How reliable are sympathetic skin responses in subjects with spinal cord injury?

Altered Cardiac Autonomic Regulation in Individuals with Myasthenia Gravis-A Systematic Review and Meta-Analysis

The aim of this systematic review with meta-analysis was to determine differences in cardiovascular autonomic parameters between patients with myasthenia gravis (MG) and healthy controls (HCs). Two reviewers searched four electronic databases, namely PubMed, Web of Science, EMBASE, and SCOPUS, from database inception to 7 July 2023 for studies investigating cardiovascular autonomic parameters in MG vs. HCs. A random-effects meta-analysis was performed to compute Hedges' g ± 95% confidence intervals (CI). Out of a total of 2200 records, 8 observational studies with a sample size of 301 patients with MG and 454 HCs were included in the systematic review. Meta-analysis revealed lower values of expiration/inspiration ratio (g = -0.45, I2 = 74.7), baroreflex sensitivity (g = -0.56, 95%CI -0.80, -0.33; I2 = 0.3), percentage of adjacent NN intervals differing by more than 50 ms (g = -1.2, I2 = 82.8), square root of the mean of squared differences between successive beat intervals (g = -1.94, I2 = 95.1), mean of the standard deviations of all NN intervals (g = -0.83, 95%CI -1.37, -0.28; I2 = 55.5), and high frequency of HRV during tilt (g = -0.75, 95%CI -0.11, -0.39; I2 = 0). MG patients vs. HCs had higher systolic blood pressure (g = 0.39; I2 = 56.1), sympathovagal balance at rest/during tilt (LF/HF-RRIsupine, g = 0.44; I2 = 0; LF/HF-RRItilt, g = 0.86; I2 = 0; LF/HFtilt, g = 0.40; I2 = 0). As a group, MG patients have altered cardiac autonomic function, including decreased parasympathetic function, lower baroreflex sensitivity, and higher sympathovagal balance at rest and during orthostatic challenges.

Neurophysiological Changes in the First Year After Cell Transplantation in Sub-acute Complete Paraplegia

Neurophysiological testing can provide quantitative information about motor, sensory, and autonomic system connectivity following spinal cord injury (SCI). The clinical examination may be insufficiently sensitive and specific to reveal evolving changes in neural circuits after severe injury. Neurophysiologic data may provide otherwise imperceptible circuit information that has rarely been acquired in biologics clinical trials in SCI. We reported a Phase 1 study of autologous purified Schwann cell suspension transplantation into the injury epicenter of participants with complete subacute thoracic SCI, observing no clinical improvements. Here, we report longitudinal electrophysiological assessments conducted during the trial. Six participants underwent neurophysiology screening pre-transplantation with three post-transplantation neurophysiological assessments, focused on the thoracoabdominal region and lower limbs, including MEPs, SSEPs, voluntarily triggered EMG, and changes in GSR. We found several notable signals not detectable by clinical exam. In all six participants, thoracoabdominal motor connectivity was detected below the clinically assigned neurological level defined by sensory preservation. Additionally, small voluntary activations of leg and foot muscles or positive lower extremity MEPs were detected in all participants. Voluntary EMG was most sensitive to detect leg motor function. The recorded MEP amplitudes and latencies indicated a more caudal thoracic level above which amplitude recovery over time was observed. In contrast, further below, amplitudes showed less improvement, and latencies were increased. Intercostal spasms observed with EMG may also indicate this thoracic “motor level.” Galvanic skin testing revealed autonomic dysfunction in the hands above the injury levels. As an open-label study, we can establish no clear link between these observations and cell transplantation. This neurophysiological characterization may be of value to detect therapeutic effects in future controlled studies.

Acute effects of contrast bath on sympathetic skin response in patients with poststroke complex regional pain syndrome

PURPOSE

Complex regional pain syndrome (CRPS) is one of the common complications in stroke patients. Sympathetic dysfunction is usually considered underlying pathology. The evidence for contrast bath (CB) used in the treatment of CRPS is limited. The aim of the study is to investigate the possible effects of CB on the sympathetic activity in poststroke CRPS.

