Prognosis of asymptomatic carotid occlusion

Magnetic resonance markers of bilateral neuronal metabolic dysfunction in patients with unilateral internal carotid artery occlusion

OBJECTIVES

To evaluate cerebral hemodynamic, metabolic and anatomic changes occurring in patients with unilateral occlusion of the internal carotid artery (ICA).

MATERIALS AND METHODS

Twenty-two patients with unilateral occlusion of ICA and twenty age and sex matched healthy subjects were included in the study. Single voxel proton magnetic resonance spectroscopy (¹H-MRS) of the centrum semiovale, semi-automated hippocampal volumetry in T1-weighted scans and transcranial Doppler examination (TCD) with calculation of Breath Holding Index (BHI) were performed in both groups. Metabolic, anatomic, and hemodynamic features were compared between the two groups.

RESULTS

The N-acetylaspartate (NAA)/choline (Cho) ratio was significantly lower in both hemispheres of enrolled patients compared to controls (p = 0.005 for the side with occlusion, p = 0.04 for the side without occlusion). The hippocampus volume was significantly reduced bilaterally in patients compared to healthy subjects (p = 0.049). A statistically significant difference in BHI values was observed between the side with occlusion and without occlusion (p = 0.037) of the patients, as well as between BHI values of the side with occlusion and healthy volunteers (p = 0.014).

DISCUSSION

Patients with unilateral ICA occlusion have reduced NAA/Cho ratio in the white matter of both hemispheres and have bilateral atrophy of hippocampus. The alteration of hemodynamics alone cannot explain these changes.

Prognosis of Asymptomatic Carotid Artery Occlusion

Background and Purpose—

The aim of this systematic review was to quantify the risk of ipsilateral stroke in patients with asymptomatic carotid artery occlusion (ACAO).

Methods—

Studies reporting ipsilateral stroke risk in ACAO were identified by a search of MEDLINE, EMBASE, and study bibliographies. Study estimates were pooled using a random effects model, and heterogeneity was quantified using the I 2 statistic. The primary outcome was the annual rate of ipsilateral stroke.

Results—

Thirteen studies were identified, encompassing 718 patients with ACAO who were followed up for a median of 2.8 years. The annual rate of ipsilateral stroke was 1.3% (95% confidence interval, 0.4–2.1; I 2 =53%). The annual rate of ipsilateral transient ischemic attack was 1.0% (95% confidence interval, 0.3–1.8; I 2 =40%). The annual rate of death was substantially higher at 7.7% (95% confidence interval, 4.3–11.2; I 2 =83%). Correction for possible publication bias for the primary outcome suggested a lower risk of ipsilateral stroke (0.3% per year; 95% confidence interval, –0.4 to 1.1).

Conclusions—

Stroke in ACAO is relatively infrequent, but patients face high mortality rates. This suggests the need for intensified medical therapy in ACAO.

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.

MMP-9 microsatellite polymorphism: Association with the progression of intima-media thickening and constrictive remodeling of carotid atherosclerotic plaques

Intima-media thickening (IMT) of carotid arteries and constrictive remodeling (CR) of atherosclerotic plaques are vascular pathologic characteristics that precede the onset of vascular events. SMC migration and proliferation are linked both to IMT and CR and are matrix metalloproteinase 9 (MMP-9) dependent. A genetic polymorphism (PM) of MMP-9, a CA (13-27) microsatellite in the promoter region, which accounts for differential expression of MMP-9, could be linked to progression of IMT and CR. Progression of IMT and CR of plaques in carotid arteries were studied in 55 consecutive patients with a 12-18 months follow-up. All patients were genotyped for MMP-9 PM. A positive linear relationship between the number of repeats and the progression of IMT (P=0.028) as well as of CR (P=0.018) was found. The analogous relationship was obtained when only the allele with longer microsatellite was considered. Carriers of more than 20 repeats in one allele showed faster both IMT growth (P=0.045) and stenosis progressions of plaques (P=0.019). In multivariate analysis, age, dyslipidemia, and MMP-9 PM were determinants of IMT progression, while MMP-9 PM was the only one of CR. In conclusion, the high number of CA repeats in MMP-9 promoter is positively correlated with faster IMT and CR progression.

Assessment of cerebral haemodynamics and vascular reserve in patients with symptomatic carotid artery occlusion: an integrated MR method

We describe an MR-based methodology designed to study cerebral haemodynamic compromise in patients with symptomatic carotid occlusions. We present the results of eight patients who underwent MR angiography of the cervical carotids and circle of Willis, MR imaging of the brain and dynamic gadolinium MR perfusion studies before and after the injection of the carbonic anhydrase inhibitor acetazolamide. All patients showed increased transit times in the symptomatic hemisphere at rest indicating reduced flow. The transit time asymmetries became more pronounced after acetazolamide in all patients because of failed vasodilatation on the affected side. There was an inverse correlation between the degree of increased transit time and the degree of collateralisation around the circle of Willis. We believe that demonstration of both macroscopic vascular anatomy and microvascular reserve is important when assessing patients with possible low-flow states and the described method is a robust means of obtaining that data.

