Investigation of changes in body composition, metabolic profile and skeletal muscle functional capacity in ischemic stroke patients: the rationale and design of the Body Size in Stroke Study (BoSSS)

BACKGROUND

Stroke is steadily increasing in prevalence. Muscle tissue wasting and functional changes are frequently observed in stroke, but this has not been studied in detail yet. There is a lack of data to support guideline recommendations on how to target muscle wasting in stroke patients. We hypothesise that pathophysiological metabolic profiles and muscle functional and structural impairment are developing in stroke patients, which are associated with stroke severity and outcome after stroke.

METHODS

The Body Size in Stroke Study (BoSSS) is a prospective, longitudinal observation study that will explore associations between the metabolic profile, body tissue wasting and particular metabolic and functional changes in skeletal muscle tissue in stroke patients. Consecutive patients with acute stroke (n = 150) will be enrolled due to lacunar or territorial ischemic infarct in the area of the middle cerebral artery. Patients will be studied at annual intervals after 12 and 24 months. For comparison, healthy controls of similar age and patients with chronic heart failure will be used as control groups. The main objective is to study changes in body composition in stroke patients. Secondary, the study will focus on changes in insulin sensitivity of adipose tissue and skeletal muscle. Furthermore, measurements of endothelial function and peripheral blood flow will provide insight in the vascular regulation in stroke patients.

CONCLUSION

This study will be the largest observational study providing insights into the metabolic and functional changes of muscle tissue in patients with acute ischemic stroke. The new data will increase our understanding of the pathophysiologic tissue wasting in stroke disease and help to develop new therapeutic strategies.

Laminar infarcts in clinical routine: a prospective analysis in standard stroke unit patients

The present study aimed to investigate prospectively the frequency of laminar infarcts (LI) within a standard stroke unit population. Laminar infarcts follow neuroanatomical borders rather than the vascular architecture. The LI are rarely noticed in clinical routine because they are typically not detected by computed tomography. As there is a lack of systemic studies about this specific infarct pattern, little is known about their frequency, clinical characteristics or pathophysiological mechanisms. Consecutive acute ischemic stroke unit patients were prospectively enrolled during a 12 month period. The LI were defined as ischemic lesions following the gyral anatomy of the cerebral cortex. The clinical assessment included a standardized questionnaire, clinical syndromes and standard diagnostic results. There were 491 consecutive ischemic stroke patients enrolled (243 female, mean age 75 ± 12 years). The MRI revealed no laminar lesion crossing vascular territories and 28 patients with LI non-crossing vascular territories (7 %). According to the TOAST classification, 61 % of LI were classified as stroke of undetermined etiology (TOAST V) including 46 % with completed evaluation (TOAST Vb). In contrast to these findings, only 20 % of the whole study cohort with non-laminar infarcts were classified as TOAST V. The results indicate that LI are rare. In clinical routine, patients with LI require particular attention. Within the TOAST classification, this specific infarct pattern seems to be underrepresented.

Propagation of cortical spreading depolarization in the human cortex after malignant stroke

OBJECTIVE

To investigate hemodynamic response pattern and spatiotemporal propagation of cortical spreading depolarization in the peri-infarct region of malignant hemispheric stroke.

METHODS

In this prospective observational case study we used intraoperative laser speckle technology to measure cerebral blood flow in patients with malignant hemispheric stroke. Additionally, postoperative occurrence of cortical spreading depolarization was monitored using a subdural recording strip for electrocorticography and infarct progression was assessed by serial MRI.

RESULTS

In 7 of 20 patients, 19 blood flow changes typical of cortical spreading depolarizations occurred during a 20-minute period. Thirteen events were characterized by increase, 2 by biphasic response, and 4 by decrease of blood flow. Propagation velocity ranged from 1.7 to 9.2 mm/min and propagation area from 0.1 to 4.8 cm(2). Intrinsic optical signal alterations preceded and low-frequency vascular fluctuations were suppressed during the hemodynamic responses. A mean number of 56 ± 82 cortical spreading depolarizations per patient was recorded and a mean infarct progression of 30 ± 13 cm(3) was detected in 5 of 7 patients.

CONCLUSIONS

We visualize the spatiotemporal propagation of spreading depolarizations in the human cerebral cortex intraoperatively. In patients with focal ischemia, multiple cortical spreading depolarizations with either hyperemic or hypoemic flow responses occurred. Our data suggest that, in patients with focal ischemia, cortical spreading depolarizations are associated with both unfavorable and protective hemodynamic responses.

Electrochemical Failure of the Brain Cortex Is More Deleterious When it Is Accompanied by Low Perfusion

Background and Purpose—

Clinical and experimental evidence suggests that spreading depolarization facilitates neuronal injury when its duration exceeds a certain time point, termed commitment point. We here investigated whether this commitment point is shifted to an earlier period, when spreading depolarization is accompanied by a perfusion deficit.

