Different pharmaceutical preparations of Δ9 -tetrahydrocannabinol differentially affect its behavioral effects in rats.

Based on the contribution of the endocannabinoid system to the pathophysiology of schizophrenia, the primary pro-psychotic ingredient of Cannabis sativa, Δ-9-tetrahydrocannabinol (Δ-9-THC), is used in preclinical as well as clinical research to mimic schizophrenia-like symptoms. While it is common to administer lipid-based formulations of Δ-9-THC in human studies orally, intraperitoneal injections of water-based solutions are used in animal models. Because of the poor water solubility of Δ-9-THC, solubilizers such as ethanol and/or emulsifiers are needed for these preparations. In order to test whether a lipid-based solvent would be superior over a water-based vehicle in rats, we compared the effects on locomotor activity and prepulse inhibition (PPI) of the acoustic startle reaction, as well as pharmacokinetic data obtained from rats' serum and brain tissue samples. Up to 50 mg/kg Δ-9-THC in the lipid-based formulation was not able to induce any behavioral alterations, while already 5 mg/kg of the water-based Δ-9-THC preparation significantly reduced locomotor activity. This also induced a small but significant PPI reduction, which was prepulse intensity dependent. Interestingly, the reflexive motor response to the startle stimulus was not affected by the water-based Δ-9-THC solution. Analysis of serum and brain Δ-9-THC levels by high-performance liquid chromatography/mass spectrometry revealed that although the final concentration reached in the brain was comparable for both pharmaceutical preparations, the water-based formulation achieved a faster kinetic. We, therefore, conclude that the slope of the Δ-9-THC concentration-time curve and the resulting cannabinoid receptor type 1 activation per time unit are responsible for the induction of behavioral alterations.

Glucose consumption of inflammatory cells masks metabolic deficits in the brain.

Inflammatory cells such as microglia need energy to exert their functions and to maintain their cellular integrity and membrane potential. Subsequent to cerebral ischemia, inflammatory cells infiltrate tissue with limited blood flow where neurons and astrocytes died due to insufficient supply with oxygen and glucose. Using dual tracer positron emission tomography (PET), we found that concomitant with the presence of inflammatory cells, transport and consumption of glucose increased up to normal levels but returned to pathological levels as soon as inflammatory cells disappeared. Thus, inflammatory cells established sufficient glucose supply to satisfy their energy demands even in regions with insufficient supply for neurons and astrocytes to survive. Our data suggest that neurons and astrocytes died from oxygen deficiency and inflammatory cells metabolized glucose non-oxidatively in regions with residual availability. As a consequence, glucose metabolism of inflammatory cells can mask metabolic deficits in neurodegenerative diseases. We further found that the PET tracer did not bind to inflammatory cells in severely hypoperfused regions and thus only a part of the inflammation was detected. We conclude that glucose consumption of inflammatory cells should be taken into account when analyzing disease-related alterations of local cerebral metabolism.

Lithium prevents early cytosolic calcium increase and secondary injurious calcium overload in glycolytically inhibited endothelial cells.

Cytosolic free calcium concentration ([Ca(2+)]i) is a central signalling element for the maintenance of endothelial barrier function. Under physiological conditions, it is controlled within narrow limits. Metabolic inhibition during ischemia/reperfusion, however, induces [Ca(2+)]i overload, which results in barrier failure. In a model of cultured porcine aortic endothelial monolayers (EC), we addressed the question of whether [Ca(2+)]i overload can be prevented by lithium treatment. [Ca(2+)]i and ATP were analysed using Fura-2 and HPLC, respectively. The combined inhibition of glycolytic and mitochondrial ATP synthesis by 2-desoxy-d-glucose (5mM; 2-DG) plus sodium cyanide (5mM; NaCN) caused a significant decrease in cellular ATP content (14±1 nmol/mg protein vs. 18±1 nmol/mg protein in the control, n=6 culture dishes, P<0.05), an increase in [Ca(2+)]i (278±24 nM vs. 71±2 nM in the control, n=60 cells, P<0.05), and the formation of gaps between adjacent EC. These observations indicate that there is impaired barrier function at an early state of metabolic inhibition. Glycolytic inhibition alone by 10mM 2-DG led to a similar decrease in ATP content (14±2 nmol/mg vs. 18±1 nmol/mg in the control, P<0.05) with a delay of 5 min. The [Ca(2+)]i response of EC was biphasic with a peak after 1 min (183±6 nM vs. 71±1 nM, n=60 cells, P<0.05) followed by a sustained increase in [Ca(2+)]i. A 24-h pre-treatment with 10mM of lithium chloride before the inhibition of ATP synthesis abolished both phases of the 2-DG-induced [Ca(2+)]i increase. This effect was not observed when lithium chloride was added simultaneously with 2-DG. We conclude that lithium chloride abolishes the injurious [Ca(2+)]i overload in EC and that this most likely occurs by preventing inositol 3-phosphate-sensitive Ca(2+)-release from the endoplasmic reticulum. Though further research is needed, these findings provide a novel option for therapeutic strategies to protect the endothelium against imminent barrier failure.

