Evaluation of critically perfused area in acute ischemic stroke for therapeutic reperfusion: a clinical PET study

CT volume/density ratio as the marker of ischaemic brain injury

OBJECTIVES

We believe that the CT volume/density ratio (VDR) of infarcted area reflects the degree of brain tissue damage during ischaemic stroke (IS).

PATIENTS AND METHODS

Forty six patients with IS were prospectively enrolled into the study. CT scan was performed on days 1 and 10 of hospitalization. S100BB serum level, gelatinase activities (MMP-2 and MMP-9) and neurological examination (NIHSS) were performed on days 1, 5 and 10 of IS. After 3 months, 42 patients were examined by functional disability scales: Barthel index (BI) and modified Rankin scale (mRS).

RESULTS

The VDR of ischaemic focus correlated well with the average S100BB serum level, MMP-9 serum activity and NIHSS score. The weak but statistically significant relationships were noticed between the VDR vs BI and mRS estimated 3 months after stroke.

CONCLUSION

VDR reflects well the damage ratio of brain tissue during IS. In addition, the study underlines the relationship between VDR vs patients' neurological status and disability after IS.

Recommendations for Comprehensive Stroke Centers

Background and Purpose— To develop recommendations for the establishment of comprehensive stroke centers capable of delivering the full spectrum of care to seriously ill patients with stroke and cerebrovascular disease. Recommendations were developed by members of the Brain Attack Coalition (BAC), which is a multidisciplinary group of members from major professional organizations involved with the care of patients with stroke and cerebrovascular disease.

Summary of Review— A comprehensive literature search was conducted from 1966 through December 2004 using Medline and Pub Med. Articles with information about clinical trials, meta-analyses, care guidelines, scientific guidelines, and other relevant clinical and research reports were examined and graded using established evidence-based medicine approaches for therapeutic and diagnostic modalities. Evidence was also obtained from a questionnaire survey sent to leaders in cerebrovascular disease. Members of BAC reviewed literature related to their field and graded the scientific evidence on the various diagnostic and treatment modalities for stroke. Input was obtained from the organizations represented by BAC. BAC met on several occasions to review each specific recommendation and reach a consensus about its importance in light of other medical, logistical, and financial factors.

Conclusions— There are a number of key areas supported by evidence-based medicine that are important for a comprehensive stroke center and its ability to deliver the wide variety of specialized care needed by patients with serious cerebrovascular disease. These areas include: (1) health care personnel with specific expertise in a number of disciplines, including neurosurgery and vascular neurology; (2) advanced neuroimaging capabilities such as MRI and various types of cerebral angiography; (3) surgical and endovascular techniques, including clipping and coiling of intracranial aneurysms, carotid endarterectomy, and intra-arterial thrombolytic therapy; and (4) other specific infrastructure and programmatic elements such as an intensive care unit and a stroke registry. Integration of these elements into a coordinated hospital-based program or system is likely to improve outcomes of patients with strokes and complex cerebrovascular disease who require the services of a comprehensive stroke center.

Neuroprotection in acute ischaemic stroke. II: Clinical potential

In the 4 years since our first article, there has been considerable progress in our understanding of the pathophysiology of acute ischaemic stroke, and the results of well-conducted trials have at last begun to change everyday clinical practice. The timing of the various processes of the ischaemic cascade and the potential time windows for different interventions are better understood. Furthermore, the importance of maintaining cerebral perfusion and optimizing systemic physiological and biochemical factors in order to prevent neurological deterioration ('progressing stroke') is increasingly being realized. Numerous antithrombotic and neuroprotective drugs have been evaluated in clinical trials, and while none has shown unequivocal benefits on its own, prospects for successful intervention are still good. This will probably involve different combinations of treatments targeted on different pathophysiological stroke types, so that the management of acute stroke will offer a considerable challenge to the stroke physicians of the future.

Repeat positron emission tomographic studies in transient middle cerebral artery occlusion in cats: residual perfusion and efficacy of postischemic reperfusion

The wider clinical acceptance of thrombolytic therapy for ischemic stroke has focused more attention on experimental models of reversible focal ischemia. Such models enable the study of the effect of ischemia of various durations and of reperfusion on the development of infarctions. We used high-resolution positron emission tomography (PET) to assess cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), oxygen extraction fraction (OEF), and cerebral metabolic rate of glucose (CMRglc) before, during, and up to 24 h after middle cerebral artery occlusion (MCAO) in cats. After determination of resting values, the MCA was occluded by a transorbital device. The MCA was reopened after 30 min in five, after 60 min in 11, and after 120 min in two cats. Whereas all cats survived 30-min MCAO, six died after 60-min and one after 120-min MCAO during 6-20 h of reperfusion. In those cats surviving the first day, infarct size was determined on serial histologic sections. The arterial occlusion immediately reduced CBF in the MCA territory to < 40% of control, while CMRO2 was less affected, causing an increase in OEF. Whereas in the cats surviving 24 h of reperfusion after 60- and 120-min MCAO, OEF remained elevated throughout the ischemic episode, the initial OEF increase had already disappeared during the later period of ischemia in those cats that died during the reperfusion period. After 30-min MCAO, the reperfusion period was characterized by a transient reactive hyperemia and fast normalization of CBF, CMRO2, and CMRglc, and no or only small infarcts in the deep nuclei were found in histology. After 60- and 120-min MCAO, the extent of hyperperfusion was related to the severity of ischemia, decreased CMRO2 and CMRglc persisted, and cortical/subcortical infarcts of varying sizes developed. A clear difference was found in the flow/metabolic pattern between surviving and dying cats: In cats dying during the observation period, extended postischemic hyperperfusion accompanied large defects in CMRO2 and CMRglc, large infarcts developed, and intracranial pressure increased fatally. In those surviving the day after MCAO, increased OEF persisted over the ischemic episode, postischemic hyperperfusion was less severe and shorter, and the perfusional and metabolic defects as well as the final infarcts were smaller. These results stress the importance of the severity of ischemia for the further course after reperfusion and help to explain the diverging outcome after thrombolysis, where a relation between the residual flow and the effectiveness of reperfusion was also observed.

Accumulation of L-[2-(F-18)]fluorophenylalanine in peri-infarct area in a patient with acute cerebral infarction

We studied the brain uptake of amino acid in a patient with acute cerebral infarction with L-[2-(F-18)]fluorophenylalanine and positron emission tomography. The increased accumulation of the ligand was specifically found in the peri-infarct area where oxygen metabolism was still maintained but decreased later in the 72-day follow-up period. The kinetic analysis revealed that increased accumulation was not due to increased transport from the blood to the brain but delayed washout from the brain to the blood. Although the mechanism is still unknown, abnormally high accumulation of L-[F-18]fluorophenylalanine may predict delayed neuronal changes after ischemic insults of the brain.