Systemic and cerebral hemodynamics during cognitive testing

Cognitive, behavioral and psychiatric symptoms in patients with spinal cord injury: a scoping review

Spinal Cord Injury (SCI) is a condition where the spinal cord is damaged and experiences partial or complete loss of motor and/or sensory function, which is typically less than normal. After SCI, patients may exhibit more severe psychiatric symptoms and experience cognitive impairments, including reduced speed and attention processing capacity, as well as difficulties with executive function and episodic memory retention. Among the behavioral and psychiatric symptoms, depression, anxiety, substance use disorder, and posttraumatic stress disorder are the most common. This review aims to investigate the cognitive, behavioral, or psychiatric symptoms of the patient with SCI and their influence on the rehabilitation process. Studies were identified from an online search of PubMed, Web of Science, Cochrane Library, and Embase databases. Studies published between 2013-2023 were selected. This review has been registered on OSF (n) 3KB2U. We have found that patients with SCI are at high risk of cognitive impairment and experience a wide range of difficulties, including tasks based on processing speed and executive function. This clinical population may experience adjustment disorders with depression and anxiety, as well as other psychiatric symptoms such as fatigue, stress, and suicidal ideation. This review has demonstrated that SCI patients may experience psychiatric symptoms and cognitive impairments that affect their functioning. At the same time, these patients may be more prone to various adjustment and mood disorders. Moreover, these two aspects may interact with each other, causing a range of symptoms, increasing the risk of hospitalization, and delaying the rehabilitation process.

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.

Massive body-brain disconnection consequent to spinal cord injuries drives profound changes in higher-order cognitive and emotional functions: A PRISMA scoping review

Spinal cord injury (SCI) leads to a massive disconnection between the brain and the body parts below the lesion level representing a unique opportunity to explore how the body influences a person's mental life. We performed a systematic scoping review of 59 studies on higher-order cognitive and emotional changes after SCI. The results suggest that fluid abilities (e.g. attention, executive functions) and emotional regulation (e.g. emotional reactivity and discrimination) are impaired in people with SCI, with progressive deterioration over time. Although not systematically explored, the factors that are directly (e.g. the severity and level of the lesion) and indirectly associated (e.g. blood pressure, sleeping disorders, medication) with the damage may play a role in these deficits. The inconsistency which was found in the results may derive from the various methods used and the heterogeneity of samples (i.e. the lesion completeness, the time interval since lesion onset). Future studies which are specifically controlled for methods, clinical and socio-cultural dimensions are needed to better understand the role of the body in cognition.

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.

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.

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 Profiles Among Individuals With Spinal Cord Injuries: Predictors and Relations With Psychological Well-being

OBJECTIVES

To examine predictors of profiles of cognitive functioning among individuals receiving acute inpatient spinal cord injury (SCI) rehabilitation, as well as associations between their cognitive functioning and psychological well-being (life satisfaction and depression) 6 months after the baseline assessment.

DESIGN

Prospective observational study design, with 2 assessments approximately 6 months apart.

SETTING

A rehabilitation unit at a level 1 trauma hospital during acute SCI hospitalization and outpatient setting after discharge.

PARTICIPANTS

Individuals (N=89) with SCI.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Cognitive functioning (assessed by the Repeatable Battery for the Assessment of Neuropsychological Status), life satisfaction (measured by the Life Satisfaction Index A), and depressive symptoms (measured by the Patient Health Questionnaire-9).

RESULTS

Latent profile analysis identified 3 classes of individuals with similar patterns of cognitive functioning: class1 (average levels of cognitive performance across all assessed domains; n=48), class 2 (average cognitive performance, except in recall and memory; n=23), and class 3 (low cognitive functioning across multiple domains of cognition; n=18). Fewer years of education, history of smoking, history of substance use other than alcohol, and greater postconcussion symptoms were associated with higher odds of classification in class 3 (P<.05). Six months post baseline, individuals in class 3 reported significantly lower levels of life satisfaction than individuals in class 1 (χ²(1)=5.86; P=.045) and marginally higher depressive symptoms than individuals in class 2 (χ²(1)=5.48; P=.057)_. CONCLUSIONS: The impact of impaired cognition during acute rehabilitation may persist after discharge and influence the psychological well-being of individuals with SCI. Identifying individuals with cognitive dysfunction and attending to modifiable risk factors and may help ameliorate maladjustment after SCI.

