Myogenic transcranial motor evoked potentials monitoring cannot always predict neurologic outcome after spinal cord ischemia in rats

OBJECTIVES

A day after undergoing an operation of the thoracic aorta, a patient showed signs of spastic paraplegia, but on myogenic transcranial motor evoked potential monitoring, the myogenic transcranial motor evoked potentials recorded from the left anterior tibial muscle appeared normal. We sought to confirm these observations by using a rat spinal ischemia model to define the possibility of false-negative results in myogenic transcranial motor evoked potential monitoring by motor function behavior and spinal histopathology.

METHODS

Spinal ischemia was induced for 6 minutes (group A, n = 6) or 10 minutes (group B, n = 6) with an intra-aortic balloon. After ischemia, motor function was assessed periodically by using the motor deficit index (0, complete recovery; 6, complete paraplegia). Myogenic transcranial motor evoked potentials were recorded from the right soleus muscle before ischemia, 2 and 6 minutes after the start of spinal ischemia, and at 30 minutes, 24 hours, and 72 hours of reperfusion.

RESULTS

All group A rats showed normal motor function at 72 hours of reperfusion, whereas all group B rats displayed complete spastic paraplegia (motor deficit index = 6) at 72 hours of reperfusion. However, transcranial motor evoked potential was preserved in both group B and group A. Histopathologic analysis in group B revealed the presence of extensive necrotic changes of the gray matter distributed between laminae V through VII in the L3 to L5 segments but normal appearance of alpha motor neurons.

CONCLUSION

According to our data, in using myogenic transcranial motor evoked potential monitoring during thoracic or thoracoabdominal aneurysm repair, we should be aware that transcranial motor evoked potentials cannot always be used to predict neurologic outcome after the operation.

Immunophilin ligands FK506 and cyclosporine A improve neurologic and histopathologic outcome after transient spinal cord ischemia in rabbits

BACKGROUND

We comparatively evaluated the protective effect of the immunophilin ligands cyclosporine A (INN: ciclosporin), FK506, and rapamycin on the spinal cord in a rabbit model of transient ischemia. Both cyclosporine A and FK506 inhibit calcineurin, whereas rapamycin does not.

METHODS

Thirty-six male New Zealand White rabbits were divided into the following 6 groups: group C, 15 minutes of spinal cord ischemia; group FK, FK506 (1 mg/kg) administered 30 minutes before ischemia; group CsA, cyclosporine A (30 mg/kg) administered 30 minutes before ischemia; group CsA-C, chronic administration of cyclosporine A (20 mg/kg) for 9 days before ischemia; group R, rapamycin (1 mg/kg) administered 30 minutes before ischemia; and group R+FK, rapamycin (1 mg/kg) administered 20 minutes before FK506 pretreatment (1 mg/kg). Group CsA-C was added because the drug does not readily cross the blood-brain barrier. Neurologic function was evaluated by Johnson's 5-point scale at 8, 24, and 48 hours after ischemia, and histopathology was assessed 48 hours after ischemia.

RESULTS

At 24 and 48 hours after ischemia, the Johnson score was better in groups FK (4.0 +/- 1.1), R+FK (3 +/- 1.1), and CsA-C (2.7 +/- 1.2) than in group C (0.8 +/- 1.2). Numbers of morphologically intact anterior horn cells were higher in groups FK (31.3 +/- 9.9), R+FK (23.2 +/- 4.5), and CsA-C (18.3 +/- 6.8) than in group C (6.3 +/- 4.3).

CONCLUSIONS

FK506 and chronic administration of cyclosporine A, but not rapamycin, protect the spinal cord from transient ischemia. Although these results are compatible with inhibition of calcineurin in the mechanism of neuroprotective action of these drugs, other effects through different pathways cannot be excluded before further study.

Spinal cord infarction due to a self-inflicted needle stick injury

STUDY DESIGN

Case report.

OBJECTIVE

To report a case of spinal cord infarction after a self-inflicted needle stick injury, following an injection of heroin into the cord.

SETTING

National spinal injury unit in a Scottish University teaching hospital, Glasgow, UK.

CASE REPORT

A 20-year-old male, injected street heroin accidentally into the cord through the left side of the neck, leading to sudden loss of power to all four limbs. Initial magnetic resonance imaging scans showed extensive cord oedema and follow-up scans showed signal changes within the anterior horns of the spinal cord in keeping with a cord infarct.

CONCLUSION

Self-inflicted spinal cord injury with a small needle is difficult, but not impossible. Cord infarct as a result of a self-inflicted injury has not been previously reported. The mechanism of the injury resulting in cord infarction is explained by the vascular anatomy of the spinal cord circulation, and this may also explain the residual neurological status of the patient.

