Decentralized cardiovascular autonomic control and cognitive deficits in persons with spinal cord injury

Brain activation during the N-back working memory task in individuals with spinal cord injury: a functional near-infrared spectroscopy study

Cognitive impairments have frequently been reported in individuals with spinal cord injury (SCI) across different domains such as working memory, attention, and executive function. The mechanism of cognitive impairment after SCI is not well understood due to the heterogeneity of SCI sample populations, and may possibly be due to factors such as cardiovascular dysfunction, concomitant traumatic brain injury (TBI), hypoxia, sleep disorders, and body temperature dysregulation. In this study, we implement the Neuropsychiatric Unit Cognitive Assessment Tool (NUCOG) to assess cognitive differences between individuals with SCI and age-matched able-bodied (AB) controls. We then use an N-back working memory task and functional near-infrared spectroscopy (fNIRS) to elucidate the neurovascular correlates of cognitive function in individuals with SCI. We observed significant differences between the SCI and AB groups on measures of executive function on the NUCOG test. On the N-back task, across the three levels of difficulty: 0-back, 2-back, and 3-back, no significant differences were observed between the SCI and AB group; however, both groups performed worse as the level of difficulty increased. Although there were no significant differences in N-back performance scores between the two groups, functional brain hemodynamic activity differences were observed between the SCI and AB groups, with the SCI group exhibiting higher maximum oxygenated hemoglobin concentration in the right inferior parietal lobe. These findings support the use of fNIRS to study cognitive function in individuals with SCI and may provide a useful tool during rehabilitation to obtain quantitative functional brain activity metrics.

The Clinical Relevance of Autonomic Dysfunction, Cerebral Hemodynamics, and Sleep Interactions in Individuals Living With SCI

A myriad of physiological impairments is seen in individuals after a spinal cord injury (SCI). These include altered autonomic function, cerebral hemodynamics, and sleep. These physiological systems are interconnected and likely insidiously interact leading to secondary complications. These impairments negatively influence quality of life. A comprehensive review of these systems, and their interplay, may improve clinical treatment and the rehabilitation plan of individuals living with SCI. Thus, these physiological measures should receive more clinical consideration. This special communication introduces the under investigated autonomic dysfunction, cerebral hemodynamics, and sleep disorders in people with SCI to stakeholders involved in SCI rehabilitation. We also discuss the linkage between autonomic dysfunction, cerebral hemodynamics, and sleep disorders and some secondary outcomes are discussed. Recent evidence is synthesized to make clinical recommendations on the assessment and potential management of important autonomic, cerebral hemodynamics, and sleep-related dysfunction in people with SCI. Finally, a few recommendations for clinicians and researchers are provided.

Transcutaneous Spinal Cord Stimulation to Stabilize Seated Systolic Blood Pressure in Persons With Chronic Spinal Cord Injury: Protocol Development

Transcutaneous spinal cord stimulation (tSCS) is an emerging therapeutic strategy to target spinal autonomic circuitry to normalize and stabilize blood pressure (BP) in hypotensive persons living with chronic spinal cord injury (SCI). Our aim is to describe our current methodological approach to identify individual tSCS parameters that result in the maintenance of seated systolic blood pressure (SBP) within a pre-defined target range. The parent study is a prospective, randomized clinical trial in which eligible participants will undergo multiple mapping sessions to optimize tSCS parameter settings to promote stable SBP within a target range of 110-120 mm Hg for males and 100-120 mm Hg for females. Parameter mapping includes cathode electrode placement site (T7/8, T9/10, T11/12, and L1/2), stimulation frequency (30, 60 Hz), current amplitudes (0-120 mA), waveform (mono- and biphasic), pulse width (1000 μs), and use of carrier frequency (0, 10 kHz). Each participant will undergo up to 10 mapping sessions involving different electrode placement sites and parameter settings. BP will be continuously monitored throughout each mapping session. Stimulation amplitude (mA) will be increased at intervals of between 2 and 10 mA until one of the following occurs: 1) seated SBP reaches the target range; 2) tSCS intensity reaches 120 mA; or 3) the participant requests to stop. Secondary outcomes recorded include 1) symptoms related to autonomic dysreflexia and orthostatic hypotension, 2) Likert pain scale, and 3) skin appearance after removal of the tSCS electrode. Clinical Trials Registration: NCT05180227.

Autonomic Cardiovascular Control, Psychological Well-Being, and Cognitive Performance in People With Spinal Cord Injury

PURPOSE

To examine associations between parameters of psychological well-being, injury characteristics, cardiovascular autonomic nervous system (ANS) control, and cognitive performance in persons with spinal cord injury (SCI) compared with age-matched uninjured controls. This is an observational, cross-sectional study including a total of 94 participants (52 with SCI and 42 uninjured controls: UIC). Cardiovascular ANS responses were continuously monitored at rest and during administration of the Paced Auditory Serial Addition Test (PASAT). Self-report scores on the SCI-Quality of Life questionnaires are reported for depression, anxiety, fatigue, resilience, and positive affect. Participants with SCI performed significantly more poorly on the PASAT compared with the uninjured controls. Although not statistically significant, participants with SCI tended to report more psychological distress and less well-being than the uninjured controls. In addition, when compared with uninjured controls, the cardiovascular ANS responses to testing were significantly altered in participants with SCI; however, these responses to testing did not predict PASAT performance. Self-reported levels of anxiety were significantly related to PASAT score in the SCI group, but there was no significant relationship between PASAT and the other indices of SCI-Quality of Life. Future investigations should more closely examine the relationship among cardiovascular ANS impairments, psychological disorders, and cognitive dysfunction to better elucidate the underpinnings of these deficits and to guide interventions aimed at improving physiological, psychological, and cognitive health after SCI. Tetraplegia, paraplegia, blood pressure variability, cognitive, mood.

Cognitive Failure in Adults with Spinal Cord Injury: A Valuable Adjunct Measure for Enhancing Cognitive Assessment and Rehabilitation Outcomes

Cognitive impairment is common in persons with spinal cord injury (SCI), impacting their daily functioning and rehabilitation. This study assesses the extent of self-reported cognitive failures in everyday life in persons with SCI and its relationships with objective neurocognitive measures and psychosocial factors, including depressive mood, anxiety, perceived control, and fatigue. The differences between forty-one adults with a chronic SCI and forty-one able-bodied controls were examined. The participants completed the Cognitive Failures Questionnaire (CFQ) to assess cognitive failure and neurocognitive tests assessing attention and executive functions, as well as a psychosocial assessment. The SCI group reported higher cognitive failure rates than the able-bodied group (31.7% versus 19%, p > 0.05). Objective neurocognitive tests did not significantly correlate with the CFQ scores in either group. However, the CFQ scores were positively associated with most psychosocial factors, even after controlling for covariates. The CFQ scores were significantly associated with depressive mood in persons with SCI. These findings highlight the importance of incorporating self-reported cognitive measures into neurocognitive assessments and rehabilitation planning for adults with SCI. Self-reports capture everyday cognitive challenges that objective tests may miss. Additionally, this study highlights the strong connections between cognitive failures and psychosocial issues, particularly mood disorders, emphasizing the need for comprehensive rehabilitation and psychosocial support post-SCI, addressing both cognitive and emotional wellbeing.

