Intrathecal pressure monitoring and cerebrospinal fluid drainage in acute spinal cord injury: a prospective randomized trial

Temporal changes of spinal subarachnoid space patency after graded spinal cord injury in rats

INTRODUCTION

Disturbances in spinal subarachnoid space (SSAS) patency after SCI have been reported as an incidental finding, but there is a lack of information on its in vivo extent and time course. For substances and cells carried in the cerebrospinal fluid (CSF) to reach damaged neural tissue and promote reparative processes, CSF must be able to flow freely in SASS.

OBJECTIVE

To characterise the extent and time course of SSAS patency disruption in vivo in a rat model after graded SCI.

MATERIALS AND METHODS

Anaesthetised rats were subjected to mild or severe cord contusion at T9. Estimation of SSAS patency was carried out at 1h and 1, 3, 7, 15, 30 and 90 days postinjury, as well as in naïve rats, by quantifying the passage of superparamagnetic beads injected into the CSF at the cisterna magna and recovered at spinal level L2. CSF volume recovery was measured simultaneously. Data were analysed by the two-way ANOVA test.

RESULTS

Estimation of SSAS patency revealed nearly complete blockage early after contusion that was unevenly restored entering the chronic stages. Volume of CSF recovered was also significantly decreased early after injury compared to naïve rats, but was fully restored by 1 month postinjury. Overall, although modestly different from each other, changes in both parameters were more pronounced after severe rather than mild injuries for each time point examined.

CONCLUSIONS

SCI alters SSAS patency. Its extent is a function primarily of time elapsed after lesion and secondly of injury severity. It is reasonable to expect that disturbances in SASS patency might alter CSF dynamics and impair self-reparative mechanisms and intrathecal therapeutics, making SSAS patency blockage a key target for SCI management.

Management of acute traumatic spinal cord injury

OPINION STATEMENT

Spinal cord injury (SCI) causes significant morbidity and mortality. Clinical management in the acute setting needs to occur in the intensive care unit in order to identify, prevent, and treat secondary insults from local ischemia, hypotension, hypoxia, and inflammation. Maintenance of adequate perfusion and oxygenation is quintessential and a mean arterial pressure >85-90 mm Hg should be kept for at least 1 week. A cervical collar and full spinal precautions (log-roll, flat, holding C-spine) should be maintained until the spinal column has been fully evaluated by a spine surgeon. In patients with SCI, there is a high incidence of other bodily injuries, and there should be a low threshold to assess for visceral, pelvic, and long bone injuries. Computed tomography of the spine is superior to plain films, as the former rarely misses fractures, though caution needs to be exerted as occipitocervical dislocation can still be missed. To reliably assess the spinal neural elements, soft tissues, and ligamentous structures, magnetic resonance imaging is indicated and should be obtained within 48-72 h from the time of injury. All patients should be graded daily using the American Spinal Injury Association classification, with the first prognostic score at 72 h postinjury. Patients with high cervical cord (C4 or higher) injury should be intubated immediately, and those with lower cord injuries should be evaluated on a case-by-case basis. However, in the acute setting, respiratory mechanics will be disrupted with any spinal cord lesion above T11. Steroids have become extremely controversial, and the professional societies for neurosurgery in the United States have given a level 1 statement against their use in all patients. We, therefore, do not advocate for them at this time. With every SCI, a spine surgeon must be consulted to discuss operative vs nonoperative management strategies. Indications for surgery include a partial or progressive neurologic deficit, instability of the spine not allowing for mobilization, correction of a deformity, and prevention of potential neurologic compromise. Measures to prevent pulmonary emboli from deep venous thromboembolisms are necessary: IVC filters are recommended in bedbound patients and low-molecular weight heparins are superior to unfractionated heparin. Robust prevention of pressure ulcers as well as nutritional support should be a mainstay of treatment. Lastly, it is important to note that neurologic recovery is a several-year process. The most recovery occurs in the first year following injury, and therefore aggressive rehabilitation is crucial.

