Comparison of spinal cord evoked potentials and peripheral nerve evoked potentials by electric stimulation of the spinal cord under acute spinal cord compression in cats

Multiple myeloma presenting with acute bony spinal cord compression and mechanical instability successfully managed nonoperatively

OBJECT Convection-enhanced delivery (CED) is a method for distributing small and large molecules locally into the interstitial space of the spinal cord. Delivering these molecules to the spinal cord is otherwise difficult due to the blood-spinal cord barrier. Previous research has proven the efficacy of CED for delivering molecules over long distances along the white matter tracts in the spinal cord. Conversely, the characteristics of CED for delivering molecules to the gray matter of the spinal cord remain unknown. The purpose of this study was to reveal regional distribution of macromolecules in the gray and white matter of the spinal cord with special attention to the differences between the gray and white matter. METHODS Sixteen rats (F344) underwent Evans blue dye CED to either the white matter (dorsal column, 8 rats) or the gray matter (ventral horn, 8 rats) of the spinal cord. The rates and total volumes of infusion were 0.2 μl/min and 2.0 μl, respectively. The infused volume of distribution was visualized and quantified histologically. Computational models of the rat spinal cord were also obtained to perform CED simulations in the white and gray matter. RESULTS The ratio of the volume of distribution to the volume of infusion in the gray matter of the spinal cord was 3.60 ± 0.69, which was comparable to that of the white matter (3.05 ± 0.88). When molecules were injected into the white matter, drugs remained in the white matter tract and rarely infused into the adjacent gray matter. Conversely, when drugs were injected into the gray matter, they infiltrated laterally into the white matter tract and traveled longitudinally and preferably along the white matter. In the infusion center, the areas were larger in the gray matter CED than in the white matter (Mann-Whitney U-test, p < 0.01). In computational simulations, the aforementioned characteristics of CED to the gray and white matter were reaffirmed. CONCLUSIONS In the spinal cord, the gray and white matter have distinct characteristics of drug distribution by CED. These differences between the gray and white matter should be taken into account when considering drug delivery to the spinal cord. Computational simulation is a useful tool for predicting drug distributions in the normal spinal cord.

Cognitive and structural brain abnormalities are common following traumatic brain injury (TBI). The authors compared cognition and brain structure in 14 TBI survivors and 28 matched healthy comparison subjects. TBI survivors showed reduced cerebral volume, due mainly to white matter changes, and poorer attention, psychomotor speed, and memory. Severity of white matter abnormality correlated with worse performance on several cognitive measures that distinguished between groups. Using voxel-based morphometry, regions of reduced white matter concentration were found throughout the cerebrum along with more localized gray matter reductions. Findings suggest that diffuse rather than focal aspects of TBI contribute most to cognitive outcome.

Spinal cord stimulation (SCS) applied between T8 and T11 segments has been shown to be effective for the treatment of chronic pain of the lower back and limbs. However, the mechanism of the analgesic effect at these medullary levels remains unclear. Numerous studies relate glial cells with development and maintenance of chronic neuropathic pain. Glial cells are electrically excitable, which makes them a potential therapeutic target using SCS. The aim of this study is to report glia to neuron ratio in thoracic segments relevant to SCS, as well as to characterize the glia cell population at these levels. Dissections from gray and white matter of posterior spinal cord segments (T8, T9, intersection T9/T10, T10 and T11) were obtained from 11 human cadavers for histological analyses. Neuronal bodies and glial cells (microglia, astrocytes and oligodendrocytes) were immunostained, microphotographed and counted using image analysis software. Statistical analyses were carried out to establish significant differences of neuronal and glial populations among the selected segments, between the glial cells in a segment, and glial cells in white and gray matter. Results show that glia to neuron ratio in the posterior gray matter of the human spinal cord within the T8-T11 vertebral region is in the range 11:1 to 13:1, although not significantly different among vertebral segments. Glia cells are more abundant in gray matter than in white matter, whereas astrocytes and oligodendrocytes are more abundant than microglia (40:40:20). Interestingly, the population of oligodendrocytes in the T9/T10 intersection is significantly larger than in any other segment. In conclusion, glial cells are the predominant bodies in the posterior gray and white matter of the T8-T11 segments of the human spinal cord. Given the crucial role of glial cells in the development and maintenance of neuropathic pain, and their electrophysiological characteristics, anatomical determination of the ratio of different cell populations in spinal segments commonly exposed to SCS is fundamental to understand fully the biological effects observed with this therapy.