Clinical trial of home blood pressure monitoring following midodrine administration in hypotensive individuals with spinal cord injury

BACKGROUND

Individuals with spinal cord injury (SCI) above thoracic level-6 (T6) experience impaired descending cortical control of the autonomic nervous system which predisposes them to blood pressure (BP) instability, including includes hypotension, orthostatic hypotension (OH), and autonomic dysreflexia (AD). However, many individuals do not report symptoms of these BP disorders, and because there are few treatment options that have been proven safe and effective for use in the SCI population, most individuals remain untreated.

OBJECTIVE

The primary aim of this investigation was to determine the effects of midodrine (10 mg) prescribed TID or BID in the home environment, compared to placebo, on 30-day BP, study withdrawals, and symptom reporting associated with OH and AD in hypotensive individuals with SCI.

DESIGN/METHODS

Participants were randomly assigned to received midodrine/placebo or placebo/midodrine, with a 2-weeks washout period in between, and both the participants and investigators were blinded to randomization order. Study medication was taken 2 or 3 times/day, depending on their sleep/wake schedule, BP, and any related symptoms were recorded before and 1 h after each dosage and periodically throughout the day.

RESULTS

Nineteen individuals with SCI were recruited; however, 9 withdrew prior to completion of the full protocol. A total of 1892 BP recordings (75 ± 48 recordings/participant/30-day period) were collected in the 19 participants over the two 30-day monitoring periods. Average 30-day systolic BP was significantly increased with midodrine compared to placebo (114 ± 14 vs. 96 ± 11 mmHg, respectively; P = 0.004), and midodrine significantly reduced the number of hypotensive BP recordings compared to placebo (38.7 ± 41.9 vs. 73.3 ± 40.6, respectively; P = 0.01). However, compared to placebo, midodrine increased fluctuations in BP, did not improve symptoms of OH, but did significantly worsen the intensity of symptoms associated with AD (P = 0.03).

CONCLUSION

Midodrine (10 mg) administered in the home environment effectively increases BP and reduces the incidence of hypotension; however these beneficial effects come at the expense of worsened BP instability and AD symptom intensity.

Myokines may target accelerated cognitive aging in people with spinal cord injury: A systematic and topical review

Persons with spinal cord injury (SCI) can suffer accelerated cognitive aging, even when correcting for mood and concomitant traumatic brain injury. Studies in healthy older adults have shown that myokines (i.e. factors released from muscle tissue during exercise) may improve brain health and cognitive function. Myokines may target chronic neuroinflammation, which is considered part of the mechanism of cognitive decline both in healthy older adults and SCI. An empty systematic review, registered in PROSPERO (CRD42022335873), was conducted as proof of the lack of current research on this topic in people with SCI. Pubmed, Embase, Cochrane and Web of Science were searched, resulting in 387 articles. None were considered eligible for full text screening. Hence, the effect of myokines on cognitive function following SCI warrants further investigation. An in-depth narrative review on the mechanism of SCI-related cognitive aging and the myokine-cognition link was added to substantiate our hypothetical framework. Readers are fully updated on the potential role of exercise as a treatment strategy against cognitive aging in persons with SCI.

Effects of trunk muscle activation on trunk stability, arm power, blood pressure and performance in wheelchair rugby players with a spinal cord injury

Objective: In wheelchair rugby (WR) athletes with tetraplegia, wheelchair performance may be impaired due to (partial) loss of innervation of upper extremity and trunk muscles, and low blood pressure (BP). The objective was to assess the effects of electrical stimulation (ES)-induced co-contraction of trunk muscles on trunk stability, arm force/power, BP, and WR performance.Design: Cross-sectional study.Setting: Rehabilitation research laboratory and WR court.Participants: Eleven WR athletes with tetraplegia.Interventions: ES was applied to the rectus abdominis, obliquus externus abdominis and erector spinae muscles. For every test, the ES condition was compared to the non-ES condition.Outcome measures: Stability was assessed with reaching tasks, arm force/power with an isokinetic test on a dynamometer, BP during an ES protocol and WR skill performance with the USA Wheelchair Rugby Skill Assessment.Results: Overall reaching distance (ES 14.6 ± 7.5 cm, non-ES 13.4 ± 8.2 cm), and BP showed a significant increase with ES. Arm force (ES 154 ± 106 N, non-ES 148 ± 102 N) and power (ES 37 ± 26 W, non-ES 36 ± 25 W), and WR skills were not significantly improved.Conclusion: ES-induced trunk muscle activation positively affects trunk stability and BP, but not arm force/power. No effects were found in WR skill performance, probably due to abdominal strapping. More research is needed to assess different ES (training) protocols and longitudinal effects.

Does lack of brain injury mean lack of cognitive impairment in traumatic spinal cord injury?

OBJECTIVE

Traumatic spinal cord injury (tSCI) has implications in many areas, including cognitive functioning. Findings regarding cognitive problems in people with SCI are inconsistent, presumably due to multiple variables than can affect performance, among them emotional variables. The purpose of the current study was to elucidate cognitive sequalae in some individuals with tSCI with no medical record of brain injury, while taking emotional variables into consideration.

DESIGN

Cross-sectional, with two groups.

SETTING

A public rehabilitation center.

PARTICIPANTS

Twenty participants with tSCI at least ten months post injury and twenty non-SCI controls, matched for sex, age, and education.

INTERVENTION

None.

OUTCOME MEASURES

A battery of neuropsychological tests tapping executive functions, memory, attention, and naming abilities, in addition to questionnaires assessing depression and distress.

RESULTS

When emotional variables were statistically controlled, participants with tSCI showed higher levels of depression and distress and scored lower than non-SCI control participants on all cognitive tests except naming. Executive functions were found to have the highest effect size, though no specific ability was sensitive enough to differentiate between the groups in a binary logistic regression analysis.

CONCLUSION

In some individuals with chronic tSCI, lower cognitive ability that is unrelated to emotional distress might result from spinal cord damage and its implications in a population who's medical records show no indication of brain injury. This highlights the importance of conducting cognitive evaluation following SCI, so that deficits can be effectively addressed during rehabilitation.

Management of blood pressure disorders in individuals with spinal cord injury

Blood pressure regulation is impacted by a spinal cord injury (SCI) due to impaired descending sympathetic vascular control. Common blood pressure problems in the SCI population include persistently low blood pressure with bouts of orthostatic hypotension and autonomic dysreflexia, which are more prevalent in individuals with lesions above the sixth thoracic vertebral level; however, they may occur regardless of the neurological level of injury. Although blood pressure disorders adversely impact daily function and quality of life, most individuals with SCI do not acknowledge this association. Few pharmacological options have been rigorously tested for safety and efficacy to manage blood pressure disorders in the SCI population. Furthermore, clinical management of any one blood pressure disorder may adversely impact others, as such treatment is complicated and not often prioritized.