Is intrathecal magnesium sulfate safe and protective against ischemic spinal cord injury in rabbits?

We performed three sets of experiments to investigate the safety of intrathecal magnesium and to determine its optimal dose for protection, if any, against ischemic spinal cord injury in rabbits. First, we examined neurotoxicity of 0.3, 1, 2, or 3 mg/kg of magnesium sulfate (n = 6 each). Significant sensory dysfunction was observed in the 3-mg/kg group 7 days after administration. Motor dysfunction was found in two rabbits in both the 2- and 3-mg/kg groups. The area of destruction in laminae V-VII was observed in one, two, and one rabbit in the 1-, 2-, and 3-mg/kg groups, respectively. Second, we investigated the temporal profile (6 h, 48 h, and 96 h [n = 3 each]) of histopathologic changes after 3 mg/kg of magnesium sulfate and confirmed similar changes in the rabbits with motor dysfunction at 48 and 96 h. Third, we evaluated the effects of 0.3 mg/kg or 1 mg/kg of magnesium sulfate or saline (n = 6 each) administered before ischemia on hindlimb motor function and histopathology after spinal cord ischemia (15 min). Magnesium did not improve neurologic or histopathologic outcome 96 h after reperfusion. The results indicate that intrathecal magnesium has a risk of neurotoxicity and shows no evidence of protective effects against ischemic spinal cord injury.

The evolution of ischemic spinal cord injury in function, cytoarchitecture, and inflammation and the effects of adenosine A2A receptor activation

OBJECTIVE

Spinal cord ischemia/reperfusion injury involves multiple factors that may be modulated by adenosine A 2A receptor activation. This study defines injury progression in terms of function, cytoarchitecture, and inflammation and assesses whether adenosine A 2A receptor activation by ATL-146e limits injury progression.

METHODS

Mature swine were divided into 3 groups: sham thoracotomy, IR (30 minutes of ischemia followed by reperfusion), and ATL (ischemia/reperfusion with ATL-146e administration for the first 3 hours of reperfusion). Subgroups were killed at 0, 3, 6, 12, 24, and 48 hours after reperfusion. Function was followed up with Tarlov scores. Spinal cord tissue was evaluated for neuronal viability, microtubule-associated protein-2 immunohistochemistry, and neutrophil sequestration (myeloperoxidase assay). Spinal cord tissue, cerebrospinal fluid, and serum were evaluated for tumor necrosis factor-alpha by enzyme-linked immunosorbent assay.

RESULTS

Function was significantly impaired at 24, 36, and 48 hours in the IR group compared with the sham and ATL groups ( P < .05). Neuronal viability and microtubule-associated protein-2 staining were significantly preserved in the sham and ATL groups compared with the IR group at 24 and 48 hours ( P < .05). Spinal cord myeloperoxidase levels were significantly higher in the IR group than in the sham and ATL groups at 24 and 48 hours. Although negligible in serum and cerebrospinal fluid, tumor necrosis factor-alpha levels in the spinal cord peaked significantly higher in the IR group compared with the sham and ATL groups at 6 and 24 hours ( P < .05).

CONCLUSIONS

Spinal cord ischemia/reperfusion induced changes in neutrophil sequestration, microtubule-associated protein-2 expression, and neuronal viability within 24 hours of reperfusion. Spinal cord tumor necrosis factor-alpha increased significantly by 6 to 12 hours after reperfusion. Adenosine A 2A receptor activation attenuates spinal cord inflammation, which may be critical for the preservation of neuronal function and cytoarchitecture after ischemia/reperfusion.

Expression and changes of calbindin D-28k immunoreactivity in the ventral horn after transient spinal cord ischemia in rabbits

We examined ischemia-related changes of calbindin D-28k (CB) immunoreactivity in L(7) of the spinal ventral horn after transient spinal cord ischemia in rabbits. In the sham-operated group, CB immunoreactivity was not present in the spinal ventral horn, but CB immunoreactivity was detectable in the dorsal horn. CB immunoreactivity was detectable in the ventral horn at 30 min after ischemia: the CB immunoreactivity was found in glial cells identified as astrocytes. At 1 h after ischemia, CB immunoreactivity was highest and present at a few somata located in the lamina VII as well as many glial cells. CB immunoreactivity was lower in the lamina VII at 3 h after ischemia compared to 1 h post-ischemic group. By 2 days after ischemia, CB immunoreactivity was decreased in this region. In addition, the result of Western blot result showed the pattern of CB expression similar to that of immunohistochemistry. In conclusion, the ischemia-related changes of CB immunoreactivity in neurons and glial cells in the ischemic spinal ventral horn in rabbits may be related to modulation of intracellular calcium following transient ischemia.

