction studies were obtained in 1–6, 7–12, and 13–24 months infants without neurological pathology. This will make it possible to objectify neurophysiological parameters in neuromuscular diseases in infants.

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.

Radial motor nerve conduction studies recorded from triceps brachii and extensor carpi radialis longus: Techniques and reference values.

Optimal timing of nerve transfer surgery in cervical spinal cord injury (SCI) depends upon the integrity of lower motor neurons (LMNs) in recipient nerves, which is best predicted by compound muscle action potential (CMAP) amplitude. There are no established techniques for obtaining the CMAP in two recipient muscles: triceps brachii and extensor carpi radialis longus (ECRL). This study aimed to develop recording techniques for radial motor studies to triceps and ECRL, and to determine reference values for CMAP amplitudes in healthy volunteers. This was a prospective observational study of healthy adults aged 18 years and older. Motor nerve conduction studies were performed, stimulating the radial nerve in the axilla, over the axillary pulse at the pectoralis major insertion. Recording was from triceps (long head) and ECRL. CMAP amplitude, area, latency, and stimulus intensity were recorded. Reference values (RV) were calculated for CMAP amplitudes using a value 2 standard deviations below the mean. Cube root or logarithmic transformations were used to correct for non-normal distributions. Twenty-five healthy subjects participated. Triceps mean CMAP amplitude was 15.5mV (SD 4.19), with an RV of 8.1mV. ECRL mean CMAP amplitude was 11.5mV (SD 3.54), with an RV of 6.2mV. CMAP amplitude at ECRL was 75% (95% confidence interval 50%-100%) of that at triceps. We describe a technique for recording radial motor NCS from triceps and ECRL. Knowledge of normal CMAP amplitudes will help identify LMN injury in patients with cervical SCI being considered for nerve transfers.

Exercise test for patients with new-onset paroxysmal kinesigenic dyskinesia.

The pathogenesis of primary paroxysmal kinesigenic dyskinesia (PKD) remains unclear, and channelopathy is a possibility. In a pilot study, we found that PKD patients had abnormal exercise test (ET) results. To investigate the ET performances in patients affected by PKD, and the role of the channelopathies in the pathogenesis of PKD, we compared the ET results of PKD patients, control subjects, and hypokalemic periodic paralysis (HoPP) patients, and we analyzed ET changes in 32 PKD patients before and after treatment. Forty-four PKD patients underwent genetic testing for the PRRT2, SCN4A, and CLCN1 genes. Sixteen of 59 (27%) patients had abnormal ET results in the PKD group, while 28 of 35 (80%) patients had abnormal ET results in the HoPP group. Compared with the control group, the PKD group showed a significant decrease in the compound muscle action potential (CMAP) amplitude and area after the long ET (LET), while the HoPP group showed not only greater decreases in the CMAP amplitude and area after the LET but also greater increases in the CMAP amplitude and area immediately after the LET. The ET parameters before and after treatment were not significantly different. Nine of 44 PKD patients carried PRRT2 mutations, but the gene abnormalities were unrelated to any ET parameter. The PKD group demonstrated an abnormal LET result by electromyography (EMG), and this abnormality did not seem to correlate with the PRRT2 variant or sodium channel blocker therapy.

Use of CMAP, MScan fit-MUNE, and MUNIX in understanding neurodegeneration pattern of ALS and detection of early motor neuron loss in daily practice