Potential of early [(18)F]-2-fluoro-2-deoxy-D-glucose positron emission tomography for identifying hypoperfusion and predicting fate of tissue in a rat embolic stroke model.

BACKGROUND AND PURPOSE: Experimental stroke models are essential to study in vivo pathophysiological processes of focal cerebral ischemia. In this study, an embolic stroke model in rats was applied (1) to characterize early development of regional cerebral blood flow and metabolism with positron emission tomography (PET) using [(15)O]H(2)O and [(18)F]-2-fluoro-2-deoxy-D-glucose (FDG); and (2) to identify potential parameters for predicting tissue fate. METHODS: Remote occlusion of the middle cerebral artery was induced in 10 Wistar rats by injection of 4 TiO(2) macrospheres. Sequential [(15)O]H(2)O-PET (baseline, 5, 30, 60 minutes after middle cerebral artery occlusion) and FDG-PET measurements (75 minutes after middle cerebral artery occlusion) were performed. [(15)O]H(2)O-PET data and FDG kinetic parameters were compared with MRIs and histology at 24 hours. RESULTS: Regional cerebral blood flow decreased substantially within 30 minutes after middle cerebral artery occlusion (41% to 58% of baseline regional cerebral blood flow; P<0.001) with no relevant changes between 30 and 60 minutes. At 60 minutes, regional cerebral blood flow correlated well with the unidirectional transport parameter K1 of FDG in all animals (r=0.86±0.09; P<0.001). Tissue fate could be accurately predicted taking into account K1 and net influx rate constant Ki of FDG. The infarct volume predicted by FDG-PET (375.8±102.3 mm(3)) correlated significantly with the infarct size determined by MRI after 24 hours (360.8±93.7 mm(3); r=0.85). CONCLUSIONS: Hypoperfused tissue can be identified by decreased K1 of FDG. Acute ischemic tissue can be well characterized using K1 and Ki allowing for discrimination between infarct core and early viable tissue. Because FDG-PET is widely spread, our findings can be easily translated into clinical application for early diagnoses of ischemia.

The severity of ischemia determines and predicts malignant brain edema in patients with large middle cerebral artery infarction.

BACKGROUND: In order to determine the impact of the severity of ischemia on malignant edema formation, we investigated various degrees of perfusional deficit by (11)C-flumazenil PET in patients with large middle cerebral artery (MCA) infarction. METHODS: 17 patients with large MCA stroke were included. Cerebral blood flow (CBF) was measured 15.9 ± 6.4 h after the ictus. Patients were divided into a malignant (n = 9) and a benign group (n = 8) as a function of their clinical courses and edema. Edema was measured as maximal midline shift on follow-up CTs. Total hypoperfusion volume was divided into different subvolumes according to the degree of CBF reduction. RESULTS: Subvolumes of severe ischemia relative to total ischemic area were significantly larger in the malignant group than in the benign group and were significantly correlated with edema formation. The highest correlation and best predictive values for edema formation with a sensitivity, specificity, and a positive and negative predictive value of 100% were found for subvolumes with severe ischemia. Correlation coefficients and prediction decreased for subvolumes with less severe perfusional deficit, pointing to the risk of misclassifying patients when relying on the volume of total perfusional deficit alone. CONCLUSIONS: Malignant MCA infarction seems to be determined more by the volume of severe perfusional deficit than that of total perfusional deficit. Assessment of severely ischemic areas allows prediction of malignant edema formation and might help to select candidates for hemicraniectomy.