Elevated Serum Neuropeptide FF Levels Are Associated with Cognitive Decline in Patients with Spinal Cord Injury

BACKGROUND

Spinal cord injury (SCI) has high incidence globally and is frequently accompanied by subsequent cognitive decline. Accurate early risk-categorization of SCI patients for cognitive decline using biomarkers can enable the timely application of appropriate neuroprotective measures and the development of new agents for the management of SCI-associated cognitive decline. Neuropeptide FF is an endogenous neuropeptide with a multitude of functions and is associated with neuroinflammatory processes. This prospective study investigated the predictive value of serum neuropeptide FF levels measured after acute SCI for subsequent cognitive decline.

METHODS

88 patients presenting with acute SCI without preexisting neurological injury, brain trauma, or severe systemic illness and 60 healthy controls were recruited. Serum neuropeptide FF levels, clinical, and routine laboratory variables including low-density lipoprotein, high-density lipoprotein, fasting blood glucose, total triiodothyronine (TT3), total thyroxine (TT4), and thyroid-stimulating hormone (TSH) levels collected from all subjects were assessed. Montreal cognitive assessment (MoCA) was performed 3 months after enrollment. SCI patients were grouped according to quartile of serum neuropeptide FF level and MoCA scores were compared using ANOVA. Additionally, multivariate linear regression with clinical and laboratory variables was performed to predict MoCA scores.

RESULTS

SCI patients displayed significantly higher baseline serum neuropeptide FF levels than healthy controls (38.5 ± 4.1 versus 23.4 ± 2.0 pg/ml, p < 0.001∗∗). SCI patients in higher quartiles of baseline serum neuropeptide FF displayed significantly lower MoCA scores at 3 months. Linear regression analysis indicated serum neuropeptide FF levels as a significant independent predictor of worse MoCA scores after SCI (r = 0.331, p = 0.034∗).

CONCLUSION

Early serum neuropeptide FF levels significantly and independently predicted cognitive decline after acute SCI among patients without preexisting neurological disorders.

Cognitive Impairment in Adult Patients with 5q-Associated Spinal Muscular Atrophy

In previous studies, a below-average, average, or above-average intelligence quotient (IQ) in children with SMA was detected but, aside from a severe physical disability, the cognitive performance of adult SMA patients has not yet been evaluated. The intelligence test used in this study, the Wechsler Adult Intelligence Scale, fourth edition (WAIS-IV), was used to measure major intelligence components of adult SMA patients. The WAIS-IV determines four index scores representing verbal comprehension, perceptual reasoning, working memory, and processing speed. Due to time-dependent demands on motor function, the processing speed index score was excluded. IQ index scores of 33 adult SMA patients did not differ from IQ index scores of the normal population. In SMA type-3 patients, the index scores for verbal comprehension, perceptual reasoning, and working memory did not differ from the normal population but showed a trend of IQ scores towards lower points. Patients with SMA type 2 had lower IQ index scores for working memory (90.33 ± 12.95; p = 0.012) and perceptual reasoning (90.73 ± 12.58; p = 0.013) than the normal population. This study provided further evidence that SMA is a multi-systemic disease and may refute the widespread hypothesis that SMA patients might improve their cognitive skills to compensate for their physical impairment.

Autonomic cardiovascular dysfunction during simple arithmetic test in a patient with cervical spinal cord injury-a case report

INTRODUCTION

Spinal cord injury (SCI) disrupts autonomic control of the cardiovascular system, which may lead to autonomic dysfunction. Growing amounts of evidence support the possibility that systemic and cerebral hemodynamic dysfunctions may contribute to cognitive deficits in patients with SCI.

CASE PRESENTATION

We present a case of autonomic cardiovascular dysfunction in a 55-year old female patient following non-traumatic cervical SCI. This case illustrates how a simple arithmetic test may elicit fluctuations in blood pressure causing cognitive disturbances.

DISCUSSION

Clinical awareness of autonomic dysfunction and cognitive deficits is relevant in neurorehabilitation of patients with SCI. Assessment of autonomic function should be evaluated according to recommendation from International Standards to document remaining Autonomic Function after Spinal Cord Injury (ISAFSCI) [1].

Graph theoretical structural connectome analysis of the brain in patients with chronic spinal cord injury: preliminary investigation

STUDY DESIGN

Retrospective study.

OBJECTIVES

We aimed to characterize the convergent disruptions of the structural connectivity based on network modeling technique (i.e., graph theory) to identify significant changes in network organization/reorganization between uninjured and chronic spinal cord injury (SCI) participants.

SETTING

USA.

METHODS

Ten adult participants including 4 with chronic SCI and 6 uninjured were scanned using a multi-shell diffusion imaging on a 3.0 T MR scanner. Whole brain structural connectivity matrix was estimated by performing the quantification of the number of white matter fibers (called edges) connecting each possible pair of brain region (called nodes). Brain regions were defined according to Desikan-Killiany cortical atlas. Using connectivity matrix, connectivity strength as well as six different graph theoretical measurements were computed for each participant. They include: (1) global efficiency; (2) local efficiency; (3) degree; (4) betweenness centrality; (5) average shortest length and (6) clustering coefficient. Finally network based statistics was applied to extract nodes/connections with significant differences between groups (uninjured vs SCI).

RESULTS

The SCI group showed significant decreases in betweenness centrality in the left precentral gyrus (T-score=2.98, p value=0.02), and the right caudal middle frontal gyrus (score = 2.35, p value=0.047). It also showed significant decrease in left transverse temporal gyrus (T-score=2.36, p value=0.046) in clustering coefficient. In addition, altered regions in the occipital and parietal lobe were also identified.

CONCLUSION

These results suggest that not only local but also global alterations of the white matter occur after SCI. The proposed modeling technique has the potential to serve as a screening tool to identify any areas of the brain affected after SCI.

Neuropsychological Study in Patients with Spinal Cord Injuries

The present investigation was designed to determinate the nature, pattern, and extent of cognitive deficits in a group of participants with subacute and chronic spinal cord injury (SCI). Methods: A cross-sectional study was conducted in both patients with subacute and chronic SCI. Different cognitive functions were evaluated through a neuropsychological protocol designed for this purpose, taking into account the patient’s emotional state. Results: A total of 100 patients suffering a spinal cord injury were evaluated. There were no differences between the two groups when age, sex, level of education, and region of origin were studied. The chronic injured patients obtained lower scores in the neuropsychological evaluation protocol respective to the subacute injured patients. Conclusions: Subjects with chronic spinal cord injury presented a cognitive profile that differed greatly in the number of altered cognitive functions as well as in their magnitude from the subacute spinal cord injured patient profile. Moreover, cognitive dysfunction may be important beyond the end of the first stage of rehabilitation as it can affect an individual’s quality of life and possible integration in society.

