Sensory Nerve Action Potential Amplitude Research Articles

Clinical features of Guillain-Barré syndrome with anti-neurofascin 155 antibody.

Anti-neurofascin 155 (NF155) antibody has been discovered in chronic demyelinating conditions. However, the positive rate and clinical description were insufficient in acute demyelinating conditions, such as Guillain-Barré syndrome (GBS). This study aimed to explore the positive rate of anti-NF155 antibody in GBS patients and determine whether there were unique clinical characteristics in these patients. Serum anti-NF155 antibody was detected from 94 GBS patients and 50 sex- and age-matched healthy controls using cell-based assay and tissue-based assay with immunostaining of mouse teased sciatic nerve fibers. Clinical characteristics, laboratory data, and electrophysiology examinations were retrospectively collected. Seven of 94 (7.45%) GBS patients were positive for anti-NF155 antibody, and the main IgG subclass was IgG1. Compared with anti-NF155 antibody-negative GBS patients, anti-NF155 antibody-positive GBS patients had a higher GBS disability score at nadirs (p=.010), higher modified Erasmus GBS outcome score (p=.022), higher rate of abnormal compound motor action potential (CMAP) amplitude (p=.002), higher frequency of prolonged F-wave latency (p < .001), lower frequency of abnormal sensory conduction velocity (p < .001) and sensory nerve action potential amplitude (p < .001), more axonal type (p=.040), and poorer therapeutic effect (p=.017). Anti-NF155 antibody exists in a small portion of GBS patients. Anti-NF155 antibody-positive GBS patients possibly have a more severe clinical course, less sensory nerves involved, higher proportion of axonal type, poorer therapeutic effect, and worse prognosis, but the pathogenicity of the anti-NF155 antibody in GBS needs further study.

Nerve Conduction Studies of Dorsal Sural Nerve: Normative Data and Its Potential Application in ATTRv Pre-Symptomatic Subjects.

The objective of the study is to provide age-related normative values for dorsal sural nerve (DSN) and to analyse its application during follow-up of hereditary transthyretin amyloidosis (ATTRv) pre-symptomatic subjects. We consecutively recruited ATTRv pre-symptomatic carriers in which clinical examination, cardiological evaluation, and nerve conduction studies of the sural nerve and DSN were performed. To provide normative data of DSN, neurophysiologic parameters from healthy controls referred to our service were entered into linear regression analyses to check the relative influence of age and height. A correction grid was then derived. We collected 231 healthy subjects: the mean DSN sensory nerve action potential (SNAP) amplitude was 9.99 ± 5.48 μV; the mean conduction velocity was 49.01 ± 5.31 m/s. Significant correlations were found between age and height with DSN SNAP amplitude. Fifteen ATTRv pre-symptomatic carriers were examined. Sural nerve NCS were normal in 12/15 and revealed low/borderline values in three subjects. Considering our correction grid, we found an abnormal DNS amplitude in 9/15 subjects and low/borderline values in 2/15. In ATTRv, early detection of peripheral nerve damage is crucial to start a disease-modifying treatment. DSN may be easily and reliably included in the routine neurophysiological follow-up of ATTRv pre-symptomatic subjects.

Clinical and electrophysiological findings in C9ORF72 ALS.

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal, neurodegenerative disorder of motor neurons in which the cause is mostly unknown. Early identification of genetic ALS cases, of which C9ORF72 (C9ALS) is the most frequent, can have important implications for evaluation, prognosis, and therapeutics. Here, we aimed to characterize the clinical and electrophysiological hallmarks of C9ALS and investigate differences from C9ORF72 negative ALS (non-C9ALS). We retrospectively reviewed clinical and electrodiagnostic (EDX) data for all genetically confirmed C9ALS cases seen between 1/1/2012 and 10/1/2020 who met Gold Coast criteria and compared them 1:1 with non-C9ALS patients within the same time frame. A total of 99 C9ALS and 99 non-C9ALS cases were identified. Compared to non-C9ALS, C9ALS demonstrated higher prevalence in women, lesser racial variability, stronger family history of ALS, and higher frequency of upper motor neuron signs. EDX testing of C9ALS showed higher median sensory nerve and lower fibular compound muscle action potential amplitudes. Although the differences between C9ALS and non-C9ALS reached statistical significance in certain nerve conduction parameters, they were not sufficient to discriminate between groups on a case-by-case basis. Genetic testing is required to identify C9ALS patients.

