Autonomic dysreflexia: Somatosympathetic and viscerosympathetic vasoconstrictor responses to innocuous and noxious sensory stimulation below lesion in human spinal cord injury

Mechanistic involvement of noradrenergic neuronal neurotransmitter release in cutaneous vasoconstriction during autonomic dysreflexia in persons with spinal cord injury

INTRODUCTION

Autonomic dysreflexia (AD) is a potentially life-threatening consequence in high (above T6) spinal cord injury that involves multiple incompletely understood mechanisms. While peripheral arteriolar vasoconstriction, which controls systemic vascular resistance, is documented to be pronounced during AD, the pathophysiological neurovascular junction mechanisms of this vasoconstriction are undefined. One hypothesized mechanism is increased neuronal release of norepinephrine and co-transmitters. We tested this by examining the effects of blockade of pre-synaptic neural release of norepinephrine and co-transmitters on cutaneous vasoconstriction during AD, using a novel non-invasive technique; bretylium (BT) iontophoresis followed by skin blood flow measurements via laser doppler flowmetry (LDF).

METHODS

Bretylium, a sympathetic neuronal blocking agent (blocks release of norepinephrine and co-transmitters) was applied iontophoretically to the skin of a sensate (arm) and insensate (leg) area in 8 males with motor complete tetraplegia. An nearby untreated site served as control (CON). Cutaneous vascular conductance (CVC) was measured (CVC = LDF/mean arterial pressure) at normotension before AD was elicited by bladder stimulation. The percent drop in CVC values from pre-AD vs. AD was compared among BT and CON sites in sensate and insensate areas.

RESULTS

There was a significant effect of treatment but no significant effect of limb/sensation or interaction of limb x treatment on CVC. The percent drop in CVC between BT and CON treated sites was 25.7±1.75 vs. 39.4±0.87, respectively (P = 0.004).

CONCLUSION

Bretylium attenuates, but does not fully abolish vasoconstriction during AD. This suggests release of norepinephrine and cotransmitters from cutaneous sympathetic nerves is involved in cutaneous vasoconstriction during AD.

Autonomic Dysreflexia following Spinal Cord Injury

Autonomic dysreflexia (AD) is a potentially life-threatening condition of the autonomic nervous system following spinal cord injury at or above T6. One of the most common symptoms is a sudden increase in blood pressure induced by afferent sensory stimulation owing to unmodulated reflex sympathetic hyperactivity. Such episodes of high blood pressure might be associated with a high risk of cerebral or retinal hemorrhage, seizures, heart failure, or pulmonary edema. In-depth knowledge is, therefore, crucial for the proper management of the AD, especially for spine surgeons, who encounter these patients quite often in their clinical practice. Systematical review of the literature dealing with strategies to prevent and manage this challenging condition was done by two independent reviewers. Studies that failed to assess primary (prevention, treatment strategies and management) and secondary outcomes (clinical symptomatology, presentation) were excluded. A bibliographical search revealed 85 eligible studies that provide a variety of preventive and treatment measures for the subjects affected by AD. As these measures are predominantly based on noncontrolled trials, long-term prospectively controlled multicenter studies are warranted to validate these preventive and therapeutic proposals.

The effects of GelMA hydrogel on nerve repair and regeneration in mice with spinal cord injury

Background

To determine the effects of gelatin methacryloyl (GelMA) hydrogel on nerve repair and regeneration in mice with spinal cord injury (SCI).

Methods

A total of 30 ICR mice (6–8 weeks old) were randomly assigned into the control group, the model group, and the experimental group via the random digits table method. There were 10 mice in each group. All mice underwent a T8 laminectomy. For mice in the experimental group and the model group, after the T8 laminectomy, SCI models were constructed by clamping the mice spinal cord tissue for 1 minute using an aneurysm clip (25 g). Additionally, the SCI area of each mouse in the experimental group was locally injected with 0.05–0.7 mL GelMA hydrogel [10% (w/v)] and photocrosslinking was initiated under a blue light source with a wavelength of 405 nm. The exercise performance of each mouse was tested via the bedside mobility scale (BMS) on post-operative days 1, 3, 7, and 14. After 14 days, mice were sacrificed and the dorsal root ganglion (DRG) sensory neurons were isolated and cultured for 3 days in vitro. The axon lengths of the neurons were then evaluated. Immunohistochemical staining was performed to assess the development of syringomyelia in the area. Western blots (WB) and immunofluorescence staining were performed to quantify the expression of glial fibrillary acidic protein (GFAP), growth associated protein (GAP)43, and nestin in the DRG neurons from each group of mice.