Patterns of cognitive deficits in persons with spinal cord injury as compared with both age-matched and older individuals without spinal cord injury

Context/Objective: Cognitive deficits can impact as many as 60% of individuals with spinal cord injury (SCI). In an effort to identify the nature of cognitive deficits in SCI, we examined neuropsychological test performance in individuals with SCI, age matched healthy controls and older healthy controls.Design: Participants completed a motor-free neuropsychological test battery assessing attention, working memory, information processing speed, new learning /memory and executive control.Setting: Outpatient rehabilitation research facility.Participants: Participants included 60 individuals with chronic spinal cord injury [SCI; 32 with paraplegia (T2-T12) and 28 with tetraplegia (C3-T1)], 30 age-matched healthy controls (AMHC; 30-40 years old) and 20 older healthy controls (OHC; 50-60 years old).Outcome Measures: Wechsler Intelligence Scale - 3^rd edition (WAIS-III) Digit Span and Letter-Number Sequencing; Symbol Digit Modalities Test (SDMT) - oral version; California Verbal Learning Test-II; Paced Auditory Serial Addition Test (PASAT); Wechsler Abbreviated Scale of Intelligence (WASI); Delis-Kaplan Executive Function System; Verbal Fluency subtest.Results: Significant differences were noted between the SCI and AMHC groups on measures of information processing speed, new learning and memory, and verbal fluency. No significant differences were noted between the groups on tests of attention or working memory.Conclusion: The current study documented differences in specific realms of cognitive functioning between a chronic SCI sample and AMHC. Implications for cognitive rehabilitation and overall quality of life are discussed. Additional research is needed utilizing a more comprehensive battery of motor-free neuropsychological tests that avoid the confound of upper limb motor limitations on cognitive performance.

Cerebral blood flow modulations during proactive control in chronic hypotension

In addition to complaints including fatigue, mood disturbance, dizziness or cold limbs, chronic low blood pressure (hypotension) is associated with reduced cognitive performance. Deficiencies in cerebral blood flow regulation may contribute to this impairment. This study investigated cerebral blood flow modulations during proactive control in hypotension. Proactive control refers to cognitive processes during anticipation of a behaviourally relevant event that allow optimization of readiness to react. Using functional transcranial Doppler sonography, bilateral blood flow velocities in the middle cerebral arteries were recorded in 40 hypotensive and 40 normotensive participants during a precued Stroop task. Hypotensive participants exhibited smaller bilateral blood flow increases during response preparation and longer response time. The group differences in blood flow and response time did not vary by executive function load, i.e. congruent vs. incongruent trials. Over the total sample, the flow increase correlated negatively with response time in trials with a higher executive function load. The findings indicate reduced cerebral blood flow adjustment during both the basic and more complex requirements of proactive control in hypotension. They also suggest a general deficit in attentional function and processing speed due to low blood pressure and cerebral hemodynamic dysregulations rather than particular impairments in executive functions.

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.

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).

Alterations in autonomic cerebrovascular control after spinal cord injury

Among chronic cardiovascular and metabolic sequelae of spinal cord injury (SCI) is an up-to four-fold increase in the risk of ischemic and hemorrhagic stroke, suggesting that individuals with SCI cannot maintain stable cerebral perfusion. In able-bodied individuals, the cerebral vasculature is able to regulate cerebral perfusion in response to swings in arterial pressure (cerebral autoregulation), blood gases (cerebral vasoreactivity), and neural metabolic demand (neurovascular coupling). This ability depends, at least partly, on intact autonomic function, but high thoracic and cervical spinal cord injuries result in disruption of sympathetic and parasympathetic cerebrovascular control. In addition, alterations in autonomic and/or vascular function secondary to paralysis and physical inactivity can impact cerebrovascular function independent of the disruption of autonomic control due to injury. Thus, it is conceivable that SCI results in cerebrovascular dysfunction that may underlie an elevated risk of stroke in this population, and that rehabilitation strategies targeting this dysfunction may alleviate the long-term risk of adverse cerebrovascular events. However, despite this potential direct link between SCI and the risk of stroke, studies exploring this relationship are surprisingly scarce, and the few available studies provide equivocal results. The focus of this review is to provide an integrated overview of the available data on alterations in cerebral vascular function after SCI in humans, and to provide suggestions for future research.

