Distal Compound Muscle Action Potential Research Articles

Compound Muscle Action Potential and Myosin-Loss Pathology in Patients With Critical Illness Myopathy: Correlation and Prognostication.

Prolonged compound muscle action potential (CMAP) duration and preferential loss of myosin are considered the diagnostic hallmarks of critical illness myopathy (CIM); however, their correlation and prognostic values have not been studied. We aimed to investigate the correlation between CMAP duration and myosin loss and their effect on mortality by comparing between patients with CIM with and without myosin loss. We searched the Mayo Clinic Electromyography Laboratory databases (1986-2021) for patients diagnosed with CIM on the basis of prolonged distal CMAP durations (>15 msec in fibular motor nerve studies recording over the tibialis anterior or >8 msec in other motor nerves) and needle EMG findings compatible with myopathy. Electrodiagnostic studies were generally performed within 24 hours after weakness became noticeable. We included only patients who underwent muscle biopsy. Clinical, electrophysiologic, and myopathologic data were reviewed. We conducted myosin/actin ratio analysis when muscle tissue was available. We used the Fisher exact test for categorical data comparisons and the Mann-Whitney 2-tailed test for continuous data. We applied the Kaplan-Meier technique to analyze survival rates. Twenty patients (13 female patients) were identified [median age at diagnosis of 62.5 years (range: 19-80 years)]. The median onset of weakness was 24 days (range: 1-128) from the first day of intensive care unit admission. Muscle biopsy showed myosin loss in 14 patients, 9 of whom had >50% of myofibers affected (high grade). Type 2 fiber atrophy was observed in 19 patients, 13 of whom also had myosin loss. Patients with myosin loss had higher frequency of steroid exposure (14 vs 3; p = 0.004); higher median number of necrotic fibers per low-power field (2.5 vs 1, p = 0.04); and longer median CMAP duration (msec) of fibular (13.4 vs 8.75, p = 0.02), tibial (10 vs 7.8, p = 0.01), and ulnar (11.1 vs 7.95, p = 0.002) nerves compared with those without. Only patients with high-grade myosin loss had reduced myosin/actin ratios (<1.7). Ten patients died during median follow-up of 3 months. The mortality rate was similar between patients with and without myosin loss. Patients with high-grade myosin loss had a lower overall survival rate than those with low-grade or no myosin loss, but this was not statistically significant (p = 0.05). Myosin loss occurred in 70% of the patients with CIM with prolonged CMAP duration. Longer CMAP duration predicts myosin-loss pathology. The extent of myosin loss marginally correlates with the mortality rate. Our findings highlight the potential prognostic values of CMAP duration and myosin loss severity in predicting disease outcome.

Impact of 2021 European Academy of Neurology/Peripheral Nerve Society diagnostic criteria on diagnosis and therapy of chronic inflammatory demyelinating polyradiculoneuropathy variants.

There are different criteria for the diagnosis of different variants of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). The 2021 European Academy of Neurology/Peripheral Nerve Society (EAN/PNS) guidelines provide specific clinical criteria for each CIDP variant even if their therapeutical impact has not been investigated. We applied the clinical criteria for CIDP variants of the 2021 EAN/PNS guidelines to 369 patients included in the Italian CIDP database who fulfilled the 2021 EAN/PNS electrodiagnostic criteria for CIDP. According to the 2021 EAN/PNS clinical criteria, 245 patients achieved a clinical diagnosis of typical CIDP or CIDP variant (66%). We identified 106 patients with typical CIDP (29%), 62 distal CIDP (17%), 28 multifocal or focal CIDP (7%), four sensory CIDP (1%), 27 sensory-predominant CIDP (7%), 10 motor CIDP (3%), and eight motor-predominant CIDP (2%). Patients with multifocal, distal, and sensory CIDP had milder impairment and symptoms. Patients with multifocal CIDP had less frequently reduced conduction velocity and prolonged F-wave latency and had lower levels of cerebrospinal fluid protein. Patients with distal CIDP more frequently had reduced distal compound muscle action potentials. Patients with motor CIDP did not improve after steroid therapy, whereas those with motor-predominant CIDP did. None of the patients with sensory CIDP responded to steroids, whereas most of those with sensory-predominant CIDP did. The 2021 EAN/PNS criteria for CIDP allow a better characterization of CIDP variants, permitting their distinction from typical CIDP and more appropriate treatment for patients.

