Symptomatic carotid artery occlusion. A reappraisal of hemodynamic factors

Ultrasonographic and perioperative macroscopic findings in acute carotid artery occlusion

BACKGROUND AND PURPOSE

acute ischemic stroke (AIS) may occur both in the acute and chronic internal carotid artery occlusion (ICAo). Thus, it is important to assess the ICAo character when considering the recanalization method. The aim was to assess the agreement between the ultrasonographic (US) and perioperative macroscopic (PM) finding in AIS patients with acute ICAo, undergoing an emergent carotid endarterectomy.

METHODS

in a retrospective, hospital-based study, the set consisted of 47 patients (36 males; age 49-79, mean 63.7 ± 8.5 years). ICAo character was classified as an acute thromboembolus either isolated or in combination with atherosclerotic plaque using the US (B-mode) and the PM evaluation. Cohen's Kappa and AC(1) coefficient were applied to assess the methods agreement.

RESULTS

an acute ICAo character diagnosed by US was confirmed by the PM evaluation in all cases. US and PM findings were consistent in 41 cases. The agreement between both methods in the classification of acute ICAo was 87.2% [95% confidence interval (CI): 77.7-96.8%], κ= .589 (95% CI: .293-.885) (P < .0001), AC(1) = .815.

CONCLUSIONS

US is a reliable method in the diagnostics of the acute character of ICAo and it has a good agreement with PM finding regarding a differentiation of atherosclerotic plaque and fresh thromboembolus.

Cerebral hemodynamics as a predictor of stroke in adult patients with moyamoya disease: a prospective observational study

Moyamoya disease is an obliterative vasculopathy of the large arteries at the base of the brain. In the US, it most commonly affects women in their 3rd and 4th decades of life, frequently causing ischemic stroke. The natural history of this disorder is not well described. It is very likely that hemodynamic factors play an important role in the risk of future stroke, as has been established in atherosclerotic carotid occlusive disease. The authors describe an ongoing, prospective observational study designed to test the hypothesis that increased oxygen extraction in the cerebral hemisphere beyond the occlusive lesion is a predictor of subsequent risk of ipsilateral stroke in medically treated patients with moyamoya phenomenon. On enrollment, all patients undergo regional measurements of cerebral oxygen extraction fraction (OEF) with PET. Information on baseline clinical, laboratory, epidemiological, and angiographic risk factors are obtained at the time of the PET study. Decisions regarding surgery are made by the treating physicians based on clinical information while being blinded to PET data. Patients undergo follow-up at 6-month intervals to determine the subsequent risk of ipsilateral stroke. All patients will return at 1 and 3 years for repeat PET studies. Secondary, exploratory, aims of this longitudinal and blinded study are to determine other predictive factors for stroke in this population; to determine preliminary estimates of the effects of different medical treatment regimens in this population; to determine the temporal changes in hemodynamic impairment in medically treated patients; to determine the effects of surgery on hemodynamic impairment in the subset of patients who undergo surgical revascularization; and to obtain estimates of surgical complication rates for patients with and without hemodynamic impairment.

The role of indirect extracranial-intracranial bypass in the treatment of symptomatic intracranial atheroocclusive disease

Object

The optimal treatment of medically refractory intracranial atheroocclusive disease remains unclear. The EC-IC Bypass Study Investigators found that patients with internal carotid and middle cerebral artery (ICA and MCA) occlusion received no benefit from direct superficial temporal artery to MCA bypass, and that patients with ICA occlusion and MCA stenosis may have actually fared worse after surgery, perhaps in part due to flow reversal in critical perforator-bearing segments. Although the results of recent investigations have suggested that direct bypass may be beneficial in a subgroup of patients with hemodynamic failure secondary to unilateral ICA occlusion, similar data do not exist for patients with hemodynamic failure from other intracranial stenoocclusive diseases. Indirect bypass via encephaloduroarteriosynangiosis offers a surgical alternative that may avoid rapid flow reversal while providing additional flow to at-risk, distal vascular territories.

Methods

Twelve patients with medically resistant hemodynamic failure from intracranial atheroocclusive disease underwent indirect vascular bypass. Eight patients had ICA occlusion and coexistent MCA stenosis, 1 patient had tandem ICA stenoses and MCA stenosis, 1 patient had tandem ICA and MCA occlusion, 1 patient had ICA and posterior cerebral artery occlusion and an ischemic hemisphere supplied via a proximal superficial temporal artery branch, and 1 patient had poor donor arteries and severe medical comorbidities that precluded the use of general anesthesia. Patient evaluation included clinical assessment of neurological status, CT scanning, MR imaging, digital subtraction angiography, and transcranial Doppler ultrasonography with CO2 reactivity, or SPECT with acetazolamide challenge. Patient records were reviewed and patients were interviewed for outcome assessment, including transient ischemic attack (TIA), cerebral infarction, change in cerebral perfusion, graft patency, and functional level according to the modified Rankin scale. Kaplan-Meier cumulative failure curves for the primary end point of cerebral infarction were used to compare these patients to a control group of 81 patients derived from the literature who received medical management for severe symptomatic hemodynamic failure.

Results

Eleven patients underwent encephaloduroarteriosynangiosis and 1 patient received bur holes with dural and arachnoid incisions; the mean length of follow-up was 51.2 ± 40.1 months. Five patients had decreased perfusion on follow-up despite graft patency, and 10 patients suffered new infarctions or TIAs during the follow-up period. Five patients (42%) suffered infarctions within 1 year of surgery. A meta-analysis of 4 studies of patients with symptomatic ICA occlusion and severe hemodynamic failure who underwent medical treatment revealed a new infarction rate of 30% in the first year after entry into the study. There was no significant difference between patients with severe hemodynamic failure who underwent surgery and those in the medically treated control group (log-rank test, p = 0.179).