The effects of the delta-opioid agonist SNC80 on hind-limb motor function and neuronal injury after spinal cord ischemia in rats

Recent investigation suggested neuroprotective efficacy of a delta-opioid agonist in the brain. We investigated the effects of intrathecal treatment with a delta-opioid agonist (SNC80) on spinal cord ischemia (SCI) in rats. SCI was induced with an intraaortic balloon catheter. The animals were randomly allocated to one of the following five groups: 1) SNC80 before 9 min of SCI (SNC-9; n = 12), 2) vehicle before 9 min of SCI (V-9; n = 12), 3) SNC80 before 11 min of SCI (SNC-11; n = 10), 4) vehicle before 11 min of SCI (V-11; n = 12), or 5) sham (n = 12). SNC80 (400 nmol) or vehicle was administered 15 min before SCI. Forty-eight hours after reperfusion, hind-limb motor function was assessed by using the Basso, Beattie, Bresnahan (BBB) scale (0 = paraplegia; 21 = normal) and histological assessment of the L4 and L5 spinal segments was performed. BBB scores in the SNC-9 group were higher compared with those in the V-9 group (P < 0.05), whereas there were no differences in BBB scores between the SNC-11 and V-11 groups. There were significantly more normal neurons in the SNC-9 and SNC-11 groups than in the V-9 and V-11 groups (P < 0.05). The results indicate that intrathecal treatment with the delta-opioid agonist SNC80 can attenuate hind-limb motor dysfunction and neuronal injury after SCI in rats.

Spinal cord infarction secondary to intervertebral foraminal disease

STUDY DESIGN

The 5 year review of patients referred to one center.

OBJECTIVE

To report spinal cord infarction secondary to vascular occlusion from disease in a lower thoracic intervertebral foramen.

METHOD

The clinical and imaging findings of two cases with acute spinal cord dysfunction are presented.

SETTING

Midlands Centre for Spinal Injuries, England.

RESULTS

The CT and MR imaging features revealed lower thoracic unilateral foraminal occlusion due to acute facet joint septic arthritis in a diabetic patient, and secondary to chronic hypertrophic osteophytes in a second hypertensive individual. The presumed mechanism of infarction was occlusion of the artery of Adamkiewicz.

CONCLUSION

Foraminal disease in the lower thoracic levels needs to be entertained in cases of unexplained nontraumatic acute spinal cord dysfunction.

Diffusion-weighted MRI of spinal cord infarction

Infarction is a rare cause of spinal cord dysfunction. Whereas diffusion-weighted (DW) MRI has been established as a highly sensitive technique for assessing acute cerebral ischemia, its role in spinal cord infarction remains to be determined. The purpose of this study is to present the signal characteristics of acute spinal cord ischemia using DWMRI within the first two days and after one week. MRI including DW imaging (DWI) was performed in three patients with acute spinal cord dysfunction 8, 12 and 30 hours after the onset of symptoms and repeated after one week in two patients. Two initial scans included EPI DW sequences in transverse and sagittal orientation. The remaining examinations were performed with an optimised high-spatial resolution DWI sequence in the transverse plane. The diagnosis of spinal cord ischemia was established by imaging, clinical history and CSF analysis. T2 signal abnormality and restricted diffusion was demonstrated in all initial examinations. Transverse DW sequences had the highest sensitivity. The spinal infarctions were mainly located in the centre of the spinal cord and the grey matter. Contrast enhancement was absent. After one week, the restricted diffusion had normalised (pseudo normalisation) whereas the T2 signal changes had become more prominent. Restricted diffusion in the course of spinal cord ischemic infarction can be demonstrated using DW-MRI. Whereas a diffusion abnormality can be found after few hours, it does not last for longer than one week. At this time, the establishment of the diagnosis has to rely mainly on T2-weighted images with additional post contrast T1-weighted images being useful.

Effect of puerarin on neural function and histopathological damages after transient spinal cord ischemia in rabbits

OBJECTIVE

To investigate the effect of puerarin on the neural function and the histopathological changes after ischemic spinal cord injury in rabbits.

METHODS

Thirty male New Zealand white rabbits were randomly divided into three groups as follows: puerarin group (n=10) receiving intravenous infusion of 30 mg/kg puerarin for 10 minutes, control group (n=10) receiving intravenous infusion of the same volume of normal saline as puerarin for 10 minutes, and sham operation group (n=10) undergoing only the surgical exposure of the abdominal aorta. Temporary spinal cord ischemia was induced by infrarenal aortic occlusion for 20 minutes and followed by reperfusion. The neural status was scored with the Tarlov criteria at 8, 12, 24 and 48 hours after reperfusion. All the animals were killed at 48 hours after reperfusion and the spinal cords (L5) were removed immediately for histopathological study.

