Magnetic resonance techniques for the identification of patients with symptomatic carotid artery occlusion at high risk of cerebral ischemic events

Imaging Acute Stroke: From One-Size-Fit-All to Biomarkers

In acute stroke management, time window has been rigidly used as a guide for decades and the reperfusion treatment is only available in the first few limited hours. Recently, imaging-based selection of patients has successfully expanded the treatment window out to 16 and even 24 h in the DEFUSE 3 and DAWN trials, respectively. Recent guidelines recommend the use of imaging techniques to guide therapeutic decision-making and expanded eligibility in acute ischemic stroke. A tissue window is proposed to replace the time window and serve as the surrogate marker for potentially salvageable tissue. This article reviews the evolution of time window, addresses the advantage of a tissue window in precision medicine for ischemic stroke, and discusses both the established and emerging techniques of neuroimaging and their roles in defining a tissue window. We also emphasize the metabolic imaging and molecular imaging of brain pathophysiology, and highlight its potential in patient selection and treatment response prediction in ischemic stroke.

[Cognitive impairment in patients with metabolic syndrome. The current treatment possibilities]

AIM

To study the effect of therapy with cytoflavin on cognitive function in patients with metabolic syndrome (MS).

MATERIAL AND METHODS

The randomized controlled open study included 156 patients with MS. The mean age was 41.27±5.16 years. The duration of observation was 16 weeks. The main group of patients (n=78) received cytoflavin in the dose of 2 tablets 2 times a day. Patients in the control group (n=78) received basic therapy. All patients underwent neuropsychological testing at baseline, after 2 months and at the end of the study. Cognitive evoked potentials (Р300) were recorded to assess cognitive functions. The levels of plasma glucose and lipid profile were measured.

RESULTS

Cytoflavin improved cognitive functions. Two months after treatment, the results of neuropsychological testing and electrophysiological study were better in the main group compared to the control group.

Clinical proton MR spectroscopy in central nervous system disorders

A large body of published work shows that proton (hydrogen 1 [(1)H]) magnetic resonance (MR) spectroscopy has evolved from a research tool into a clinical neuroimaging modality. Herein, the authors present a summary of brain disorders in which MR spectroscopy has an impact on patient management, together with a critical consideration of common data acquisition and processing procedures. The article documents the impact of (1)H MR spectroscopy in the clinical evaluation of disorders of the central nervous system. The clinical usefulness of (1)H MR spectroscopy has been established for brain neoplasms, neonatal and pediatric disorders (hypoxia-ischemia, inherited metabolic diseases, and traumatic brain injury), demyelinating disorders, and infectious brain lesions. The growing list of disorders for which (1)H MR spectroscopy may contribute to patient management extends to neurodegenerative diseases, epilepsy, and stroke. To facilitate expanded clinical acceptance and standardization of MR spectroscopy methodology, guidelines are provided for data acquisition and analysis, quality assessment, and interpretation. Finally, the authors offer recommendations to expedite the use of robust MR spectroscopy methodology in the clinical setting, including incorporation of technical advances on clinical units.

MAGNETIC RESONANCE SPECTROSCOPY IN EVALUATION OF COGNITIVE FUNCTIONS IN PATIENTS WITH METABOLIC SYNDROME

Objective. To evaluate the role of magnetic resonance spectroscopy (MR-spectroscopy) in the study of cognitive functions in patients with metabolic syndrome (MS).

Design and methods. The study included patients with MS (10 patients without cognitive impairment and 11 subjects with cognitive dysfunction). All patients underwent neuropsychological testing, and cognitive evoked potential for the assessment of cognitive functions. Brain metabolism was studied by proton MR-spectroscopy.

Results. In patients with MS and cognitive impairment, and without cognitive dysfunction no morphological changes in the brain according to the magnetic resonance imaging (MRI) were found. According to MR-spectroscopy of the brain in patients with MS and cognitive dysfunction the metabolism impairment is primarily associated with the increase in lactate and inositol.

Conclusion. Indicators of neuropsychological testing, the cognitive evoked potential are associated with the violation of brain metabolism in patients with MS and cognitive impairment.

