Cardiovascular consequences of loss of supraspinal control of the sympathetic nervous system after spinal cord injury

Serotonin syndrome caused by minimum doses of SSRIS in a patient with spinal cord injury

There have been only a few reports of serotonin syndrome developing after mono-therapy with a selective serotonin reuptake inhibitor (SSRI). We report a case of serotonin syndrome caused by long-term therapy with fluvoxamine prior to treatment with paroxetine. An 18-year-old man with spinal cord injury (SCI) at thoracic level 2-3 presented with onset of serotonin syndrome after taking fluvoxamine (50 mg per day) for 8 weeks prior to treatment with paroxetine (10 mg per day) for 6 days. He had confusion, agitation, severe headache, tachycardia (124 beats/minute), hypertension (165/118 mmHg), high fever (39.1 degrees C), and myoclonus. All of the symptoms disappeared within 24 hours after discontinuation of administration of paroxetine. This is an interesting case of serotonin syndrome that developed after minimum doses of single therapy with an SSRI in a patient with SCI.

Cardiovascular and temperature changes in spinal cord injured rats at rest and during autonomic dysreflexia

In patients with high spinal cord injuries autonomic dysfunction can be dangerous, leading to medical complications such as postural hypotension, autonomic dysreflexia and temperature disturbance. While animal models have been developed to study autonomic dysreflexia, associated temperature changes have not been documented. Our aim here was to use radiotelemetry and infrared thermography in rodents to record the development of cardiovascular and skin temperature changes following complete T4 transection. In adult male Wistar rats (n=5), responses were assessed prior to spinal cord injury (intact) and for 6 weeks following injury. Statistical analysis by a repeated-measure ANOVA revealed that following spinal cord injury (SCI), rats exhibited decreased mean arterial pressure (MAP, average decrease of 26 mmHg; P<0.035) and elevated heart rate (HR, average increase of 65 bpm, P<0.035) at rest. The basal core body temperature following SCI was also significantly lower than intact levels (-0.9 degrees C; P<0.0035). Associated with this decreased basal core temperature following SCI was an increased skin temperature of the mid-tail and hindpaw (+5.6 and +4.0 degrees C, respectively; P<0.0003) consistent with decreased cutaneous vasoconstrictor tone. Autonomic dysreflexia, in response to a 1 min colorectal distension (25 mmHg), was fully developed by 4 weeks after spinal cord transection, producing increases in MAP greater than 25 mmHg (P<0.0003). In contrast to the tachycardia seen in intact animals in response to colorectal distension, SCI animals exhibited bradycardia (P<0.0023). During episodes of autonomic dysreflexia mid-tail surface temperature decreased (approximately -1.7 degrees C, P<0.012), consistent with cutaneous vasoconstriction. This is the first study to compare cardiovascular dysfunction with temperature changes following spinal cord transection in rats.

Cardiovascular responses and postexercise hypotension after arm cycling exercise in subjects with spinal cord injury

OBJECTIVE

To examine postexercise hypotension and contributing factors in subjects with spinal cord injury (SCI).

DESIGN

Prospective clinical research study.

SETTING

Rehabilitation center.

PARTICIPANTS

Subjects with chronic cervical-level (n=19) and thoracic-level (n=8) SCI.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Subjects underwent graded arm-cycling with electrocardiogram and oxygen uptake monitoring to exhaustion. Heart rates and blood pressures were measured before and after exercising. Injury to motor and sensory pathways was determined by American Spinal Injury Association grade, and to autonomic pathways by sympathetic skin responses (SSRs) (n=16).

RESULTS

Resting blood pressures and heart rates were lower in cervical than thoracic SCI (mean arterial pressure [MAP]: cervical, 76.6+/-2 mmHg; thoracic, 93.5+/-3 mmHg; P<.001). Following exercise, heart rate responses were greater in thoracic than cervical SCI; MAP increased in thoracic SCI (8.4+/-5 mmHg) and markedly decreased in cervical SCI (-9.3+/-2 mmHg) (P<.001). No subject had significant electrocardiographic abnormalities at rest or during exercise. There were correlations between SSR and heart rate and blood pressure responses to exercise; the correlation between the SSR and blood pressure response was due to an interaction between the heart rate and blood pressure responses.

CONCLUSIONS

Abnormal cardiovascular responses to exercise and transient postexercise hypotension were common in cervical, but not thoracic SCI. This may be partly related to loss of descending sympathetic nervous control of the heart and vasculature following high SCI.

Effect of harness application and postural changes on cardiovascular parameters of individuals with spinal cord injury

STUDY DESIGN

Prospective assessment of cardiovascular parameters in individuals with spinal cord injury (SCI) in response to harness application and postural changes including orthostatic stress.

OBJECTIVE

To evaluate arterial blood pressure and heart rate (HR) with and without harness application during sitting, supine, and standing positions in able-bodied and SCI individuals.

METHODS

Measurements were obtained in all SCI research participants (n=11) before a locomotor training intervention and compared to data with able-bodied individuals (n=9). During standing, all research participants wore a harness and were suspended by an overhead, pneumatic body weight support system.

RESULTS

Resting arterial blood pressure and HR in individuals with cervical SCI were significantly lower during sitting than in thoracic SCI and able-bodied individuals (P<0.05). Orthostatic stress significantly decreased arterial blood pressure only in individuals with cervical SCI (P<0.05). Harness application had no effect on cardiovascular parameters in able-bodied individuals, whereas diastolic blood pressure was significantly increased in those with SCI. Orthostatic changes in cervical SCI when sitting were ameliorated by harness application. However, while standing with harness, individuals with cervical SCI still developed orthostatic hypotension.

CONCLUSIONS

Level of injury to the spinal cord influences baseline cardiovascular parameters. Application of harness in individuals with SCI could alter baseline cardiovascular parameters and the response to orthostatic stress. This should be carefully considered when assessing effects of therapeutic interventions using body weight support in individuals with SCI.

Recurrent Asystole Resulting from High Cervical Spinal Cord Injuries

Cervical spinal cord injury is a highly morbid condition frequently associated with cardiovascular instability. This instability may include bradyarrhythmias, as well as hypotension, and usually resolves in a relatively short time. However, over a 3-year period (January 2003–December, 2005), 5 of 30 patients with complete cervical spinal cord injuries seen at our Level I trauma center required placement of permanent cardiac pacemakers for recurrent bradycardia/asystolic events. Strong consideration for pacemaker placement should be given for those spinal cord-injured patients with symptomatic bradyarrhythmic events still occurring 2 weeks after injury.

Re-growth of catecholaminergic fibers and protection of cholinergic spinal cord neurons in spinal repaired rats

The extent of re-growth of catecholaminergic fibers, the survival of cholinergic neurons and the degree of autonomic dysreflexia were assessed in complete spinal cord-transected adult rats that received a repair treatment of peripheral nerve grafts and acidic fibroblast growth factor (aFGF). The rats were randomly divided into three groups: (1) sham control group (laminectomy only); (2) spinal cord transection at T8 (transected group); and (3) spinal cord transection at T8, followed by aFGF treatment and peripheral nerve graft (repaired group). The spinal cords and brains of all rats were collected at 6 months post-surgery. Immunohistochemistry for tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH), and fluoro-gold (FG) retrograde tracing were used to evaluate axon growth across the damage site, and immunocytochemistry for choline acetyl transferase (ChAT) was used to evaluate cholinergic neuronal cell survival following the injury and treatment. When comparing with the transected group, the repaired group showed: (1) lower elevation of mean arterial pressure during colorectal distension; (2) retrogradely labeled neurons in the hypothalamus, zona incerta, subcoeruleus nuclei and rostral ventrolateral medulla following application of FG below the repair site; (3) the presence of TH- and DBH-labeled axons below the lesion site; (4) higher numbers of ChAT-positive neurons in ventral horn and intermediolateral column near the lesion site. We conclude that peripheral nerve graft and aFGF treatments facilitate the re-growth of catecholaminergic fibers, also protect sympathetic preganglionic neurons and spinal motor neurons, and reduce autonomic dysfunction in a T-8 spinal cord-transected rat model.