Conclusions

The authors found that indirect bypass does not promote adequate pial collateral artery development and appears to be of limited utility in patients with symptomatic ICA or MCA stenoocclusive disease and secondary hemodynamic failure. Rates of postoperative TIAs or cerebral infarctions after indirect bypass in this patient population do not differ from previous reports in patients who received medical management only.

Predictors of patency of excimer laser–assisted nonocclusive extracranial-to-intracranial bypasses

Object

Excimer laser–assisted nonocclusive anastomosis (ELANA) is a technique that can be used for extracranial-to-intracranial (EC-IC) bypasses, without the necessity of temporary occlusion of the donor or recipient artery. Information on predictors of patency of EC-IC bypasses in general and the ELANA bypass in particular is sparse. The authors studied 159 ELANA EC-IC bypasses to find predictors of patency.

Methods

From a prospective database of patients who underwent EC-IC bypass surgery, 143 consecutive patients who underwent a total of 159 ELANA bypasses were studied. The associations of patient characteristics, surgical aspects, and technical aspects specific to the ELANA technique with intraoperative and postoperative bypass patency were studied using logistic regression analysis.

Results

At the end of the operation, 146 (92%) of the 159 bypasses were patent. A first attempt to create a bypass was almost 8 times more likely (OR 7.6, 95% CI 2.1–27.5; p = 0.02) to result in a patent bypass than a second attempt. Administration of a small amount of heparin during the operation was also associated with bypass patency (OR 5.2, 95% CI 1.1–24.9; p = 0.04). One hundred twenty-three (77%) of the 159 bypasses were functional at patency assessments during the 1st month after the operation. Older age (OR 1.043 for every year of increase in age, 95% CI 1.010–1.076; p = 0.01), male sex (OR 2.9, 95% CI 1.3–6.5; p = 0.01), and high intraoperative bypass flow (OR 1.017 for every milliliter per minute increase in flow, 95% CI 1.004–1.030; p = 0.01) were associated with postoperative bypass patency.

Conclusions

Attempts to create a second EC-IC ELANA bypass after the first one are more likely to fail, whereas administration of heparin to the patient during the procedure increases the intraoperative bypass patency rate. Postoperative patency results are better in male and in older patients. Intraoperative bypass flow measurements are essential because high bypass flow is an important determinant of postoperative patency.

The evolution of cerebral revascularization surgery

Among the relatively few surgeons to be awarded the Nobel Prize was Alexis Carrel, a French surgeon and pioneer in revascularization surgery at the turn of the 20th century. The authors trace the humble beginnings of cerebral revascularization surgery through to the major developments that helped shape the modern practice of cerebral bypass surgery. They discuss the cornerstone studies in the development of this technique, including the Extracranial/Intracranial Bypass Study initiated in 1977. Recent innovations, including modern techniques to monitor cerebral blood flow, microanastomosis techniques, and ongoing trials that play an important role in the evolution of this field are also evaluated.

Symptomatic late recanalization of an occluded internal carotid artery: a case report and review of the literature

The natural history of patients with carotid artery occlusion is poorly understood, and patients are usually offered conservative treatment as the difficulty and risks of surgical intervention are thought to outweigh the natural history of the condition. The case of a 71-year-old male patient with symptomatic internal carotid artery stenosis in a previously occluded vessel is presented. This case suggests that symptomatic recanalization of an occluded carotid artery may occur and long-term duplex surveillance may be a justifiable strategy in this patient group.

Total occlusion of the common carotid artery: a modified classification and its relation to clinical status

To investigate the hemodynamics and clinical presentation of common carotid artery occlusion (CCAO), we reviewed 6,415 patients with suspected carotid artery disease in whom a color Duplex imaging (CDI) examination was performed. According to distal vessel patency, the following CDI classification of CCAO was adopted: type I (patent both distal vessels); type II (isolated patency of external carotid artery); type III (isolated patency of internal carotid artery); and type IV (both distal vessels occluded). Thirty-five (0.5%) cases met the CDI criteria for CCAO. Twenty-nine of those (83%) had at least one patent distal vessel. Ten patients (29%) presented with stroke, 20 (57%) with transient ischemic attacks (TIAs) and five (14%) were asymptomatic. The incidence of stroke was higher in type IV (50%) vs. type II (30%) and in type II vs. type I (10%) lesions. Similarly, TIAs presented more often in type II (67%) and IV (50%) vs. in type I (40%) lesions (p = 0.002). Retrograde flow in the ophthalmic artery and concomitant severe contralateral carotid artery stenosis were more often related with type II and IV lesions (p = 0.02 and 0.04, respectively). CCAO is usually accompanied by patent distal vessel(s). The proposed CCAO classification correlates well with the patients' clinical status and may help to better clarify the outcome of this rare entity. Among the main arteries of the developed collateral circulation, only the flow direction in the ophthalmic artery may be of clinical value.

Hemodynamic and metabolic changes after carotid endarterectomy in patients with high-degree carotid artery stenosis

In symptomatic stenosis of the internal carotid artery (ICA), the predominant mechanism of ischemic event is considered thromboembolic. Carotid endarterectomy (CEA) removes the embolic source and is accepted as the major benefit from the surgery. Even in high-degree stenosis, hemodynamic compromise as a causal factor for cerebral ischemia remains controversial, however. We used positron emission tomography (PET) to evaluate possible hemodynamic and/or metabolic changes caused by a severe ICA stenosis and the subsequent changes after CEA. Subjects consisted of 10 patients with recent transient ischemic attack and/or minor stroke whose carotid stenosis exceeded 80% (mean, 92%). We measured regional cerebral blood flow (CBF), oxygen extraction fraction (OEF), oxygen metabolic rate (CMRO2), and regional cerebral blood volume (CBV) before and after the CEA. In addition, we calculated CBF/CBV value as an indicator of tissue perfusion reserve. We compared these PET values to those of 15 age-matched normal controls. Significant reductions in CBF, CBF/CBV, and CMRO2 values were observed in the hemisphere not only ipsilateral, but also contralateral to the stenosis. In 4 patients, an increase in OEF and decrease in CBF/CBV were also detected. These variables significantly recovered after CEA. High-degree carotid stenosis in the tested range reduces cerebral hemodynamic and metabolic reserve and forms a vulnerable environment in the brain. Successful CEA benefits not only by removing embolic source, but also by improving hemodynamic status, which may be seen in even the contralateral hemisphere.