Methods—

Electrophysiological and cerebral blood flow changes were studied in a rat cranial window model followed by histological and immunohistochemical analyses of cortical damage.

Results—

In group 1, brain topical application of artificial cerebrospinal fluid (ACSF) with high K + concentration ([K + ] ACSF ) for 1 hour allowed us to induce a depolarizing event of fixed duration with cerebral blood flow fluctuations around the baseline (short-lasting initial hypoperfusions followed by hyperemia). In group 2, coapplication of the NO-scavenger hemoglobin ([Hb] ACSF ) with high [K + ] ACSF caused a depolarizing event of similar duration, to which a severe perfusion deficit was coupled (=spreading ischemia). In group 3, intravenous coadministration of the L-type calcium channel antagonist nimodipine with brain topical application of high [K + ] ACSF /[Hb] ACSF caused spreading ischemia to revert to spreading hyperemia. Whereas scattered neuronal injury occurred in the superficial cortical layers in the window areas of groups 1 and 3, necrosis of all layers with partial loss of the tissue texture and microglial activation were observed in group 2.

Conclusions—

The results suggest that electrochemical failure of the cortex is more deleterious when it is accompanied by low perfusion. Thus, the commitment point of the cortex is not a universal value but depends on additional factors, such as the level of perfusion.

Impaired neurovascular coupling to ictal epileptic activity and spreading depolarization in a patient with subarachnoid hemorrhage: possible link to blood-brain barrier dysfunction

Spreading depolarization describes a sustained neuronal and astroglial depolarization with abrupt ion translocation between intraneuronal and extracellular space leading to a cytotoxic edema and silencing of spontaneous activity. Spreading depolarizations occur abundantly in acutely injured human brain and are assumed to facilitate neuronal death through toxic effects, increased metabolic demand, and inverse neurovascular coupling. Inverse coupling describes severe hypoperfusion in response to spreading depolarization. Ictal epileptic events are less frequent than spreading depolarizations in acutely injured human brain but may also contribute to lesion progression through increased metabolic demand. Whether abnormal neurovascular coupling can occur with ictal epileptic events is unknown. Herein we describe a patient with aneurysmal subarachnoid hemorrhage in whom spreading depolarizations and ictal epileptic events were measured using subdural opto-electrodes for direct current electrocorticography and regional cerebral blood flow recordings with laser-Doppler flowmetry. Simultaneously, changes in tissue partial pressure of oxygen were recorded with an intraparenchymal oxygen sensor. Isolated spreading depolarizations and clusters of recurrent spreading depolarizations with persistent depression of spontaneous activity were recorded over several days followed by a status epilepticus. Both spreading depolarizations and ictal epileptic events where accompanied by hyperemic blood flow responses at one optode but mildly hypoemic blood flow responses at another. Of note, quantitative analysis of Gadolinium-diethylene-triamine-pentaacetic acid (DTPA)-enhanced magnetic resonance imaging detected impaired blood-brain barrier integrity in the region where the optode had recorded the mildly hypoemic flow responses. The data suggest that abnormal flow responses to spreading depolarizations and ictal epileptic events, respectively, may be associated with blood-brain barrier dysfunction.

Blood-brain barrier opening to large molecules does not imply blood-brain barrier opening to small ions

Neuroimaging of exogenous tracer extravasation has become the technique of choice in preclinical and clinical studies of blood-brain barrier permeability. Such tracers have a larger molecular weight than small ions, neurotransmitters and many drugs. Therefore, it is assumed that tracer extravasation indicates both permeability to these and the cancelation of the electrical polarization across the barrier. Electrophysiological anomalies following intracarotideal administration of dehydrocholate, a bile salt causing extravasation of the albumin-binding tracer Evans blue, seemingly supported this. By contrast, electron microscopic studies suggested a different hierarchical pattern of blood-brain barrier dysfunction, a milder degree of impairment being characterized by increased function of the transcellular pathway and a severe degree by opening of the tight junctions. This would imply that the extravasation of macromolecules can occur before disruption of the electrical barrier. However, functional evidence for this has been lacking. Here, we further investigated the electrophysiological anomalies following intracarotideal application of dehydrocholate in rats and found that it caused focal cerebral ischemia by middle cerebral artery thrombosis, the electrophysiological recordings being characteristic of long-lasting spreading depolarization. These observations indicated that intracarotideal dehydrocholate is not a suitable model to study the isolated dysfunction of the blood-brain barrier. Second, we studied the topical application of dehydrocholate to the brain and the application of mannitol into the carotid artery. In both models, we found significant extravasation of Evans blue but no changes in either extracellular potassium or the CO(2)-dependent intracortical direct current deflection. The latter is assumed to depend on the proton gradient across the barrier in rats which we confirmed in additional experiments in vivo and in vitro. The stability of the extracellular potassium concentration and the CO(2)-dependent direct current deflection are two functional tests which indicate the integrity of the electrical barrier. Hence, our results provide functional evidence that the blood-brain barrier opening to large molecules does not necessarily imply the opening to small ions consistent with the hierarchy of damage in the previous electron microscopic studies.