Formulated Curcumin Prevents Paclitaxel-Induced Peripheral Neuropathy through Reduction in Neuroinflammation by Modulation of α7 Nicotinic Acetylcholine Receptors

Paclitaxel is widely used in the treatment of various types of solid malignancies. Paclitaxel-induced peripheral neuropathy (PIPN) is often characterized by burning pain, cold, and mechanical allodynia in patients. Currently, specific pharmacological treatments against PIPN are lacking. Curcumin, a polyphenol of Curcuma longa, shows antioxidant, anti-inflammatory, and neuroprotective effects and has recently shown efficacy in the mitigation of various peripheral neuropathies. Here, we tested, for the first time, the therapeutic effect of 1.5% dietary curcumin and Meriva (a lecithin formulation of curcumin) in preventing the development of PIPN in C57BL/6J mice. Curcumin or Meriva treatment was initiated one week before injection of paclitaxel and continued throughout the study (21 days). Mechanical and cold sensitivity as well as locomotion/motivation were tested by the von Frey, acetone, and wheel-running tests, respectively. Additionally, sensory-nerve-action-potential (SNAP) amplitude by caudal-nerve electrical stimulation, electronic microscopy of the sciatic nerve, and inflammatory-protein quantification in DRG and the spinal cord were measured. Interestingly, a higher concentration of curcumin was observed in the spinal cord with the Meriva diet than the curcumin diet. Our results showed that paclitaxel-induced mechanical hypersensitivity was partially prevented by the curcumin diet but completely prevented by Meriva. Both the urcumin diet and the Meriva diet completely prevented cold hypersensitivity, the reduction in SNAP amplitude and reduced mitochondrial pathology in sciatic nerves observed in paclitaxel-treated mice. Paclitaxel-induced inflammation in the spinal cord was also prevented by the Meriva diet. In addition, an increase in α7 nAChRs mRNA, known for its anti-inflammatory effects, was also observed in the spinal cord with the Meriva diet in paclitaxel-treated mice. The use of the α7 nAChR antagonist and α7 nAChR KO mice showed, for the first time in vivo, that the anti-inflammatory effects of curcumin in peripheral neuropathy were mediated by these receptors. The results presented in this study represent an important advance in the understanding of the mechanism of action of curcumin in vivo. Taken together, our results show the therapeutic potential of curcumin in preventing the development of PIPN and further confirms the role of α7 nAChRs in the anti-inflammatory effects of curcumin.

A novel method to measure sensory nerve conduction of the posterior antebrachial cutaneous nerve.

Posterior antebrachial cutaneous (PABC) nerve conduction studies could be useful for distinguishing PABC neuropathy from C7 radiculopathy. In the conventional method using an antidromic method, the sensory nerve action potential (SNAP) is sometimes followed by a large volume-conducted motor potential. In this report we describe a reliable nerve conduction study using an orthodromic method for recording SNAPs of the PABC nerve. Thirty-six healthy volunteers participated in this study. PABC SNAPs were recorded by placing a surface-active electrode 2cm anterior to the lateral epicondyle. The PABC nerve was stimulated 10cm distal to the active recording electrode along a line from the recording point to the mid-dorsum of the wrist, midway between the radial and ulnar styloid processes. We also performed PABC nerve conduction studies using an antidromic method and compared the findings. PABC SNAPs were recorded bilaterally from all subjects. The mean peak-to-peak amplitude for SNAPs was 13.4± 4.8μV. Mean maximum conduction velocity was 62.7± 3.9m/s and mean negative peak conduction velocity was 51.2± 2.6m/s. The mean side-to-side difference in amplitude was 22.1± 16.0%. The mean amplitude of SNAPs obtained by our method was 48.9% higher than that of SNAPs obtained by the conventional method (13.4 vs 9.0 μV; P < .001). In contrast to the conventional method, our method enabled SNAPs to be recorded without a volume-conducted motor potential. The higher mean amplitude of SNAPs with our method enables them to be obtained easily.

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.

Implications of median sensory study to the thumb and deltoid/biceps motor unit recruitment on identifying C6 root avulsion in upper neonatal brachial plexus palsy.