Superficial temporal artery to middle cerebral artery bypass: past, present, and future

OBJECT

The aim of this study was to review the historical developments and current status of superficial temporal artery (STA) to middle cerebral artery (MCA) bypass.

METHOD

A literature review was performed to review the origins and current uses of the STA bypass procedure in neurosurgery.

RESULTS

The idea of providing additional blood supply to the brain to prevent stroke and maintain neurological function has been present in the mind of neurosurgeons for many decades. In 1967 the first STA-MCA bypass was done by M. G. Yaşargil, and an enormous step was made into the field of microneurosurgery and cerebral revascularization. During the decades that followed, this technique was used as an adjuvant or a definitive surgical treatment for occlusive disease of the extracranial and intracranial cerebral vessels, skull base tumors, aneurysms, carotid-cavernous fistulas, cerebral vasospasm, acute cerebral ischemia, and moyamoya disease. With the results of the first randomized extracranial-intracranial (EC-IC) bypass trial and the development of endovascular techniques such as angioplasty for intracranial atherosclerotic disease and cerebral vasospasm, the indications for STA-MCA bypass became limited. Neurosurgeons continued to perform EC-IC bypasses as an adjuvant to clipping of aneurysms and in the treatment of skull base tumors and moyamoya disease; the procedure is less commonly used for atherosclerotic carotid artery occlusion (CAO) with definite evidence of hemodynamic insufficiency. The evidence that patients with symptomatic CAO and "misery perfusion" have an increased stroke risk has prompted a second trial for evaluating EC-IC bypass for stroke prevention. The Carotid Occlusion Surgery Study is a new trial designed to determine whether STA-MCA bypass can reduce the incidence of stroke in these patients. New trials will also reveal the role of the STA-MCA bypass in the prevention of hemorrhages in moyamoya disease.

CONCLUSIONS

The role of STA-MCA bypass in the management of cerebrovascular disease continues to be refined and evaluated using advanced imaging techniques and by performing randomized trials for specific purposes, including symptomatic CAO.

Outcome analysis of carotid artery occlusion

The outcome of carotid artery occlusion was studied through the retrospective identification of 115 affected patients. The majority were white (77%) males (61%) with multiple atherogenic risk factors and suffering ipsilateral stroke (57%). Those patients presenting with stroke were not distinguished by demographic features, risk factors, lipid profile, medical regimen, or subsequent mortality when compared with those without. Overall, 36 patients (31%) required contralateral carotid endarterectomy (CEA), with one (2.8%) perioperative stroke, whereas 4 (3%) underwent ipsilateral external CEA without incident. With 81% follow-up (mean 3.9 years), the overall mortality of the group was 46%; the annualized risk of ipsilateral stroke was 1.6%. This study documents a significant risk of stroke and contralateral occlusive disease with ipsilateral carotid artery occlusion, which cannot be reliably predicted by clinical criteria. Duplex surveillance is valuable, but flow velocity measurements alone may be misleading. Surgical endarterectomy can be performed with an acceptable rate of perioperative stroke.

CT angiography is cost-effective for confirmation of internal carotid artery occlusions

BACKGROUND AND PURPOSE

While sensitive to internal carotid artery (ICA) occlusion, carotid ultrasound can produce false-positive results. CT angiography (CTA) has a high specificity for ICA occlusion and is safer and cheaper than catheter angiography, although less accurate. We determined the cost-effectiveness of CTA versus catheter angiography for confirming an ICA occlusion first suggested by carotid ultrasound.

METHODS

A Markov decision-analytic model was constructed to estimate the cost-effectiveness of CTA compared with catheter angiography in a hypothetical cohort of symptomatic patients with a screening examination consistent with an ICA occlusion. Costs in 2004 dollars were estimated from Medicare reimbursement. Effectiveness was measured in quality-adjusted life years.

RESULTS

The 2-year cost in the CTA scenario was $9,178, and for catheter angiography, $11,531, consistent with a $2,353 cost-savings per person for CTA. CTA resulted in accrual of 1.83 quality-adjusted life years while catheter angiography resulted in 1.82 quality-adjusted life years. CTA was less costly and marginally more effective than catheter angiography. In sensitivity analyses, when CTA sensitivity and specificity were allowed to vary across a plausible range, CTA remained cost-effective.

CONCLUSIONS

After screening examination has suggested an ICA occlusion, confirmatory testing with CTA provides similar effectiveness to catheter angiography and is less costly.

Chronic ischemia and neurocognition

Cognitive impairment from a major stroke as a consequence of carotid disease is an acknowledged clinical outcome; however, cognitive impairment without major stroke is open to discussion. The three recognized mechanisms for cognitive dysfunction from internal carotid artery are microembolization, white-matter disease, and hypoperfusion. The last has been most difficult to characterize physiologically. In this article, the authors review evidence supporting the existence of chronic ischemia in the brain and its direct impact on cognitive functions. By incorporating the pathophysiology of chronic ischemia into the algorithm of the management of carotid artery disease, we may be able to extend the goals of carotid artery revascularization beyond merely preventing stroke to include preventing or reversing cognitive decline.

External carotid artery angioplasty and stenting to augment cerebral perfusion in the setting of subacute symptomatic ipsilateral internal carotid artery occlusion

✓The authors performed external carotid artery (ECA) angioplasty and stenting in a 45-year-old man who had presented with right hemispheric crescendo ischemic symptoms stemming from acute right internal carotid artery occlusion (ICAO). This unique application of ECA angioplasty and stenting augmented cerebral perfusion and improved clinical symptoms. In certain situations, ECA stenting can increase cerebral perfusion in the setting of ICAO and ECA stenosis. The authors are the first to describe this approach in this context.