BackgroundThe pattern of lower motor neuron (LMN) degeneration in amyotrophic lateral sclerosis (ALS), i.e., dying-back (from the nerve ending to cell body) or dying-forward (from the cell body to nerve ending), has been widely discussed. In this study, we aimed to evaluate LMN loss using compound muscle action potential (CMAP), motor unit number index (MUNIX), and MScan-fit-based motor unit number estimation (MUNE) to understand the pattern of neurodegeneration in ALS. MethodsTwenty-five patients were compared with 25 controls using CMAP amplitude and area, MUNIX, and MScan-fit MUNE in three proximal and distal muscles innervated by the ulnar nerve. ResultsUnlike the controls, the CMAP area, MScan-fit MUNE, and MUNIX recorded in ALS patients showed more neurodegeneration in distal muscles than proximal muscles. In ALS patients with unaffected CMAP amplitudes (n = 13), the CMAP area, MScan-fit MUNE, and MUNIX showed subtle motor unit loss of 30.7 %, 53.8 %, and 38.4 %, respectively. ConclusionThe CMAP area, MScan-fit MUNE, and MUNIX showed neurodegeneration earlier than the reduction in CMAP amplitude. These tests confirmed dying-back neurodegeneration, while only MUSIX showed re-innervation in ALS.

Radial motor nerve conduction studies in the upper arm.

The main goal of this study was to determine the contribution of the anterior forearm muscles to the compound muscle action potential (CMAP) recorded from the extensor digitorum (ED) after proximal stimulation. Twenty-one healthy volunteers and 114 patients with compressive and traumatic radial neuropathies were examined. Stimulation was carried out at six different points: distal third of the upper arm; Erb's point; axilla; medial upper arm; antecubital fossa; and ulnar groove. In the control group, Erb's CMAP area was significantly greater than the distal CMAP area. In compressive neuropathy, there was conduction block, but no change in conduction velocity. There were no differences in Erb's CMAP latencies between the control group and the neuropathies group. CMAPs recorded over the ED with stimulation at the brachial plexus represent the sum of the motor unit action potentials of the posterior and anterior forearm muscles.

Motor unit number index and compound muscle action potential amplitude

ObjectivesMUNIX (motor unit number index), derived from the compound muscle action potential (CMAP) and surface EMG interference pattern (SIP) has become popular as a substitute for motor unit number estimation (MUNE). This study was undertaken to determine why, in recent recordings from amyotrophic lateral sclerosis (ALS) patients and healthy controls, we found that MUNIX values resembled CMAP amplitudes more closely than MUNE values. MethodsThe relationship between MUNIX and CMAP and SIP amplitudes was investigated by a theoretical analysis and by reanalysing the data from the previous study. ResultsTheory indicates that when motor unit potentials overlap extensively, information about motor unit size and number is lost, and MUNIX depends only on CMAP area and power. Accordingly, MUNIX values were found to be sensitive to changes in CMAP amplitude but insensitive to changes in SIP amplitude. The reproducibility of MUNIX measurements in healthy controls was found to depend almost entirely on correlation with CMAP properties. ConclusionsMUNIX gives misleading information about motor unit numbers in healthy controls, and provides little information about loss of motor units in ALS patients beyond that given by simple CMAP amplitude measurements. SignificanceMUNIX should not be interpreted as a MUNE method.

T127. Electrophysiological study on selecting damage of fast motor neuron in early stage of ALS