Proton magnetic resonance spectroscopy in patients with symptomatic unilateral internal carotid artery / middle cerebral artery stenosis or occlusion

PURPOSE

To explore the value of proton magnetic resonance spectroscopy imaging ((1)H-MRSI) in patients with stenosis or occlusion of the internal carotid artery (ICA) / middle cerebral artery (MCA).

MATERIALS AND METHODS

Fifty noninfarcted patients with stenosis or occlusion of unilateral ICA/MCA were included in our study. In the meantime, 25 patients with cerebral infarction and 25 healthy control subjects were enrolled. All patients and healthy control subjects underwent (1)H-MRSI. Cerebral metabolic changes were studied in the noninfarcted patients and compared with the infarcted patients as well as healthy control subjects.

RESULTS

In 50 noninfarcted patients N-acetylaspartate (NAA) decreased and choline increased in the ischemic hemisphere compared with the contralateral side and control subjects. Lactate peaks were observed in 12 patients. The metabolic changes were relatively slight but were associated with metabolic disruption in infarcted patients. There were relationships between metabolic abnormalities and neurological status of the noninfarcted patients.

CONCLUSION

(1)H-MRSI can demonstrate abnormal metabolic changes in cerebral tissues with no infarction, while with ICA/MCA may show stenosis or occlusion at an early stage, which may help guide treatment decisions and preoperative evaluation.

Outcome in patients with stroke associated with internal carotid artery occlusion

BACKGROUND

The clinical outcome in patients with stroke associated with internal carotid artery (ICA) occlusion is poor, although a minority may recover without dependency. The purposes of this study were (1) to assess the predictive factors of adverse outcome in patients with stroke associated with an occlusion of the ICA and (2) to evaluate the rate of spontaneous recanalization of an occluded ICA.

METHODS

A total of 177 consecutive patients with first-ever ischemic stroke associated with ICA occlusion were prospectively examined from the Perugia Stroke Registry. Mean age was 71.4 +/- 14.3 years; 53% were males. Multiple regression models were used to analyze predictors of mortality, dependency and ipsilateral stroke recurrence.

RESULTS

The most probable cause of occlusion was atherosclerosis in 65%, cardioembolism in 22%, dissection in 9% and other causes in 4%. Thirty percent of the patients died within 30 days. After a mean follow-up of 420 days (range 1-1,970 days), 45% of the patients had died and 75% had died or were disabled. Another 6% of the patients had a recurrent stroke ipsilateral to the occluded carotid artery. Age was the only predictor of 30-day mortality (77.7 +/- 9.7 vs. 68.7 +/- 15.2 years; p = 0.03) and of long-term mortality or disability (p < 0.003). Hypertension (OR 0.42; 95% CI 0.17-1.00; p = 0.05) was associated with a better outcome within 30 days from stroke onset. Previous ipsilateral transient ischemic attack (OR 0.24; 95% CI 0.06-0.89; p = 0.03) and hyperlipidemia (OR 0.38; 95% CI 0.15-0.99; p = 0.049) were predictors of a better outcome with respect to long-term mortality or disability. No predictors of ipsilateral stroke recurrence were found. One hundred and five out of 177 patients had adequate follow-up ultrasound data. After a mean follow-up of 1.8 years, 10 patients had recanalization of the occluded ICA (2/71 atherosclerosis, 3/19 cardioembolism and 5/15 dissection).

CONCLUSIONS

After a mean follow-up of 1.2 years, 45% of the patients with stroke associated with ICA occlusion had died, while 75% had died or were functionally dependent. The presence of either previous ipsilateral transient ischemic attack, hypertension or hyperlipidemia was associated with a favorable outcome. Recanalization of an occluded ICA occurred in a minority of patients and it was associated with cardioembolism and with arterial dissection.

