Diaschisis with cerebral infarction

Contralateral Hemispheric Cerebral Blood Flow Measured With Arterial Spin Labeling Can Predict Outcome in Acute Stroke

Background and Purpose- Imaging is frequently used to select acute stroke patients for intra-arterial therapy. Quantitative cerebral blood flow can be measured noninvasively with arterial spin labeling magnetic resonance imaging. Cerebral blood flow levels in the contralateral (unaffected) hemisphere may affect capacity for collateral flow and patient outcome. The goal of this study was to determine whether higher contralateral cerebral blood flow (cCBF) in acute stroke identifies patients with better 90-day functional outcome. Methods- Patients were part of the prospective, multicenter iCAS study (Imaging Collaterals in Acute Stroke) between 2013 and 2017. Consecutive patients were enrolled after being diagnosed with anterior circulation acute ischemic stroke. Inclusion criteria were ischemic anterior circulation stroke, baseline National Institutes of Health Stroke Scale score ≥1, prestroke modified Rankin Scale score ≤2, onset-to-imaging time <24 hours, with imaging including diffusion-weighted imaging and arterial spin labeling. Patients were dichotomized into high and low cCBF groups based on median cCBF. Outcomes were assessed by day-1 and day-5 National Institutes of Health Stroke Scale; and day-30 and day-90 modified Rankin Scale. Multivariable logistic regression was used to test whether cCBF predicted good neurological outcome (modified Rankin Scale score, 0-2) at 90 days. Results- Seventy-seven patients (41 women) met the inclusion criteria with median (interquartile range) age of 66 (55-76) yrs, onset-to-imaging time of 4.8 (3.6-7.7) hours, and baseline National Institutes of Health Stroke Scale score of 13 (9-20). Median cCBF was 38.9 (31.2-44.5) mL per 100 g/min. Higher cCBF predicted good outcome at day 90 (odds ratio, 4.6 [95% CI, 1.4-14.7]; P=0.01), after controlling for baseline National Institutes of Health Stroke Scale, diffusion-weighted imaging lesion volume, and intra-arterial therapy. Conclusions- Higher quantitative cCBF at baseline is a significant predictor of good neurological outcome at day 90. cCBF levels may inform decisions regarding stroke triage, treatment of acute stroke, and general outcome prognosis. Clinical Trial Registration- URL: https://www.clinicaltrials.gov. Unique identifier: NCT02225730.

Heterogenous migraine aura symptoms correlate with visual cortex functional magnetic resonance imaging responses

OBJECTIVE

Migraine aura is sparsely studied due to the highly challenging task of capturing patients during aura. Cortical spreading depression (CSD) is likely the underlying phenomenon of aura. The possible correlation between the multifaceted phenomenology of aura symptoms and the effects of CSD on the brain has not been ascertained.

METHODS

Five migraine patients were studied during various forms of aura symptoms induced by hypoxia, sham hypoxia, or physical exercise with concurrent photostimulation. The blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signal response to visual stimulation was measured in retinotopic mapping-defined visual cortex areas V1 to V4.

RESULTS

We found reduced BOLD response in patients reporting scotoma and increased response in patients who only experienced positive symptoms. Furthermore, patients with bilateral visual symptoms had corresponding bihemispherical changes in BOLD response.

INTERPRETATION

These findings suggest that different aura symptoms reflect different types of cerebral dysfunction, which correspond to specific changes in BOLD signal reactivity. Furthermore, we provide evidence of bilateral CSD recorded by fMRI during bilateral aura symptoms. Ann Neurol 2017;82:925-939.

Ten problems and solutions when predicting individual outcome from lesion site after stroke

In this paper, we consider solutions to ten of the challenges faced when trying to predict an individual's functional outcome after stroke on the basis of lesion site. A primary goal is to find lesion-outcome associations that are consistently observed in large populations of stroke patients because consistent associations maximise confidence in future individualised predictions. To understand and control multiple sources of inter-patient variability, we need to systematically investigate each contributing factor and how each factor depends on other factors. This requires very large cohorts of patients, who differ from one another in typical and measurable ways, including lesion site, lesion size, functional outcome and time post stroke (weeks to decades). These multivariate investigations are complex, particularly when the contributions of different variables interact with one another. Machine learning algorithms can help to identify the most influential variables and indicate dependencies between different factors. Multivariate lesion analyses are needed to understand how the effect of damage to one brain region depends on damage or preservation in other brain regions. Such data-led investigations can reveal predictive relationships between lesion site and outcome. However, to understand and improve the predictions we need explanatory models of the neural networks and degenerate pathways that support functions of interest. This will entail integrating the results of lesion analyses with those from functional imaging (fMRI, MEG), transcranial magnetic stimulation (TMS) and diffusor tensor imaging (DTI) studies of healthy participants and patients.

Apparent diffusion coefficient evaluation for secondary changes in the cerebellum of rats after middle cerebral artery occlusion

Supratentorial cerebral infarction can cause functional inhibition of remote regions such as the cerebellum, which may be relevant to diaschisis. This phenomenon is often analyzed using positron emission tomography and single photon emission CT. However, these methods are expensive and radioactive. Thus, the present study quantified the changes of infarction core and remote regions after unilateral middle cerebral artery occlusion using apparent diffusion coefficient values. Diffusion-weighted imaging showed that the area of infarction core gradually increased to involve the cerebral cortex with increasing infarction time. Diffusion weighted imaging signals were initially increased and then stabilized by 24 hours. With increasing infarction time, the apparent diffusion coefficient value in the infarction core and remote bilateral cerebellum both gradually decreased, and then slightly increased 3–24 hours after infarction. Apparent diffusion coefficient values at remote regions (cerebellum) varied along with the change of supratentorial infarction core, suggesting that the phenomenon of diaschisis existed at the remote regions. Thus, apparent diffusion coefficient values and diffusion weighted imaging can be used to detect early diaschisis.

Xenon-enhanced computed tomography cerebral blood flow measurements in acute cerebral ischemia: Review of 56 cases

OBJECTIVE

Ischemic stroke must be diagnosed promptly if patients are to be treated with thrombolytic therapy. The diagnosis of acute cerebral ischemia, however, is usually based on clinical and computed tomography (CT) scan findings. CT scans are often normal in the first few hours after stroke. The purpose of this study was to determine whether Xenon-enhanced CT (XeCT) cerebral blood flow (CBF) studies could increase the sensitivity of stroke detection in the acute stage.

METHODS

CBF studies performed within 8 hours of symptom onset were evaluated in 56 patients who presented with hemispheric stroke symptoms. Mean CBF in the symptomatic vascular territory was calculated and compared with the corresponding contralateral area. CBF values below 18 mL/100g/min on 2 adjacent regions of interest were considered ischemic lesions. CT scans and angiograms were compared with the XeCt findings. Neurological condition on admission and discharge was evaluated by using National Institutes of Health Stroke Scale (NIHSS) scores.

RESULTS

The mean NIHSS score on admission was 12+/-5. Early CT scans were abnormal in 28 (50%) patients. There were 9 (16%) patients who had normal XeCT scans because of spontaneous reperfusion of the ischemic area. XeCT studies showed an ischemic lesion in 47 (84%) patients. In these patients, the mean CBF in the affected vascular territory was 16+/-8 mL/100g/min compared with 35+/-13 mL/100g/min in the contralateral specular territory (P<0.001). There were no false positive or negative XeCT studies, and the location of the perfusion defect corresponded with the CT and/or angiographic findings in all cases. Eight patients died (14%), and the 48 survivors (86%) had a mean NIHSS score of 9+/-6 on discharge.

CONCLUSIONS

CBF measurements were correlated with the CT and angiographic results and greatly assisted in the diagnosis of acute ischemic stroke. XeCT studies used for estimating the location and extent of cerebral ischemia may be important in the triage of patients for acute stroke therapy.

