Nerve Action Potentials Research Articles

Evaluation of the Effects of Guizhi Shaoyao Zhimu Decoction on Rheumatoid Arthritis by Ultrasound Combined with Electrophysiological Examination.

Guizhi Shaoyao Zhimu Decoction can be used in the treatment of rheumatoid arthritis, but there is scarce literature on using ultrasound combined with electrophysiology to evaluate the efficacy of this traditional Chinese medicine. This study aimed to explore the clinical effect of Guizhi Shaoyao Zhimu decoction on cold-dampness arthralgia rheumatoid arthritis (RA) by ultrasound and electrophysiological examination. A total of 64 patients with rheumatoid arthritis were randomly divided into two groups, with 32 cases in each group. The control group was treated with conventional western medicine, and the experimental group was treated with Guizhi Shaoyao Zhimu Decoction in addition to conventional western medicine. After 4 weeks of treatment, traditional Chinese medicine (TCM) symptom scores, erythrocyte sedimentation rate (ESR), Creactive protein (CRP), 28 joint disease range of motion score (DAS28), ultrasonic score, and electrophysiological examination results were observed. There were significant differences in TCM syndrome scores, ESR, CRP, DAS28, and ultrasound scores in the two groups before and after treatment (P<0.05). Compared between the two groups after treatment, there were statistically significant differences in TCM syndrome scores, ESR, CRP, DAS28, and ultrasound scores (P<0.05). The motor nerve conduction velocity (MNCV), sensory nerve conduction velocity (SNCV), and action potential (AP) of the median nerve and ulnar nerve in the experimental group were significantly increased compared with the control group (P<0.05). Guizhi Shaoyao Zhimu Decoction combined with conventional western medicine has a significant effect on cold-dampness arthralgia rheumatoid arthritis, and ultrasound and electrophysiological examination can be used to evaluate its curative effect.

Laterality, sexual dimorphism, and human vagal projectome heterogeneity shape neuromodulation to vagus nerve stimulation

Neuromodulation by vagus nerve stimulation (VNS) provides therapeutic benefits in multiple medical conditions, including epilepsy and clinical depression, but underlying mechanisms of action are not well understood. Cervical vagus nerve biopsies were procured from transplant organ donors for high resolution light microscopy (LM) and transmission electron microscopy (TEM) to map the human fascicular and sub-fascicular organization. Cervical vagal segments show laterality with right sided dominance in fascicle numbers and cross-sectional areas as well as sexual dimorphism with female dominance in fascicle numbers. The novel and unprecedented detection of numerous small fascicles by high resolution LM and TEM expand the known fascicle size range and morphological diversity of the human vagus nerve. Ground truth TEM quantification of all myelinated and unmyelinated axons within individual nerve fascicles show marked sub-fascicular heterogeneity of nerve fiber numbers, size, and myelination. A heuristic action potential interpreter (HAPI) tool predicts VNS-evoked compound nerve action potentials (CNAPs) generated by myelinated and unmyelinated nerve fibers and validates functional dissimilarity between fascicles. Our findings of laterality, sexual dimorphism, and an expanded range of fascicle size heterogeneity provide mechanistic insights into the varied therapeutic responses and off-target effects to VNS and may guide new refinement strategies for neuromodulation.

The Enigma of the Motor Nerve Conduction Study.

In motor nerve conduction studies (MNCS), proximal stimulation should give a longer duration and lower amplitude compound muscle action potential (CMAP) due to higher temporal dispersion. Yet the CMAP waveforms at the distal and proximal stimulation sites appear remarkably similar. The objective of this study was to confirm this anomaly and investigate its possible cause by studying the median and ulnar nerves. Recordings from 50 subjects with normal electrodiagnostic studies were reviewed. The conduction velocity (CV) was measured using different points on the negative phase of the CMAP including its peak and baseline crossing. Collision studies were performed in three healthy subjects to measure the dispersion when nerve action potentials (APs) propagated from elbow to wrist. CV was relatively unaffected by the measurement point on the CMAP. The CMAP duration with elbow stimulation increased minimally compared to wrist stimulation. This was inconsistent with the dispersion of the AP from wrist to elbow measured in collision studies. The insignificant change in the CMAP in spite of axon AP dispersion is an enigma. We hypothesize that the terminal conduction time (TCT) (i.e., conduction in terminal axon branches, neuromuscular transmission, etc.) is independent of axon CV, represents a significant portion of the latency, masks AP dispersion, and reduces CMAP dispersion. This yields similar CMAPs with distal and proximal stimulation. The onset latency at the distal stimulation site does not depend on CV. Thus, onset latency and CV may not reflect the conduction properties of the fastest conducting axons.