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.

Effects of midodrine and L-NAME on systemic and cerebral hemodynamics during cognitive activation in spinal cord injury and intact controls

We previously showed that increases in mean arterial pressure (MAP) following administration of midodrine hydrochloride (MH) and nitro‐L‐arginine methyl ester (L‐NAME) resulted in increased mean cerebral blood flow velocity (MFV) during head‐up tilt in hypotensive individuals with spinal cord injury (SCI) and question if this same association was evident during cognitive activation. Herein, we report MAP and MFV during two serial subtraction tasks (SSt) given before (predrug) and after (postdrug) administration of MH; (10 mg), L‐NAME (1 mg/kg) or no drug (ND) in 15 subjects with SCI compared to nine able‐bodied (AB) controls. Three‐way factorial analysis of variance (ANOVA) models were used to determine significant main and interaction effects for group (SCI, AB), visit (MH, L‐NAME, ND), and time (predrug, postdrug) for MAP and MFV during the two SSt. The three‐way interaction was significant for MAP (F = 4.262; P = 0.020); both MH (30 ± 26 mmHg; P < 0.05) and L‐NAME (27 ± 22 mmHg; P < 0.01) significantly increased MAP in the SCI group, but not in the AB group. There was a significant visit by time interaction for MFV suggesting an increase from predrug to postdrug following L‐NAME (6 ± 8 cm/sec; P < 0.05) and MH (4 ± 7 cm/sec; P < 0.05), regardless of study group, with little change following ND (3 ± 3 cm/sec). The relationship between change in MAP and MFV was significant in the SCI group following administration of MH (r² = 0.38; P < 0.05) and L‐NAME (r² = 0.32; P < 0.05). These antihypotensive agents, at the doses tested, raised MAP, which was associated with an increase MFV during cognitive activation in hypotensive subjects with SCI.

Targeting inflammation to influence cognitive function following spinal cord injury: a randomized clinical trial

STUDY DESIGN

This study was a randomized, parallel-group, controlled clinical trial.

OBJECTIVES

The purpose of this study was to examine the efficacy of targeting inflammation as a means of improving cognitive function in individuals with spinal cord injury.

SETTING

Participants were recruited from the Niagara region of Ontario Canada and all testing occurred on-site at Brock University.

METHODS

Indices of memory and verbal learning were assessed by means of the California Verbal Learning Test (CVLT). Inflammation and concentrations of neuroactive compounds related to the kynurenine pathway were assessed via a number of pro- and anti-inflammatory cytokines, as well as tryptophan, kynurenine and several large neutral amino acids. All assessments were performed at baseline as well as at 1 month and 3 months during a 3-month intervention by means of an anti-inflammatory diet.

RESULTS

Despite a reduction in inflammation, all measures of the CVLT, including list A, trial 1 (P=0.48), learning slope (P=0.46), long delay free recall (P=0.83), intrusions (P=0.61) and repetitions (P=0.07), showed no significant group × time interaction.

CONCLUSION

It may be possible that the reduction in inflammation achieved in the current study was insufficient to induce substantial changes in indices of verbal learning and memory. Alternatively, as these participants likely underwent years of previous chronic inflammation, the underlying hippocampal damage may have negated potential improvements induced by acute reductions in inflammation.