The Role of Temporo-parietal Cortex in Subcortical Visual Extinction

Visual extinction is an intriguing defect of awareness in stroke patients, referring to the unsuccessful perception of contralesional events under conditions of competition. Previous studies have investigated the cortical and subcortical brain structures that, when damaged or inactivated, provoke visual extinction. The present experiment asked how lesions of subcortical structures may contribute to the appearance of visual extinction. We investigated whether lesions centering on right basal ganglia may induce dysfunction in distant, structurally intact cortical structures. Normalized perfusion-weighted MRI was used to identify structurally intact but abnormally perfused brain tissue, that is, zones that are receiving enough blood supply to remain structurally intact but not enough to function normally. We compared patients with right basal ganglia lesions showing versus not showing visual extinction. In the extinction patients, the contrast revealed cortical malperfusion that clustered around the right TPJ. It seems as if malfunction of this area is a critical aspect in visual extinction not only after cortical lesion but also in the case of subcortical basal ganglia damage. Our results support the idea that a normally functioning TPJ area plays a decisive role for the attentional network involved in detecting of visual stimuli under conditions of competition.

Normalized perfusion MRI to identify common areas of dysfunction: patients with basal ganglia neglect

Perfusion-weighted imaging (PWI) is used to identify brain regions that are receiving enough blood supply to remain structurally intact, but not enough to function normally. Previous observations suggest that spatial neglect due to subcortical stroke can be explained by dysfunction of cortical areas rather than through the neuronal loss in the subcortical structures itself. The present study aimed to identify the dysfunctional cortical regions induced by basal ganglia stroke in patients with spatial neglect. In a patient group with stroke lesions centring on the basal ganglia, we examined the common area(s) of structurally intact but dysfunctional cortical tissue by using spatial normalization of PWI maps as well as symmetric voxel-wise inter-hemispheric comparisons. These new techniques allow comparison of the structurally intact but abnormally perfused areas of different individuals in the same stereotaxic space, and at the same time avoid problems due to regional perfusion differences and to possible observer-dependent biases. We found that strokes centring on the right basal ganglia which provoke spatial neglect induce abnormal perfusion in a circumscribed area of intact cortex that typically involves those three regions that have previously been described to provoke spatial neglect when damaged directly by cortical infarction: the superior temporal gyrus, the inferior parietal lobule and the inferior frontal gyrus. The data suggest that spatial neglect following a right basal ganglia lesion typically is caused by the dysfunction of (part of) these specific cortical areas.

Assessing dynamic cerebral autoregulation after stroke using a novel technique of combining transcranial Doppler ultrasonography and rhythmic handgrip

OBJECTIVES

Dynamic cerebral autoregulation (CA) is impaired after stroke. Methods employed to assess this phenomenon usually involve deliberate alterations in blood pressure (BP) by physical means. We performed a pilot study to assess dynamic CA in acute stroke patients using a novel technique of combining transcranial Doppler (TCD) ultrasonography with rhythmic handgrip.

METHODS

Ten patients with ischaemic stroke in the middle cerebral artery (MCA) territory were studied. We performed continuous recordings of bilateral MCA velocities and used rhythmic handgrip to induce BP oscillations. Changes in autoregulation were indicated by changes in phase shift and gain of MCA velocity in relation to BP. Patients were examined at <7 days, 6 weeks, and 3 months after stroke.

RESULTS

There were no significant differences in phase shift or gain between the affected and unaffected cerebral hemispheres. Combining the results from both hemispheres, there was a trend of increasing phase shift (P=0.04) and decreasing gain (P=0.24) over the first three months after stroke, indicating improving CA. Rhythmic handgrip produced an average percentage change in BP (peak-to-trough) of 10% around the mean, and the frequency of the induced BP oscillations was very similar to that of the rhythmic handgrip.

CONCLUSIONS

Combining TCD with rhythmic handgrip appeared to be a useful technique for assessing dynamic CA and it deserves further studies. In this pilot study, there was some evidence that CA might improve up to 3 months after ischaemic stroke.

Permanent or transitory effects on neurocognitive components of the CNV complex induced by brain dysfunctions, lesions and ablations in humans

Since the mid-1960s, essentially using electrophysiological methods, our research group has examined the effects of different brain diseases in humans, both on first- and second-order conditioned responses and on some types of neurocognitive potentials of the CNV complex. This didactic lecture will focus on our various attempts to identify and understand the neuroanatomical and neurophysiological substrates involved in cognitive information processing followed by the conception and execution of sensory-motor and behavioural responses evoked by significant acoustic stimuli, in both pathological situations and normal control subjects. Great interest was, e.g. aroused in the early 1970s by the rare, fortunately unrepeatable, opportunity of examining the CNV patterns in various psychiatric patients treated with psychosurgical Freeman-Watts bilateral prefrontal 'radical' lobotomy, also with repeated recordings (The Responsive Brain (1976) 158; Multidisciplinary Perspectives in Event-Related Brain-Potentials Research (1978) 376) or bimedial bifrontal cingulotomy (Multidisciplinary Perspectives in Event-Related Brain Potential Research (1978) 383). In the same period, investigations into CNV activity recorded in patients submitted to complete callosotomy ('split brain': Attention and Performance, vol. IV (1972) 221; Electroenceph. Clin. Neurophysiol. Suppl. 33 (1973) 161) were also begun and were continued into the 1980s, also with regard to other types of ERP (Brain 111 (1988) 553; J. Cog. Neurosci. 2 (1990) 258). All these data furnished unique information about the sub-second dynamics of unilateral or bihemispheric cortico-cortical and cortico-subcortical interconnections in humans. In recent years, with a classic method of analysis based on sequential scalp-topographic bidimensional neuroelectric mapping and 21/19 electrodes connected to three different references, and binaural/monaural clicks as warning signals (S1), we have repeatedly examined the CNV activity of 11 selected patients submitted to complete ablation of the damaged cortical areas, with uni- or bilateral lesions restricted to the prefrontal or associative parieto-temporal areas. We have always used the standard CNV paradigm (S1-S2 motor-response) which evokes a complex of neurocognitive potentials, including the P300 from S1, which are well-known, since they are certainly among the most studied ERPs in the various ages and races of normal subjects, psychiatric patients and subjects with different brain diseases. The most important results have been, (1) In normal subjects the MRI and the latency differences of CNV component measurements along the bidirectional pathways functionally interconnecting ipsilateral distant associative cortical areas (e.g. the arcuate-superior longitudinal complex bundle) were accounted for by the transcortical conduction time, which varies in our scalp recordings from 1 cm/0.74 to 1.28 ms ( approximately 9.8 m/s). (2) Constantly, no true auditory S1-elicited N1a, b, c, P2, N2, P300 components or CNV slow waves (O- and E-wave) were recordable over the whole of the ablated cortical areas, but only clearly identifiable volume-conducted EP/ERPs generated in other hemispheric structures. (3) The post-S1 ERP/CNV complexes on the intact hemisphere were found to be within the normal limits. (4) Effects of severe disruption on the S1 ERP/CNV complexes evocable on the site and on remote ipsilateral apparently normal anatomo-functionally interconnected brain regions were observed in 5 patients, 4 of whom had extensive frontocortical ablations. In two of the latter the distant disruptive action on the CNV components over the neuroradiologically normal ipsilateral two-way connected post-rolandic sensory and association areas was seen to be partially reversible, showing aspects of a probable slowly evolving diaschisis-like effect. Similar deactivation of some ERP components was observed in reverse on the ipsilateral dorsolateral frontocortical region in the fifth patient with a large parieto-temporal cortex ablation. These data require confirmahese data require confirmation, and when this phenomenon is observable, it must be appropriately monitored with different methods of functional neuroimaging. This will serve not only for medical and neuropsychophysiological diagnosis purposes, but also particularly for a correct and really useful planning of neuro-rehabilitation activities in selected cases.

Drug therapy of neurovascular disease

Recent advances in the prevention and pharmacotherapy of cerebrovascular disease have provided more favorable clinical outcomes. For the treatment of an acute ischemic stroke, the early use of thrombolytic agents can reduce the degree of brain damage while improving functional outcomes. However, trials evaluating various classes of other neuroprotective agents have not shown benefit to date. For the prevention of second stroke, the use of antiplatelet drugs, HMG-CoA reductase inhibitors, and angiotensin-converting enzyme inhibitors with a diuretic have shown benefit in reducing new events. In patients with underlying heart disease or atrial fibrillation, warfarin appears to be the drug of choice in preventing stroke. Early treatment of hemorrhagic stroke with calcium channel blockers can improve the functional outcome. Innovative therapies are now available for the treatment of migraine and vascular dementia. Primary prevention of stroke remains the optimal therapeutic strategy and includes treatment of systemic hypertension and hypercholesterolemia.

