Ineffectiveness of dexamethasone for treatment of experimental cerebral infarction

Research progress on the role of hormones in ischemic stroke

Ischemic stroke is a major cause of death and disability around the world. However, ischemic stroke treatment is currently limited, with a narrow therapeutic window and unsatisfactory post-treatment outcomes. Therefore, it is critical to investigate the pathophysiological mechanisms following ischemic stroke brain injury. Changes in the immunometabolism and endocrine system after ischemic stroke are important in understanding the pathophysiological mechanisms of cerebral ischemic injury. Hormones are biologically active substances produced by endocrine glands or endocrine cells that play an important role in the organism's growth, development, metabolism, reproduction, and aging. Hormone research in ischemic stroke has made very promising progress. Hormone levels fluctuate during an ischemic stroke. Hormones regulate neuronal plasticity, promote neurotrophic factor formation, reduce cell death, apoptosis, inflammation, excitotoxicity, oxidative and nitrative stress, and brain edema in ischemic stroke. In recent years, many studies have been done on the role of thyroid hormone, growth hormone, testosterone, prolactin, oxytocin, glucocorticoid, parathyroid hormone, and dopamine in ischemic stroke, but comprehensive reviews are scarce. This review focuses on the role of hormones in the pathophysiology of ischemic stroke and discusses the mechanisms involved, intending to provide a reference value for ischemic stroke treatment and prevention.

Role of microglia in ischemic focal stroke and recovery: focus on Toll-like receptors

Stroke is the leading cause of disability in adults. Drug treatments that target stroke-induced pathological mechanisms and promote recovery are desperately needed. In the brain, an ischemic event triggers major inflammatory responses that are mediated by the resident microglial cells. In this review, we focus on the microglia activation after ischemic brain injury as a target of immunomodulatory therapeutics. We divide the microglia-mediated events following ischemic stroke into three categories: acute, subacute, and long-term events. This division encompasses the spatial and temporal dynamics of microglia as they participate in the pathophysiological changes that contribute to the symptoms and sequela of a stroke. The importance of Toll-like receptor (TLR) signaling in the outcomes of these pathophysiological changes is highlighted. Increasing evidence shows that microglia have a complex role in stroke pathophysiology, and they mediate both detrimental and beneficial effects on stroke outcome. So far, most of the pharmacological studies in experimental models of stroke have focused on neuroprotective strategies which are impractical for clinical applications. Post-ischemic inflammation is long lasting and thus, could provide a therapeutic target for novel delayed drug treatment. However, more studies are needed to elucidate the role of microglia in the recovery process from an ischemic stroke and to evaluate the therapeutic potential of modulating post-ischemic inflammation to promote functional recovery.

Dexamethasone enhances necrosis-like neuronal death in ischemic rat hippocampus involving μ-calpain activation

Transient forebrain ischemia (TFI) leads to hippocampal CA1 pyramidal cell death which is aggravated by glucocorticoids (GC). It is unknown how GC affect apoptosis and necrosis in cerebral ischemia. We therefore investigated the co-localization of activated caspase-3 (casp-3) with apoptosis- and necrosis-like cell death morphologies in CA1 of rats treated with dexamethasone prior to TFI (DPTI). In addition, apoptosis- (casp-9, casp-3, casp-3-cleaved PARP and cleaved α-spectrin 145/150 and 120kDa) and necrosis-related (calpain-specific casp-9 cleavage, μ-calpain upregulation and cleaved α-spectrin 145/150kDa) cell death mechanisms were investigated by Western blot analysis. DPTI expedited CA1 neuronal death from day 4 to day 1 and increased the magnitude of CA1 neuronal death from 66.2% to 91.3% at day 7. Furthermore, DPTI decreased the overall (days 1-7) percentage of dying neurons displaying apoptosis-like morphology from 4.7% to 0.3% and, conversely, increased the percentage of neurons with necrosis-like morphology from 95.3% to 99.7%. In animals subjected to TFI without dexamethasone (ischemia-only), 7.4% of all dying CA1 neurons were casp-3-immunoreactive (IR), of which 3.1% co-localized with apoptosis-like and 4.3% with necrosis-like changes. By contrast, DPTI decreased the percentage of dying neurons with casp-3 IR to 1.4%, of which 0.3% co-localized with apoptosis-like changes and 1.1% with necrosis-like changes. Western blot analysis from DPTI animals showed a significant elevation of μ-calpain, a calpain-produced necrosis-related casp-9 fragment (25kDa) and cleavage of α-spectrin into 145/150kDa fragments at day 4, whereas in ischemia-only animals a significant increase of casp-3-cleaved PARP, cleavage of α-spectrin into 145/150 and 120kDa fragments was detected at day 7. We conclude that DPTI, in addition to augmenting and expediting CA1 neuronal death, causes a shift from apoptosis-like cell death to necrosis involving μ-calpain activation.