Introduction The motor neuronal damage is selective in the early stage of amytrophic lateral sclerosis (ALS), and the large motor neurons with rapid conduction may be the earliest involved. The purpose of this study is based on the analysis of the correlation between the changes of F wave minimum latencies, distal motor latencies (DML) and the compound muscle action potentials (CMAP) and negative area of CMAP to seek for the evidence supporting preferential vulnerability of fast motor neuron in early stage of ALS. Methods This study enrolled the definite and probable diagnosis ALS (according to revised EI criteria) patients in our outpatient clinic from January 2016 to October 2017. The inclusion criteria of early ALS patients: the strength of upper limbs higher than 3/5 MRC levels and revised ALS-FRS score greater than 25 points. In addition, the matched healthy people were selected as the control group. All participants were evaluated by physical examination, nerve conduction studies, and standard needle EMG and we focused on the values including DML, CMAP (from the baseline to negative wave peaks), negative peak area and F wave of minimum latencies in the median nerve. Results Forty-five patients (27 male) of ALS group, mean 55.8 ± 11.9 years, height 165.8 ± 6.7 cm,duration of disease 12.3 ± 6.3 months, revised ALS-FRS score 31.5 ± 4.1. The site of symptom onset from upper limb was 27 (60%), and from bulbar was 18 (40%). In the normal control group, there were 46 (27 male) subjects, mean 56.3 ± 12.0 years, height 164.6 ± 7.4 cm. Age, gender and height matched with ALS group. DML in the median showed no significant difference ( P = 0.138) between control and ALS group, meanwhile the median nerve conduction velocity showed in normal range. But the minimal latencies of F wave revealed more longer ( P P P R = −0.593, P ± 0.001; R = −0.530, P = 0.001), and did the same pattern to the F wave minimum latency ( R = −0.635, P = 0.001; R = 0.634, P = 0.001). Conclusion Based on the evidence of negative correlation between mildly prolonged the minimal latency of the F wave and decreased CMAP or negative wave area, the fast motor neurons show preferentially vulnerable in the early stage of ALS.

P335 Comparison of median nerve distal motor responses in patients with chronic inflammatory demyelinating polyneuropathy and carpal tunnel syndrome

Objective Dispersion of distal compound muscle action potential (CMAP) is a useful finding for showing demyelination. In this study, we aimed to compare the duration and area of CMAP of median nerve between cases with Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) and Carpal Tunnel Syndrome (CTS). Material and methods Ninety-two participants (thirty patients with CDIP, 32 patients with CTS and 30 participants of normal control group) who were evaluated. The CMAP duration was measured from the onset of the initial negative potential to the terminal negative deflection back to baseline. The CMAP area calculation was performed by computerized EMG machine. Results A significant difference was not found between groups as for mean age of the groups, and distribution of genders (CIDP: 52,73 ± 12,34 years, 18 (%40) women, 12 (%60) men; CTS: 52,38 ± 11,83 years, 25 (%78,1) women, 7 (%21,9) men; control: 48,5 ± 14,41 years,22 (%79,3) women, and 8 (%26,7) men). The mean CMAP duration of patients with CIDP was significantly higher than patients with CTS (p: 0.003) and control group (p: 0.001), however there was not any significant difference between the patients with CTS and control group (p > 0.05). The mean CMAP area of patients with CIDP was significantly lower than patients with CTS (p: 0.003) and control group (p: 0.001), however there was not any significant difference between the patients with CTS and control group (p > 0.05). Conclusion These findings suggest that the duration and area of distal CMAP is a useful parameter for the differentiation of patients with CIDPand CTS.

Electrophysiological Study of Femoral Nerve Function After a Continuous Femoral Nerve Block for Anterior Cruciate Ligament Reconstruction: A Randomized, Controlled Single-Blind Trial

