Autonomic consequences of spinal cord injury

Motor and autonomic concomitant health improvements with neuromodulation and exercise (MACHINE) training: a randomised controlled trial in individuals with spinal cord injury

INTRODUCTION

Motor and autonomic dysfunctions are widespread among people with spinal cord injury (SCI), leading to poor health and reduced quality of life. Exercise interventions, such as locomotor training (LT), can promote sensorimotor and autonomic recovery post SCI. Recently, breakthroughs in SCI research have reported beneficial effects of electrical spinal cord stimulation (SCS) on motor and autonomic functions. Despite literature supporting the independent benefits of transcutaneous SCS (TSCS) and LT, the effect of pairing TSCS with LT is unknown. These therapies are non-invasive, customisable and have the potential to simultaneously benefit both sensorimotor and autonomic functions. The aim of this study is to assess the effects of LT paired with TSCS in people with chronic SCI on outcomes of sensorimotor and autonomic function.

METHODS AND ANALYSIS

Twelve eligible participants with chronic (>1 year) motor-complete SCI, at or above the sixth thoracic segment, will be enrolled in this single-blinded, randomised sham-controlled trial. Participants will undergo mapping for optimisation of stimulation parameters and baseline assessments of motor and autonomic functions. Participants will then be randomly assigned to either LT+TSCS or LT+Sham stimulation for 12 weeks, after which postintervention assessments will be performed to determine the effect of TSCS on motor and autonomic functions. The primary outcome of interest is attempted voluntary muscle activation using surface electromyography. The secondary outcomes relate to sensorimotor function, cardiovascular function, pelvic organ function and health-related quality of life. Statistical analysis will be performed using two-way repeated measures Analysis of variance (ANOVAs) or Kruskal-Wallis and Cohen's effect sizes.

ETHICS AND DISSEMINATION

This study has been approved after full ethical review by the University of British Columbia's Research Ethics Board. The stimulator used in this trial has received Investigation Testing Authorisation from Health Canada. Trial results will be disseminated through peer-reviewed publications, conference presentations and seminars.

TRIAL REGISTRATION NUMBER

NCT04726059.

Exploring 5-minute heart rate variability in spinal cord injury during acute inpatient rehabilitation

To explore the use of 5-minute heart rate variability (HRV) during inpatient rehabilitation in the acute phase of traumatic spinal cord injury (SCI). Longitudinal observational study. Acute inpatient rehabilitation (AIR). 10 patients with acute traumatic SCI. 5-minute HRV supine recordings twice daily on three different days per patient. HRV values were evaluated (1) within a single day (Early versus Late); (2) across the inpatient admission (initial, mid, and discharge); (3) by SCI phenotypes and by clinical outcomes (ex. pressure injuries (PI)). Patients had an average age of 38 years, 80% male, and 40% with tetraplegia. There were no HRV differences between Early and Late recordings, across the inpatient admission, demographics, or SCI phenotype. However, improvement in neurologic exam was accompanied by increased parasympathetic tone (mean RR increased by 172 ms SD 61, P = .005). Patients with PI demonstrated lower sympathetic (SNS) activity (decreased LF by 472 ms² SD 240, P = .049) and lower PNS activity (decreased RMSSD by 1.2 ms SD 0.5, P = .02), compared to no PI. Comparisons to uninjured reference values and chronic SCI suggest a changing autonomic nervous system (ANS) from uninjured to acute to chronic as measured by HRV.

CONCLUSIONS

This preliminary evidence suggests HRV in acute SCI is stable across time and day during inpatient rehabilitation and may be correlated to clinical sequalae of ANS dysfunction and neurologic recovery. Comparisons to published work suggest that HRV may measure the progression in the ANS from acute to chronic phase after SCI.