RESULTS

The neural function scores at 8, 12, 24 and 48 hours after reperfusion were higher in the puerarin group and sham operation group than those in the control group (P<0.05). More normal motor neurons in the anterior horn of spinal cord were present in the puerarin group and sham operation group than those in the control group (P<0.01). There was a strong correlation between the final neural function scores and the number of normal motor neurons in the anterior horn of spinal cord (r=0.839, P<0.01).

CONCLUSIONS

Puerarin can significantly ameliorate the neural function and the histopathological damages after transient spinal cord ischemia in rabbits.

Experimental spinal cord ischemia: Model characterization and improved outcome with arterial hypertension*

OBJECTIVE

Paraplegia from spinal cord ischemia is a devastating complication of thoracoabdominal aortic aneurysm repair. Perioperative hypoperfusion of the spinal cord is a critical determinant of residual neurologic deficits. We determined if functional and histologic outcome is dependent on systemic blood pressure in a rat model of spinal cord ischemia.

DESIGN

Randomized, controlled, prospective study.

SETTING

Research laboratory at a university teaching hospital.

SUBJECTS

Adult male Wistar rats.

INTERVENTIONS

Endotracheally intubated adult male Wistar rats (300-450 g) anesthetized with halothane underwent a thoracotomy and placement of a clip across the descending aorta for 27 mins. Mean proximal arterial blood pressure (MPABP) was monitored with a cannula placed in the left common carotid artery. Halothane was adjusted (1.25-1.5%) to maintain MPABP between 70 and 90 mm Hg (n = 20) or 140 and 150 mm Hg (n = 20). Shamoperated rats (n = 10) had a thoracotomy without aortic clamping at an MPABP of 70-90 mm Hg. Following 1, 24, 48, and 72 hrs of recovery from anesthesia, motor function of the hind paws was scored as follows: 0, no evidence of deficit; 1, toes flat under body when walking but with ataxia; 2, knuckle walks; 3, movements in hind limbs but unable to knuckle walk; 4, no movement, drags hind limbs. Body temperature was maintained between 37 and 38 degrees C throughout the experiment.

MEASUREMENTS AND MAIN RESULTS

All sham operated rats with MPABP 70-90 mm Hg recovered without neurologic deficits, whereas those that underwent aortic occlusion with MPABP between 70 and 90 mm Hg emerged from anesthesia with grade 3 and 4 deficits and remained in this condition without improvement at 72 hrs. Histopathology at 72 hrs demonstrated moderate to severe neuronal loss with involvement of dorsal, intermediate, and ventral horns. Only eight of 20 rats that underwent aortic occlusion with MPABP between 140 and 150 mm Hg had grade 1 and 2 deficits on emergence but had no neurologic deficit after 1 hr. Most of the surviving neurons in these animals appeared normal histologically, particularly motor neurons around the periphery of the ventral horn.

CONCLUSIONS

Systemic blood pressure is a critical determinant of outcome following spinal cord ischemia, and controlled peri-operative blood pressure augmentation may ameliorate neurologic deficits in patients who undergo thoracoabdominal vascular procedures and are at risk for spinal cord hypoperfusion.

Spontaneous cervical epidural haematoma during pregnancy

Spontaneous cervical epidural haematoma is very rare during pregnancy. We describe a woman who presented with tetraplegia at 41 weeks of pregnancy. She had no previous history of any relevant medical disorder. Her upper level of anaesthesia was at the second thoracic segment. The condition was diagnosed by magnetic resonance imaging, and both caesarean section and decompression were conducted 12 hours after the event. The neurological deficit showed little recovery. Histology was non-specific and follow-up magnetic resonance imaging showed spinal cord ischaemia. The prognosis in this condition depends on the interval of time between onset and decompression.

The effects of tyrphostine Ag 556 on experimental spinal cord ischemia reperfusion injury

BACKGROUND

To investigate the effects of Tyrphostin Ag 556 on spinal cord ischemia reperfusion injury.

METHODS

The inhibition of tyrosine kinase may represent a novel approach in the treatment of spinal cord ischemia reperfusion injury. Recently, a family of tyrosine kinase inhibitors, the tyrphostins, has been successfully used in models of endotoxemia, peritonitis, and hypovolemic shock.