Frontal and parieto-temporal cortical ablations and diaschisis-like effects on auditory neurocognitive potentials evocable from apparently intact ipsilateral association areas in humans: five case reports

The aim of this study was to investigate the effects of disruption on the warning auditory S1-elicited ERP and CNV complexes recordable on the site and on remote ipsilateral apparently normal anatomo-functionally interconnected brain regions. These effects in some cases showed aspects of a probable diaschisis-like phenomenon, due to resections of extensive frontal association cortex or of primary and secondary sensory parieto-temporal areas damaged by differing pathological processes. Using a standard CNV paradigm, 21/19 EEG electrodes connected with three different references, and scalp-topographic bidimensional mapping analysis, the S1 auditory binaural/monaural clicks N1a,b,c, P2, N2, P3 and CNV waves were recorded in 10 normal subjects and 11 patients. Nine of the latter had been submitted to unilateral frontal dorsolateral cortex ablation, one to bihemispheric dorsomedial cortex ablation, and one to unilateral ablation of sensory parieto-temporal cortex and underlying white matter, verified through CT/MRI examinations. No true S1ERP/CNV components were recordable over the ablated cortical areas, whereas normal ERP/CNV complexes were observable on the intact hemispheres. In five patients, four of whom with frontocortical ablations, the S1 ERP/CNV complexes appeared severely diminished or disrupted, in two cases in a slow, partially-reversible manner, also in the neuroradiologically normal ipsilateral functionally-connected post-rolandic sensory and association areas. Similar deactivation of some ERP components was observed in reverse on the unilateral dorsolateral frontocortical region in the fifth patient with parieto-temporal cortex ablation. Even when they are partially reversible, these ipsilateral remote ERP changes in apparently intact brain regions, due to ablations of functionally-interconnected cortical formations, probably reflect cortical deactivation or simply dysfacilitation deriving from functional unilateral diaschisis. If these changes are instead irreversible they may probably be interpreted as transneuronal degeneration phenomena, though they are not at present easy to document either neuroradiologically or electroclinically.

Distribution of brain oedema in the contralateral hemisphere after cerebral infarction: repeated MRI measurement in the rat

The appearance of local cerebral dysfunction at remote regions from the focus in the acute stage of stroke (diaschisis) is well known, but its mechanism has not been established. We have analysed serial MR images of the infarcted brain of rats to evaluate the distribution of oedema. Forty-seven Sprague-Dawley rats were anaesthetized with halothane, and the right middle cerebral artery (MCA) was permanently occluded via the intraluminal approach using a nylon 2-0 suture. At 3, 6, 9 and 24 hours after the occlusion, coronal T(2)-weighted MR images were taken and the signal intensity (SI) was computed at each region of the brain. After occlusion of the right MCA, SI increased diachronically up to 24 hours on the occluded side of the cortex (52.9+/-3.2 to 104.8+/-22.4) and striatum, which are within the perfusion territory of the MCA. SI increment was also observed at the hippocampus, alveus hippocampi and pyriform lobe, which are not within the territory of the MCA, and at some regions of the contralateral side (52.5+/-4.8 to 69.4+/-14.8 at the cortex). These changes were prominent in ischaemia-vulnerable portions, mild in the cortex, and minimal in the striatum. This contralateral side SI increment indicates remote oedema, which corresponds to diaschisis. We suggest that the mechanism of this remote contralateral oedema is the movement of extravasated protein from the lesion.

Effect of middle cerebral artery occlusion on the passage of pituitary adenylate cyclase activating polypeptide across the blood-brain barrier in the rat

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to be a potent neuroprotective agent in global and focal ischemia. We demonstrated that PACAP could cross the blood-brain barrier (BBB) by a saturable transport system, and a systemic administration of PACAP reduced the infarct induced by unilateral middle cerebral artery occlusion (MCAO). Therefore, we studied whether this transport system is affected by MCAO in the rat. The entry of PACAP38 into the brain was compared in five groups: control, 4, 6, 24, and 48 h after MCAO. [(125)I]PACAP38 was injected intravenously and serum and various brain regions were collected 3 min later. The rate of entry into the brain of PACAP38 was also determined. We showed that PACAP entered the rat brain via a rapid transport system when the BBB is intact. After transient (2 h) unilateral MCAO, all regions of the brain, showed a selective increase in the passage of PACAP38 across the BBB after 4 h after the occlusion, which was not related to any generalized change in the permeability of the BBB, as measured with albumin. A significant decrease in the amount of PACAP38 entering the brain was observed in the 6- and 24-h groups, but it returned to the baseline level in the 48-h group. These results suggest that focal cerebral ischemia can selectively modify the passage of PACAP38 across the BBB, in both damaged and undamaged sides of the brain, and that these changes in influx are not solely due to the disruption of BBB. These findings imply the necessity of adjusting the dose of intravenously administered PACAP38 in order to maximize its therapeutic effect on the brain damage resulting from focal ischemia

Perceptual differences between stroke patients with cerebral infarction and intracerebral hemorrhage

OBJECTIVE

To assess perceptual performances of patients with intracerebral hemorrhage (ICH) compared with those of ischemic patients early after stroke and to analyze the psychometric properties of three perceptual tests used in the study.

DESIGN

Cross-sectional study.

SETTING

A rehabilitation unit at a teaching hospital.

PATIENTS

Twenty-two stroke patients with ICH and 22 demographically matched stroke patients with infarction.

MAIN OUTCOME MEASURES

Loewenstein Occupational Therapy Cognitive Assessment (LOTCA), Rivermead Perceptual Assessment Battery (RPAB), and Motor-Free Visual Perception Test (MVPT).

RESULTS

Stroke patients with ICH had significantly more severe deficits on a task of thinking operations than did patients with infarction. A significant lateralized effect of stroke existed in the ICH group, with patients with right-hemisphere strokes scoring lower than patients with left-hemisphere strokes on the figure-ground discrimination subtest of the RPAB. A considerable overlap among the three instruments was found. Yet, the observed correlations between supposedly similar subtests from the tests proved to be moderate, indicating that to a certain extent these test measures tap different perceptual processes. Four factors were generated from a joint LOTCA-RPAB-MVPT factor analysis. They assessed different facets of perceptual functioning, including higher-level and lower-level perceptual skills, part/whole conceptual integration, and color perception. This factor pattern accounted for 75.5% of the variance.

CONCLUSIONS

Higher-level perceptual functions tend to be relatively susceptible to ICH stroke pathology early in the course of the disease. This information has important clinical implications in the early treatment planning for the stroke patients with ICH, such that specific compensatory strategies for these deficiencies should be devised to facilitate a successful rehabilitation. Knowledge regarding the influences of specific deficits on the performance of daily activities may also be useful to the patients' family.

Spectral EEG analysis following hemispheric stroke: evidences of transhemispheric diaschisis

Quantitative EEG frequency analysis was performed within the acute stage and after the recovery in 40 patients with hemispheric stroke in order to analyze ipsi- and contralateral alpha peak frequency (APF) and band power changes. Localization of hemispheric lesion was determined by computer tomography. Changes of clinical scores were compared with the alpha asymmetries. In the cases of small subcortical infarcts good improvement of alpha activity was observed over the affected hemisphere; contralateral APF was relatively preserved. Bilateral symmetric reduction of APF was found in territorial middle cerebral artery infarcts, with poor tendency of recovery of alpha power and neurologic status. These findings suggest transitory derangement of alpha generators in the contralateral hemisphere evidenced by APF and power asymmetries. EEG signs of contralateral alpha reduction may be due to the remote effect of primary ischemic lesion indicating an electrical diaschisis phenomenon in the acute phase of stroke. EEG signs of diaschisis may anticipate a poor recovery of alpha activity and clinical status in the post-stroke period.