Anesthetic Requirements and Stress Hormone Responses in Spinal Cord-Injured Patients Undergoing Surgery Below the Level of Injury

Neuraxial anesthesia decreases the minimum alveolar concentration. We determined the effects of spinal cord injury (SCI) on sevoflurane requirements and stress hormone response. Twenty-two chronic SCI patients undergoing surgery below the level of the injury were enrolled in the study, and 15 patients without cord injury served as control patients. Bispectral index score was maintained at 40-50. Measurements included end-tidal sevoflurane concentrations, systolic arterial blood pressure, heart rate, and plasma catecholamine and cortisol concentrations. During surgery, systolic arterial blood pressure, heart rate, and Bispectral index were comparable between SCI and control groups. However, end-tidal sevoflurane concentration was significantly smaller in the SCI (0.81%-1.06%) versus control (1.28%-1.31%) patients. In the control group, plasma norepinephrine and cortisol concentrations were significantly increased during and 1 h after surgery compared with awake baseline values. In the SCI group, the sympathoadrenal and cortisol responses were virtually abolished. We conclude that SCI reduces the anesthetic requirement by 20%-39% during surgery below the level of injury, in association with blunted sympathoadrenal and cortisol responses.

Adaptations of peripheral vasoconstrictor pathways after spinal cord injury

The consequences of spinal cord injury on the function of sympathetic pathways in the periphery have generally been ignored. We discuss two types of plasticity that follow disruption of sympathetic pathways in rats . The first relates to the partial denervation of sympathetic ganglia that would follow the loss of some preganglionic neurones. Sprouting of residual connections rapidly reinnervates many postganglionic neurones, restoring functional transmission within a few weeks, but other neurones may be permanently decentralized. Some of the new functional connections may generate inappropriate pathways leading to abnormal reflexes . The second type of plasticity concerns the markedly enhanced and prolonged contractile responses to nerve activity in arterial vessels to which ongoing sympathetic activity has been reduced or silenced following spinal cord transection or ganglion decentralization. In a cutaneous artery (the rat tail artery), the mechanisms underlying this arterial hyperreactivity differ from those in the splanchnic arteries (the rat mesenteric artery). In the former, hyperreactivity is mainly postjunctional but independent of changes in alpha1-adrenoceptor sensitivity, whereas the increased responsiveness in the latter vessels can be attributed to a greater responsiveness to alpha1-adrenoceptor activation. There are enough data from humans to suggest that both of these novel findings in experimental animals are likely to apply after spinal cord injury and contribute to autonomic dysreflexia .

Experimental strategies to promote spinal cord regeneration--an integrative perspective

Detailed pathophysiological findings of secondary damage phenomena after spinal cord injury (SCI) as well as the identification of inhibitory and neurotrophic proteins have yielded a plethora of experimental therapeutic approaches. Main targets are (i) to minimize secondary damage progression (neuroprotection), (ii) to foster axon conduction (neurorestoration) and (iii) to supply a permissive environment to promote axonal sprouting (neuroregenerative therapies). Pre-clinical studies have raised hope in functional recovery through the antagonism of growth inhibitors, application of growth factors, cell transplantation, and vaccination strategies. To date, even though based on successful pre-clinical animal studies, results of clinical trials are characterized by dampened effects attributable to difficulties in the study design (patient heterogeneity) and species differences. A combination of complementary therapeutic strategies might be considered pre-requisite for future synergistic approaches. Here, we line out pre-clinical interventions resulting in improved functional neurological outcome after spinal cord injury and track them on their intended way to bedside.

Problems of sexual function after spinal cord injury

Sex is a legitimate and fundamental need in humans. Substantial changes to both the autonomic and somatic nervous system occur after spinal cord injury, and result in altered sexual function and fertility potential. This chapter provides a clinical overview of the main sexual and reproductive concerns and priorities men and women face after spinal cord injury. Besides genital functioning, other autonomic functions affect sexuality, such as bladder and bowel function, cardiovascular control and temperature regulation. These interlinked autonomic functions are presented in their impact on sexuality. The mind-body interaction and spinal feedback loops are discussed. It is proposed that human sexuality after spinal cord injury can be a model for investigating integrated autonomic function. Recent research on the measurement of cardiovascular parameters during vibrostimulation and ejaculation demonstrates the discordance between objective and subjective signs of autonomic dysreflexia. It is hoped that health care professionals and researchers will become motivated to attend to the unmet sexual health care needs of this population.

Improvement of Metabolic and Cardiorespiratory Responses Through Treadmill Gait Training With Neuromuscular Electrical Stimulation in Quadriplegic Subjects

This work assessed the influence of treadmill gait training with neuromuscular electrical stimulation (NMES) on the metabolic and cardiorespiratory responses in quadriplegic subjects. The gait group (GG) (n=11) performed 6 months of treadmill training with 30-50% body weight support and with the help of physiotherapists, twice a week, allotting 20 min for each session. The control group (CG) (n=10), during the 6 months of training, did not perform any activity using NMES, performing instead conventional physiotherapy. Metabolic and cardiorespiratory responses (O(2) uptake [VO(2)], CO(2) production [VCO(2)], pulmonary ventilation (V(E)), heart rate [HR], and blood pressure [BP]) were measured on inclusion and after 6 months. For the GG, differences were found in all parameters after training (P<0.05), except for HR and diastolic BP. During gait, VO(2) (L/min) increased by 36%, VCO(2) (L/min) increased by 42.97%, V(E) (L/min) increased by 30.48%, and systolic BP (mm Hg) increased by 4.8%. For the CG, only VO(2) and VCO(2) (L/min) significantly increased at rest (30.82 and 16.39%, respectively) and during knee-extension exercise (26.29 and 17.37%, respectively). Treadmill gait with NMES was, therefore, more efficient toward increasing the aerobic capacity due to yielding higher metabolic and cardiovascular stresses.

The clinical problems in cardiovascular control following spinal cord injury: an overview

On a daily basis, individuals with cervical and upper thoracic spinal cord injury face the challenge of managing their unstable blood pressure, which frequently results in persistent hypotension and/or episodes of uncontrolled hypertension. This chapter will focus on the clinical issues related to abnormal cardiovascular control in individuals with spinal cord injury, which include neurogenic shock, autonomic dysreflexia and orthostatic hypotension. Blood pressure control depends upon tonic activation of sympathetic preganglionic neurons by descending input from the supraspinal structures (Calaresu and Yardley, 1988). Following spinal cord injury, these pathways are disrupted, and thus spinal circuits are solely responsible for the generation of sympathetic activity (Osborn et al., 1989; Maiorov et al., 1997). This results in a variety of cardiovascular abnormalities that have been well documented in human studies, as well as in animal models (Osborn et al., 1990; Mathias and Frankel, 1992a, b; Krassioukov and Weaver, 1995; Maiorov et al., 1997, 1998; Teasell et al., 2000). However, the recognition and management of these cardiovascular dysfunctions following spinal cord injury represent challenging clinical issues. Moreover, cardiovascular disorders in the acute and chronic stages of spinal cord injury are among the most common causes of death in individuals with spinal cord injury (DeVivo et al., 1999).

Genetic approaches to autonomic dysreflexia

Autonomic dysreflexia is a potentially life-threatening condition in which episodic hypertension occurs after injuries above the mid-thoracic segments of the spinal cord. Despite the seriousness of this condition, little is known of the molecular mechanisms that lead to its development. The completed sequencing of the mouse genome, its dense genetic map, and the large repository of engineered and spontaneous mouse mutants, make the mouse an ideal model organism in which to study the molecular mechanisms underlying autonomic dysreflexia. We subjected two wild-type strains of mice, 129Sv and C57BL/6, and one spontaneous mouse mutant, Wallerian degeneration slow (Wld s), to spinal cord transection and clip-compression injury. We found that the incidence of autonomic dysreflexia is greatly reduced, compared to spinal cord-transected wild-type mice, in Wld s mice after both injury paradigms and in 129Sv and C57BL/6 that have undergone the clip-compression injury. We also found that the amplitude of the dysreflexic response was greater in cord-compressed 129Sv than in C57BL/6 mice. These results implicate axonal degeneration as an important source of signals that trigger the development of autonomic dysreflexia and are discussed in the context of mouse genetics, interstrain differences and possible molecular mechanisms underlying autonomic dysreflexia after spinal cord injury.

Cardiovascular responses to vibrostimulation for sperm retrieval in men with spinal cord injury

BACKGROUND/OBJECTIVE

Cardiovascular abnormalities and arrhythmias are common in individuals with spinal cord injury (SCI) who are undergoing vibrostimulation for sperm retrieval. The study aimed to examine cardiovascular control in men with SCI undergoing this procedure.