Anatomic representation suggests that a median sensory nerve conduction study recording the thumb (median D1 NCS) may effectively assess upper neonatal brachial plexus palsy (NBPP). We sought to determine the feasibility of technique, establish reference data, and assess its ability to: (a) identify focal upper plexus lesions; and (b) identify C6 root avulsion. In a secondary analysis, we explored the association between absence/presence of motor unit action potentials (MUAPs) during needle electromyography (EMG) of the deltoid and biceps brachii muscles and C6 avulsion status. A retrospective chart review was performed of surgical patients with severe upper NBPP who ultimately underwent surgical reconstruction (between 2017 and 2020). Median D1 sensory nerve action potential (SNAP) amplitude ranges were determined in affected and contralateral limbs and analyzed by C6 root avulsion status. Also, presence/absence of MUAPs during EMG of the deltoid and biceps brachii was compared between C6 avulsion patients and controls. Thirty-eight patients were included in our analysis. A median D1 NCS study was readily performed, showing a contralateral limb mean amplitude of 27.42 μV (range, 3.8-54.7μV). Most patients had a low ipsilateral median D1 SNAP amplitude, regardless of C6 avulsion status. Detectable MUAPs in either deltoid or biceps brachii on EMG were atypical in C6 root avulsion. The median D1 NCS identifies upper NBPP, but does not distinguish C6 avulsions from post-ganglionic lesions, likely due to the frequent co-occurrence of post-ganglionic axonal disruption. The presence of MUAPs on deltoid/biceps brachii EMG suggests C6 avulsion is unlikely.

The supraclavicular nerve.

The aim of this study was to describe a new method for studying the supraclavicular nerve (SCN) conduction and to report four cases with SCN lesions. The SCN was antidromically recorded with a pair of self-adhesive electrodes located in the middle of the clavicle. Stimulation (<5mA) was delivered 7cm proximally with a bar electrode. To facilitate recording, it was explained to the participant that they would feel a very faint electrical sensation locally and an electrical tingle upward (ear) or downward (shoulder/clavicle). Each participant was asked to say when the tingling moved downward. In normal subjects, median values were 16 μV (range: 9-33) for sensory nerve action potential (SNAP) amplitude; 1.2ms (range: 1-1.5) for onset latency; and 1.25 (range: 1-1.7) for side-to-side amplitude ratio. In the four patients, the SCN SNAP was absent on the pathological side and normal on the healthy side. All four patients complained of unilateral neuropathic hypoesthesia on the anterior aspect of the neck, chest, and shoulder that occurred after radical neck surgery for thyroid or larynx cancer (x3) and first rib resection (x1). A comparison with previous reports shows that this simple method provides similar or highest SNAP amplitudes. SCN lesions are rare, and rarely referred for electrodiagnosis, and often overlooked. However, the SCN conduction study, which causes very slight inconvenience (low-intensity stimulation), allows a better understanding of the origin of the complaints and permits the patient to benefit of more suitable treatment.

Different patterns of sensory nerve involvement in chronic inflammatory demyelinating polyneuropathy subtypes.

Among subtypes of chronic inflammatory demyelinating polyneuropathy (CIDP), different immune pathophysiologies have been proposed. In this study, sensory nerve conduction studies were compared among clinical subtypes to attempt to better understand the underlying pathophysiology. A total of 138 patients with CIDP was classified into clinical subtypes: typical CIDP (N=68), multifocal CIDP (N=27), or other (N=2). Patients with immunoglobulin M (IgM) neuropathy anti-myelin-associated glycoprotein neuropathy (MAG; N=19) were also included as disease controls. Sensory nerve action potentials (SNAPs) were recorded in the median, ulnar, and superficial radial and sural nerves. SNAP amplitudes (P < .05) and conduction velocities (P < .01) in the median nerve and conduction velocities (P < .05) in the ulnar nerve were lower in typical CIDP than in multifocal CIDP, whereas those in the radial and sural nerves were comparable in each group. Low median and normal sural SNAP amplitudes were more common in typical CIDP (P < .005) than in multifocal CIDP, suggesting predominant involvement at terminal portions of the nerves. Terminal portions of sensory nerves are preferentially affected in typical CIDP compared with multifocal CIDP. These findings might be partially explained by the hypothesis of antibody-mediated demyelination in typical CIDP at the regions where the blood-nerve barrier is anatomically deficient, whereas multifocal CIDP predominantly affects the nerve trunks, largely due to cell-mediated demyelination, with disruption of the blood-nerve barrier.