Selective nociceptive modulation using a novel prototype of transcutaneous kilohertz high-frequency alternating current stimulation: a crossover double-blind randomized sham-controlled trial

BackgroundKilohertz high-frequency alternating current (KHFAC) stimulation has demonstrated to induce rapid and reversible nerve blocks without causing nerve damage. Previous studies have explored frequency-dependent effects using a transcutaneous approach in humans from 5 to 20 kHz. Nevertheless, its application in humans is limited by the lack of stimulators approved for frequencies above 20 kHz. Therefore, this study aimed to assess the effects and safety of transcutaneous KHFAC stimulation using a novel prototype stimulator, comparing interventions at 30, 40, and 50 kHz to sham stimulation on experimental pain, sensory, motor, and neurophysiological outcomes.MethodsA randomized, double-blind, sham-controlled crossover study involving 34 healthy participants was conducted. Four interventions (30, 40, 50 kHz, and sham) were administered, and stimulation was applied for 20 min to the median nerve of the non-dominant hand. A prototype stimulator capable of delivering frequencies between 1 and 50 kHz, with a maximum peak-to-peak output current intensity of 400 mA was designed. The intensity applied during the stimulation was below motor threshold, evoking a ‘strong but comfortable’ tingling sensation. Primary outcomes included heat pain threshold (HPT), pressure pain threshold (PPT), and adverse effects. The secondary outcomes included static two-point discrimination sensitivity, isometric pinch strength, and median sensory nerve action potential (SNAP).ResultsCompared with the sham stimulation, all the active interventions exhibited a significantly greater increase in the PPT during and immediately after the stimulation, while only a significant increase was observed at 40 kHz (4.1 N/cm2; 95%CI 0.3 to 7.9) at 15 min post-intervention. Compared to sham stimulation, the 40 kHz intervention had a significantly greater effect on the HPT at all time points, with the greatest difference (1.4 °C; 0.6 to 2.1) occurring immediately post-intervention. Adverse effects during active interventions included petechiae, erythema, and itching, which resolved at 24 h post-intervention. For secondary outcomes, only a significant reduction in the median SNAP velocity was observed in the sham stimulation group compared to the 50 kHz group.ConclusionsActive KHFAC stimulation, particularly at 40 kHz, delivered through a novel stimulator, effectively increased the PPT and HPT without affecting tactile or motor outcomes, inducing mild skin-related adverse effects. These findings have potential implications for people with pain-related pathologies.Trial registrationNCT05230836.

Hopkins Syndrome: An Uncommon Cause of Weakness in Intensive Care Unit

BackgroundHopkins syndrome is a rare polio-like syndrome, with an incompletely understood pathophysiology, that affects children after asthma crisis. MethodsA 10-year-old girl was admitted to the intensive care unit following a severe asthma attack, requiring mechanical ventilation for a period of five days. After regaining consciousness, the patient exhibited development of asymmetric flaccid paraparesis. Neuroaxis magnetic resonance imaging revealed contrast enhancement in the anterior lumbar roots, with the enhancement originating at the T11 level and extending downward on axial series. Nerve conduction study revealed the absence of compound muscle action potentials in the tibialis and peroneal nerves on the left, with preserved sensory nerve action potentials. ResultsBased on the patient's clinical phenotype, which was most consistent with a polio-like syndrome arising acutely following an asthmatic crisis, the diagnosis of Hopkins syndrome was established. ConclusionHopkins syndrome is a rare polio-like syndrome that is probably underdiagnosed and has a poor motor prognosis.