A new rat model of thrombotic focal cerebral ischemia

We developed a fibrin-rich thrombotic focal cerebral ischemic model with reproducible and predictable infarct volume in rats. In male Wistar rats (n = 77), a thrombus was induced at the origin of the middle cerebral artery (MCA) by injection of thrombin via an intraluminal catheter placed in the intracranial segment of the internal carotid artery (ICA). Thrombus induction and consequent ischemic cell damage were examined by histopathological analysis and neurological deficit scoring, and by measuring changes in cerebral blood flow (CBF) using laser-Doppler flowmetery (LDF), perfusion-weighted imaging (PWI), and by diffusion weighted imaging (DWI). Histopathology revealed that a fibrin-rich thrombus localized to the origin of the right MCA. Regional cerebral blood flow (rCBF) in the right parietal cortex was reduced by 34-58% of preinjection levels after injection of thrombin in rats administered 30 U of thrombin (n = 10). Magnetic resonance imaging (MRI) showed a reduction in CBF and a hyperintensity DWI encompassing the territory supplied by the right MCA. The infarct volume in rats administered 80 U of thrombin was 31.29 +/- 12.9% of the contralateral hemisphere at 24 h (n = 13), and 34.7 +/- 16.4% of the contralateral hemisphere at 168 h (n = 6). Rats administered 30 U of thrombin exhibited a hemispheric infarct volume of 34.0 +/- 14.5% (n = 9) at 24 h and 29.7 +/- 13.9% (n = 8) at 168 h. In addition, thrombotic rats (n = 3) treated with recombinant tissue plasminogen activator (rt-PA) (10 mg/kg) 2 h after thrombosis showed that CBF rapidly returned towards preischemic values as measured by PWI. This model of thrombotic ischemia is relevant to thromboembolic stroke in humans and may be useful in documenting the safety and efficacy of thrombolytic intervention as well as for investigating therapies complementary to antithrombotic therapy.

Cerebral and cerebellar diaschisis following carbamazepine therapy

1. The regional cerebral blood flow was studied by SPECT in patients with partial epilepsy before and after 30 days of monotherapy with carbamazepine (CBZ). 2. Both a qualitative visual interpretation and a semiquantitative analysis of SPECT was performed. All patients underwent EEG, CT scan, and MRI studies. The CBZ serum concentrations were assayed. 3. After therapy, in three patients with focal epilepsy, both a crossed cerebral and cerebellar diaschisis were observed, with respect to the side of the epileptic focus in the opposite hemisphere. No morphologic changes were detected at MRI in the cerebral or cerebellar remote hypometabolic areas found at SPECT. 4. CBZ may have a depressant action on the corticopontocerebellar pathways and on the corticocallosal connections.

Cerebellar diaschisis in pontine infarctions: a report of five cases

We evaluate regional cerebral and cerebellar perfusion to prove the occurrence and follow the persistence of crossed cerebellar diaschisis in infratentorial pontine infarction. Six consecutive patients exhibiting mild hemiparetic symptoms or a heavy feeling in the head (mean age 65 years; four women, two men) and diagnosed as having pontine infarction by magnetic resonance imaging were subjected to evaluation. Lesions due to infarction were located at the upper basis pontis in five patients and the upper tegmentum pontis in one, and medially at the paramedian portion in four and laterally in two. Regional cerebral and cerebellar perfusion was evaluated semiquantitatively by iodine-123 N-isopropyl-p-iodoamphetamine (IMP) single-photon emission tomography (SPET); this was done during the acute stage in five cases (mean time after onset: 0.7 months) and during the chronic stage in three (mean time after onset: 14.8 months). Four patients had two examinations during their clinical courses. For semiquantitative evaluation of perfusion, an asymmetry index was calculated for each region of interest, set symmetrically in regions of the cerebral cortex and cerebellum in both hemispheres. Significant asymmetry (P < 0.01) in cerebellar perfusion, which was reduced in the contralateral (n = 4) or ipsilateral (n = 1) cerebellar hemisphere, was demonstrated semiquantitatively in four cases during the acute stage and in one during the chronic stage, as compared with normal controls (n = 5, mean age 61 years). This asymmetry continued to the chronic stage (6.5 and 33.0 months) in two cases, while no patient showed any significant asymmetries in cerebral perfusion in any region of interest in either SPET study.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoradiographic measurement of regional brainstem blood flow. Findings after 2 hours of occlusion of the unilateral anterior inferior cerebellar artery and 30 minutes' occlusion of the unilateral vertebral artery

Using [14C]iodoantipyrine, regional brainstem blood flow was measured in the rat 2 h after occlusion of the left anterior inferior cerebellar artery (AICA) and 30 min after occlusion of the left vertebral artery (VA). Two hours after occluding the left AICA, the mean +/- SEM value of blood flow in 6 animals in the right superior olive was 2.13 +/- 0.13 ml/g/min and in the left side, 1.13 +/- 0.11. Thirty minutes after occlusion of the left VA, there were no significant differences between the right and left sides. Blood flow changes were assessed in the hindbrain structures between the control group, 30 min after occlusion of the left VA and 2 h after occlusion of the left AICA. Changes observed in the blood flow in the hindbrain structures suggest that the extra volume of the blood flow might be concealed in the brainstem. However, whether the recovery of the blood flow rate indicates the recovery of the brainstem function remains unclear.

Clinical features, pathogenesis, and computed tomographic characteristics of internal watershed infarction

BACKGROUND AND PURPOSE

Infarction in the internal border-zone region has been described radiologically and pathologically. The aim of this study was to define the clinical and pathophysiological correlates of internal watershed infarction.

METHODS

Eighteen consecutive stroke patients with evidence of internal watershed infarction on computed tomography (CT) were studied.

RESULTS

Two CT patterns were identified: 6 patients had confluent internal watershed infarction (CIWI), and 12 patients had partial internal watershed infarction (PIWI). Syncopal symptoms and/or documented hypotension were prominent in both groups. Patients with CIWI usually presented with stepwise onset of contralateral hemiplegia and recovered poorly; patients with PIWI usually had discrete episodes of brachiofacial sensorimotor deficit and good recovery. Both groups had evidence of cortical involvement as part of their clinical deficit. Severe carotid occlusive disease was seen in 10 patients, and 12 patients had evidence of transiently impaired cardiac output. Carotid disease (P < .001), cardiac disease (P < .01), and diabetes mellitus (P < .01) were more prevalent in patients with internal watershed infarction compared with our stroke population as a whole.

CONCLUSIONS

Distinguishing internal watershed infarction from lacunar and other subcortical infarctions is important because the different pathological mechanisms demand different therapeutic strategies.

Regional cerebral blood flow in chronic stroke patients

BACKGROUND AND PURPOSE

The aim of this study was to investigate regional cerebral blood flow parameters during the postacute phase of unilateral ischemic stroke and to correlate them with clinical data.

METHODS

Regional cerebral blood flow was measured in 187 patients in the stabilized phase of stroke by the xenon-133 inhalation method with 32 extracranial detectors. Thirty-eight patients were reexamined after a mean +/- SD time of 32 +/- 21.4 months.

RESULTS

The overall detection of hypoperfusion was 92.0%, with asymmetries as the most sensitive index, especially for patients with a lesser degree of neurological disability. Neurological disability score was strongly associated with regional cerebral blood flow in the affected hemisphere (p < 0.0001) and with asymmetries (p < 0.0001). The presence of carotid obstruction further decreased the regional cerebral blood flow in the affected hemisphere and significantly increased asymmetry (p < 0.0001). Subjects who had no hypoperfusion at absolute values analysis were more frequently free of carotid disease and had less severe disability than those who had bilateral or unilateral regional absolute cerebral blood flow reduction. In 38 patients without new cerebrovascular events, a significant (p = 0.005) reduction of hemispheric regional cerebral blood flow asymmetries was found on a follow-up examination.

CONCLUSIONS

These data confirm the value of regional cerebral blood flow asymmetries in stroke detection and point out that important clinical information is also contained in absolute values analysis.

Microvascular morphometry in primate diaschisis

Focal cerebral ischemia was produced in monkeys by transorbital occlusion of the right middle cerebral artery. Following this, in one group of animals the total microvasculature, including both perfused and nonperfused vessels of the opposite caudate nucleus and insula, was examined by alkaline phosphatase staining of the endothelium. In another group, the patency of the microvascular bed was visualized by india ink perfusion. The number, diameter, and length of visualized vessels were measured by means of a Wild ASBA image analysis system. The perfused patient microvascular bed was significantly reduced in both insula and caudate nucleus in the supposedly normal left side, although the total microvascular volume showed an increase at 4 and 12 hr in the insula and at 48 hr in the caudate nucleus. Reduced perfusion in the hemisphere opposite to the occluded middle cerebral artery provides an anatomical substrate for the phenomenon of "diaschisis."