Genetic evidence for the most common risk factors for chronic axonal polyneuropathy in the general population.

Background and purposeChronic axonal polyneuropathy is a common disease, but the etiology remains only partially understood. Previous etiologic studies have identified clinical risk factors, but genetic evidence supporting causality between these factors and polyneuropathy are largely lacking. In this study, we investigate whether there is a genetic association of clinically established important risk factors (diabetes, body mass index [BMI], vitamin B12 levels, and alcohol intake) with chronic axonal polyneuropathy.MethodsThis study was performed within the population‐based Rotterdam Study and included 1565 participants (median age = 73.6 years, interquartile range = 64.6–78.8, 53.5% female), of whom 215 participants (13.7%) had polyneuropathy. Polygenic scores (PGSs) for diabetes, BMI, vitamin B12 levels, and alcohol intake were calculated at multiple significance thresholds based on published genome‐wide association studies.ResultsHigher PGSs of diabetes, BMI, and alcohol intake were associated with higher prevalence of chronic axonal polyneuropathy, whereas higher PGS of vitamin B12 levels was associated with lower prevalence of polyneuropathy. These effects were most pronounced for PGSs with lenient significance thresholds for diabetes and BMI (odds ratio [OR]diabetes, p < 1.0 = 1.21, 95% confidence interval [CI] = 1.05–1.39 and ORBMI, p < 1.0 = 1.21, 95% CI = 1.04–1.41) and for the strictest significance thresholds for vitamin B12 level and alcohol intake (OR vitamin B12, p < 5e‐6 = 0.79, 95% CI = 0.68–0.92 and ORalcohol, p < 5e‐8 = 1.17, 95% CI = 1.02–1.35). We did not find an association between different PGSs and sural sensory nerve action potential amplitude, nor between individual lead variants of PGS p < 5e‐8 and polyneuropathy.ConclusionsThis study provides evidence for polygenic associations of diabetes, BMI, vitamin B12 level, and alcohol intake with chronic axonal polyneuropathy. This supports the hypothesis of causal associations between well‐known clinical risk factors and polyneuropathy.

NERVE CONDUCTION STUDIES IN ASYMPTOMATIC HIV POSITIVE PERSONS

Background: Nerve Conduction Studies were performed in asymptomatic HIV positive persons and corresponding controls to detect subclinical peripheral nervous system involvement in early stage of HIV. Aims &amp; Objective: To perform Nerve Conduction Studies in asymptomatic HIV positive persons and corresponding controls. Material and Methods: In this study,100 participants in the age group 25-45 years were selected. In study group, 50 3 participants who were HIV positive and asymptomatic (CD4 count &gt; 350 cells/mm ) and were not on Anti Retro Viral Treatment (ART),were included.In control group 50 healthy age matched HIV negative participants were included.We performed Nerve Conduction Studies in these participants. For motor nerves, Distal Latency (DL), Motor Nerve Conduction Velocity (MNCV), Compound Muscle Action Potential (CMAP) amplitude were measured and for sensory nerves Onset Latency (OL), Sensory Nerve Conduction Velocity (SNCV) and Sensory Nerve Action Potential (SNAP) amplitude were measured. Results: Nerve Conduction Studies in asymptomatic HIV revealed that,MNCV was significantly decreased for median motor nerve and tibial motor nerve in study group compared to control group, SNAP was significantly reduced for median sensory nerve in study group compared to control group,OL was significantly prolonged for sural nerve in study group than control group and SNCV was significantly decreased for sural nerve in study group than control group. Conclusion: Nerve Conduction Studies in asymptomatic HIV positive persons suggests subclinical peripheral nervous system involvement in early stages of HIV. Hence Nerve Conduction Studies can be important to detect subclinical peripheral nervous system involvement in the early stages of HIV.

Medial Plantar Sensory Nerve Action Potential: A Study for Reference Data in Indian Subjects.