[Internal carotid artery revascularization]

Carotid endarterectomy remains the standard revascularization technique for the prevention of ischemic stroke resulting from severe carotid stenosis. Surgery is highly beneficial in patients with a symptomatic stenosis of 70% or greater that is not a total or near-total occlusion. The benefit becomes more diluted in patients with a symptomatic 50-69% stenosis, and surgery has no effect, or even increases the risk of stroke, in those with a less than 50% stenosis. Surgery has also been shown to reduce the risk of stroke in asymptomatic patients with a 60-99% stenosis, but the absolute benefit is only 1% per year. There is no clear evidence that surgery benefits asymptomatic women at 5-year follow-up, and the benefit is unknown in asymptomatic patients aged over 75 years. Decision-making must take individual factors into consideration, particularly in patients with an asymptomatic (60-99%) or a moderate (50-69%) symptomatic carotid stenosis, so that the risk-benefit ratio of surgery can be optimized. Current data do not support the preferential use of carotid stenting over carotid endarterectomy in patients with a symptomatic or asymptomatic carotid stenosis who are good candidates for surgery. In those who are not good surgical candidates, carotid stenting might be equivalent to surgery, but whether or not any form of carotid revascularization is superior to medical treatment alone remains unknown.

Recanalization of a Symptomatic Extracranial Internal Carotid Artery Near Occlusion with Proximal and Distal Protection

OBJECTIVE

To describe a novel approach to recanalizing symptomatic extracranial internal carotid artery near occlusion using proximal and distal emboli protection devices.

METHODS

Patients presenting with symptomatic extracranial internal carotid artery near occlusion who underwent endovascular recanalization between October 2004 and July 2005 were included in this study. During these procedures, a 9-French Concentric Balloon Guide Catheter (Concentric Medical, Mountain View, CA) was advanced into the common carotid artery proximal to the site of occlusion. During the prestent angioplasty of the lesion, the proximal balloon was inflated and aspiration was performed. After initial angioplasty and before stent placement, a distal filter protection device was placed in the distal internal carotid artery. Stent placement and repeat angioplasty were performed with both protection devices active. All patients were placed on dual antiplatelet therapy.

RESULTS

There were four patients treated with a mean age of 74 years; three of these four patients were men. All patients had signs of ischemia and carotid occlusion or near occlusion on noninvasive imaging. Three right internal carotid arteries were treated. All patients were successfully recanalized. No procedurally related complications or deaths occurred.

CONCLUSION

This series demonstrates the feasibility of recanalization of symptomatic carotid artery occlusion or near occlusion using proximal and distal emboli protection devices. Such an approach may provide an added level of safety during carotid recanalization procedures.

Perimetric and retrobulbar blood flow changes following carotid endarterectomy

BACKGROUND

Carotid stenosis can produce visual changes. This study examines perimetric and retrobulbar blood flow changes following carotid endarterectomy (CEA) in patients without visual symptoms.

METHODS

Sixteen patients (13 male, three female) with bilateral carotid stenosis were included. Patients with a history of ophthalmic disease, including glaucoma, were excluded. Peak systolic velocity (PSV) in the ophthalmic artery (OA), central retinal artery (CRA), and short posterior ciliary arteries (SPCAs) was measured preoperatively and 12 months following CEA with color Doppler imaging (CDI), using a 7.5 MHz probe, at both the side operated upon and its fellow side. Automated static perimetry (Octopus 500 perimeter, G1x program) was performed at the same intervals. Mean sensitivity (MS), mean defect (MD), loss variance (LV) and corrected loss variance (CLV) were recorded.

RESULTS

Preoperative PSV in the OA was significantly lower in the side operated on. Preoperative perimetric parameters were significantly compromised, compared with normative data, in both eyes. Postoperatively, PSV had significantly improved in all vessels examined in the carotid that was operated on, but only in the OA and SPCAs in the fellow side. MD had significantly improved postoperatively for both eyes, whereas improvement in the other perimetric parameters examined was not statistically significant.

CONCLUSIONS

Perimetric changes occur in carotid stenosis. CEA results in the improvement of retrobulbar blood flow and perimetric parameters. Further research will be required to determine whether perimetric parameters may be used as additional indicators for carotid endarterectomy.

Complete occlusion of extracranial internal carotid artery: clinical features, pathophysiology, diagnosis and management

A complete occlusion of the internal carotid artery (ICA) is an important cause of cerebrovascular disease. A never-symptomatic ICA occlusion has a relatively benign course, whereas symptomatic occlusion increases future risk of strokes. Ultrasonography, magnetic resonance imaging and contrast angiography are useful diagnostic tests, and functional imaging of the brain (eg, with positron emission tomography) helps to understand haemodynamic factors involved in the pathophysiology of brain ischaemia. Recently, there has been a resurgence of interest in the role of extracranial-intracranial bypass surgery for the treatment of completely occluded ICA. With advances in the measurement of cerebral haemodynamics, it may be possible to identify high-risk patients who could benefit from the bypass surgery.

Cognitive dysfunction in 16 patients with carotid stenosis: detailed neuropsychological findings

Background

Impairment of cognitive function is often present in patients with carotid artery stenosis but the details of this dysfunction have rarely been reported. Our purpose was to elucidate the cognitive dysfunction in patients with unilateral severe carotid stenosis using comprehensive neuropsychological testing, and also to identify the specific underlying clinical and radiological factors.

Methods

We analyzed the results of neuropsychological testing, the clinical history, and MR findings in 16 consecutive patients with angiographically proven severe (70-99%) stenosis of the extra cranial internal carotid artery (ICA). Cognitive functions were examined using the Seoul Neuropsychological Screening Battery and the Neglect Battery. We excluded patients with cortical infarction and those with contra lateral ICA occlusion or severe stenosis.