Custom-tailored hemodilution with albumin and crystalloids in acute ischemic stroke

BACKGROUND AND PURPOSE

Hemodilution in the acute phase of ischemic stroke is still controversial. Multicenter studies have failed to demonstrate any benefit. The present study focuses attention on analysis of circulation in stroke and on individual restabilization of circulation.

METHODS

The Amsterdam Stroke Study is a prospective, single-center, randomized clinical trial (n = 300). Normovolemic hemodilution is accomplished in a customized procedure by administration of 20% albumin plus crystalloids under hemodynamic and rheological monitoring in the acute phase of stroke. All patients receive general intensive care treatment and monitoring with a pulmonary artery catheter. This custom-tailored fluid therapy is guided on the basis of a target pulmonary capillary wedge pressure (12 +/- 3 mm Hg) and hematocrit (0.32 +/- 0.02). The control group receives only customized rehydration by infusion of crystalloids.

RESULTS

We obtained significant (p less than 0.05) reduction in mortality at 3 months (from 27% to 16%) and an increase in independence at home (from 35% to 48%) after viscosity reduction by means of hemodilution with albumin in the subgroup with a hematocrit less than 0.45 (n = 201) (specific viscosity effect). We also obtained a significant (p less than 0.005) reduction in mortality at 3 months (from 27% to 8%) and an increase in independence (from 35% to 59%) after only rehydration with crystalloids in the subgroup with overt dehydration (hematocrit greater than or equal to 0.45; n = 51) as compared with the normal-hematocrit group without signs of dehydration (hematocrit less than 0.45; n = 103) (specific rehydration effect).

CONCLUSIONS

This study may provide an explanation for the failures in former hemodilution trials and may re-establish proper hemodilution and rehydration as a valuable therapy in the acute phase of stroke, thus reducing mortality and improving independence after 3 months.

Hemodynamic consequences of common carotid artery thrombosis and thrombogenically activated blood in rats

We documented the hemodynamic consequences of nonocclusive common carotid artery thrombosis (CCAT) and tested the hypothesis that vasoactive substances capable of altering local CBF (LCBF) are released into the systemic circulation following cerebrovascular injury. Ten minutes after photochemically induced CCAT, an autoradiographic determination of LCBF was conducted with [14C]iodoantipyrine. In blood transfusion studies using donor and recipient rats, a 1-ml sample of thrombogenically activated blood (TAB) collected downstream from the forming thrombus was reinjected into a recipient rat 15 or 60 min before CBF study. A heterogeneous pattern of abnormal LCBF was documented in the ipsilateral hemisphere of CCAT rats and recipient rats receiving TAB 15 min before CBF study. Acute hemodynamic abnormalities included ischemic (less than 35% of control) and hyperemic (greater than 125% of control) foci and more global reductions (50-80% of control) in cortical and subcortical LCBF. Border zone hyperemia exceeding 2.0 ml/g/min was associated with focal sites of severe LCBF reductions. Although recipient rats that received TAB 15 min before CBF study displayed similar hemodynamic abnormalities, LCBF values in 60-min recipient rats were not significantly different from control despite ischemic foci. Humoral factors generated during CCAT appear to be responsible for the acute LCBF consequences of cerebrovascular thrombosis. Vasoactive substances released from a thrombotic site, capable of regionally affecting vascular reactivity in a time-dependent fashion, might be expected to participate in the pathogenesis of transient ischemic attacks and acute stroke.

Effects of MK-801 on cerebral regional oxygen consumption in focal cerebral ischemia in rats

This investigation tested in rats whether MK-801, an N-methyl-D-aspartate receptor antagonist, would improve the balance of oxygen supply and consumption in the focal ischemic area of the brain induced by occlusion of the middle cerebral artery. Fifteen minutes after middle cerebral artery occlusion, 5 mg/kg MK-801 was administered intravenously to the MK-801 group (n = 12), and normal saline was given to the control group (n = 12). One hour after the occlusion in each group, regional cerebral blood flow was determined in six rats using [14C]iodoantipyrine, and regional arterial and venous oxygen saturations were determined using a microspectrophotometric technique in the other six rats. In both groups of animals, the cerebral blood flow of the ischemic cortex was significantly lower than that of the contralateral cortex (36 +/- 16 [SD] and 67 +/- 14 ml/min/100 g for the control group; 33 +/- 10 and 58 +/- 11 ml/min/100 g for the MK-801 group, respectively). Oxygen extraction was significantly higher in the ischemic cortex (8.8 +/- 2.1 ml O2/100 ml blood) than in the contralateral cortex (5.6 +/- 0.3) for the control group. However, for the MK-801 group, there was no significant difference between the ischemic cortex (6.1 +/- 1.0) and the contralateral cortex (5.7 +/- 1.1). Oxygen extraction in the ischemic cortex of the MK-801 group was significantly lower than that of the control group. Calculated ischemic regional oxygen consumption was similar to the nonischemic values in the control group, whereas the ischemic value was reduced to 61% of the value of the contralateral cortex in the MK-801 group.(ABSTRACT TRUNCATED AT 250 WORDS)

Transhemispheric diaschisis. A review and comment

We review here the literature in both animal models and humans concerning electrical activity, blood flow, and metabolism in the hemisphere contralateral to unilateral cerebral ischemia. We analyze the data by periods based on the time from initial injury to emphasize the time course of transhemispheric diaschisis. Contralateral electrical activity, such as evoked potential amplitude, is increased in the late stages after unilateral infarction, with the data from the more acute periods being inconclusive. Contralateral blood flow changes probably depend on the magnitude of the ischemic injury, with a larger insult resulting in a decrease not seen with smaller insults. Some studies have shown a decrease in contralateral blood flow over the first week followed by a gradual return toward baseline. Most measures of contralateral metabolism show a time course similar to blood flow, that is, a decrease followed by gradual recovery. The effects of corpus callosum section on transhemispheric diaschisis are not yet established. We provide examples to show that under certain conditions, diaschisis may represent a loss of remote inhibition rather than a loss of remote facilitation, as von Monakow originally suggested. By following the contralateral changes over time, particularly during the first minutes and hours of ischemia, insight will be gained into the brain's responses remote from the focus of ischemic injury. These responses should bear a relation to the brain's defense mechanisms ipsilaterally to the region of ischemia.

Bilateral impairment of somesthetically mediated object recognition in humans

Thirty adult patients (six in each of five groups--neurologically normal, lacunar infarct-related hemiparesis, unilateral thalamic lacunar infarction, right cortical infarction with mild left hemineglect, and extensive right cortical infarction with severe left hemineglect) were asked to perform various tasks that encompassed basic and intermediate somatosensory functions and tactile and visual object recognition. Patients with thalamic and cortical infarctions had severe impairment of contralateral hand-mediated somatosensory functions in all three categories of somesthetic tasks, although patients with cortical infarction were more impaired on the object recognition task than were patients with thalamic infarction. Patients with extensive damage to the right hemisphere and severe left hemineglect also had impairment of somesthetically mediated object recognition in the ipsilateral hand despite normal basic and intermediate somatosensory function and visually mediated object recognition analogous to unilateral tactile agnosia. All other groups had normal ipsilateral tactile object recognition.

Clinical recovery and sleep architecture degradation

We achieved a unique and timely recording of cerebral activity in a 70 year old woman immediately pre- and post-stroke, while studying the effect of acute cerebral infarction on sleep-electroencephalogram (EEG) patterns. Normal patterns, except for increased wakefulness, were recorded during two pre-infarct polysomnograms. Immediately following cerebral infarction increased delta activity was recorded from the infarcted hemisphere only. Initially, REM sleep could not be recorded from either side; however, on the third post infarct day REM sleep returned. Background EEG levels from both hemispheres became progressively slower, flatter and simpler. In addition, sleep spindles and the distinctive saw-tooth wave forms of sleep almost disappeared. At one year post-stroke sleep-EEG rhythm recordings from both hemispheres became more similar except for persisting delta activity from the left hemisphere. Unexpected deterioration of sleep-EEG pattern recordings from the undamaged hemisphere taken during the patient's clinical recovery remains unexplained. Serial sleep recording may facilitate the study of brain recovery, activity and reorganization following stroke.