[Early detection of asymptomatic carotid disease in patients with obliterative arteriosclerosis of the lower extremities]

INTRODUCTION

Arterial occlusive disease is a systemic phenomenon frequently coexisting in more than one arterial system. Often in one arterial bed disease is manifested with symptoms, in another is asymptomatic. There are only several reports indicating the prevalence of carotid stenosis in patients with peripheral vascular disease. Asymptomatic carotid stenosis is defined as the presence of internal carotid/carotid bifurcation stenotic or occlusive lesions in patients with no signs or symptoms of cerebrovascular disease. Lesions are important causative factors in unheralded stroke. Two factors are particularly important: severity of stenosis and morphologic characteristics of the stenotic plaque. The recent largest completed clinical trial concerning asymptomatic carotid artery stenosis (completed 1995) ACAS (Asymptomatic Carotid Artery Study) established the benefit of surgical treatment vs. best medical treatment. The reduction in relative risk of stroke was 55% in favor of surgery. Population screening for carotid stenosis is inefficient and expensive. The current interest is focused on the efficacy of screening population at risk.

AIM OF THE STUDY

The aim of the study was to establish prevalence of asymptomatic carotid artery stenosis in patients with symptomatic lower extremities atherosclerosis. Furthermore, possibility for limiting screening to subgroups of patients concerning risk factors, carotid bruit and severity of lower extremities atherosclerosis, was examined.

PATIENTS AND METHODS

Over the study period 109 patients with symptomatic lower extremities atherosclerosis underwent routine carotid duplex examinations (on Acuson 128 XP-10) to detect the presence of asymptomatic carotid disease. Indication for hospitalization was pain at rest in 60% of patients, ulcer or gangrene in 25% and claudication in 15%. Patients with a history of previous carotid endarterectomy or symptomatic cerebrovascular disease, patients who underwent emergency operations, and patients with nonatherosclerotic disease were not included in the analysis. Internal carotid stenosis was determined by duplex ultrasound blood flow velocities according to a criterion of ACAS. Plaque morphology was classified according to Gray-Weale as type I (echolucent) to type IV (echogenic). Plaque surface was graded as smooth, irregular and ulcerated. Secondary analysis was performed to find out a subgroup of patients with symptomatic lower extremities atherosclerosis at significant risk for carotid artery stenosis in order to be maximally effective. We examined the relationship of carotid artery stenosis of 60% or grater or occlusion to the 1st degree of lower extremities atherosclerosis (determined by previous vascular surgery, preoperative ankle-systolic blood pressure index, clinical severity of disease); 2. age and gender; 3. risk factors of atherosclerosis (arterial hypertension, diabetes mellitus, hyperlipidaemia, smoking history, and alcohol consumption); and 4. carotid bruit. Data were analyzed using two-way contingency tables and chi 2 test, two-sample Student's test, and multivariate, stepwise logistic regression analysis.

RESULTS AND DISCUSSION

According to the criterion of ACAS, forty patients (36.69%) had haemodynamically significant carotid artery stenosis > 60% or occlusion, and 32 patients (29%) carotid artery stenosis > 70% or occlusion. These results confirm that patients with symptomatic lower extremities atherosclerosis are at risk for increased prevalence for simultaneous asymptomatic carotid artery stenosis. Using B-mode we assessed carotid plaque characteristics in a group of 40 patients with asymptomatic 50-99% carotid artery stenosis. Distribution of plaque morphology was as follows: type I (echolucent with thin echogenic cap) in 4 patients (9.30%), type II (substantially echolucent) in 10 (23.26%), type III (dominantly echogenic) in 19 (44.18%), and type IV (homogenous echogenic) in 10 patients (23.26%). Plaque types III and IV were more common in asymptomatic patients, but there was no significant association with fibrous component of plaque. Degree of internal carotid stenosis was unrelated to plaque morphology. Plaque surface was as follows: smooth in 8 patients (18.60%), irregular in 25 (58.14%) and ulcerated in 10 patients (23.26%). Presence of ulcerated surface in 6 plaques (14%) with 50-69% of carotid artery stenosis is worth mentioning because these patients could be a subgroup likely to suffer stroke without warning. Secondary analysis examined the relationship of carotid artery stenosis of 60% or grater or occlusion to different patient's characteristics. By multivariant analysis we found that significant carotid artery stenosis was associated with prior vascular surgery, in patients over 60 years of age, arterial hypertension, ASPI < 0.5, and carotid bruit (results were considered significant if p < 0.05). Probability that various factors influenced the prevalence of carotid artery stenosis was assessed by multivariate stepwise logistic regression analysis. Only carotid bruit was associated with carotid artery stenosis > 60% (t = 0.50; p = 0.01), with sensitivity of 67% and specificity of 56%.