MATERIALS AND METHODS

Stroke patients with CRPS (CRPS group) and without CRPS (control group) were included in the study. Age, gender, duration of stroke, aetiology, plegic side, dominant hand, spasticity level, Brunnstrom stages, and comorbidities were recorded. CB was performed for one session to the plegic side of the CRPS and control groups. Sympathetic skin responses (SSR) was recorded from the plegic and healthy hands of participants at pre-CB and post-CB.

RESULTS

Each group consisted of 20 participants. No significant difference was detected in stroke duration, aetiology, and Brunnstrom stages between groups. Elbow spasticity level was significantly higher in CRPS group (p = .034). SSR amplitudes of plegic hands were significantly decreased after CB in CRPS and control groups (p = .0002, p = .013 respectively). Also, CB reduced the SSR amplitude of healty side in CRPS group (p = .003). There was no statistically significant change in SSR latency or percentage changes of SSR amplitude and latency after CB in both groups.

CONCLUSION

CB leads to a significant reduction in sympathetic activity of plegic side of stroke patients. Also, CB to the plegic side has an inhibitory effect on sympathetic activity of healty side in poststroke CRPS. ClinicalTrials.gov ID: NCT04198532.

Cardiovascular Autonomic Dysfunction in Spinal Cord Injury: Epidemiology, Diagnosis, and Management

Spinal cord injury (SCI) disrupts autonomic circuits and impairs synchronistic functioning of the autonomic nervous system, leading to inadequate cardiovascular regulation. Individuals with SCI, particularly at or above the sixth thoracic vertebral level (T6), often have impaired regulation of sympathetic vasoconstriction of the peripheral vasculature and the splanchnic circulation, and diminished control of heart rate and cardiac output. In addition, impaired descending sympathetic control results in changes in circulating levels of plasma catecholamines, which can have a profound effect on cardiovascular function. Although individuals with lesions below T6 often have normal resting blood pressures, there is evidence of increases in resting heart rate and inadequate cardiovascular response to autonomic provocations such as the head-up tilt and cold face tests. This manuscript reviews the prevalence of cardiovascular disorders given the level, duration and severity of SCI, the clinical presentation, diagnostic workup, short- and long-term consequences, and empirical evidence supporting management strategies to treat cardiovascular dysfunction following a SCI.

Automated Detection of Symptomatic Autonomic Dysreflexia Through Multimodal Sensing

OBJECTIVE

Autonomic Dysreflexia (AD) is a potentially life-threatening syndrome which occurs in individuals with higher level spinal cord injuries (SCI). AD is caused by triggers which can lead to rapid escalation of pathophysiological responses and if the trigger is not removed, AD can be fatal. There is currently no objective, non-invasive and accurate monitoring system available to automatically detect the onset of AD symptoms in real time in a non-clinical setting. Technology or Method: We developed a user-independent method of symptomatic AD detection in real time with a wearable physiological telemetry system (PTS) and a machine learning model using data from eleven participants with SCI.

RESULTS

The PTS could detect onset of AD symptoms with an average accuracy of 94.10% and a false negative rate of 4.89%.

CONCLUSIONS

The PTS can detect the onset of the symptoms AD with high sensitivity and specificity to assist people with SCIs in preventing the occurrence of AD. It would enable persons with high level SCIs to be more independent and pursue vocational activities while granting continuous medical oversight. Clinical Impact: The PTS could serve as a supplementary tool to current solutions to detect the onset of AD and prepare individuals who are newly injured to be better prepared for AD episodes. Moreover, it could be translated into a system to encourage individuals to practice better healthcare management to prevent future occurrences.

Is Technology for Orthostatic Hypotension Ready for Primetime?