Extracranial-intracranial arterial bypass surgery improves total brain blood supply in selected symptomatic patients with unilateral internal carotid artery occlusion and insufficient collateralization

It remains controversial whether extracranial-intracranial (EC-IC) arterial bypass surgery leads to a significant increase in brain blood supply, allowing the reversal of regional cerebral hypoperfusion in symptomatic patients with occlusive cerebrovascular disease and hemodynamic impairment. The aim of the present study was to determine the effects of EC-IC bypass surgery on cerebral brain-supplying blood volume flow (BVF; ml/min) from a purely hemodynamic point of view, using 2D cine phase-contrast MR imaging. Twenty-five patients with symptomatic, unilateral internal carotid artery (ICA) occlusion and hemodynamic compromise received EC-IC arterial bypass surgery. All patients underwent quantitative BVF measurements of brain-supplying arteries preoperatively and postoperatively, including the direct BVF measurement in the established EC-IC bypass after surgery. Preoperatively, total brain BVF was reduced in comparison to normal controls (595 +/- 89 vs 663 +/- 49 ml/min; [mean +/- SEM]; p = 0.039). Mean BVF through the EC-IC bypass reached 84 +/- 32 ml/min (range: 14-177 ml/min), leading to a significant net increase in total BVF of 78 +/- 43 ml/min (range: 7-136 ml/min) when compared with BVF prior to surgery (p < 0.001), with resulting postoperative BVF reaching values obtained in normal controls. EC-IC arterial bypass surgery increases total brain blood supply, allowing restoration of local perfusion in hemodynamically compromised brain tissue in patients with symptomatic ICA occlusion.

Cerebral bloodflow and oxygen metabolism in borderzone and territorial infarcts due to symptomatic carotid artery occlusion

It remains controversial whether borderzone infarcts are due to compromised cerebral perfusion and whether territorial infarcts are caused by artery-to-artery emboli in case of occlusion of the internal carotid artery. The present positron emission tomography study compares with normal controls, the average regional cerebral bloodflow (rCBF), regional oxygen extraction fraction (rOEF) and regional cerebral metabolic rate for oxygen (rCMRO(2)) in the infarct area, the peri-infarct zone, the remaining homolateral hemisphere and in the contralateral hemisphere of 10 patients with borderzone and 17 patients with territorial infarcts, due to internal carotid artery occlusion by atherosclerosis and by cervical dissection. The steady-state technique with oxygen-15 was used. A nearly significant increase of rOEF with lowered rCBF and rCMRO(2) was observed in the peri-infarct zone of patients with territorial infarcts. In patients with borderzone infarcts rCMRO(2) was decreased in the peri-infarct zone, in the remaining homolateral hemisphere and in the contralateral hemisphere without changes in rCBF and rOEF. The present study finds no arguments that impaired cerebral perfusion is a more frequent cause of borderzone than of territorial infarcts.

Cobalt-55 positron emission tomography in symptomatic atherosclerotic carotid artery disease: borderzone versus territorial infarcts

BACKGROUND

Borderzone as well as territorial infarcts can occur in severe atherosclerotic carotid artery disease. It remains controversial whether the borderzone distribution of infarcts is due to hypoperfusion or due to artery-to-artery embolism.

PURPOSE

The present study investigates whether cobalt-55 (55Co) positron emission tomography (PET) shows a different pattern of ischaemia according to the topography of the infarct in severe atherosclerotic carotid artery disease.

PATIENTS AND METHODS

Five patients with a cortical borderzone and seven with a territorial infarct, due to symptomatic carotid artery disease, were investigated with 55Co PET 3-6 months after stroke. Average 55Co counts in the infarct area, the adjacent cortical zone, the deep white matter and, contralateral cerebral cortex and white matter, were compared to the values in the cerebellum used as reference.

RESULTS

No differences in 55Co ratio were observed in the different regions of interest (ROIs) between patients with cortical borderzone and those with territorial infarcts. The 55Co uptake was similar or lower than the reference value for all ROIs in all individual patients.

CONCLUSION

In patients with borderzone as well as with territorial infarcts no evidence was found for subclinical ischaemic injury in or around the infarcts. These data do support the conclusion that cortical borderzone infarcts may not be due to ongoing chronic haemodynamic impairment, but by no means is this conclusive evidence.