Multidimensional review of cognitive impairment after spinal cord injury

Cognitive impairment is highly prevalent in the population with spinal cord injury (SCI) and exerts a significant impact on functional independence and quality of life in this population. A number of neuroscientists have conducted preliminary investigations of cognitive deficits after SCI, but achieved marginally contradictory results due to some limitations such as the heterogeneity in the sample population, sample size, types of tests utilized, study design, and time since SCI. Therefore, this review mainly focuses on the characteristics, assessments, potential causality and treatment of cognitive impairment for better understanding such deficits in the SCI population.

Beneficial Cardiac Structural and Functional Adaptations After Lumbosacral Spinal Cord Epidural Stimulation and Task-Specific Interventions: A Pilot Study

Cardiac myocyte atrophy and the resulting decreases to the left ventricular mass and dimensions are well documented in spinal cord injury. Therapeutic interventions that increase preload can increase the chamber size and improve the diastolic filling ratios; however, there are no data describing cardiac adaptation to chronic afterload increases. Research from our center has demonstrated that spinal cord epidural stimulation (scES) can normalize arterial blood pressure, so we decided to investigate the effects of scES on cardiac function using echocardiography. Four individuals with chronic, motor-complete cervical spinal cord injury were implanted with a stimulator over the lumbosacral enlargement. We assessed the cardiac structure and function at the following time points: (a) prior to implantation; (b) after scES targeted to increase systolic blood pressure; (c) after the addition of scES targeted to facilitate voluntary (i.e., with intent) movement of the trunk and lower extremities; and (d) after the addition of scES targeted to facilitate independent, overground standing. We found significant improvements to the cardiac structure (left ventricular mass = 10 ± 2 g, p < 0.001; internal dimension during diastole = 0.1 ± 0.04 cm, p < 0.05; internal dimension during systole = 0.06 ± 0.03 cm, p < 0.05; interventricular septum dimension = 0.04 ± 0.02 cm, p < 0.05), systolic function (ejection fraction = 1 ± 0.4%, p < 0.05; velocity time integral = 2 ± 0.4 cm, p < 0.001; stroke volume = 4.4 ± 1.5 ml, p < 0.01), and diastolic function (mitral valve deceleration time = -32 ± 11 ms, p < 0.05; mitral valve deceleration slope = 50 ± 25 cm s-1, p < 0.05; isovolumic relaxation time = -6 ± 1.9 ms, p < 0.05) with each subsequent scES intervention. Despite the pilot nature of this study, statistically significant improvements to the cardiac structure, systolic function, and diastolic function demonstrate that scES combined with task-specific interventions led to beneficial cardiac remodeling, which can reverse atrophic changes that result from spinal cord injury. Long-term improvements to cardiac function have implications for increased quality of life and improved cardiovascular health in individuals with spinal cord injury, decreasing the risk of cardiovascular morbidity and mortality.

Longitudinal Assessment of Autonomic Function during the Acute Phase of Spinal Cord Injury: Use of Low-Frequency Blood Pressure Variability as a Quantitative Measure of Autonomic Function

High-level spinal cord injury (SCI) can disrupt cardiovascular autonomic function. However, the evolution of cardiovascular autonomic function in the acute phase following injury is unknown. We evaluated the timing, severity, progression, and implications of cardiovascular autonomic injury following acute SCI. We tested 63 individuals with acute traumatic SCI (aged 48 ± 2 years) at five time-points: <2 weeks, and 1, 3, 6-12, and >12 months post-injury. Supine beat-to-beat systolic arterial pressure (SAP) and R-R interval (RRI) were recorded and low-frequency variability (LF SAP and LF RRI) determined. Cross-spectral analyses were used to determine baroreflex function (low frequency) and cardiorespiratory interactions (high frequency). Known electrocardiographic (ECG) markers for arrhythmia and self-reported symptoms of cardiovascular dysfunction were determined. Comparisons were made with historical data from individuals with chronic SCI and able-bodied controls. Most individuals had high-level (74%) motor/sensory incomplete (63%) lesions. All participants had decreased LF SAP at <2 weeks (2.22 ± 0.65 mm Hg²). Autonomic injury was defined as high-level SCI with LF SAP <2 mm Hg². Two distinct groups emerged by 1 month: autonomically complete SCI with sustained low LF SAP (0.76 ± 0.17 mm Hg²) and autonomically incomplete SCI with increased LF SAP (5.46 ± 1.0 mm Hg², p < 0.05). Autonomically complete injuries did not recover over time. Cardiovascular symptoms were prevalent and worsened with time, especially in those with autonomically complete lesions, and chronic SCI. Baroreflex function and cardiorespiratory interactions were impaired after SCI. Risk of arrhythmia increased immediately after SCI, and remained elevated throughout the acute phase. Acute SCI is associated with severe cardiovascular dysfunction. LF SAP provides a simple, non-invasive, translatable, quantitative assessment of autonomic function, and is most informative 1 month after injury.

Heart rate and blood pressure response improve the prediction of orthostatic cardiovascular dysregulation in persons with chronic spinal cord injury

Unstable blood pressure after spinal cord injury (SCI) is not routinely examined but rather predicted by level and completeness of injury (i.e., American Spinal Injury Association Impairment Scale AIS classification). Our aim was to investigate hemodynamic response to a sit-up test in a large cohort of individuals with chronic SCI to better understand cardiovascular function in this population. Continuous blood pressure and ECG were recorded from individuals with SCI (n = 159) and non-injured individuals (n = 48). We found orthostatic hypotension occurred within each level and AIS classification (n = 36). Moreover, 45 individuals with chronic SCI experienced a drop in blood pressure that did not meet the criteria for orthostatic hypotension, but was accompanied by dramatic increases in heart rate, reflecting orthostatic intolerance. A cluster analysis of hemodynamic response to a seated position identified eight distinct patterns of interaction between blood pressure and heart rate during orthostatic stress indicating varied autonomic responses. Algorithmic cluster analysis of heart rate and blood pressure is more sensitive to diagnosing orthostatic cardiovascular dysregulation. This indicates blood pressure instability cannot be predicted by level and completeness of SCI, and the consensus statement definition of orthostatic hypotension is insufficient to characterize the variability of blood pressure and heart rate responses during orthostatic stress. Both blood pressure and heart rate responses are needed to characterize autonomic function after SCI.

The Neural Mechanisms Underlying Processing Speed Deficits in Individuals Who Have Sustained a Spinal Cord Injury: A Pilot Study

Our objective was to determine differences in brain activation during a processing-speed task in individuals with SCI compared to a group of age-matched healthy controls and to a group of older healthy controls. Ten individuals with cervical SCI (C3-C5), 10 age-matched healthy controls and 10 older healthy controls participated in a cross-sectional study in which performance on neuropsychological tests of processing speed and brain activation were the main outcome measures. The brain areas used by the individuals with SCI during the processing-speed task differed significantly from the age-matched healthy controls, but were similar to the older control cohort, and included activation in frontal, parietal and hippocampal areas. This suggests that individuals with SCI may compensate for processing-speed deficits by relying on brain regions that classically support control cognitive processes such as executive control and memory.

