Sensory Nerve Action Research Articles

A Young Man With Acute-Onset Bilateral Arm Weakness After Traumatic Sciatic Neuropathy: A Clinical Vignette.

A Young Man With Acute-Onset Bilateral Arm Weakness After Traumatic Sciatic Neuropathy: A Clinical Vignette.

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 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.

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.

Characterization of the Sensory Nerve Action Potential of the Sural Nerve in Patients Over 60 Years of Age without Peripheral Neuropathy

ABSTRACT Demonstration of the possibility to obtain the sensory nerve action potential (SNAP) of sural nerve in patients over 60 years old, without peripheral neuropathy. Prospective study on 101 patients older than 60 years of age. Stimulation was applied 12 cm proximal to the recording point. Two hundred and two SNAPs of the sural nerve were collected with an average peak latency of 3.2 ms, onset latency of 2.6 ms, peak-to-peak amplitude of 15.2 μV and velocity of 45.7 m/s. It was possible to obtain the sural nerve SNAP in all tested patients older than 60, without peripheral neuropathy. The values obtained in this study prove to be useful as a reference in the evaluation of patients older than 60 years of age.

Peripheral neuropathy in severe iron deficiency anemia: A case report

Anemia is a global health problem that need medical attention. Iron deficiency anemia (IDA), in particular is the most common nutritional deficiency anemia prevalent in India. Iron essential for effective myelination of peripheral nervous system.1 Nerve conduction studies are one of the neurophysiological investigations that can quantitatively detect peripheral nerve dysfunction.2 In this case report, we present findings of nerve conduction studies performed on a case of severe iron deficiency anemia and the associated peripheral neurodeficit observed in the case study. Nerve conduction study (NCS) was performed in bilateral median and ulnar motor and sensory nerves. CMAP (compound muscle action potential) and SNAP(sensory nerve action potential) and motor and sensory NCV (nerve conduction velocity) was decreased and the distal latency was prolonged in both ulnar and median nerves. These observations indicate a sensorimotor demyelinating and axonal peripheral neuropathy in the patient due to iron deficiency.

Normative value of sensory nerve action potential of median and ulnar nerves

Normative value of sensory nerve action potential of median and ulnar nerves

Sural Sensory Nerve Action Potential: A Study in Healthy Indian Subjects at Tertiary Care Center of North-West India.

This study was done to obtain the reference data for the sural SNAP amplitude and latency at distances of 14, 12, and 10 cm from the active recording electrode in Indian healthy subjects for different age groups. Two hundred forty-four healthy subjects (18-80 years) were included in this cross-sectional study. Subjects were divided into six groups according to age. Sural SNAP was recorded antidromically stimulating at three sites (14, 12, and 10 cm from the recording electrode). The quantitative variables were expressed as Mean ± SD/Median (IQR) and compared using t test/ANOVA. Transformed data for amplitude were analyzed with the use of paired t test. P < 0.05 was considered statistically significant. SPSS version 20.0 software was used for statistical analysis. Mean age of included subjects was 43.28 years. Maximum leg girth was at 14 cm. Analysis showed a significant difference in the leg girth at all three sites (P < 0.001). Sural SNAP latency at each stimulating site was compared in different age groups, no significant difference was found between groups (P = 0.19). Maximum amplitude was in the 18-30-years age group and amplitude was minimum in the 71-80-years age group (4.34 and 2.79, respectively). The difference in the amplitude recorded in the different age groups was found to be statistically different (P < 0.001). The difference in the amplitude recorded at each site was found to be statistically different (P < 0.001). This is the first study with a large sample size (244 subjects) to provide age-stratified reference data for SNAP in the Indian population by using three sites of stimulation at distances of 14, 12, and 10 cm from the recording electrode. This study shows that sural SNAP amplitude varies with the age of the subject and distance from stimulation.