The Effects of Thermal and Pulsed Ultrasound on Pain and Function in Patients with Carpal Tunnel Syndrome: A Randomized Controlled Trial

ABSTRACT Objective While ultrasound therapy is common for carpal tunnel syndrome, the relative merits of thermal versus pulsed ultrasound remain unclear. This study compares their therapeutic effects. Design Randomized, double-blinded, placebo-controlled trial. Ninety-two adults aged 30-60 years with mild-moderate carpal tunnel syndrome (characteristic symptoms, positive clinical tests, abnormal electrophysiology) were randomized into 4 groups receiving 4 weeks night splinting plus 12 ultrasound sessions: Group A: 1 MHz, 1.0 W/cm2 continuous ultrasound for 5 minutes; Group B: 1 MHz, 25% duty cycle, 1.0 W/cm2 pulsed ultrasound for 15 minutes; Group C: 5 minutes thermal plus 15 minutes pulsed ultrasound; Group D: sham ultrasound for 15 minutes. Pain (VAS), function (DASH-Arabic), nerve conduction, and grip strength were measured at baseline, 4, and 8 weeks. Results Thermal and pulsed ultrasound groups improved in all outcomes versus placebo over 8 weeks (p < 0.05). Pulsed ultrasound decreased pain and distal motor latency more than placebo (p < 0.05). Thermal ultrasound increased sensory nerve action potentials versus placebo (p < 0.05). Conclusion Thermal and pulsed ultrasound with splinting improved pain, disability, grip strength, and nerve conduction in carpal tunnel syndrome. Pulsed ultrasound was optimal for pain and motor function, while thermal ultrasound enhanced sensory nerve function.

Sural-to-medial femoral cutaneous amplitude ratio in early diagnosis of uremic neuropathy.

Medial femoral cutaneous (MFC) sensory nerve action potentials (SNAPs) can be easily recorded using distal stimulation. This study aimed to identify a new parameter using MFC SNAPs for the early electrophysiological diagnosis of length-dependent axonal polyneuropathy (LDAP) associated with uremic neuropathy. Patients with chronic renal failure who were referred to the electrodiagnostic laboratory due to symptoms suggesting polyneuropathy were included. Assessments encompassed neurological examination, Michigan Neuropathy Screening Instrument (MNSI), and Semmes-Weinstein monofilament test. Antidromic radial, median, ulnar, MFC, sural, and superficial peroneal sensory; median, ulnar, tibial, and peroneal motor nerve conduction studies were performed. Sural-to-radial amplitude ratio (SRAR) and sural-to-medial femoral cutaneous amplitude ratio (SMFCAR) were calculated, and their diagnostic sensitivities were compared with the age and sex matched healthy controls. Thirty-two chronic renal failure patients (mean age 60.0 ± 9.6 years) and 37 controls (60.6 ± 9 years) were included. MNSI indicated clinical polyneuropathy in 59.4% of patients, while sural SNAP amplitude was diagnostic in 78%. Median SRAR and SMFCAR values were significantly lower in patients than controls (p < .001 for both). The cut-off values for SMFCAR and SRAR were <1.82 and <0.30, respectively, both with a sensitivity of 59% and a specificity of 94%. Sural SNAP is the most sensitive parameter in the diagnosis of LDAP. SMFCAR is not superior to SRAR. If the sural SNAP amplitude is normal, SMFCAR can serve as an alternative to SRAR in dialysis patients with bilateral arteriovenous fistulae or in those unable to undergo radial NCS.