A prospective cohort study investigating contributors to mild cognitive impairment in adults with spinal cord injury: study protocol

BACKGROUND

Studies report rates of mild cognitive impairment (MCI) in spinal cord injury (SCI) range between 10 and 60%. This broad estimate of MCI in SCI is most likely a result of: (i) inconsistent operationalization of MCI; (ii) heterogeneity among individuals with SCI; (iii) failure to account for MCI subtypes, thereby adding to the heterogeneity of samples; and, (iv) poor control for traumatic brain injury (TBI) that obscures differentiation of MCI attributable to TBI versus other factors. There is a paucity of longitudinal studies following the course of MCI in SCI, and none that account for multiple predictors of MCI, including interactions among predictors.

METHODS

An inception cohort longitudinal study will assess approximately 100 individuals aged 17-80 years with acute SCI, with measures taken at three timepoints (baseline, 3 months post-baseline, and 12 months post-injury). Data relevant to medical care received within the first 24-48 h of presentation to the emergency department will be analysed, as will measures of cognition, injury characteristics, medical history, personal factors, psychological status, psychosocial functioning, and quality of life. Latent class mixture modelling will determine trajectories for the primary outcome of interest, cognitive functioning and its subtypes, and secondary outcomes of interest such as depression. Multiple regression analyses will identify predictors of MCI and its subtypes.

DISCUSSION

The prospective design will reveal change in cognitive functioning across time and unveil different outcome trajectories; thus addressing the lack of knowledge on trajectories of MCI and MCI subtypes in SCI. Through subtyping MCI, we hope to yield groups of cognitively impaired individuals with SCI that are potentially more homogenous and thereby stable and predictable. This is the first study to capture emergency department and acute care diagnostic evidence of mild TBI, which has been poorly controlled in previous studies. Our study will also be the first to distinguish the contribution of TBI from other factors to the development of MCI in individuals with SCI.

TRIAL REGISTRATION

The study was prospectively registered with the Australian and New Zealand Clinical Trial Registry ( ACTRN12619001702101 ) on 3rd December 2019.

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.

The impact of level of injury on patterns of cognitive dysfunction in individuals with spinal cord injury

Context: While it is well recognized that physical and physiological changes are more prominent in individuals with higher neurologic levels of spinal cord injury (SCI), the impact of level of lesion on cognition is less clear. Design: Cross-sectional, 3-group. Setting: Non-profit rehabilitation research foundation. Participants: 59 individuals with SCI (30 with tetraplegia, 29 with paraplegia) and 30 age-matched healthy controls (HC). Interventions: None. Outcome Measures: Neuropsychological tests in the domains of attention, working memory, processing speed, executive control, and learning and memory. Results: Results indicated significantly lower test performance in individuals with paraplegia on new learning and memory testing compared to HC. In contrast, compared to HC the group with tetraplegia, showed a significantly impaired performance on a processing speed task, and both the tetraplegia and the paraplegia groups were similarly impaired on a verbal fluency measure. SCI groups did not differ on any cognitive measure. Conclusion: Individuals with SCI may display different patterns of cognitive performance based on their level of injury.

Cognitive Dysfunction in Persons with Chronic Spinal Cord Injuries

Cognitive dysfunction (CD) is pervasive in individuals who have chronic spinal cord injuries (SCI). Although classically associated with concomitant traumatic brain injuries, many other causes have been proposed, including premorbid neuropsychological conditions, mood disorders, substance abuse, polypharmacy, chronic pain and fatigue, sleep apnea, autonomic dysregulation, post-intensive care unit syndrome, cortical reorganizations, and neuroinflammation. The consequences of CD are likely widespread, affecting rehabilitation and function. CD in those with SCI should be recognized, and potentially treated, in order to provide the best patient care.

Physiologic and behavioural signs during a dental appointment in children and teenagers with Cerebral Palsy: a comparative cross-sectional study

AIM

To evaluate the heart rate (HR) and behaviour of children and teenagers with Cerebral Palsy (CP) when having a dental appointment.

METHODS

A comparative cross-sectional study was carried out with 60 participants with CP, between 2 and 14 years old (study group-SG), and 60 normotypical individuals (CG). The sample was paired according to age, gender and socioeconomic status. Behaviour was evaluated during dental prophylaxis using the Frankl Scale, and HR was measured at five moments: before the appointment, when sitting in the dental chair, during the clinical examination, during prophylaxis and immediately after prophylaxis. Mann-Whitney, Friedman and Chi-square tests were applied at a significance level of 5%.

RESULTS

SG presented significantly higher HR (p < 0.001) and more participants with uncooperative behaviour (p < 0.001) than CG in all observational periods. Furthermore, SG participants with uncooperative behaviour presented higher HR values than those in SG who were cooperative in all observational periods (p ≤ 0.002).

CONCLUSIONS

Individuals with CP have a higher HR before and during the clinical session, and are frequently more uncooperative with the procedure than normotypical individuals.

Modulation of left ventricular diastolic filling during exercise in persons with cervical motor incomplete spinal cord injury

PURPOSE

To characterize left ventricular diastolic function during an exertional challenge in adults with incomplete cervical spinal cord Injury (icSCI).

METHODS

In this cross-sectional study, a two-group convenience sample was used to compare left ventricular LV diastolic performance during a 5-10 W·min-1 incremental arm ergometer exercise protocol, using bioimpedance cardiography. Subjects were eight males with cervical incomplete spinal cord injury (icSCI; C5-C7: age 39 ± 14 years) versus eight able-bodied males (CON: age 38 ± 13 years). Left ventricular (LV) diastolic indices included end-diastolic volume (EDV) and early diastolic filling ratio (EDFR). LV ejection time (LVET), inotropic index (dZ/dT2) and stroke volume (SV) were compared between the groups at peak exercise, and maximum workload for the icSCI group (isomax).

RESULTS

EDV (at peak exercise:131.4 ± 7.3 vs 188.78 ± 9.4, p < 0.001; at isomax: 131.4 ± 7.3 vs 169 ± 23, p = 0.0009) and EDFR (at peak exercise 73 ± 14% vs 119 ± 11%, p = 0.006; at isomax 94 ± 10; p = 0.009) were significantly reduced in icSCI compared to CON, respectively. Significant differences in LVET (icSCI: 273 ± 48 vs CON: 305 ± 68; p = 0.1) and dZ/dT2 (icSCI: 0.64 ± 0.11 vs CON: 0.85 ± 0.31; p = 0.1) were not observed at isomax, despite a significant decrease in SV in the subjects with icSCI (77.1 ± 6.05 mL vs 105.8 ± 9.2 mL, p < 0.00) CONCLUSION: Left ventricular filling was impaired in the subjects with icSCI as evidenced at both peak exercise and isomax. It is likely that restrictions on the skeletal muscle pump mechanized the impairment but increased left ventricular wall stiffness could not be excluded as a mediator.