QS35. Dermal Sensory Regenerative Peripheral Nerve Interface (DS-RPNI) for Multimodal Sensory Feedback

Purpose: Sensory tactile feedback is crucial in our everyday lives as it helps us characterize held objects, modulate motor actions, and understand our limb’s position in space. Though sensors for exteroceptive stimuli detection have been developed for advanced prostheses, persons with upper extremity amputation often never regain physiologically relevant, natural sensory feedback largely in part due to lack of an appropriate user-prosthetic interface. Current neural interfaces lack stable long-term transmission of sensory information from the environment, natural sensory perception, and modality- and somatotopic-matched sensory feedback. To address the critical need for a high fidelity, stable interface that can facilitate natural sensory feedback, our lab has created the Dermal Sensory Regenerative Peripheral Nerve Interface (DS-RPNI), which involves securing a de-epithelialized dermal graft around a transected sensory nerve. The DS-RPNI provides the ideal end organ targets for physiologic reinnervation by regenerating sensory axons, attenuates neuroma formation, and allows for stability and longevity of neural signaling that is not painful to the user. Natural reinnervation also has the potential for providing a full range of modality-matched sensation. We have previously shown that DS-RPNIs are successfully revascularized and neurotized with minimal scar tissue formation, and that they facilitate graded neural signaling to both mechanical and electrical stimuli. Expanding on this previous work, the purpose of this study was to assess the range of sensory modalities (i.e., pressure, vibration, heat, cold, nociception) that can successfully elicit compound sensory nerve action potentials following application of stimuli to DS-RPNI. Methods: Twenty rats underwent transection of the sural sensory nerve with subsequent securement of the transected nerve end in either acellular dermal matrix (negative control group) or de-epithelialized dermal graft from the hindpaw of a donor rat (DS-RPNI group). Compound sensory nerve action potentials (CSNAPs) were evaluated after a 3-month maturation period and elicited after exposure to pressure, vibration, heating, cooling, and nociceptive modality testing for each rat. Only one sensory modality was tested at a time, and an intertrial interval of 5 minutes was waited between testing trials for each modality testing. Statistical analyses were performed to compare the DS-RPNI group to negative control group. Results: We found that the DS-RPNI can effectively respond to different sensory modalities and that the elicited CSNAP were greater than those of the negative control group that lack the end organ targets for reinnervation. Increased DS-RPNI response compared to the negative control suggests that DS-RPNI response is most likely due to functional reinnervation rather than direct nerve end stimulation. Conclusions: The results of this study demonstrate the potential of the DS-RPNI as a multi-modality sensory peripheral nerve interface, potentially revolutionizing the frontier of prosthetic innovations. Future directions will focus on understanding the immunohistological composition of the DS-RPNI that contributes to its success as a neural interface.

Long-Term Outcome of Electrodiagnostic Values and Symptom Improvement After Carpal Tunnel Release: A Retrospective Cohort Study

The aim of this study was to evaluate electrodiagnostic studies and clinical outcomes after carpal tunnel release surgery in moderate and severe cases of carpal tunnel syndrome (CTS). Seventy-two patients with moderate or severe CTS who underwent carpal tunnel release surgery (46 unilateral; 26 bilateral; total, 98 surgeries) between 2009 and 2014 were included in the study. The cases were divided into 2 groups according to electrodiagnostic results: those with moderate CTS and those with severe CTS. Michigan Hand Outcomes Questionnaire scores and electrodiagnostic data (sensory nerve action potentials and compound muscle action potentials) were recorded before surgery and in postoperative follow-up studies obtained at 3 months, 1 year, and 5 years. There were 56 surgeries in the moderate CTS group and 42 surgeries in the severe CTS group. Sensory nerve action potentials and compound muscle action potentials were significantly lower in the severe CTS group when compared to the moderate CTS group at all follow-up times. There was a significant difference in Michigan Hand Outcomes Questionnaire scores between the groups before surgery, but no significant differences at the final follow-up. It was found that the values of all parameters (sensory nerve action potentials, compound muscle action potentials, and Michigan Hand Outcomes Questionnaire score) demonstrated significant improvements with time in both the severe and the moderate CTS groups. Carpal tunnel release surgery improves symptoms, regardless of the preoperative severity. Postoperative electrodiagnostic study results of patients with moderate CTS improve to a greater degree than those of patients with severe CTS, but all remain abnormal. Prognosis IIb.