Criteria for the diagnosis of noninfectious and infectious complications after aneurysmal subarachnoid hemorrhage in DISCHARGE-1

Patients with aneurysmal subarachnoid hemorrhage (aSAH) frequently develop secondary noninfectious and infectious complications that have an important impact on clinical course and outcome. We here report on criteria for the diagnosis of the most important complications after aSAH based on clinical status, neuroimaging, and laboratory tests, including cerebrospinal fluid parameters. These criteria will be used for a retrospective analysis of aSAH patients who were recruited at the Charité Berlin for the CoOperative Study on Brain Injury Depolarisations (COSBID) before the Depolarisations in Ischaemia after Subarachnoid Haemorrhage-1 (DISCHARGE-1) trial started. Moreover, they serve for the survey of complications in DISCHARGE-1. We also report on a customized, Web-based database that has been developed for the documentation of the clinical course after aSAH. This database is used for the COSBID outcome study on aSAH and for DISCHARGE-1.

Cerebral glucose and spreading depolarization in patients with aneurysmal subarachnoid hemorrhage

The pathogenesis of delayed cerebral ischemia (DCI) is multifactorial and not completely elucidated. Our objective was to determine if episodes of spreading depolarization (SD) are reflected in compromised levels of extracellular glucose monitored by bedside microdialysis (MD) in aneurysmal subarachnoid hemorrhage (aSAH) patients. Patients with aSAH, prospectively included in the COSBID (CoOperative Study on Brain Injury Depolarisations) protocol (Berlin, Heidelberg), had hourly monitoring of cerebral glucose by MD and in parallel electrocorticographic (ECoG) monitoring for SD detection on day of admission until days 10-14 after aSAH. Cerebral MD probes were placed in the vascular territory at risk for DCI. Twenty-one aSAH patients (53.3 ± 9.1 years; mean ± standard deviation), classified according to the World Federation of Neurosurgical Societies (WFNS) in low (I-III, 11) and high (IV-V, 10) grades, were studied. Of these, 13 patients (62%) presented with DCI. Median glucose was 1.48 (0.00-8.79). Median occurrence of SD was 7 (0-66)/patients. High WFNS grade (WFNS grades IV-V) patients had more SDs (p = 0.027), while the overall glucose level did not differ. In high-grade SAH patients, SDs were more frequent. Individually, the occurrence of SD was not linked to local deviations (neither high nor low) from the LOWESS (locally weighted scatterplot smoothing) trend curve for extracellular glucose concentrations. Rapid-sampling MD techniques and analyses of SD clusters may elucidate more detail of the relationship between SD and brain energy metabolism.

Full-band electrocorticography of spreading depolarizations in patients with aneurysmal subarachnoid hemorrhage

Cortical spreading depolarizations (CSDs) are a pathologic mechanism occurring in patients with aneurysmal subarachnoid hemorrhage and may contribute to delayed cerebral ischemia. We conducted a pilot study to determine the durations of depolarizations as measured by the negative direct current shifts in electrocorticography. Cortical electrode strips were placed in six patients (aged 35-63 years, Fisher grade 4, World Federation of Neurosurgical Societies [WFNS] 3-4) with ruptured aneurysms treated by clip ligation. Full-band electrocorticography was performed by direct current amplification (g.USBamp, Guger Tec, Graz, Austria) with ±250-mV range, 24-bit digitization, and recording/display with a customized BCI2000 platform. We recorded 191 CSDs in 4 patients, and direct current shifts of CSD (n = 403) were measured at 20 electrodes. Amplitudes were 7.2 mV (median; quartiles 6.2, 7.9), and durations were 2 min 14 s (1:53, 2:45). Ten direct current shifts in two patients with delayed infarcts were longer than 10 min, ranging up to 28 min. Taken together with previous studies, results suggest a threshold of 3-3.5 min to distinguish a normally distributed class of short CSDs with spreading hyperemia from prolonged CSDs with initial spreading ischemia. Results further demonstrate the clinical feasibility of direct current electrocorticography to monitor CSDs and assess their role in the pathology and management of subarachnoid hemorrhage.

Clusters of spreading depolarizations are associated with disturbed cerebral metabolism in patients with aneurysmal subarachnoid hemorrhage

BACKGROUND AND PURPOSE

We studied the dynamics of extracellular brain tissue concentrations of glucose, lactate, pyruvate, and glutamate during the occurrence of spreading depolarizations (SDs) in patients with aneurysmal subarachnoid hemorrhage.

METHODS

In this prospective observational study, patients with aneurysmal subarachnoid hemorrhage received multimodal cerebral monitoring, including intracranial pressure, cerebral microdialysis, and subdural electrocorticography.