Diverse cognitive impairment after spinal cord injury is associated with orthostatic hypotension symptom burden

This study: 1) compared cognitive functioning between individuals with chronic (>1 year) spinal cord injury (SCI) and non-injured controls and, 2) assessed associations between symptoms of autonomic dysreflexia and orthostatic hypotension with cognitive functioning in SCI participants with a history of unstable blood pressure (BP). Thirty-two individuals with SCI (C4-L2, American Spinal Injury Association Impairment Scale A-D) and thirty age, sex-matched non-injured controls participated in this study. Participants completed a motor-free neuropsychological test battery assessing 1) memory, 2) attention/concentration/psychomotor speed and, 3) executive function. Nineteen participants with SCI who had injuries ≥T6 and a history of unstable BP also completed the Autonomic Dysfunction Following Spinal Cord Injury (ADFSCI) questionnaire. Cognitive function was significantly lower in people with SCI across measures of memory and executive function compared to non-injured controls. Significant, moderate-to-large associations were observed between cumulative (frequency x severity) orthostatic hypotension and total BP instability symptoms scores, with measures of attention/concentration/psychomotor speed and executive function. These data demonstrate a 10 - 65% reduced performance across specific realms of cognitive functioning in individuals with SCI relative to non-injured controls. Furthermore, cumulative subjective scores for symptoms of unstable BP were associated with diverse cognitive deficits. These findings, in individuals without co-occurring traumatic brain injury, imply cardiovascular dysregulation plays a role in cognitive deficits observed in this population.

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.

Cognitive function after spinal cord injury: A systematic review

OBJECTIVE

To systematically examine the incidence of cognitive impairment in individuals with spinal cord injury (SCI), as well as identify potential contributing and confounding factors.

METHODS

Studies quantitatively reporting cognitive ability after spinal cord injury were searched electronically via Medline, CINAHL, Embase, and PsycINFO. Manual screening for references within articles was also performed. A total of 2,481 studies were screened and a total of 70 were included in this review, 21 reporting cognitive function after SCI compared to an able-bodied control group and 49 with no able-bodied controls. Studies were analyzed for the incidence of impairment and the interactions with concomitant traumatic brain injury, psychological or somatic complaints, decentralized cardiovascular control, sleep apnea, neurologic level of injury, and age.

RESULTS

There is a high volume of evidence reporting substantial cognitive impairment in individuals with SCI. Potential co-contributors include concomitant brain injury, psychological or somatic comorbidities, decentralized cardiovascular control, and sleep apnea. Cognitive functioning was negatively correlated with age. No clear agreement was found for the incidence of cognitive impairment or its association with level of injury.

CONCLUSION

Current evidence suggests that individuals with SCI should be examined and addressed for cognitive impairment. Future studies aimed at identifying potential secondary causative factors should employ stringent controls for co-occurring brain trauma since it appears to be a major contributor and confounder to impaired cognition.

Association between head injury and concussion with retinal vessel caliber

The adverse long-term consequences following traumatic brain injury are poorly understood, particularly on the cerebral microvasculature. Retinal vessels are a surrogate marker of cerebral vascular changes. We therefore aimed to examine the cross-sectional association between serious head injury or being knocked unconscious, and/or concussion and retinal microvascular signs, specifically, mean retinal arteriolar and venular calibre, in older adults after accounting for potential confounders. This cohort study involved 2,624 adults with mean age of 66.9 (±9.1) years who self-reported head injury and concussion parameters, and had gradable retinal photographs. Face-to-face interviews with trained interviewers allowed participants to report prior serious head injury or being knocked unconscious, and/or a previous diagnosis of concussion by a medical professional. Fundus photographs were taken and retinal vascular calibre measured using computer-assisted techniques and summarized. There were 25.9%, 15.3% and 10.1% who reported a prior serious head injury or being “knocked unconscious”, concussion, and both, respectively. Participants in the first group compared to non-injured participants had significantly wider (~2 μm) mean retinal venular calibre (p = 0.02), after adjusting for age, sex, smoking, body mass index, mean arterial blood pressure, type 2 diabetes and fellow vessel calibre. No significant associations were observed in people reporting medically diagnosed concussion or with mean retinal arteriolar calibre. Our exploratory study suggests that head injury is independently associated with wider retinal venular caliber. These findings warrant further investigation in longitudinal cohort studies.

A Community Perspective on Bowel Management and Quality of Life after Spinal Cord Injury: The Influence of Autonomic Dysreflexia

Autonomic dysfunction is common in individuals with spinal cord injury (SCI) and leads to numerous abnormalities, including profound cardiovascular and bowel dysfunction. In those with high-level lesions, bowel management is a common trigger for autonomic dysreflexia (AD; hypertension provoked by sensory stimuli below the injury level). Improving bowel care is integral for enhancing quality of life (QoL). We aimed to describe the relationships between bowel care, AD, and QoL in individuals with SCI. We performed an online community survey of individuals with SCI. Those with injury at or above T7 were considered at risk for AD. Responses were received from 287 individuals with SCI (injury levels C1-sacral and average duration of injury 17.1 ± 12.9 [standard deviation] years). Survey completion rate was 73% (n = 210). Bowel management was a problem for 78%: it interfered with personal relationships (60%) and prevented staying (62%) and working (41%) away from home. The normal bowel care duration was >60 min in 24% and most used digital rectal stimulation (59%); 33% reported bowel incontinence at least monthly. Of those at risk for AD (n = 163), 74% had AD symptoms during bowel care; 32% described palpitations. AD interfered with activities of daily living in 51%. Longer durations of bowel care (p < 0.001) and more severe AD (p = 0.04) were associated with lower QoL. Bowel management is a key concern for individuals with SCI and is commonly associated with symptoms of AD. Further studies should explore ways to manage bowel dysfunction, increase self-efficacy, and ameliorate the impact of AD to improve QoL.

Wavelet decomposition analysis is a clinically relevant strategy to evaluate cerebrovascular buffering of blood pressure after spinal cord injury

The capacity of the cerebrovasculature to buffer changes in blood pressure (BP) is crucial to prevent stroke, the incidence of which is three- to fourfold elevated after spinal cord injury (SCI). Disruption of descending sympathetic pathways within the spinal cord due to cervical SCI may result in impaired cerebrovascular buffering. Only linear analyses of cerebrovascular buffering of BP, such as transfer function, have been used in SCI research. This approach does not account for inherent nonlinearity and nonstationarity components of cerebrovascular regulation, often depends on perturbations of BP to increase the statistical power, and does not account for the influence of arterial CO₂ tension. Here, we used a nonlinear and nonstationary analysis approach termed wavelet decomposition analysis (WDA), which recently identified novel sympathetic influences on cerebrovascular buffering of BP occurring in the ultra-low-frequency range (ULF; 0.02-0.03Hz). WDA does not require BP perturbations and can account for influences of CO₂ tension. Supine resting beat-by-beat BP (Finometer), middle cerebral artery blood velocity (transcranial Doppler), and end-tidal CO₂ tension were recorded in cervical SCI ( n = 14) and uninjured ( n = 16) individuals. WDA revealed that cerebral blood flow more closely follows changes in BP in the ULF range ( P = 0.0021, Cohen's d = 0.89), which may be interpreted as an impairment in cerebrovascular buffering of BP. This persisted after accounting for CO₂. Transfer function metrics were not different in the ULF range, but phase was reduced at 0.07-0.2 Hz ( P = 0.03, Cohen's d = 0.31). Sympathetically mediated cerebrovascular buffering of BP is impaired after SCI, and WDA is a powerful strategy for evaluating cerebrovascular buffering in clinical populations.

