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Objective: CD44 is a major cell surface receptor involved in cell adhesion and migration. The overexpression of CD44 is a poor prognostic factor in many neoplasms, including meningiomas. The aim of this study was to investigate the association between CD44 gene expression and clinical signatures of primary meningiomas., Methods: CD44 gene expression was quantitatively evaluated by snap freezing tumor tissues obtained from 106 patients with primary meningioma. The relationships between CD44 expression and clinical signatures of meningiomas, including histological malignancy, tumor volume, and peritumoral brain edema (PTBE), were analyzed. PTBE was assessed using the Steinhoff classification (SC) system (from SC 0 to SC III)., Results: CD44 gene expression in WHO grade 2 and 3 meningiomas was significantly higher than that in grade 1 meningiomas. In addition, CD44 expression increased with the severity of PTBE. Particularly, among the grade 1 meningiomas or small-sized tumors (maximum tumor diameter < 43 mm), CD44 expression in tumors with severe PTBE (SC II or III) was significantly higher than that in tumors without or with mild PTBE (SC 0 or I). Multivariate logistic regression analysis also revealed that overexpression of CD44 was an independent significant factor of severe PTBE development in primary meningiomas., Conclusions: In addition to tumor cell aggressiveness, CD44 expression promotes the development of PTBE in meningioma. Since PTBE is a strong factor of tumor-related epilepsy or cognitive dysfunction in patients with meningioma, CD44 is thus a potential therapeutic target in meningioma with PTBE.

Objective: Brain abscesses could lead to cerebral symptoms through tissue destruction, edema, changes in brain architecture, and increased intracranial pressure. However, the possibility that the pus itself could contribute to symptoms has received little attention. Brain abscesses are areas of tissue destruction, proteolysis, and formation of free amino acids, which are energy substrates for bacteria and possible sources of ammonia. Ammonia is neurotoxic, may cause brain edema, and could contribute to the symptoms of brain abscesses., Methods: The authors analyzed the extracellular phase of pus from 14 patients with brain abscesses with respect to ammonia and amino acids. For comparison, CSF from 10 patients undergoing external ventricular drainage was included. The ammonia-forming ability of Streptococcus intermedius and Staphylococcus aureus, two common microbial isolates in brain abscesses, was studied in vitro., Results: In brain abscesses ammonia was 15.5 mmol/L (median value; range 1.7-69.2 mmol/L). In CSF ammonia was 29 μmol/L (range 17-55 μmol/L; difference from value in pus: p < 0.001). The total concentration of amino acids in brain abscesses was 1.12-16 times higher than the ammonia concentration (p = 0.011). The median glucose value in pus was 0 mmol/L (range 0-2.1 mmol/L), lactate was 21 mmol/L (range 3.3-26.5 mmol/L), and pH was 6.8 (range 6.2-7.3). In vitro, S. intermedius and S. aureus formed ammonia at 6-7 mmol/L in 24 hours when incubated with 20 proteinogenic amino acids plus g-aminobutyric acid (GABA), taurine, and glutathione at 1 mmol/L., Conclusions: Intracerebral abscesses contain toxic levels of ammonia. At the concentrations found in pus, ammonia could contribute to the brain edema and the symptoms of brain abscesses.

Object: Peritumoral brain edema (PTBE) is a common phenomenon associated with high-grade gliomas (HGGs). In this study, the authors investigated the expression of Notch delta-like ligand 4 (DLL4) and its correlation with PTBE and prognosis in patients with an HGG., Methods: Tumors from 99 patients with HGG were analyzed for DLL4 expression using immunohistochemistry. PTBE on preoperative MR images and the relationship between PTBE and DLL4 expression were evaluated. The effect of DLL4 on patient prognosis was assessed by using Kaplan-Meier survival and Cox proportional hazard models., Results: Immunohistochemistry results revealed that the expression of DLL4 was distributed primarily within the cytoplasm of tumor vascular endothelial cells and seldom detected in tumor cells. DLL4 expression was correlated positively with the degree of edema (r = 0.845 and p < 0.001, Spearman's test). In addition, DLL4 was an independent predictor of prognosis in patients with HGGs (p = 0.001)., Conclusions: DLL4 expression was correlated positively with the degree of PTBE and was an independent unfavorable prognostic indicator in patients with HGG.

Object: Previous studies have demonstrated that traumatic brain injury (TBI) causes brain edema by allowing excessive water passage through aquaporin (AQP) proteins. To establish the potential neuroprotective properties of ethanol as a post-TBI therapy, in the present study the authors determined the effect of ethanol on brain edema, AQP expression, and functional outcomes in a post-TBI setting., Methods: Adult male Sprague-Dawley rats weighing between 425 and 475 g received a closed head TBI in which Maramarou's impact-acceleration method was used. Animals were given a subsequent intraperitoneal injection of 0.5 g/kg or 1.5 g/kg ethanol at 60 minutes post-TBI and were killed 24 hours after TBI. Brains were subsequently examined for edema along with AQP mRNA and protein expression. Additional animals treated with either 0.5 g/kg or 1.5 g/kg ethanol at 60 minutes post-TBI were designated for cognitive and motor testing for 3 weeks., Results: Ethanol administration post-TBI led to significantly (p < 0.05) lower levels of brain edema as measured by brain water content. This downregulation in brain edema was associated with significantly (p < 0.05) reduced levels of AQP mRNA and protein expression as compared with TBI without treatment. These findings concur with cognitive studies in which ethanol-treated animals exhibited significantly (p < 0.05) faster radial maze completion times. Motor behavioral testing additionally demonstrated significant (p < 0.05) beneficial effects of ethanol, with treated animals displaying improved motor coordination when compared with untreated animals., Conclusions: The present findings suggest that acute ethanol administration after a TBI decreases AQP expression, which may lead to reduced cerebral edema. Ethanol-treated animals additionally showed improved cognitive and motor outcomes compared with untreated animals.

Object: Intracranial surgery causes cortical injury from incisions, hemorrhage, retraction, and electrocautery. The term "surgical brain injury" (SBI) has been developed to categorize this injury inherent to the procedure. Neuroinflammation plays a significant role in SBI. Traditional antiinflammatory therapies are often limited by their immunosuppressive side effects and poor CNS penetration. This study uses mucosal tolerance to develop an immune system that is tolerant to brain myelin basic protein (MBP) so that inflammation can be suppressed in a timely and site-specific manner following surgical disruption of the blood-brain barrier., Methods: A standard SBI model using CD57 mice was used. Nasopharyngeal mucosa was exposed to vehicle, ovalbumin, or MBP to develop mucosal tolerance to these antigens. Immunological tolerance to MBP was confirmed in vivo through hypersensitivity testing. Neurological scores, cerebral edema, and interleukin (IL)-1β and transforming growth factor (TGF)-β1 cytokine levels were measured 48 hours postoperatively., Results: Hypersensitivity testing confirmed the development of immune tolerance to MBP. Myelin basic protein-tolerant mice demonstrated reduced neurological injury, less cerebral edema, decreased levels of IL-1β, and increased levels of TGFβ1 following SBI., Conclusions: Developing preoperative immunological tolerance to brain antigens through mucosal tolerance provides neuroprotection, reduces brain edema, and modulates neuroinflammation following SBI.

Object: Hypertension is the main cause of spontaneous intracerebral hemorrhages (ICHs), but the effects of hypertension on ICH-induced brain injury have not been well studied. In this study, the authors examined ICH-induced brain injury in spontaneously hypertensive rats (SHRs)., Methods: This 2-part study was performed in 12-week-old male SHRs and Wistar Kyoto (WKY) rats. First, the rats received an intracaudate injection of 0.3 U collagenase, and hematoma sizes were determined at 24 hours. Second, rats were injected with 100 μl autologous whole blood into the right basal ganglia. Brain edema, neuronal death, ferritin expression, microglia activation, and neurological deficits were examined., Results: Hematoma sizes were the same in SHR and WKY rats 24 hours after collagenase injection. The SHRs had greater neuronal death and neurological deficits after blood injection. Intracerebral hemorrhage also resulted in higher brain ferritin levels and stronger activation of microglia in SHRs. However, perihematomal brain edema was the same in the SHRs and WKY rats., Conclusions: Moderate chronic hypertension resulted in more severe ICH-induced neuronal death and neurological deficits, but did not exaggerate hematoma enlargement and perihematomal brain edema in the rat ICH models.