METHODS

Individuals with chronic cervical (n=8; age: 33.1 +/- 1.9 years) and upper thoracic SCI (n=5; age: 35.2 +/- 2.9 years) volunteered for vibrostimulation, with continuous blood pressure (Finometer) and electrocardiographic monitoring. Patients were characterized further by sympathetic skin responses (SSR) to assess descending autonomic spinal pathways and American Spinal Injury Association (ASIA) scores to assess motor and sensory pathways.

RESULTS

All but one subject with cervical SCI were ASIA A or B and were negative for SSR in the hands and feet. All subjects with upper thoracic SCI were ASIA A or B and were positive for SSR in the hands. Systolic blood pressure was lower in men with cervical injury at rest. Vibrostimulation induced an increase in systolic blood pressure >20 mmHg in all patients with cervical SCI (range = 125/65 - 280/152; median = 167/143 mmHg) and in 2 thoracic subjects (151/104 and 170/121 mmHg). During ejaculation, 6 cervical and 3 thoracic subjects developed arrhythmias (5 with bradycardia, 6 with premature atrial contractions, 4 with ventricular excitation, 1 with junctional rhythm, and 1 with heart block).

CONCLUSION

The vibrostimulation procedure induced electrocardiographic abnormalities and autonomic dysreflexia in subjects with either cervical or high thoracic SCI.

Which pathways must be spared in the injured human spinal cord to retain cardiovascular control?

Cardiovascular abnormalities following spinal cord injury are attributed to autonomic instability caused by a combination of changes occurring within the spinal cord, including loss of descending autonomic control and plastic changes within spinal and peripheral circuits. Previous animal studies have shown that localized disruption of the descending vasomotor pathways results in cardiovascular changes similar to those observed following cord injury. However, the location of these pathways in humans is uncertain. This chapter presents clinical and histopathological findings from individuals with spinal cord injury that associates a common area of white matter destruction with severe cardiovascular symptoms. These data provide evidence that descending vasomotor pathways in the human spinal cord project through the dorsal aspects of the lateral funiculus.

Effect of a convenient single 90-mg pamidronate dose on biochemical markers of bone metabolism in patients with acute spinal cord injury

BACKGROUND/OBJECTIVE

To describe the biochemical and adverse effects of a convenient single 90 mg pamidronate dose in patients with acute spinal cord injury (SCI) and compare these effects with those observed in a previous similar study using a 30 mg/d x 3-day pamidronate dosing regimen.

STUDY DESIGN

Retrospective cohort study.

SETTING

University-based rehabilitation center in New York City.

METHODS

A total of 32 patients with SCI were evaluated for biochemical response and adverse events associated with pamidronate therapy. All patients were screened at or near admission for acute rehabilitation, received calcium (1,000 mg daily) and calcitriol (0.25 micrg daily) therapy daily, and on day 4, received a single dose of pamidronate, 90 mg by intravenous infusion, over 4 hours. Serum calcium and phosphate levels were closely monitored, and 2 weeks after pamidronate, biochemical bone markers were re-evaluated.

RESULTS

Responses of biochemical markers of bone resorption (N-telopeptide and 24-hour urinary calcium excretion) to pamidronate 90 mg were consistent with an antiresorptive effect, although less than that observed with a 30 mg/d x 3-day pamidronate dosing regimen. The frequency of hypocalcemia was greater, and hypophosphatemia was less than the 30 mg/d x 3-day pamidronate dosing regimen. Fever was more frequent (78%) with the 90-mg single dose of pamidronate compared with the 30 mg/d x 3-day pamidronate dosing regimen (20%).

CONCLUSIONS

Single-dose pamidronate 90 mg is effective at reducing biochemical markers of bone hyperresorption in patients with acute SCI but is associated with a greater incidence of fever compared with a 30 mg/d x 3-day dosing regimen.

Central nervous system injury-induced immune deficiency syndrome

Infections are a leading cause of morbidity and mortality in patients with acute CNS injury. It has recently become clear that CNS injury significantly increases susceptibility to infection by brain-specific mechanisms: CNS injury induces a disturbance of the normally well balanced interplay between the immune system and the CNS. As a result, CNS injury leads to secondary immunodeficiency - CNS injury-induced immunodepression (CIDS) - and infection. CIDS might serve as a model for the study of the mechanisms and mediators of brain control over immunity. More importantly, understanding CIDS will allow us to work on developing effective therapeutic strategies, with which the outcome after CNS damage by a host of diseases could be improved by eliminating a major determinant of poor recovery.

Orthostatic hypotension following spinal cord injury: understanding clinical pathophysiology

Motor and sensory deficits are well-known consequences of spinal cord injury (SCI). During the last decade, a significant number of experimental and clinical studies have focused on the investigation of autonomic dysfunction and cardiovascular control following SCI. Numerous clinical reports have suggested that unstable blood pressure control in individuals with SCI could be responsible for their increased cardiovascular mortality. The aim of this review is to outline the incidence and pathophysiological mechanisms underlying the orthostatic hypotension that commonly occurs following SCI. We describe the clinical abnormalities of blood pressure control following SCI, with particular emphasis upon orthostatic hypotension. Possible mechanisms underlying orthostatic hypotension in SCI, such as changes in sympathetic activity, altered baroreflex function, the lack of skeletal muscle pumping activity, cardiovascular deconditioning and altered salt and water balance will be discussed. Possible alterations in cerebral autoregulation following SCI, and the impact of these changes upon cerebral perfusion are also examined. Finally, the management of orthostatic hypotension will be considered.

Fasting serum levels of adiponectin, ghrelin, and leptin in men with spinal cord injury

OBJECTIVES

To measure serum levels of adiponectin, ghrelin, and leptin in men with spinal cord injury (SCI) and to investigate possible correlations between these serum levels and various factors, such as body mass index (BMI), age, injury level, and duration of injury.

DESIGN

Cross-sectional.

SETTING

A university hospital that is a tertiary referral center.

PARTICIPANTS

Eighty-nine men with traumatic neurologically complete SCI (30 with tetraplegia, 59 with paraplegia) and 37 age- and BMI-matched male controls. Subjects with SCI were injured at the mean age +/- standard error of 28.5+/-1.0 years (range, 14.7-59.1 y) and the mean injury duration was 10.8+/-0.7 years (range, 1.1-27.7 y).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Serum levels of adiponectin, ghrelin, and leptin and BMI.

RESULTS

Serum leptin levels in subjects with SCI (mean, 7.0+/-0.5 mg/mL) [corrected] were significantly higher than those in able-bodied controls (mean, 4.7+/-0.6 mg/mL) [corrected] (P<.01). The group with tetraplegia had higher serum leptin levels than the group with paraplegia, but this did not reach a statistically significant level (8.2+/-1.1 ng/mL vs 6.4+/-0.5 mg/mL [corrected] P=.097). There were significant differences in serum leptin levels among the 3 groups by 1-way analysis of variance (P=.008). Serum adiponectin levels in subjects with SCI (7.1+/-0.5 mg/mL) [corrected] were higher than those in able-bodied controls (5.6+/-0.5 mg/mL) [corrected] but this was not statistically significant (P=.08). In contrast, serum levels of ghrelin in subjects with SCI (302.0+/-17.5 pg/mL) were similar to those in the controls (264.0+/-27.0 pg/mL) (P=.24). Serum leptin levels correlated positively with BMI (SCI, r=.698, P<.001; controls, r=.782, P<.001), whereas serum adiponectin (SCI, r=-.527, P<.001; controls, r=-.315, P=.057) and ghrelin (SCI, r=-.368, P<.001; controls, r=-.447, P=.006) levels correlated negatively with the BMI in both subjects with SCI and controls.

CONCLUSIONS

Men with SCI have significantly higher serum leptin levels than able-bodied controls, and serum leptin levels correlated with the degree of neurologic deficit. Men with SCI had a tendency toward higher serum adiponectin level than able-bodied controls. Serum levels of ghrelin in men with SCI were similar to those of controls.

Malignant autonomic dysreflexia in spinal cord injured men

STUDY DESIGN

Case reports.

OBJECTIVES

To present a series of cases of protracted and severe autonomic dysreflexia (AD) in men with spinal cord injury (SCI), who sustained damage to their descending autonomic pathways.

SETTINGS

GF Strong Rehabilitation Centre, Sexual Health Rehabilitation Service, Vancouver Sperm Retrieval Clinic, Vancouver Coastal Health Authority, Vancouver, BC, Canada.