NK1 receptor blockade is ineffective in improving outcome following a balloon compression model of spinal cord injury

The neuropeptide substance P (SP) is a well-known mediator of neurogenic inflammation following a variety of CNS disorders. Indeed, inhibition of SP through antagonism of its receptor, the tachykinin NK1 receptor, has been shown to be beneficial following both traumatic brain injury and stroke. Such studies demonstrated that administration of an NK1 receptor antagonist reduced blood-brain-barrier permeability, edema development and improved functional outcome. Furthermore, our recent studies have demonstrated a potential role for SP in mediating neurogenic inflammation following traumatic spinal cord injury (SCI). Accordingly, the present study investigates whether inhibition of SP may similarly play a neuroprotective role following traumatic SCI. A closed balloon compression injury was induced at T10 in New Zealand White rabbits. At 30 minutes post-injury an NK1 receptor antagonist was administered intravenously. Animals were thereafter assessed for blood spinal cord barrier (BSCB) permeability, spinal water content (edema), intrathecal pressure (ITP), and histological and functional outcome from 5 hours to 2 weeks post-SCI. Administration of an NK1 receptor antagonist was not effective in reducing BSCB permeability, edema, ITP, or functional deficits following SCI. We conclude that SP mediated neurogenic inflammation does not seem to play a major role in BSCB disruption, edema development and consequential tissue damage seen in acute traumatic SCI. Rather it is likely that the severe primary insult and subsequent hemorrhage may be the key contributing factors to ongoing SCI injury.

Spatial and temporal morphological changes in the subarachnoid space after graded spinal cord contusion in the rat

Spontaneous repair or treatment-induced recovery after spinal cord injury (SCI) is very limited and might be related to extramedullary alterations that have only briefly been documented. Here we report on the morphological changes of the spinal subarachnoid space (SAS) in a clinically relevant model of SCI. Anesthetized rats were subjected either to mild or severe spinal cord contusion at T9. Spine blocks from the site of injury and adjacent segments were harvested at acute (1 h and 1 day [d]), subacute (3 and 7 d), and chronic (1 and 3 months) stages post-injury. Histopathology and morphometry at each decalcified vertebral level were assessed. At acute and subacute stages, reduction of SAS lumen was observed after both mild and severe injuries. Acutely, after severe injuries, SAS occlusion was associated mainly with cord swelling and subarachnoid hematomas; a trend for dural sac constriction was observed for mild injuries. At 7 d, cord swelling diminished in both instances, but dural sac constriction increased for severe injuries. At early stages, in the epicenter and vicinity, histopathology revealed compression of neurovascular elements within the SAS, which was more intense in severe than in mild injuries. In the chronic stage, SAS lumen increased notably, mostly from cord atrophy, despite dural sac constriction. Myelograms complemented observations made on SAS lumen permeability. Post-traumatic arachnoiditis occurred mainly in animals with severe injury. In conclusion, early extramedullary SAS changes described here might be expected to produce alterations in cerebrospinal fluid (CSF) dynamics and cord blood perfusion, thereby contributing to the pathophysiology of SCI and becoming novel targets for treatment.

A prospective evaluation of hemodynamic management in acute spinal cord injury patients

STUDY DESIGN

Prospective observational study of acute spinal cord-injured (SCI) patients.

OBJECTIVES

To determine how effectively mean arterial blood pressure (MAP) and spinal cord perfusion pressure (SCPP) are maintained at target levels in acute SCI patients.

SETTING

Single-institution study at a Canadian level-one trauma center.

METHODS

Twenty-one individuals with cervical or thoracic SCI were enrolled within 48 h of injury. A lumbar intrathecal drain was inserted for monitoring intrathecal cerebrospinal fluid pressure (ITP). The MAP was monitored concurrently with ITP, and the SCPP was calculated. Data was recorded hourly from the time of first assessment until at least the end of the 5th day post injury.