Object: The present study investigated the role of hypoxia-inducible factor-1α (HIF-1α), aquaporin-4 (AQP-4), and matrix metalloproteinase-9 (MMP-9) in blood-brain barrier (BBB) permeability alterations and brain edema formation in a rodent traumatic brain injury (TBI) model., Methods: The brains of adult male Sprague-Dawley rats (400-425 g) were injured using the Marmarou closed-head force impact model. Anti-AQP-4 antibody, minocycline (an inhibitor of MMP-9), or 2-methoxyestradiol (2ME2, an inhibitor of HIF-1α), was administered intravenously 30 minutes after injury. The rats were killed 24 hours after injury and their brains were examined for protein expression, BBB permeability, and brain edema. Expression of HIF-1α, AQP-4, and MMP-9 as well as expression of the vascular basal lamina protein (laminin) and tight junction proteins (zona occludens-1 and occludin) was determined by Western blotting. Blood-brain barrier disruption was assessed by FITC-dextran extravasation, and brain edema was measured by the brain water content., Results: Significant (p < 0.05) edema and BBB extravasations were observed following TBI induction. Compared with sham-operated controls, the injured animals were found to have significantly (p < 0.05) enhanced expression of HIF-1α, AQP-4, and MMP-9, in addition to reduced amounts (p < 0.05) of laminin and tight junction proteins. Edema was significantly (p < 0.01) decreased after inhibition of AQP-4, MMP-9, or HIF-1α. While BBB permeability was significantly (p < 0.01) ameliorated after inhibition of either HIF-1α or MMP-9, it was not affected following inhibition of AQP-4. Inhibition of MMP reversed the loss of laminin (p < 0.01). Finally, while inhibition of HIF-1α significantly (p < 0.05) suppressed the expression of AQP-4 and MMP-9, such inhibition significantly (p < 0.05) increased the expression of laminin and tight junction proteins., Conclusions: The data support the notion that HIF-1α plays a role in brain edema formation and BBB disruption via a molecular pathway cascade involving AQP-4 and MMP-9. Pharmacological blockade of this pathway in patients with TBI may provide a novel therapeutic strategy.

Object: Peritumoral brain edema (PTBE) is associated with perioperative neurological deficits in patients with meningiomas. However, the pathogenesis of meningioma-associated edema remains unclear. In the present study, the authors investigated the expression of interleukin-6 (IL-6) and its relationship with PTBE in resected meningiomas., Methods: Thirty-six benign meningiomas obtained in 36 patients were studied retrospectively. Edema volume was assessed on MR images, and an edema index (EI) was calculated. Interleukin-6 mRNA and protein expression were examined by real-time reverse transcriptase polymerase chain reaction and immunohistochemical staining., Results: Peritumoral brain edema was found in 16 patients (44%). Neither age, sex, histological subtype, nor tumor location were related to PTBE. The level of IL-6 mRNA was 7.72 times greater in the edema group (EI > 0.2) than in the nonedema group (EI < 0.2; p = 0.011). On immunohistochemical analysis, IL-6 protein was found localized in the cytoplasm of the tumor cells, and was detected in 12 (75%) of 16 cases of edematous meningiomas, but in only 6 (30%) of 20 nonedematous cases. There was a significant correlation between the severity of PTBE and IL-6 expression (p = 0.004)., Conclusions: The authors' results in this study indicate that IL-6 expression may contribute to the development of brain edema associated with meningiomas.

Object: A relationship has been found between peripheral thermal injury and cerebral complications leading to injury and death. In the present study, the authors examined whether tumor necrosis factor-alpha (TNF-alpha) and matrix metalloproteinase-9 (MMP-9) play a causative role in blood-brain barrier (BBB) disruption after peripheral thermal injury., Methods: Thirty-two male Sprague-Dawley rats were subjected to thermal injury. One hour later, 8 rats were injected with TNF-alpha neutralizing antibody, and 8 were injected with doxycycline, an inhibitor of the MMP family proteins; 16 rats did not receive any treatment. Brain tissue samples obtained 7 hours after injury in the treated animals were examined for BBB function by using fluorescein isothiocyanate-dextran and by assessing parenchymal water content. Protein expression of basement membrane components (collagen IV, laminin, and fibronectin) was quantified on Western blot analysis, and MMP-9 protein expression and enzyme activity were determined using Western blot and gelatin zymography. Thermally injured rats that did not receive treatment were killed at 3, 7, or 24 hours after injury and tested for BBB functioning at each time point. Histological analysis for basement membrane proteins was also conducted in untreated rats killed at 7 hours after injury. Results of testing in injured rats were compared with those obtained in a control group of rats that did not undergo thermal injury., Results: At 7 hours after thermal injury, a significant increase in the fluorescein isothiocyanate-dextran and water content of the brain was found (p < 0.05), but BBB dysfunction was significantly decreased in the rats that received TNF-alpha antibody or doxycycline (p < 0.05). In addition, the components of the basal lamina were significantly decreased at 7 hours after thermal injury (p < 0.01), and there were significant increases in MMP-9 protein expression and enzyme activity (p < 0.05). The basal lamina damage was reversed by inhibition of TNF-alpha and MMP-9, and the increase in MMP-9 protein was reduced in the presence of doxycycline (p < 0.05). The authors found that MMP-9 enzyme activity was significantly increased after thermal injury (p < 0.01) but decreased in the presence of either TNF-alpha antibody or doxycycline (p < 0.01)., Conclusions: The dual, inhibitory activity of both TNF-alpha and MMP-9 in brain injury suggests that a TNF-alpha and MMP-9 cascade may play a key role in BBB disruption. These results offer a better understanding of the pathophysiology of burn injuries, which may open new avenues for burn treatment beyond the level of current therapies.

Object: Brain edema formation following intracerebral hemorrhage (ICH) appears to be partly related to erythrocyte lysis and hemoglobin release. An increase of brain water content was associated with an increase of brain iron, which is an erythrocyte degradation product. Expression of AQP4 is highly modified in several brain disorders, and it can play a key role in cerebral edema formation. However, the question whether AQP4 is regulated by drugs lacks reliable evidence, and the interacting roles of iron overload and AQP4 in brain edema after ICH are unknown. The goal of this study was to clarify the relationship between iron overload and AQP4 expression and to characterize the effects of the iron chelator deferoxamine (DFO) on delayed brain edema after experimental ICH., Methods: A total of 144 Sprague-Dawley rats weighing between 250 and 300 g were used in this work. The animals were randomly divided into 4 groups. The ICH models (Group C) were generated by injecting 100 microl autologous blood stereotactically into the right caudate nucleus; surgical control rats (Group B) were generated in a similar fashion, by injecting 100 microl saline into the right caudate nucleus. Intervention models (Group D) were established by intraperitoneal injection of DFO into rats in the ICH group. Healthy rats (Group A) were used for normal control models. Brain water content, iron deposition, and AQP4 in perihematomal brain tissue were evaluated over the time course of the study (1, 3, 7, and 14 days) in each group., Results: Iron deposition was found in the perihematomal zone as early as the 1st day after ICH, reaching a peak after 7 days and remaining at a high level thereafter for at least 14 days following ICH. Rat brain water content around the hematoma increased progressively over the time course, reached its peak at Day 3, and still was evident at Day 7 post-ICH. Immunohistochemical analysis showed that AQP4 was richly expressed over glial cell processes surrounding microvessels in the rat brain; there was upregulation of the AQP4 expression in perihematomal brain during the observation period, and it reached maximum at 3 to 7 days after ICH. The changes of brain water content were accompanied by an alteration of AQP4. The application of the iron chelator DFO significantly reduced iron overload, brain water content, and AQP4 level in the perihematomal area compared with the control group., Conclusions: Iron overload and AQP4 may play a critical role in the formation of brain edema after ICH. In addition, AQP4 expression was affected by iron concentration. Importantly, treatment with DFO significantly reduced brain edema in rats and inhibited the AQP4 upregulation after ICH. Deferoxamine may be a potential therapeutic agent for treating ICH.

Object: This study was undertaken to determine if dialysis of damaged brain surface can reduce cerebrospinal fluid (CSF) pressure and progressive brain edema. The authors secondarily determined if local brain cooling was simultaneously possible., Methods: Telemetric pressure transmitters were implanted into the lumbar subarachnoid space of 58 young adult male rats. Cryogenic brain injury was created and 2 hours later decompressive craniectomy was performed. An osmotic cell with a semipermeable dialysis membrane placed on the damaged brain surface was perfused with dextran 15% solution for 2 or 4 hours. Water content was determined in the cerebral hemispheres using the wet-dry weight method. Evans blue-albumin spread was measured morphometrically. Brain temperature was measured bilaterally., Results: The CSF pressure increased after cryogenic injury and decreased after craniotomy. Two hours of brain dialysis significantly reduced CSF pressure in comparison with craniotomy alone and sham dialysis. Injured brain had higher water content, but this was not affected by dialysis. Spread of Evans blue-albumin, however, was significantly reduced by the treatment. Cooling of the dialysis solution caused significant local brain cooling., Conclusions: Surface dialysis of cryogenically injured rat brain controls CSF pressure and reduces intraparenchymal spread of edema fluid in the acute period after injury. The authors postulate that edema fluid moves into the osmotic cell rather than spreading through the uninjured brain. Long-term experiments will be needed to prove that this combination therapy is effective.