MATERIALS AND METHODS

Twenty-four Wistar rats were used in the study. Rats were divided into 4 groups of 6 animals. The groups were named as sham operated group, injury group, vehicle group, and treatment group. Clamping of the abdominal aorta was performed for 45 minutes with all of the groups except sham-operated group. All of the rats were sacrificed 24 hours after the operation for biochemical and ultrastructural studies.

RESULTS

Tyrphostin Ag 556 treatment was found effective on experimental spinal cord ischemia reperfusion injury. The Malondialdehyde (MDA) values of the treatment group were statistically significant lower then the other reperfusion injury groups. The histologic examination showed better cellular structure in the treatment group than the other reperfusion injury groups. The neurologic scores of the treatment group also improved after treatment.

CONCLUSIONS

Tyrphostin Ag 556 alters spinal cord ischemia reperfusion injury by inhibiting protein kinases. Further investigations will be required to determine the long-term effects of this drug.

Characterization of spinal HSP72 induction and development of ischemic tolerance after spinal ischemia in rats

Induction of heat shock protein (HSP72) has been implicated in the development of ischemic tolerance in several tissue organs including brain and spinal cord. In the present study, using an aortic balloon occlusion model in rats, we characterized the effect of transient noninjurious (3 or 6 min) or injurious intervals (10 min) of spinal ischemia followed by 4-72 h of reflow on spinal expression of HSP72 and GFAP protein. In a separate group of animals, the effect of ischemic preconditioning (3 or 6 min) on the recovery of function after injurious interval of spinal ischemia (10 min) was studied. After 3 min of ischemia, there was a modest increase in HSP72 protein immunoreactivity in the dorsal horn neurons at 12 h after reperfusion. After 6 min of ischemia, a more robust and wide spread HSP72 protein expression in both dorsal and ventral horn neurons was detected. The peak of the expression was seen at 24 h after ischemia. At the same time point, a significant increase in spinal tissue GFAP expression was measured with Western blots and corresponded morphologically with the presence of activated astrocytes in spinal segments that had been treated similarly. After 10 min of ischemia and 24 h of reflow, a significant increase in spinal neuronal HSP72 expression in perinecrotic regions was seen. Behaviorally, 3 min preconditioning ischemia led to the development of a biphasic ischemic tolerance (the first at 30 min and the second at 24 h after preconditioning) and was expressed as a significantly better recovery of motor function after exposure to a second 10-min interval of spinal ischemia. After 6 min ischemic preconditioning, a more robust ischemic tolerance at 24 h after preconditioning then seen after 3-min preconditioning was detected. These data indicate that 3 min of spinal ischemia represents a threshold for spinal neuronal HSP72 induction, however, a longer sublethal interval (6 min) of preconditioning ischemia is required for a potent neuronal HSP72 induction. More robust neurological protection, seen after 6 min of preconditioning ischemia, also indicates that HSP72 expression in spinal interneurons seen at 24 h after preconditioning may represent an important variable in modulating ischemic tolerance observed during this time frame.

[Ischemic-reperfusion paraplegia in the dog and its light microscopy imaging]

Paraplegia, which develops after operation on aorta, represents a real catastrophe for the patient and for the surgeon. The aim of the present work was to investigate the light microscopy picture of this complication and consequently better understand related processes. Twenty one adult dogs, cross breeds of both sexes, weight 18-25 kg, were divided into four groups: 1. Controls (n = 3); 2.30-min ischemia induced by occlusion of thoracic aorta by a tourniquet, followed for 30 min survival (n = 6); 3.30-min ischemia and 72 h of survival (n = 6); 4) 30-min ischemia and 6 days of survival (n = 6). All these manipulations were made in sterile conditions under general anesthesia. As soon as the planned time of survival passed, the animals were flushed out, in deep pentobarbital anesthesia, with 3,000 ml of sodium chloride and fixed with 3,000 ml of 10% neutral formaldehyde. Sections, 30 microns thick, from L3-S1 medulla segments were processed in the laboratory of Neurobiological Institute by the method of Nauta for light microscopy examination. Neurohistological picture was characterized by a marked damage of the medulla neurons. The changes proved to be irreversible and resulted, in the course of six days of survival, to death of the cells, characterized by their disintegration. The results indicate that the only rational procedure in conditions of threatening ischemic-reperfusion injury of medulla is to prevent it.

Effect of Mg2SO4 Usage on Spinal Cord Ischemia-Reperfusion Injury: Electron Microscopic and Functional Evaluation

OBJECTIVES

To evaluate the effects of intravenous magnesium sulfate (Mg(2)SO(4)) administration on ischemia-reperfusion injury of the spinal cord.