Effort-based decision making in the rat: an [18F]fluorodeoxyglucose micro positron emission tomography study.

Decision making refers to the process by which subjects choose between competing courses of action based on the expected costs and benefits of their consequences. Lesion studies in rats suggest that the anterior cingulate cortex and the nucleus accumbens are key structures of a neural system that subserves effort-based decision making. Little is known about brain activation associated with effort-based decisions in intact rats. Using an open hypothesis approach, we used 2-deoxy-2[(18)F]fluoro-D-glucose positron emission tomography (FDG-PET) to assess regional metabolic changes in two conditions of an effort-based decision making task. In the "same effort" condition, male rats could choose between two response options associated with the same effort but different reward sizes, i.e., decision making was simply a function of reward size. By contrast, in the "different effort" condition, an integration of different efforts and reward sizes associated with the two response options was necessary before making a decision. Separate PET scans were performed from each condition. Subtractive analysis revealed that metabolic activity was increased in the different effort relative to the same effort condition in the left anterior cingulate, left orbitofrontal and prelimbic cortex region. Metabolic activity was decreased in the infralimbic cortex and septum region. Our findings suggest that making decisions on how much effort to invest to obtain greater rewards evokes changes of metabolic activity in multiple brain areas associated with cognitive, limbic, motor and autonomic functions. This study demonstrates that FDG-PET provides a tool to determine in rats regional brain metabolic activity in cognitive tasks.

Noninvasive imaging of endogenous neural stem cell mobilization in vivo using positron emission tomography.

Neural stem cells reside in two major niches in the adult brain [i.e., the subventricular zone (SVZ) and the dentate gyrus of the hippocampus]. Insults to the brain such as cerebral ischemia result in a physiological mobilization of endogenous neural stem cells. Since recent studies showed that pharmacological stimulation can be used to expand the endogenous neural stem cell niche, hope has been raised to enhance the brain's own regenerative capacity. For the evaluation of such novel therapeutic approaches, longitudinal and intraindividual monitoring of the endogenous neural stem cell niche would be required. However, to date no conclusive imaging technique has been established. We used positron emission tomography (PET) and the radiotracer 3'-deoxy-3'-[(18)F]fluoro-l-thymidine ([(18)F]FLT) that enables imaging and measuring of proliferation to noninvasively detect endogenous neural stem cells in the normal and diseased adult rat brain in vivo. This method indeed visualized neural stem cell niches in the living rat brain, identified as increased [(18)F]FLT-binding in the SVZ and the hippocampus. Focal cerebral ischemia and subsequent damage of the blood-brain barrier did not interfere with the capability of [(18)F]FLT-PET to visualize neural stem cell mobilization. Moreover, [(18)F]FLT-PET allowed for an in vivo quantification of increased neural stem cell mobilization caused by pharmacological stimulation or by focal cerebral ischemia. The data suggest that noninvasive longitudinal monitoring and quantification of endogenous neural stem cell activation in the brain is feasible and that [(18)F]FLT-PET could be used to monitor the effects of drugs aimed at expanding the neural stem cell niche.

Recurrent spreading depolarizations after subarachnoid hemorrhage decreases oxygen availability in human cerebral cortex.