Object: The authors of previous studies based on diffusion tensor imaging have indicated that there are two types of peritumoral edema-namely, edema with preserved structural integrity of the glial matrix and edema with compromised glial matrix. The authors of this study hypothesized that functionality of the glutamate (Glu)-glutamine shuttle, a vital neuron-glia interaction, may be differentially affected by peritumoral edema. They tested this hypothesis using proton magnetic resonance (MR) spectroscopy on a 3.0-tesla system that is capable of quantifying Glu without need of editing., Methods: Twenty-three patients, each with a single brain tumor mass and peritumoral edema (nine high-grade gliomas, eight metastatic brain tumors, and six meningiomas), and nine healthy individuals participated in this study. Single-voxel proton MR imaging targeting the region of peritumoral edema was performed using a 3.0-tesla system. Glutamate levels in the peritumoral edema of nonglial tumors was significantly elevated (p < 0.01) compared with edema associated with glial tumors or normal white matter. The finding confirmed that peritumoral edema in nonglial tumors is distinct from that of glial tumors, as previously indicated in diffusion tensor imaging studies. The authors hypothesized that the former condition represents a compensatory increase in activities of the Glu-glutamine shuttle brought about by simple expansion of the extracellular space due to edema., Conclusions: The assessment of Glu concentrations in peritumoral edema using 3.0-tesla proton MR spectroscopy may be developed into an objective index of the structural integrity of the glial matrix.

Object: The aims of this study were to determine the following: whether there are sex differences in intracerebral hemorrhage (ICH) induced brain injury in rats, whether delayed administration of 17beta-estradiol can reduce ICH-induced brain damage, and whether these effects are estrogen receptor (ER)-dependent., Methods: Male and female Sprague-Dawley rats received an infusion of 100 microl autologous whole blood into the right basal ganglia. Twenty-four hours later the rats were killed. The effects of 17beta-estradiol on ICH-induced brain injury were examined by measuring brain edema and neurological deficits. Both ER-alpha and hemeoxygenase (HO)-1 were investigated through Western blot and immunohistochemical analysis. Brain edema was significantly less severe in female compared with that in male rats. The ER antagonist ICI 182,780 exacerbated ICH-induced brain edema in female but not in male rats, indicating that ER-alpha activation during ICH is protective in female rats. Administration of exogenous 17beta-estradiol in male, but not in female, rats significantly attenuated brain edema, neurological deficits, and ICH-induced changes in HO-1 when given 2 hours after hemorrhage. The effects of exogenous 17beta-estradiol occurred through an ER-independent mechanism., Conclusions: Results in this study indicate that 17beta-estradiol could be a potential therapeutic agent for ICH.

Object: Aquaporin-4 (AQP4) plays a significant role in the regulation of brain water homeostasis. In this study the authors investigated the regulation of AQP4 following a focal cortical contusion injury in rats., Methods: Thirty-three adult male Wistar rats received a focal cortical contusion of the parietal cortex. An additional nine rats underwent a craniectomy, but no trauma was inflicted (sham injury). Animals were killed 1, 4, and 24 hours later. The rat brains were examined for water content by comparing the wet and dry weights of each hemisphere. Aquaporin-4 messenger (m)RNA was measured by reverse transcription-polymerase chain reaction. A ratio of AQP4 mRNA expression in the lesioned hemisphere compared with that in the contralateral control hemisphere was calculated for each animal at the injury site (parietal cortex) and at sites adjacent to (occipital cortex) and distant from the injury (frontal pole cortex). Brain edema was significantly increased at the injury site. The expression of AQP4 mRNA was significantly increased at the injury site, significantly decreased adjacent to the injury site, and not significantly different at a site distant from the injury. The magnitude of AQP4 mRNA upregulation at the injured parietal cortex correlated with the degree of downregulation in the adjacent occipital cortex., Conclusions: Data from this study demonstrate that an upregulation of AQP4 occurs at the site of traumatic brain injury and that a downregulation of this molecule occurs adjacent to the site of injury. Understanding the physiology of AQP4 and its regulation following brain injury may allow for the development of novel treatments for cerebral edema that accompanies head injury.

Object: Identification of new therapeutic agents aimed at attenuating posttraumatic brain edema formation remains an unresolved challenge. Among others, activation of bradykinin B2 receptors is known to mediate the formation of brain edema. The purpose of this study was to investigate the protective effect of the novel nonpeptide B2 receptor antagonist, LF 16-0687Ms, in brain-injured rats., Methods: Focal contusion was produced by controlled cortical impact injury. Five minutes after trauma, the rats received a single dose of no, low- (3 mg/kg body weight), or high- (30 mg/kg) dose LF 16-0687Ms. After 24 hours, the amount of brain swelling and hemispheric water content were determined. Low and high doses of LF 16-0687Ms significantly reduced brain swelling by 25% and 27%, respectively (p < 0.03). Hemispheric water content tended to be increased in the nontraumatized hemisphere. In a subsequent series of 10 rats, cisternal cerebrospinal fluid (CSF) samples were collected to determine whether changes in substances associated with edema formation could clarify why LF 16-0687Ms increases water content. For this, the volume regulator amino acid taurine, the excitatory transmitter glutamate, and the adenosine triphosphate degradation products hypoxanthine and xanthine were measured. In CSF, the levels of taurine, hypoxanthine, and xanthine were significantly decreased following a single administration of LF 16-0687Ms (p < 0.005); the level of glutamate, however, was double that found in control animals (p < 0.05)., Conclusions: Using the present study design, a single administration of LF 16-0687Ms successfully reduced posttraumatic brain swelling. The decreased levels of taurine, hypoxanthine, and xanthine may reflect reduced posttraumatic brain edema, whereas the increased level of glutamate could account for the elevated water content observed in the nontraumatized hemisphere.

Object: The proinflammatory cytokines interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNFalpha) are produced intracerebrally in brain disorders such as trauma, ischemia, meningitis, and multiple sclerosis. This investigation was undertaken to analyze the effect of intracerebral administration of IL-1beta and TNFalpha on inflammatory response, cell death, and edema development., Methods: Intracerebral microinjections of these cytokines were administered to rats. The animals were killed 24 or 72 hours after the injections, and their brains were analyzed by using deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) with digoxigenin-labeled deoxyuridine triphosphate, immunohistochemical studies, and brain-specific gravity measurement. The IL-1beta induced a transient inflammatory response (p < 0.001) and TUNEL staining (p < 0.001), indicating cell death, in intrinsic central nervous system (CNS) cells and infiltrating inflammatory cells. In 73.8+/-6.77% of the TUNEL-positive cells, small, fragmented nuclei were found. All TUNEL-positive cells expressed the proapoptotic gene Bax, and 69.6+/-4.6% of the TUNEL-positive cells expressed the antiapoptotic gene Bcl-2; the Bax expression was stronger than the Bcl-2 expression. Taken together, the data indicate that cell death occurred via the apoptotic pathway. The TNFalpha did not induce inflammation or DNA fragmentation within the analyzed time period. Both IL-1beta (p < 0.001) and TNFalpha (p < 0.01) caused vasogenic edema, as measured by specific gravity and albumin staining. The edematous effect of TNFalpha persisted 72 hours after injection (p < 0.01), whereas the IL-1beta-treated animals had normalized by that time., Conclusions: Intracerebral inflammation, death of intrinsic CNS cells, and vasogenic edema can be mediated by IL-1beta, and TNFalpha can cause vasogenic edema. Suppression of these cytokines in the clinical setting may improve outcome.

Object: The authors examined the correlation between changes in the apparent diffusion coefficient, regional water content, and tissue ultrastructure after vasogenic brain edema., Methods: Vasogenic edema was induced in the white matter of six cats by cortical cold lesioning. The trace of diffusion tensor (Trace[D]) obtained from magnetic resonance imaging to measure the orientationally averaged water diffusibility was compared with the corresponding tissue water content determined by gravimetric studies and with ultrastructural water localization. Edema fluid had spread to the subcortical and deep white matter by 4.5 hours postlesioning. The increase in Trace(D) showed a significant linear correlation with the increase in tissue water content, both in the subcortical and deep white matter as follows: y = 45.5x - 2367 (r = 0.94) and y = 37.0x - 1769 (r = 0.93), respectively, where x is the water content (gram water/gram tissue) and y the Trace(D) (x 10(-6) mm2/second). On histological examination, nerve fibers were found to be dissociated in the white matter and the extracellular space was markedly enlarged with protein-rich fluid. No noticeable hydropic swelling of the cellular components was observed., Conclusions: A linear correlation was observed between increases in Trace(D) and increases in extracellular water volume in in vivo vasogenic brain edema. A similar correlation between the subcortical and deep white matter showing different arrangements of nerve fibers (parallel compared with intermingled, respectively) indicated that measurement of Trace(D) is a suitable parameter for the evaluation of vasogenic brain edema.