Results

Our comprehensive neuropsychological testing revealed obvious cognitive deficits in all patients with unilateral severe ICA stenosis, the most common being frontal executive impairment. The mean cognitive score on the memory test was also significantly lower in patients with symptomatic ICA stenosis than in asymptomatic patients (29.33±10.98, mean±SD, p < 0.05). The total score on the global cognitive test was significantly lower in patients with an ischemic lesion on MRI than in no lesion patients (113.23±34.78, p < 0.05). The presence of symptoms related to the ICA stenosis was related to cognitive dysfunction even when there were no ischemic lesions on MRI. SPECT revealed ipsilateral cortical hypoperfusion in 9 of 12 patients (75%).

Conclusions

Cognitive deficits are common in patients with unilateral severe ICA stenosis. Our findings suggest that an additional mechanism beyond the structural lesion such as chronic hypoperfusion may affect cognitive function in patients with high-grade ICA stenosis.

Feasibility of Endovascular Recanalization for Symptomatic Cervical Internal Carotid Artery Occlusion

OBJECTIVES

This study sought to report technical details and clinical results of the first series of endovascular recanalization for cervical internal carotid artery (ICA) occlusion.

BACKGROUND

Cervical ICA occlusion is associated with impaired cerebral perfusion, which may lead to ischemic cerebral symptoms and hemodynamic infarcts. Neither surgical nor endovascular revascularization has been shown to benefit this population.

METHODS

Endovascular recanalization was attempted in 30 patients with ICA occlusions (27 men; age 72.1 +/- 8.0 years, range 48 to 85 years). Recurrent neurologic deficit or cerebral ischemia by perfusion study, after known ICA occlusion, was noted in all patients. Strategies and devices for coronary occlusion intervention were applied, including microcatheter-supported tapered-tip stiff coronary guidewires. Contralateral ICA stenosis was found in 9 patients (30%). All patients underwent independent neurologic and duplex ultrasound follow-up.

RESULTS

The overall technical success rate was 73% (22 of 30). No neck hematoma, intracranial hemorrhage, or hyperperfusion was noted. One (3.3%) fatal brainstem infarction occurred 1 day after a successful ICA procedure, with angiographically proven acute basilar artery occlusion and patent ICA stent. Baseline ophthalmic artery flow was reversed in 15 of the 22 successfully recanalized patients, and was normalized in 12 after the procedure. There was no new cerebral ischemic event or neurologic death for a mean follow-up of 16.1 +/- 18.5 months.

CONCLUSIONS

Endovascular recanalization for cervical ICA occlusion is feasible with acceptable midterm clinical results.

Selective neuronal damage and chronic hemodynamic cerebral ischemia

OBJECTIVE

In atherothrombotic internal carotid artery or middle cerebral artery (MCA) occlusive disease, chronic hemodynamic compromise may increase the risk for cerebral ischemic damage. To determine whether selective neuronal damage demonstrated as a decrease in central benzodiazepine receptor (BZR) in the normal-appearing cerebral cortex is associated with increased oxygen extraction fraction (OEF) (misery perfusion).

METHODS

We measured BZR and OEF using positron emission tomography in 105 nondisabled patients with atherothrombotic internal carotid artery or MCA occlusive disease and no cortical infarction. By using three-dimensional stereotactic surface projections and the stereotactic extraction estimation method, without correction for partial volume effects, the abnormally decreased BZR index [(the extent of the pixels with Z-score more than 2 compared with controls) x (average Z-score in those pixels)] in the cerebral cortex of the MCA distribution with arterial disease was calculated, and it was found to be correlated with the mean hemispheric value of OEF and several clinical variables.

RESULTS

All patients had pixels with abnormally decreased BZR, with the extent varying from 0.04 to 60.91%. Multivariate analysis showed that the abnormally decreased BZR index was positively correlated with the value of OEF and the history of stroke, whereas it was negatively correlated with the presence of hypercholesterolemia with statin treatment. Follow-up examinations of 17 patients without ischemic episode showed that a decrease of BZR was associated with an increase of OEF.

INTERPRETATION

In atherothrombotic internal carotid artery or MCA occlusive disease, misery perfusion may cause selective neuronal damage, and statins might have beneficial effects against neuronal damage.

Sténoses athéroscléreuses des artères carotides internes

Atherosclerotic carotid stenosis is a risk factor for stroke and other vascular events. Preventive medical treatment is based on the elimination of risk factors and the use of antithrombotic drugs. Surgery remains the standard revascularization treatment. The benefits of carotid surgery are especially important for severe (> or = 70%) symptomatic carotid stenosis. The benefits of surgery for moderate (> or =60%) asymptomatic stenosis or for moderate (50-69%) symptomatic stenosis are slight, particularly in women. The treatment decision requires consideration of individual factors to optimize the risk/benefit ratio.

Spect measurements of regional cerebral perfusion and carbondioxide reactivity: correlation with cerebral collaterals in internal carotid artery occlusive disease

BACKGROUND

The aim of the present study was to assess the regional variation in cerebral perfusion, vasomotor reactivity (VMR) and the role of cerebral collaterals in patients with symptomatic internal carotid artery (ICA).

METHODS

Seventeen functionally independent patients (60+/-9 years, mean+/-SD) with a unilateral symptomatic internal carotid artery occlusion and a <30% contralateral ICA stenosis were investigated. (99 m) Tc-hexamethyl propyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT) was performed to study cerebral blood flow in rest and during a CO(2) challenge in the cerebellum, temporal lobe, occipital lobe, basal ganglia, frontal lobe and parietal lobe. Time of flight and phase contrast MRA were used to study collateral flow via circle of Willis.