Local cerebral blood flow during and after bilateral carotid artery occlusion in unanesthetized gerbils

Using [14C]iodoantipyrine autoradiography, we measured regional cerebral blood flow in unanesthetized gerbils subjected to 2 (n = 5) or 30 (n = 6) minutes of bilateral carotid artery occlusion or 5 (n = 6), 30 (n = 6), or 120 (n = 5) minutes of reflow after 30 minutes of occlusion. Blood pressure, respiratory rate, and blood gases were recorded, and these and other gerbils were evaluated with periodic neurologic examinations. Blood flow to structures above the level of the diencephalon ceased almost totally during occlusion. The lateral thalamus, the rostral three quarters of the hypothalamus, and the superior colliculi were also markedly ischemic. Blood flow to the brainstem and cerebellum was only slightly affected. After release of the occlusion, blood flow was restored in some of the affected areas but to levels somewhat below that in eight sham-operated gerbils. In several areas, principally column-shaped areas in the cortex as well as patchy areas in other structures, blood flow did not recover. This inhomogeneous blood flow distribution lasted at least 30 minutes after release of the occlusion. Thereafter, the inhomogeneity slowly disappeared in such a manner that blood flow to originally well reperfused areas appeared to decrease while that to poorly reperfused areas increased. During reflow, blood flow in the brainstem and cerebellum slowly and continuously decreased. We show that there is an early no-reflow phenomenon that is inhomogeneous and appears to be of vascular origin and lasts approximately 30 minutes after release of the occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of the serotonin antagonist ketanserin on the hemodynamic and morphological consequences of thrombotic infarction

The effect of the serotonin (5-hydroxytryptamine, 5-HT) antagonist ketanserin on the remote hemodynamic consequences of thrombotic brain infarction was studied in rats. Treated rats received an injection of 1 mg/kg ketanserin 30 min before and 1 h following photochemically induced cortical infarction. Local CBF (LCBF) was assessed autoradiographically with [14C]iodoantipyrine 4 h following infarction, and chronic infarct size was documented at 5 days. Thrombotic infarction led to significant decreases in LCBF within noninfarcted cortical regions. For example, mean LCBF was decreased to 63, 55, and 65% of control (nontreated normal rats) in ipsilateral frontal, lateral, and auditory cortices, respectively. In rats treated with ketanserin, significant decreases in LCBF were not documented within remote cortical areas compared with controls. In contrast to these hemodynamic effects, morphological analysis of chronic infarct size demonstrated no differences in infarct volume between treated (27 +/- 3 mm3) and nontreated (27 +/- 6 mm3) rats. These data are consistent with the hypothesis that 5-HT is involved in the widespread hemodynamic consequences of experimentally induced thrombotic infarction. Remote hemodynamic consequences of acute infarction can be inhibited without altering final infarct size.

Evaluation of cerebral blood flow data in stroke patients using a mapping system

We retrospectively examined regional cerebral blood flow values in 78 patients in the stabilized phase of stroke to evaluate the consistency of lateralization compared with computed tomographic imaging. Examinations were performed using the xenon-133 inhalation technique, and the data were processed and displayed by a computer-assisted system of our own design that allows statistical analysis in real time and is suitable for clinical use. The consistency of lateralization correlated with computed tomographic findings was tested for absolute values, percent distribution, and asymmetries. The latter yielded the highest degree of sensitivity (in 83.3% of the patients the affected hemisphere was correctly identified). Absolute values showed at least one hypoperfused area in the affected hemisphere in 48.7% of the patients, and percent distribution did so in 57.7%. Furthermore, the combination of the three methods of data analysis yielded a sensitivity of 91%; the remaining 9% of the patients, however, exhibited some abnormalities of regional cerebral blood flow (bilateral or contralateral hypoperfusion). Although good agreement was found for lateralization by computed tomography and by the combined use of the three methods of analysis, a complete overlap between functional and structural examinations should not be expected. Problems concerning the sensitivity of the xenon-133 inhalation technique under conditions of low blood flow and the statistical analysis of regional cerebral blood flow data are discussed.

Local cerebral glucose utilization in chronic middle cerebral artery occlusion in the cat

This study examines the correlation between local CMRglc (LCMRglc) alterations and clinicopathological changes in a chronic middle cerebral artery (MCA) occlusion model in the cat. The left MCA was occluded for a period of 2 h. The animals were grouped into mild, moderate, and severe ischemia based on the depression of the EEG 30 min after the MCA occlusion. Following release of the clip, the animals were allowed to recover for a week during which time daily neurological examinations were performed. On the seventh day [14C]2-deoxyglucose was injected for the determination of LCMRglc. Alternative blocks were processed for histological evaluation in which both neuronal and phagocytic changes were graded into four categories (0 = normal to 3 = severe). LCMRglc (mumol/100 g/min) in the ischemic hemisphere (all histological grades) was significantly lower than the metabolic rate in comparable regions of the sham MCA occlusion group. Regions with significant phagocytosis (grade 2 and 3) invariably exhibited activated glucose metabolism (57.4 +/- 8.4 and 105.9 +/- 6.8 mumol/100 g/min, respectively), which was significantly higher than in regions without phagocytosis (30.4 +/- 0.8 mumol/100 g/min). There was a significant gradient of metabolism in the central, peripheral, and boundary zone and the non-MCA territory in the animals with severe ischemic lesions. LCMRglc in the central MCA territory was well correlated with the EEG amplitude changes (r = 0.82, p less than 0.05) and the morphological score (r = -0.89, p less than 0.05). The metabolic rate was significantly depressed in both the ipsilateral and the contralateral central MCA territories in comparison with the sham occlusion animals. The depression in LCMRglc in the contralateral hemisphere correlated well with the concomitant depression in the contralateral EEG amplitude. These studies demonstrate that local heterogeneous metabolic alterations and contralateral cortical diaschisis exist chronically following temporary MCA occlusion and that the increases in local cerebral glucose metabolism seen in chronic stroke may be due to phagocytotic activity.

Correlation between cerebral blood flow and histologic changes in a new rat model of middle cerebral artery occlusion

We describe a new focal ischemia model consisting of unilateral middle cerebral artery occlusion with a silicone rubber cylinder attached to a nylon surgical thread inserted through the internal carotid artery in rats. Recirculation was accomplished by pulling the thread out of the artery. We evaluated the reliability of this model and studied the influence of reperfusion of the brain by measuring regional cerebral blood flow in 30 rats and by using conventional neuropathologic methods after different periods of occlusion in 48 rats. The anterior neocortex and the lateral part of the caudate putamen, which were supplied by the occluded middle cerebral artery, were the regions most frequently damaged. After 1 hour of occlusion in five rats, in the cortex supplied by the occluded artery mean +/- SD blood flow was 0.19 +/- 0.08 ml/g/min (approximately 15% of that in the corresponding region of five sham-operated control rats), and mild scattered ischemic cell change was observed. Three (n = 5) or six (n = 5) hours of occlusion reduced blood flow more severely and caused severe ischemic cell changes in the cortex supplied by the occluded artery in proportion to the duration of ischemia. Characteristically, in five rats subjected to 3 hours of occlusion followed by 3 hours of recirculation, blood flow was restored and spongy edematous change was observed in the cortex supplied by the recirculated artery. This change resulted in hypoperfusion of the neighboring cortical region surrounding the recirculated area. Our model should be useful in various investigations of the influence of reperfusion on focal ischemic brain injury.