Evaluation of Split Hand Syndrome in Early Diagnosis of Amyotrophic Lateral Sclerosis by Nerve Conduction Study as a Diagnostic Tool

Background: Amyotrophic lateral sclerosis (ALS), a degenerative disease of the motor neurons that can present diversly. Needle electromyography (EMG) is the gold standard investigation for the diagnosis of ALS. Split hand syndrome (SHS) demonstrated by nerve conduction study (NCS); a noninvasive tool could be useful in diagnosing ALS. This study aimed to assess SHS by NCS in ALS. Methods: This diagnostic accuracy case-control study included 37 cases of ALS and 37 age and gender-matched controls. Compound muscle action potential (CMAP) and distal motor latency (DML) of median and ulnar nerves and the ratio of median and ulnar CMAP and DML were compared between study groups. The diagnostic validity testing of electrophysiological SHS was also done. Results: The mean age of the ALS and control groups were similar, 39.8±2.7 and 39.3±2.6 years, respectively. Sixteen (43.2%) ALS patients were in 30-59 years age group. Male-female ratio was 5.2. In the ALS group, median-ulnar CMAP ratio was lower and median-ulnar DML ratio was prolonged than the control. The diagnostic efficacy of median-ulnar CMAP ratio and DML ratio were calculated. A median-ulnar CMAP ratio cut-off value ≤1 showed 70% sensitivity, 97% specificity, 96% positive predictive value and 77% negative predictive value. A median-ulnar DML ratio cut-off value ≥1.5 showed 48% sensitivity, 89% specificity, 82% positive predictive value and 65% negative predictive value. Conclusion: NCS demonstrating SHS can be an important tool in the early diagnosis of ALS. J Bangladesh Coll Phys Surg 2024; 42: 350-354

Clinical significance of upper arm motor nerve conduction velocity in cubital tunnel syndrome.

Retrograde denervation occurs in severe entrapment neuropathy. This study aimed to investigate changes in motor nerve conduction velocity (MNCV) at the upper arm, specifically proximal to the elbow, in cubital tunnel syndrome (CuTS) and to correlate these changes with preoperative severity and postoperative outcomes. We retrospectively reviewed 95 elbows with 81 patients with CuTS for preoperative severity, and then 67 elbows with 60 of these patients who underwent anterior subcutaneous transposition surgery for postoperative outcome, classified into favorable and unfavorable groups according to Messina grade. The reduction of upper arm MNCV was correlated with aging, decreased compound muscle action potentials of abductor digiti minimi muscle, loss of sensory nerve action potentials, and modified McGowan grade. Postoperative assessment revealed lower MNCV values in the "unfavorable" group compared to the "favorable" group at 1 month, 6 months, and the last follow up. At each time point, the optimal cut-off value of upper arm MNCV for predicting postoperative outcomes was 54.1 m/s. Upper arm MNCV might be a useful predictor of poor surgical outcome. Ulnar nerve MNCV at the upper arm should be measured alongside routine assessment of MNCV at the elbow and forearm, especially in clinically severe cases considering surgery.

3T-3D FLAIR MRI in Menière's disease: associated profiles with clinical symptoms and electroacoustic characteristics.

Diagnosis of Menière's disease relies on clinical symptoms. Injected 3T MRI can show endolymphatic hydrops (EH), but correlation with the clinical status of MD, (probable -PMD or definite-DMD) remains doubtful. We revealed endolymphatic pressure disruption through functional exploration and verified if it was associated with an EH through MRI. We prospectively analyzed 3D3T FLAIR MRI of DMD and PMD patients. All of them underwent electrocochleography (EcoG), distortion-product otoacoustic emissions (DPOAEs), and videonystagmograhy (VNG). Amplitudes of summating potential (SP) and cochlear nerve action potential (AP) were measured on EcoG. DPOAE-phase was collected at 1kHz for the 2f1-f2 DPOAE between sitting and laying position. A SP/AP ≥ 40% and a DPOAE phase-shift > 40° revealed pressure disruption. 39 patients (25 women, 53 y.o. 20-78), were included, with 32 DMD ears and 11 PMD ears. MRI was performed in a median of 21 days [0; 68] from the MD incident. Audiovestibular exploration took place 41 days after the crisis [0;83]. MRI revealed an EH in 71.9% and 27.2% of DMD and PMD, respectively. When combining functional explorations and MRI, testing was positive in 97% for DMD and 82% for PMD. When abnormal (59%), VNG mainly showed hyporeflexia in the diseased ear. In patients suffering from DMD or PMD, with endolymphatic pressure disturbances confirmed by combined DPOAE-phase and EcoG, 3T 3D MRI reveals EH mostly in DMD but rarely in PMD. This seems to confirm that disturbance of endolymphatic pressure precedes EH.