Background: A continuous femoral nerve block (CFNB) is an effective analgesic treatment after anterior cruciate ligament (ACL) reconstruction but may result in transient femoral nerve injuries and quadriceps muscle weakness, which in turn contribute to worsened functional outcomes. Purpose: To compare electrophysiological criteria of a femoral nerve injury as well as functional and pain-related outcomes after ACL reconstruction when analgesia was provided by a CFNB or intravenous patient-controlled analgesic of morphine (IV PCA). Study Design: Randomized controlled clinical trial; Level of evidence, 1. Methods: A total of 74 patients scheduled for ACL reconstruction were randomized to receive a CFNB before surgery, followed by a ropivacaine infusion for 2 days and oxycodone, or IV PCA. The primary outcome was the rate of femoral nerve injuries at 4 weeks postoperatively, defined as a reduction of the compound muscle action potential (CMAP) area from the vastus medialis muscle after supramaximal femoral nerve stimulation at the groin, associated with an absent H-reflex of the femoral nerve and signs of vastus medialis muscle denervation. Secondary functional outcomes were quadriceps muscle strength, active flexion range, and distance walked, as measured on postoperative days 1 and 2. Secondary pain-related outcomes were IV morphine consumption and pain scores at rest and on movement in phase 1 recovery and on postoperative days 1 and 2. Results: No patients met the electrophysiological criteria of a femoral nerve injury. The mean CMAP area at 4 weeks was equivalent in both the CFNB and IV PCA groups (47 ± 16 mV·ms and 51 ± 13 mV·ms, respectively; P = .50). While no differences were detected in functional outcomes or pain scores, the consumption of an IV morphine equivalent was reduced by the administration of a CFNB in phase 1 recovery (6 ± 5 mg and 13 ± 7 mg, respectively; P = .0003), on postoperative day 1 (6 ± 7 mg and 19 ± 17 mg, respectively; P = .0005), and on postoperative day 2 (11 ± 10 mg and 19 ± 17 mg, respectively; P = .03) compared with an IV PCA. Conclusion: Despite prior contrary reports, a CFNB did not result in femoral nerve injuries or worsened functional outcomes after ACL reconstruction. The improvement of analgesia with a CFNB was only marginal and not clinically relevant beyond 24 hours. Registration: NCT01321138 (ClinicalTrials.gov identifier).

Motor unit number index examination in dominant and non-dominant hand muscles

This study investigated the effect of handedness on motor unit number index (MUNIX). Maximal hand strength, compound muscle action potential (CMAP) and voluntary surface electromyography (EMG) signals were measured bilaterally for the first dorsal interosseous (FDI) and thenar muscles in 24 right-handed and 2 left-handed healthy subjects. Mean (±standard error) grip and pinch forces in the dominant hand were 43.99 ± 2.36 kg and 9.36 ± 0.52 kg respectively, significantly larger than those in the non-dominant hand (grip: 41.37 ± 2.29 kg, p < .001; pinch: 8.79 ± 0.46 kg, p < .01). Examination of myoelectric parameters did not show a significant difference among the CMAP area, the MUNIX or motor unit size index (MUSIX) between the two sides in the FDI and thenar muscles. In addition, there was a lack of correlation between the strength and myoelectric parameters in regression analysis. However, strong correlations were observed between dominant and non-dominant hand muscles in both strength and myoelectric measures. Our results indicate that the population of motor units or spinal motor neurons as estimated from MUNIX may not be associated with handedness. Such findings help understand and interpret the MUNIX during its application for clinical or laboratory investigations.

The usefulness of proximal radial motor conduction in acute compressive radial neuropathy.

Background and PurposeThe objective of this study was to determine diagnostic and prognostic values of proximal radial motor conduction in acute compressive radial neuropathy.MethodsThirty-nine consecutive cases of acute compressive radial neuropathy with radial conduction studies-including stimulation at Erb's point-performed within 14 days from clinical onset were reviewed. The radial conduction data of 39 control subjects were used as reference data.ResultsThirty-one men and eight women (age, 45.2±12.7 years, mean±SD) were enrolled. All 33 patients in whom clinical follow-up data were available experienced complete recovery, with a recovery time of 46.8±34.3 days. Partial conduction block was found frequently (17 patients) on radial conduction studies. The decrease in the compound muscle action potential area between the arm and Erb's point was an independent predictor for recovery time.ConclusionsProximal radial motor conduction appears to be a useful method for the early detection and prediction of prognosis of acute compressive radial neuropathy.

Quantification of muscle-derived signal interference during monopolar needle electromyography of a peripheral nerve interface in the rat hind limb.