RESULTS

Seven of the 17 recruited patients had intracerebral hemorrhage, acute ischemia and severe brain oedema leading to acute ischemic neurological deficits associated with early disturbance of metabolism at the recording site. They displayed a total of 130 SDs. The remaining 10 patients without acute ischemic neurological deficits exhibited 138 single SDs and 68 SDs in clusters. In patients without acute ischemic neurological deficits, clustered SDs were associated with a significant transient decrease in glucose and increase in lactate compared with baseline during the first 140 minutes after SDs. Moreover, the number of clustered SDs correlated with the outcome (R=-0.659; P<0.01).

CONCLUSIONS

SDs can propagate in nonischemic human brain tissue. Clusters of SDs are related to metabolic changes suggestive of ongoing secondary damage in primarily nonischemic brain tissue.

Peri-infarct blood-brain barrier dysfunction facilitates induction of spreading depolarization associated with epileptiform discharges

Recent studies showed that spreading depolarizations (SDs) occurs abundantly in patients following ischemic stroke and experimental evidence suggests that SDs recruit tissue at risk into necrosis. We hypothesized that BBB opening with consequent alterations of the extracellular electrolyte composition and extravasation of albumin facilitates generation of SDs since albumin mediates an astrocyte transcriptional response with consequent disturbance of potassium and glutamate homeostasis. Here we show extravasation of Evans blue-albumin complex into the hippocampus following cortical photothrombotic stroke in the neighboring neocortex. Using extracellular field potential recordings and exposure to serum electrolytes we observed spontaneous SDs in 80% of hippocampal slices obtained from rats 24 h after cortical photothrombosis. Hippocampal exposure to albumin for 24 h through intraventricular application together with serum electrolytes lowered the threshold for the induction of SDs in most slices irrespective of the pathway of stimulation. Exposing acute slices from naive animals to albumin led also to a reduced SD threshold. In albumin-exposed slices the onset of SDs was usually associated with larger stimulus-induced accumulation of extracellular potassium, and preceded by epileptiform activity, which was also observed during the recovery phase of SDs. Application of ifenprodil (3 μM), an NMDA-receptor type 2 B antagonist, blocked stimulus dependent epileptiform discharges and generation of SDs in slices from animals treated with albumin in-vivo. We suggest that BBB opening facilitates the induction of peri-infarct SDs through impaired homeostasis of K+.

Peri-infarct flow transients predict outcome in rat focal brain ischemia

Spreading depolarizations are accompanied by transient changes in cerebral blood flow (CBF). In a post hoc analysis of previously studied control rats we analyzed CBF time courses after middle cerebral artery occlusion in the rat in order to test whether intra-ischemic flow, reperfusion, and different parameters of peri-infarct flow transients (PIFTs) (amplitude, number) can predict outcome. Sprague-Dawley rats anesthetized with either halothane (n=23) or isoflurane (n=32) underwent 90-min filament occlusion of the middle cerebral artery followed by 72 h of reperfusion. The infarct size was determined by 2,3,5-triphenyltetrazolium chloride staining. Relative CBF changes were monitored by laser Doppler flowmetry at 4-5 mm lateral, and 1-2mm posterior to Bregma. An additional filament occlusion study (n=12) was performed to validate that PIFTs were coupled to direct current shifts of spreading depolarization. The PIFT-direct current shift study revealed that every PIFT was associated with a negative direct current shift typical of spreading depolarization. Post-hoc analysis showed that the number of PIFTs, especially with the combination of intra-ischemic level of flow, can predict the development of cortical infarcts. These findings show that PIFTs can serve as an early biomarker in predicting outcome in preclinical animal studies.

Is spreading depolarization characterized by an abrupt, massive release of gibbs free energy from the human brain cortex?

In the evolution of the cerebral cortex, the sophisticated organization in a steady state far away from thermodynamic equilibrium has produced the side effect of two fundamental pathological network events: ictal epileptic activity and spreading depolarization. Ictal epileptic activity describes the partial disruption, and spreading depolarization describes the near-complete disruption of the physiological double Gibbs-Donnan steady state. The occurrence of ictal epileptic activity in patients has been known for decades. Recently, unequivocal electrophysiological evidence has been found in patients that spreading depolarizations occur abundantly in stroke and brain trauma. The authors propose that the ion changes can be taken to estimate relative changes in Gibbs free energy from state to state. The calculations suggest that in transitions from the physiological state to ictal epileptic activity to spreading depolarization to death, the cortex releases Gibbs free energy in a stepwise fashion. Spreading depolarization thus appears as a twilight state close to death. Consistently, electrocorticographic recordings in the core of focal ischemia or after cardiac arrest display a smooth transition from the initial spreading depolarization component to the later ultraslow negative potential, which is assumed to reflect processes in cellular death.