Nerve conduction studies of sensory nerves with proven vasculitic neuropathy often show an absent electrical response.

In vasculitic neuropathy (VN), it is not known whether nerve conduction studies (NCSs) showing low amplitude sensory nerve action potentials (SNAPs) or those with absent responses have a higher yield in detecting appropriate nerves for pathological confirmation. Our goal was to describe NCS findings of nerves prior to biopsy in patients with VN. We performed a retrospective study between January 2000 and April 2021 in patients with VN who either met pathological definite criteria for VN or criteria for clinically probable VN and had NCS of the sural or superficial radial sensory nerves prior to biopsy of the same nerve. We included 61 patients with VN. The pathological findings showed 37 (60.7%) definite, 14 (23%) probable, and 2 (3.3%) possible VN; eight (13%) samples did not meet Peripheral Nerve Society pathological criteria. Most patients who met definite (20 out of 37, 54%) and probable (9 out of 14, 64%) VN pathological criteria had absent SNAPs. Only three out of eight (37.5%) patients without VN pathological findings had absent SNAPs. There was no statistically significant correlation between pathological diagnosis and SNAP amplitude (χ2 = 1.98, p = .58). Additionally, no association was found between VN pathological criteria and use of immunomodulatory treatment (p = .67) or corticosteroids (p = .52). Most nerves with pathological VN findings showed no response on NCS. In patients with suspected VN, sural or superficial radial sensory nerves with absent responses on NCS are adequate biopsy targets as compared to nerves in which SNAPs can be recorded.

A Retrospective Study of Lateral Antebrachial Cutaneous Nerve Neuropathy: Electrodiagnostic Findings and Etiologies in 49 Cases.

The lateral antebrachial cutaneous nerve (LACN) is the terminal sensory branch of the musculocutaneous nerve and is rarely entrapped or injured. This study describes the electrodiagnostic (EDX) findings and etiologies of LACN neuropathy. This is a review of 49 patients with pain and/or paresthesia of the forearm who underwent EDX studies. The diagnosis of LACN neuropathy was based on clinical and sensory conduction abnormalities. The most common etiology of LACN neuropathy was iatrogenic injury in 30 (61.2%) patients, primarily due to biceps tendon repair at the elbow (11 [36.7%]) and phlebotomy (5 [16.7%]). Fifteen (30.6%) patients sustained a non-iatrogenic injury at the proximal forearm/elbow, consisting of six (60%) laceration injuries and five (33.3%) stretch injuries. Four (8.2%) patients comprised the "other" etiology category, including two mass lesions causing LACN compression. Pain, paresthesia, and/or numbness in the LACN distribution were reported in 33 (67.3%), 27 (55.1%), and 23 (46.9%) patients, respectively. Hypoesthesia was detected in 45 (91.8%) patients, and dysesthesia in 7 (14.3%). The sensory nerve action potentials (SNAPs) of the LACN on the symptomatic side were absent in 44 (89.8%) patients. Of the five patients whose SNAPs of the LACN were detected, all had a decreased amplitude, and two had increased sensory latency. The most common etiology for LACN neuropathy in this series was iatrogenic injury; repair of biceps tendon at the elbow was the most frequent provoking cause. Protection of the LACN during surgical procedures at the elbow and forearm is vital to prevent iatrogenic injury.

Neurofilament light chain as a biomarker for hereditary ATTR amyloidosis − correlation between neurofilament light chain and nerve conduction study