High-fidelity signal acquisition is critical for the fundamental control of a neuroprosthesis. Our group has developed a bio-artificial interface consisting of a muscle graft neurotized by a severed nerve in a rat hind limb model. This regenerative peripheral nerve interface (RPNI) permits nerve signal transmission, amplification, and detection via in situ electromyography (EMG). Our study examined the magnitude of signal interference from simultaneously contracting muscles adjacent to our muscle of interest. In eighteen F344 rats, the extensor digitorum longus (EDL) muscle was used to fabricate simulated RPNI constructs of various sizes in which the neurovascular pedicle was preserved, obviating the need for reinnervation or revascularization. After 3 weeks of recovery, in situ EMG testing was performed using electrical stimulation of the common peroneal nerve. A recording needle was placed in the EDL muscle with a reference/ground electrode in the contralateral toe webspace, comprising a monopolar recording configuration. The superficial peroneal nerve was transected to further isolate stimulation of the anterior compartment. Recordings from the EDL were performed before and after excision of the tibialis anterior (TA) and extensor hallucis longus (EHL) muscles. After TA/EHL excision, EDL compound muscle action potential (CMAP) peak-to-peak amplitudes were significantly lower by an average of 7.4±5.6(SD) mV, or 32±18%, (paired t(17)=-5.7, p<;0.0001). A significant positive linear correlation was seen between CMAP amplitude and EDL mass both before TA/EHL excision (r=0.68, n=18, p<;0.01) and after TA/EHL excision (r=0.79, n=18, p<;0.0001). EDL mass did not correlate with differences in CMAP amplitude or area caused by TA/EHL excision. Monopolar needle EMG recordings from the EDL muscle are significantly, but predictively, contaminated by concomitant muscular contractions in the anterior compartment of the rat hind limb. Further investigation of strategies to reduce this signal interference, including electrode choice or configuration, use of bioelectrical insulators, and filtering methods, is warranted to promote high-fidelity signal acquisition for prosthetic control.

2013 Neer Award: Effect of the adipose-derived stem cell for the improvement of fatty degeneration and rotator cuff healing in rabbit model

This study was conducted to verify the effects of adipose-derived stem cells (ADSCs) on tendon healing and reversal of fatty infiltration in a chronic rotator cuff tear model by using the rabbit subscapularis (SSC). The SSC insertions in 32 rabbits were cut bilaterally. After 6 weeks, secondary procedures were performed bilaterally, dividing the rabbits into 4 groups of 8 rabbits each as follows: the ADSC+repair group, saline+repair group, ADSC-only group, and saline-only group. A fifth group of 8 rabbits served as normal controls (control group). Electromyographic, biomechanical, and histologic analyses were performed 6 weeks after the secondary procedures. All SSC tendons in the ADSC-only and saline-only groups failed to heal and were excluded fromthe electromyographic and biomechanical tests. On electromyographic evaluation, the ADSC+repair group exhibited a larger compound muscle action potential area than the saline+repair group (11.86 ± 2.97 ms · mV vs 9.42 ± 3.57 ms · mV, P = .029), and this response was almost at the level of the control group (13.17 ± 6.6 3 ms · mV, P = .456). Biomechanically, the load-to-failure of the ADSC+repair group (87.02 ± 29.81 N) was higher than that of the saline+repair group (59.85 ± 37.77 N), although this difference did not reach statistical significance (P = .085). Histologically, the mean proportions of fatty infiltration in the SSC muscles were 29% ± 15%, 43% ± 9%, 51% ± 14%, 63% ± 10%, and 18% ± 9% for the ADSC+repair, saline+repair, ADSC-only, saline-only, and control groups, respectively (P < .001). The degree of fat staining increased from the ADSC+repair group (unclear or weak) to the saline-only group (strongly present). Local administration of ADSCs might have the possibility to improve muscle function and tendon healing and decrease fatty infiltration after cuff repair.