CASE REPORT

AD is a serious complication of SCI triggered by a variety of noxious or non-noxious stimuli below the level of injury. However, we are presenting three cases of protracted, severe AD we have termed 'malignant', owing to the tendency of progressive worsening not usually seen with AD once the alleviating factor is removed. In all three individuals, AD was initially triggered by ejaculation and continued for a period of more than 1 week. Systolic blood pressure in these individuals increased above 220 mmHg and required either acute hospitalization or hospital assessment. Two of the individuals with malignant AD had American Spinal Injury Association (ASIA) B and C high cervical injury, respectively, with the third having a high thoracic ASIA A injury. In addition to detailed history and neurological examination, electrophysiological assessment of sympathetic skin responses (SSR) demonstrated a significant disruption of the descending autonomic pathways in these individuals.

CONCLUSIONS

Our findings suggest that in addition to the severe injury of the motor and sensory pathways (assessed by ASIA score), these individuals sustained severe injury to the supraspinal autonomic control. A combination of strong triggers such as ejaculation and bladder or colono-rectal irritation with total loss of descending autonomic control to the spinal sympathetic circuits could therefore contribute to the unusual manifestation of AD.

Enhanced neurally evoked responses and inhibition of norepinephrine reuptake in rat mesenteric arteries after spinal transection

In patients with high thoracic spinal lesions that remove most of the central drive to splanchnic preganglionic neurons, visceral or nociceptive stimuli below the lesion can provoke large increases in blood pressure (autonomic dysreflexia). We have examined the effects of T4 spinal transection on isometric contractions of mesenteric arteries isolated from spinalized rats. Nerve-evoked contractions involved synergistic roles for norepinephrine and ATP. At 7 wk after spinal transection, responses to perivascular stimulation at 1-5 Hz were enhanced fivefold, whereas the alpha1-adrenoceptor antagonist prazosin (10 nM) produced a twofold larger reduction in contraction (to 20 pulses at 10 Hz) than in unoperated controls. In contrast, the reduction in nerve-evoked contractions by the P2-purinoceptor antagonist suramin (0.1 mM) and the responses to the P2-purinoceptor agonist alpha,beta-methylene ATP or to high K+ concentration did not greatly differ between groups, indicating that arteries from spinalized rats were not generally hyperreactive. Sensitivity to the alpha1-adrenoceptor agonist phenylephrine was enhanced in arteries from spinalized rats, and the difference from controls was abolished by the norepinephrine uptake blocker desmethylimipramine. Sensitivity to the alpha1-adrenoceptor agonist methoxamine, which is not a substrate for the neuronal norepinephrine transporter, was similar among the groups. Thus the increased neurally evoked response after spinal transection appeared to be due to a reduction in neuronal uptake of released norepinephrine, a mechanism that did not explain the enhanced response of tail arteries after spinal transection that we previously reported. The findings provide further support for potentiated neurovascular responses contributing to the genesis of autonomic dysreflexia.

Response of the arterial blood pressure of quadriplegic patients to treadmill gait training

Blood pressure pattern was analyzed in 12 complete quadriplegics with chronic lesions after three months of treadmill gait training. Before training, blood pressure values were obtained at rest, during treadmill walking and during the recovery phase. Gait training was performed for 20 min twice a week for three months. Treadmill gait was achieved using neuromuscular electrical stimulation, assisted by partial body weight relief (30-50%). After training, blood pressure was evaluated at rest, during gait and during recovery phase. Before and after training, mean systolic blood pressures and heart rates increased significantly during gait compared to rest (94.16 +/- 5.15 to 105 +/- 5.22 mmHg and 74.27 +/- 10.09 to 106.23 +/- 17.31 bpm, respectively), and blood pressure decreased significantly in the recovery phase (86.66 +/- 9.84 and 57.5 +/- 8.66 mmHg, respectively). After three months of training, systolic blood pressure became higher at rest (94.16 +/- 5.15 mmHg before training and 100 +/- 8.52 mmHg after training; P < 0.05) and during gait exercise (105 +/- 5.22 mmHg before and 110 +/- 7.38 mmHg after training; P < 0.05) when compared to the initial values, with no changes in heart rate. No changes occurred in blood pressure during the recovery phase, with the lower values being maintained. A drop in systolic pressure from 105 +/- 5.22 to 86.66 +/- 9.84 mmHg before training and from 110 +/- 7.38 to 90 +/- 7.38 mmHg after training was noticed immediately after exercise, thus resulting in hypotensive symptoms when chronic quadriplegics reach the sitting position from the upright position.

Metabolic and cardiorespiratory responses of tetraplegic subjects during treadmill walking using neuromuscular electrical stimulation and partial body weight support

STUDY DESIGN

Determination of differences in the cardiorespiratory responses of tetraplegic subjects with incomplete and complete lesions during treadmill gait and endurance exercise provided by neuromuscular electrical stimulation (NMES). Differences between rest and exercise phases were also examined.

OBJECTIVES

To compare the cardiorespiratory responses in tetraplegic individuals during endurance exercise in the sitting position and treadmill gait with 30-50% body weight relief, both provided by NMES.

SETTING

Rehabilitation Ambulatory at University Hospital, Brazil.

METHODS

A total of 31 tetraplegic subjects were evaluated. Individuals were separated into two groups: gait group and endurance exercise group. In the gait group (n=17), the exercise protocol consisted of three different phases: 8 min of rest, 10 min of treadmill walking using NMES and 10 min of recovery. In the endurance exercise group (n=14), the cardiorespiratory test consisted of 8 min of rest, 15 min of quadriceps endurance exercise in the sitting position by NMES and 10 min of recovery. Oxygen uptake (VO(2)), carbon dioxide production (VCO(2)), respiratory exchange ratio (RER), pulmonary ventilation (V(E)) and heart rate (HR) were measured.

RESULTS

All parameters increased considerably in the gait group from rest to the walking phase, although individuals with incomplete lesions presented a more pronounced increase than those with complete lesion. In the gait group, for incomplete tetraplegics, the mean VO(2) peak was 0.816+/-0.314 l/min, corresponding to 11.41+/-3.11 ml/kg/min; the mean value for VCO(2) was 0.660+/-0.24 l/min, mean HR was 124.54+/-28.72 bpm and mean V(E) was 28.38+/-6.28 l/min. In the endurance exercise group, for incomplete tetraplegics, the mean VO(2) peak was 0.246+/-0.07 l/min, corresponding to 3.84+/-0.92 ml/kg/min; the mean value for VCO(2) was 0.205+/-0.06 l/min, mean HR was 71.45+/-15.51 bpm and mean V(E) was 11.83+/-2.72 l/min. In the endurance exercise group, smaller differences were observed in all variables from rest to the exercise phase, compared with the large increases observed in the gait group.

CONCLUSIONS

These preliminary results have shown that gait training probably improves physical capacity in tetraplegic individuals more than the endurance exercise.

Energy expenditure during rest and treadmill gait training in quadriplegic subjects

STUDY DESIGN

The analysis of oxygen uptake (VO(2)) and energy consumption in quadriplegics after 6 months of treadmill gait with neuromuscular electrical stimulation (NMES).

OBJECTIVES

To compare metabolic responses in quadriplegics after 6 months of treadmill training, with NMES (30-50% body weight relief), with quadriplegics who did not perform gait.

SETTING

Ambulatory of University Hospital, Brazil.

METHODS

Quadriplegics were separated into gait and control groups (CGs). On inclusion, all subjects performed VO(2) test. In the gait group (GG) (n=11), the protocol consisted of 8 min of rest, 10 min of treadmill walking using NMES and 10 min of recovery. In the CG (n=10), testing consisted of 8 min rest, 15 min of quadriceps endurance exercise in sitting position with NMES and 10 min recovery. VO(2), carbon dioxide production (VCO(2)) and energy consumption were measured. The GG performed 6 months of treadmill training, using NMES, for 20 min, twice a week. The CG did not practice any activity with NMES, performing conventional physiotherapy only; the CG was stimulated only during the cardiorespiratory test.

RESULTS

All parameters increased significantly for the GG: 36% for VO(2) (l/min), 43% for VCO(2) (l/min) and 32.5% for energy consumption (J/kg/s). For the CG, during knee extension exercise, VO(2) increased without changes in the energy consumption (P<0.05); smaller values were obtained for all parameters when compared to those obtained during gait.

CONCLUSIONS

Quadriplegic gait was efficient towards increasing VO(2) and energy consumption, which can decrease the risk of cardiovascular diseases.

