Central nervous system trauma : journal of the American Paralysis Association最新文献

Nor-binaltorphimine (nor-BNI) is a recently developed opiate antagonist that has a high degree of selectivity for kappa-opiate receptors. Because of the proposed role of kappa-opiate receptors in mediating secondary damage after spinal trauma, the effect of nor-BNI was studied in a well-characterized model of traumatic spinal cord injury in rats. Nor-BNI, at a dose of 10 mg/kg administered intravenously at 15 min following impact trauma to T-9, significantly improved neurological recovery, measured both in terms of Tarlov motor scores and ability to maintain position on an inclined plane. Given intrathecally, at doses that were ineffective systemically (0.1 mg/kg), nor-BNI also significantly improved neurological recovery after trauma. These data are consistent with the hypothesis that endogenous opioids, through actions at kappa-opiate receptors within the spinal cord, contribute to the pathophysiological changes after spinal trauma that lead to irreversible tissue damage, and indicate that kappa-receptor antagonists may be beneficial for the treatment of acute spinal cord injury.

Eicosanoids are known mediators of inflammation, vascular permeability, and are involved in microcirculatory blood flow regulation. To study their potential involvement in the pathophysiology of CNS trauma we used a rabbit spinal cord trauma model. Rabbits were subjected to lumbar spinal cord trauma produced by a modification of the Allen weight-drop method. TXB2, 6-keto-PGF1 alpha, PGE2, and 5-hydroxyeicosatetraenoic acid (5-HETE) release from spinal cord slices incubated ex vivo were measured by radioimmunoassay at 5, 30 min, 24 hrs, and 2 wks after trauma. Five and 30 min after trauma the TXB2/6-keto-PGF1 alpha ratio was elevated and the release of 5-HETE at 5 min after trauma increased in the injured spinal cord whereas release of 6-keto-PGF1 alpha and PGE2 remained at base-line levels. In the thoracic spinal cord, TXB2 and 6-keto-PGF1 alpha release were increased at 30 min after trauma. Release of 5-HETE from the injured spinal cord was also elevated 24 hrs after trauma. Two wks after trauma, TXB2 and 6-keto-PGF1 alpha release were also elevated in the injured spinal cord. Measurements of tissue water content by microgravimetry indicated progressive edema in the injury site while histopathological evaluation indicated progressive damage and tissue destruction. The results of this study suggest that eicosanoids may be involved in the pathophysiology of spinal cord trauma through two potential mechanisms: 1) site specific increase in the TXB2/6-keto-PGF1 alpha ratio immediately following trauma which is due primarily to an increase in TXA2 synthesis; 2) the increase synthesis of 5-HETE which signals the activation of the 5-lipoxygenase pathway of arachidonate metabolism and production of mediators that are involved in inflammatory mechanisms and may affect local blood flow regulation and blood-spinal cord barrier integrity.

Cats, injured by a mechanical plus hypoxic model of traumatic brain injury, were treated by intracisternal injection of a modified loop diuretic (L-644,711). This drug inhibits the chloride/bicarbonate anion exchange transport system. The treatment resulted in a significant decrease in mortality from 61 to 21%, and an improvement in both neurological status and EEG activity of the surviving animals. The dose of drug given intracisternally was at least 175 times less than the dosage we previously found was needed to achieve a comparable effect when the drug was given intravenously. The present results suggest that certain types of head injury can be treated by drugs which affect cellular anion transport processes in the brain.

The sites and mechanisms by which thyrotropin-releasing hormone (TRH) may ameliorate the effects of spinal cord contusion were studied in the rabbit. We have examined the actions of an effective intravenous TRH infusion on the spinal content and utilization of the monoamine neurotransmitters (norepinephrine [NE], dopamine [DA], and serotonin [5-HT]) in both control and injured animals. The ability of TRH to penetrate the blood-brain barrier was determined by the measurement of spinal cord TRH immunoreactivity and the effect of TRH upon the development of traumatic edema was evaluated. TRH was found to enter the spinal cord to a large extent in approximately half the animals, but to a lesser degree in the remainder. This indicates the potential for a central site of action. In this regard, TRH induced a significant increase in the metabolism or utilization of 5-HT above the injury site. This effect was not observed in control animals. Finally, TRH was able to cancel the formation of edema at the injury site. These results are correlated with previously described mechanisms and are discussed in terms of the co-existence of TRH and 5-HT in raphe-spinal neurons descending from the medulla.