Background Neurofilament light chain (NfL) is a biomarker of neuronal injury in hereditary ATTR (ATTRv) amyloidosis. However, the correlation between NfL and nerve conduction study (NCS), the standard test for ATTRv neuropathy, has not been investigated. Objective Elucidate the correlation between NfL and NCS parameters. Methods 227 serum NfL measurements were performed in 45 ATTRv patients, 5 asymptomatic carriers, and 12 controls. Among them, 177 simultaneous analyses of NCS and NfL were conducted in 45 ATTRv patients. Results NfL levels of symptomatic patients were significantly higher than those of asymptomatic carriers and controls. Serum NfL levels were correlated with NCS parameters, especially compound muscle action potential (CMAP) and sensory nerve action potential (SNAP) amplitudes, indicators of axonal damage. CMAP and/or SNAP amplitudes were undetectable in 9 patients (no-amplitude group) due to advanced neuropathy. NfL levels in the no-amplitude group were significantly higher than those in patients with detectable CMAP/SNAP. NfL levels significantly decreased with patisiran, although no significant changes were observed in CMAP and SNAP. Conclusions NfL levels are found to be correlated with CMAP/SNAP amplitudes. Compared with NCS, NfL can be a more sensitive biomarker for detecting treatment response and active nerve damage even in patients with advanced neuropathy.

Sensory dysfunction in SMA type 2 and 3 - adaptive mechanism or concomitant target of damage?

BackgroundThe motor neuron survival protein performs numerous cellular functions; hence, spinal muscular atrophy (SMA) is considered to be a multi-organ disease with possible sensory system damage. The controversy surrounding the presence of sensory disturbances, prompted us to conduct standard electrophysiological studies and assess the sensory thresholds for different modalities in adults with SMA types 2 and 3. The study group consisted of 44 adult SMA patients (types 2 and 3). All patients underwent neurological examination using the Hammersmith Functional Motor Scale – Expanded (HFMSE). Standard sensory electrophysiological studies in the ulnar nerve and the estimation of vibratory, temperature, and warm- and cold-induced pain thresholds with temperature dispersion assessment were performed using quantitative sensory testing (QST).ResultsThe most repeatable result was the high amplitude of the sensory nerve action potentials (SNAP) in SMA patients compared to controls. This was higher in type 2 patients compared to type 3a and 3b patients and patients with low HFSME scores. Patients with SMA, especially type 3b presented a longer sensory latency and slower conduction velocity than did controls. Cold pain threshold was higher and warm dispersion larger in SMA. The vibratory limit was higher in patients with high HFSME scores.ConclusionsA high SNAP amplitude suggests sensory fibre hyperactivity, which may be based on overactivation of metabolic pathways as an adaptive mechanism in response to SMN protein deficiency with additionally coexisting small C- and A-delta fibre damage. SMA patients seem to have a concomitant, mild demyelinating process present at the early SMA stage.

Abstract P383: Increased renal afferent nerve activity and peak response to pro-inflammatory cytokine interleukin 6 in isolated dorsal root ganglion neurons from hypertensive rats

Renal afferent nerves are reported to mediate the progression of hypertension in preclinical models, putatively via an aberrant increase in activation. The underlying source of this nerve activation is unknown but we hypothesized renal inflammatory cytokines are a primary driver. We previously reported interleukin 6 (IL-6) is increased in the kidneys of hypertensive rats, and intrarenal administration of IL-6 can activate renal afferent nerves. Though these data are promising, the direct effects of IL-6 on afferent renal nerves remain unclear. We hypothesized that isolated renal afferent neurons from hypertensive rats will have increased activity and responsiveness to inflammatory cytokine IL-6 compared to normotensive controls. To test our hypothesis, we tested the direct effects of interleukin-6 (IL-6) on renal afferent nerve action potentials (AP) generated in freshly isolated dorsal root ganglion (DRG) neurons. To model salt-sensitive hypertension, uninephrectomized rats (n=6) were administered deoxycorticosterone acetate (DOCA; 100mg, sc) and 0.9% saline for drinking water for 21 days. Control rats (n=6) were uninephrectomized. To label renal afferent nerves, neuronal tracer DiI was introduced by intrarenal injection 6 days prior to DRG collection. DRGs from T10-L1 were isolated, enzymatically digested and dissociated, and cultured overnight for whole-cell patch-clamp the following day. DiI-positive neurons from both control and DOCA rats generated AP during the delivery of 100, 200, and 300 pA current steps. Data were analyzed by two-way, repeat-measures ANOVA (α=.05). At baseline, DOCA neurons had a higher (p&lt;0.05) mean AP frequency compared to controls (no difference in AP mean peak amplitude or AP duration). In both groups, increasing concentrations of IL-6 (0. 4, 4, and 40 ng/ml) elicited a dose-dependent increase in AP peak amplitude compared to baseline. No difference was detected in IL-6 responses between DOCA and controls. Overall, these data supported our original hypothesis that pro-inflammatory cytokine IL-6 would increase renal afferent nerve activity, and that said activity is increased in hypertensive DOCA-salt rats. IL-6 accumulation triggered by end organ damage due to hypertension might lead to increased afferent renal nerve activity, which exacerbates the hypertensive phenotype through a sympatho-excitatory response. Additional measurements of isolated DRG responses to pro-inflammatory mediators are underway for direct comparison.