Réentraînement a l'effort chez le blesse médullaire

INTRODUCTION

Individualised exercise training programs in spinal cord injury (SCI) individuals are considered highly effective for improving and maintaining capacity for physical activity, as well as for reducing cardiovascular risk. However, no consensus exists on the type, intensity, and frequency of the training programs for SCI.

OBJECTIVE

To review the literature about training program characteristics for SCI and describe their efficacy, limits, and results, with the aim of proposing specific recommendations.

METHODS

Query using Medline and Embase databases. Ninety-nine references were found, including the following: Clinical studies examining physical endurance capacity of individuals with SCI, physiological responses to maximal exercise, or cardiovascular differences between sedentary and wheelchair-trained subjects; Articles? investigating the effects of training programmes for SCI.

RESULTS

Various combinations of training intensity, duration, frequency, type, and ergometers have been proposed for SCI. Whatever the characteristics of the training program, a review of 25 cardiorespiratory training studies involving SCI subjects revealed an average improvement of 9% to 99% in VO2max, 19% to 118% in power output, and a decrease in submaximal values after 4 to 36 weeks of training.

DISCUSSION - CONCLUSION

Wheelchair ergometers seems to be interesting for SCI because it mimics closely the daily motor tasks of wheelchair users and allows for adjustment of the wheelchair. Both continuous and interval training programmes are appropriate, but intermittent exercise intensities may be more beneficial since they mimic the intermittent nature of daily activity patterns. Furthermore, on the basis of the results of these studies, we recommend that training at or above 70% of maximum heart rate, for 30 minutes of rhythmic exercise, three days per week during eight weeks, will provide a sound of basis for design of an endurance exercise programme for people with SCI.

Systemic microcirculation after complete high and low thoracic spinal cord section in rats

Spinal cord injury (SCI) produces multiple systemic and metabolic alterations. Although some systemic alterations could be associated with ischemic organ damage, little is known about microvascular blood flow (MVBF) in organs other than the spinal cord after acute SCI. We used laser Doppler flowmetry in anesthetized rats to assess MVBF in several tissues before and after complete T-2 and T-9 SCI at 1 h and on days 1, 3, and 7 post-SCI. Mean arterial blood pressure (MAP), heart rate and hematologic variables also were recorded. MAP changes after T-2 injury were not significant, while MAP decreased significantly 1 h after T-9 injury. Statistically significant bradycardia occurred after T-2 injury at 7 days; statistically significant tachycardia occurred after T-9 injury at 1, 3, and 7 days. Hematocrit significantly increased at day 1 and decreased at days 3 and 7 after T-2 injury. SCI was associated with significant decreases in MVBF in liver, spleen, muscle and fore footpad skin. Changes in MVBF in hind footpad skin and kidney were not significant. Changes were more pronounced at 1 h and 1 day post-SCI. Significant differences between MVBF after T-2 and T-9 SCI occurred only in liver. MVBF significantly correlated with regional peripheral vascular resistances (assessed using the MAP/MVBF ratio), but not with MAP. In conclusion, organ-specific changes in systemic MVBF that are influenced by the level of SCI, could contribute to organ dysfunction.

Autonomic dysreflexia during sperm retrieval in spinal cord injury: influence of lesion level and sildenafil citrate

Autonomic dysreflexia (AD) can occur during penile vibratory stimulation in men with spinal cord injury, but this is variable, and the association with lesion level is unclear. The purpose of this study was to characterize the cardiovascular responses to penile vibratory stimulation in men with spinal cord injury. We hypothesized that those with cervical injuries would demonstrate a greater degree of AD compared with men with thoracic injuries. We also questioned whether the rise in blood pressure could be attenuated by sildenafil citrate. Participants were classified as having cervical (n = 8) or thoracic (n = 5) injuries. While in a supine position, subjects were instrumented with an ECG, and arterial blood pressure was determined beat by beat. Subjects reported to the laboratory twice and received an oral dose of sildenafil citrate (25-100 mg) or no medication. Penile vibratory stimulation was performed using a handheld vibrator to the point of ejaculation. At ejaculation during the nonmedicated trials, the cervical group had a significant decrease in heart rate (-5-10 beats/min) and increase in mean arterial blood pressure (+70-90 mmHg) relative to resting conditions, whereas the thoracic group had significant increases in both heart rate (+8-15 beats/min) and mean arterial pressure (+25-30 mmHg). Sildenafil citrate had no effect on the change in heart rate or mean arterial pressure in either group. In summary, men with cervical injuries had more pronounced AD during penile vibratory stimulation than men with thoracic injuries. Administration of sildenafil citrate had no effect on heart rate or blood pressure during penile vibratory stimulation in men with spinal cord injury.

H-reflex and physiologic measures of ejaculation in men with spinal cord injury11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the author(s) or on any organization with which the author(s) is/are associated

OBJECTIVE

To investigate the various physiologic parameters characterizing and predicting ejaculation.

DESIGN

Single case-control study.

SETTING

A referred care center and university setting.

PARTICIPANTS

Two men with spinal cord injury (SCI) and 2 control subjects.

INTERVENTION

Subjects were asked to self-stimulate with a Ferticare vibrator to induce ejaculation over 5 to 8 independent sessions.

MAIN OUTCOME MEASURES

Penile tumescence, blood pressure, heart rate, electromyographic activity of the bulbocavernosus muscles, abdominal muscles, soleus H-reflex, and occurrence of ejaculation.

RESULTS

Changes on all measures were observed, with penile tumescence being more stable in control subjects. Blood pressure increased in both groups, whereas tachycardia was observed in controls and bradycardia in subjects with SCI. H-reflex dropped slightly in controls but increased in subjects with SCI. Muscular patterns differed on ejaculatory success or failure.

CONCLUSIONS

Physiologic changes on all measures can be observed in men with SCI as a function of ejaculation. Changes include hypertension and bradycardia, characteristic of hyperreflexia, and tachycardia in controls. The neural mechanisms underlying these patterns are discussed. H-reflex showed increased spinal cord excitability in subjects with SCI after ejaculation, which suggests spasticity. The results support investigation of the H-reflex to predict ejaculatory success or failure in men with SCI, along with specific analysis of muscular patterns.

Autonomic Dysreflexia, Induced by Noxious or Innocuous Stimulation, Does Not Depend on Changes in Dorsal Horn Substance P

After experimental spinal cord injury (SCI) in rats, autonomic dysreflexia is commonly induced by slightly noxious cutaneous or visceral stimuli. The presence of autonomic dysreflexia is associated with an increase in the afferent fiber arbor area labeled by cholera toxin B or with an anti-CGRP antibody. Our goal was to examine further the sensory afferent input contributing to exaggerated autonomic spinal reflexes and subsequent increases in blood pressure after SCI, typical of autonomic dysreflexia. We observed that changes in blood pressure and heart rate induced by slightly noxious stimuli (2.0-mL balloon colon distension, cutaneous pinch) were increased in magnitude with time after SCI. In contrast, cardiovascular responses induced by non-noxious stimuli (1.0-mL balloon colon distension, light stroking of hair) were relatively constant. We examined substance P-immunoreactive afferent fibers to identify type C, unmyelinated afferent fibers, and A delta lightly myelinated fibers in superficial and deeper laminae of the dorsal horn, respectively. The area of substance P-immunoreactive fibers was quantified in laminae I-V of the dorsal horn. Analysis revealed no difference in substance P afferent fiber area in laminae I-II, or laminae III-V, between sham-injured and SCI rats. These data suggest that noxious, or innocuous, stimulation induces autonomic dysreflexia without expansion of the central arbors of substance P-immunoreactive sensory neurons. Furthermore, autonomic dysreflexia induced by noxious stimulation increases with time after spinal cord injury.

Is there a relationship between chronic pain and autonomic dysreflexia in persons with cervical spinal cord injury?

The purpose of this study was to define the relationships among clinical characteristics of chronic pain, injury characteristics, affective factors and autonomic dysreflexia (AD) in people with chronic cervical spinal cord injury (SCI). A survey containing questions concerning the presence of AD, demographic factors, clinical characteristics of pain and affective symptoms, was mailed to people with traumatic SCI and chronic pain included in the Miami Project to Cure Paralysis database. Of all subjects (n = 330) reporting chronic pain in a previous study, 181 had cervical injuries. Of this subset, 117 (64.6%) participated in the study. Thirty-five people (29.9%) reported AD in our study. Although intense pain has previously been reported to trigger AD, the average pain intensity was not predictive of AD. Pair-wise comparisons indicated that people reporting AD marked significantly more painful areas in the drawing and used more descriptive pain adjectives. Anxiety and sadness were significantly more frequent among people with AD. Furthermore, aggravation of pain due to muscle spasms, infections, full bladder, and constipation was significantly more common among people with AD. The logistic regression analysis indicated that a combination of having widespread pain, experiencing aggravation of pain due to infections, having a complete injury, and experiencing anxiety significantly predicted AD. Our results suggest that relationships between chronic pain and AD exist. Since multiple pain types are common after SCI and may be associated with AD, it is important to determine which pain types that may be particularly important for the condition of AD.