Effect of the Refrigerator Storage Time on the Potency of Botox for Human Extensor Digitorum Brevis Muscle Paralysis

Background and PurposeIt is recommended that Botox be used within 5 hours of reconstitution, which results in substantial quantities being discarded. This is not only uneconomic, but also inconvenient for treating patients. The aim of this study was to determine the potencies of Botox used within 2 hours of reconstitution with unpreserved saline, the same Botox refrigerated (at +4℃) 72 hours after reconstitution, and during the next 4 consecutive weeks (weeks 1, 2, 3, and 4). This comparison was used to determine the length of refrigeration time during which reconstituted Botox will maintain the same efficacy as freshly reconstituted toxin.MethodsIndividual paralysis rates in the extensor digitorum brevis (EDB) compound muscle action potential (CMAP) amplitude and area were measured 1 week after injecting fresh reconstituted 2.5 MU of Botox on one side of the foot, and when the same quantity of Botox that had been refrigerated for a designated time (i.e., 72 h, or 1, 2, 3, or 4 weeks) into the other side of the foot. The EDB CMAP amplitude and area at 12 and 16 weeks postinjection were also measured to compare the efficacy durations in all five comparative groups.ResultsNinety-four volunteers were divided into five groups according to the refrigerator storage time of the second Botox injection. The paralysis of the EDBs was significant for each injection of Botox, both fresh and refrigerated, with no statistically significant differences between them, regardless of the refrigeration time. There was a tendency toward increased CMAP amplitude and area at 12 or 16 weeks postinjection (p<0.0001). The duration of effective muscle paralysis did not differ significantly throughout the 16-week follow-up period between all five groups.ConclusionsThe potency of reconstituted Botox is not degraded by subsequent refrigeration for 4 weeks. However, there are definite concerns regarding its sterility, and hence its safety, since multiple withdrawals from the same vial over long periods can introduce bacterial contamination.

Quantification of Regenerative Peripheral Nerve Interface Signal Transmission

INTRODUCTION: Amputees prefer body-powered, cable operated prosthetics over those with advanced technology. Our solution is to surgically construct an interface at residual peripheral nerves endings. Regenerative peripheral nerve interface (RPNI) devices are composed of: a) host muscle freely grafted to the residual stump area, b) residual peripheral nerves for neurotizing the muscle, c) implanted recording electrodes, and d) decellularized small intestine submucosa (SIS) wrap. This study's purpose is to quantify signal transmission at RPNI devices in the rat. The hypothesis is: RPNI devices communicate peripheral nerve signaling with capacities approaching Sham devices. METHODS: F344 rats (n=29) were randomized into 3 groups. During Sham surgeries, the right soleus muscle was exposed (Sham, n=11). For RPNI not neurotized (RPNI-NN, n=9) and neurotized (RPNI+N, n=9) devices, the left peroneal nerve was divided and the right soleus muscle was transferred to the left thigh simulated residual limb area. For the RPNI+N device, the divided left nerve was used to neurotize the soleus. SIS was wrapped around all devices. Electrodes were implanted at evaluation. Measurements included nerve conduction, force capacity, and histology after 1 or 3 months of convalescence. RESULTS: Comparisons of RPNI compound muscle action potentials (CMAP), muscle mass, and stimulation thresholds between months 1 and 3 indicated ongoing regeneration and reinnervation. At 3 months, RPNI+N CMAP amplitude, CMAP area, device force, and motor unit number were 50% to 100% those of Sham devices (Table 1). RPNI-NN values were significantly lower than Sham (p<.05). Histology showed RPNI+N contained healthy axons with robust myelination that were organized with muscle fibers.Table 1: Table 1.CONCLUSION: Successful peripheral nerve interfacing which approached sham functioning was achieved through neurotization of regernerative peripheral nerve interface (RPNI) devices. DISCLOSURES: Supported by: DoD Multidisciplinary University Research Initiative (MURI) program (#W911NF0610218), NIH T32, (#GM0008616-11), Plastic Surgery Educational Foundation (#174964).