Object: The authors present a quantitative in vivo magnetic resonance (MR) imaging method and propose its use for the accurate assessment of brain water in humans., Methods: With this technique, a pure T1-weighted image of a selected brain slice in a patient is generated, and the image is subsequently converted to a pure water image by means of an equation derived from a tissue relaxation model. The image intensity in the resulting water map directly yields absolute measures of water expressed in grams of water per gram of tissue at a given anatomical location. The method has been validated previously in a series of phantom experiments and in an infusion model of brain edema in cats. In this report, the authors evaluate the method by using samples of tissue harvested from patients who underwent surgery for brain tumor removal and apply the technique to a series of normal volunteers, providing average regional brain water content (f(w)) values for a range of tissues. Application of the method in pathological conditions such as head trauma, tumor, and hydrocephalus allows quantification of regional or global increases in f(w) that result from edema., Conclusions: It is now possible to obtain accurate brain water measurements with the anatomical resolution of MR imaging. This permits monitoring of the development and resolution of edema in a variety of clinical circumstances, thus enhancing understanding of the underlying pathophysiological processes.

Object: The authors previously demonstrated, in a large-animal intracerebral hemorrhage (ICH) model, that markedly edematous ("translucent") white matter regions (> 10% increases in water contents) containing high levels of clot-derived plasma proteins rapidly develop adjacent to hematomas. The goal of the present study was to determine the concentrations of high-energy phosphate, carbohydrate substrate, and lactate in these and other perihematomal white and gray matter regions during the early hours following experimental ICH., Methods: The authors infused autologous blood (1.7 ml) into frontal lobe white matter in a physiologically controlled model in pigs (weighing approximately 7 kg each) and froze their brains in situ at 1, 3, 5, or 8 hours postinfusion. Adenosine triphosphate (ATP), phosphocreatine (PCr), glycogen, glucose, lactate, and water contents were then measured in white and gray matter located ipsi- and contralateral to the hematomas, and metabolite concentrations in edematous brain regions were corrected for dilution. In markedly edematous white matter, glycogen and glucose concentrations increased two- to fivefold compared with control during 8 hours postinfusion. Similarly, PCr levels increased several-fold by 5 hours, whereas, except for a moderate decrease at 1 hour, ATP remained unchanged. Lactate was markedly increased (approximately 20 micromol/g) at all times. In gyral gray matter overlying the hematoma, water contents and glycogen levels were significantly increased at 5 and 8 hours, whereas lactate levels were increased two- to fourfold at all times., Conclusions: These results, which demonstrate normal to increased high-energy phosphate and carbohydrate substrate concentrations in edematous perihematomal regions during the early hours following ICH, are qualitatively similar to findings in other brain injury models in which a reduction in metabolic rate develops. Because an energy deficit is not present, lactate accumulation in edematous white matter is not caused by stimulated anaerobic glycolysis. Instead, because glutamate concentrations in the blood entering the brain's extracellular space during ICH are several-fold higher than normal levels, the authors speculate, on the basis of work reported by Pellerin and Magistretti, that glutamate uptake by astrocytes leads to enhanced aerobic glycolysis and lactate is generated at a rate that exceeds utilization.

Object: The authors sought to determine whether 3,3-bis (3-fluorophenyl) propylamine (NPS 846), a novel noncompetitive N-methyl-D-aspartate receptor antagonist, alters outcome after closed head trauma in rats., Methods: The experimental variables were: presence or absence of closed head trauma, treatment with NPS 846 or no treatment, and time at which the rats were killed (24 or 48 hours). The NPS 846 (1 mg/kg) was administered intraperitoneally at 1 and 3 hours after closed head trauma or sham operation. Outcome measures were the neurological severity score (NSS), ischemic tissue volume, hemorrhagic necrosis volume, and specific gravity, water content, and concentrations of calcium, sodium, potassium, and magnesium in brain tissue. The following closed head trauma-induced changes in the injured hemisphere (expressed as the mean +/- the standard deviation) were reversed by NPS 846: decreased specific gravity of 1.035 +/- 0.006 at 24 hours was increased to 1.042 +/- 0.004; the decreased potassium level of 0.583 +/- 0.231 mg/L at 48 hours and at 24 hours was increased to 2.442 +/- 0.860 mg/L; the increased water content of 84.7 +/- 2.6% at 24 hours was decreased to 79.8 +/- 2%; the increased calcium level of 0.592 +/- 0.210 mg/L at 24 hours was decreased to 0.048 +/- 0.029 mg/L; and the increased sodium level of 2.035 +/- 0.649 mg/L was decreased to 0.631 +/- 0.102 mg/L. Administration of NPS 846 also lowered the NSS (improved neurological status) at 48 hours (7 +/- 3) and caused no significant changes in ischemic tissue or hemorrhagic necrosis volumes in the injured hemisphere at 24 or 48 hours., Conclusions: In this model of closed head trauma, NPS 846 improved neurological outcome, delayed the onset of brain edema, and improved brain tissue ion homeostasis.

Object: The purpose of this study was to evaluate the involvement of platelet-activating factor (PAF) in the formation of edema surrounding meningiomas., Methods: Volumes of tumor and peritumoral edema were calculated based on three-dimensional reconstructed magnetic resonance images in 31 patients with intracranial meningiomas. The authors measured tumor concentrations of PAF and localized PAF and leukocytes in the tumors by using immunohistochemical studies. A significant positive correlation was found between peritumoral edema and PAF concentration. Both PAF and leukocyte common antigen were localized to the interstitial tissue of the tumor. Edema production was related to the degree of leukocyte infiltration in meningiomas., Conclusions: It appears that PAF, which may arise from infiltrating leukocytes, is important to the development of peritumoral edema in patients with meningioma.

Polyamines and N-methyl-D-aspartate (NMDA) receptors are both thought to play an important role in secondary neuronal injury after cerebral ischemia. Ifenprodil, known as a noncompetitive inhibitor of polyamine sites at the NMDA receptor, was studied after transient focal cerebral ischemia occurred. Spontaneously hypertensive male rats, each weighing between 250 and 350 g, underwent 3 hours of tandem middle cerebral artery (MCA) and common carotid artery occlusion followed by reperfusion for a period of 3 hours or 21 hours. Intravenous ifenprodil (10 microg/kg/minute) or saline infusion was started immediately after the onset of MCA occlusion and continued throughout the ischemic period. Physiological parameters including blood pressure, blood gas levels, blood glucose, hemoglobin, and rectal and temporal muscle temperatures were monitored. Six rats from each group were evaluated at 6 hours postocclusion for brain water content, an indicator of brain edema, and Evans blue dye extravasation for blood-brain barrier breakdown. Infarct volume was also measured in six rats from each group at 6 and 24 hours postocclusion. Ifenprodil treatment significantly reduced brain edema (82.5 +/- 0.4% vs. 83.5 +/- 0.4%, p < 0.05) and infarct volume (132 +/- 14 mm3 vs. 168 +/- 25 mm3, p < 0.05) compared with saline treatment, with no alterations in temporal muscle (brain) or rectal (body) temperature (35.9 +/- 0.4 degrees C vs. 36.2 +/- 0.2 degrees C; 37.7 +/- 0.4 degrees C vs. 37.6 +/- 0.6 degrees C; not significant). These results demonstrate that ifenprodil has neuroprotective properties after ischemia/reperfusion injury in the absence of hypothermia. This indicates that antagonists selective for the polyamine site of the NMDA receptors may be a viable treatment option and helps to explain some of the pathophysiological mechanisms involved in secondary injury after transient focal cerebral ischemia has occurred.

The contribution of brain edema to brain swelling in cases of traumatic brain injury remains a critical problem. The authors believe that cellular edema, the result of complex neurotoxic events, is the major contributor to brain swelling and that vasogenic edema, secondary to blood-brain barrier compromise, may be overemphasized. The objective of this study, therefore, was to quantify temporal water content changes and document the type of edema that forms during the acute and late stages of edema development following closed head injury (CHI). The measurement of brain water content was based on magnetic resonance imaging-determined values of tissue longitudinal relaxation time (T1-weighted imaging) and their subsequent conversion to percentage of water, whereas the differentiation of edema formation (cellular vs. vasogenic) was based on the measurement of the apparent diffusion coefficient (ADC) by diffusion-weighted imaging. A new impact-acceleration model was used to induce CHI. Thirty-six adult Sprague-Dawley rats were separated into two groups: Group I, control (six animals); and Group II, trauma (30 animals). Fast ADC measurements (localized, single-voxel) were obtained sequentially (every minute) up to 1 hour postinjury. The T1-weighted images, used for water content determination, and the diffusion-weighted images (ADC measurement with conventional diffusion-weighted imaging) were obtained at the end of the 1st hour postinjury and on Days 1, 3, 7, 14, 28, and 42 in animals from the trauma and control groups. In the animals subjected to trauma, the authors found a significant increase in ADC (10 +/- 5%) and brain water content (1.3 +/- 0.9%) during the first 60 minutes postinjury. This is consistent with an increase in the volume of extracellular fluid and vasogenic edema formation as a result of blood-brain barrier compromise. This transient increase, however, was followed by a continuing decrease in ADC that began 40 to 60 minutes postinjury and reached a minimum value on Days 7 to 14 (10 +/- 3% reduction). Because the water content of the brain continued to increase during the first 24 hours postinjury (1.9 +/- 0.9%), it is suggested that the decreased ADC indicated cellular edema formation, which started to develop soon after injury and became dominant between 1 and 2 weeks postinjury. The study provides supportive evidence that cellular edema is the major contributor to posttraumatic swelling in diffuse CHI and defines the onset and duration of the increase in cellular volume.