Spinal interneurons infected by renal injection of pseudorabies virus in the rat

The potency of spinal sympathetic reflexes is increased after spinal injury, and these reflexes may result in life-threatening hypertensive crises in humans. Few, if any, primary afferents project directly to sympathetic preganglionic neurons (SPN). Therefore, spinal sympathetic interneurons (IN) must play a major role in generating dysfunctional sympathetic activity after spinal cord injury. Furthermore, these IN are potentially aberrant targets, either for ascending and descending axons that may sprout after spinal cord injury or for axons that regenerate after spinal cord injury. We identified IN via the transsynaptic retrograde transport of pseudorabies virus (PRV) injected into the kidneys of rats. The proportion of infected IN ranged from approximately 1/3 to approximately 2/3 of the number of infected SPN. IN were heavily concentrated among the SPN in spinal lamina VII. However, IN were located in all lamina of the dorsal horn. The longitudinal distribution of infected IN was closely correlated with the longitudinal distribution of infected SPN. Few infected IN were found rostral or caudal to the longitudinal range of infected SPN. Infected IN were heterogeneous in both their sizes and the extent of their dendritic trees. The strong correlation between longitudinal distributions of infected IN and SPN supports physiological data demonstrating a segmental organization of spinal sympathetic reflexes. The paucity of infected IN in segments distant from SPN suggests that multisegmental sympathetic reflexes are mediated by projections onto IN rather than onto SPN themselves. The morphological heterogeneity of IN probably manifests the variety of systems that affect spinal sympathetic regulation.

Foot Cooling Reduces Exercise-Induced Hyperthermia in Men with Spinal Cord Injury

The number of individuals with spinal cord injury (SCI) participating in sports at recreational and elite levels is on the rise. However, loss of autonomic nervous system function below the lesion can compromise thermoregulatory capacity and increase the risk of heat stress relative to able-bodied (AB) individuals.

PURPOSE

To test the hypotheses that exercise in a heated environment would increase tympanic temperature (TTY) more in individuals with SCI than AB individuals, and that foot cooling using a new device would attenuate the rise in TTY during exercise in both groups.

METHODS

Six subjects with SCI (lesions C5-T5) and six AB controls were tested in a heated environment (means +/- SEM, temperature = 31.8 +/- 0.2 degrees C, humidity = 26 +/- 1%) for 45 min at 66% +/- 5 of arm cranking VO2peak and 30 min of recovery on two separate occasions with foot cooling (FC) or no foot cooling (NC) in randomized order.

RESULTS

During exercise and recovery in both trials, SCI TTY was elevated above baseline (P < 0.001) but more so in the NC versus FC trial (1.6 +/- 0.2 degrees C vs 1.0 +/- 0.2 degrees C, respectively, P < 0.005). Within the AB group, TTY was elevated above baseline for both trials (P < 0.001) with peak increases of 0.5 +/- 0.2 degrees C and 0.3 +/- 0.2 degrees C for NC and FC, respectively. TTY, face, and back temperature were higher in both SCI trials compared with AB trials (P < 0.05). Heart rate during exercise and recovery was lower in the SCI FC versus SCI NC (P < 0.05).

CONCLUSION

These results suggest that extraction of heat through the foot may provide an effective way to manipulate tympanic temperature in individuals with SCI, especially during exercise in the heat.

Descending Vasomotor Pathways in Humans: Correlation between Axonal Preservation and Cardiovascular Dysfunction after Spinal Cord Injury

Cardiovascular dysfunction is common after cervical spinal cord injury (SCI) in humans. At least three spinal cord elements involved in cardiovascular control have been identified: descending vasomotor pathways (DVPs), sympathetic preganglionic neurons, and spinal afferents. However, little is known about the localization of the DVPs within the human spinal cord, which limits our understanding of the mechanisms of cardiovascular dysfunction after SCI. This study was undertaken to examine the association of cardiovascular abnormalities after SCI in humans with the severity of degeneration and axonal loss within the DVPs. A detailed chart review and histopathological examination of postmortem spinal cord tissue was conducted in individuals with cervical SCI (n = 7) and control individuals with an intact central nervous system (n = 5). Individuals with SCI were divided into group 1 (severe cardiovascular abnormalities) and group 2 (no/minor cardiovascular disturbances). The area of degeneration and the number of preserved axons within different areas of the spinal cord were quantitated using EMPIX imaging software. Two areas of possible localization of DVPs were investigated: area I, within the dorsal aspects of the lateral funiculus; and area II, within the white matter adjacent to the dorsolateral aspect of the lateral horn. Comparison of the extent of axonal degeneration in both SCI groups demonstrated that individuals in group 1 had more extensive axonal degeneration than those in group 2. The number of intact axons within areas I and II in individuals from group 1 was significantly lower than those from group 2 or control cases (p = 0.029; p = 0.028). The most dramatic axonal loss was observed within area I in individuals with cardiovascular dysfunction. We conclude that loss and degeneration of DVPs, which are localized within the dorsolateral aspects of the human spinal cord, contributes to abnormal cardiovascular control after SCI. This information adds to our knowledge of pathobiology of cardiovascular dysfunction after human SCI and may ultimately suggest novel therapeutic strategies as regenerative and reparative approaches become translated to the clinic.

Cardiovascular responses to endotracheal intubation in patients with acute and chronic spinal cord injuries

Endotracheal intubation usually causes transient hypertension and tachycardia. We investigated whether the cardiovascular responses to intubation change as a function of the time elapsed in patients with spinal cord injury. One-hundred-six patients with traumatic complete spinal cord injury were grouped into acute and chronic groups according to the time elapsed (less than and more than 4 wk after injury) and into those with quadriplegia and paraplegia according to the level of injury (above C7 and below T5): acute quadriplegia, n = 26; chronic quadriplegia, n = 27; acute paraplegia, n = 24; and chronic paraplegia, n = 29. Twenty-five patients with no spinal cord injury served as controls. Systolic arterial blood pressure (SAP), heart rate, and plasma concentrations of catecholamines were measured. The intubation did not affect SAP in either the acute or chronic quadriplegics, but it significantly increased SAP in both acute and chronic paraplegics. Heart rate was significantly increased in all groups; however, the magnitude of change was less in acute quadriplegics than in the other groups. Plasma concentrations of norepinephrine increased in every group but the acute quadriplegics. The magnitude of increase was attenuated in chronic quadriplegics, accentuated in acute paraplegics, and similar in chronic paraplegics when compared with controls. The incidence of arrhythmias did not differ among groups. We conclude that the cardiovascular and catecholamine responses to endotracheal intubation may change as a function of the time elapsed and the level of spinal cord injury.

IMPLICATIONS

Cardiovascular and catecholamine responses to endotracheal intubation may differ according to the time elapsed and the level of injury in patients with complete spinal cord injury.

Autonomic dysreflexia in response to pudendal nerve stimulation

STUDY DESIGN

Pudendal nerve stimulation in complete spinal cord injury (SCI).

OBJECTIVE

To evaluate the influence of pudendal nerve stimulation on the cardiovascular system in SCI patients in order to assess the underlying neuronal mechanism and the potential risk during stimulation.

SETTING

Swiss Paraplegic Center, and University Hospital, Zurich.

METHODS

A total of 22 male patients with a complete SCI were divided into two groups according to the level of lesion: group A (C6-T6, n=15) and group B (T7-L2, n=7). A total of 66 stimulations using biphasic rectangular impulses (0.2 ms, 10 Hz) with intensities up to 100 mA were applied to the dorsal penile nerve. Of these, 15 stimulations in five patients were repeated after intravenous application of 7 mg of phentolamine. Heart rate (HR) and blood pressure (BP) were recorded by a Finapres cuff applied to the right index finger.