Sural sparing reversible sensorimotor abnormalities in hypokalemia: A close mimic of GBS

Nerve conduction studies (NCS) in hypokalemic paralysis usually show decreased compound muscle action potential (CMAP) which improves with correction of hypokalemia and normalizes in between the attacks. Inactivity of Na+ K+ ATPase pump due to hypokalemia results in decreased excitability of muscle fibers resulting in reduced CMAP on NCS. Sensory symptoms, as well as abnormalities in sensory NCS is a rare phenomenon. Here we describe a 40-year-old male who presented with acute onset rapidly progressive ascending quadriparesis with type 2 respiratory failure due to hypokalemia following hepatorenal dysfunction. NCS done before hypokalemia correction, suggested sural sparing with generalized reduced CMAPs, nonrecordable median and ulnar nerves sensory nerve action potential (SNAP) and abnormal F waves. After hypokalemia correction there was improvement in CMAPs as well as SNAPs. Thus, hypokalemia can present as an axonal sensorimotor involvement with sural sparing on NCS study similar to Guillain-Barré syndrome subtype.

Ultraconformable cuff implants for long-term bidirectional interfacing of peripheral nerves at sub-nerve resolutions

Implantable devices interfacing with peripheral nerves exhibit limited longevity and resolution. Poor nerve-electrode interface quality, invasive surgical placement and development of foreign body reaction combine to limit research and clinical application of these devices. Here, we develop cuff implants with a conformable design that achieve high-quality and stable interfacing with nerves in chronic implantation scenarios. When implanted in sensorimotor nerves of the arm in awake rats for 21 days, the devices record nerve action potentials with fascicle-specific resolution and extract from these the conduction velocity and direction of propagation. The cuffs exhibit high biocompatibility, producing lower levels of fibrotic scarring than clinically equivalent PDMS silicone cuffs. In addition to recording nerve activity, the devices are able to modulate nerve activity at sub-nerve resolution to produce a wide range of paw movements. When used in a partial nerve ligation rodent model, the cuffs identify and characterise changes in nerve C fibre activity associated with the development of neuropathic pain in freely-moving animals. The developed implantable devices represent a platform enabling new forms of fine nerve signal sensing and modulation, with applications in physiology research and closed-loop therapeutics.

Recordings of Superior Laryngeal Nerve Sensory Nerve Action Potentials in a Rat Model.

Superior laryngeal nerve (SLN) function is critical to laryngeal sensation. Sensory dysfunction in the larynx, mediated through the internal branch of the superior laryngeal nerve (iSLN), is thought to occur with aging and neurodegenerative disease. However, objective analysis of iSLN neurophysiology is difficult due to its anatomic location and small diameter. This study measures sensory nerve action potentials (SNAP) from the iSLN in a rat model. SNAP data were obtained from two adult rat strains (Sprague-Dawley, SD and Fischer 344 × Brown Norway F1 Hybrid rats, FBN). Evoked responses were obtained by stimulating the main trunk of the SLN and recording the response using a 160-μm cuff electrode placed around the iSLN. SNAP were averaged from 10 stimulations. Laryngeal adductor reflex (LAR) threshold measurements were obtained with stimulation of the iSLN and direct laryngoscopy. The sections of the iSLN were obtained for histologic analysis. SLN-evoked responses were successfully obtained in 18 hemi-laryngeal preparations (SD n = 13 and FBN n = 5) with corresponding LAR threshold measurements. Mean(±SD) SNAP latency, total duration, amplitude, negative durations, and intensity were 2.28 ms (±0.56), 2.13 ms (±0.70), 879 μV (±535), and 0.69 mA (±0.25), respectively. SLN stimulation threshold to elicit an LAR was of 0.84 mA (±0.31). It is feasible to record evoked SLN responses in two adult rat strains. This work may lead to a tractable animal model for objective measurements of SLN neurophysiology with various disease states. NA Laryngoscope, 134:5028-5033, 2024.