Snapshot of 1973 and 1974: critical thinkers and contemporary research ideas in neurosurgical anesthesia during the first years of SNACC

The year 2012 marks the 40th anniversary of the Society of Neuroscience in Anesthesiology and Critical Care (SNACC). To celebrate this occasion, we provide a review, speculative synthesis, and commentary addressing research relevant to neurosurgical anesthesiology in 1973 and 1974--the early years of SNACC. We address topics such as effects of anesthetic drugs, neuroprotection, cerebral physiology, and monitoring as they relate to the perioperative care of neurosurgical patients or patients experiencing or at risk for neurological disorders. Our hypothesis is that a review of these publications will identify the foundations of research and practice concepts that persist until today and will also identify concepts that have dwindled or outright disappeared.

The function of the adrenocortical axis in permanent middle cerebral artery occlusion: effect of glucocorticoids on the neurological outcome

We characterized the effect of acute ischemic stroke on the activation of the hypothalamic-pituitary-adrenal (HPA) axis and evaluated the role of glucocorticoids (GC) in the clinical outcome following ischemic stroke. Male spontaneous hypertensive rats underwent permanent middle cerebral artery occlusion (PMCAO) and developed a cortical infarct. At 4h post-PMCAO or sham operation, serum levels of ACTH and corticosterone (CS) were elevated 5 and 4 fold respectively as compared to controls and then returned to basal levels at 24h post surgery. In these experimental groups we found also a significant depletion of median eminence (ME)-CRH(41). In adrenalectomized (Adx) rats that underwent PMCAO the degree of motor disability and infarct volume was similar to that of intact rats. Administration of dexamethasone (Dex) to Adx-PMCAO rats significantly improved the motor disability and decreased the infarct volume. However, in sham-Adx with PMCAO, Dex had no effect on these two parameters. In rats with PMCAO or sham-PMCAO, brain production of PGE(2) was significantly increased. This effect was further enhanced in Adx-PMCAO rats and significantly inhibited by Dex. In conclusion, activation of the HPA axis following PMCAO is due to stress induced by surgery. This activation is mediated by hypothalamic CRH(41). Absence of endogenous GC or administration of Dex in naïve rats does not alter motor and pathological parameters in the acute stage following PMCAO. In contrast, administration of Dex significantly improved the outcome following cerebral ischemia in Adx rats which may be due to increased glucocorticoid receptors. Brain production of PGE(2) does not play an important role in the pathophysiology of the acute phase of cerebral ischemia.

Treatment of space-occupying cerebral infarction

OBJECTIVE

Patients with a hemispheric infarct accompanied by massive edema have a poor prognosis; the case fatality rate may be as high as 80%, and most survivors are left severely disabled. Various treatment strategies have been proposed to limit brain tissue shifts and to reduce intracranial pressure, but their use is controversial. We performed a systematic search of the literature to review the evidence of efficacy of these therapeutic modalities.

DATA SOURCES

Literature searches were carried out on MEDLINE and PubMed.

STUDY SELECTION

Studies were included if they were published in English between 1966 and February 2002 and addressed the effect of osmotherapy, hyperventilation, barbiturates, steroids, hypothermia, or decompressive surgery in supratentorial infarction with edema in animals or humans.

DATA SYNTHESIS

Animal studies of medical treatment strategies in focal cerebral ischemia produced conflicting results. If any, experimental support for these strategies is derived from studies with animal models of moderately severe focal ischemia instead of severe space-occupying infarction. None of the treatment options have improved outcome in randomized clinical trials. Two large nonrandomized studies of decompressive surgery yielded promising results in terms of reduction of mortality and improvement of functional outcome.

CONCLUSIONS

There is no treatment modality of proven efficacy for patients with space-occupying hemispheric infarction. Decompressive surgery might be the most promising therapeutic option. For decisive answers, randomized, controlled clinical trials are needed.