Spinal cord injury (SCI) often results in the devastating loss of motor, sensory, and autonomic function. After SCI, the interruption of descending sympathoexcitatory pathways disrupts supraspinal control of blood pressure (BP). A common clinical consequence of cardiovascular dysfunction after SCI is orthostatic hypotension (OH), a debilitating condition characterized by rapid profound decreases in BP when assuming an upright posture. OH can result in a diverse array of insidious and pernicious health consequences. Acute effects of OH include decreased cardiac filling, cerebral hypoperfusion, and associated presyncopal symptoms such as lightheadedness and dizziness. Over the long term, repetitive exposure to OH is associated with a drastically increased prevalence of heart attack and stroke, which are leading causes of death in those with SCI. Current recommendations for managing BP after SCI primarily include pharmacologic interventions with prolonged time to effect. Because most episodes of OH occur in less than 3 minutes, this delay in action often renders most pharmacologic interventions ineffective. New innovative technologies such as epidural and transcutaneous spinal cord stimulation are being explored to solve this problem. It might be possible to electrically stimulate sympathetic circuitry caudal to the injury and elicit rapid modulation of BP to manage OH. This review describes autonomic control of the cardiovascular system before injury, resulting cardiovascular consequences after SCI such as OH, and the clinical assessment tools for evaluating autonomic dysfunction after SCI. In addition, current approaches for clinically managing OH are outlined, and new promising interventions are described for managing this condition.

Application of electrophysiological measures in spinal cord injury clinical trials: a narrative review

STUDY DESIGN

Narrative review.

OBJECTIVES

To discuss how electrophysiology may contribute to future clinical trials in spinal cord injury (SCI) in terms of: (1) improvement of SCI diagnosis, patient stratification and determination of exclusion criteria; (2) the assessment of adverse events; and (3) detection of therapeutic effects following an intervention.

METHODS

An international expert panel for electrophysiological measures in SCI searched and discussed the literature focused on the topic.

RESULTS

Electrophysiology represents a valid method to detect, track, and quantify readouts of nerve functions including signal conduction, e.g., evoked potentials testing long spinal tracts, and neural processing, e.g., reflex testing. Furthermore, electrophysiological measures can predict functional outcomes and thereby guide rehabilitation programs and therapeutic interventions for clinical studies.

CONCLUSION

Objective and quantitative measures of sensory, motor, and autonomic function based on electrophysiological techniques are promising tools to inform and improve future SCI trials. Complementing clinical outcome measures, electrophysiological recordings can improve the SCI diagnosis and patient stratification, as well as the detection of both beneficial and adverse events. Specifically composed electrophysiological measures can be used to characterize the topography and completeness of SCI and reveal neuronal integrity below the lesion, a prerequisite for the success of any interventional trial. Further validation of electrophysiological tools with regard to their validity, reliability, and sensitivity are needed in order to become routinely applied in clinical SCI trials.

Comparison between esophageal and intestinal temperature responses to upper-limb exercise in individuals with spinal cord injury

STUDY DESIGN

Experimental study.

OBJECTIVE

Individuals with spinal cord injuries (SCI) may present with impaired sympathetic control over thermoregulatory responses to environmental and exercise stressors, which can impact regional core temperature (T_core) measurement. The purpose of this study was to investigate whether regional differences in T_core responses exist during exercise in individuals with SCI.

SETTING

Rehabilitation centre in Wakayama, Japan.

METHODS

We recruited 12 men with motor-complete SCI (7 tetraplegia, 5 paraplegia) and 5 able-bodied controls to complete a 30-min bout of arm-cycling exercise at 50% V̇O₂ peak reserve. T_core was estimated using telemetric pills (intestinal temperature; T_int) and esophageal probes (T_eso). Heat storage was calculated from baseline to 15 and 30 min of exercise.

RESULTS

At 15 min of exercise, elevations in T_eso (Δ0.39 ± 0.22 °C; P < 0.05), but not T_int (Δ0.04 ± 0.18 °C; P = 0.09), were observed in able-bodied men. At 30 min of exercise, men with paraplegia and able-bodied men both exhibited increases in T_eso (paraplegia: Δ0.56 ± 0.30 °C, P < 0.05; able-bodied men: Δ0.60 ± 0.31 °C, P < 0.05) and T_int (paraplegia: Δ0.38 ± 0.33 °C, P < 0.05; able-bodied men: Δ0.30 ± 0.30 °C, P < 0.05). T_eso began rising 7.2 min earlier than T_int (pooled, P < 0.01). Heat storage estimated by T_eso was greater than heat storage estimated by T_int at 15 min (P = 0.02) and 30 min (P = 0.03) in men with paraplegia. No elevations in T_eso, T_int, or heat storage were observed in men with tetraplegia.