MATERIAL AND METHODS

Sixteen rabbits were randomly assigned to the control (group I, 8 rabbits) and the study group (group II, 8 rabbits). The abdominal aorta was clamped for a period of 30 min followed by a reperfusion period of 60 min. The animals in group II received 0.25 ml/kg/h Mg(2)SO(4) intravenous infusion (15% Mg(2)SO(4)) throughout this procedure. The animals were then observed for 24 h after which their neurological states were evaluated and tissue samples obtained from the spinal cord were examined with electron microscopy.

RESULTS

Aortic pressure distal to the cross-clamp during the occlusion period was 9 +/- 3 mm Hg in group I and 19 +/- 6 mm Hg in group II. All animals in group I were paraplegic at the end of the study. In group II the neurological outcome of 1 animal was poor while the other 7 animals were neurologically in a good condition. Electron microscopic examinations of the spinal cord tissues of group I revealed severe injury but the ultrastructure was well preserved in group II.

CONCLUSIONS

Intravenous Mg(2)SO(4) administration may have protective effects on the ischemia-reperfusion injury of the spinal cord. We propose that Mg(2)SO(4) may be an additional protective pharmacological agent in thoracal and thoracoabdominal aortic surgery.

Protective effect of D-003 on experimental spinal cord ischemia in rabbits

D-003 is a natural mixture of long chain aliphatic acids isolated and purified from sugar cane wax. It possesses antiplatelet and antithrombotic effects as well as decreases plasma and serum levels of thromboxane B(2) (TxB(2)), meanwhile significantly and markedly raises prostacyclin (PgI(2)) levels in rats. This study was undertaken to investigate the effects of D-003 on spinal cord injury in rabbits. New Zealand rabbits were treated during 10 days with D-003 (25 and 200 mg kg(-1)) and ASA (2 mg kg(-1)) before spinal cord ischemia. Animals were subjected to 20 min of aortic occlusion and 24h of reperfusion. Clinical symptoms and histopathological changes of spinal cord were observed. The PgI(2) levels in thoracic aorta were quantified by bioassay. D-003 (25 and 200 mg kg(-1)) significantly increased the mean scores reached 4h after reperfusion, although no dose relation was observed. Twenty-four hours after reperfusion, no deaths occurred in both sham and D-003 treated groups, meanwhile in positive controls and ASA the mortality rate was 38.5% and 7.69% respectively. In addition, 100% of sham, 69% and 77% of rabbits treated with D-003 at 25 and 200 mg kg(-1), respectively, did not show histopathological changes. By the contrary, 100% of positive control animals showed severe damage and ASA-treated rabbits showed only a partial protection. Animals treated with both doses of D-003 showed PgI(2) levels significantly larger than those of positive and negative controls, an effect dose-related, while ASA 2 mg kg(-1) did not change PgI(2) values. The increase of PgI(2) levels achieved in the D-003 treated animals could be an important mechanism in the protection against the spinal cord ischemia.

Neuroprotective effects of FK-506, l-carnitine and azathioprine on spinal cord ischemia-reperfusion injury

OBJECTIVE

In our experimental study, we aimed to test the effect of FK506, azathioprine and L-carnitine on protection of spinal cord injury due to ischemia-reperfusion.

METHODS

Twenty-seven Sprague-Dawley male rats were randomly divided into five groups. They were subjected to spinal cord ischemia by clamping the abdominal aorta for 45 min. Thirty minutes before the aortic clamping, group I received 0.5 mg/kg FK506, group II received 100 mg/kg L-carnitine, group III received 4 mg/kg azathioprine, the fourth group was the control group and received only normal saline injection intravenously and the last group was the sham group. Neurological status was scored by using the Tarlov scoring system. Sections of the lumbar cord were harvested for histopathological grades (1-4), having regard to percentage of the apoptotic cells.

RESULTS

Hind-limb motor function had recovered normally 48 h after the operation in all rats which received FK506, azathioprine and L-carnitine prophylactically. In contrast, all rats in the control group had deteriorated to paraplegia by 48 h after the operation (P<0.05). Histopathologic sections in the involved spinal cord segment showed that a greater number of motor neuron cells were preserved and there were less apoptotic cells in the rats that received FK506, azathioprine and L-carnitine than those in control group.

CONCLUSIONS

These results suggest that prophylactic use of FK506, azathioprine and L-carnitine protects motor neuron cells from ischemic spinal cord injury.

Transcranial myogenic motor-evoked potentials after transient spinal cord ischemia predicts neurologic outcome in rabbits

OBJECTIVE

Myogenic transcranial motor-evoked potentials (tc-MEPs) were applied to monitor spinal cord ischemia in the repairs of thoracoabdominal aortic aneurysms. We investigated whether tc-MEPs after spinal cord ischemia/reperfusion could be used to predict neurologic outcome in leporine model.