High-dose methylprednisolone treatment in experimental focal cerebral ischemia

Previous studies using steroids for experimental focal stroke have demonstrated conflicting results, possibly related to dose used or ischemic models employed. In this study we examined high-dose methylprednisolone treatment following permanent and temporary focal cerebral ischemia in the rat. Focal stroke was induced in spontaneously hypertensive rats by permanent right common carotid and either permanent or 3 h of temporary middle cerebral artery (MCA) occlusion. Methylprednisolone (105 mg/kg) was administered intra-arterially. Infarct volume was measured at 24 h after permanent and temporary MCA occlusion. Cerebral edema was determined by measuring right and left hemispheric volumes and water content 24 h after permanent MCA occlusion in one experiment. Methylprednisolone, whether administered in divided doses over 12 h (n = 15 in each group) or a single bolus (n = 9 per group), had no effect on infarct volume after permanent MCA occlusion. Methylprednisolone treatment also had no influence on cerebral edema (n = 9 per group). In two different experiments, methylprednisolone given in divided doses over 12 h (n = 11, n = 25) after temporary MCA occlusion decreased infarct volume (P < 0.05) by 20% compared with saline controls (n = 10, n = 25). High dose methylprednisolone decreased infarct volume following temporary, but not permanent, focal ischemia. The benefit suggests that high dose methylprednisolone may prove useful clinically if reperfusion can be established with thrombolytic agents. Furthermore, the differential treatment effect in the setting of comparable ischemic insults implies that different modifiable biochemical processes may be present during temporary but not permanent focal ischemia, thus providing indirect evidence for reperfusion injury.

Nature, time-course, and extent of cerebral edema in perinatal hypoxic-ischemic brain damage

To ascertain the nature, time-course, and extent of the cerebral edema that accompanies perinatal hypoxic-ischemic brain damage, 7-day postnatal rats were subjected to unilateral right common carotid artery ligation followed by exposure to hypoxia with 8% oxygen for up to 3 hours. Some rat pups were sacrificed during hypoxia-ischemia or recovery for determination of cerebral hemispheric water content and percentage of brain swelling. Other animals were sacrificed and their brains processed either for determination of cerebral cortical edema and infarct volume or for horseradish peroxidase staining. The results indicated that cerebral edema occurs even during the course of hypoxia-ischemia and that the extent and duration of edema formation during the recovery period is dependent upon the severity of tissue injury. The data also disclosed a direct, linear correlation between infarct volume and the extent of cerebral edema. Accordingly, the greater the severity of cerebral edema, the proportionately greater the extent of infarction. Horseradish peroxidase staining, a reflection of vasogenic edema, occurred in 17 of 19 brains in a distribution which corresponded closely to the distribution of neuropathologic alterations observed histologically. The findings indicate that cerebral edema can occur in the absence of consequent infarction and that when infarction does occur, the associated edema contributes little or nothing to the severity of the ultimate brain damage.

Effects of retrograde perfusion of the brain with combined drug therapy after focal ischemia in rat brain

BACKGROUND AND PURPOSE

The ischemic edema associated with blood-brain barrier permeability changes and the excess production of free radicals are serious complications in prolonged cerebral ischemia. We examined the efficacy of transvenous perfusion of the brain, starting treatment 5 hours after occlusion of the middle cerebral artery for a period of 2 hours in rats with the combined agents mannitol (10 ml/2 hr) and dexamethasone (1 mg/2 hr) to counter edema and verapamil (0.05 mg/kg/2 hr) for vasodilation.

METHODS

In experiment 1, blood-brain barrier permeability changes were examined in five groups with six rats each: group C rats underwent 7 hours of middle cerebral artery occlusion with no treatment; group V, treatment with verapamil alone; group VD, treatment with verapamil and dexamethasone; group VM, treatment with verapamil and mannitol; and group VDM, treatment with verapamil, dexamethasone, and mannitol. In experiment 2, we examined local cerebral blood flow, ischemic tissue damage volume, and water content of cerebral hemispheres in two groups of 16 rats each subjected to the same treatment as groups C and VDM rats in experiment 1.