RESULTS

All subjects had at least one recorded episode with a MAP below 80 mm Hg, and 81% had at least one episode with a MAP below 70 mm Hg. On average, subjects with cervical injuries had 18.4% of their pressure recordings below 80 mm Hg. Subjects with thoracic cord injuries had on average 35.9% of their MAP recordings <80 mm Hg.

CONCLUSION

It is common practice to establish MAP targets for optimizing cord perfusion in acute SCI. This study suggests that even in an acute SCI referral center, when prospectively scrutinized, the actual MAP may frequently fall below the intended targets. Such results raise awareness of the vigilance that must be kept in the hemodynamic management of these patients, and the potential discrepancy between routinely setting target MAP according to 'practice guidelines' and actually achieving them.

The effect of an NK1 receptor antagonist on blood spinal cord barrier permeability following balloon compression-induced spinal cord injury

The blood spinal cord barrier (BSCB) is disrupted following spinal cord injury (SCI) resulting in vasogenic edema and increased intrathecal pressure (ITP). The neuropeptide substance P (SP) has been implicated in the development of blood-brain barrier (BBB) disruption, edema, and increased intracranial pressure following brain injury, although it has not been investigated in SCI. The balloon compression model of experimental SCI has many advantages in that it replicates the "closed" environment observed clinically. Accordingly, this study characterized whether this model produces an increase in BSCB permeability and edema, and whether a SP, NK1 tachykinin receptor antagonist, N-acetyl-L-tryptophan (NAT) reduces such BSCB disruption and edema formation. At 30 min post-injury, animals were administered 2.5 mg/kg NAT or saline. Subgroups of animals were assessed for BSCB permeability (Evan's Blue) and spinal cord edema (wet weight/dry weight). BSCB permeability and edema were significantly increased in injured groups compared with sham (p < 0.001). There was no significant difference between vehicle and NAT treatment. We conclude that the balloon compression model of SCI produces significant BSCB disruption although NAT treatment did not attenuate BSCB permeability or edema. Further studies are required to fully elucidate the role of SP following SCI.

Anesthetic considerations in acute spinal cord trauma

Patients with actual or potential spinal cord injury (SCI) are frequently seen at adult trauma centers, and a large number of these patients require operative intervention. All polytrauma patients should be assumed to have an SCI until proven otherwise. Pre-hospital providers should take adequate measures to immobilize the spine for all trauma patients at the site of the accident. Stabilization of the spine facilitates the treatment of other major injuries both in and outside the hospital. The presiding goal of perioperative management is to prevent iatrogenic deterioration of existing injury and limit the development of secondary injury whilst providing overall organ support, which may be adversely affected by the injury. This review article explores the anesthetic implications of the patient with acute SCI. A comprehensive literature search of Medline, Embase, Cochrane database of systematic reviews, conference proceedings and internet sites for relevant literature was performed. Reference lists of relevant published articles were also examined. Searches were carried out in October 2010 and there were no restrictions by study design or country of origin. Publication date of included studies was limited to 1990–2010.

Rat model of spinal cord injury preserving dura mater integrity and allowing measurements of cerebrospinal fluid pressure and spinal cord blood flow

PURPOSES

Cerebrospinal fluid (CSF) pressure elevation may worsen spinal cord ischaemia after spinal cord injury (SCI). We developed a rat model to investigate relationships between CSF pressure and spinal cord blood flow (SCBF).

METHODS

Male Wistar rats had SCI induced at Th10 (n = 7) or a sham operation (n = 10). SCBF was measured using laser-Doppler and CSF pressure via a sacral catheter. Dural integrity was assessed using subdural methylene-blue injection (n = 5) and myelography (n = 5).

RESULTS

The SCI group had significantly lower SCBF (p < 0.0001) and higher CSF pressure (p < 0.0001) values compared to the sham-operated group. Sixty minutes after SCI or sham operation, CSF pressure was 8.6 ± 0.4 mmHg in the SCI group versus 5.5 ± 0.5 mmHg in the sham-operated group. No dural tears were found after SCI.