Use of ambulatory blood pressure monitoring in adolescents with SCI: a case series

Introduction

Due the impact of maturation on cardiovascular hemodynamics the degree of cardiovascular dysfunction, attributable to spinal cord injury (SCI), in the pediatric and adolescent population remains unclear. While few studies have begun to assess this, there is still a void in the literature regarding the prevalence of cardiovascular dysfunction and how best to identify and treat it in this population.

Case presentation

The purpose of this case series is to present the cardiovascular profile of three adolescent patients with chronic SCI, ages 14-16, following 2 or 3 days of 24-h Ambulatory Blood Pressure Monitoring (ABPM).

Discussion

We found that there are variations across the different cases in most cardiovascular hemodynamic categories and a clarification of the International Standards to document remaining Autonomic Function after Spinal Cord Injury (ISAFSCI) may be needed to accurately identify the remaining autonomic cardiovascular function in the adolescent SCI population.

[Experimental study of urinary center change in pons after conus medullaris injury in rats]

Objective

To observe the structural changes of urinary center and the expression of Bcl-2 after conus medullaris injury in rats brain so as to explore the possible influence factors of degeneration in brain.

Methods

Thirty-six adult Sprague-Dawley rats were randomly divided into experimental group ( n=30) and control group ( n=6). In the experimental group, the conus medullaris injury model was established by cutting off the spinal nerve below L ₄, and no treatment was done in the control group. The modeling operations in the experimental group were successful, and 2 rats died at 3 months and 5 months after modeling operation respectively, which may be caused by renal failure or urinary tract infection. In the experimental group, 6, 6, 6, 5, and 5 rats were killed at 1 day, 1 week, and 1, 3, 6 months after operation respectively, and 1 rat was killed at each time point in the control group. The dorsolateral tissue of the pontine tegmentum was harvested to perform HE staining and Bcl-2 immunohistochemical SP staining.

Results

HE staining showed that there was no obvious difference between the experimental group and the control group at 1 day after operation, the neurons were densely packed, arranged neatly, and the nucleoli were clear; at 1 week, the space between the neurons in the experimental group were slightly widened; at 1 month, nucleus retraction in some neurons happened in the experimental group; at 3 and 6 months, the nuclei in the experimental group were more and more condensed, and even some cells disappeared. Bcl-2 immunohistochemical SP staining showed that the expression of Bcl-2 in the control group was weakly positive. The positive expression of Bcl-2 was found at 1 day after operation in the experimental group; the positive expression of Bcl-2 at 7 days after operation was significantly higher than that in the control group, and reached the peak; the positive expression of Bcl-2 decreased gradually at 1, 3, and 6 months after modeling operation, but it was still higher than that of the control group.

Conclusion

The urinary center appears structure degeneration and necrocytosis after conus medullaris injury in rats brain. The elevated expression of Bcl-2 may be associated with brain tissue repair and function remodeling.

The course and prognostic factors of cognitive status after central nervous system trauma: a systematic review protocol

INTRODUCTION

Traumatic brain injury (TBI) is among the most disabling injuries, resulting in a range of cognitive impairments. Traumatic spinal cord injury (SCI) often occurs in conjunction with TBI; the two are best considered together in the context of trauma to the central nervous system (CNS). Despite strong indications of cognitive dysfunction in CNS trauma, little is known about its natural history or relationship with other factors. The current protocol outlines a strategy for a systematic review of the current evidence examining CNS trauma as a prognostic factor of cognitive decline in the adult population.

METHODS AND ANALYSIS

The review will be conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. All peer-reviewed English language publications with a longitudinal design that focus on cognition in adults (ages 18 and older) with either TBI or SCI, or both from inception to December 2016 found through Medline, Central, Embase, Scopus, PsycINFO, supplemental PubMed and bibliographies of identified articles will be considered eligible. Quality will be evaluated using published guidelines. Results will be grouped by: (1) prognostic factors of cognitive deficits; and (2) development of, or time until development of, cognitive deficit in patients with CNS trauma. Close attention will be paid to the evaluative properties of the measurements used to assess cognition.

ETHICS AND DISSEMINATION

The authors will publish findings from this review in a peer-reviewed scientific journal(s) and present the results at national and international conferences. This work will advance scientific certainty regarding natural history and prognostic factors of cognitive status in males and females with CNS trauma, informing clinicians, policymakers and future researchers on the topic.

PROSPERO REGISTRATION NUMBER

CRD42017055309.

Dynamic wheelchair seating positions impact cardiovascular function after spinal cord injury

BACKGROUND

Innovative wheelchairs allow individuals to change position easily for comfort and social situations. While these wheelchairs are beneficial in multiple ways, the effects of position changes on blood pressure might exacerbate hypotension and cerebral hypoperfusion, particularly in those with spinal cord injury (SCI) who can have injury to autonomic nerves that regulate cardiovascular control. Conversely, cardiovascular benefits may be obtained with lowered seating. Here we investigate the effect of moderate changes in wheelchair position on orthostatic cardiovascular and cerebrovascular reflex control.

METHODS

Nineteen individuals with SCI and ten neurologically-intact controls were tested in supine and seated positions (neutral, lowered, and elevated) in the Elevation™ wheelchair. Participants with SCI were stratified into two groups by the severity of injury to cardiovascular autonomic pathways. Beat-to-beat blood pressure, heart rate and middle cerebral artery blood flow velocity (MCAv) were recorded non-invasively.

RESULTS

Supine blood pressure and MCAv were reduced in individuals with lesions to autonomic pathways, and declined further with standard seating compared to those with preserved autonomic control. Movement to the elevated position triggered pronounced blood pressure and MCAv falls in those with autonomic lesions, with minimum values significantly reduced compared to the seated and lowered positions. The cumulative duration spent below supine blood pressure was greatest in this group. Lowered seating bolstered blood pressure in those with lesions to autonomic pathways.

CONCLUSIONS

Integrity of the autonomic nervous system is an important variable that affects cardiovascular responses to orthostatic stress and should be considered when individuals with SCI or autonomic dysfunction are selecting wheelchairs.

SPONSORSHIP

This work was supported in part by the Heart and Stroke Foundation of British Columbia and the Yukon (V.E.C).

Autonomic dysreflexia after spinal cord injury: Systemic pathophysiology and methods of management

Traumatic spinal cord injury (SCI) has widespread physiological effects beyond the disruption of sensory and motor function, notably the loss of normal autonomic and cardiovascular control. Injury at or above the sixth thoracic spinal cord segment segregates critical spinal sympathetic neurons from supraspinal modulation which can result in a syndrome known as autonomic dysreflexia (AD). AD is defined as episodic hypertension and concomitant baroreflex-mediated bradycardia initiated by unmodulated sympathetic reflexes in the decentralized cord. This condition is often triggered by noxious yet unperceived visceral or somatic stimuli below the injury level and if severe enough can require immediate medical attention. Herein, we review the pathophysiological mechanisms germane to the development of AD, including maladaptive plasticity of neural circuits mediating abnormal sympathetic reflexes and hypersensitization of peripheral vasculature that collectively contribute to abnormal hemodynamics after SCI. Further, we discuss the systemic effects of recurrent AD and pharmacological treatments used to manage such episodes. Contemporary research avenues are then presented to better understand the relative contributions of underlying mechanisms and to elucidate the effects of recurring AD on cardiovascular and immune functions for developing more targeted and effective treatments to attenuate the development of this insidious syndrome following high-level SCI.