A cerebral blood flow evaluation during cognitive tasks following a cervical spinal cord injury: a case study using transcranial Doppler recordings

A spinal cord injury (SCI) is one of the most common neurological disorders. In this paper, we examined the consequences of upper SCI in a male participant on the cerebral blood flow velocity. In particular, transcranial Doppler was used to study these effects through middle cerebral arteries (MCA) during resting-state periods and during cognitive challenges (non-verbal word-generation tasks and geometric-rotation tasks). Signal characteristics were analyzed from raw signals and envelope signals (maximum velocity) in the time domain, the frequency domain and the time-frequency domain. The frequency features highlighted an increase of the peak frequency in L-MCA and R-MCA raw signals, which revealed stronger cerebral blood flow during geometric/verbal processes respectively. This underlined a slight dominance of the right hemisphere during word-generation periods and a slight dominance of the left hemisphere during geometric processes. This finding was confirmed by cross-correlation in the time domain and by the entropy rate in information-theoretic domain. A comparison of our results to other neurological disorders (Alzheimer's disease, Parkinson's disease, autism, epilepsy, traumatic brain injury) showed that the SCI had similar effects such as general decreased cerebral blood flow and similar regular hemispheric dominance in a few cases.

Prevalence of abnormal systemic hemodynamics in veterans with and without spinal cord injury

OBJECTIVE

Increased prevalence of heart rate and blood pressure abnormalities are evident in persons with spinal cord injury (SCI), but age, comorbid medical conditions, and prescription medication use may contribute. To determine differences in the prevalence of cardiac acceleration (heart rate ≥80 beats per minute), hypotension (blood pressure ≤110/70mmHg), orthostatic hypotension (OH) (-20/-10mmHg with upright positioning), and hypertension (HTN) (blood pressure ≥140/90mmHg) in veterans with and without SCI.

DESIGN

Observational trial.

SETTING

Medical center.

PARTICIPANTS

Subjects included veterans with SCI (n=62; cervical: tetraplegia, C3-8; high thoracic, T1-5; low thoracic, T7-L2) and veterans without SCI (n=160).

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

We assessed medical history, prescription medication use, and heart rate and blood pressure during a routine clinical visit. Prevalence rates of cardiac acceleration, hypotension, OH, and HTN were calculated using binary logistic regression analysis with 95% confidence intervals. The influence of SCI status, age, smoking status, cardiovascular diagnoses, and use of prescribed antihypertensive medications on the prevalence of abnormal heart rate and blood pressure recordings was determined.

RESULTS

The diagnosis of HTN was reduced in the high thoracic and tetraplegia groups compared with the non-SCI and low thoracic groups. Use of antihypertensive medications was increased in the low thoracic group compared with the other 3 groups and was increased in the non-SCI group compared with the tetraplegia group. The prevalence of cardiac acceleration was reduced, and the prevalence of systolic hypotension was increased in the tetraplegia group. The prevalence of diastolic hypotension was increased in all SCI groups compared with the non-SCI group. For all analyses, increased prevalence of abnormal heart rate and blood pressure recordings was not further explained by the covariates, with the exception of age, cardiovascular diagnoses, and antihypertensive medications in the cardiac acceleration model; however, SCI status remained significant and was the dominant predictor variable.

CONCLUSIONS

Our data suggest that SCI status contributes to the prevalence of cardiac acceleration and systolic and diastolic hypotension regardless of cardiovascular medical conditions or prescription antihypertensive medication use.

Orthostatic responses to anticholinesterase inhibition in spinal cord injury

INTRODUCTION

Acetylcholine (Ach) is the pre-synaptic neurotransmitter of the sympathetic nervous system. Increased pre-synaptic Ach may augment post-synaptic release of norepinephrine, thereby increasing systemic blood pressure (BP).

OBJECTIVES

The primary objective of this investigation was to determine the hemodynamic effect of pyridostigmine bromide (PYRIDO: 60 mg), an Ach inhibitor (AchI), compared to no-drug (NO-D) during head-up tilt (HUT) in individuals with spinal cord injury (SCI). Secondarily, we aimed to determine the effects of PYRIDO compared to NO-D on symptoms of orthostatic intolerance (OI) and adverse event reporting (AE).

METHODS

Ten individuals with SCI (C4-C7) were studied on two occasions: visit (1) NO-D and visit (2) PYRIDO. On each visit subjects underwent a progressive HUT maneuver to 15°, 25°, 35° for 5 min at each angle and 45 min at 45°. Supine and orthostatic heart rate (HR), systolic and diastolic BP (SBP and DBP), as well as monitored and symptoms of OI and AE were monitored and recorded.