CONCLUSION

Our rat model allows SCBF and CSF pressure measurements after induced SCI. After SCI, CSF pressure significantly increases.

A novel porcine model of traumatic thoracic spinal cord injury

Spinal cord injury (SCI) researchers have predominately utilized rodents and mice for in vivo SCI modeling and experimentation. From these small animal models have come many insights into the biology of SCI, and a growing number of novel treatments that promote behavioral recovery. It has, however, been difficult to demonstrate the efficacy of such treatments in human clinical trials. A large animal SCI model that is an intermediary between rodent and human SCI may be a valuable translational research resource for pre-clinically evaluating novel therapies, prior to embarking upon lengthy and expensive clinical trials. Here, we describe the development of such a large animal model. A thoracic spinal cord injury at T10/11 was induced in Yucatan miniature pigs (20-25 kg) using a weight drop device. Varying degrees of injury severity were induced by altering the height of the weight drop (5, 10, 20, 30, 40, and 50 cm). Behavioral recovery over 12 weeks was measured using a newly developed Porcine Thoracic Injury Behavior Scale (PTIBS). This scale distinguished locomotor recovery among animals of different injury severities, with strong intra-observer and inter-observer reliability. Histological analysis of the spinal cords 12 weeks post-injury revealed that animals with the more biomechanically severe injuries had less spared white matter and gray matter and less neurofilament immunoreactivity. Additionally, the PTIBS scores correlated strongly with the extent of tissue sparing through the epicenter of injury. This large animal model of SCI may represent a useful intermediary in the testing of novel pharmacological treatments and cell transplantation strategies.

The pressure distribution of cerebrospinal fluid responds to residual compression and decompression in an animal model of acute spinal cord injury

STUDY DESIGN

In vivo large animal (pig) model study of cerebrospinal fluid (CSF) pressures after acute experimental spinal cord injury (SCI).

OBJECTIVE

To determine how the CSF pressure (CSFP) and CSF pulse pressure amplitude (CSFPPA) cranial and caudal to the injury site change after an acute SCI with subsequent thecal occlusion and decompression.

SUMMARY OF BACKGROUND DATA

Lowering intrathecal pressure via CSF drainage is currently instituted to prevent ischemia-induced SCI during thoracoabdominal aortic aneurysm surgery and was recently investigated as a potential intervention for acute traumatic SCI. However, in SCI patients, persistent extradural compression commonly occludes the subarachnoid space. This may generate a CSFP differential across the injury site, which cannot be appreciated with lumbar catheter pressure measurements.

METHODS

Anesthetized pigs were subjected to an acute contusive SCI at T11 and 8 hours of sustained compression (n = 12), or sham surgery (n = 2). CSFP was measured cranial and caudal to the injury site, using miniature pressure transducers, during compression and for 6 hours after decompression.

RESULTS

The cranial-caudal CSFP differential increased (mean, 0.39 mm Hg/h), predominantly due to increased cranial pressure. On decompression, cranial CSFP decreased (mean, -1.16 mm Hg) and caudal CSFP increased (mean, 0.65 mm Hg). The CSFP differential did not change significantly after decompression. Cranial CSFPPA was greater than caudal CSFPPA, but this differential did not change during compression. On decompression, the caudal CSFPPA increased in some but not all animals.

CONCLUSION

Although extradural compression exists at the site of injury, lumbar CSFP may not accurately indicate CSFP cranial to the injury. Decompression may provide immediate, though perhaps partial, resolution of the pressure differential. CSFPPA was not a consistent indicator of decompression in this animal model. These findings may have implications for the design of future clinical protocols in which CSFP is monitored after acute SCI.

Gross morphological changes of the spinal cord immediately after surgical decompression in a large animal model of traumatic spinal cord injury

STUDY DESIGN

Quantitative in vivo ultrasound imaging study of spinal cord and dura morphology after acute experimental spinal cord injury (SCI) and decompression in a pig model.