Therapeutic Outcomes and Electrophysiological Biomarkers in Anti-Myelin-Associated Glycoprotein Neuropathy: A Multicenter Cohort Study in South Korea.

Unlike other immune-mediated neuropathies, anti-myelin-associated glycoprotein (MAG) neuropathy is often refractory to immunotherapy. It is necessary to compare the relative efficacies of various immunotherapies and develop objective biomarkers in order to optimize its clinical management. This study recruited 91 patients with high anti-MAG antibody titers from 7 tertiary hospitals in South Korea. We analyzed the baseline characteristics, therapeutic outcomes, and nerve conduction study (NCS) findings of 68 patients and excluded 23 false positive cases. The rate of positive responses to treatment was highest using zanubrutinib (50%) and rituximab (36.4%), followed by corticosteroids (16.7%), immunosuppressants (9.5%), intravenous immunoglobulin (5%), and plasma exchange (0%). Disability and weakness were significantly associated with multiple NCS parameters at the time of diagnosis, especially distal compound muscle action potential (CMAP) amplitudes. Moreover, the longitudinal trajectory of the average CMAP amplitudes paralleled the clinical courses, with a 16.2 percentile decrease as an optimal cutoff for predicting a clinical exacerbation (area under the receiver operating characteristic curve=0.792). Our study supports the use of NCS as an objective marker for estimating disease burden and tracking clinical changes in patients with anti-MAG neuropathy. We have described the beneficial effects of rituximab and a new drug, zanubrutinib, compared with conventional immunotherapies.

Electrodiagnostic profile of conduction slowing in amyotrophic lateral sclerosis

ObjectiveSince motor nerve conduction slowing can occur due to loss of large axons, we investigate the conduction slowing profile in amyotrophic lateral sclerosis (ALS) and identify the limits beyond which the diagnosis of exclusive axonal loss is unlikely. MethodsFirst, using linear regression analysis, we established the range of motor conduction slowing in 76 chronic inflammatory demyelinating polyneuropathy (CIDP) patients. Demyelinating range confidence intervals were defined by assessing conduction velocity (CV), distal latency (DML), and F-wave latency (F) in relation to distal compound muscle action potential (CMAP) amplitude of median, ulnar, fibular, and tibial nerves. Results were subsequently validated in 38 additional CIDP patients. Then, the newly established demyelination confidence intervals were used to investigate the profile of conduction slowing in 95 ALS patients. ResultsCV slowing, prolonged DML, and abnormal F were observed in 22.2%, 19.6%, and 47.1% of the studied nerves respectively in ALS patients. When slowing occurred, it affected more than one segment of the motor nerve, suggesting that CMAP amplitude dependent conduction slowing caused by an exclusive loss of large axons is the main mechanism of slowing. No ALS patient had more than 2 nerves with CV slowing in the confidence interval defined by the regression equations or the American Academy of Neurology (AAN) research criteria for CIDP diagnosis. ConclusionsThe presence of more than two motor nerves with CV slowing in the demyelinating range defined by the regression analysis or AAN criteria in ALS patients suggests the contribution of acquired demyelination or other additional mechanisms exist in the electrodiagnostic profile of ALS.