OBJECTIVE: Delayed ischemic neurological deficit (DIND) contributes to poor outcome in subarachnoid hemorrhage (SAH) patients. Because there is continuing uncertainty as to whether proximal cerebral artery vasospasm is the only cause of DIND, other processes should be considered. A potential candidate is cortical spreading depolarization (CSD)-induced hypoxia. We hypothesized that recurrent CSDs influence cortical oxygen availability. METHODS: Centers in the Cooperative Study of Brain Injury Depolarizations (COSBID) recruited 9 patients with severe SAH, who underwent open neurosurgery. We used simultaneous, colocalized recordings of electrocorticography and tissue oxygen pressure (p(ti)O(2)) in human cerebral cortex. We screened for delayed cortical infarcts by using sequential brain imaging and investigated cerebral vasospasm by angiography or time-of-flight magnetic resonance imaging. RESULTS: In a total recording time of 850 hours, 120 CSDs were found in 8 of 9 patients. Fifty-five CSDs ( approximately 46%) were found in only 2 of 9 patients, who later developed DIND. Eighty-nine ( approximately 75%) of all CSDs occurred between the 5th and 7th day after SAH, and 96 (80%) arose within temporal clusters of recurrent CSD. Clusters of CSD occurred simultaneously, with mainly biphasic CSD-associated p(ti)O(2) responses comprising a primary hypoxic and a secondary hyperoxic phase. The frequency of CSD correlated positively with the duration of the hypoxic phase and negatively with that of the hyperoxic phase. Hypoxic phases significantly increased stepwise within CSD clusters; particularly in DIND patients, biphasic p(ti)O(2) responses changed to monophasic p(ti)O(2) decreases within these clusters. Monophasic hypoxic p(ti)O(2) responses to CSD were found predominantly in DIND patients. INTERPRETATION: We attribute these clinical p(ti)O(2) findings mainly to changes in local blood flow in the cortical microcirculation but also to augmented metabolism. Besides classical contributors like proximal cerebral vasospasm, CSD clusters may reduce O(2) supply and increase O(2) consumption, and thereby promote DIND.

Spreading depolarizations cycle around and enlarge focal ischaemic brain lesions.

How does infarction in victims of stroke and other types of acute brain injury expand to its definitive size in subsequent days? Spontaneous depolarizations that repeatedly spread across the cerebral cortex, sometimes at remarkably regular intervals, occur in patients with all types of injury. Here, we show experimentally with in vivo real-time imaging that similar, spontaneous depolarizations cycle repeatedly around ischaemic lesions in the cerebral cortex, and enlarge the lesion in step with each cycle. This behaviour results in regular periodicity of depolarization when monitored at a single point in the lesion periphery. We present evidence from clinical monitoring to suggest that depolarizations may cycle in the ischaemic human brain, perhaps explaining progressive growth of infarction. Despite their apparent detrimental role in infarct growth, we argue that cycling of depolarizations around lesions might also initiate upregulation of the neurobiological responses involved in repair and remodelling.

Spreading depolarizations occur in human ischemic stroke with high incidence.

OBJECTIVE: Cortical spreading depression (CSD) and periinfarct depolarization (PID) have been shown in various experimental models of stroke to cause secondary neuronal damage and infarct expansion. For decades it has been questioned whether CSD or PID occur in human ischemic stroke. Here, we describe CSD and PID in patients with malignant middle cerebral artery infarction detected by subdural electrocorticography (ECoG). METHODS: Centres of the Co-operative Study of Brain Injury Depolarisations (COSBID) recruited 16 patients with large middle cerebral artery infarction. During surgery for decompressive hemicraniectomy, an electrode strip was placed on the periinfarct region, from which four ECoG channels were acquired. RESULTS: A total of 1,638 hours was recorded; mean monitoring time per patient was 109.2 hours. A total of 127 CSD and 42 PID events were observed. In CSD, a stereotyped slow potential change spreading between adjacent channels was accompanied by transient depression of ECoG activity. In PID, a slow potential change spread between neighboring channels despite already established suppression of ECoG activity. Most CSDs and PIDs appeared repetitively in clusters. CSD or PID was observed in all but two patients. In these two patients, the electrode strip had been placed over infarcted tissue, and accordingly, no local ECoG or recurrent transient depolarization activity occurred throughout the observation period. INTERPRETATION: CSD and PID occurred spontaneously with high frequency in this study of patients with malignant middle cerebral artery infarction. This suggests that the large volume of experimental studies of occlusive stroke that implicate spreading depolarizations in its pathophysiology can be translated, with appropriate caution, to patients and their treatment.

Sleep deprivation increases oleoylethanolamide in human cerebrospinal fluid.