Inter-day reliability of blood pressure and cerebral blood flow velocities in persons with spinal cord injury and intact controls

BACKGROUND

Due to interruption of cardiovascular autonomic control unstable blood pressure (BP) is common in individuals with spinal cord injury (SCI) above the sixth thoracic vertebral level. The impact of unstable BP on cerebral blood flow (CBF) is not well appreciated, but symptoms associated with altered cerebral perfusion are reported, which can negatively impact daily life activities.

METHODS

We measured seated BP and CBF in participants with SCI and able-bodied (AB) controls on three laboratory visits to determine the inter-day reliability (intraclass correlation coefficient: ICC). BP was assessed at the finger using photoplethysmography and at the brachial artery with manual sphygmomanometry. CBF velocities (CBFv) were assessed at the middle cerebral artery using transcranial Doppler (TCD) ultrasound.

RESULTS

Data were collected in 15 participants with chronic SCI (C3-T4) and 10 AB controls, the groups did not differ for age, height, weight or BMI; however, brachial BP (P < 0.001), finger BP (P < 0.01) and CBFv (P < 0.05) were significantly lower in the SCI group compared to the controls. The inter-day ICC for brachial BP ranged from 0.51 to 0.79, whereas the ICC for finger BP was not as high (0.17 to 0.47). The inter-day ICC for CBFv ranged from 0.45 to 0.96, indicating fair to substantial reliability.

CONCLUSIONS

These data indicate good inter-day reliability of brachial BP and TCD recording of CBFv; however, the assessment of finger BP appears to be somewhat less reliable. In addition, these data confirm reduced resting CBFv in association with hypotension in individuals with SCI compared to matched controls with low BP.

Cardiovascular Physiology and Responses to Sexual Activity in Individuals Living with Spinal Cord Injury

Background: Spinal cord injury (SCI) may profoundly impact autonomic function producing a variable degree of dysfunction in cardiovascular, bronchopulmonary, sweating, bladder, bowel, and sexual function. The cardiovascular system is crucially important for sexual function, as it is responsible for blood flow shifts to cavernous and musculoskeletal tissue during sexual activity. This system is prone to 3 main abnormalities after SCI including low resting blood pressure (LRBP), orthostatic hypotension (OH), and autonomic dysreflexia (AD), all of which have important effects on sexual function. Methods: We review the current etiological mechanisms and manifestations of cardiovascular dysfunction after SCI and discuss how this is documented to impact sexual function in individuals living with SCI. Conclusions: All individuals with SCI at or above the T6 neurologic level have an increased risk of AD during sexual stimulation, with increasing risk associated with higher levels of injury and greater completeness of injury. AD can be silent, and individuals living with SCI should be aware of blood pressure values at baseline and during sexual activity. Clinicians performing vibrostimulation fertility procedures need to be aware of the risk of AD and consider pretreatment if needed. Researchers studying the cardiovascular response to sexual stimulation should consider continuous monitoring of blood pressure, as intermittent monitoring may underestimate true blood pressure values.

Endoplasmic Reticulum Stress and Disrupted Neurogenesis in the Brain Are Associated with Cognitive Impairment and Depressive-Like Behavior after Spinal Cord Injury

Clinical and experimental studies show that spinal cord injury (SCI) can cause cognitive impairment and depression that can significantly impact outcomes. Thus, identifying mechanisms responsible for these less well-examined, important SCI consequences may provide targets for more effective therapeutic intervention. To determine whether cognitive and depressive-like changes correlate with injury severity, we exposed mice to sham, mild, moderate, or severe SCI using the Infinite Horizon Spinal Cord Impactor and evaluated performance on a variety of neurobehavioral tests that are less dependent on locomotion. Cognitive impairment in Y-maze, novel objective recognition, and step-down fear conditioning tasks were increased in moderate- and severe-injury mice that also displayed depressive-like behavior as quantified in the sucrose preference, tail suspension, and forced swim tests. Bromo-deoxyuridine incorporation with immunohistochemistry revealed that SCI led to a long-term reduction in the number of newly-generated immature neurons in the hippocampal dentate gyrus, accompanied by evidence of greater neuronal endoplasmic reticulum (ER) stress. Stereological analysis demonstrated that moderate/severe SCI reduced neuronal survival and increased the number of activated microglia chronically in the cerebral cortex and hippocampus. The potent microglial activator cysteine-cysteine chemokine ligand 21 (CCL21) was elevated in the brain sites after SCI in association with increased microglial activation. These findings indicate that SCI causes chronic neuroinflammation that contributes to neuronal loss, impaired hippocampal neurogenesis and increased neuronal ER stress in important brain regions associated with cognitive decline and physiological depression. Accumulation of CCL21 in brain may subserve a pathophysiological role in cognitive changes and depression after SCI.

Rigid and remodelled: cerebrovascular structure and function after experimental high-thoracic spinal cord transection

High-thoracic or cervical spinal cord injury (SCI) is associated with several critical clinical conditions related to impaired cerebrovascular health, including: 300-400% increased risk of stroke, cognitive decline and diminished cerebral blood flow regulation. The purpose of this study was to examine the influence of high-thoracic (T3 spinal segment) SCI on cerebrovascular structure and function, as well as molecular markers of profibrosis. Seven weeks after complete T3 spinal cord transection (T3-SCI, n = 15) or sham injury (Sham, n = 10), rats were sacrificed for either middle cerebral artery (MCA) structure and function assessments via ex vivo pressure myography, or immunohistochemical analyses. Myogenic tone was unchanged, but over a range of transmural pressures, inward remodelling occurred after T3-SCI with a 40% reduction in distensibility (both P < 0.05), and a 33% reduction in vasoconstrictive reactivity to 5-HT trending toward significance (P = 0.09). After T3-SCI, the MCA had more collagen I (42%), collagen III (24%), transforming growth factor β (47%) and angiotensin II receptor type 2 (132%), 27% less elastin as well as concurrent increased wall thickness and reduced lumen diameter (all P < 0.05). Sympathetic innervation (tyrosine hydroxylase-positive axon density) and endothelium-dependent dilatation (carbachol) of the MCA were not different between groups. This study demonstrates profibrosis and hypertrophic inward remodelling within the largest cerebral artery after high-thoracic SCI, leading to increased stiffness and possibly impaired reactivity. These deleterious adaptations would substantially undermine the capacity for regulation of cerebral blood flow and probably underlie several cerebrovascular clinical conditions in the SCI population.