METHODS

Tc-MEPs were measured at 30-second intervals before, during, and after spinal cord ischemia (SCI) induced by balloon occlusion of the infrarenal aorta. Twenty rabbits were divided into five groups. Four groups (n = 4 animals in each group) had transient ischemia induced for 10, 15, 20, or 30 minutes. In fifth group, the terminal aorta at the aortic bifurcation was occluded for 30 minutes. All animals were evaluated neurologically 48 hours later, and their spinal cords were removed for histologic examination.

RESULTS

The tc-MEPs in each SCI group rapidly disappeared after SCI. After reperfusion, the recovery of tc-MEPs amplitude was inversely correlated to duration of SCI. Tc-MEPs amplitude at one hour after reperfusion was correlated with both neurologic score and number of neuron cells in the spinal cord 48 hours later. Logistic regression analysis demonstrated that the neurologic deficits differed significantly between animals with tc-MEPs amplitude of less than 75% of the baseline and those with an amplitude of more than 75%.

CONCLUSIONS

The amplitude of tc-MEPs after ischemia /reperfusion of the spinal cord showed a high correlation with durations of SCI, with neurologic deficits, and with pathologic findings of the spinal cord. Tc-MEPs, therefore, could be used to predict neurologic outcome. In particular, tc-MEPs whose amplitude recovered by less than 75% indicated a risk of paraplegia.

Injury severity and cell death mechanisms: effects of concomitant hypovolemic hypotension on spinal cord ischemia–reperfusion in rats

A number of previous studies indicated that ischemia-reperfusion injury causes two distinct types of cell death--necrosis and apoptosis--in the central nervous system. It was also implicated that the intensity of injury can somehow affect the cell death mechanisms. By occluding the descending thoracic aorta with or without simultaneously induced hypovolemic hypotension in rats, we established a model of experimental spinal cord ischemia-reperfusion (I/R) in which the injury severity can be controlled. Recordings of carotid blood pressure (CBP) and spinal cord blood flow (SCBF) showed that aortic occlusion induced dramatic CBP elevation but SCBF drop in both the normotensive (NT) and hypotensive (HT) groups of rats. However, the HT group demonstrated significantly lower SCBF during aortic occlusion, and much slower elevation of SCBF after reperfusion, and extremely poor neurological performance. Spinal cord lesions were characterized by infarction associated with extensive necrotic cell death, but little apoptosis and caspase-3 activity. In contrast, in the NT group, I/R injury resulted in minor tissue destruction associated with persistent abundant apoptosis, augmented caspase-3 activity, and favorable functional outcome. The relative sparing of motoneurons in the ventral horns from apoptosis might have accounted for the minor functional impairment in the NT group. The severity of I/R injury was found to have substantial impact on the histopathological changes and cell death mechanisms, which correlate with neurological performance. Our results implicate that injury severity and duration after injury are two critical factors to be considered in therapeutic intervention.

Ischemic insult exacerbates acrolein-induced conduction loss and axonal membrane disruption in guinea pig spinal cord white matter

Cellular destruction following ischemic insult may be due to secondary injury mechanisms, not the oxygen-glucose deprivation itself. We have examined the effect of acrolein, an aldehyde product of lipid peroxidation (LPO) and oxidative stress, on the axons in isolated guinea pig spinal cord white matter following ischemic insult. We have found that acrolein at 50 microM, which is unharmful to spinal cord when applied alone, causes action potential conduction failure and membrane disruption following 1 to 2 h of exposure when applied during the reperfusion period. Ischemic insult also exacerbates the effect of acrolein at 200 microM, which does inflict functional and anatomical damage when applied alone. Unlike metabolic poisoning, acrolein-mediated damage is not a function of axonal size and does not affect the refractoriness in response to dual and multiple stimuli. These results indicate that spinal cord axons, in addition to experiencing elevated free radicals, are more vulnerable to acrolein attack when the level of oxygen and glucose is low. We conclude that free radicals and lipid peroxidation in general, and acrolein in specific, may play a critical role in cellular destruction and functional loss in such injury.