Proinflammatory cytokines mediate brain injury in experimental studies. This study was undertaken to analyze the production of proinflammatory cytokines in experimental contusion. A brain contusion causing delayed edema was mimicked experimentally in rats using a weight-drop model. Intracerebral expression of the cytokines interleukin (IL)-1 beta, tumor necrosis factor-alpha (TNF alpha), IL-6, and interferon-gamma (IFN gamma) was studied by in situ hybridization and immunohistochemistry. The animals were killed at 6 hours or 1, 2, 4, 6, 8, or 16 days postinjury. In the injured area, no messenger (m)RNA expression was seen during the first 2 days after the trauma. On Days 4 to 6 posttrauma, however, strong IL-1 beta, TNF alpha, and IL-6 mRNA expression was detected in mononuclear cells surrounding the contusion. Expression of IFN gamma was not detected. Immunohistochemical double labeling confirmed the in situ hybridization results and demonstrated that mononuclear phagocytes and astrocytes produced IL-1 beta and that mainly astrocytes produced TNF alpha. The findings showed, somewhat unexpectedly, a late peak of intracerebral cytokine production in the injured area and in the contralateral corpus callosum, allowing for both local and global effects on the brain. An unexpected difference in the cellular sources of TNF alpha and IL-1 beta was detected. The cytokine pattern differs from that seen in other central nervous system inflammatory diseases and trauma models, suggesting that the intracerebral immune response is not a uniform event. The dominance of late cytokine production indicates that many cytokine effects are late events in an experimental contusion: Different pathogenic mechanisms may thus be operative at different times after brain injury.

Purified thrombin from an exogenous source is a hemostatic agent commonly used in neurosurgical procedures. The toxicity of thrombin in the brain, however, has not been examined. This study was performed to assess the effect of thrombin on brain parenchyma, using the formation of brain edema as an indicator of injury. Ten microliters of test solution was infused stereotactically into the right basal ganglia of rats. The animals were sacrificed 24 hours later, and the extent of brain edema and ion content were measured. Concentrations of human thrombin as low as 1 U/microliter resulted in a significant increase in brain water content. Rats receiving 10 U/microliters had a mortality rate of 33% compared to no mortality in the groups receiving smaller doses. Thrombin-induced brain edema was inhibited by a specific and potent thrombin inhibitor, hirudin. A medical grade of bovine thrombin commonly used in surgery also caused brain edema when injected at a concentration of 2 U/microliters. Edema formation was prevented by another highly specific thrombin inhibitor, N alpha-(2-Naphthalenesulfonylglycyl)-4-DL-phenylalaninepiperidid e (alpha-NAPAP). Thrombin-induced brain edema was accompanied by increases in brain sodium and chloride contents and a decrease in brain potassium content. Changes in brain ions were inhibited by both hirudin and alpha-NAPAP, corresponding to the inhibition of brain water accumulation. This study shows that thrombin causes brain edema when infused into the brain at concentrations as low as 1 U/microliter, an amount within the range of concentrations used for topical hemostasis in neurosurgery.

Peritumoral vasogenic brain edema (PVBE) is a common accompaniment of malignant gliomas. It results from microvascular extravasation of plasma fluid and proteins through the interendothelial spaces. Tumor-associated cysts (TACs) are observed more commonly with benign gliomas that are not associated with PVBE. This study investigates the hypothesis that these morphologically distinct epiphenomena of microvascular extravasation are linked by a common pathophysiological mechanism involving vascular endothelial growth/permeability factor (VEG/PF), which has been implicated in vascular leak phenomena including ascites, malignant effusions, and brain edema. Furthermore, VEG/PF has been isolated from cultured glioma cells, and both VEG/PF protein and messenger RNA transcripts are expressed in brain tumor tissue. To further elucidate the relationship of VEG/PF to PVBE and TACs, the authors examined 34 pathological specimens for VEG/PF expression. Nineteen primary low-grade tumors, 11 primary high-grade tumors, and four gliosis controls were immunostained with a polyclonal anti-VEG/PF immunoglobulin G antibody. Magnetic resonance imaging was used to quantitate PVBE and to determine the presence of TACs and tumor enhancement. The study revealed that eight VEG/PF-negative specimens exhibited no significant edema, whereas 26 VEG/PF-positive tumors exhibited either significant PVBE or TACs. Notably, eight of nine benign TACs that were not associated with PVBE immunostained positive for VEG/PF. These data indicate a high degree of correlation between VEG/PF expression by gliomas and the occurrence of PVBE or TACs, irrespective of tumor grade, thus supporting VEG/PF's pivotal role as the common pathophysiological link between these processes.

There have been few investigations of brain edema formation after intracerebral hemorrhage (ICH), despite the fact that mass effect and edema are important clinical complications. The present study was designed to investigate the time course for the formation and resolution of brain edema and to determine how changes in cerebral blood flow (CBF) and blood-brain barrier (BBB) permeability are temporally related to edema formation following ICH. Anesthetized adult rats received a sterile injection of 100 microliters of autologous blood into the caudate nucleus. Water and ion contents were measured immediately, at 4 and 12 hours, and daily to Day 7 (10 time points, six rats at each time) after experimental ICH. The water content of the ipsilateral basal ganglia increased progressively (p < 0.002) over the first 24 hours, then remained constant until after Day 5, when the edema began to resolve. Edema was most severe in the tissue immediately surrounding the hemorrhage; however, it was also present in the ipsilateral cortex, the contralateral cortex, and the basal ganglia. Measurements of local CBF (using [14C]-iodoantipyrine) and BBB permeability (using [3H]-alpha-aminoisobutyric acid) were obtained in separate groups of six to eight rats at various time intervals between 1 and 48 hours after ICH. Cerebral blood flow was reduced to 50% of control at 1 hour, returned to control values by 4 hours, but then decreased to less than 50% of control between 24 and 48 hours after ICH. The BBB permeability increased significantly prior to the occurrence of significant edema in the tissue surrounding the clot. However, BBB permeability in the more distant structures remained normal despite the development of edema. These results demonstrate a time course for the formation and resolution of brain edema following ICH similar to that observed during focal ischemia. Brain edema forms in the immediate vicinity of the clot as a result of both BBB disruption and the local generation of osmotically active substances and then spreads to adjacent structures. While local ischemia, due to the mass effect of the hemorrhage, may play a role in producing cytotoxic and vasogenic edema, the release of toxic substances from the clot should also be considered. Since edema is nearly maximal by 24 hours after ICH, therapy directed at reducing edema formation must be instituted within the 1st day.

Experimental brain tumors were produced in cats by xenotransplantation of the rat glioma clone F98 into the white matter of the left hemisphere. One to 4 weeks after implantation, local adenosine triphosphate (ATP), glucose, lactate, and tissue pH were measured via imaging techniques in cryostat sections passing through the center of the tumor and correlated with changes in water and electrolyte content. The tumors exhibited a heterogeneous metabolic pattern, with a tendency for ATP to decrease and lactate to increase during tumor development. Tissue pH was above 7.5 in tumors with high ATP content but it sharply declined at low ATP levels. In peritumoral edema, ATP also decreased and lactate increased but, in contrast to tumor tissue, pH became more alkaline. Metabolic changes were associated with edema formation, as evidenced by the rise in water and sodium content. There was a distinct difference between tumor tissue and peritumoral edema: in tumor tissue, pH declined with increasing water content, whereas in peritumoral edema it increased. These observations are interpreted as follows: 1) in tumor tissue, "lactacidosis" and ATP depletion are attributed to disturbances in blood flow, resulting in metabolic failure and the intracellular "cytotoxic" accumulation of water; 2) in peritumoral edema, "lactalkalosis" is the result of an efflux of (alkaline) lactate salts from the tumor into the expanded extracellular compartment, and the decrease in ATP is the volumetric effect of extracellular "vasogenic" edema fluid and not the result of cellular energy failure. These findings are of importance for the interpretation of volume-selective magnetic resonance spectroscopy and may contribute to the establishment of spectroscopic criteria for the evaluation of therapeutical interventions.