Effect of analgesics and sedatives on the occurrence of spreading depolarizations accompanying acute brain injury

Spreading depolarizations are waves of mass neuronal and glial depolarization that propagate across the injured human cortex. They can occur with depression of neuronal activity as spreading depressions or isoelectric spreading depolarizations on a background of absent or minimal electroencephalogram activity. Spreading depolarizations are characterized by the loss of neuronal ion homeostasis and are believed to damage functional neurons, leading to neuronal necrosis or neurological degeneration and poor outcome. Analgesics and sedatives influence activity-dependent neuronal ion homeostasis and therefore represent potential modulators of spreading depolarizations. In this exploratory retrospective international multicentre analysis, we investigated the influence of midazolam, propofol, fentanyl, sufentanil, ketamine and morphine on the occurrence of spreading depolarizations in 115 brain-injured patients. A surface electrode strip was placed on the cortex, and continuous electrocorticographical recordings were obtained. We used multivariable binary logistic regression to quantify associations between the investigated drugs and the hours of electrocorticographical recordings with and without spreading depolarizations or clusters of spreading depolarizations. We found that administration of ketamine was associated with a reduction of spreading depolarizations and spreading depolarization clusters (P < 0.05). Midazolam anaesthesia, in contrast, was associated with an increased number of spreading depolarization clusters (P < 0.05). By using a univariate odds ratio analysis, we also found a significant association between ketamine administration and reduced occurrence of isoelectric spreading depolarizations in patients suffering from traumatic brain injury, subarachnoid haemorrhage and malignant hemispheric stroke (P < 0.05). Our findings suggest that ketamine-or another N-methyl-d-aspartate receptor antagonist-may represent a viable treatment for patients at risk for spreading depolarizations. This hypothesis will be tested in a prospective study.

Correlates of spreading depolarization in human scalp electroencephalography

It has been known for decades that suppression of spontaneous scalp electroencephalographic activity occurs during ischaemia. Trend analysis for such suppression was found useful for intraoperative monitoring during carotid endarterectomy, or as a screening tool to detect delayed cerebral ischaemia after aneurismal subarachnoid haemorrhage. Nevertheless, pathogenesis of such suppression of activity has remained unclear. In five patients with aneurismal subarachnoid haemorrhage and four patients with decompressive hemicraniectomy after malignant hemispheric stroke due to middle cerebral artery occlusion, we here performed simultaneously full-band direct and alternating current electroencephalography at the scalp and direct and alternating current electrocorticography at the cortical surface. After subarachnoid haemorrhage, 275 slow potential changes, identifying spreading depolarizations, were recorded electrocorticographically over 694 h. Visual inspection of time-compressed scalp electroencephalography identified 193 (70.2%) slow potential changes [amplitude: −272 (−174, −375) µV (median quartiles), duration: 5.4 (4.0, 7.1) min, electrocorticography–electroencephalography delay: 1.8 (0.8, 3.5) min]. Intervals between successive spreading depolarizations were significantly shorter for depolarizations with electroencephalographically identified slow potential change [33.0 (27.0, 76.5) versus 53.0 (28.0, 130.5) min, P = 0.009]. Electroencephalography was thus more likely to display slow potential changes of clustered than isolated spreading depolarizations. In contrast to electrocorticography, no spread of electroencephalographic slow potential changes was seen, presumably due to superposition of volume-conducted electroencephalographic signals from widespread cortical generators. In two of five patients with subarachnoid haemorrhage, serial magnetic resonance imaging revealed large delayed infarcts at the recording site, while electrocorticography showed clusters of spreading depolarizations with persistent depression of spontaneous activity. Alternating current electroencephalography similarly displayed persistent depression of spontaneous activity, and direct current electroencephalography slow potential changes riding on a shallow negative ultraslow potential. Isolated spreading depolarizations with depression of both spontaneous electrocorticographic and electroencephalographic activity displayed significantly longer intervals between successive spreading depolarizations than isolated depolarizations with only depression of electrocorticographic activity [44.0 (28.0, 132.0) min, n = 96, versus 30.0 (26.5, 51.5) min, n = 109, P = 0.001]. This suggests fusion of electroencephalographic depression periods at high depolarization frequency. No propagation of electroencephalographic depression was seen between scalp electrodes. Durations/magnitudes of isolated electroencephalographic and corresponding electrocorticographic depression periods correlated significantly. Fewer spreading depolarizations were recorded in patients with malignant hemispheric stroke but characteristics were similar to those after subarachnoid haemorrhage. In conclusion, spreading depolarizations and depressions of spontaneous activity display correlates in time-compressed human scalp direct and alternating current electroencephalography that may serve for their non-invasive detection.