RESULTS

Significant increased diastolic and systolic BP accompanied by significant decreased HR suggested the occurrence of autonomic dysreflexia (AD) during pudendal nerve stimulation. These cardiovascular changes corresponded with the subjective sensation of AD symptoms in patients of group A. Intravenous phentolamine lowered the resting BP and prevented severe hypertension during stimulation. Patients in group B presented with mild HR and BP changes in response to pudendal nerve stimulation and reported no AD symptoms.

CONCLUSION

Our results show a considerable effect of electrical pudendal nerve stimulation on HR and BP in patients with high SCI. This may indicate that sacral somatic afferent fibers of the pudendal nerve are involved in the neuronal mechanism of AD in SCI patients with high neurological level. Intravenous phentolamine enables pudendal nerve stimulation without the risk of severe hypertension.

Autonomic dysreflexia: a plastic surgery primer

Plastic surgeons are integral to the management team for patients with spinal cord injuries, with responsibilities including pressure sore management and upper extremity reconstruction. Injury to the spinal cord profoundly disrupts the body's ability to maintain homeostasis. In particular, the autonomic system can become unregulated, resulting in a massive sympathetic discharge called autonomic dysreflexia. Autonomic dysreflexia occurs in the majority of patients with injuries above the sixth thoracic vertebra and causes sudden, severe hypertension. If left untreated, autonomic dysreflexia can result in stroke or death. Because this syndrome causes morbidity and mortality, it is crucial for plastic surgeons to be able to recognize and treat autonomic dysreflexia. This article reviews the etiology, symptoms, and treatment of this syndrome.

Autonomic dysreflexia in acute spinal cord injury: an under-recognized clinical entity

While autonomic dysreflexia (AD) is well recognized in the chronic stage of spinal cord injury (SCI) this potentially life-threatening complication has been only rarely documented in the acute phase (1 month) after SCI. Based on our clinical experience we hypothesized that AD is under-recognized in the acute phase of SCI. This study was undertaken to determine the incidence and clinical associations of early AD in our center. We reviewed the charts of patients with acute traumatic SCI admitted to the Toronto Western Hospital Spinal Program between 1998 and 2000. Among 58 patients with acute traumatic SCI (15F, 43M; ages 17-89 years, mean of 55.4), all three individuals who developed evidence of early AD had complete cervical tetraplegia (1F, 2M; ages 31-42 years, mean of 38.3). The incidence of early AD was 5.2% (3 of 58), whereas the adjusted incidence for the population at risk (SCI at T6 or above) was 5.7% (3 of 53). A significant number of patients in this series (87.9%, or 51 of 58) had a cervical SCI. While the mean resting systolic arterial blood pressure among these three individuals was 105.7+/-3 mm Hg, the mean systolic blood pressure at the time of early AD was 173.3+/-14.8 mm Hg (increase in systolic blood pressure over baseline ranged from 35.5% to 95%). The earliest episode of AD occurred on the 4(th) post-injury day. The trigger mechanisms for AD were somatic pain, fecal impaction, and abdominal distention. Although numerous reports emphasize AD as a potential complication of chronic SCI, our study demonstrates that AD occurs in 5.7% of patients with acute SCI above T6. Patients with severe cervical SCI are particularly susceptible to the early onset of AD. Clinicians need to be aware and highly vigilant of the potential development of AD in the acute phase of SCI.

Critical care and perioperative management in traumatic spinal cord injury

Traumatic spinal cord injury is frequently associated with brain injury and with alterations in respiratory and cardiovascular function that require critical care management. Complications include respiratory failure, atelectasis, pneumonia, neurogenic shock, autonomic dysreflexia, venous thromboembolism, and sepsis. While complications may be managed with supportive care, the goal of ameliorating neurologic outcome has proved elusive. Methylprednisolone, when instituted <8 hours after traumatic spinal cord injury, was associated in two clinical trials with statistically significant improvements in motor scores at 6 months and 1 year; however, critical reappraisal of these data raises questions about their validity and clinical relevance. Until more evidence of clinically effective therapies is available, acute management must be driven by pathophysiologic principles, with emphasis on interventions that attenuate secondary neurologic injury; these include the rational use of immobilization, cautious airway management, and promotion of cord perfusion and oxygenation with the appropriate level of hemodynamic and respiratory support. Clinical trials of pharmacologic neuroprotection have yielded disappointing results, but the ongoing elucidation of spinal cord repair and regenerative mechanisms suggests new therapeutic prospects.

Medical co-morbidities, secondary complications, and mortality in elderly with acute spinal cord injury

Despite an increasing incidence of spinal cord injury (SCI) in the elderly and evidence that age appears to influence outcome after neurotrauma, surprisingly little is known regarding clinical outcomes and secondary complications in elderly with an acute SCI. This study was undertaken to evaluate the effect of age on clinical outcomes after acute traumatic SCI managed in an acute care unit by a multidisciplinary team. A retrospective chart review of all patients with acute SCI admitted to an acute care unit at a university hospital between 1998 and 2000 was performed. Data on clinical outcomes and secondary complications in younger individuals (group 1: age < 60 years) were compared to elderly subjects (group 2: age > or = 60 years). There were 28 elderly (age 60-89 years) and 30 younger (age 17-56 years) individuals. The severity and level of SCI were similar in both groups (p = 0.11; p = 0.93). Co-morbidities were more frequent in the elderly (p < 0.01). There was a trend, which did not achieve significance, for an increased incidence of secondary complications in the elderly (57.1% versus 33.3%; p = 0.11). The most common secondary complications in both groups were infections, psychiatric disorders, pressure sores, and cardiovascular complications. Mortality rates in elderly and younger individuals with acute SCI (p = 0.41) were not significantly different. Our data suggest that rigorous attention to principles of acute SCI care can minimize previously reported higher susceptibility for secondary complications in the elderly. A multidisciplinary team approach to the management of the elderly with acute SCI is essential to minimize or prevent secondary complications.

Arterial vascular properties in individuals with spina bifida

STUDY DESIGN

Observational cross-sectional study.

OBJECTIVE

To assess the vascular characteristics of the arterial circulation in individuals with spina bifida (SB) in comparison with individuals with spinal cord injury (SCI) and able-bodied controls (C).

SETTING

University Medical Centre, Nijmegen, The Netherlands.

METHODS

Six spina bifida (SB), 15 spinal cord injury (SCI) and 10 C were included. Red blood cell velocities and arterial diameter of the common carotid artery and common femoral artery were measured using echo-Doppler ultrasound in a supine position. A venous blood sample was withdrawn for determination of blood viscosity.

RESULTS

In the common carotid artery, blood flow and wall shear stress were not different between the three groups. The diameter was smaller in SB compared with SCI and C. In the common femoral artery, blood flow was smaller in SB than in SCI and C. Wall shear stress was significantly higher in SB and SCI compared with C. High wall shear stress may lead to endothelial dysfunction and related cardiovascular disease.

CONCLUSION

Deteriorating vascular properties are present in SB as well as in spinal-cord-injured individuals in comparison with C. These properties tend to be more pronounced in SB than in SCI.

Silent autonomic dysreflexia during a routine bowel program in persons with traumatic spinal cord injury: a preliminary study

OBJECTIVE

To determine the existence and frequency of silent autonomic dysreflexia in subjects with a complete spinal cord injury (SCI) above the neurologic level of T6.

DESIGN

Prospective design.

SETTING

Blood pressure monitoring of subjects during a routine bowel program.

PARTICIPANTS

Ten subjects with chronic (>1 y), complete (American Spinal Injury Association Impairment Scale class A) SCI with a neurologic level of injury above T6.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

An increase in systolic blood pressure (SBP) of greater than 20 to 40 mmHg above baseline or an SBP greater than 150 mmHg.

RESULTS

The mean resting blood pressure for the subject group was 104/65 mmHg. During the bowel program, no subject reported experiencing any of the classic symptoms of autonomic dysreflexia. The mean maximum blood pressure recorded during the bowel program was 160/90 mmHg. All of the patients had an increase in SBP greater than 20 mmHg above baseline, and 70% had an increase in SBP greater than 40 mmHg above baseline. Sixty percent of subjects had an increase in SBP greater than 150 mmHg, with 40% of subjects reaching an SBP greater than 170 mmHg at least once during their bowel program.

CONCLUSION

Silent autonomic dysreflexia occurs frequently in SCI during bowel programs. Further study is recommended to determine whether preventative measures or treatment is needed.