Mechanical properties of spinal cord grey matter and white matter in confined compression

Spinal cord blood flow (SCBF) was measured in 24 rhesus monkeys after injury to the cord produced by the inflatable circumferential extradural cuff technique. Measurement of regional blood flow in the white and gray matter of the cord in areas of 0.1 sq mm was achieved with the 14C-antipyrine autoradiographic technique and a scanning microscope photometer. After moderate cord injury (400 mm Hg pressure in the cuff maintained for 5 minutes), which produced paraplegia in 50% of animals and moderate to severe paresis in the other 50%, mean white matter SCBF was significantly decreased for up to 1 hour. White matter blood flow then rose to normal levels by 6 hours posttrauma and was significantly increased by 24 hours posttrauma. Gray matter SCBF was significantly decreased for the entire 24-hour period posttrauma. After severe cord injury (150 mm Hg pressure in the cuff maintained for 3 hours), which produced total paraplegia in almost all animals; SCBF in white and hours), which prodced total paraplegia in almost all animals, SCBF in white and gray matter was reduced to extremely low levels for 24 hours posttrauma. In addition, focal decreases in SCBF were seen in white and gray matter for considerable distances proximal and distal to the injury site. It is concluded that acute compression injury of the spinal cord is associated with long-lasting ischemia in the cord that increases in severity with the degree of injury.

Acute spinal cord injury was induced by a clip compression model in rats to approximate spinal cord injury encountered in spinal surgery. Spinal somatosensory-evoked potential neuromonitoring was used to study the electrophysiologic change. To compare and correlate changes in evoked potential after acute compression at different core temperatures with postoperative neurologic function and histologic change, to evaluate current intraoperative neuromonitoring warning criteria for neural damage, and to confirm the protective effect of hypothermia in acute spinal cord compression injury by electrophysiologic, histologic, and clinical observation. With the increase in aggressive correction of spinal deformities, and the invasiveness of surgical instruments, the incidence of neurologic complication appears to have increased despite the availability of sensitive intraoperative neuromonitoring techniques designed to alert surgeons to impending neural damage. Many reasons have been given for the frequent failures of neuromonitoring, but the influence of temperature-a very important and frequently encountered factor-on evoked potential has not been well documented. Specifically, decrease in amplitude and elongation of latency seem not to have been sufficiently taken into account when intraoperative neuromonitoring levels were interpreted and when acceptable intraoperative warning criteria were determined. Experimental acute spinal cord injury was induced in rats by clip compression for two different intervals and at three different core temperatures. Spinal somatosensory-evoked potential, elicited by stimulating the median nerve and recorded from the cervical interspinous C2-C3, was monitored immediately before and after compression, and at 15-minute intervals for 1 hour. Spinal somatosensory-evoked potential change is almost parallel to temperature-based amplitude reduction and latency elongation. Significant neurologic damage induced by acute compression of the cervical spinal cord produced a degree of effect on the amplitude of spinal somatosensory-evoked potential in normothermic conditions that differed from the effect in moderately hypothermic conditions. Using the same electromonitoring criteria,moderately hypothermic groups showed a significantly higher false-negative rate statistically (35%) than normothermic groups (10%). Systemic cooling may protect against the detrimental effects of aggressive spinal surgical procedures. There is still not enough published information available to establish statistically and ethically acceptable intraoperative neuromonitoring warning and intervention criteria conclusively. Therefore, an urgent need exists for further investigation. Although a reduction of more than 50% in evoked potential still seems acceptable as an indicator of impending neural function loss, maintenance of more than 50% of baseline evoked potential is no guarantee of normal postoperative neural function, especially at lower than normal temperatures.