Delayed cerebral ischemia and spreading depolarization in absence of angiographic vasospasm after subarachnoid hemorrhage

It has been hypothesized that vasospasm is the prime mechanism of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH). Recently, it was found that clusters of spreading depolarizations (SDs) are associated with DCI. Surgical placement of nicardipine prolonged-release implants (NPRIs) was shown to strongly attenuate vasospasm. In the present study, we tested whether SDs and DCI are abolished when vasospasm is reduced or abolished by NPRIs. After aneurysm clipping, 10 NPRIs were placed next to the proximal intracranial vessels. The SDs were recorded using a subdural electrode strip. Proximal vasospasm was assessed by digital subtraction angiography (DSA). 534 SDs were recorded in 10 of 13 patients (77%). Digital subtraction angiography revealed no vasospasm in 8 of 13 patients (62%) and only mild or moderate vasospasm in the remaining. Five patients developed DCI associated with clusters of SD despite the absence of angiographic vasospasm in three of those patients. The number of SDs correlated significantly with the development of DCI. This may explain why reduction of angiographic vasospasm alone has not been sufficient to improve outcome in some clinical studies.

Spreading depolarization, a pathophysiological mechanism of stroke and migraine aura

Spreading depolarization is a mechanism of abrupt, massive ion translocation between intraneuronal and extracellular space that entails cytotoxic edema in the brain’s gray matter. It is observed in patients as a large change of the slow electrical potential. Dependent on the energy status of the tissue, spreading depolarization is either preceded by nonspreading silencing due to neuronal hyperpolarization or accompanied by spreading silencing of electrical brain activity due to a depolarization block. Nonspreading silencing seems to translate into the initial clinical symptoms of ischemic stroke and spreading silencing translates into migraine aura. Direct electrophysiological evidence exists that spreading depolarization occurs in abundance in aneurysmal subarachnoid hemorrhage, delayed ischemic stroke after subarachnoid hemorrhage, malignant hemispheric stroke, spontaneous intracerebral hemorrhage and traumatic brain injury. Indirect evidence suggests its occurrence during migraine aura. In animals, spreading depolarizations facilitate neuronal death when they invade metabolically compromised tissue, whereas they are relatively innocuous in healthy tissue. Therapies targeting spreading depolarization may potentially treat these neurological conditions.

Spreading convulsions, spreading depolarization and epileptogenesis in human cerebral cortex

Spreading depolarization of cells in cerebral grey matter is characterized by massive ion translocation, neuronal swelling and large changes in direct current-coupled voltage recording. The near-complete sustained depolarization above the inactivation threshold for action potential generating channels initiates spreading depression of brain activity. In contrast, epileptic seizures show modest ion translocation and sustained depolarization below the inactivation threshold for action potential generating channels. Such modest sustained depolarization allows synchronous, highly frequent neuronal firing; ictal epileptic field potentials being its electrocorticographic and epileptic seizure its clinical correlate. Nevertheless, Leão in 1944 and Van Harreveld and Stamm in 1953 described in animals that silencing of brain activity induced by spreading depolarization changed during minimal electrical stimulations. Eventually, epileptic field potentials were recorded during the period that had originally seen spreading depression of activity. Such spreading convulsions are characterized by epileptic field potentials on the final shoulder of the large slow potential change of spreading depolarization. We here report on such spreading convulsions in monopolar subdural recordings in 2 of 25 consecutive aneurismal subarachnoid haemorrhage patients in vivo and neocortical slices from 12 patients with intractable temporal lobe epilepsy in vitro. The in vitro results suggest that γ-aminobutyric acid-mediated inhibition protects from spreading convulsions. Moreover, we describe arterial pulse artefacts mimicking epileptic field potentials in three patients with subarachnoid haemorrhage that ride on the slow potential peak. Twenty-one of the 25 subarachnoid haemorrhage patients (84%) had 656 spreading depolarizations in contrast to only three patients (12%) with 55 ictal epileptic events isolated from spreading depolarizations. Spreading depolarization frequency and depression periods per 24 h recording episodes showed an early and a delayed peak on Day 7. Patients surviving subarachnoid haemorrhage with poor outcome at 6 months showed significantly higher total and peak numbers of spreading depolarizations and significantly longer total and peak depression periods during the electrocorticographic monitoring than patients with good outcome. In a semi-structured telephone interview 3 years after the initial haemorrhage, 44% of the subarachnoid haemorrhage survivors had developed late post-haemorrhagic seizures requiring anti-convulsant medication. In those patients, peak spreading depolarization number had been significantly higher [15.1 (11.4–30.8) versus 7.0 (0.8–11.2) events per day, P = 0.045]. In summary, monopolar recordings here provided unequivocal evidence of spreading convulsions in patients. Hence, practically all major pathological cortical network events in animals have now been observed in people. Early spreading depolarizations may indicate a risk for late post-haemorrhagic seizures.