RESULTS

Supine hemodynamics did not differ between the trials. The significant fall in SBP during the NO-D trial was diminished with PYRIDO, and five subjects had an increased DBP during HUT with PYRIDO compared to the NO-D trial. Individuals that responded to PYRIDO with an increase in orthostatic BP had significantly lower resting HR than non-responders (p < 0.01), which suggests increased levels of pre-synaptic Ach. Subjective symptoms of OI and AE reporting did not differ between the two trials.

CONCLUSIONS

These preliminary data suggest that PYRIDO is safe and may be effective at ameliorating the orthostatic fall in BP in select individuals with SCI.

Regional neurovascular coupling and cognitive performance in those with low blood pressure secondary to high-level spinal cord injury: improved by alpha-1 agonist midodrine hydrochloride

Individuals with high-level spinal cord injury (SCI) experience low blood pressure (BP) and cognitive impairments. Such dysfunction may be mediated in part by impaired neurovascular coupling (NVC) (i.e., cerebral blood flow responses to neurologic demand). Ten individuals with SCI >T6 spinal segment, and 10 age- and sex-matched controls were assessed for beat-by-beat BP, as well as middle and posterior cerebral artery blood flow velocity (MCAv, PCAv) in response to a NVC test. Tests were repeated in SCI after 10 mg midodrine (alpha1-agonist). Verbal fluency was measured before and after midodrine in SCI, and in the control group as an index of cognitive function. At rest, mean BP was lower in SCI (70 ± 10 versus 92 ± 14 mm Hg; P<0.05); however, PCAv conductance was higher (0.56 ± 0.13 versus 0.39 ± 0.15 cm/second/mm Hg; P<0.05). Controls exhibited a 20% increase in PCAv during cognition; however, the response in SCI was completely absent (P<0.01). When BP was increased with midodrine, NVC was improved 70% in SCI, which was reflected by a 13% improved cognitive function (P<0.05). Improvements in BP were related to improved cognitive function in those with SCI (r(2)=0.52; P<0.05). Impaired NVC, secondary to low BP, may partially mediate reduced cognitive function in individuals with high-level SCI.

Regulation of cerebral blood flow after spinal cord injury

Significant cardiovascular and autonomic dysfunction occurs after era spinal cord injury (SCI). Two major conditions arising from autonomic dysfunction are orthostatic hypotension and autonomic dysreflexia (i.e., severe acute hypertension). Effective regulation of cerebral blood flow (CBF) is essential to offset these drastic changes in cerebral perfusion pressure. In the context of orthostatic hypotension and autonomic dysreflexia, the purpose of this review is to critically examine the mechanisms underlying effective CBF after an SCI and propose future avenues for research. Although only 16 studies have examined CBF control in those with high-level SCI (above the sixth thoracic spinal segment), it appears that CBF regulation is markedly altered in this population. Cerebrovascular function comprises three major mechanisms: (1) cerebral autoregulation, (i.e., ΔCBF/Δ blood pressure); (2) cerebrovascular reactivity to changes in PaCO2 (i.e. ΔCBF/arterial gas concentration); and (3) neurovascular coupling (i.e., ΔCBF/Δ metabolic demand). While static cerebral autoregulation appears to be well maintained in high-level SCI, dynamic cerebral autoregulation, cerebrovascular reactivity, and neurovascular coupling appear to be markedly altered. Several adverse complications after high-level SCI may mediate the changes in CBF regulation including: systemic endothelial dysfunction, sleep apnea, dyslipidemia, decentralization of sympathetic control, and dominant parasympathetic activity. Future studies are needed to describe whether altered CBF responses after SCI aid or impede orthostatic tolerance. Further, simultaneous evaluation of extracranial and intracranial CBF, combined with modern structural and functional imaging, would allow for a more comprehensive evaluation of CBF regulatory processes. We are only beginning to understand the functional effects of dysfunctional CBF regulation on brain function on persons with SCI, which are likely to include increased risk of transient ischemic attacks, stroke, and cognitive dysfunction.