The gray matter of the cervical spinal cord has been thought to be equally or less rigid than the white matter. Based on this assumption, various studies have been conducted on the changes of stress distributions within the spinal cord under mechanical compression, although the mechanical properties of the white and gray matters had not been fully elucidated. The present study measured the mechanical properties of the white and gray matter of bovine spinal cords. For both the white and gray matter, the stress-strain curves had a nonlinear region, followed by a linear region, and then a region where the stresses plateaued before failure. In the nonlinear region, stress was not significantly different between the gray and white matter samples (strain approximately 0-10%), while stress and Young's modulus in the gray matter was significantly higher than the white matter in the linear part of the curve. The gray matter ruptured at lower strains than the white matter. These findings demonstrated the gray matter is more rigid and fragile than the white matter, and the conventional assumption (i.e., the white matter is more rigid than the gray matter) is not correct. We then applied our data to computer simulations using the finite element method, and confirmed that simulations agreed with actual magnetic resonance imaging findings of the spinal cord under compression. In future computer simulations, including finite element method using our data, changes in stress and strain within the cervical spinal cord under compression would be clarified in more detail, and our findings would also help to elucidate the area which can easily receive histologic damage or which could have hemodynamic disorders under mechanical compression, as well as severity and location of biochemical and molecular biological changes.

The aim of this study was to investigate whether or not conductive spinal cord evoked potentials and spinal cord function change correspondingly with each other. The relationship between conductive spinal cord evoked potentials and locomotor function during acute spinal cord compression in animals was investigated. In decerebrate cats, controlled locomotion can be induced by electrical stimuli in the mesencephalic locomotor region. Conductive spinal cord evoked potentials were recorded at the L3 level of the spinal cord and stimuli were given at the T4 segment. The locomotor function was evaluated through electromyograms of the hind limbs. By compressing the spinal cord at L1, both the conductive spinal cord evoked potentials and the locomotor function gradually decreased. When the first negative potential amplitude of conductive spinal cord evoked potentials was decreased to half the level found in normal cats, locomotor function was injured irreversibly. These results showed that changes in the conductive spinal cord evoked potentials were related to changes in locomotor function. The 50% level of the first negative potential amplitude was considered to be the critical level at which irreversible spinal cord paralysis occurred in the cats.

Complement Plays an Important Role in Spinal Cord Injury and Represents a Therapeutic Target for Improving Recovery following Trauma

Draw A Cross-Section through the spinal cord; it is ovoid and has a thin fissure on its anterior side. The internal gray matter resembles a butterfly (or a bikini-top). Label the top of the diagram as “posterior” and the bottom as “anterior.” The ratio of gray matter to white matter varies throughout the rostro–caudal length of the spinal cord. In the lumbosacral spinal cord, the gray matter outsizes the white matter, whereas in the thoracic spinal cord, the white matter outsizes the gray matter. Why is this? At the bottom of the spinal cord, the ascending white matter tracts are narrow (they are just beginning to coalesce) and the descending white matter motor fibers have, for the most part, already terminated within the spinal cord gray matter, so they are also narrow. Conversely, in the thoracic cord, a high density of white matter lumbosacral afferent sensory fibers have accumulated and the white matter motor efferent bundles destined for the lumbosacral cord are still dense with fibers. Additionally, there are gray matter enlargements in both the lumbosacral and cervical spinal cord regions because of the high density of sensory and motor neurons required to innervate the distal extremities, which helps enlarge the relative size of the gray matter at those levels. But in the thoracic spinal cord, the gray matter size is small. Thoracic-innervated abdominal musculature requires less eloquent wiring than the lumbosacral-innervated footwork requisite for dancing or the cervical-innervated finger coordination required to play the piano. Thus, in the lumbosacral cord, the gray matter clearly outsizes the white matter and in the thoracic spinal cord, the white matter outsizes the gray matter. In the cervical spinal cord, both the gray and white matter are plump for reasons you can infer from the prior discussion.

Spinal cord injury (SCI) is one of the serious central nervous system injuries and the incidence of SCI continues to increase. Previous studies have indicated that electroacupuncture (EA) is beneficial for promoting recovery after SCI. In the present study, we attempted to evaluate how EA can promote the neural repair in SCI model rats by observing changes in the Notch signaling pathway. Experimental rats were randomly divided into four groups. Each group had its own intervention period: 1 day, 7 days, 14 days, and 28 days, and five randomized subgroups: blank control (B) group, blank electroacupuncture (BE) group, sham operation (S) group, model control (M) group and EA group. Animals in the EA group and the BE group were treated with EA at Dazhui (GV14) and Mingmen (GV4) acupoints for 20 min. After the intervention period, the Basso-Beattie-Bresnahan (BBB) score was used to evaluate the neurological function. We found that BBB score increased in EA-treated groups. Hematoxylin and eosin staining was used to observe pathological changes in the injured spinal cord and the results showed that EA therapy could promote the repair of injured spinal cord tissue. Immunohistochemistry and Western blot methods were used to detect the expression of proteins Delta1, Presenilin1, Hes1, and Hes5 in the injured spinal cord. The results showed that the expression levels of Delta1, Presenilin1, Hes1, and Hes5 increased significantly after SCI and decreased after EA treatment. Our study suggested that the possible mechanism by which EA could benefit the recovery after SCI in rats may include inhibiting the Notch signaling pathway and regulating the downstream proteins expression. In addition, our study can provide reference for selecting acupoints and treatment cycle in the treatment of SCI.