This study investigated the role of two fatty acid ethanolamides, the endogenous cannabinoid anandamide and its structural analog oleoylethanolamide in sleep deprivation of human volunteers. Serum and cerebrospinal fluid (CSF) samples were obtained from 20 healthy volunteers before and after a night of sleep deprivation with an interval of about 12 months. We found increased levels of oleoylethanolamide in CSF (P = 0.011) but not in serum (P = 0.068) after 24 h of sleep deprivation. Oleoylethanolamide is an endogenous lipid messenger that is released after neural injury and activates peroxisome proliferator-activated receptor-alpha (PPAR-alpha) with nanomolar potency. Exogenous PPAR-alpha agonists, such as hypolipidemic fibrates and oleoylethanolamide, exert both neuroprotective and neurotrophic effects. Thus, our results suggest that oleoylethanolamide release may represent an endogenous neuroprotective signal during sleep deprivation.

Imaging-guided gene therapy of experimental gliomas.

To further develop gene therapy for patients with glioblastomas, an experimental gene therapy protocol was established comprising a series of imaging parameters for (i) noninvasive assessment of viable target tissue followed by (ii) targeted application of herpes simplex virus type 1 (HSV-1) amplicon vectors and (iii) quantification of treatment effects by imaging. We show that viable target tissue amenable for application of gene therapy vectors can be identified by multitracer positron emission tomography (PET) using 2-(18)F-fluoro-2-deoxy-D-glucose, methyl-(11)C-L-methionine, or 3'-deoxy-3'-(18)F-fluoro-L-thymidine ([(18)F]FLT). Targeted application of HSV-1 amplicon vectors containing two therapeutic genes with synergistic antitumor activity (Escherichia coli cytosine deaminase, cd, and mutated HSV-1 thymidine kinase, tk39, fused to green fluorescent protein gene, gfp) leads to an overall response rate of 68%, with 18% complete responses and 50% partial responses. Most importantly, we show that the "tissue dose" of HSV-1 amplicon vector-mediated gene expression can be noninvasively assessed by 9-[4-(18)F-fluoro-3-(hydroxymethyl)butyl]guanine ([(18)F]FHBG) PET. Therapeutic effects could be monitored by PET with significant differences in [(18)F]FLT accumulation in all positive control tumors and 72% in vivo transduced tumors (P = 0.01) as early as 4 days after prodrug therapy. For all stably and in vivo transduced tumors, cdIREStk39gfp gene expression as measured by [(18)F]FHBG-PET correlated with therapeutic efficiency as measured by [(18)F]FLT-PET. These data indicate that imaging-guided vector application with determination of tissue dose of vector-mediated gene expression and correlation to induced therapeutic effect using multimodal imaging is feasible. This strategy will help in the development of safe and efficient gene therapy protocols for clinical application.

Early blood-brain barrier dysfunction predicts neurological outcome following aneurysmal subarachnoid hemorrhage.

BACKGROUND: Disease progression and delayed neurological complications are common after aneurysmal subarachnoid hemorrhage (aSAH). We explored the potential of quantitative blood-brain barrier (BBB) imaging to predict disease progression and neurological outcome. METHODS: Data were collected as part of the Co-Operative Studies of Brain Injury Depolarizations (COSBID). We analyzed retrospectively, blinded and semi-automatically magnetic resonance images from 124 aSAH patients scanned at 4 time points (24-48 h, 6-8 days, 12-15 days and 6-12 months) after the initial hemorrhage. Volume of brain with apparent pathology and/or BBB dysfunction (BBBD), subarachnoid space and lateral ventricles were measured. Neurological status on admission was assessed using the World Federation of Neurosurgical Societies and Rosen-Macdonald scores. Outcome at ≥6 months was assessed using the extended Glasgow outcome scale and disease course (progressive or non-progressive based on imaging-detected loss of normal brain tissue in consecutive scans). Logistic regression was used to define biomarkers that best predict outcomes. Receiver operating characteristic analysis was performed to assess accuracy of outcome prediction models. FINDINGS: In the present cohort, 63% of patients had progressive and 37% non-progressive disease course. Progressive course was associated with worse outcome at ≥6 months (sensitivity of 98% and specificity of 97%). Brain volume with BBBD was significantly larger in patients with progressive course already 24-48 h after admission (2.23 (1.23-3.17) folds, median with 95%CI), and persisted at all time points. The highest probability of a BBB-disrupted voxel to become pathological was found at a distance of ≤1 cm from the brain with apparent pathology (0·284 (0·122-0·594), p < 0·001, median with 95%CI). A multivariate logistic regression model revealed power for BBBD in combination with RMS at 24-48 h in predicting outcome (ROC area under the curve = 0·829, p < 0·001). INTERPRETATION: We suggest that early identification of BBBD may serve as a key predictive biomarker for neurological outcome in aSAH. FUND: Dr. Dreier was supported by grants from the Deutsche Forschungsgemeinschaft (DFG) (DFG DR 323/5-1 and DFG DR 323/10-1), the Bundesministerium für Bildung und Forschung (BMBF) Center for Stroke Research Berlin 01 EO 0801 and FP7 no 602150 CENTER-TBI. Dr. Friedman was supported by grants from Israel Science Foundation and Canada Institute for Health Research (CIHR). Dr. Friedman was supported by grants from European Union's Seventh Framework Program (FP7/2007-2013; grant #602102).