Our report deals with 24 patients who were treated neurosurgically for spinal space occupying lesions and in whom a noninvasive technique of intraoperative monitoring with somatosensory evoked potentials (SEP) was carried out. Reproducible potentials were obtained intraoperatively in each case, but only patients in whom potentials could be obtained preoperatively were included in the study. Using changes in amplitudes of up to 50% of the starting value as criteria, it was possible to make an accurate statement as to the expected postoperative neurological status in 22 patients (91.7%). We found false positive results in 2 cases (8.3%), but no false negative results were observed. In one patient, a postoperative complication caused by bleeding could be discovered in the early stages by means of postoperative SEP-monitoring. The results confirm the reliability and usefulness of this noninvasive technique when applied intraoperatively. Furthermore, the value of SEP-monitoring during the early postoperative phase in cases where the clinical judgment is limited due to anesthesia is emphasized. The secondary postoperative deterioration in the neurological status of one patient with a ventral space occupying lesion could not, however, be detected with the SEP monitoring. The use of the motor stimulation technique could be an advantageous adjunct in intraoperative and perioperative monitoring, particularly in cases where primarily motor pathways are at risk.

Transient injuries to the central nervous system, whether due to trauma or ischemia, often produce long lasting metabolic derangements, lipid peroxidation, edema, and falls in blood flow at the lesion site. Because these post-injury responses are believed to be causes of secondary injury, much research effort has been devoted to developing therapies that prevent them. Recent studies suggest that excessive Ca entry into injured cells instigates these post-injury responses. A new theory is proposed to explain these post-injury responses. This theory posits that Ca ions entering dying cells activate phospholipases that break down membranes to release phosphates. The phosphates then bind and precipitate Ca ions, producing the profound and prolonged decreases in extracellular Ca activity that have been observed in traumatized spinal cords and ischemic brains. The phospholipase activity also facilitates release of lipid peroxides which enhance edema and reduce blood flow. Both of these in turn decrease Ca diffusion to the lesion site and slow the recovery of extracellular Ca activity, giving the tissue time to recover and avoiding the consequences of rapid restoration of extracellular Ca activity. The theory suggests that central nervous tissues evolved these Ca-activated responses as a general mechanism to protect neurons against excessive Ca entry. Brain and spinal cord tissues contain very high concentrations of phosphates, many times greater than is necessary to bind all the Ca ions in the tissues. This excessive Ca buffering capacity enables the tissue to sacrifice a small proportion of severely injured cells to reduce Ca entry into less severely injured neurons. This process will also rapidly eliminate moribund cells that may otherwise linger and consume oxygen and metabolic substrates better utilized by the remaining cells. If confirmed, this theory raises serious questions concerning the current experimental therapeutic approaches to CNS trauma and stroke. Therapy should perhaps be designed to optimize rather than to abort the post-injury responses.

Fluid-percussion models of traumatic brain injury produce injury by rapidly injecting fluid volumes into the epidural space. In the present study, we characterized the physiological, histopathological, and neurological responses in a new model of midline (vertex) fluid-percussion injury of graded severity in the rat. All levels of injury produced transient (acute) hypertension, which was followed by a significant and prolonged hypotension at the higher levels of injury. There was also postinjury suppression if EEG amplitudes, which was related to the severity of injury. However, there were no significant changes in brainstem auditory evoked potentials (BAERs) at any level of injury. Neurological scores over a 4-week postinjury period were directly correlated with the severity of injury. Survival rates were significantly decreased at the higher magnitudes of injury. The extent of postinjury hemorrhage and blood-brain barrier disruption (as evidenced by extravasation of Evans Blue Albumin complex) was related to the magnitude of injury. These data demonstrate that the midline (vertex) model of fluid-percussion injury in the rat reproduces many of the features of head injury observed in other models and species and may serve as a useful cost-effective model for the study of the pathophysiology and treatment of traumatic brain injury.