Clinical characterization of symptomatic microangiopathic brain lesions

Background: Microangiopathic brain lesions can be separated in diffuse lesions – leukoaraiosis – and focal lesions – lacunes. Leukoaraiosis and lacunes are caused by common cerebrovascular risk factors, but whether they represent a common entity is not sufficiently investigated. The present study aimed to determine the clinical profiles associated with the extent of leukoaraiosis and lacunes. Methods: Sixty-four consecutive patients with acute microangiopathic stroke were studied. Leukoaraiosis and lacunes were stratified according to their MRI-based extent. Standardized clinical assessment included clinical syndromes, cerebrovascular risk factors, cognitive performance, retinal imaging, ultrasonography, blood, and urine parameters. Results: Different clinical profiles for leukoaraiosis and lacunes were found. Regarding leukoaraiosis, the cognitive scores (SISCO, mini mental score examination, mental examination) and the presence of hyperlipidemia decreased as the severity of leukoaraiosis increased. Univariate and multivariate analysis revealed that these cognitive score values as well as the presence of hyperlipidemia correlated significantly with no or only mild leukoaraiosis. Regarding lacunes, the percentage of migraine, previous stroke events, hydrocephalus, left ventricular hypertrophy, and a higher National Institutes of Health Stroke Scale increased as the number of lacunar lesions increased. Statistical analysis revealed that these parameters correlated not significantly with the number of lacunes. Conclusions: The findings suggests that leukoaraiosis and lacunes are different microangiopathic entities potentially requiering different treatment concepts.

Chronically epileptic human and rat neocortex display a similar resistance against spreading depolarization in vitro

BACKGROUND AND PURPOSE

Experimental and clinical evidence suggests that prolonged spreading depolarizations (SDs) are a promising target for therapeutic intervention in stroke because they recruit tissue at risk into necrosis by protracted intracellular calcium surge and massive glutamate release. Unfortunately, unlike SDs in healthy tissue, they are resistant to drugs such as N-methyl-d-aspartate-receptor antagonists. This drug resistance of SD in low perfusion areas may be due to the gradual rise of extracellular potassium before SD onset. Brain slices from patients undergoing surgery for intractable epilepsy allow for screening of drugs, targeting pharmacoresistant SDs under elevated potassium in human tissue. However, network changes associated with epilepsy may interfere with tissue susceptibility to SD. This could distort the results of pharmacological tests.

METHODS

We investigated the threshold for SD, induced by a gradual rise of potassium, in neocortex slices of patients with intractable epilepsy and of chronically epileptic rats as well as age-matched and younger control rats using combined extracellular potassium/field recordings and intrinsic optical imaging.

RESULTS

Both age and epilepsy significantly increased the potassium threshold, which was similarly high in epileptic rat and human slices (23.6±2.4 mmol/L versus 22.3±2.8 mmol/L).

CONCLUSIONS

Our results suggest that chronic epilepsy confers resistance against SD. This should be considered when human tissue is used for screening of neuroprotective drugs. The finding of similar potassium thresholds for SD in epileptic human and rat neocortex challenges previous speculations that the resistance of the human brain against SD is markedly higher than that of the rodent brain.

Report of selective cortical infarcts in the primate clot model of vasospasm after subarachnoid hemorrhage

BACKGROUND

In human autopsy studies, 70% to 80% of patients with aneurysmal subarachnoid hemorrhage (SAH) showed infarcts in cerebral cortex covered by subarachnoid blood. Thus far, no animal model of SAH is known to produce this peculiar infarct pattern, and its pathogenesis remains enigmatic.

OBJECTIVE

To investigate whether such infarcts occur in the clot model of SAH in primates.

METHODS

We performed a retrospective pathological review of 16 primate brains. In 13 cynomolgus monkeys, a blood clot was placed around the middle cerebral artery after additional removal of the arachnoid membrane from the basal surface of the frontal and temporal cortexes. Three animals underwent sham surgery without placement of a blood clot (controls). The brains were harvested between days 1 and 28 after SAH and examined by a neuropathologist blinded to study group.

RESULTS

We identified 2 types of cortical infarcts. A band of selective cortical laminar necrosis parallel to the cortical surface ("horizontal") was found in 5 animals. The second category of cortical lesions had a "vertical" extension. It included wedge-shaped (n = 2) or pillarlike (n = 2) necrosis. Both horizontal and vertical infarcts were located exclusively in areas adjacent to subarachnoid blood. The presence of a cortical infarct did not correlate with the degree of middle cerebral artery vasospasm (r2 = .24, P = .13).

CONCLUSION

The presence of cortical infarcts suggests that a modified nonhuman primate model of SAH is suitable to examine the pathogenesis of proximal vasospasm and permits investigation of cortical lesions similar to those reported in patients after SAH. Furthermore, it indicates that direct effects of the blood clot on the brain and microcirculation contribute to the development of cortical infarcts after SAH.