RESULTS

There was a significant reduction of blood-brain barrier permeability changes in the ischemic cortex of rats in group VDM compared with rats in the other groups. In the group undergoing transvenous perfusion of the brain with the three combined agents, there was a significant improvement of cerebral blood flow (39-58%, p < 0.05) in the ischemic cortex and reduction of ischemic cerebral damage volume (22%, p < 0.01) and water content of the ischemic hemisphere (p < 0.05) compared with the control group.

CONCLUSIONS

The therapeutic approach using combined agents is effective treatment when initiated within 5 hours of focal cerebral ischemia in rats.

Effect of steroids on edema and sodium uptake of the brain during focal ischemia in rats

Steroids reduce permeability of the blood-brain barrier and inhibit active sodium transport by brain capillaries in vitro. Since the rate of edema formation during the early stages of ischemia is related to the rate of sodium transport from blood to brain, this study was designed to determine whether steroids reduce ischemic edema formation by inhibiting blood-brain barrier sodium transport. Dexamethasone was compared with progesterone since the latter is a more potent inhibitor of sodium transport in isolated capillaries. Sprague-Dawley rats were treated with vehicle (n = 22) or 2 mg/kg of either dexamethasone (n = 22) or progesterone (n = 17) 1 hour before occlusion of the middle cerebral artery. After 4 hours of ischemia, brain water content and blood-brain barrier permeability to [3H] alpha-aminoisobutyric acid and sodium-22 were determined. In controls, mean +/- SEM water content of tissue in the center of the ischemic zone was 82.4 +/- 0.2%. Brain edema was significantly reduced following pretreatment with either dexamethasone (80.6 +/- 0.1%, p less than 0.001) or progesterone (81.5 +/- 0.3%, p less than 0.05). There was also a significant reduction in blood-brain barrier permeability to alpha-aminoisobutyric acid in normal brain following either treatment (e.g., 2.21 +/- 0.19 and 1.37 +/- 0.10 microliters/g/min, p less than 0.001, for control and dexamethasone treatments, respectively), but no effect on the permeability to sodium (e.g., 1.19 +/- 0.05 and 1.12 +/- 0.11 microliters/g/min for control and dexamethasone treatments, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral protection

Cerebral protection from an ischemic/hypoxic insult implies that tissue injury can be controlled or even prevented by certain therapeutic maneuvers. For example, physiological thresholds may be altered so that tissue vulnerability to the insult is reduced, or the intensity of an insult may be blunted by enhancing brain homeostasis. Such a therapeutic maneuver is carotid endarterectomy to improve blood flow in the disordered hemisphere. Alternatively, drugs with protective properties can be used before or even after the insult to "stabilize" injured tissue and prevent the harmful secondary effects that often follow. Various past and present approaches to cerebral protection employing physiological, pharmacological, and surgical intervention are reviewed. The mechanisms by which each allegedly protects the brain from ischemia and hypoxia are discussed briefly. Promising, but not always successful, approaches used in the past have pointed the way for new and more rational therapies. Truly effective protection of the brain from ischemia and hypoxia depends directly upon our capability to explore basic mechanisms of injury and our willingness to measure accurately and objectively the outcome of newly developed protective measures.

Actinomycin D suppresses the protective effect of dexamethasone in rats affected by global cerebral ischemia

Simultaneous occlusion of both common carotid arteries in female Sprague-Dawley CFY rats produced characteristic symptoms of global cerebral ischemia, such as staggering, circling, convulsions, followed by coma and death. A close correlation existed among these symptoms and the elevation of water and Na+ content, appearing at the stage of staggering; Evans blue extravasation and diminution of K+ content, detected at circling; and the increase in Ca2+ content in the total brain tissue, manifesting itself at the phase of convulsions, indicating the development of cerebral edema due to ischemia. Dexamethasone given subcutaneously in a single 2.0 mg kg-1 dose 5 hours prior to the induction of global cerebral ischemia reduced considerably the morbidity and mortality, the alterations in water and electrolyte content, and albumin leakage in the brain tissue. Actinomycin D, in a dose of 0.5 mg kg-1 injected intravenously 1 hour before steroid treatment, abolished the beneficial effect. This finding suggests that de novo protein synthesis is involved in the cerebroprotective effect of dexamethasone.