Motor Nerve Conduction Slowing in Amyotrophic Lateral Sclerosis (P10-8.006)

<h3>Objective:</h3> To determine the range of conduction values for motor nerve conduction slowing and further characterize the distribution of conduction slowing in ALS and characterize the limits of conduction slowing beyond which the diagnosis of ALS is uncertain. <h3>Background:</h3> Abnormal motor nerve conduction studies in ALS are attributed to loss of large axons and distal axonopathy, however conduction slowing can be the result of superimposed demyelinating polyneuropathy or an alternate diagnosis. <h3>Design/Methods:</h3> The electrodiagnostic data of 76 chronic inflammatory demyelinating polyneuropathy (CIDP) patients, identified using AAN research criteria was used to create 12 novel equations using regression analysis that determine a range of the expected slowing of a primary demyelinating polyneuropathy. Demyelinating range confidence intervals were defined by assessing conduction velocity (CV), distal latency (DL), and F latency in relation to distal compound muscle action potential (CMAP) amplitude of median, ulnar, fibular, and tibial nerves. Results were then validated in 38 additional CIDP patients. These developed equations were then used to evaluate conduction slowing in 95 patients with ALS. Transformed CMAP amplitude was used as an independent variable whereas transformed DL, CV, and F were used as dependent variables. <h3>Results:</h3> CV slowing, prolonged DL, and abnormal F latency were observed respectively in 22.2%, 19.6%, and 46.7% of the studied nerves. When slowing occurred, it affected more than one segment of the motor nerve, suggesting that loss of large axons is the main mechanism of slowing. No ALS patient had more than 2 nerves with CV slowing in the confidence interval defined by the regression equations or the American Academy of Neurology (AAN) research criteria for CIDP diagnosis. <h3>Conclusions:</h3> The presence of more than two motor nerves with CV slowing in the demyelinating range defined by the regression analysis or AAN criteria in ALS patients suggests an alternative diagnosis or superimposed demyelination. <b>Disclosure:</b> Mr. Mandava has nothing to disclose. Miss Shaikh has nothing to disclose. Mr. Jaffry has nothing to disclose. Mr. Jaffry has nothing to disclose. Mr. Ors has nothing to disclose. Mr. Trivedi has nothing to disclose. Ms. Faiz has nothing to disclose. Mr. Gandhi has nothing to disclose. Dr. Patel has nothing to disclose. Abu Nasar, MD has nothing to disclose. Ankit Pahwa has nothing to disclose. Dr. Sander has received personal compensation for serving as an employee of Grifols. Dr. Sander has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Grifols. Dr. Sander has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for Law firm. Dr. Souayah has received publishing royalties from a publication relating to health care.

Compound muscle action potential duration ratio for differentiation between Charcot-Marie-Tooth disease and CIDP

ObjectiveTo elucidate the utility of the proximal to distal compound muscle action potential (CMAP) duration ratio to distinguish between demyelinating Charcot-Marie-Tooth disease (CMT) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) compared with nerve ultrasound. MethodsThirty-nine demyelinating CMT patients and 19 CIDP patients underwent nerve conduction studies (NCS) and nerve ultrasound. NCS parameters including CMAP duration ratio calculated by dividing the value at the proximal site by that at the distal site and nerve cross-sectional area (CSA) measured by ultrasound were compared between the two groups. The diagnostic sensitivity and specificity of each parameter were analysed. ResultsCMT patients showed a significantly lower CMAP duration ratio than CIDP patients (p < 0.05). The area under the curve (AUC) value of the CMAP duration ratio exceeded 0.95 when CMT was considered “positive”, and a cut-off value of 1.13 resulted in high diagnostic sensitivity and specificity (84.6 and 100 % for median nerve, 97.4 and 85.7 % for ulnar nerve, respectively), whereas the AUC value of nerve CSA ranged from 0.70 to 0.81. ConclusionsThe CMAP duration ratio could effectively distinguish between demyelinating CMT and CIDP. SignificanceAdding the CMAP duration ratio to a routine NCS may improve the accuracy of the diagnosis of demyelinating CMT.