Peri-infarct depolarizations lead to loss of perfusion in ischaemic gyrencephalic cerebral cortex.

In the light of accumulating evidence for the occurrence of spontaneous cortical spreading depression and peri-infarct depolarizations in the human brain injured by trauma or aneurysmal subarachnoid haemorrhage, we used DC electrode recording and laser speckle imaging to study the relationship between depolarization events and perfusion in the ischaemic, gyrencephalic brain. In 14 adult male cats anaesthetized with chloralose, one cerebral hemisphere was exposed and the middle cerebral artery occluded. Surface cortical perfusion in core and penumbral territories was imaged semiquantitatively at intervals of 13 s for 4 h. Cortical surface DC potential was recorded. Time interval between changes in DC potential and in perfusion was examined, and this comparison was repeated using microelectrodes for DC potential in five similar experiments in a second laboratory. Mean pre-occlusion perfusion was 11707 +/- 4581 units (equivalent to CBF (cerebral blood flow) approximately 40.5 +/- SD 14.4 ml/100 g/min), and fell on occlusion to 5318 +/- 2916 (CBF approximately 17.1 +/- 8.3), 5291 +/- 3407 (CBF approximately 17.0 +/- 10.1), and 6711 +/- 3271 (CBF approximately 22.2 +/- 9.6), quickly recovering to 8704 +/- 4581 (CBF approximately 29.5 +/- 14.4), 9741 +/- 4499 (CBF approximately 33.3 +/- 14.1) and 10 314 +/- 3762 (CBF approximately 35.4 +/- 11.4) on the core, intermediate and outer penumbral gyri, respectively. Mean perfusion later fell secondarily on core and intermediate gyri but, overall, was preserved on the outer (upper level of perfusion) gyrus during the period of observation. Pattern and severity of transient changes in perfusion associated with depolarization events varied with gyral location; falls in perfusion were sometimes profound and irreversible, and followed rather than preceded depolarization. In this model of occlusive stroke, reductions in perfusion linked to peri-infarct depolarization events contribute to secondary deterioration in penumbral areas. The findings suggest that such events play a central rather than a subsidiary role in cerebral infarction in the gyrencephalic brain.

Identification and clinical impact of impaired cerebrovascular autoregulation in patients with malignant middle cerebral artery infarction.