The authors investigated the pharmacokinetics of mannitol administered for treatment of vasogenic cerebral edema. A cortical cold injury was produced in 23 cats maintained under general anesthesia for 5 or 21 hours. Control animals received no mannitol, while treatment groups received either a single dose or five doses administered at 4-hour intervals of 0.33 gm/kg radiolabeled mannitol. Liquid scintillation counting was carried out to determine the concentrations of mannitol in the cerebral tissue, cerebrospinal fluid, plasma, and urine. Cerebral water content and linear progression of edema were also measured. Rapid plasma clearance prevented accumulation of mannitol after multiple intravenous injections, as 84% +/- 2% (mean +/- standard error of the mean) of the infused mannitol was excreted through the urine. However, there was progressive accumulation of mannitol within the cerebral tissue, especially in the edematous white matter where it reached a level of 0.33 +/- 0.03 mg/gm after five doses, exceeding the trough plasma concentrations by a ratio of 2.69:1. Water content measurement showed that a single dose of mannitol failed to reduce cerebral water content or edema progression at 4 hours postinjection, while multiple doses produced a 3% increase in water content in edematous regions (p greater than 0.0003). The results of this study demonstrated a reversal of the osmotic concentration gradient between edematous brain and plasma following multiple mannitol injections, associated with exacerbation of vasogenic cerebral edema.

The transit routes of fluid and particulate matter through brain tissue remain unclear. The object of this study was to examine the movement of macromolecules through brain tissue to further clarify the clearance pathways of edema proteins as they migrate toward the cortex. For this purpose, albumin solution (20 microliters rat albumin diluted to 65 mg/ml with mock cerebrospinal fluid (CSF)) was intracerebrally infused into the caudate putamen, and the migration through brain tissue as well as through the ultrastructure of the cortical surfaces was explored using an immunocytochemical technique. The authors observed immunoreactive product on the glial limitans and pial lining as well as in the extracellular space of the cortical neuropil at 24 hours postinfusion, confirming that the protein had reached the cortical surface. To confirm the efflux of macromolecules into the subarachnoid CSF, 71,200 D fluorescein isothiocyanate-dextran (FITC-dextran 71,200) was infused; cortical surfaces of brains removed en bloc as well as coronal sections were macroscopically observed under ultraviolet illumination at 15 minutes and 24 hours postinfusion. It was observed that infused FITC-dextran 71,200 mainly localized in the cortical white matter and caudate putamen of the infusion site at 15 minutes postinfusion and by 24 hours was distributed in the entire cortex of the infused hemisphere. However, the dynamics of lower-molecular-weight substances was completely different. The spatial distribution of FITC-dextran 4400 diverged upward toward the cortical surface and spread more extensively than FITC-dextran 71,200. These observations were consistent with a diffusion process as the spread of the tracer was dependent upon molecular size. These studies provide compelling evidence that a process other than bulk flow was involved in the spread of macromolecules through the extracellular space of the normal cortical neuropil to sink into the subarachnoid space. It was concluded that the CSF pathway via the extracellular space of the cortical neuropil is a primary route for clearance of extracellular edema proteins to the subarachnoid space and that diffusion is involved in this process.

Leukotrienes are powerful metabolites of arachidonic acid which are known to increase the permeability of peripheral blood vessels. These substances are found in brain tissue in association with cerebral ischemia, and in brain tumors. Therefore, it has been proposed that leukotrienes have a mediator function in brain edema. This hypothesis was subjected to further experimental analysis in this study, in which the authors investigated whether: 1) superfusion of the exposed brain surface with leukotrienes increases the permeability of extraparenchymal blood vessels in vivo; 2) intraparenchymal infusion of leukotrienes induces brain edema; and 3) pharmacological inhibition of leukotriene formation by BW755C, an inhibitor of leukotriene synthesis, reduces formation of brain edema from a standardized traumatic insult. The pial vessels of the parietal cortex of cats were examined by fluorescence microscopy during cerebral superfusion with the leukotrienes C4 (LTC4), D4 (LTD4), or E4 (LTE4) by using an open cranial window preparation. Intravenous Na(+)-fluorescein served as an in vivo blood-brain barrier (BBB) indicator. Superfusion of the pia with leukotrienes (up to 2 microM) did not open the barrier to fluorescein, but was associated with a significant constriction (up to 25%) of arterial and venous vessels. In experiments with slow infusion of leukotriene B4 (LTB4) or LTC4 into the white matter of feline brain, the tissue water content was subsequently determined in serial brain slices using the specific gravity method. Tissue water profiles obtained after a 15-microM infusion of either LTB4 or LTC4 were virtually identical with those of control animals infused with mock cerebrospinal fluid. Thus, neither LTB4 nor LTC4 led to an augmentation of infusion-induced brain edema. In a final series, a cold lesion of the left parietal cortex was induced in rabbits. Twenty-four hours later, swelling of the exposed hemisphere was quantified by gravimetrical comparison of its weight with that of the contralateral nontraumatized hemisphere. Eight animals received BW755C intravenously prior to and after trauma to inhibit formation of leukotrienes. Seven rabbits were infused with an equivalent volume of saline as a control study. The resulting hemispheric swelling was 7.7% +/- 0.6% (mean +/- standard error of the mean) 24 hours later in animals receiving BW755C and 7.8% +/- 1.2% in the control group, indicating that inhibition of leukotrienes was ineffective in preventing formation of vasogenic brain edema. The findings demonstrate that leukotrienes administered to the brain in concentrations occurring under pathological conditions do not open the BBB nor do they induce brain edema.(ABSTRACT TRUNCATED AT 400 WORDS)

To investigate the effects of focal neodymium:yttrium-aluminum-garnet (Nd:YAG) laser irradiation (lambda = 1060 nm) on regional cerebral blood flow, cerebral protein synthesis, and blood-brain barrier permeability, the parietal brain surface of 44 rats was irradiated with a focused laser beam at a constant output energy of 30 J. Survival times ranged from 5 minutes to 48 hours. Laser irradiation immediately caused well-defined cortical coagulation necrosis. Within 5 minutes after unilateral irradiation, 14C-iodoantipyrine autoradiographs demonstrated severely reduced blood flow to the irradiation site and perilesional neocortex, but a distinct reactive hyperemia in all other areas of the forebrain. Apart from a persistent ischemic focus in the vicinity of the cortical coagulation necrosis, blood flow alterations in remote areas of the brain subsided within 3 hours after irradiation. Autoradiographic assessment of 3H-tyrosine incorporation into brain proteins revealed rapid onset and prolonged duration of protein synthesis inhibition in perifocal morphologically intact cortical and subcortical structures. Impairment of amino acid incorporation proved to be completely reversible within 48 hours. Immunoautoradiographic visualization of extravasated plasma proteins using 3H-labeled rabbit anti-rat immunoglobulins-showed that, up to 1 hour after irradiation, immunoreactive proteins were confined to the neocortex at the irradiation site. At 4 hours, vasogenic edema was present in the vicinity of the irradiation site and the subcortical white matter, and, at later stages (16 to 36 hours), also extended into the contralateral hemisphere. Although this was followed by a gradual decrease in labeling intensity, resolution of edema was still not complete after 48 hours. Analysis of sequential functional changes in conjunction with morphological alterations indicates that the evolution of morphological damage after laser irradiation does not correlate with the time course and spatial distribution of protein synthesis inhibition or vasogenic edema. Although the central coagulation necrosis represents a direct effect of radiation, the final size of the laser-induced lesion is determined by a delayed colliquation necrosis due to persistent perifocal ischemia. Extent and severity of ischemia in a zone with initial preservation of neuroglial cells can be explained by the optical properties of the Nd:YAG laser; extensive scattering of light within brain parenchyma associated with a high blood-to-brain absorption ratio selectively affects blood vessels outside the irradiation focus.

Recent developments in the field of cerebral circulation and metabolism are reviewed, with emphasis on circulatory and metabolic events that have a bearing on brain damage incurred in ischemia. The first part of the treatise reviews aspects of cerebral metabolism that provide a link to the coupling of metabolism and blood flow, notably those that lead to a perturbation of cellular energy state, ionic homeostasis, and phospholipid metabolism. In the second part, attention is focused on the derangement of energy metabolism and its effects on ion fluxes, acid-base homeostasis, and lipid metabolism. It is emphasized that gross brain damage, involving edema formation and infarction, is enhanced by tissue acidosis, and that neuronal damage, often showing a pronounced selectivity in localization, appears related to a disturbed Ca2+ homeostasis, and to Ca2+-triggered events such as lipolysis and proteolysis.