OBJECTIVE

To study the morphological changes of the spinal cord and dura immediately after surgical decompression for acute SCI.

SUMMARY OF BACKGROUND DATA

Surgical decompression for traumatic SCI is currently a topic of debate. After decompression, relief of bony impingement on the thecal sac and spinal cord can be confirmed intraoperatively. However, postoperative imaging often reveals that the cord has swollen to fill the subarachnoid space. Little is known about the extent and timing of this morphological response.

METHODS

Yucatan miniature pigs received sham surgery (N = 1) or a moderate (N = 6, 20 g, 2.3 m/s) or high (N = 6, 20 g, 4.7 m/s) severity weight-drop SCI followed by 8 hours of sustained compression (100 g) and 6 hours of postdecompression monitoring. Sagittal-plane ultrasound images were used to quantify spinal cord, dura, and subarachnoid space dimensions preinjury and once per hour after decompression.

RESULTS

Animals with a moderate SCI exhibited a residual cord deformation of up to 0.64 mm within 10 minutes of decompression, which tended to resolve during 6 hours because of tissue relaxation and swelling. For animals with high-severity SCIs, cord swelling was immediate and resulted in occlusion of the subarachnoid space within 10 minutes to 5 hours, whereas this occurred for only half of the moderate injury group.

CONCLUSION

Decompression of an acute SCI may result in residual cord deformation followed by gradual swelling or immediate swelling leading to subarachnoid occlusion. The response is dependent on initial injury severity. These observations may partly explain the lack of benefit of decompression in some patients and suggest a need to reduce cord swelling to optimize the clinical outcome after acute SCI.

Spinal cord injury and its treatment: current management and experimental perspectives

Clinical management of spinal cord injury (SCI) has significantly improved its general prognosis. However, to date, traumatic paraplegia and tetraplegia remain incurable, despite massive research efforts. Current management focuses on surgical stabilisation of the spine, intensive neurological rehabilitation, and the prevention and treatment of acute and chronic complications. Prevention remains the most efficient strategy and should be the main focus of public health efforts. Nevertheless, major advances in the understanding of the pathophysiological mechanisms of SCI open promising new therapeutic perspectives. Even if complete recovery remains elusive due to the complexity of spinal cord repair, a strategy combining different approaches may result in some degree of neurological improvement after SCI. Even slight neurological recovery can have high impact on the daily functioning of severely handicapped patients and, thus, result in significant improvements in quality of life.The main investigated strategies are: [1] initial neuroprotection, in order to decrease secondary injury to the spinal cord parenchyma after the initial insult; [2] spinal cord repair, in order to bridge the lesion site and reestablish the connection between the supraspinal centres and the deafferented cord segment below the lesion; and [3] re-training and enhancing plasticity of the central nervous system circuitry that was preserved or rebuilt after the injury.Now and in the future, treatment strategies that have both a convincing rationale and seen their efficacy confirmed reproducibly in the experimental setting must carefully be brought from bench to bedside. In order to obtain clinically significant results, their introduction into clinical research must be guided by scientific rigour, and their coordination must be rationally structured in a long-term perspective.

Vascular disruption and the role of angiogenic proteins after spinal cord injury

Spinal cord injuries (SCI) can result in devastating paralysis, for which there is currently no robustly efficacious neuroprotective/neuroregenerative treatment. When the spinal cord is subjected to a traumatic injury, the local vasculature is disrupted and the blood–spinal cord barrier is compromised. Subsequent inflammation and ischemia may then contribute to further secondary damage, exacerbating neurological deficits. Therefore, understanding the vascular response to SCI and the molecular elements that regulate angiogenesis has considerable relevance from a therapeutic standpoint. In this paper, we review the nature of vascular damage after traumatic SCI and what is known about the role that angiogenic proteins—angiopoietin 1 (Ang1), angiopoietin 2 (Ang2) and angiogenin—may play in the subsequent response. To this, we add recent work that we have conducted in measuring these proteins in the cerebrospinal fluid (CSF) and serum after acute SCI in human patients. Intrathecal catheters were installed in 15 acute SCI patients within 48 h of injury. CSF and serum samples were collected over the following 3–5 days and analysed for Ang1, Ang2 and angiogenin protein levels using a standard ELISA technique. This represents the first description of the endogenous expression of these proteins in an acute human SCI setting.