Context:The medial plantar nerve (MP) sensory nerve action potential (SNAP) has been shown to be a sensitive indicator for detecting a length-dependent axonal peripheral neuropathy. However, literature survey shows paucity of age stratified data. This study was undertaken to obtain age stratified reference data for MP SNAP amplitude and latency.Aim:To establish age-stratified reference data in Indian subjects for the MP SNAP.Study Setting and Design:The study was conducted in the electrodiagnostic laboratory of a tertiary city hospital and is retrospective study.Materials and Methods:A retrospective study was conducted using the nerve conduction study reports of 173 patients with only upper limb symptoms and findings. Patients were between the ages of 18 and 86 years, stratified into six groups, a = 18-30 years, b = 31- 40 years, c = 41-50 years, d = 51- 60 years, e = 61-70 years, f ≥70 years.Statistical Methods:Stata 12.1 statistical program was used. Lower limit of the SNAP amplitude was obtained using mean-2SD of transformed data. Analysis of variance defined the intergroup variability, linear regression and Pearson's correlation assessed the statistical significance.Results:The lower limit of normal MP SNAP amplitude for each age group is as follows: a: 8.7uv b: 7.5uv c: 3.7 uv d: 2.9uv e: 2.0 uv f: 1.4uv. The amplitude difference between the groups b & c, c & d and e and f using analysis of variance with Bonferroni correction and Tukey post-hoc test was not significant, but the other groups showed statistically significant variance. The equation of regression for the predicted amplitude value with age was defined as Y^ = {3.5 + age (-.0233) – 2 (0.389)}3.Conclusion:This study provides age stratified reference data for MP SNAP. There is evidence to suggest that MP SNAP amplitude varies with age hence age stratified data should be used to define abnormality.

Influence of age and gender in the sensory nerve fibers excitability.

ObjectivesTo assess the influence of age and gender on sensory nerve axonal excitability parameters.MethodsThirty‐three healthy subjects (21 women) were included, with a mean age of 34.6 (range 21–76). Median sensory nerve excitability measurements (index finger) were performed using the TRONDNF nerve excitability protocol of the QTRAC program.ResultsPeak sensory nerve action potential (SNAP) amplitude was significantly higher among women (27.1 vs. 9.2 μV; p = .022), and strength–duration time constant (SDTC) was significantly higher in men (0.7 vs. 0.5; p = .011), not dependent on age. Greater age was negatively correlated with resting I/V slope, not dependent on gender (r = –0.4; p = .024). No other changes in excitability properties with increasing age were found.ConclusionsPhysiological features like as age and gender do not have a relevant impact on sensory nerve excitability measurements, which can have implications regarding pharmacological treatments.

When is needle examination of thenar muscle necessary in the evaluation of mild and moderate carpal tunnel syndrome?

Objectives This study aims to evaluate the predictors of standard nerve conduction study (NCS) parameters in determining the presence of axonal loss by means of spontaneous activity in patients with mild and moderate carpal tunnel syndrome (CTS). Patients and methods Between May 2015 and April 2018, a total of 118 patients (11 males, 107 females; mean age: 52.3±10.6 years; range, 27 to 79 years) who underwent electrophysiological studies and were diagnosed with CTS were included. Demographic data of the patients including age, sex, and symptom duration were recorded. Electrodiagnostic studies were performed in all patients. All the needle electromyography (EMG) findings were recorded, but only the presence or absence of spontaneous EMG activities was used as the indicator of axonal injury. Results In 37 (31.4%) of the patients, spontaneous activity was detected at the thenar muscle needle EMG. No spontaneous activity was observed in any of 43 (36.4%) patients with normal distal motor latency (DML). There were significant differences in DMLs, compound muscle action potential (CMAP) amplitudes, sensory nerve action potentials amplitudes, and sensory nerve conduction velocities between the groups with and without spontaneous activity (p<0.05). The multiple logistic regression analysis revealed that DML was a significant independent risk variable in determining presence of spontaneous activity. The most optimal cut-off value for median DML was calculated as 4.9 ms. If the median DML was >4.9 ms, the relative risk of finding spontaneous activity on thenar muscle needle EMG was 13.5 (95% CI: 3.6-51.2). Conclusion Distal motor latency is the main parameter for predicting the presence of spontaneous activity in mild and moderate CTS patients with normal CMAP. Performing needle EMG of the thenar muscle in CTS patients with a DML of >4.9 ms may be beneficial to detect axonal degeneration in early stages.