Acute thrombotic infarction suppresses metabolic activation of ipsilateral somatosensory cortex: evidence for functional diaschisis

To study the effects of focal infarction on the capacity for functional activation of an ipsilateral somatosensory system remote from the lesion, we produced a small thrombotic infarct in the left frontal pole of male Wistar rats by a photochemical method. Five days later, the awake, restrained rats received tactile stimulation of the large whiskers (vibrissae) of the right side of the face, while a double-label 14C-autoradiographic study of local CMRglc (lCMRglc) and local CBF (lCBF) was performed. Unlesioned and unstimulated animals served as controls. In rats without frontal infarct, vibrissae stimulation led to activation of lCMRglc in the three synaptic relay stations of the barrel-field pathway (ipsilateral trigeminal medullary nucleus, contralateral ventrobasal thalamus, and contralateral barrel-field cortex). The mean increment in lCMRglc was 42% in lamina IV of barrel-field cortex and 49% in ventrobasal thalamus. Normalized lCBF tended to increase in superficial cortical laminae. In unstimulated animals with frontal infarct, lCMRglc was reduced by 20-30% throughout the ipsilateral barrel-field cortex as well as other ipsilateral cortical regions, but not in ventrobasal thalamus or other subcortical areas. In animals with frontal infarct subjected to contralateral vibrissae stimulation, a remarkable suppression of activation was observed throughout the barrel-field cortex so that left-less-than-right hemispheral lCMRglc asymmetry persisted despite stimulation. The ventrobasal thalamus, similarly, failed to increment its lCMRglc with vibrissae stimulation, whereas activation of the trigeminal nucleus was not suppressed. Similar trends were observed in the normalized lCBF data. These observations, which establish that a small frontal infarct is capable of suppressing normal physiological activation in remote ipsilateral brain structures, may have important implications with respect to suppression and recovery of function in human ischemic stroke.

Changes of blood flow in the cerebral cortex after subcortical ischemic infarction

The two-dimensional xenon-133 inhalation method was used to measure cortical blood flow in 16 patients with small subcortical ischemic infarcts and in 10 patients with larger cortical infarcts in the chronic phase of stroke. An abnormal hemispheric asymmetry of blood flow was seen, not only in patients with cortical infarcts, but also in those with subcortical infarcts. In the patients with subcortical infarcts, focal areas of reduced cortical blood flow were seen in the symptomatic hemisphere remote from the tissue destruction, usually including part of the noninfarcted frontoparietal cortex. The cortical dysfunction may have contributed to the clinical manifestations including aphasia, which was present in 14 of the 16 patients with subcortical lesions.

Remote effects of subcortical cerebrovascular lesions: a SPECT cerebral perfusion study

The remote effects of small unilateral cerebrovascular lesions confined to subcortical structures were evaluated by single photon emission computerized tomography (SPECT) and a CBF tracer, I-123 HIPDM. A CBF study was performed in 34 patients presenting with subcortical stroke either in the acute or in the chronic stages. Twenty-one of the 34 patients showed areas of cortical hypoperfusion ipsilateral to the subcortical lesion. In 14 patients, asymmetry of perfusion was also observed at the cerebellar level, perfusion being significantly reduced in the cerebellar hemisphere contralateral to the lesion. There was no correlation between the degree and extension of these remote effects and the type of stroke (ischemic or hemorrhagic), the patency of cerebral arteries, or the size and site of the lesion by transmissive computerized tomography (TCT). Subcortical hematomas showed a correlation between occurrence of remote effects and time interval from the onset of stroke, occurring more frequently in the acute phase. A correlation was observed between cortical and cerebellar remote effects and the severity of clinical presentation. The causes of remote effects are still unclear and have been extensively debated. Our data indicate that there is a relationship of remote effect to the neurological status. It is possible to show, by noninvasive, low-cost methods, remote CBF effects after stroke that may contribute to the assessment of brain functional impairment.

Triple-tracer autoradiography demonstrates effects of hyperglycemia on cerebral blood flow, pH, and glucose utilization in cerebral ischemia of rats

Triple-tracer autoradiography was used to measure topographic changes in local cerebral blood flow, cerebral tissue pH, and local cerebral glucose utilization in hyperglycemic and normoglycemic rats, all of which had undergone occlusion of the middle cerebral artery. More severe and extensive reduction of all three variables was observed in the hyperglycemic than in the normoglycemic rats. In seven normoglycemic rats, significant reduction in local cerebral blood flow (p less than 0.025) was observed in the ischemic but not in the contralateral nonischemic side at the lateral portion of the caudate nucleus and the neocortex. Tissue pH was significantly lower (p less than 0.025) only at the lateral portion of the caudate nucleus in the ischemic side. No significant differences in local cerebral glucose utilization were observed when the two hemispheres were compared. In the ischemic hemisphere of five hyperglycemic rats, the caudate nucleus and the neocortex exhibited significant reduction (p less than 0.025) in local cerebral blood flow, tissue pH, and local cerebral glucose utilization. Even in the nonischemic hemisphere of the hyperglycemic rats, local cerebral blood flow in the caudate nucleus and the neocortex was significantly reduced (p less than 0.025) compared with the normoglycemic rats. No significant change in tissue pH or local cerebral glucose utilization was observed throughout the nonischemic hemisphere of the hyperglycemic compared with the normoglycemic rats. Tissue pH was systematically lower in the hyperglycemic than in the normoglycemic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropsychological improvement following endarterectomy as a function of outcome measure and reconstructed vessel

30 patient receiving right or left carotid reconstruction and 15 medically matched controls were compared pre- and post-surgically on measures of motor speed, sustained vigilance, verbal memory and verbal and nonverbal intellectual function. The group receiving right sided vessel reconstruction demonstrated the largest post-operative improvement in intellectual function in any of the groups. The findings suggest that increased blood perfusion following right sided endarterectomy facilitates the right hemisphere's exclusive control of bilateral attention/arousal responses. In addition, findings suggest that detection of post-endarterectomy improvement may be dependent on the specific task dimension sampled, e.g., speed vs. cognitive ability and verbal-graphic vs. nonverbal symbol manipulation.

Crossed cerebello-cerebral diaschisis in a patient with cerebellar infarction

After supratentorial infarction crossed cerebellar diaschisis has been described. This report concerns the rare phenomenon of crossed cerebral diaschisis in cerebellar infarction. Relative distribution of cerebral and cerebellar blood flow was measured using three-dimensional, qualitative single-photon-emission-computed-tomography (SPECT) with a rotating gamma camera and 123I-IMP. Regional cerebral blood flow was calculated with the two-dimensional, quantitative 133Xe-inhalation-technique. Reduced uptake was observed in the left cerebral hemisphere (-13.9%) contralateral to the cerebellar infarction with the most marked reduction in the left premotor region (-21%). This might be explained by the functional depression of cerebello-ponto-thalamo-cerebral pathways.

Contralateral flow reduction in unilateral stroke: evidence for transhemispheric diaschisis

Using clinical presentation, angiography, computed tomography, and nuclear magnetic resonance imaging, 7 patients were identified who had strictly unilateral hemispheric infarction and unilateral cerebrovascular disease. In 6, cerebral blood flow measured by fluorine-18-fluoromethane inhalation and positron emission tomography was reduced in the contralateral hemisphere (p less than 0.05). Multiple regression analysis demonstrated a high correlation between contralateral flow reduction and the degree of flow impairment in the infarcted area (r = 0.941, p = 0.0014) but not with age, risk factor profile, blood pressure, PCO2, hematocrit, or duration of stroke. We conclude that transhemispheric diaschisis best explains the contralateral flow reduction seen in supratentorial ischemic stroke.

Cerebral blood flow in the evolution of infarction following unilateral carotid artery occlusion in Mongolian gerbils

Cerebral blood flow (CBF) was measured in gerbils 2, 4, 7, and 12 hours after unilateral irreversible carotid artery ligation to determine if the delayed ischemic damage to nerve terminals that occurs over 8 hours after stroke could be due to changes in CBF. [14C]butanol (4.5 mu Ci in 45 microliter 0.9% saline) was injected into the femoral vein, and cpm accumulating in the cerebrum and in a catheter inserted in the abdominal aorta were measured. CBF (ml/100 g/min, mean +/- SEM) in sham-operated control gerbils was 108.4 +/- 37.5 in the left hemisphere and 123.8 +/- 37.1 in the right. CBF in the ischemic left cerebrum was 41.0 +/- 7.7 at 2 hours (n = 7), 21.6 +/- 7.2 at 4 hours (n = 4), 26.2 +/- 4.6 at 7 hours (n = 7), and 9.7 +/- 3.1 at 12 hours (n = 6). CBF in the nonligated right hemisphere was 115.0 +/- 15.3 at 2 hours, 70.4 +/- 23.3 at 4 hours, 80.4 +/- 14.6 at 7 hours, and 50.9 +/- 20.1 at 12 hours. As expected, CBF was significantly reduced in the ischemic left cerebral hemisphere compared with the nonligated right cerebral hemisphere at each time, but CBF in the ischemic left cerebral hemisphere was also significantly lower at 12 hours than at 2 hours (p = 0.002) and at 7 hours (p = 0.014). CBF in the nonligated right cerebral hemisphere was also lower at 12 hours than at 2 hours (p = 0.02). No changes in PCO2 or blood pressure accounted for these differences.(ABSTRACT TRUNCATED AT 250 WORDS)