Study of total duration of distal compound muscle action potential in demyelinating and axonal Guillain-Barre’ syndrome

ABSTRACT Objectives Electrophysiology plays a crucial role in Guillain-Barré syndrome (GBS) diagnosis and subtype classification. The aim of our study was to assess the potential role of distal compound muscle action potential (dCMAP) for early differentiation between acute inflammatory demyelinating polyneuropathy (AIDP) and axonal GBS. Methods We retrospectively reviewed the medical records of 24 subjects with AIDP and 18 subjects with axonal GBS. We built up receiver operating characteristic curves for total dCMAP duration and negative phase of dCMAP duration, in order to derive cut-off values able to differentiate between AIDP and axonal GBS. Results The total duration of dCMAP was significantly prolonged in AIDP compared to axonal GBS. AUCs, odds ratio and positive predictive values were higher for total duration than for negative peak duration. Nerve conduction parameters in the lower limbs were more sensitive than those in the upper limbs in distinguishing AIDP from axonal GBS. Discussion Total duration of dCMAP dispersion may capture an adjunctive component of distal demyelination, not measured by the more traditional parameters and may thus represent a useful tool for early differentiation between AIDP and axonal GBS.

Pre- and intra-operative prognostic factors of facial nerve function in cerebellopontine angle surgery

PurposeThe study assesses whether pre- and intraoperative factors linked to electromyography and direct electrical stimulation (DES) of facial nerve can predict facial nerve function in the short- (12 days) and long-term (1 year) after cerebellopontine angle (CPA) tumor resection.Methods157 patients who underwent surgical resection of CPA tumors with facial nerve monitoring. Pre-operative factors (age, tumor size, pure tone average), surgical time and intra-operative parameters regarding facial function, minimum stimulation threshold (MST), compound muscle action potential (CMAP) and the difference between proximal and distal CMAP (DPDC) were evaluated.ResultsA correlation between tumor size, MST, CMAP and facial function in both short and long term was found. A higher grade of immediate facial paralysis corresponded to a higher risk of poor outcome after one year. A postoperative House–Brackmann (HB) score of V or VI was correlated with poor outcome in 88.8% and 93.8% of cases. A risk of HB 3 or more, in the long term, was correlated with a tumor size of 20.2 mm. Using an MST of 0.1 mA, for long-term predictions, sensitivity and specificity were 0.62 (95% CI 0.46–0.75) and 0.73 (95% CI 0.61–0.82), respectively. With a CMAP cut-off < 200 µV, for long-term prediction, sensitivity was 0.73 (95% CI 0.53–0.87) and specificity 0.73 (95% CI 0.55–0.85).ConclusionThe assessment based on the cut-offs described increases the ability to predict facial function. Improving predictive accuracy enables surgeons to address patients’ expectations and to establish an intervention timeline for planning facial reanimation.

Investigation of graphene-coated Ag/AgCl electrode performance in surface electromyography measurement

Conventional silver-silver chloride (Ag/AgCl) electrodes are widely used for recording surface electromyography (sEMG) with a conductive gel. However, for long-term sEMG recording, the gel has some disadvantages that cause high impedance. Therefore, the dry electrodes have been alternatively purposed to overcome these disadvantages. Recently, the nanomaterial-based dry electrodes have been developed for long term electrophysiological signal recording. In the present study, we aimed to develop a graphene-coated Ag/AgCl electrode for long-term recording. We transferred single layer graphene (SLG) on the Ag/AgCl electrode surface by using chemical vapor deposition and confirmed this process by Raman scattering spectroscopy and scanning electron microscopy. We then compared the graphene-coated Ag/AgCl and conventional Ag/AgCl electrodes by evaluating median motor nerve conduction studies (mNCS) and their impedance. The charge transfer resistance (Rct) for the Ag/AgCl electrode (4170 Ω) was much higher than graphene-coated Ag/AgCl electrode (Rct = 24.6 Ω). For median mNCS measurements without gel, the graphene-coated Ag/AgCl electrode provided a better amplitude of distal and proximal compound muscle action potential (28.3 mV and 25.8 mV, respectively) than the Ag/AgCl electrode (21.8 mV and 20.9 mV, respectively). Consequently, the present study suggests promising results in terms of the usability of graphene-coated Ag/AgCl electrodes for long-term monitoring and wearable systems applications of sEMG. In future studies, we aim to investigate clinical applicability of graphene-coated sEMG electrodes that include extended clinical settings and larger study population.