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.

Comparison of Clinical Symptoms and Neurophysiological Findings in Patients With Chemotherapy Induced Peripheral Neuropathy.

IntroductionTaxanes are associated with a distal sensory neuropathy, significantly affecting cancer survivor quality of life. However, chemotherapy-induced peripheral neuropathy (CIPN) assessments are primarily based on clinical symptoms rather than objective neurophysiologic findings. Therefore, we investigated neurophysiologic changes in symptomatic subjects, comparing them with symptom severity.Materials and MethodsMedical charts of 111 subjects who were referred for CIPN diagnosis after chemotherapy for breast or ovarian cancer between May 1, 2016, and December 31, 2019, were retrospectively reviewed. Demographics, anthropometric parameters, and Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) pain scale data were collected. The nerve conduction study (NCS) results, including sensory nerve action potentials recorded from sural nerves, were analyzed relative to clinical symptoms. To optimize follow-up (FU) NCS diagnostic sensitivity, relative references of FU sural amplitude reductions to >30% and an absolute reference <10 μV were used.ResultsEighty-eight female patients met the criteria, and 20 underwent FU NCS. Baseline and FU sural amplitudes showed significant positive correlation with respective LANSS scores (p < 0.01). FU sural amplitude was significantly lower than the initial result (p < 0.05). The FU LANSS score was not different from the initial score. Initial NCS sensitivity and specificity for clinically suspected CIPN diagnoses with LANSS were 69.7 and 47.3%, respectively. All 20 subjects with FU evaluation were clinically compatible with CIPN (LANSS >12) at initial and FU assessments. Among them, only six (30.0%) had abnormal sural amplitudes (<10μV for ≤50 s, <3 μV for 60 s, <1 μV for 70 s) in the initial NCS. In the FU NCS, sural amplitude became abnormal in five additional subjects. Between the initial and FU NCS, sural amplitude was reduced by > 30% in eight subjects (40.0%). NCS sensitivity increased to 65.0% when including either abnormal sural amplitudes or a > 30% reduction in sural amplitude in FU studies.ConclusionsAlthough clinical symptoms and NCS results were positively correlated, a single NCS point had limited value for suspected CIPN electrophysiological diagnoses. Serial NCS during chemotherapy might help assess the degree of chemotherapy-induced nerve damage, attain evidence of CIPN prior to symptom aggravation, and monitor the progression of CIPN. Further study is needed to find specific relative references for variable patient factors to increase the sensitivity of electrophysiological studies of clinically suspected CIPN.

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.

Electrodiagnostic findings in facial onset sensory motor neuronopathy (FOSMN)

ObjectiveTo determine the electrodiagnostic characteristics of facial onset sensory and motor neuronopathy (FOSMN). MethodsElectrophysiological data from 10 FOSMN patients in Newcastle-upon-Tyne and Sydney were reviewed. Relevant literature was reviewed. ResultsFindings on standard electrophysiological assessment were in broad agreement with those published: blink reflexes were abnormal in all but one patient; sensory nerve action potentials were reduced but compound muscle action potentials preserved; mixed acute and chronic neurogenic change was identified on needle electromyography in bulbar and cervico-thoracic muscles in approximately 50% of patients.Upper limb somatosensory evoked potential (SEP) central conduction times were increased (n = 4) and progressed on repeat testing (n = 3). Upper motor neuron dysfunction was revealed by several measures [ipsilateral motor evoked potentials (MEPs) (n = 1); reduced short interval intra-cortical inhibition on threshold-tracking transcranial magnetic stimulation (n = 2); absent beta-band intermuscular coherence (n = 3)]. ConclusionsElectrodiagnostic investigation of FOSMN should include blink reflex testing, SEPs and tests of upper motor neuron function. The combination of progressive lower motor neuron disease and upper motor neuron disease on neurophysiological investigation provides further support for the contention that FOSMN is a rare variant of motor neurone disease. SignificanceThese findings will aid the neurologist and neurophysiologist in making a confident diagnosis of FOSMN, thus expediting appropriate care.