BACKGROUND AND PURPOSE: To study cerebrovascular autoregulation and its impact on clinical course in patients with impending malignant middle cerebral artery infarction, we used invasive multimodal neuromonitoring, including measurement of cerebral perfusion pressure, tissue oxygen pressure, and microdialysis. METHODS: Fifteen patients with a stroke that involved >50% of the middle cerebral artery territory were included. Probes were placed into the ipsilateral frontal lobe. Autoregulation was assessed by calculation of the cerebral perfusion pressure-oxygen reactivity index (COR) and the correlation coefficient (R) of cerebral perfusion pressure and tissue oxygen pressure at 24 and 72 hours after stroke. RESULTS: COR and R at 24 hours after stroke were higher in the 8 patients with a malignant course (ie, massive edema formation) compared with the 7 patients with a benign course (COR, 1.99+/-1.46 versus 0.68+/-0.29; R, 0.49+/-0.28 versus 0.06+/-0.31; P<0.05), indicating impaired autoregulation in the malignant course group. At 72 hours, further increases in COR and R were observed in the malignant course group in contrast to the benign course group with stable values over time (COR, 3.31+/-2.38 versus 0.75+/-0.31; R, 0.75+/-011 versus 0.36+/-0.27; P<0.05). With a COR of 0.99, a cutoff value for prediction of a malignant course was found. The lactate-pyruvate ratio was higher in patients with a malignant compared with a benign course at both time points. COR, R, and the lactate-pyruvate ratio showed significant correlations with outcome parameters as a midline shift on cranial computed tomography and score on the modified Rankin scale after 3 months. CONCLUSIONS: We found early impairment of cerebrovascular autoregulation in peri-infarct tissue of patients who developed malignant brain edema, whereas autoregulation was preserved in patients with a benign course. Impaired cerebral autoregulation seems to play a key role for development of a malignant course and might serve as a predictive marker. Impaired cerebral autoregulation also accentuates the need for consequent adjustment of cerebral perfusion pressure in patients with impaired autoregulation.

Large field-of-view movement-compensated intrinsic optical signal imaging for the characterization of the haemodynamic response to spreading depolarizations in large gyrencephalic brains.

Haemodynamic responses to spreading depolarizations (SDs) have an important role during the development of secondary brain damage. Characterization of the haemodynamic responses in larger brains, however, is difficult due to movement artefacts. Intrinsic optical signal (IOS) imaging, laser speckle flowmetry (LSF) and electrocorticography were performed in different configurations in three groups of in total 18 swine. SDs were elicited by topical application of KCl or occurred spontaneously after middle cerebral artery occlusion. Movement artefacts in IOS were compensated by an elastic registration algorithm during post-processing. Using movement-compensated IOS, we were able to differentiate between four components of optical changes, corresponding closely with haemodynamic variations measured by LSF. Compared with ECoG and LSF, our setup provides higher spatial and temporal resolution, as well as a better signal-to-noise ratio. Using IOS alone, we could identify the different zones of infarction in a large gyrencephalic middle cerebral artery occlusion pig model. We strongly suggest movement-compensated IOS for the investigation of the role of haemodynamic responses to SDs during the development of secondary brain damage and in particular to examine the effect of potential therapeutic interventions in gyrencephalic brains.

Standard-sampling microdialysis and spreading depolarizations in patients with malignant hemispheric stroke.

Spreading depolarizations (SD) occur in high frequency in patients with malignant hemispheric stroke (MHS). Experimentally, SDs cause marked increases in glutamate and lactate, whereas glucose decreases. Here, we studied extracellular brain glutamate, glucose, lactate, pyruvate and the lactate/pyruvate ratio in relationship to SDs after MHS. We inserted two microdialysis probes in peri-infarct tissue at 5 and 15 mm to the infarct in close proximity to a subdural electrode strip. During 2356.6 monitoring hours, electrocorticography (ECoG) revealed 697 SDs in 16 of 18 patients. Ninety-nine SDs in electrically active tissue (spreading depressions, SDd) were single (SDds) and 485 clustered (SDdc), whereas 10 SDs with at least one electrode in electrically inactive tissue (isoelectric SDs, SDi) were single (SDis) and 103 clustered (SDic). More SDs and a significant number of clustered SDs occurred during the first 36 h post-surgery when glutamate was significantly elevated (> 100 µM). In a grouped analysis, we observed minor glutamate elevations with more than two SDs per hour. Glucose slightly decreased during SDic at 5 mm from the infarct. Directions of SD-related metabolic changes correspond to the experimental setting but the long sampling time of standard microdialysis precludes a more adequate account of the dynamics revealed by ECoG.

The continuum of spreading depolarizations in acute cortical lesion development: Examining Leão's legacy.