Sensitivity of sympathetically correlated spinal interneurons, renal sympathetic nerve activity, and arterial pressure to somatic and visceral stimuli after chronic spinal injury

In the chronic stage of spinal cord injury in humans, both innocuous and noxious somatic and visceral stimuli can elicit severe autonomic dysreflexia characterized by potentially dangerous, sympathetically mediated, increases in arterial pressure. We hypothesized that a similar sympathetic hyperexcitability would be manifested in spinal sympathetic networks of chronically spinally transected rats. To test this hypothesis, we compared the responses of sympathetically correlated spinal interneurons and arterial pressure to both innocuous and noxious stimuli in acutely and chronically spinally transected rats. Experiments were conducted in anesthetized female rats, either within hours of T(3) spinal transection (rats with acute spinal transection) or one month after T(3) spinal transection (rats with chronic spinal transection). Sympathetically correlated spinal interneurons were identified by cross correlating their ongoing activity with simultaneously recorded renal sympathetic nerve activity. Cutaneous stimuli (either light brushing or noxious pinch) were delivered to a wide area of the ipsilateral side of the rat. Colorectal distension was used as a noxious visceral stimulus. The activity of sympathetically correlated interneurons was increased by stimulation of more of the body surface and decreased by stimulation of less of the body surface in rats with chronic spinal transection than in rats with acute spinal transection. Colorectal distension elicited greater increases in arterial pressure in chronically than acutely spinally-transected rats without exciting significantly more interneurons in those rats. These results suggest that spinal circuits undergo significant plastic changes in the chronic stage of spinal cord injury, and they provide a mechanism for the observation, in some human patients, that many stimuli, both noxious and non-noxious, applied caudal to the site of spinal injury increase sympathetic activity and arterial pressure.

Heart rate-arterial blood pressure relationship in conscious rat before vs. after spinal cord transection

This experiment quantified the initial disruption and subsequent adaptation of the blood pressure (BP)-heart rate (HR) relationship after spinal cord transection (SCT). BP and HR were recorded for 4 h via an implanted catheter in neurally intact, unanesthetized rats. The animals were then anesthetized, and their spinal cords were severed at T(1)-T(2) (n = 5) or T(4)-T(5) (n = 6) or sham lesioned (n = 4). BP was recorded for 4 h daily over the ensuing 6 days. The neurally intact rat showed a positive cross correlation, with HR leading BP at the peak by 1.8 +/- 0.8 (SD) s. The cross correlation in unanesthetized rats (n = 2) under neuromuscular blockade was also positive, with HR leading. After SCT at T(1)-T(2), the cross correlation became negative, with BP leading HR, and did not change during the next 6 days. The cross correlation also became negative 1-3 days after SCT at T(4)-T(5), but in four rats by day 6 and thereafter the cross correlation progressively reverted to a positive value. We propose that the positive cross correlation with HR leading BP in the intact rat results from an open-loop control that depends on intact supraspinal input to sympathetic preganglionic neurons in the spinal cord. After descending sympathetic pathways were severed at T(1)-T(2), the intact vagal pathway to the sinoatrial node dominated BP regulation via the baroreflex. We suggest that reestablishment of the positive correlation after SCT at T(4)-T(5) was attributable to the surviving sympathetic outflow to the heart and upper vasculature reasserting some effective function, perhaps in association with decreased spinal sympathetic hyperreflexia. The HR-BP cross correlation may index progression of sympathetic dysfunction in pathological processes.

The expression of Fos-labeled spinal neurons in response to colorectal distension is enhanced after chronic spinal cord transection in the rat

The present study used Fos-like immunoreactivity to examine neuronal activation in response to colorectal distension in rats at 1 day or 30 days following spinal cord transection or sham transection. Fifty-five Wistar rats were anesthetized and an incision was made to expose the T(5) spinal segment. The dura was reflected away in all rats and a complete transection at the rostral end of the T(5) segment was given to the lesioned group. At 1 day (acute) or 30 days (chronic) post-surgery, conscious rats were subjected to a 2 h period of intermittent colorectal distension. Rats were perfused and spinal segments L(5)-S(2) were removed and processed for Fos-like immunoreactivity. Spinal cord transection alone had no effect on Fos-labeling in either acute or chronic rats. In acute rats, colorectal distension produced significant increases in Fos-labeling in the superficial and deep dorsal horn regions. In chronic rats, colorectal distension produced a three-fold increase in Fos-labeled neurons that was manifest throughout all laminar regions. These results indicate that the number of neurons expressing Fos in response to colorectal distension is much greater after a chronic spinal cord transection than after an acute transection. Since Fos is an indicator of neuronal activation, the results show that many more neurons become active in response to colorectal distension following a chronic spinal injury. This suggests that a functional reorganization of spinal circuits occurs following chronic spinal cord transection. This may ultimately result in altered visceral and somatic functions associated with spinal cord injury in humans.

Abrupt withdrawal from intrathecal baclofen: recognition and management of a potentially life-threatening syndrome

OBJECTIVE

To suggest guidelines for the prevention, recognition, and management of a life-threatening syndrome (high fever, altered mental status, profound muscular rigidity that sometimes progressed to fatal rhabdomyolysis) in patients who experience the abrupt withdrawal of intrathecal baclofen (ITB) therapy.

DESIGN

Retrospective literature and safety-file review.

SETTING

Expert panel drawn from physiatry, neurology, and neurosurgery.

PARTICIPANTS

Experienced users of ITB therapy in the pediatric and adult populations in the United States.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

We reviewed literature reports, MedWatch reports to the US Food and Drug Administration, and our own experiences. We critically analyzed patient management and drug therapy in the context of the pharmacology of baclofen and other antispastic agents.

RESULTS

An abrupt reduction in gamma-aminobutyric acid(B) (GABA) agonist activity in the central nervous system can cause the ITB withdrawal syndrome, which is clinically and pathophysiologically distinct from autonomic dysreflexia, malignant hyperthermia, and neuroleptic-malignant syndrome. ITB withdrawal evolves over 1 to 3 days, but may become fulminant if not recognized and treated early. The syndrome can be interrupted by the restoration of ITB therapy. However, supportive measures and high-dose benzodiazepine infusion may be life saving in the interval before ITB therapy is resumed. Dantrolene infusion may relieve muscle rigidity but does not reverse the other manifestations of GABAergic agonist withdrawal.

CONCLUSIONS

Most episodes of severe ITB withdrawal were preventable. Patients at risk can be identified and educated prospectively and given medication for emergency use. Treatment with GABAergic agonist drugs may prevent potentially fatal sequelae.

Interlimb reflexes and synaptic plasticity become evident months after human spinal cord injury

Persons with long-standing injury to the cervical spinal cord resulting in complete or partial paralysis typically develop a wide spectrum of involuntary movements in muscles receiving innervation caudal to the level of injury. We have previously shown that these movements include brief and discrete contraction of muscles in the hand and forearm in response to innocuous sensory stimulation to the feet and legs, but we have been unable to replicate these interlimb reflexes in able- bodied subjects. Properties of these muscle responses indicate that the synaptic contacts between ascending sensory fibres and motor neurones of the cervical enlargement are more efficacious than normal. If these connections are present at all times, and require the more rostrally-placed spinal cord injury to allow their emergence, one might expect their appearance relatively soon following injury, as has been shown for studies of 'latent' synapses. Conversely, delayed appearance of these interlimb reflexes would suggest either the development of new synaptic connections or a profound strengthening of existing circuits in the cervical spinal cord due to a combination of afferent target loss and motor neurone denervation from motor tracts originating rostral to the injury site. In this study, we used repeated examinations of persons with acute injury to the cervical spinal cord to examine the time post-injury at which interlimb reflexes are first seen. Using tibial nerve stimulation at the knee as a screening test, a total of 24 subjects were found to develop interlimb reflexes following spinal cord injury. Latencies between stimulation and EMG were as brief as 32 ms for muscles of the forearm and 44 ms for muscles in the hand. These minimal delays all but rule out a supraspinal route for these interlimb reflexes. Interlimb reflexes first became evident no sooner than approximately 6 months following injury, and in some individuals were not seen until well over 1 year post-injury. Enhanced lower limb segmental excitability had emerged in nearly all of these subjects weeks or months prior to the first appearance of interlimb reflexes, arguing against a manifestation of traditional post-traumatic spasticity as a basis for this activity. This prolonged delay between time of injury and emergence of interlimb reflex activity lends support to the hypothesis that this activity represents an example of plasticity-and perhaps 'regenerative sprouting'-in the human spinal cord following traumatic injury.