[Functional prognosis of paraplegia due to cord ischemia: a retrospective study of 23 patients]

The functional prognosis of spinal cord infarct is not well known, complicating care of patients suffering from ischemic paraplegia. The aim of this study was to evaluate the clinical and functional outcome of patients with spinal cord infarct treated in rehabilitation centers in order to identify factors influencing functional outcome. We studied cases of non-trauma-related paraplegia treated between 1992 and 1999. Spinal compression and infectious and inflammatory myelopathy were excluded. Age, gender, cardiovascular risk factors, initial and final clinical findings according to the American Spinal Injury Association (ASIA/IMSOP) criteria, MRI findings, and initial urodynamic findings were analyzed. Two groups were identified regarding extension of the spinal cord infarct to the cone or not. Assessment of functional outcome was based on the Frankel classification, ambulatory ability, wheelchair use, and bladder control. Cases of spinal cord infarct were then classified according to extension to the cone or not, determined on the basis of initial clinical, MRI, and urodynamic findings. Twenty-three patients (19 males and 4 females) were selected for analysis. Mean age was 54 years, with no mortality during the follow-up period. At discharge, the group of nine patients whose infarct had not extended to the medullary cone had a significantly better motor recovery using the ASIA motor score (p<0.01). Patients whose infarct did not extend to the cone used wheelchairs less often, were more often in Frankel class D (p<0.05), and had normal bladder control more often (p<0.05) than patients whose infarct extended to the cone. Lack of extension to the medullary cone appeared to be a factor predictive of better functional outcome.

Evaluation of Rapid Ischemic Preconditioning in a Rabbit Model of Spinal Cord Ischemia

Background

Rapid ischemic preconditioning (IPC) has been shown to reduce cellular injury after subsequent cardiac and cerebral ischemia. However, the data on rapid IPC of the spinal cord is limited. The authors investigated whether pretreatment with sublethal ischemia of spinal cord can attenuate neuronal injury after spinal cord ischemia in rabbits.

Methods

Forty-seven male New Zealand white rabbits were randomly assigned to one of three groups (n = 15 or 16 each). In the IPC(-) group, the infrarenal aorta was occluded for 17 min to produce spinal cord ischemia. In the IPC(+) group, 5 min of aortic occlusion was performed 30 min before 17 min of spinal cord ischemia. In the sham group, the aorta was not occluded. Hind limb motor function was assessed at 3 h, 24 h, 4 days, and 7 days after reperfusion using Tarlov scoring (0 = paraplegia; 4 = normal). Animals were killed for histopathologic evaluation at 24 h or 7 days after reperfusion. The number of normal neurons in the anterior spinal cord (L4-L6) was counted.

Results

Neurologic scores were significantly higher in the IPC(+) group than the IPC(-) group at 3 and 24 h after reperfusion (P &lt; 0.05). However, neurologic scores in the IPC(+) group gradually decreased and became similar to those in the IPC(-) group at 4 and 7 days after reperfusion. At 24 h after reperfusion, the numbers of normal neurons were significantly higher in the IPC (+) group than in the IPC(-) group (P &lt; 0.05) and were similar between the IPC(+) and sham groups. At 7 days after reperfusion, there was no difference in the number of normal neurons between the IPC(+) and IPC(-) groups.

Conclusion

The results indicate that rapid IPC protects the spinal cord against neuronal damage 24 h but not 7 days after reperfusion in a rabbit model of spinal cord ischemia, suggesting that the efficacy of rapid IPC may be transient.

Neuroprotective effect of N-acetylcysteine and hypothermia on the spinal cord ischemia-reperfusion injury

The purpose of this study was to investigate the effect of N-acetylcysteine (NAC) on spinal cord ischemia-reperfusion (I-R) in rabbits. Thirty rabbits were divided into five equal groups, group I (sham-operated, no I-R), group II (control, only I-R), group III (I-R+NAC), group IV (I-R+hypothermia), group V (I-R+NAC+hypothermia). Spinal cord ischemia was induced by clamping the aorta both below the left renal artery and above the aortic bifurcation. Forty-eight hours postoperatively, the motor function of the lower limbs was evaluated in each animal according to Tarlov Score. Spinal cord samples were taken to evaluate the histopathological changes. The sham-operated rabbits (group I) showed no neurologic deficit (Score=4). Paraplegia (Score=0) developed in all rabbits in the control group (group II). Administration of 50 mg/kg of NAC (group III) resulted in significant reduction of motor dysfunction (Score=3.1+/-1.3, p=0.002). Application of hypothermia alone (group IV) showed significant recovery of motor functions (Score=3.0+/-1.1, p=0.002), and combination of hypothermia and 50 mg/kg of NAC (group V) showed complete recovery of lower limb motor function (Score=4, p=0.001). Histologic examination of the spinal cord in rabbits with paraplegia revealed several injured neurons. The cords of animals with no motor function deficits showed only minimal cellular infiltrates in the gray matter, and there was good preservation of nerve cells. NAC showed protective effects of the spinal cord. Moderate hypothermia alone also showed protective effects. Combined use of NAC and hypothermia resulted in highly significant recovery of spinal cord function.