Effect of dexamethasone on serum protein extravasation in experimental brain infarcts of monkey: an immunohistochemical study

Experimental brain infarcts were produced in 12 adult baboons (Papio cynocephalus) by transorbital permanent clipping of the left middle cerebral artery. One group (seven monkeys) received daily injections of 1 mg/kg dexamethasone, starting 1 h after vascular occlusion and continuing till the end of the experiment. Another group (five monkeys) was not treated. One week after vascular occlusion the volume of infarcts and peri-infarct edema was estimated morphometrically on histological sections, using Masson's trichrome stain and the peroxidase-anti-peroxidase (PAP) technique for visualization of serum protein extravasation. In the untreated animals the average volume of infarct was 6.57 +/- 4.23% (mean +/- SD) and the volume of edema 7.83 +/- 2.93% of ipsilateral hemisphere. In the treated animals the infarct volume was not different (7.95 +/- 3.00%), but the volume of peri-infarct edema was significantly lower (2.82 +/- 3.06%, p less than 0.05). The results obtained indicate that dexamethasone treatment reduces the development of peri-infarct edema but does not influence the size of infarcts.

The protective effect of combined administration of anti-oxidants and perfluorochemicals on cerebral ischemia

We previously published results of investigations which indicated that the combination of mannitol, which acts as a free radical scavenger, and perfluorochemicals (PFC), which have a strong oxygen-carrying capacity, can be therapeutic in cases of brain infarction. The present experiment tested the hypothesis that the effectiveness of such treatment could be increased by an optimal combination of such scavengers and other chemicals. Fifty-two dogs were used, employing the "canine model of a completely ischemic brain regulated with the perfusion method." A total of six drugs with free radical scavenger capacities were tested: mannitol, vitamin E, vitamin C, Nizofenone (Y-9197), dexamethasone (DEXA) and suloctidil (MY-103). These drugs were administered intravenously 15 minutes prior to the production of ischemia, when cerebral blood flow was reduced to one-tenth its normal volume. After one hour, recirculation was allowed and the recovery of electrical activity of the brain observed for three hours. Judged by the degree of recovery of brain electrical activity, five drugs were considered to have protective effect against brain ischemia: mannitol, vitamin E, MY-103, DEXA and Y-9197. Among these five drugs, mannitol, vitamin E and DEXA are known to be safe and easily used clinically. The combined administration of these three drugs, together with PFC, was also investigated. It was found that the speed and degree of recovery of brain electrical activity were greater when these drugs were given together than when one was administered alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Alteration of pharmacokinetic parameters for pentobarbital by ischemic stroke and reversion to normal by dexamethasone treatment

The values of the pharmacokinetic parameters for pentobarbital were determined in 18 cats, 12 of which were subjected to acute ischemic stroke by ligation of the left middle cerebral artery (LMCA). All 18 ats received 50 mg/kg sodium pentobarbital during operation. The following three experimental groups were formed: control (sham-operated); ischemic stroke plus administration of 4 mg/kg dexamethasone; and ischemic stroke without dexamethasone administration. Ischemic stroke significantly prolonged the plasma half-life of pentobarbital, but concurrent administration of dexamethasone prevented this effect. Ischemic stroke significantly reduced the plasma clearance of pentobarbital, but dexamethasone prevented this reduction. Ischemic stroke significantly increased the area under the plasma pentobarbital concentration-time curve, but dexamethasone prevented this increase. Ischemic stroke significantly reduced the volume of distribution, but dexamethasone did not prevent this reduction. The alterations of the value of these pharmacokinetic parameters for pentobarbital by ischemic stroke and reversion to normal by dexamethasone treatment are discussed in the light of certain known circulatory changes which occur secondary to ischemic stroke and dexamethasone treatment.

Effect of steroid on ischemic brain edema. Analysis of cytotoxic and vasogenic edema occurring during ischemia and after restoration of blood flow

Mongolian gerbils were observed for the effects of beta-methasone on ischemic brain edema which developed during ischemia or after blood flow restoration. The severity of brain edema was determined by measuring water content of the ischemic cerebral hemisphere, using the wet and dry methods. Sodium and potassium ions were extracted from homogenized brains with 0.75N HNO2 and ion concentration measured by flame photometry. Passage of RISA from blood into the cerebral parenchyma, as an indicator of blood-brain barrier change, was determined with a gamma-scintillation counter. In the cytotoxic edema model, animals were killed after 9 h permanent ischemia or 3 h after 1 h ischemia. In the simultaneous cytotoxic and vasogenic edema model, the animals were killed either 20 h or 3 days following 1 h ischemia, or 3 h after blood flow restoration following 6 h ischemia. Steroid treatment was ineffective in ischemic brain edema of the cytotoxic or vasogenic type.