Variable differences of nerve conduction amplitudes versus velocities and distal latencies of healthy subjects assessed in ethnic cohorts.

The variables affecting reference compound muscle (CMAP) and sensory nerve action potential (SNAP) amplitudes as compared to ones affecting conduction velocities and DLs have not been adequately evaluated in previous studies. In this report, this subject is studied in healthy subject cohorts mainly of Northern European extraction, Northern Plains Indians, and Latinos. Nineteen variables and 18 attributes of nerve conductions (NCs) were assessed using highly standard testing conditions and techniques. Classification and Regression Tree analyses were used to assess variable differences among amplitudes, conduction velocities, and DLs. The most important variable affecting CMAP and SNAP amplitudes was age. For conduction velocities (CVs) and DLs, the variables were height, ethnic cohort, and age. The variables affecting attributes of NCs were similar for the three ethnic cohorts evaluated. The differences of variables affecting amplitudes compared to CVs and DLs need to be taken into account in interpretation of NC results and in setting reference limits for use in medical practice, epidemiology surveys, and therapeutic trials. Scores of CMAP and SNAP amplitudes are suitable measures of sensorimotor polyneuropathy severity, whereas conduction velocities and DLs reflect physiologic/pathologic abnormality of nerve fibers.

Enhanced sensory conduction in primary fibromyalgia: a case\u2013control pilot study

BackgroundThis study aimed to test the changes in the conduction properties of peripheral nerves in patients with primary fibromyalgia (FM). Thirty patients with FM and sixteen healthy controls participated in this study. Visual analogue scale (VAS) for pain severity, pain duration, Widespread Pain Index (WPI), Symptom Severity (SS) scale, Hamilton depression rating scale, Taylor’s manifest anxiety scale, and Fibromyalgia Impact Questionnaire (FIQR) were used for measurement of psychiatric comorbidities and quality of life for each patient. Routine motor and sensory nerve conduction studies of both median, ulnar, common peroneal, posterior tibial, and sural nerves were measured for all study participants.ResultsWe found statistically significant increase in Sensory Conduction Velocity (SCV), Sensory Nerve Action Potential (SNAP) amplitude, and decrease in Sensory Latency (SL) in patients with FM compared to controls. There were no significant changes in motor nerve conduction between patients and controls. Regression analysis showed a significant relation between WPI and both SCV and SL especially in nerves of upper limbs. However, no significant relation between SCV and SL and other presumed predictors including VAS for pain severity, pain duration, SS scale, FIQR, and psychiatric comorbidities. Patients with FM suffered more depression and anxiety than controls.ConclusionsWe found enhanced conductivity of the sensory rather than the motor nerves in patients with FM. To our knowledge, this is the first study to describe these sensory changes which may add further evidence of peripheral sensitization in patients with FM.

Age-related sensory neuropathy in patients with spinal muscular atrophy type 1.

Spinal muscular atrophy type 1 (SMA 1) is a devastating motor neuron disorder that leads to progressive muscle weakness, respiratory failure and premature death. Although sensory electrophysiological changes have been anecdotally found in pediatric SMA 1 patients, the age of onset of sensory neuropathy remains unknown. Sensory nerve conduction studies of the median and sural nerves were performed in 28 consecutive SMA 1 patients of different ages. Sensory nerve conduction velocities and sensory nerve action potential (SNAP) amplitudes recorded in these patients were compared with those obtained from 93 healthy subjects stratified by age. SNAP amplitudes decreased with increasing age in the sural and median nerves, without any significant difference between upper and lower limbs. Our data suggest that sural and median nerve SNAP amplitudes are normal in younger patients, while an axonal neuropathy appears in older ones.

Variability in electrodiagnostic findings associated with neurogenic thoracic outlet syndrome.