A modern understanding of how cerebral cortical lesions develop after acute brain injury is based on Aristides Leão's historic discoveries of spreading depression and asphyxial/anoxic depolarization. Treated as separate entities for decades, we now appreciate that these events define a continuum of spreading mass depolarizations, a concept that is central to understanding their pathologic effects. Within minutes of acute severe ischemia, the onset of persistent depolarization triggers the breakdown of ion homeostasis and development of cytotoxic edema. These persistent changes are diagnosed as diffusion restriction in magnetic resonance imaging and define the ischemic core. In delayed lesion growth, transient spreading depolarizations arise spontaneously in the ischemic penumbra and induce further persistent depolarization and excitotoxic damage, progressively expanding the ischemic core. The causal role of these waves in lesion development has been proven by real-time monitoring of electrophysiology, blood flow, and cytotoxic edema. The spreading depolarization continuum further applies to other models of acute cortical lesions, suggesting that it is a universal principle of cortical lesion development. These pathophysiologic concepts establish a working hypothesis for translation to human disease, where complex patterns of depolarizations are observed in acute brain injury and appear to mediate and signal ongoing secondary damage.

Recording, analysis, and interpretation of spreading depolarizations in neurointensive care: Review and recommendations of the COSBID research group.

Spreading depolarizations (SD) are waves of abrupt, near-complete breakdown of neuronal transmembrane ion gradients, are the largest possible pathophysiologic disruption of viable cerebral gray matter, and are a crucial mechanism of lesion development. Spreading depolarizations are increasingly recorded during multimodal neuromonitoring in neurocritical care as a causal biomarker providing a diagnostic summary measure of metabolic failure and excitotoxic injury. Focal ischemia causes spreading depolarization within minutes. Further spreading depolarizations arise for hours to days due to energy supply-demand mismatch in viable tissue. Spreading depolarizations exacerbate neuronal injury through prolonged ionic breakdown and spreading depolarization-related hypoperfusion (spreading ischemia). Local duration of the depolarization indicates local tissue energy status and risk of injury. Regional electrocorticographic monitoring affords even remote detection of injury because spreading depolarizations propagate widely from ischemic or metabolically stressed zones; characteristic patterns, including temporal clusters of spreading depolarizations and persistent depression of spontaneous cortical activity, can be recognized and quantified. Here, we describe the experimental basis for interpreting these patterns and illustrate their translation to human disease. We further provide consensus recommendations for electrocorticographic methods to record, classify, and score spreading depolarizations and associated spreading depressions. These methods offer distinct advantages over other neuromonitoring modalities and allow for future refinement through less invasive and more automated approaches.

Peri-infarct depolarizations reveal penumbra-like conditions in striatum.

Spreading depression-like peri-infarct depolarizations not only characterize but also worsen penumbra conditions in cortical border zones of experimental focal ischemia. We intended to investigate the relevance of ischemic depolarization in subcortical regions of ischemic territories. Calomel electrodes measured DC potentials simultaneously in the lateral and medial portions of the caudate nucleus (CN) of 11 anesthetized cats after permanent occlusion of the middle cerebral artery. Additionally, platinum electrodes measured cerebral blood flow (CBF) in the CN, and laser Doppler probes CBF in the cortex. Depolarizations (negative DC shifts >10 mV) were obtained in 10 of 11 cats. Further differentiation revealed that short-lasting spreading depression-like depolarizations (SDs; 5 of 10 cats: 5.24 +/- 1.22 min total duration; 23.3 +/- 4.2 mV amplitude) were predominantly found in medial and longer depolarizations (LDs; 4 of 10 cats: 64.7 +/- 47.5 min; 25.0 +/- 11.3 mV) in the lateral CN. Terminal depolarizations (TDs; 6 of 10 cats; without repolarization) occurred immediately after occlusion or at later stages, being then accompanied by elevations of intracranial pressure presumably inducing secondary CBF reduction. CBF tended to be lower in regions with TDs (33.3 +/- 29.9% of control) and LDs (37.3 +/- 22.8%) than in regions with SDs (51.5 +/- 48.0%). We conclude that in focal ischemia, transient peri-infarct depolarizations emerge not only in cortical but also in striatal gray matter, thereby demonstrating the existence of subcortical zones of ischemic penumbra. The generation of these ischemic depolarizations is a multifocal process possibly linked to brain swelling and intracranial pressure rise in the later course of focal ischemia, and therefore a relevant correlate of progressively worsening conditions.