The impacts of poor glycemic control and disease duration on peripheral nerves in children and adolescents with type 1 diabetes mellitus

Objective: To evaluate the risk factors of subclinical neuropathy, and the nerve conduction study (NCS) results in children, and adolescents with type 1 diabetes mellitus (T1DM). Methods: A total of 81 patients without neuropathy symptoms were studied. Demographical features, pubertal stage, disease duration, NCS results, lipid profile results in the last 2 years, HbA1c results in the last 5 years, and the types of treatments (multiple-dose and insulin pump therapy) were recorded. Results: The median age was 14 (5) years, 49.3 % (n=40) of the study group was female and 81.5 % (n=66) of the patients were pubertal. Of the patients, 16.04% had abnormal NCS results. There were no significant differences between patients with normal and abnormal NCS results in terms of demographical features, pubertal stage, disease duration, lipid profiles, and dysglycemia. No significant differences were found between the types of treatment in terms of NCS results. The proximal and distal compound muscle action potential (CMAP) amplitudes of the median nerve were significantly lower in patients with poor glycemic control than in those with well-glycemic control. Sensory nerve action potential (SNAP) amplitudes of sural nerve were significantly lower in patients whose disease durations were ≥60 months than in those &lt;60 months. Conclusions: About a sixth of the T1DM has subclinical neuropathy. CMAP amplitudes of the median nerve are the most affected measurement from poor-glycemic control. Additionally, SNAP amplitudes of the sural nerve are the values most affected by longer disease duration.

Nodopathies in the Early Diagnosis of Axonal Forms of Guillain-Barré Syndrome.

Introduction:Guillain-Barré syndrome (GBS) has been classified into demyelinating and axonal subtypes or forms, such as acute motor axonal neuropathy (AMAN) and regional pharyngeal-cervical-brachial variant (PCBv).ObjectiveTo study the relationship between motor nerve conduction blocks (CBs) and prognosis in AMAN and PCBv.Patients and MethodsWe retrospectively analyzed six cases of AMAN and PCBv with serial nerve conduction studies (NCS) and electromyography (EMG).ResultsThe serial NCS (1st−2nd and 3rd week) showed, as the most constant data, a decreased amplitude of the compound muscle action potential (CMAP) in 100% of cases. CBs were present in 66.6% of cases. EMG (3rd week) showed signs of severe denervation in 33.3%. All patients were treated from the 1st−2nd week of evolution with intravenous immunoglobulins (IVIGs). Patients with CBs (1st−2nd and 3rd week), showed reversible CBs or reversible conduction failure (RCF) and complete recovery at 1 month. Patients without CBs, with persistent reduced distal CMAP amplitude (dCMAP), showed severe acute denervation due to axonal degeneration (3rd week and 1st−3rd month) and a slow recovery of several months.ConclusionsNot all axonal forms of GBS have a poor prognosis. This study of AMAN and PCBv shows that patients with CBs can have reversible CBs or RCF, and good prognosis. Patients without CBs, with persistent reduction of dCMAP amplitude decrement, have severe acute denervation, and a worse prognosis. AMAN and PCBv have a continuous spectrum ranging from CBs due to dysfunction/disruption of Nodes of Ranvier, called nodopathies, with reversible CBs or RCF and good prognosis, to axonal degeneration with worse prognosis.

Temporal Dispersion and Duration of the Distal Compound Muscle Action Potential Do Not Distinguish Diabetic Sensorimotor Polyneuropathy From Chronic Inflammatory Demyelinating Polyneuropathy.