Cerebral blood flow and oxygen metabolism in symptomatic internal carotid artery occlusion by atherosclerosis and by cervical dissection

Symptomatic internal carotid artery occlusion by atherosclerosis and by cervical dissection are distinct conditions with different long-term prognoses. The purpose of the present study is to investigate if regional cerebral blood flow and oxygen metabolism, after onset of stroke, differ between both conditions. Seventeen patients with symptomatic unilateral atherosclerotic internal carotid occlusion and 10 patients with symptomatic internal carotid occlusion due to cervical dissection were submitted to a positron emission tomographic (PET) study between 1 and 2 months after stroke onset. The steady state technique with 15O was used in order to determine regional cerebral blood flow, regional oxygen extraction fraction, and regional cerebral metabolic rate for oxygen in the infarct area, the peri-infarct zone, the remaining homolateral hemisphere, and the contralateral hemisphere. The results were compared between both patient's populations. The patients with cervical dissection were on average much younger than those with atherosclerotic occlusion, but neurological impairment on admission and disability at 3 months were comparable. Between both patient populations, no differences in rCBF, rOEF, and rCMRO2 could be demonstrated in the different regions of interest when the results were age-adjusted. Except for age-related changes, no differences in PET findings could be demonstrated between patients with symptomatic internal carotid occlusion caused by either atherosclerosis or cervical dissection.

Carotid surgery in acute symptomatic patients

OBJECTIVES

evaluation of urgent carotid artery surgery with new diagnostic techniques and changing surgical considerations at a university hospital.

DESIGN, MATERIAL AND METHODS

prospective monitoring and assessment of outcome in 67 patients who underwent urgent carotid surgery because of symptomatic extracranial carotid artery involvement. Patients were examined via the stroke unit: duplex sonography was mandatory for diagnosis of extracranial carotid artery disease, as was proof of an open middle cerebral artery (MCA). Assessment of intracerebral damage followed CT or MR imaging procedures. Perioperative and surgical management was standardized. Neurological impairment was assessed pre-, postoperatively and at follow-up using the Rankin scale. "Urgent" was defined as "immediate" after the final diagnostic step had been performed.

RESULTS

within a period of 26 months 67 symptomatic patients (58% stroke, 42% TIA) underwent urgent carotid surgery. Median time from admission to surgery was 2 days. In all but five cases flow through the ICA could technically be restored (93%). Thirty-day mortality was 3% and disease-related morbidity 13%. The one and two year survival rates were 92 and 90%, respectively. No ipsilateral recurrent stroke occurred during follow-up.

CONCLUSIONS

clinical decision-making based on stratified diagnostic workup by means of extra- and intracranial as well as intracerebral hemodynamics using new imaging techniques may select patients who will benefit more from urgent surgery than from conservative management.

Management of patients with symptomatic carotid artery occlusion

The annual risk of stroke in patients with symptomatic carotid artery occlusion (CAO) and impaired cerebral blood flow (CBF) is approximately 10%. Increased oxygen extraction fraction measured by positron emission tomography (PET) and low cerebrovascular reactivity assessed by transcranial Doppler is associated with an increased risk of recurrent ischemic stroke in these patients. Recently, other risk factors have been identified: (1) symptoms of purported hemodynamic origin; (2) ongoing symptoms in the presence of documented symptomatic CAO; (3) leptomeningeal collaterals visible on angiography; and (4) low NAA/choline ratio on magnetic resonance (MR) spectroscopy. Evidence is growing that a second extracranial-intracranial (EC-IC) bypass trial might be worthwhile in patients with symptomatic CAO. Probably, only patients with ongoing symptoms and compromised CBF should be included in such a trial. Current evidence based therapeutic options for patients with symptomatic CAO include antithrombotic medication and control of vascular risk factors. For stenosis of the contralateral internal or ipsilateral external carotid artery endarterectomy may be considered. Ongoing symptoms may cease after tapering of antihypertensive medication.

CT angiography and MR angiography in the evaluation of extracranial carotid vascular disease

CTA and MRA techniques likely will continue to increase in use in the evaluation of the extracranial cerebrovascular system. The increasing reliance on noninvasive tests mirrors an overall concern with the risks and costs of more invasive examinations. Given the rapid development of the computer technology, data acquisition, and reconstruction algorithms in the past few years, it is apparent that CTA and MRA also will continue to improve.