Guillain-Barré Syndrome Following the ChAdOx1-S/nCoV-19 Vaccine: A Case Report

Serious neurological complications following coronavirus disease 2019 (COVID-19) vaccination, such as cerebral venous sinus thrombosis or acute disseminated encephalomyelitis, have rarely been reported. Here, we report a case of Guillain-Barré syndrome (GBS) that occurred within 2 weeks of receiving the AstraZeneca ChAdOx1-S/nCoV-19 vaccine. A 61-year-old man presented with weakness and hypesthesia of the legs 9 days after the first dose of the ChAdOx1-S vaccine. The patient progressed to respiratory failure and severe quadriparesis. Nerve conduction studies showed markedly reduced amplitudes of compound muscle action potentials and sensory nerve action potentials in both upper and lower extremities, without definitive evidence of demyelination. The patient was diagnosed with axonal GBS and received intravenous immunoglobulin treatment, with a poor response. This is a rare case of GBS after COVID-19 vaccination in Korea. Physicians should be aware of this rare but serious complication of the COVID-19 vaccine to effectively manage such a situation in clinical practice.

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.

Sensory Thresholds and Peripheral Nerve Responses in Chronic Tension-Type Headache and Neuropsychological Correlation.

Chronic tension-type headache (CTTH) is a common disease with no fully defined pathophysiological processes. We designed a study to value electrophysiological responses in these patients and their correlation with possible psychopathological manifestations in order to deepen understanding of central and peripheral mechanisms of CTTH. In 40 patients with CTTH and 40 healthy controls, we used electrical stimulation to determine sensory threshold (SPT) and pain perception threshold (PPT) and the characteristics of the electrophysiological sensory nerve action potential (SNAP): initial sensory response (ISR) and supramaximal response (SMR). We then calculated the intensity differences between thresholds (IDT), namely SPT-PPT, ISR-SMR and SMR-PPT, and correlated these IDTs with psychological characteristics: trait and state anxiety, depression, and emotional regulation. The SPT, together with the ISR and SMR thresholds, were higher (p < 0.01) in CTTH patients. The SMR-PPT IDT was smaller and correlated with significantly higher indicators of depression, state and trait anxiety, and poorer cognitive reappraisal. CTTH patients have less capacity to recognize non-nociceptive sensory stimuli, greater tendency toward pain facilitation, and a poor central pain control requiring higher stimulation intensity thresholds to reach the start and the peak amplitude of the SNAP. This is consistent with relative hypoexcitability of the Aβ nerve fibers in distant regions from the site of pain, and therefore, it could be considered a generalized dysfunction with a focal expression. Pain facilitation is directly associated with psychological comorbidity.

Effect of Percutaneous Electric Stimulation with High-Frequency Alternating Currents on the Sensory-Motor System of Healthy Volunteers: A Double-Blind Randomized Controlled Study

Former studies investigated the application of high-frequency alternating currents (HFAC) in humans for blocking the peripheral nervous system. The present trial aims to assess the effect of HFAC on the motor response, somatosensory thresholds, and peripheral nerve conduction when applied percutaneously using frequencies of 10 kHz and 20 kHz in healthy volunteers. A parallel, placebo-controlled, double-blind, randomized clinical trial was conducted. Ultrasound-guided HFAC at 10 kHz and 20 kHz and sham stimulation were delivered to the median nerve of 60 healthy volunteers for 20 min. The main assessed variables were the maximum isometric flexion strength (MFFS) of the index finger, myotonometry, pressure pain threshold (PPT), mechanical detection threshold (MDT), and sensory nerve action potential (SNAP). A decrease in the MFFS is observed immediately postintervention compared to baseline, both in the 10 kHz group (−8.5%; 95% CI −14.9 to −2.1) and the 20 kHz group (−12.0%; 95% CI −18.3 to −5.6). The between-group comparison of changes in MFFS show a greater reduction of −10.8% (95% CI −19.8 to −1.8) immediately postintervention in the 20 kHz compared to the sham stimulation group. The percutaneous stimulation applying 20 kHz HFAC to the median nerve produces a reversible postintervention reduction in strength with no adverse effects.