Vasogenic edema was induced in mongrel cats by cold injury to study uptake and activation of the plasma-kallikrein-kinin system in central nervous system (CNS) tissue. A method was developed for quantitative assessment of kinin formation in affected brain tissue areas. Gross disruption of the blood-brain barrier by focal trauma causes marked penetration of plasma kininogens into necrotic and edematous brain tissue. Moreover, the kallikrein-kinin (KK) system was activated in both necrotic and perifocal edematous areas, and was markedly enhanced by additional cerebral ischemia. Formation of kinins in necrotic brain tissue led to consumption of approximately 60% to 80% of the amount of kininogens being taken up. In perifocal edematous tissue, formation of kinins was less pronounced, or even absent. However, if cerebral ischemia evolved after severe intracranial hypertension, kinins were also formed in the perifocal edematous brain. The intravascular origin of kininogens found in pathological tissue areas secondary to injury was deduced from the observation that cerebral tissue of the contralateral hemisphere with an intact blood-brain barrier had no measurable quantities of kininogens. Consumption of plasma kininogens or formation of kinins were assessed as the difference of the total amount of plasma kininogens taken up into the tissue minus the amount of kininogens found in the brain at postmortem examination. The data indicate that uptake and activation of the plasma-KK system might occur under all pathological conditions in which blood-brain barrier damage permits cerebral penetration of plasma proteins, such as with cerebral contusion, focal ischemia, and tumors. The potent pathophysiological mechanisms induced by kinins in CNS tissue, such as formation of brain edema, microcirculatory dysfunction, and enhancement of blood-brain barrier permeability, together with their formation in focal and perifocal pathological brain tissue, provide further support for a mediator function of the KK system. Methods that specifically interfere with the formation of kinins in damaged brain should therefore be expected to attenuate vasogenic edema.

Mongrel cats with experimental cryogenic brain lesions were treated with the carotenoid compound crocetin. It has been shown that crocetin increases the diffusion speed of oxygen through plasma, and should provide a net increase in available oxygen to the capillary endothelial cell. The treated group of animals showed a significant reduction in edema as compared to a comparable control group. It is suggested that oxygen availability is an important factor in vasogenic edema.

Evidence has previously been provided that administration of kinins to the cerebrum causes edema and opening of the blood-brain barrier. It has further been shown that these highly active compounds are formed in the brain under pathophysiological conditions. Their formation was enhanced when cerebral blood flow became compromised by an increase in intracranial pressure. Final evidence, however, was not available as to whether specific inhibition of the kallikrein-kinin (KK) system has a therapeutic function in acute head injury. The authors have demonstrated in rabbits that inhibition of the activating enzyme kallikrein by aprotinin or by aprotinin plus soybean trypsin inhibitor (SBTI), which interfere with plasma and tissue kallikrein, is associated with a decrease in formation of posttraumatic swelling after a standardized cold lesion to the brain. Saline-treated control animals with cerebral cold-induced injury had an increase in hemispheric weight 24 hours later of 13.0% +/- 0.8% (standard error of the mean) in the damaged hemisphere compared to the contralateral nondamaged hemisphere. Administration of aprotinin or aprotinin plus SBTI led to a significant reduction of hemispheric swelling of 10.1% +/- 0.7% or 10.4% +/- 0.7%, respectively. In animals receiving SBTI only, hemispheric swelling evolving from cold injury was not significantly reduced. Therapeutic reduction of brain edema by aprotinin cannot be attributed to a nonspecific effect on the blood pressure, which in the experimental groups remained almost normal as compared to the control animals. Failure of SBTI to influence posttraumatic brain swelling may have resulted from disturbances in intravascular coagulation. Measurements of aprotinin in plasma and tissue demonstrate that the inhibitor doses employed are within an effective therapeutic range. Attenuation of brain edema by specific inhibition of the KK system provides evidence for a mediator role of kinins in vasogenic edema. Clinical trials with inhibitors of the KK system in acute forms of traumatic lesions associated with vasogenic edema appear worthwhile.

The pathophysiological potential of mediator substances in manifestations of secondary brain damage is attracting increased attention. This is particularly true of the excitatory transmitters glutamate and arachidonic acid. Noxious properties of these compounds in central nervous tissue have been demonstrated. The current study was performed to determine whether glutamate and arachidonate are released in brain tissue secondary to focal trauma. For this purpose, a cold injury of exposed cerebral cortex was induced in cats. Marked accumulation of glutamate was observed in interstitially drained edema fluid, reaching 10 to 15 times the level that was assessed in normal cerebrospinal fluid (CSF) prior to trauma. The extracellular release of glutamate was further dramatically enhanced by a critical decrease of the cerebral perfusion pressure due to a malignant increase of intracranial pressure. Under these conditions, glutamate concentrations 1000 to 1500 times normal levels accumulated in vasogenic edema fluid, demonstrating a relationship between the extent of the release of glutamate in damaged brain and the severity of the insult. Although under normal conditions glutamate concentrations in plasma were considerably higher than in the interstitial fluid, the pronounced increase of glutamate in this compartment due to trauma cannot be explained by transport of the compound together with the plasma-like edema from the intravascular space. Corresponding findings were obtained for free fatty acid concentrations in edema fluid. Almost all fatty acids that were studied had a significantly higher concentration in edema fluid than in normal CSF obtained as a control prior to trauma. However, contrary to the findings for glutamate, fatty acid concentrations in edema fluid were lower than in plasma. Accumulation of fatty acids in vasogenic edema fluid might, therefore, have resulted from uptake of the material together with edema fluid through the breached blood-brain barrier. Arachidonic acid was an exception. Its concentrations were significantly higher in edema fluid than in plasma, suggesting that it was released from cerebral parenchyma as the underlying mechanism of its extracellular accumulation. The current observations provide further support for a mediator function of glutamate and arachidonic acid in acute traumatic lesions of the brain. Quantitative assessment of the release of highly active mediator substances in brain tissue may facilitate analysis of the therapeutic efficiency of specific treatment aimed at interfering with the release or pathological function of mediators of secondary brain damage.

Plasma and bradykinin were perfused into the ventricular system of mongrel dogs to investigate whether either or both induce brain edema. Formation of cerebral edema was determined by measurement of cerebral water and electrolytes in periventricular white matter, cerebral cortex, and caudate nucleus. The response of cerebral tissue to exposure to bradykinin or to plasma, as a carrier of kininogens, was analyzed by assessment of the perfusate composition after ventricle passage. The authors report that cerebral administration of bradykinin induces cerebral edema. Ventricular perfusion with plasma also led to an increase of cerebral water content which was restricted to the white matter, but involved all brain tissue areas, if bradykinin was used. Ventricular perfusion with plasma was associated with consumption of the kinin precursor (kininogens) indicative of formation of kinins. Significant consumption of the precursor was found in five out of nine animals subjected to plasma perfusion of the ventricular system. In these animals a close correlation between the increase of white matter water content and kininogen-consumption as a measure of kinin-formation was obtained. Marked kinin-degrading activity was observed during ventricular perfusion with bradykinin as concluded from a considerable decrease of bradykinin concentration in the cisternal effluent compared to the inflowing perfusate concentration. Ventricular perfusion with plasma was associated with a decrease of K+ clearance capacity with continued duration, and in two animals with a release of glutamate into the plasma perfusate, suggesting an involvement of cytotoxic mechanisms. These findings provide support for the hypothesis of a mediator function of the kallikrein-kinin (KK) system in vasogenic brain edema. The next question that needs to be answered to complete the picture--does spontaneous activation of the KK system occur in conditions leading to vasogenic edema?--is studied in a subsequent report.

The authors have assessed the effects of subacute traumatic brain edema (BE) on cerebral circulation and metabolism, and on clinical outcome. Fifty-five severely injured, comatose, young patients who survived for more than 24 hours were studied on 78 occasions within 30 days of injury. After hematomas had been surgically evacuated, BE was diagnosed by radiological evidence of brain swelling, demonstrated by cerebral angiograms and ventriculograms. At identical levels of carbon dioxide pressure, intracranial pressure was significantly elevated in the Edema Group to twice the value in the No Edema Group (27.1 vs 14.1 torr). There were, however, no significant differences in cerebral perfusion pressure cerebral blood flow, resistance to blood flow, cerebral metabolic oxygen rate, ventricular cerebrospinal fluid acid-base, lactate, K+ or Na+ concentrations, or in clinical outcome. It is concluded that this type of subacute traumatic BE, which is significantly associated with surgical lesions, is not of major hemodynamic or clinical significance in intensively treated patients, and does not cause cerebral ischemia. Patient outcome is determined more by the severity of the initial diffuse cortical and subcortical injury than by the presence or absence of subacute BE.