CONCLUSIONS

While not interchangeable, both T_eso and T_int are sensitive to elevations in T_core during arm-cycling exercise in men with paraplegia, although T_eso may have superior sensitivity to capture temperature information earlier during exercise.

Effects of exercise interventions on cardiovascular health in individuals with chronic, motor complete spinal cord injury: protocol for a randomised controlled trial [Cardiovascular Health/Outcomes: Improvements Created by Exercise and education in SCI (CHOICES) Study]

INTRODUCTION

Recent studies demonstrate that cardiovascular diseases and associated complications are the leading cause of morbidity and mortality in individuals with spinal cord injury (SCI). Abnormal arterial stiffness, defined by a carotid-to-femoral pulse wave velocity (cfPWV) ≥10 m/s, is a recognised risk factor for heart disease in individuals with SCI. There is a paucity of studies assessing the efficacy of conventional training modalities on arterial stiffness and other cardiovascular outcomes in this population. Therefore, this study aims to compare the efficacy of arm cycle ergometry training (ACET) and body weight-supported treadmill training (BWSTT) on reducing arterial stiffness in individuals with chronic motor complete, high-level (above the sixth thoracic segment) SCI.

METHODS AND ANALYSIS

This is a multicentre, randomised, controlled, clinical trial. Eligible participants will be randomly assigned (1:1) into either ACET or BWSTT groups. Sixty participants with chronic (>1 year) SCI will be recruited from three sites in Canada (Vancouver, Toronto and Hamilton). Participants in each group will exercise three times per week up to 30 min and 60 min for ACET and BWSTT, respectively, over the period of 6 months. The primary outcome measure will be change in arterial stiffness (cfPWV) from baseline. Secondary outcome measures will include comprehensive assessments of: (1) cardiovascular parameters, (2) autonomic function, (3) body composition, (4) blood haematological and metabolic profiles, (5) cardiorespiratory fitness and (6) quality of life (QOL) and physical activity outcomes. Outcome measures will be assessed at baseline, 3 months, 6 months and 12 months (only QOL and physical activity outcomes). Statistical analyses will apply linear-mixed modelling to determine the training (time), group (ACET vs BWSTT) and interaction (time × group) effects on all outcomes.

ETHICS AND DISSEMINATION

Ethical approval was obtained from all three participating sites. Primary and secondary outcome data will be submitted for publication in peer-reviewed journals and widely disseminated.

TRIAL REGISTRATION NUMBER

NCT01718977; Pre-results.

TRIAL STATUS

Recruitment for this study began on January 2013 and the first participant was randomized on April 2013. Recruitment stopped on October 2018.

Clinical and Neurophysiological Changes after Targeted Intrathecal Injections of Bone Marrow Stem Cells in a C3 Tetraplegic Subject