RESULTS

In rest, cerebral perfusion on the side ipsilateral to the ICA occlusion was decreased compared with the contralateral side in the basal ganglia (p<0.05), frontal lobe (p<0.01) and parietal lobe (p<0.01). During a CO(2) challenge only the ipsilateral frontal lobe demonstrated a perfusion decrease compared with the contralateral frontal lobe (p<0.05). Furthermore, in patients without collateral flow via the anterior circle of Willis the perfusion of the ipsilateral frontal lobe was significantly decreased (p<0.01) during the CO(2) challenge and crossed cerebellar diaschisis with a decreased perfusion on the contralateral cerebellar hemisphere was detected (p<0.05). No cerebral blood flow (CBF) differences were found for present/absent collateral flow via the posterior communicating artery.

CONCLUSION

Regional assessment of cerebral perfusion and VMR with SPECT demonstrated the heterogeneity of cerebral hemodynamics and the importance of collateral flow via the anterior circle of Willis.

Asymptomatic Carotid Artery Stenosis: Past, Present and Future

BACKGROUND

The role of carotid endarterectomy (CEA) for asymptomatic carotid artery stenosis (aCAS) remains a matter of debate. It seems that not only the degree of stenosis, but also other factors have to be taken in account to improve patient selection and increase the benefit of CEA for aCAS.

METHODS AND RESULTS

The literature pertaining aCAS was reviewed in order to describe the natural history, risk of stroke and benefit of CEA for patients with aCAS in regard to several factors.

CONCLUSION

The benefit of CEA for aCAS is low. Current factors influencing the indication for CEA are severity of stenosis, age, contralateral disease, stenosis progression to >80%, gender, concomitant operations and life expectancy. To improve patient selection investigations will concentrate on plaque characteristics and instability and cerebral hemodynamics and metabolism.

Cerebral hemodynamics after contralateral carotid endarterectomy in patients with symptomatic and asymptomatic carotid occlusion: a 10-year follow-up

We sought to investigate whether carotid endarterectomy (CEA) can achieve long-term cerebral hemodynamic improvement and reduce recurrence of cerebral ischemic events in symptomatic and asymptomatic patients with severe (>70%) carotid artery stenosis contralateral to carotid occlusion (CO). Thirty-nine patients with severe carotid lesion contralateral to CO were studied before (1 day) and after CEA (at 7 days, 1, 3 and 6 months, and then yearly thereafter). Collateral flow and cerebral vasomotor reactivity (VMR) were assessed by transcranial Doppler sonography (TCD). A total of 32 unoperated patients with severe carotid lesion contralateral to CO, who were comparable with respect to age and sex, served as a control group. The average period of TCD follow-up was 10 years and was obtained in all patients; during this period, major clinical events (stroke, acute myocardial infarction and death) were also recorded. The proportion of patients with collateral flow via the anterior communicating artery increased significantly from 61.5% before to 89.7% after CEA (P = 0.01). Cerebral VMR ipsilateral to CO improved in 85.7% of patients (30 of 35) within 30 days of CEA, and in all patients within 90 days. No significant spontaneous VMR recovery was recorded in the control group. After the initial recovery, no significant change in VMR was observed in the surgical group or the control group during the follow-up. In conclusion, in patients with severe carotid stenosis, CEA contralateral to symptomatic and asymptomatic CO determines a durable cerebral hemodynamic improvement not only on the side of the CEA but also on the contralateral side, with no difference between symptomatic and asymptomatic patients.

Magnetic resonance evaluation of the cerebral circulation in obstructive arterial disease

BACKGROUND

The aim of the current overview is to highlight the possibilities of magnetic resonance imaging (MRI) in the assessment of patients with obstructive arterial disease. The anatomic and hemodynamic aspects of the extra- and intracranial cerebral circulation were analyzed and show the importance of combining both aspects in studying cerebral hemodynamic changes.

RESULTS

Three levels of cerebral circulation are distinguished: blood flow to the brain (level 1); the distribution of blood flow in the brain (level 2), and finally perfusion of the brain (level 3). To investigate the anatomy of the arteries in the neck and the circle of Willis, contrast-enhanced, time-of-flight and phase contrast MR angiography (MRA) are available. To evaluate the hemodynamics at the 1st and 2nd level of the cerebral circulation two-dimensional phase contrast (volume flow and flow direction) MRA can be used. In addition, the distribution of blood via the circle of Willis can be visualized with dynamic MRA. At the 3rd level, measurements of regional brain perfusion can be obtained by injecting gadolinium, dynamic susceptibility contrast MRI, or noninvasively with arterial spin labeling (ASL) MRI. In addition, selective ASL MRI is able to evaluate the perfused territories of individual brain-feeding arteries.

CONCLUSION

The currently available MR techniques allow evaluation of the cerebral circulation from the aortic arch upwards towards the microvasculature and brain tissue perfusion in a comprehensive 20-min protocol. The combined use of the described MR methods in patients with steno-occlusive disease will further clarify the pathophysiological relations between the vasculature, perfusion and brain function.

Application of regional perfusion imaging to extra-intracranial bypass surgery and severe stenoses

Arterial Spin Labeling (ASL) is a non-invasive method to quantitatively measure perfusion without the need of contrast material. Measurement of perfusion is derived from the subtraction of two consecutively acquired scans, with or without radio frequency labeling of the magnetization in the feeding arteries. So far, almost all ASL methods only allowed labeling the entire feeding artery tree of the brain simultaneously, without separation of the individual perfusion territories. In this paper, we describe a newly developed method, Regional Perfusion Imaging, allowing quantitative measurement of perfusion in the watershed of individually labeled arteries (right and left internal carotids, as well as basilar artery and the posterior circulation). Unlike conventional digital subtraction angiography, this new method is completely non-invasive, and allows to selectively measure cerebral perfusion, and not only to get angiograms of the feeding vessels. Regional perfusion was already measured in more than 70 elderly healthy volunteers and over 30 patients with internal carotid disease (severe stenoses and/or after extra-intracranial bypass surgery). A large variation among perfusion territories, even in healthy volunteers, can be appreciated. This method has the potential to increase our understanding of the relationship between collateral flow and regional perfusion in patients with neurovascular diseases.