Modification of acute focal ischemia by treatment with mannitol and high-dose dexamethasone

A simple implanted device was used to occlude the left middle cerebral artery (MCA) of 50 conscious cats. In the acute experiments, 10 cats were given mannitol (1.2 gm/kg intravenously) and 10 cats were untreated. The neurological status of the treated cats improved. Perfusion with a mixture of colloidal carbon and buffered paraformaldehyde was carried out from 30 minutes to 12 hours following MCA occlusion. Results of the morphological examination of the brains demonstrated that mannitol delayed the development of neuronal alterations and edema. Measurement of capillary luminal diameters in the ischemic cortex of the untreated cats revealed progressive narrowing with microcirculatory obstruction occurring at 6 hours. Capillary narrowing was absent or minimal in the treated cats during the initial 6 hours. Breakdown of the blood-brain barrier also was delayed by treatment. In the 30 subacute experiments, 10 cats were untreated, 10 cats received mannitol (1.2 gm/kg intravenously), and 10 cats were given a combination of mannitol and high-dose dexamethasone. Although early transient clinical improvement occurred in the treated animals, morphological findings in the brains of the treated and untreated cats following 48 hours of ischemia were not significantly different. Despite the finding that the beneficial effects of mannitol were relatively short-lived (6 to 12 hours), the delay in the development of irreversible changes probably is important as it would allow a longer period of time for the institution of a more definitive form of therapy.

Delayed pentobarbital therapy of acute focal cerebral ischemia

The efficacy of pentobarbital in the delayed treatment of acute cerebral ischemia was investigated in cats. Cerebral ischemia was produced by left middle cerebral artery (LMCA) ligation. Ten cats received 50 mg/kg of pentobarbital prior to ligation; a second group of 10 cats received the same dose of pentobarbital 2 hrs after ligation, and the control group of 7 cats received no pentobarbital. Brains were removed after spontaneous or induced death and the volume infarction was determined histologically. It was found that the volume of brain infarction in the group receiving pentobarbital 2 hrs after ligation was significantly less than that of the control group, which received no pentobarbital; but the volume of infarction in the former group was significantly greater than that found in the experimental group, which received pentobarbital prior to ligation. However, the mortality after LMCA ligation was higher in the 2 experimental groups, which received pentobarbital therapy, than in the control group, which did not receive pentobarbital. An hypothesis was advanced, which speculated that secondary adrenal insufficiency and altered cardiovascular function accounted for the increased mortality after pentobarbital treatment of patients with ischemic stroke.

Is there a real treatment for stroke? Clinical and statistical comparison of different treatments in 300 patients

In the absence of universally accepted criteria for the medical treatment of stroke, we made a rigorously randomized comparative study of different treatments in 300 patients. One group of patients received only a general supportive treatment designed to ensure adequate supplies of water, electrolytes and calories, plus whatever was needed to prevent infection and correct extant associated pathology. Three other groups of patients were treated in the same way but were also given, respectively, one of the following medications: Hydergine (Sandoz) (a mixture of three ergot alkaloids), dexamethasone, and mannitol. No statistically significant difference emerged among any of the treatment groups and the reference group in terms of objective therapeutic results. The authors concluded that, at least with the dosage used in this study, none of the treatments proved more useful than conventional supportive therapy in the first 10 days after a stroke.

Report of Joint Committee for Stroke Resources. IV. Brain edema in stroke

A classification of brain edema is provided as well as an extensive review of the animal models from which we have derived most of the basic information we have about the formation and resolution of edema. The clinical aspects of cerebral edema in stroke are discussed and also modern methods for identifying cerebral edema in the human. Attention is given to computed tomography and enhanced CT and advances in their application to this condition. Treatment of cerebral edema in the stroke patient using glycerol, dextran 40, mannitol, steroids, and other drugs is discussed and the need pointed out for controlled clinical trials of the therapeutic effectiveness of these agents.