To explore the effect and underlying mechanism of decompression(DE)combined with Governor Vessel(GV)electro-acupuncture(EA) on rats with acute severe upper cervical spinal cord compression injury. Thirty SPF rats were randomly divided into 5 groups(control group A, B and experiment group C, D, E), 6 rats in each group. The model of acute severe upper cervical spinal cord compression injury were made by forcing a balloon catheter put in atlas pillow clearance. The group A was blank one, the group B put balloon catheter in atlas pillow clearance without forcing, and the group C, D, E sustained compressed for 48 h. The group C received electric acupuncture intervention, selecting the Baihui and Dazhui point, having the continuous wave and frequency of 2 Hz, with the treatment time of 15 min and continuous treatment for 14 d; the group D received methylprednisolone intervention, injected by caudal vein; the group E did not received any intervention again. The arterial blood and injured spinal cord tissue of all the rats were obtained after 14 days' treatment, and BBB score was used to evaluate the change of each group hind limbs motor function, the contents of platelet activating factor(PAF) in injured spinal cord tissue and blood serum were assess by ELISA method; the Caspase-9 expression for each group after 14 days' treatment was assess by Western blot method. BBB scores were(21.000±0.000) points at the 6 time points, that was, 1 h, 48 h after forcing in control group, 24 h, 3 d, 7 d, 14 d after treating in experiment group; the score of experimental groups (group C, D, E) were always lower than control groups(group A, B); compared with group E, group C and D were significantly higher(P<0.05); and there was no significant difference between group C and group D(P>0.05). The results of PAF by ELISA method to measure:the concentration of serum PAF, there was no statistical difference among group A, B, D, E (P>0.05), group C was lower than the other groups (P<0.05); the concentration of tissue PAF, there was no significant difference between group A and group B(P>0.05), group D was significantly higher than that of group A, B, and C(P<0.05), group E was the highest one than that of the other groups(P<0.05). Western blot med tests showed that the Caspase-9 protein expression in group A and B was similar (P>0.05), group C was higher than that of group A and B(P<0.05), group D was higher than group A, B and C(P<0.05), group E was the highest than that of group A, B, C and D (P<0.05). Decompression and Governor Vessel electro-acupuncture on acute severe upper cervical spinal cord compression injury had a better effect compare with decompression and methylprednisolone or simple decompression only, its mechanism may be related to lower the PAF levels and downregulating Caspase-9 protein expression in spinal injury tissue.

Acute compression of the spinal cord is a devastating but treatable disorder. Diseases that cause acute spinal cord compression constitute a special category because they originate in the spinal column and narrow the spinal canal. This review addresses the disorders that account for most instances of acute spinal cord compression: trauma, tumor, epidural abscess, and epidural hematoma. The pathophysiological features and management of these disorders are similar to those of other acute and serious spinal conditions. The medical context of spinal cord compression determines the diagnosis and directs treatment. Traumatic cord compression is often self-evident. Cord compression in patients with . . .

The spinal cord is composed of gray matter and white matter. It is well known that the properties of these two tissues differ considerably. Spinal diseases often present with symptoms that are caused by spinal cord compression. Understanding the mechanical properties of gray and white matter would allow us to gain a deep understanding of the injuries caused to the spinal cord and provide information on the pathological changes to these distinct tissues in several disorders. Previous studies have reported on the physical properties of gray and white matter, however, these were focused on longitudinal tension tests. Little is known about the differences between gray and white matter in terms of their response to compression. We therefore performed mechanical compression test of the gray and white matter of spinal cords harvested from cows and analyzed the differences between them in response to compression. We conducted compression testing of gray matter and white matter to detect possible differences in the collapse rate. We found that increased compression (especially more than 50% compression) resulted in more severe injuries to both the gray and white matter. The present results on the mechanical differences between gray and white matter in response to compression will be useful when interpreting findings from medical imaging in patients with spinal conditions.