Spreading depolarizations have prolonged direct current shifts and are associated with poor outcome in brain trauma

Cortical spreading depolarizations occur spontaneously after ischaemic, haemorrhagic and traumatic brain injury. Their effects vary spatially and temporally as graded phenomena, from infarction to complete recovery, and are reflected in the duration of depolarization measured by the negative direct current shift of electrocorticographic recordings. In the focal ischaemic penumbra, peri-infarct depolarizations have prolonged direct current shifts and cause progressive recruitment of the penumbra into the core infarct. In traumatic brain injury, the effects of spreading depolarizations are unknown, although prolonged events have not been observed in animal models. To determine whether detrimental penumbral-type depolarizations occur in human brain trauma, we analysed electrocorticographic recordings obtained by subdural electrode-strip monitoring during intensive care. Of 53 patients studied, 10 exhibited spreading depolarizations in an electrophysiologic penumbra (i.e. isoelectric cortex with no spontaneous activity). All 10 patients (100%) with isoelectric spreading depolarizations had poor outcomes, defined as death, vegetative state, or severe disability at 6 months. In contrast, poor outcomes were observed in 60% of patients (12/20) who had spreading depolarizations with depression of spontaneous activity and only 26% of patients (6/23) who had no depolarizations (χ2, P<0.001). Spontaneous electrocorticographic activity and direct current shifts of depolarizations were further examined in nine patients. Direct current shift durations (n=295) were distributed with a significant positive skew (range 0:51-16:19 min:s), evidencing a normally distributed group of short events and a sub-group of prolonged events. Prolonged direct current shifts were more commonly associated with isoelectric depolarizations (median 2 min 36 s), whereas shorter depolarizations occurred with depression of spontaneous activity (median 2 min 10 s; P<0.001). In the latter group, direct current shift durations correlated with electrocorticographic depression periods, and were longer when preceded by periodic epileptiform discharges than by continuous delta (0.5-4.0 Hz) or higher frequency activity. Prolonged direct current shifts (>3 min) also occurred mainly within temporal clusters of events. Our results show for the first time that spreading depolarizations are associated with worse clinical outcome after traumatic brain injury. Furthermore, based on animal models of brain injury, the prolonged durations of depolarizations raise the possibility that these events may contribute to maturation of cortical lesions. Prolonged depolarizations, measured by negative direct current shifts, were associated with (i) isoelectricity or periodic epileptiform discharges; (ii) prolonged depression of spontaneous activity and (iii) occurrence in temporal clusters. Depolarizations with these characteristics are likely to reflect a worse prognosis.

The gamut of blood flow responses coupled to spreading depolarization in rat and human brain: from hyperemia to prolonged ischemia

Cortical spreading depolarizations (SD) have been shown to occur frequently in patients with aneurysmal subarachnoid hemorrhage (SAH) and are associated with delayed ischemic brain damage. In animal models the link between SD and cell damage is the microvascular spasm coupled to the passage of SDs, resulting in spreading ischemia. Here we compared the hemodynamic changes induced by SD between human and rat cerebral cortex. Specifically, we addressed the question, whether the full spectrum of regional cerebral blood flow (rCBF) responses to SD is found in the human brain in a similar fashion to animal models. SDs were identified by slow potential changes in electrocorticographic recordings and the rCBF response profiles and magnitudes were analyzed. We found a large variability of rCBF changes concomitant to SDs in rat and in human recordings. The spectrum ranged from normal hyperemic responses to prolonged cortical spreading ischemia with intermediate forms characterized by biphasic (hypoemic-hyperemic) responses. The bandwidths of rCBF responses were comparable and the relative response magnitudes of hypo- and hyperperfusion phases did not differ significantly between rats and humans. The correspondence of the rCBF response spectrum to SD between human and animal brain underscores the importance of animal models to learn more about the mechanisms underlying the early and delayed pathological sequelae of SAH.

Endothelin-1(1-31) induces spreading depolarization in rats

BACKGROUND

The vasoconstrictor endothelin-1(1-21) (ET-1) seems to induce cerebral vasospasm after aneurismal subarachnoid hemorrhage (aSAH). Moreover, ET-1 causes spreading depolarization (SD) via vasoconstriction/ischemia. ET-1(1-31) is an alternate metabolic intermediate in the generation of ET-1. Our aim was to investigate whether endothelin-1(1-31) causes SD in a similar fashion to ET-1.

METHOD

Increasing concentrations of either ET-1, ET-1(1-31) or vehicle were brain topically applied in 29 rats. Each concentration was superfused for one hour while regional cerebral blood flow (rCBF) and direct current electrocorticogram (DC-ECoG) were recorded.

FINDINGS

In response to the highest concentration of 10(-6) M, all animals of both ET groups developed typical SD. At concentrations below 10(-6) M only ET-1 induced SD (n=14 of 19 rats). Thus, the efficacy of ET-1(1-31) to induce SD was significantly lower (P<0.001, two-tailed Fisher's Exact Test).

CONCLUSIONS

Our findings suggest that ET-1(1-31) less potently induces SD compared to ET-1 which implicates that it is a less potent vasoconstrictor. Speculatively, it could be interesting to shift the metabolic pathway towards the alternate intermediate ET-1(1-31) after aSAH as an alternative strategy to ETA receptor inhibition. This could decrease ET-induced vasoconstriction and SD generation while a potentially beneficial basal ETA receptor activation is maintained.