3. Value of the exercise compound muscle action potential study and provocative tests in possible periodic paralysis

Introduction: Pathogenic mutations can be identified in up to 70% of patients with periodic paralysis (PP). However, a substantial proportion of individuals with typical PP symptoms do not carry the known mutations. And, there are many patients with atypical symptoms referred for evaluation. Objectives: To evaluate whether the sensitivity of the exercise compound muscle action potential (CMAP) study is improved after provocative tests for the diagnosis of PP and to determine whether these tests are of value in assessing patients with possible periodic paralysis (P3). Methods: Six patients with genetically or clinically definite PP, 11 patients with P3, and 21 healthy volunteers were studied. The exercise CMAP study (McManis protocol) and serum potassium were performed before and after bicycle exercise and after oral glucose and potassium loading. Abnormal decrement is defined as >40% decline in CMAP amplitude or >50% in CMAP area. Healthy volunteers only participated in the bicycle exercise. Results: Of 6 definite PP participants, 4 (67%) had abnormal decrement on the pre-bicycle study compared to 4 (36%) in the P3 participants. Although percent decrement was similar in each group, time-to-nadir appeared to be longer in the P3 group (52.6 versus 40 min). Of 9 participants who had normal baseline studies, glucose loading provoked abnormal decrement in 1 definite PP, and potassium loading provoked hyperkalemia and abnormal decrement in 1 possible PP. All healthy volunteers had normal exercise CMAP studies. Conclusion: Abnormal exercise CMAP study occurs in both definite and possible PP. Provocative testing may improve the diagnostic accuracy in a mutation-negative possible PP.

Assessment of a Neurophysiological Model of the Mandibular Branch of the Facial Nerve in Rats by Electromyography

Our objective was to develop an experimental model for the noninvasive and objective evaluation of facial nerve regeneration in rats using a motor nerve conduction test (electromyography). Twenty-two rats were submitted to neurophysiological evaluation using motor nerve conduction of the mandibular branch of the facial nerve to obtain the compound muscle action potentials (CMAPs). To record the CMAPs, we used two needle electrodes that were inserted into the lower lip muscle of the rat. A supramaximal electrical stimulus was applied, and the values of CMAP latency, amplitude, length, area, and stimulus intensity obtained from each side were compared by use of the Wilcoxon test. There was no significant difference (all p > 0.05) in latency, amplitude, duration, area, or intensity of stimuli between the two sides. The amplitudes ranged between 1.61 and 8.30 mV, the latencies between 1.03 and 1.97 ms, and the stimulus intensities between 1.50 and 2.90 mA. This is a noninvasive, easy, and highly reproducible method that contributes to an improvement of the techniques previously described and may contribute to future studies of the degeneration and regeneration of the facial nerve.

Activity-dependent conduction block in chronic inflammatory demyelinating polyneuropathy

Previous studies suggested that activity-dependent conduction block (CB) contributes to weakness in chronic inflammatory demyelinating polyneuropathy (CIDP). These studies, however, investigated only one nerve segment per patient, employed cervical magnetic stimulation which may be submaximal, included nerves with extremely low compound muscle action potentials (CMAPs) which precludes assessment of CB, and lacked predefined criteria for activity-dependent CB. Obtaining more robust evidence for activity-dependent CB is important because it may be treated pharmacologically. We investigated 22 nerve segments in each of 18 CIDP patients, employed supramaximal electrical stimulation, excluded nerves with markedly reduced CMAPs, and adopted criteria for activity-dependent CB. Each nerve was tested before and immediately after 60 s of maximal voluntary contraction (MVC) of the relevant muscle. Per nerve segment we calculated segmental area ratio: (area proximal CMAP)/(area distal CMAP). Per nerve we calculated total area ratio: (area CMAP evoked at Erb's point)/(area most distally evoked CMAP). MVC induced no change in mean area ratios and no activity-dependent CB according to our criteria, except for one segment. MVC induced increases in distal and proximal CMAP area and duration. In segments with demyelinative slowing, MVC induced an increase in CMAP duration prolongation. Thus, in CIDP, muscle activity induces virtually no CB, but it may increase temporal dispersion of nerve action potentials.