Age related changes in skin sensitivity assessed with smartphone vibration testing

The capacity to perceive tactile input at the fingertips, referred to as tactile sensitivity, is known to diminish with age due to regressive changes to mechanoreceptor density and morphology. Sensitivity is measured as perceptual responses to stimuli of varying intensity. Contrary to traditional sensitivity monitoring instruments, smartphones are uniquely suited for remote assessment and have shown to deliver highly calibrated stimuli along a broad spectrum of intensity, which may improve test reliability. The aim of this study was to evaluate a vibration-emitting smartphone application, the Vibratus App, as a mode of estimating tactile sensory thresholds in the aging adult. The peripheral nerve function of 40 neurologically healthy volunteers (ages 18–71) was measured using monofilaments, a 128-Hz tuning fork, the Vibratus App, and nerve conduction studies (NCS). Between group differences were analyzed to determine each measurement’s sensitivity to age. Spearman correlation coefficients depicted the associative strength between hand-held measurements and sensory nerve action potential (SNAP) amplitude. Inter-rater reliability of traditional instruments and the software-operated smartphone were assessed by intraclass correlation coefficient (ICC2,k). Measurements taken with Vibratus App were significantly different between age groups (p < 0.001). The inter-rater reliability of monofilament, smartphone vibration, and tuning fork testing was moderate to good (ICC2,k = 0.65, 0.69, and 0.79, respectively). The findings of this study support further investigation of smartphones as sensitivity monitoring devices for at home monitoring of skin sensitivity.

Challenges and Advances in the Diagnosis and Management of Neurogenic Thoracic Outlet Syndrome: A Comprehensive Review.

Neurogenic thoracic outlet syndrome (nTOS) is caused by brachial plexus compression in the thoracic outlet. It accounts for 85%-95% of thoracic outlet syndrome (TOS) cases, which may also be caused by compression of the subclavian artery and vein. Compression occurs in the interscalene triangle, costoclavicular space or subpectoralis minor space, with congenital anomalies and repetitive overhead activities as contributing factors. Diagnosis is challenging due to overlapping symptoms with other conditions. Patients commonly report pain, numbness, tingling and weakness in the neck, shoulder and arm, exacerbated by arm elevation. Symptoms related to nTOS may manifest in the distribution of the upper (C5-C6), middle (C7) and lower plexus (C8-T1). Although widely used, provocative tests have varying degrees of sensitivity and specificity and may have high false-positive rates, complicating the diagnosis. Patterns on electrodiagnostic studies provide key diagnostic clues, such as reduced sensory response in the medial antebrachial cutaneous nerve and low compound motor action potential in the median nerve. Imaging techniques like magnetic resonance imaging (MRI), alongside procedures like diagnostic and therapeutic anterior scalene blocks, assist in identifying anatomical abnormalities and predicting surgical outcomes. Management of nTOS involves lifestyle changes, physical therapy, medication and botulinum toxin injections for symptomatic relief. Surgical options may include supraclavicular, transaxillary and infraclavicular approaches, each offering specific benefits based on patient anatomy and surgeon expertise. Minimally invasive techniques, such as video-assisted thoracoscopic surgery (VATS) and robotic surgery, enhance exposure and dexterity, leading to better outcomes. Future research should focus on developing precise diagnostic tools, understanding nTOS pathophysiology, standardising diagnostic criteria and surgical approaches, comparing long-term treatment outcomes and exploring preventive measures to improve patient care and quality of life. Level of Evidence: Level V (Therapeutic).