Cognitive functions in patients with cerebrovascular disease: potential impact of revascularization

The purpose of this review is to assess the impact of luminal restoring of carotid artery stenosis on cognitive functions. Therefore, papers dealing with the neuropsychological influence of carotid artery stenosis and studies comparing the neuropsychological course after respective recanalization have been included.

Revascularization of the posterior circulation

The primary objective of revascularization procedures in the posterior circulation is the prevention of vertebrobasilar ischemic stroke. Specific anatomical and neurophysiologic characteristics such as posterior communicating artery size affect the susceptibility to ischemia. Current indications for revascularization include symptomatic vertebrobasilar ischemia refractory to medical therapy and ischemia caused by parent vessel occlusion as treatment for complex aneurysms. Treatment options include endovascular angioplasty and stenting, surgical endarterectomy, arterial reimplantation, extracranial-to-intracranial anastomosis, and indirect bypasses. Pretreatment studies including cerebral blood flow measurements with assessment of hemodynamic reserve can affect treatment decisions. Careful blood pressure regulation, neurophysiologic monitoring, and neuroprotective measures such as mild brain hypothermia can help minimize the risks of intervention. Microscope, microinstruments and intraoperative Doppler are routinely used. The superficial temporal artery, occipital artery, and external carotid artery can be used to augment blood flow to the superior cerebellar artery, posterior cerebral artery, posterior inferior cerebellar artery, or anterior inferior cerebellar artery. Interposition venous or arterial grafts can be used to increase length. Several published series report improvement or relief of symptoms in 60 to 100% of patients with a reduction of risk of future stroke and low complication rates.

Long-term reendothelialization of excimer laser—assisted nonocclusive anastomoses compared with conventionally sutured anastomoses in pigs

Object. In contrast to conventional anastomosis methods, the excimer laser—assisted nonocclusive anastomosis (ELANA) technique involves a platinum ring and intima—adventitia apposition with a rim of medial and adventitial layers exposed to the bloodstream. The authors assessed the reendothelialization of porcine carotid arteries through ELANA compared with conventional anastomosis by using scanning electron microscopy.

Methods. In 28 pigs a bypass with one ELANA and one conventional anastomosis was made on the left common carotid artery. All patent anastomoses were evaluated intraoperatively with the aid of an ultrasonographic flowmeter and postoperatively by using scanning electron microscopy at 2 weeks, 2 months, 3 months, and 6 months thereafter. Twenty-four of 28 bypasses (48 of 56 end-to-side anastomoses) were fully patent at the time of evaluation. On scanning electron microscopic evaluation of the bypasses, all 48 patent anastomoses showed complete reendothelialization, including all 24 ELANAs in which the endothelium covered the rim and the laser-ablated edge completely. No endothelial difference was observed between conventional anastomoses and ELANAs, aside from the obvious anatomical differences like the platinum ring, which had been completely covered with endothelium. At 6 months postsurgery, remodeling of the ELANA was observed, leaving the ring covered with a layer of endothelium as the most narrow part of the anastomosis.

Conclusions. In long-term experiments, ELANA allows reendothelialization comparable to that achieved with conventional anastomosis. Considering its nonocclusive and high-flow characteristics, the ELANA technique is preferable in cerebral revascularization procedures.

Critical analysis of hemodynamic insufficiency by head-up tilt in patients with carotid occlusive disease

BACKGROUND

The objective of this study was to evaluate the diagnostic value of the head-up-tilt (HUT) test for detecting cerebral hemodynamic insufficiency in patients with major cerebral artery occlusion disease because such patients may benefit from extracranial - intracranial bypass surgery.

METHODS AND RESULTS

In 13 cases of transient ischemic attacks in patients with carotid or middle cerebral artery occlusive disease, the HUT test was used to determine whether or not the symptoms appear during induced hypotension before investigating cerebral hemodynamics with positron emission tomography. Three of the 13 patients showed focal symptoms such as hemiparesis and limb shaking during the HUT test. In all 3 patients, the oxygen extraction fraction (OEF) increased beyond 53.3% (ie, misery perfusion), whereas only 2 of the other 10 patients without focal symptoms showed an increase in OEF during HUT.

CONCLUSIONS

The HUT test was highly useful for screening patients with cerebral hemodynamic insufficiency in carotid occlusive disease.

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.

Positron Emission Tomography Imaging of Cerebral Ischemia

Positron emission tomography (PET) uniquely allows the in vivo regional measurement of several important physiologic parameters in living humans, including cerebral blood flow and oxygen metabolism. PET studies have advanced our understanding of normal human brain physiology and, as detailed in this article, our understanding of human cerebrovascular pathophysiology. This article focuses on knowledge gained from PET regarding acute ischemic stroke and chronic oligemia from arterial occlusive disease. Knowledge of the responses of the brain and its vasculature to ischemia and oligemia is growing more important with the increasing availability of CT and MR perfusion techniques.

Indications for cerebral revascularization for patients with atherosclerotic carotid occlusion

Patients with complete carotid occlusion and recent ischemic symptoms are at high risk for subsequent stroke, particularly those with evidence of severe hemodynamic impairment due to poor collateral flow. Treatment options for these patients include direct extracranial to intracranial arterial bypass, or interventions aimed at improving collateral sources of flow such as endarterectomy or angioplasty and stenting of the ipsilateral external carotid artery, the contralateral carotid artery, or the vertebral arteries. The evidence supporting the use of these procedures for patients with complete occlusion of the carotid artery will be the focus of this article. The use of physiologic imaging to select subgroups of patients at high risk due to hemodynamic factors will also be discussed.