Introduction/AimsNeurogenic thoracic outlet syndrome (NTOS) is a heterogeneous and often disputed entity. An electrodiagnostic pattern of T1 > C8 axon involvement is considered characteristic for the diagnosis of NTOS. However, since the advent of high‐resolution nerve ultrasound (US) imaging, we have encountered several patients with a proven entrapment of the lower brachial plexus who showed a different, variable electrodiagnostic pattern.MethodsIn this retrospective case series, 14 patients with an NTOS diagnosis with a verified source of compression of the lower brachial plexus and abnormal findings on their electrodiagnostic testing were included. Their medical records were reviewed to obtain clinical, imaging, and electrodiagnostic data.ResultsSeven patients showed results consistent with the “classic” T1 axon > C8 pattern of involvement. Less typical findings included equally severe involvement of T1 and C8 axons, more severe C8 involvement, pure motor abnormalities, neurogenic changes on needle electromyography in the flexor carpi radialis and biceps brachii muscles, and one patient with an abnormal sensory nerve action potential (SNAP) amplitude for the median sensory response recorded from the third digit. Patients with atypical findings on electrodiagnostic testing underwent nerve imaging more often compared to patients with classic findings (seven of seven patients vs. five of seven respectively), especially nerve ultrasound.DiscussionWhen there is a clinical suspicion of NTOS, an electrodiagnostic finding other than the classic T1 > C8 pattern of involvement does not rule out the diagnosis. High resolution nerve imaging is valuable to diagnose additional patients with this treatable condition.

Normal reference value of orthodromic and antidromic sensory nerve conduction velocity of median nerve with intact palmaris longus tendon in apparently healthy individuals

The aim of this study was to determine normative electrophysiological reference values of median sensory nerve conduction studies among security guards with the palmaris longus tendon (PLT). Sensory nerve conduction studies of the median nerve using antidromic and orthodromic methods were conducted in the upper limbs of 101 healthy male security guards between the ages of 21 and 42 years. The presence of the PLT was recorded in both hands using a standard test. A scatter plot was used to determine the correlation between different parameters using the ortho and antidromic methods. The mean age (years), weight (kg), height (cm), and BMI (kg/m2) were 28.77±5.14, 70.53±11.28, 171.71±7.12, and 23.91±3.45, respectively. In the median nerve (sensory) by antidromic method, the mean distal latency (DL) was 2.65±0.33ms and 2.64±0.37, SNCV (sensory nerve conduction velocity) was 53.45±5.28m/s and 53.84±5.68 and the amplitude was 27.33±12.38µV and 29.41±12.97 in the left- and right-hand wrist, respectively. By orthodromic method the DL was 2.54±0.53ms and 2.51±0.44, SNCV was 55.93±6.09m/s and 55.93±5.24 and the sensory nerve action potential amplitude was 12.00±8.82µV and 11.72±6.24 in the left and right hand, respectively. Spearman correlations were used to determine the variables influenced by hand sidedness. The normative reference parameters of sensory nerve conduction velocity of the median nerve were established by both methods using a standardized technique.

WS4.3. Overview of Axonal Excitability Studies

Nerve excitability testing is a non-invasive neurophysiological technique, which investigates nerve functions in vivo . While nerve conduction studies deliver supramaximal stimuli to measure conduction velocities and the number of large myelinated fibres, nerve excitability studies use weaker stimuli and measure strength of stimuli, which evoke target compound muscle action potential or sensory nerve action potential amplitudes. The combination of conditioning and test stimuli, with various strength and duration, can examine functions of various types of ion channels and ion pumps and exchangers, which are located in peripheral nerve axons, and membrane potential. Several paradigms, such as strength-duration properties, threshold electrotonus, current-threshold relationship and recovery cycle, are assessed in this testing, and alterations of parameters in these paradigms indicate changes in those functions. This technique has disclosed various pathophysiological alterations mainly in genetic and acquired channelopathies. A famous study, using this technique, disclosed an effect of puffer fish poisoning for nerve excitability. Tetrodotoxin is known to block sodium channels, and salient reductions of strength-duration time constant and refractoriness in recovery cycle, makers of persistent and transient sodium channel functions, respectively, were disclosed in patients with tetrodotoxin intoxation. This study firstly visualized an effect of tetrodotoxin for the human peripheral nerve. In another study, increased strength-duration time constant, i.e. increased excitability, was revealed in patients with neuropathic pain and muscle cramps. Mexiletine treatment, a sodium channel blocker, for these patients relieved those symptoms and decreased strength-duration time constant. As those studies, recent studies, using this testing, have disclosed an impact of altered ion channel functions for neurological diseases and utility of this technique as a treatment biomarker. In this session, I plan to introduce the principle of this testing and recent advances in clarification of pathophysiology in neurological diseases and treatment developments, using this testing.