Intracanal pressure in compressive spinal cord injury: reduction with hypothermia

Most cases of human spinal cord injury (SCI) are accompanied by continuing cord compression. Experimentally, compression results in rapid neurological decline over hours, suggesting a rise in intracanal pressure local to the site of injury. The aim of this study was to measure the rise in local intracanal pressure accompanying progressive canal occlusion and to determine the relationship between raised intracanal pressure and neurological outcome. We also aimed to establish whether hypothermia was able to reduce raised intracanal pressure. We demonstrate that, following SCI in F344 rats, local intracanal pressure remains near normal until canal occlusion exceeds 30% of diameter, whereupon a rapid increase in pressure occurs. Intracanal pressure appears to be an important determinant of neurological recovery, with poor long-term behavioural and histological outcomes in animals subject to 8 h of 45% canal occlusion, in which intracanal pressure is significantly elevated. In contrast, good neurological recovery occurs in animals with near normal intracanal pressure (animals undergoing 8 h of 30% canal occlusion or those undergoing immediate decompression). We further demonstrate that hypothermia is an effective therapy to control raised intracanal pressure, rapidly reducing elevated intracanal pressure accompanying critical (45%) canal occlusion to near normal. Overall these data indicate that following SCI only limited canal narrowing is tolerated before local intracanal pressure rapidly rises, inducing a sharp decline in neurological outcome. Raised intracanal pressure can be controlled with hypothermia, which may be a useful therapy to emergently decompress the spinal cord prior to surgical decompression.

Role of early surgical decompression of the intradural space after cervical spinal cord injury in an animal model

BACKGROUND

The role of decompressing the intradural space through a durotomy as a treatment option for acute traumatic cervical spinal cord injury has not been explored in an animal model, to our knowledge. We sought to determine the role of durotomy and duraplasty in the treatment of acute cervical spinal cord injury and its effects on inflammation, scar formation, and functional recovery.

METHODS

Seventy-two adult female Sprague-Dawley rats were assigned to three groups: contusion injury alone, contusion injury with a decompressive durotomy, and contusion injury with a decompressive durotomy followed by placement of a dural allograft. A mild (200-kdyn [2-N]) contusive injury was delivered to the exposed spinal cord at C5. The injured segment was reexposed four hours after injury, and a durotomy with decompression was performed. When a dural allograft was used it was affixed to the surrounding intact dura with use of a fibrin sealant. The Grip Strength Meter was used to assess forelimb function. Animals were killed at two and four weeks, and immunohistochemical analysis was performed to assess scar formation, inflammatory cell infiltration, and lesional volume.

RESULTS

Immunohistochemical analysis revealed increased scar formation, cavitation, and inflammatory response in the animals treated only with a decompressive durotomy. Relative to the group with a contusion injury alone, the animals treated with a durotomy followed by a dural allograft had decreased cavitation and scar formation. Lesional volume measurements showed a significantly increased cavitation size at four weeks in both the contusion-only (mean and standard deviation, 12.6 +/- 0.5 mm(3)) and durotomy-only (15.1 +/- 1 mm(3)) groups relative to the animals that had received a dural allograft following durotomy (6.8 +/- 1.4 mm(3)).

CONCLUSIONS

Functional recovery after acute cervical spinal cord injury was better in animals treated with decompression of the intradural space and placement of a dural allograft than it was in animals treated with decompression alone. These functional data correlated directly with histological evidence of a decrease in spinal cord cavitation, inflammation, and scar formation.