ObjectiveTo investigate the contribution of duration and temporal dispersion (TD) of the distal compound muscle action potential (CMAP) in discriminating chronic inflammatory demyelinating polyneuropathy (CIDP) from diabetic sensorimotor polyneuropathy (DSP) and from CIDP+DSP.MethodsWe performed a retrospective review of patients diagnosed with CIDP, DSP and CIDP+DSP (responsive to immunotherapy) and examined differences in CMAP duration and TD at baseline.ResultsWe included 59 subjects: 17 CIDP, 21 DSP and 21 CIDP+DSP. Of these, 16 (94.1%) CIDP, 18 (85.7%) CIDP+DSP and 1 (4.7%) DSP fulfilled the 2010 EFNS/PNS criteria for definite CIDP. There was no difference in CMAP duration or TD in all nerves (compound outcome) or in individual motor nerves. Patients with CIDP/CIDP+DSP had more conduction blocks, slower conduction velocities and more prolonged F wave latencies than those with DSP.ConclusionMeasures of CMAP duration and TD were not helpful in distinguishing CIDP, DSP or CIDP+DSP patients; however, parameters such as F-wave latencies, conduction blocks or the number of demyelinating parameters were useful in this separation.SignificanceThere are no definite nerve conduction criteria to distinguish patients with CIDP+DSP from DSP alone. Further studies focusing on measures of demyelination may provide stronger evidence to guide treatment decisions in CIDP + DSP patients.

Duration and temporal dispersion measurements in CIDP subjects from the Polyneuropathy And Treatment with Hizentra (PATH) study

Abstract:&#x0D; Introduction: Distal compound muscle action potential (dCMAP) duration and temporal dispersion (TD) are electrophysiological hallmarks of demyelination and important for the diagnosis of CIDP. While the impact of CIDP treatment on other nerve conduction parameters has been examined, the effects on dCMAP and TD remain unexplored. The aim of the study was to examine the impact of withdrawal of immunoglobulin treatment on dCMAP duration and TD, and also the influence of the measurement technique on dCMAP duration and TD.&#x0D; Methods: Nerve conduction studies were analyzed from the PATH (Polyneuropathy And Treatment with Hizentra) study which randomized patients with CIDP to two doses of IgPro 20 and placebo. Distal CMAP duration and TD were obtained by two methods of measurements (D1 and D2, TD1 and TD2) from the median and peroneal nerves. &#x0D; Results: The dCMAP and TD were obtained from 389 tracings. While the two methods of measurement showed differences in D1 and D2 with D2 longer than D1 in all the three groups, there was no difference between the TD1 and TD2. There was no difference at baseline in dCMAP duration or TD among the three groups. At the end of treatment, patients in the placebo arm had no worsening of dCMAP and TD compared to baseline or the treated groups.&#x0D; Conclusion: dCMAP duration and TD did not show a difference between treated and placebo groups, and may be less sensitive measures than other nerve conduction parameters when evaluating changes in treatment. The method of dCMAP duration measurement does not affect TD as long as a consistent method is followed.&#x0D;

Electrophysiological features of acute inflammatory demyelinating polyneuropathy associated with SARS-CoV-2 infection