Dexamethasone and DMSO in experimental transorbital cerebral infarction

Twenty rhesus monkeys were used to evaluate the effects of dexamethasone and dimethyl sulfoxide (DMSO) following experimental occlusion of the middle cerebral artery (MCA) for 17 hours. Animals were initially treated after four hours while the MCA remained occluded and a series of tests was used to evaluate the neurological and cerebral status of each monkey for seven days. The results show that the gross, microscopic and angiographical picture of dexamethasone and no-treatment controls was practically identical. In contrast, DMSO-treated monkeys showed significant protection from the severe neurological deficits seen in the other groups. It is concluded that DMSO has a positive effect in reducing the neurological deficits seen in this model and may be potentially useful in clinical emoblic stroke.

Changes of epidural pressures after experimental occlusion of one middle cerebral artery in cats

Epidural pressures (EDP) were measured in 29 cats. Twenty cats had the left middle cerebral artery (MCA) occluded; pentobarbital was used for anesthesia for 10 of these, and halothane was used for the other 10. Two cats had sham operations: the MCA was manipulated but not occluded. Seven cats were used for testing the reliability of the EDP devices. EDP was measured successfully and was directly related to the swelling of the brain and to the size of the cerebral infarct resulting from MCA occlusion. Side-to-side pressure gradients were demonstrated in 7 cats with marked increases of EDP after occlusion; in these cats, EDP may have reflected the pressure of compressed cerebral tissue rather than the pressure of cerebrospinal fluid. Cats anesthetized with pentobarbital had greater increases of EDP and died before the end of the period of observation more frequently than cats anesthetized with halothane, probably because of respiratory depression and slower recovery with pentobarbital. Measurements of EDP may be useful for studies of the treatment of cerebral edema in experimental models of acute cerebral ischemia.

Dexamethasone effect on blood-brain barrier damage caused by acute hypertension in x-irradiated rabbits

Unilateral X-ray exposure of brain increases the vulnerability of cerebral vessels to acute hypertension in the brain hemisphere exposed to radiation. A preventive effect of dexamethasone was observed when treatment with the drug was started before irradiation; but also when the drug was given 24 h before acute hypertension was induced, 1 week after irradiation.

Therapy against brain swelling in stroke patients. A retrospective clinical study on 227 patients

The effectiveness of cerebral antiedema agents in stroke has been questioned. Animal and clinical work is inconclusive about steroids and osmotic drugs. A retrospective study of a continuous series of 227 stroke patients treated in the acute stage (some with dexamethasone alone, some with dexamethasone plus hyperosmotic mannitol infusions, and some without antiedema therapy) showed no significant difference in the ten-day survival rate. On this criterion, there is no ground for the systematic use of such agents against this type of brain swelling.

Immediate effects of cerebral ischemia: evolution and resolution of neurological deficits after experimental occlusion of one middle cerebral artery in conscious cats

Acute occlusion of the left middle cerebral artery (MCA) was accomplished without anesthesia and inside an intact cranium containing cerebrospinal fluid (CSF) in ten cats five to nine days after implantation of an occlusive device through the orbit. Immediate neurological deficits included forced ambuxlation, circling, and tonic deviation of the head and neck toward the side of the occluded artery; weakness of the opposite limbs; and an apathetic or akinetic state. Two cats died within 24 hours. The other eight cats improved but secondary deficits developed in two, causing death. In two of the remaining six cats no deficits were apparent seven days later. The cerbral infarcts regularly involved the basal ganglia, internal capsule, and cortical regions, and were larger and less variable than those produced by MCA occlusion through and open optic foramen or craniectomy with cranial decompression by drainage of CSF. This model of acute focal cerebral ischemia may be of value for studies of physiological and biochemical factors uninfluenced by sedatives, anesthesia, or recent surgical procedures.

Effects of dexamethasone on distributions of water and pertechnetate in brains of cats after middle cerebral artery occlusion

Large parenteral doses of dexamethasone were given to five of ten cats after transorbital occlusion of one middle cerebral artery and to two of four cats after sham operations. Two days later the water content and brain/blood ratios of pertechnetate were measured in samples of cerebral tissue that were categorized as nonischemic, ischemic, or infarcted. Values for infarcted tissue were greater than those for ischemic tissue in untreated cats, but not in cats that received dexamethasone. The drug had no apparent effect in ischemic tissue that was not necrotic. These results help explain inconsistencies in previous studies and help define the potential usefulness of dexamethasone for treatment of cerebrovascular disease.