The bioenergetic mechanisms of vasogenic edema were studied by measuring concentrations of adenosine triphosphate (ATP), phosphocreatine (CrP), and lactate in rapidly frozen edematous white matter in cats. When edema was produced using a cold lesion, it was found that both ATP and CrP were reduced to one-half of control values, and that lactate was elevated. When a correction was applied for dilution, however, it was found that high-energy phosphates were equal to control values, and that lactate was even more significantly elevated. This pattern contrasted with that seen in white-matter ischemia, in which CrP is depressed out of proportion to ATP. Finally, it was found that the white-matter lactate-concentration in the plasma infusion model of edema was increased. It is concluded that vasogenic edema induces an increase in lactate, but does not deplete high-energy phosphate compounds in affected white matter.

Total parenteral nutrition (TPN) has been shown to decrease mortality and to increase the rate of recovery in head-injured patients. However, a recent short-term animal experiment has raised concern over the potential enhancement of vasogenic edema by TPN. The experiment described here was undertaken to examine longer-term effects of TPN infusion on vasogenic edema development. Twenty-four rats received an infusion of a TPN solution (35% glucose) or 0.9% saline at 4 ml/kg/hr for 4 or 26 hours following cold injury. In the 4-hour experiment, TPN increased the serum glucose level to 772 +/- 57 mg/dl compared to 160 +/- 14 mg/dl in the saline-treated animals (p = 0.0001) and increased serum osmolality to 312 +/- 3 mOsm/kg compared to 291 +/- 3 mOsm/kg in the saline-treated group (p = 0.0006). In the 26-hour experiment, TPN-infused rats were also hyperglycemic and hyperosmotic by 4 hours postinjury and remained hyperglycemic at 26 hours postinjury (serum glucose level 374 +/- 97 mg/dl compared to 141 +/- 3 mg/dl in saline-treated animals; p = 0.0371). Although by 26 hours the TPN-infused rats appeared hyperosmotic compared to the saline-treated rats, high variability in the TPN group prevented statistical confirmation of this observation (serum osmolality 337 +/- 35 mOsm/kg in the TPN group compared to 287 +/- 6 mOsm/kg in the saline group). A three-way analysis of variance with repeated measures was used to analyze the effect of infusion (saline vs. TPN), time (4 vs. 26 hours), and cold injury on the specific gravity of the five brain regions studied. Cold injury significantly increased edema development in the injured versus uninjured hemisphere for every region studied (p less than or equal to 0.0034, all five regions), and edema development increased significantly between 4 and 26 hours in three of the five regions (p less than or equal to 0.0207, all three regions). The infusion fluid was not a significant factor in any of the analyses. In conclusion, TPN infusion produced hyperglycemia and hyperosmolality in cold-injured rats but did not enhance vasogenic edema development in any brain region studied.

A Remington humane stunner was used to deliver a blow to the left side of the surgically-exposed skull in ketamine-anesthetized cats. At 15 minutes after the trauma, brain tissue was frozen in situ. In animals without visible tissue hemorrhage (Grade 0) and in those with unilateral cerebral contusions involving the cerebral cortex and white matter (Grade 2), regional cerebral metabolite concentrations were measured by enzymatic-fluorometric techniques and edema was tested with an organic gradient. No substantial changes in cerebral metabolite concentrations were observed in head-injured animals without cerebral contusions. In animals with unilateral contusions, the white matter neighboring the tissue hemorrhage had an increase in lactic acid and a decrease in phosphocreatine as compared to values from corresponding areas on the contralateral side, and in control and Grade 0 animals. The cerebral cortex adjacent to tissue hemorrhage had a variable response that ranged from metabolite concentrations within normal ranges to marked decreases in high-energy phosphates and increases in lactic acid. Metabolites of the cortex and white matter contralateral as well as distant to contusion were not statistically different from values of control animals. Changes in several metabolites correlated well with the magnitude of edema. It is concluded that focal metabolic alterations can occur shortly after severe blunt head injury, and that these events may contribute to acute traumatic cerebral edema.

The isolation of edema fluid from cats with cold-induced cerebral edema allowed the study of changes of Na+ and K+ content, lactate dehydrogenase and creatine phosphokinase activity, colloid osmotic pressure and the level of intravenously administered 99mTc-albumin in the edema fluid during a period of hypoxia. The changes consisted of an increase of all mentioned parameters, except Na+; and could be interpreted as a concentration of solutes (but for Na+) in the extracellular edema fluid, concomitant to a reduction of the extracellular space, as the oxygen deficiency caused improper functioning of the cellular Na+-K+ pump, with a resulting shift of fluid (including Na+) into the cellular elements.

A simple method was developed for the laboratory preparation of gradient columns of specific gravity used in measurement of brain-tissue water. By this automated technique, virtually linear and repeatable density gradients were obtained from which values of tissue specific gravity could be determined. The specific gravity of both solid and fresh cortex and white matter from adult cats was measured and converted to units of percent water per gram tissue using conversion factors derived for this purpose and applicable to studies of brain edema.

Edema fluid isolated from cats with cold-induced brain edema was subjected to analysis of electrolyte content, enzyme activities, colloid osmotic pressure and the radioactivity of intravenously injected 99mTc-labeled albumin. The findings corroborate the essential features of vasogenic edema, such as its origin from the blood plasma, its rapid propagation into the white matter of the brain as contrasted with the delayed spread into gray matter, and its contribution to composition of cerebrospinal fluid. Moreover, the elevated activities of cellular enzymes and K+ content of edema fluid point to the admixture with cellular contents due to the freezing damage.

Peritumoral brain edema was produced by intracerebral transplantation of Walker 256 tumor in rats. Local cerebral blood flow (LCBF), local cerebral glucose utilization (LCGU), and capillary permeability were studied in untreated and methylprednisolone-treated rats by quantitative autoradiography. In the untreated group, LCBF and LCGU were widely depressed in the cortex and deep structures of the hemisphere ipsilateral to the tumor. In the methylprednisolone-treated animals, LCBF and LCGU were significantly better than in the untreated animals. Capillary permeability was highly increased in the viable part of the tumor in the untreated animals. In the methylprednisolone-treated group, capillary permeability of the tumor was significantly lower than that in the untreated group. These results may suggest that increase in capillary permeability of the tumor is the major source for edema fluid production, and that methylprednisolone improves brain edema by decreasing capillary permeability of the tumor. Decrease in edema fluid formation may result in restoration of blood flow and glucose metabolism in the adjacent brain tissue, and may improve clinical symptoms and signs.

Serum-free conditioned medium derived from confluent monolayer cultures of malignant human astroglial tumors contains a substance that rapidly increases capillary vascular permeability after intradermal injection into guinea pigs. Accumulation of vascular permeability factor (VPF) activity occurs with increasing duration of tumor incubation in vitro. Expression of this activity is inhibited by incubation of cell cultures with cycloheximide or dexamethasone. This VPF is an acid-stable heat-labile macromolecule that is inactivated by trypsin and pepsin and binds immobilized heparin. Activity is retained by ultrafiltration with 30,000-dalton cut-off microconcentrators. Pretreatment of test animals with systemic dexamethasone prior to intradermal injection of VPF diminishes microvascular permeability. Furthermore, VPF activity is not inhibited by antihistamines. Secretion of VPF may cause the vasogenic brain edema that is frequently associated with malignant primary and metastatic intracerebral tumors. Inhibition by dexamethasone of both VPF expression in tissue culture, and VPF activity at the microvascular level in test animals, is in keeping with the known efficacy of this agent in treating the vasogenic edema associated with brain tumors.

The distribution, retention, and phototoxicity of the sensitizer hematoporphyrin derivative (HPD) were studied following intraperitoneal and direct intraneoplastic injections of the agent into subcutaneous or intracerebral gliosarcomas in rats. Forty-eight hours after intraperitoneal injection, the ratio of tritiated (3H) HPD in subcutaneous tumor: adjacent normal skin was about 1.4:1 and the ratio in tumor: normal brain was 3:1. In contrast, direct injection of 3H-HPD into subcutaneous tumors resulted in tumor: adjacent normal skin concentration ratios of approximately 44:1 and tumor: normal brain ratios of about 61:1. For rats bearing intracerebral gliosarcomas, intraperitoneal administration of 3H-HPD resulted in approximately 1.3-fold sensitization in tumor tissue relative to adjacent edematous brain. In contrast, after direct injection into intracerebral tumors, the tumor: adjacent edematous brain and tumor: skin 3H-HPD ratios were 3:1 and 32:1, respectively. In all cases, 3H-HPD was found in every portion of the tumor, even at a distance from the injection site. For the 3H-HPD doses used in this study, after direct injection both subcutaneous and intracerebral tumor tissue contained about three to four times more 3H-HPD than tumors in rats receiving intraperitoneal 3H-HPD. Both in vitro and in vivo clonogenic assays demonstrated that the photodynamic inactivation of the tumors was significantly greater after direct injection than after intraperitoneal injection.