ObjectiveTo assess whether patients with acute inflammatory demyelinating polyneuropathy (AIDP) associated with SARS-CoV-2 show characteristic electrophysiological features.MethodsClinical and electrophysiological findings of 24 patients with SARS-CoV-2 infection and AIDP (S-AIDP) and of 48 control AIDP (C-AIDP) without SARS-CoV-2 infection were compared.ResultsS-AIDP patients more frequently developed respiratory failure (83.3% vs. 25%, P = 0.000) and required intensive care unit (ICU) hospitalization (58.3% vs. 31.3%, P = 0.000). In C-AIDP, distal motor latencies (DMLs) were more frequently prolonged (70.9% vs. 26.2%, P = 0.000) whereas in S-AIDP distal compound muscle action potential (dCMAP) durations were more frequently increased (49.5% vs. 32.4%, P = 0.002) and F waves were more often absent (45.6% vs. 31.8%, P = 0.011). Presence of nerves with increased dCMAP duration and normal or slightly prolonged DML was elevenfold higher in S-AIDP (31.1% vs. 2.8%, P = 0.000);11 S-AIDP patients showed this pattern in 2 nerves.ConclusionIncreased dCMAP duration, thought to be a marker of acquired demyelination, can also be oserved in critical illness myopathy. In S-AIDP patients, an increased dCMAP duration dissociated from prolonged DML, suggests additional muscle fiber conduction slowing, possibly due to a COVID-19-related hyperinflammatory state. Absent F waves, at least in some S-AIDP patients, may reflect α-motor neuron hypoexcitability because of immobilization during the ICU stay. These features should be considered in the electrodiagnosis of SARS-CoV-2 patients with weakness, to avoid misdiagnosis.

Analysis of compound muscle action potential in patients with chronic inflammatory demyelinating polyneuropathy and Charcot-Marie-Tooth disease type 1A

Objective: To provide an additional contribution to the differential diagnosis of Charcot-Marie-Tooth disease type 1A (CMT1A) and chronic inflammatory demyelinating polyneuropathy (CIDP) by analyzing distal duration and proximal/distal amplitude and duration ratios on different nerves in these diseases that show demyelinating peripheral neuropathy features.&#x0D; Material and Methods: We retrospectively reviewed the electromyography (EMG) findings of patients aged 18-80 years who were followed up with a diagnosis of acquired and hereditary demyelinating type polyneuropathy in the neuromuscular diseases outpatient clinic in our center. We analyzed the distal CMAP duration and amplitude, proximal and distal compound muscle action potential, and duration ratios on each nerve in the patient groups, separately.&#x0D; Results: The CIDP group had significantly longer Peroneal nerve distal duration than the CMT1A group (p=0.04). Median, ulnar, and tibial nerve distal durations were similar between the groups (p=0.84, p=0.86, and p=0.13, respectively). The median nerve, ulnar nerve, and peroneal nerve proximal/distal amplitude ratios were not different between the CMT1A and CIDP groups (p=0.99, p=0.38, and p=0.16, respectively). The tibial nerve proximal/distal amplitude ratio in the CIDP group was lower than in the CMT1A group (p=0.003). Median, ulnar, peroneal, and tibial nerve proximal/distal duration ratios were statistically similar among the groups (p=0.21, p=0.66, p=0.62, and p=0.46, respectively).&#x0D; Conclusion: This study may help to improve the management of challenging patients where there is an overlap between hereditary and inflammatory neuropathies. The different electrodiagnostic models of various acquired and hereditary demyelinating polyneuropathies should be clinically recognized.

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.

Antibody- and macrophage-mediated segmental demyelination in chronic inflammatory demyelinating polyneuropathy: clinical, electrophysiological, immunological and pathological correlates.

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a heterogeneous autoimmune disorder critically lacking diagnostic biomarkers. Autoantibodies to nodal and paranodal components have recently been described in a small subset of patients. Here, the diagnostic value of immune reactivity toward the myelin compartment was investigated. Ninety-four French CIDP patients were retrospectively studied. The reactivity toward the peripheral nerve was investigated. Sural nerve biopsies were examined by electron microscopy and immunofluorescence. Twenty-one patients (22%) and three patients (3%) presented with a strong immunoglobulin G or immunoglobulin M reactivity respectively against the myelin compartment. The clinical, electrophysiological and morphological features were examined in nine of these patients for whom sural nerve biopsies were available. Seven patients were electrodiagnosed with definite CIDP, one with possible CIDP and one was unclassifiable but sural nerve biopsy argued for CIDP diagnosis. Electron microscopy of sural nerve biopsies demonstrated the presence of macrophage-mediated demyelination restricted to the internode in all nine patients. Immunolabelling for voltage-gated sodium channels, myelin and axonal markers confirmed the presence of segmental demyelination and of remyelination. The nodal and paranodal regions, however, were unaffected in these patients. Nerve conduction studies corroborated the multifocal and segmental profile, and seven patients showed increased duration of proximal (1.5-5.1 times) and/or distal (1.2-3.4 times) compound muscle action potential in at least two nerves. Antibody- and macrophage-mediated demyelination appears responsible for conduction alterations in CIDP patients and nerve immunostaining assays may serve as a supportive diagnostic biomarker.