High-level quadriplegia is a devastating condition with limited treatment options. Bone marrow derived stem cells (BMSCs) are reported to have immunomodulatory and neurotrophic effects in spinal cord injury (SCI). We report a subject with complete C2 SCI who received three anatomically targeted intrathecal infusions of BMSCs under a single-patient expanded access investigational new drug (IND). She underwent intensive physical therapy and was followed for >2 years. At end-point, her American Spinal Injury Association Impairment Scale (AIS) grade improved from A to B, and she recovered focal pressure touch sensation over several body areas. We conducted serial neurophysiological testing to monitor changes in residual connectivity. Motor, sensory, and autonomic system testing included motor evoked potentials (MEPs), somatosensory evoked potentials (SSEPs), electromyography (EMG) recordings, F waves, galvanic skin responses, and tilt-table responses. The quality and magnitude of voluntary EMG activations increased over time, but remained below the threshold of clinically obvious movement. Unexpectedly, at 14 months post-injury, deep inspiratory maneuvers triggered respiratory-like EMG bursting in the biceps and several other muscles. This finding means that connections between respiratory neurons and motor neurons were newly established, or unmasked. We also report serial analysis of MRI, International Standards for Neurological Classification of SCI (ISNCSCI), pulmonary function, pain scores, cerebrospinal fluid (CSF) cytokines, and bladder assessment. As a single case, the linkage of the clinical and neurophysiological changes to either natural history or to the BMSC infusions cannot be resolved. Nevertheless, such detailed neurophysiological assessment of high cervical SCI patients is rarely performed. Our findings indicate that electrophysiology studies are sensitive to define both residual connectivity and new plasticity.

Multi-Domain Assessment of Autonomic Function in Spinal Cord Injury Using a Modified Autonomic Reflex Screen

The aim of this study was to characterize autonomic lesions in participants with spinal cord injury (SCI; n = 10) using an autonomic reflex screen, incorporating sudomotor, cardiovagal, and sympathetic adrenergic tests, as well as hemodynamic responses to head-up tilt (HUT). Hemodynamic responses were compared to healthy controls (n = 20) and previously published normative cutoffs in order better identify autonomic impairments. Sympathetic skin responses (SSRs), heart rate response to deep breathing (HR_DB), and heart rate and beat-to-beat blood pressure responses to Valsalva maneuver (VM) and HUT were measured. SCI participants demonstrated impairment in at least one domain, with 7 of 10 demonstrating autonomic impairment across all domains. No single test was concordant with orthostatic hypotension on HUT, in all participants. Measures of cardiovagal function, including HR_DB (SCI = 7.7 ± 3.8 beats/min vs. controls = 17.6 ± 8.1 beats/min) and Valsalva ratio (SCI = 1.53 ± 0.29 vs. controls = 1.85 ± 0.37), were significantly reduced in SCI participants, compared to controls (p < 0.05). These findings suggest that an autonomic reflex screen, which includes standardized testing protocol and normative data for comparison, is useful for determining the autonomic domains affected by the neurological injury in SCI. We also demonstrated significant cardiovagal impairment in SCI participants compared to controls, which warrants further investigation to determine whether cardiovagal dysfunction is associated with the negative cardiovascular outcomes, which are known to occur in SCI.

Sympathetic skin response and heart rate variability in predicting autonomic disorders in patients with Parkinson disease

The purpose of this study was to evaluate sympathetic skin response (SSR) and heart rate variability (HRV) in determining autonomic nervous system (ANS) involvement in patients with Parkinson disease (PD). Forty-eight idiopathic PD patients and 30 healthy controls participated in this study. SSR, HRV, Unified Parkinson's Disease Rating Scale (UPDRS) III, the Scales for outcomes in Parkinson's Disease-Autonomic (SCOPA-AUT), Hoehn and Yahr (H&Y) scale were evaluated. Absent lower limb SSR was determined unilaterally in 2, bilaterally in 1 of 3 advanced PD patients; there was significant difference between PD and control groups in terms of the SSR (P < 0.01), significant prolonged SSR latencies and decreased SSR amplitudes from bilateral hands and feet. Significant difference was noted in HRV between PD and control groups except for root mean square of successive differences (rMSSD) and high-frequency (HF) power (P < 0.05). There was a significant different correlation between the parameters of SSR and the SCOPA-AUT, and between the parameters (except HF power) of HRV and the SCOPA-AUT. Some parameters of SSR were relevantly associated with HRV. The right hand SSR amplitude correlated positively with the (SD) of all R-R interval, total spectral power, very low frequency. The right foot amplitude correlated positively with total spectral power. Both SSR and HRV parameters are sensitive in determining ANS dysfunction not only in late but also in the early stage of PD, which can be used for early detection of autonomic dysfunction in patients with PD and have the potential to serve as electrophysiological markers of dysautonomia of PD.