Acute Carotid Artery Thrombosis: Description of 12 Surgically Treated Cases

The morbidity and mortality of stroke secondary to acute internal carotid artery thrombosis range from 40 to 69% and from 15 to 55%, respectively, after purely medical treatment. This report describes a series of 12 patients who underwent urgent surgical treatment for primary acute carotid artery thrombosis between January 1999 and December 2002. Upon admission, all patients had severe neurologic deficits contralateral to carotid artery thrombosis. One patient experienced ongoing changes in the level of consciousness. The interval between the onset of symptoms and admission was less than 6 hr in all cases. Initial work-up in all patients included a brain computed tomographic scan with contrast injection and carotid duplex scan. The operative procedure consisted of carotid thomboemdarterectomy after shunt placement with prosthetic patch closure. Intraoperative angiography was performed in all cases. Following treatment, we observed deterioration of neurologic status leading to death in one case; improvement with partial regression of initial neurologic deficit in two cases, including one patient who died from causes unrelated to carotid artery disease; and full neurologic recovery in nine cases. The delay to revascularization was longer than 6 hr in both patients who died. These data support surgical intervention for carotid artery thrombosis in selected patients without major disturbances of consciousness or hemorrhagic infarction, provided that the delay to revascularization is less than 6 hr.

Mapping hypercapnia-induced cerebrovascular reactivity using BOLD MRI

Severe carotid artery stenosis or occlusion may put patients at risk for ischaemic stroke. Reduced cerebrovascular reserve capacity is a possible indicator of an imminent ischaemic event and can be determined by assessment of cerebrovascular reactivity to a vasodilative stimulus. However, little is known about the distribution of cerebrovascular reactivity in healthy individuals. In 13 healthy volunteers, dynamic T2* MR images, acquired at alternating inspiratory pCO2 levels, showed a high percentage of signal change in grey matter, with a strong linear correlation with end-tidal pCO2. The mean percentages of signal change for grey and white matter were 5.9 +/- 1.2% and 1.9 +/- 0.5%, respectively. The mean time lag between CO2 stimulus and haemodynamic response was 15 +/- 4 s for grey matter and 180 +/- 12 s for white matter. Parameter mapping revealed a hemispherically symmetrical and homogeneous distribution of cerebrovascular reactivity over the entire grey matter. These findings indicate that it may be feasible to detect exhausted cerebrovascular autoregulation in patients with a compromised cerebral vasculature.

Pattern of collaterals, type of infarcts, and haemodynamic impairment in carotid artery occlusion

BACKGROUND

In internal carotid artery (ICA) occlusion, increased oxygen extraction fraction (OEF) indicates inadequate collateral blood flow distal to the occlusion, which may be caused by poor function of collateral pathways. In ICA occlusion, the circle of Willis may be the major collateral pathway, while the collaterals through the ophthalmic artery and leptomeningeal vessels may be recruited when collateral flow through the circle of Willis is inadequate. Conversely, ischaemic lesions may affect the adequacy of collateral blood flow by reducing the metabolic demand of the brain.

OBJECTIVE

To determine whether the pattern of collateral pathways and the type of infarcts are independent predictors of OEF in ICA occlusion.

METHODS

We studied 42 patients with symptomatic ICA occlusion. The presence of Willisian, ophthalmic, or leptomeningeal collaterals was evaluated by conventional four vessel angiography. The infarcts on magnetic resonance imaging were categorised as territorial, border zone (external or internal), striatocapsular, lacunar, and other white matter infarcts. The value of OEF in the affected hemisphere was measured with positron emission tomography as an index of haemodynamic impairment.

RESULTS

Using multivariate analysis, the presence of any ophthalmic or leptomeningeal collaterals and the absence of striatocapsular infarcts were significant and independent predictors of increased OEF.

CONCLUSIONS

In patients with symptomatic ICA occlusion, the supply of collateral flow, which is affected by the pattern of collateral pathways, and the metabolic demand of the brain, which is affected by the type of infarct, may be important factors determining the severity of haemodynamic impairment.

The use of positron emission tomography in cerebrovascular disease

Even with rapid development of other neuroimaging modalities such as MR imaging and CT, PET is the only technique that provides accurate, quantitative measurements of regional hemodynamics and metabolism in human subjects. Through the use of these combined measurements, we have greatly expanded our knowledge of the pathophysiology of cerebrovascular disease of different types. It has been possible to document the compensatory responses of the brain to reductions in perfusion pressure and to directly relate these responses to prognosis. PET measurements of OEF identify a subgroup of patients who have carotid occlusion and who are at increased risk for recurrent stroke who cannot be identified by any other clinical or arteriographic means. These measurements of OEF are being used to identify high-risk patients for inclusion in a clinical trial to assess the efficacy of surgical revascularization in reducing the subsequence of ipsilateral ischemic stroke. In acute ischemic stroke, attempts have been made to define the "ischemic penumbra" and to predict tissue viability and clinical outcome, although the reliability of PET markers of ischemia in distinguishing viable from irreversibly damaged tissue needs to be confirmed with independent data sets. Much work has been devoted to the investigation of the metabolic effects of infarcts and hemorrhages on remote areas of the brain; the clinical importance of such findings appears to be minimal. Early studies of recovery from stroke suggested functional reorganization of the brain, but further investigations with more rigorous experimental design need to be performed. Given the case of performing such studies with functional MR imaging, it is likely that this technology will supplant PET for this specific indication. The importance of ischemia as a secondary mechanism of brain injury has been addressed in ICH and SAH. PET demonstrated that hematomas exert a primary depression of metabolism rather than inducing ischemia in the surrounding tissue. It also documented the integrity of autoregulation and provided clinically useful information regarding the safety of blood pressure reduction after ICH. Studies in SAH have differentiated the primary effects of the hemorrhage on cerebral hemodynamics and metabolism from those of vasospasm. PET studies are time-consuming, expensive, and require extensive facilities and technical support. In the field of cerebrovascular disease, PET has served as a specialized research tool at a few centers to help elucidate the pathophysiology of stroke. Up until now, however, PET scans in individual patients have not been demonstrated to be necessary for making patient care decisions. Whether the role of PET expands to impact the management of individual patients will depend on the results of investigations like the Carotid Occlusion Surgery Study that directly assess the ability of PET to influence patient outcome.

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.