Longitudinal Impact of Acute Spinal Cord Injury on Clinical Pharmacokinetics of Riluzole, a Potential Neuroprotective Agent

Riluzole, a benzothiazole sodium channel blocker that received US Food and Drug Administration approval to attenuate neurodegeneration in amyotrophic lateral sclerosis in 1995, was found to be safe and potentially efficacious in a spinal cord injury (SCI) population, as evident in a phase I clinical trial. The acute and progressive nature of traumatic SCI and the complexity of secondary injury processes can alter the pharmacokinetics of therapeutics. A 1-compartment with first-order elimination population pharmacokinetic model for riluzole incorporating time-dependent clearance and volume of distribution was developed from combined data of the phase 1 and the ongoing phase 2/3 trials. This change in therapeutic exposure may lead to a biased estimate of the exposure-response relationship when evaluating therapeutic effects. With the developed model, a rational, optimal dosing scheme can be designed with time-dependent modification that preserves the required therapeutic exposure of riluzole.

Association of Autonomic Storming with Urinary Catheter Removal in NMDA Receptor Encephalitis: A Case Report

We present a case of a 47-year-old female who presented with altered mental status and was found to have severe anti-NMDA receptor encephalitis. Her intensive care unit course was complicated by paroxysmal sympathetic storming. She also had urinary retention for which a catheter was placed early in her admission, but attempts at removal were associated with worsening storming. Her average Clinical Features Scale score was 5.9 when the catheter was not in place compared to 3.6 with the catheter in place. This is the first case report to our knowledge demonstrating an association between urinary catheter removal and autonomic storming in anti-NMDA receptor encephalitis.

Exosomes derived from human placental mesenchymal stem cells enhanced the recovery of spinal cord injury by activating endogenous neurogenesis

Background

Spinal cord injury (SCI) is a debilitating medical condition that can result in the irreversible loss of sensorimotor function. Current therapies fail to provide an effective recovery being crucial to develop more effective approaches. Mesenchymal stem cell (MSC) exosomes have been shown to be able to facilitate axonal growth and act as mediators to regulate neurogenesis and neuroprotection, holding great therapeutic potential in SCI conditions. This study aimed to assess the potential of human placental MSC (hpMSC)-derived exosomes on the functional recovery and reactivation of endogenous neurogenesis in an experimental animal model of SCI and to explore the possible mechanisms involved.

Methods

The hpMSC-derived exosomes were extracted and transplanted in an experimental animal model of SCI with complete transection of the thoracic segment. Functional recovery, the expression of neural stem/progenitor cell markers and the occurrence of neurogenesis, was assessed 60 days after the treatment. In vitro, neural stem cells (NSCs) were incubated with the isolated exosomes for 24 h, and the phosphorylation levels of mitogen-activated protein kinase kinase (MEK), extracellular signal-regulated kinases (ERK), and cAMP response element binding (CREB) proteins were assessed by western blot.

Results

Exosomes were successfully isolated and purified from hpMSCs. Intravenous injections of these purified exosomes significantly improved the locomotor activity and bladder dysfunction of SCI animals. Further study of the exosomes’ therapeutic action revealed that hpMSC-derived exosomes promoted the activation of proliferating endogenous neural stem/progenitor cells as denoted by the significant increase of spinal SOX2⁺GFAP⁺, PAX6⁺Nestin⁺, and SOX1⁺KI67⁺ cells. Moreover, animals treated with exosomes exhibited a significative higher neurogenesis, as indicated by the higher percentage of DCX⁺MAP 2⁺ neurons. In vitro, hpMSC-derived exosomes promoted the proliferation of NSCs and the increase of the phosphorylated levels of MEK, ERK, and CREB.

Conclusions

This study provides evidence that the use of hpMSC-derived exosomes may constitute a promising therapeutic strategy for the treatment of SCI.

The Translesional Spinal Network and Its Reorganization after Spinal Cord Injury

Evidence from preclinical and clinical research suggest that neuromodulation technologies can facilitate the sublesional spinal networks, isolated from supraspinal commands after spinal cord injury (SCI), by reestablishing the levels of excitability and enabling descending motor signals via residual connections. Herein, we evaluate available evidence that sublesional and supralesional spinal circuits could form a translesional spinal network after SCI. We further discuss evidence of translesional network reorganization after SCI in the presence of sensory inputs during motor training. In this review, we evaluate potential mechanisms that underlie translesional circuitry reorganization during neuromodulation and rehabilitation in order to enable motor functions after SCI. We discuss the potential of neuromodulation technologies to engage various components that comprise the translesional network, their functional recovery after SCI, and the implications of the concept of translesional network in development of future neuromodulation, rehabilitation, and neuroprosthetics technologies.