L-DOPS and the treatment of neurogenic orthostatic hypotension

L-threo-dihydroxyphenylserine (L-DOPS) is an oral prodrug that is converted to the sympathetic neurotransmitter noradrenaline through a single-step decarboxylation by the endogenous enzyme 3,4-dihydrophenylalanine decarboxylase. DOPS can provide an exogenous source of noradrenaline to adrenergic neurons that are involved in the maintenance of blood pressure. Impaired secretion of noradrenaline at the synaptic junction can result in neurogenic orthostatic hypotension and cause faints and falls. The safety and efficacy of DOPS has been evaluated in patients with neurogenic orthostatic hypotension caused by a variety of neurological conditions that can result in autonomic failure, such as Parkinson’s disease, multiple system atrophy, pure autonomic failure and dopamine-β-hydroxylase deficiency. In this review, we include Phase II and III clinical trials undertaken that have examined the safety, efficacy and tolerability of DOPS in the treatment of neurogenic orthostatic hypotension. Drug mechanisms and pharmacology of the drug are also discussed.

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

Spinal cord injury (SCI) results in motor and sensory impairments that can be identified with the American Spinal Injury Association (ASIA) Impairment Scale (AIS). Although, SCI may disrupt autonomic neural transmission, less is understood regarding the clinical impact of decentralized autonomic control. Cardiovascular regulation may be altered following SCI and the degree of impairment may or may not relate to the level of AIS injury classification. In general, persons with lesions above T1 present with bradycardia, hypotension, and orthostatic hypotension; functional changes which may interfere with rehabilitation efforts. Although many individuals with SCI above T1 remain overtly asymptomatic to hypotension, we have documented deficits in memory and attention processing speed in hypotensive individuals with SCI compared to a normotensive SCI cohort. Reduced resting cerebral blood flow (CBF) and diminished CBF responses to cognitive testing relate to test performance in hypotensive non-SCI, and preliminary evidence suggests a similar association in individuals with SCI. Persons with paraplegia below T7 generally present with a normal cardiovascular profile; however, our group and others have documented persistently elevated heart rate and increased arterial stiffness. In the non-SCI literature there is evidence supporting a link between increased arterial stiffness and cognitive deficits. Preliminary evidence suggests increased incidence of cognitive impairment in individuals with paraplegia, which we believe may relate to adverse cardiovascular changes. This report reviews relevant literature and discusses findings related to the possible association between decentralized cardiovascular autonomic control and cognitive dysfunction in persons with SCI.

31st g. Heiner sell lectureship: secondary medical consequences of spinal cord injury

Persons with spinal cord injury (SCI) have secondary medical consequences of paralysis and/or the consequences of extreme inactivity. The metabolic changes that result from reduced activity include insulin resistance with carbohydrate disorders and dyslipidemia. A higher prevalence of coronary artery calcification was found in persons with SCI than that in matched able-bodied controls. A depression in anabolic hormones, circulating testosterone and growth hormone, has been described. Adverse soft tissue body composition changes of increased adiposity and reduced skeletal muscle are appreciated. Immobilization is the cause for sublesional disuse osteoporosis with an associated increased risk of fragility fracture. Bowel dysmotility affects all segments of the gastrointestinal tract, with an interest in better defining and addressing gastroesophageal reflux disease and difficulty with evacuation. Developing and testing more effective approaches to cleanse the bowel for elective colonoscopy are being evaluated. The extent of respiratory dysfunction depends on the level and completeness of SCI. Individuals with higher spinal lesions have both restrictive and obstructive airway disease. Pharmacological approaches and expiratory muscle training are being studied as interventions to improve pulmonary function and cough strength with the objective of reducing pulmonary complications. Persons with spinal lesions above the 6th thoracic level lack both cardiac and peripheral vascular mechanisms to maintain blood pressure, and they are frequently hypotensive, with even worse hypotension with upright posture. Persistent and/or orthostatic hypotension may predispose those with SCI to cognitive impairments. The safety and efficacy of anti-hypotensive agents to normalize blood pressure in persons with higher level cord lesions is being investigated.