Photochemically induced cerebral infarction. II. Edema and blood-brain barrier disruption

Alterations in the blood-brain barrier to proteins, and regional water and electrolyte content were documented in a rat model of photochemically induced small-vessel thrombosis leading to infarction. Horseradish peroxidase (HRP) or Evans blue was given immediately following a 2-min photochemical sensitization period. At 5 min following irradiation, multifocal sites of peroxidase extravasation were noted within the irradiated area. Ultrastructural examination revealed endothelial cells filled with HRP which in some cases extended into the basal lamina and extracellular spaces. At 15 min, protein leakage was more pronounced within the irradiated zone and reaction product was also apparent within the subarachnoid and perivascular spaces of brain regions remote from the site of irradiation. Widespread staining on the surface of the irradiated hemisphere was apparent in rats perfused 8 h following Evans blue infusion. Water content increased significantly by 15 min within the irradiated zone but not in brain regions remote from this site. Although vasogenic edema is an early event in this stroke model, increases in water content are restricted to the irreversibly damaged site. In contrast, protein tracer escaping from microvessels coursing within the irradiated zone was widely distributed. These findings implicate endothelial barrier dysfunction in the genesis of tissue injury in this model. Morphological evidence for the capability of macromolecules to escape from a site of evolving infarction and to migrate to distances remote from the area of primary microvascular damage is also discussed.

Cerebral blood flow in acute and chronic ischemic stroke using xenon-133 inhalation tomography

Serial measurements of cerebral blood flow (CBF) were performed in 12 patients with acute symptoms of ischemic cerebrovascular disease. CBF was measured by xenon-133 inhalation and single photon emission computer tomography. Six patients had severe strokes and large infarcts on the CT scan. They showed in the acute phase (Days 1-3) very large low-flow areas, larger than the hypodense areas seen on the CT scan. The cerebral vasoconstrictor and vasodilator capacity was tested in the acute phase following aminophylline and acetazolamide, respectively. A preserved but reduced reactivity was seen at both tests in all 6 cases in the infarct and the peri-infarct areas. On Days 5-25, 4 of the patients had transitory increases (59-108%) of CBF, probably corresponding to lysis of an intracerebral embolic occlusion. The other 2 patients showed on Days 7-15 only a moderate CBF increase (appr. 20%), both had occlusion of the relevant internal carotid artery. In all 6 patients, CBF studies at 2 and 6 months resembled the acute phase, showing large areas with reduced flow. At the 6 months follow-up, the vasodilatory stress test was repeated, and all but one showed a preserved but reduced vasoreactivity in the infarct and peri-infarct tissue. Of the remaining 6 patients, one had a pontine infarct and one had no lesions on the CT scan, both having normal angiograms and CBF maps. Four patients had small deep or subcortical CT lesions, and showed a slight, but persistent CBF reduction of about 6-8% in the parietal region on the affected side. No changes in the flow pattern were seen at the vasoreactive studies. A likely explanation for the finding of superjacent low-flow areas is an intrahemispheric uncrossed diaschisis. This interpretation is discussed in relation to the peri-infarct low-flow area seen in the 6 cases with large infarcts.

Cerebral glucose metabolism during the recovery period after ischemia--its relationship to NADH-fluorescence, blood flow, EcoG and histology

Local cerebral glucose utilization (lCMRgl), NADH fluorescence, cerebral blood flow (CBF), electrocortical activity (ECoG) and histology were studied during a 4 hr recovery period following 2 hrs of left middle cerebral artery (MCA) occlusion in cats. Changes in relative reduced pyridine nucleotides and CBF were measured by fluororeflectometry, ECoG was obtained from the left middle ectosylvian gyrus (MEG), and lCMRgl was measured at the end of the recovery period autoradiographically with 14-C-2-deoxyglucose. A sham group was comprised of 4 cats. The ten animals subjected to the stroke were classified into 3 groups based on the mean amplitude of the ECoG at the end of the ischemic period. At the end of the recovery period, the relative reduced pyridine nucleotides showed a 22.5% oxidation (oxidation of NADH), a 66.2% reduction (reduction of NAD) and a 3.0% reduction compared to the sham group in the severe, moderate and mild groups, respectively. LCMRgl of the left MEG in the severe group was 64.2% of the corresponding sham value, whereas lCMRgl in the moderate and mild groups were 124.8% and 132.0% of the sham, respectively. CBF at the end of the recovery period ranged from 28.1% to 83.0% of the sham value, although there was no significant difference among these groups. Histologically, a large portion of the neurons in the left MEG in the severe group showed ischemic neuronal changes, while the damage was less severe in the moderate and mild groups. On the basis of these data, it is suggested that a relative substrate deficiency and/or a loss of mitochondrial enzymatic pool size may occur in the animals comprizing the severe group. Conversely, anaerobic glycolysis may be activated in the moderate group, while the mild group exhibits an increase in glucose metabolism that is most likely aerobic. A gradient in the magnitude of changes in lCMRgl was noted from the central MCA territory to the surrounding brain regions in the ischemic hemisphere. In addition, there was a mild, but statistically significant (p less than 0.05), depression in lCMRgl with no histological damage in the non-ischemic hemisphere of the severe group.

No evidence for transhemispheric diaschisis after human cerebral infarction

Forty-four studies of regional cerebral blood flow (rCBF), fractional oxygen extraction (rOER) and oxygen consumption (rCMRO2) were made on twenty-five patients with recent internal carotid artery territory infarcts. The purpose was to study flow-metabolism relationships in the contralateral hemispheres, and to investigate whether contralateral rCMRO2 was depressed as a result of the recent infarcts. Two groups of controls were included for comparison--seventeen normal volunteers, and ten patients with proven extracranial cerebrovascular disease but without evidence of cerebral infarction. The results demonstrated that: contralateral hemispheric rCMRO2 was less variable than regional oxygen availability (the product of rCBF and arterial oxygen content). This was due, in part, to the effect of individual variations in PaCO2 on rCBF, but other uncontrolled factors, such as intracranial pressure, may have had influences. As a result, rCMRO2 did not correlate with rCBF; mean rCMRO2 in the contralateral hemispheres was 12% lower than normal (a significant difference), but was not different from the value found in patients with extracranial vascular disease in whom there was no evidence of infarction or ischemia; contralateral rCMRO2 did not correlate with the size of the infarct in the opposite hemisphere. It is concluded that rCMRO2 cannot be inferred from rCBF measurements in uncontrolled human studies (as frequently done in the past), and that depression of contralateral rCMRO2 may have preceded infarction in the opposite hemisphere, a consequence of the previous influences of diseases that predispose to stroke.

Photochemically induced cortical infarction in the rat. 1. Time course of hemodynamic consequences

Alterations in local CBF (LCBF) were assessed autoradiographically in the rat at several time points following photochemically induced cortical infarction. Cortical infarction of consistent size and location was produced by irradiating the brain with green light through the intact skull for 20 min following the systemic injection of rose bengal. A consistent pattern of altered LCBF was recorded in both ipsilateral and contralateral brain regions over the course of the study. At 30 min, a severely ischemic zone surrounded by regions of cortical hyperemia was apparent. LCBF was also depressed relative to control values in ipsilateral cortical regions remote from the irradiated area, while contralateral cortical structures were mildly hyperemic. By 4 h, the zone of severe ischemia had enlarged and its margins were no longer hyperemic. Ipsilateral cortical and some subcortical structures demonstrated significantly depressed levels of LCBF. At 5 days, LCBF throughout both ipsilateral and contralateral cortices was depressed compared with control values. By 15 days, LCBF had returned to control levels in most brain structures shown histopathologically not to be irreversibly damaged. The temporal sequence and magnitude of these hemodynamic alterations are consistent with findings in clinical studies in which repeated measurements of CBF have been carried out in patients with acute stroke. The ability to produce a cortical infarct that results in a consistent pattern of altered CBF should facilitate the investigation of stroke mechanisms responsible for these hemodynamic abnormalities.