O-34 Hereditary or inflammatory childhood neuropathy – Electrophysiological abnormalities helpful in the differentiation

Background The differentiation between hereditary neuropathy and chronic inflammatory demyelinating polyneuropathy (CIDP) in children is especially significant because of completely different treatment possibilities and prognosis in these conditions. The aim of the study was to compare electrophysiological abnormalities in a group of children and young adults with demyelinating neuropathy of chronic or subacute onset. Material and methods Retrospective analysis of clinical and nerve conduction study (NCS) data included 3 children and 4 young adults with Charcot-Marie-Tooth Neuropathy X type 1 (CMTX1), 24 children with Charcot-Marie-Tooth Neuropathy type 1a (CMT1a), 8 with hereditary neuropathy with pressure palsy (HNPP) and 18 children with CIDP. Results In our study 6/7 CMTX1 had both axonal and demyelinating changes in NCS study. The AAN and EFNS electrophysiological CIDP criteria were fulfilled in 2/7 CMTX1, 23/24 CMT1a, 4/8 HNPP and 17/18 CIDP patients. Additionally 3 patients with CMTX1 are classified with EFNS criteria as “probable/possible CIDP”. A distal compound muscle action potential (dCMAP) was >9 ms in all CMT1a and 14/18 CIDP patients but none with CMTX1 nor HNPP. Abnormal median/normal sural SNAP (AMNS) or while abnormal sural/normal median SNAP (ASNM) parameter and a difference between conduction velocities (CV) of two corresponding nerves > 10 m/s were not observed in any CMT1a patient. Conclusion Our study has showed that presented above electrophysiological parameters are useful in differentiation between these neuropathies.

Electrodiagnostic data-driven clustering identifies a prognostically different subgroup of patients with chronic inflammatory demyelinating polyneuropathy

ObjectiveThis study aimed to explore the correlations between electrodiagnostic (EDX) features in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and to investigate whether EDX data-driven clustering can identify a distinct...

Electrophysiological demyelinating features in hereditary ATTR amyloidosis

Objective: To elucidate the electrophysiological demyelinating features in patients with hereditary ATTR amyloidosis that may lead to a misdiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP).Methods: In 102 patients with hereditary ATTR amyloidosis (85 Val30Met and 17 non-Val30Met; 37 and 65 from endemic and non-endemic areas, respectively), results of motor nerve conduction studies (MNCSs) with a 2-Hz low-cut filter in the unilateral ulnar and tibial nerves were retrospectively investigated to assess whether each MNCS parameter demonstrated demyelinating features that fulfil the European Federation of Neurological Societies/Peripheral Nerve Society electrodiagnostic (EFNS/PNS EDX) criteria for CIDP.Results: Thirteen patients with low compound muscle action potential (CMAP) amplitude in the tibial nerve (0.7 ± 0.7 mV) and prolonged distal CMAP duration in the ulnar nerve satisfied the definite EFNS/PNS EDX criteria for CIDP. Abnormal temporal dispersion and prolongation of distal latency in the tibial nerve were observed in 5 of 13 patients. However, only one of the 13 patients presented with the reduction of motor conduction velocity in each nerve. No patient exhibited conduction block in any nerve.Conclusion: Patients with hereditary ATTR amyloidosis occasionally show electrophysiological demyelinating features without conduction block following severe axonal degeneration.