Results

Compared with mice in the control group, mice in the SCI model group showed a notable decrease in exercise ability, while the exercise ability of mice in the experimental group recovered markedly after treatment with GelMA hydrogel. Administration of GelMA hydrogel lengthened the axon of DRG neurons in mice and reduced the area of syringomyelia. Furthermore, GelMA hydrogel inhibited scar formation and promoted the recovery of neurological function by upregulating GAP43 and nestin expression and downregulating GFAP expression.

Conclusions

In mice with SCI, local injection of GelMA hydrogel strongly inhibited scar formation, reduced the area of syringomyelia, and promoted nerve regeneration and recovery of limb movement function.

Autonomic Hyperactivity

PURPOSE OF REVIEW

Autonomic hyperactivity is a relatively common consequence of severe acute brain injury and can also be seen with spinal cord and peripheral nerve disorders. This article reviews basic pathophysiologic concepts regarding autonomic hyperactivity, its various forms of clinical presentation, and practical management considerations.

RECENT FINDINGS

Paroxysmal sympathetic hyperactivity is most common after traumatic brain injury but can also occur after other forms of severe acute diffuse or multifocal brain injury. Formal criteria for the diagnosis and severity grading of paroxysmal sympathetic hyperactivity have now been proposed. A growing body of literature is beginning to elucidate the mechanisms underlying this disorder, but treatment remains based on observational data. Our mechanistic understanding of other distinct forms of autonomic hyperactivity, such as autonomic dysreflexia after traumatic spinal cord injury and dysautonomia after Guillain-Barré syndrome, remains rudimentary, yet clinical experience shows that their appropriate management can minimize the risk of serious complications.

SUMMARY

Syndromes of autonomic hyperactivity can result from injury at all levels of the neuraxis. Much more research is needed to refine our understanding of these disorders and guide optimal management decisions.

Autonomic dysreflexia in a case of radiation myelopathy and cisplatin-induced polyneuropathy

INTRODUCTION

While autonomic dysreflexia caused by severe spinal cord lesions can be life-threatening, relevant reports on non-traumatic spinal lesions are rare. Furthermore, modes of innervation of the supraspinal inhibitory pathways at each spinal sympathetic segment remain unknown. Herein, I report the case of a patient with autonomic dysreflexia and radiation myelopathy. The laterality of autonomic dysreflexia was investigated with special reference to the sudomotor function.

CASE PRESENTATION

A 51-year-old man with a history of epipharynx carcinoma, radiotherapy, and cisplatin chemotherapy was referred for the evaluation of autonomic function. He was ambulant but displayed spastic tetraparesis, areflexia of the extremities, sensory disturbance below C4 dermatome, dysuria, and impotence. Spinal magnetic resonance imaging demonstrated a cervical lesion involving the lateral portion of C2-C5, bilaterally. The thermal sweating test showed that sweating was lower on the left side of the face and neck, left shoulder, and arm than the corresponding parts on the right side. The rest of the body was anhidrotic. Sweating due to autonomic dysreflexia was symmetric, but more abundant on the left side of the face. Acetylcholine-induced sweating was markedly reduced on the left leg.

DISCUSSION

This might be the first documentation of autonomic dysreflexia observed in a patient with radiation myelopathy. The present observations suggested that the supraspinal inhibitory pathway to spinal preganglionic neurons may descend on the same side as thermal sudomotor facilitatory pathways at the cervical level. Furthermore, autonomic dysreflexia was more prominent in the standing position suggesting that the pressure stimulus might enhance autonomic dysreflexia.

Sudor Anglicus: an epidemic targeting the autonomic nervous system

Renaissance England witnessed a series of brief epidemics of a rapid and often fatal illness, the predominant feature of which was a disturbance of the autonomic nervous system. Profuse sweating was both an emblematic and ominous sign of this Sudor Anglicus. Its story is medically fascinating as well as historically noteworthy. Possible sites of pathological involvement include the hypothalamus, serotonergic neurons in the brainstem or spinal cord, autonomic ganglia, peripheral sympathetic nerves, neuroeffector junctions, or eccrine glands. Of candidate etiologic agents, a virus is most likely, given the seasonal variation, geographic clustering, and pattern of spread of the epidemics. Hantaviruses, enteroviruses, influenza, and others provide clinical comparisons, but a definitive match with known viruses has remained elusive.

Recognition and management of autonomic dysreflexia in patients with a spinal cord injury

Autonomic dysreflexia is a potentially life-threatening condition that affects patients with a spinal cord injury at the level of T6 or above. It is characterised by uncontrolled elevation of systolic blood pressure of more than 20mmHg, which may occur alongside bradycardia. This article explains the pathophysiology of autonomic dysreflexia, alongside its causes, signs and symptoms. It also details the pharmacological and non-pharmacological management interventions that should be promptly initiated in patients who present to the emergency department with autonomic dysreflexia, to alleviate their symptoms and prevent further complications.