CONCLUSION

Prevalence of asymptomatic carotid artery stenosis in patients with lower extremities atherosclerosis is relatively high. Limiting screening of specific subgroups for any demographic or medical characteristics is ineffective. Screening for asymptomatic carotid artery stenosis is indicated in all patients with lower extremities atherosclerosis except in whom prophylactic carotid endarterectomy is not recommended because of comorbid disease or extreme age.

The fate of a patent carotid artery contralateral to an occlusion

The finding of carotid stenosis contralateral to a carotid occlusion is becoming more frequent. While the neurologic outcomes in this patient population have been described, the rate of disease progression measured by duplex examination and the eventual need for carotid endarterectomy has not been described. In this study, a computerized database of carotid duplex examinations was reviewed and clinical data were obtained from clinic records. From 9124 studies 117 patients were identified. Thirty patients had previous carotid surgery on the patent side and were excluded. Of 87 patients 33 required carotid endarterectomy on the patent side. The rate of disease progression and/or the performance of a carotid endarterectomy by life-table analysis was 85.9% over 8 years. There were 10 neurologic events during the follow-up period. Patients with carotid stenosis and contralateral occlusion are at significant risk for disease progression. Follow-up should be more frequent and of longer duration in this patient population. A significant number of patients with carotid artery occlusion will require a carotid endarterectomy of the patent contralateral carotid.

Endarterectomy of an Occluded ICA: Short Segment Occlusion with Distal Patency Maintained by an Aberrant Ascending Pharyngeal Artery

SUMMARY

The authors report a case in which an anomalous ascending pharyngeal artery maintained patency of the internal carotid artery beyond an occlusion. The patient presented with ipsilateral transient ischaemic attacks and was found to have an internal carotid artery occlusion on Doppler ultrasound. Subsequent angiography demonstrated retrograde flow in the ipsilateral APA, perfused by pharyngeal anastomoses from the contralateral APA with slow antegrade flow in the ipsilateral ICA distal to the occlusion. Carotid endarterectomy resulted in abolition of the TIA's.

Death from ischemic stroke in the anterior circulation: the contralateral carotid matters

Death from acute hemispheric infarction is commonly associated with stroke size, but the potential role of the internal carotid artery (ICA) in this phenomenon is poorly understood. The aim of the present study was to analyse the relation between the degree of ipsilateral and contralateral ICA stenosis, infarct type and death. We studied 2,148 first-ever stroke patients with anterior circulation infarction from the Lausanne Stroke Registry. Doppler ultrasonography with frequency spectral analysis and Duplex-scanning were performed systematically during the acute phase of stroke. The patients were divided into groups according to the degree of ipsilateral and contralateral ICA stenosis. The case fatality ratios (CFR) at hospital discharge were obtained for each group. Several clinical features including age, stroke topography, level of consciousness, limb weakness on admission, type of onset, hyperglycemia, previous transient ischemic attack, cardiac ischemia, cardiac arrhythmia and left ventricular hypertrophy were also studied. Mortality increased significantly with ipsilateral ICA stenosis: </=50% stenosis, 2.8%, (44/1,549); >50% and </=90% stenosis, 3.5%, (6/170); >90% stenosis, 5.6%, (24/429); p = 0.026, but not significantly with contralateral ICA stenosis. However, patients without ipsilateral ICA stenosis had significantly higher mortality when contralateral stenosis was present: 16.7% (3/18) versus 2.7% (41/1,531), p = 0.013. This corresponded to an increased frequency of strokes involving the whole middle cerebral artery territory, with impaired consciousness at onset of stroke. Patients with ipsilateral stenosis had similar CFR independently of the presence or absence of contralateral stenosis. In conclusion, patency of the contralateral ICA may be an important contributory factor of larger infarction and indirectly of stroke mortality in patients with no ipsilateral stenosis.

Cerebrovascular disorders in patients with diabetes mellitus

Diabetes mellitus is a risk factor for ischemic, but not hemorrhagic stroke. The frequency of transient ischemic attacks is not increased in patients with diabetes compared to the general population. Diabetes mellitus is associated with higher mortality, worse functional outcome, more severe disability after stroke and a higher frequency of recurrent stroke. Diabetes is not associated with an increased size of cerebral infarction. Controversy exists regarding whether hyperglycemia adversely affects stroke outcome or primarily reflects stroke severity. Cerebral blood flow disturbances, impaired cerebrovascular reactivity, and damage to large and small extra- and intracranial cerebral vessels have been found in humans and animals with diabetes. Combinations of some or all of these factors may underlie the high incidence and worse outcome of stroke in patients with diabetes. Knowledge of these pathophysiologic factors will assist in the design of future intervention strategies.

The anatomy of the posterior communicating artery as a risk factor for ischemic cerebral infarction

BACKGROUND

After the occlusion of an internal carotid artery the principal source of collateral flow is through the arteries of the circle of Willis, but the size and patency of these arteries are quite variable. Study of the anatomy of the collateral pathways in patients with internal-carotid-artery occlusion with or without infarction in the watershed area of the deep white matter may identify patterns that afford protection from ischemic infarction.

METHODS

Using conventional magnetic resonance imaging and three-dimensional phase-contrast magnetic resonance angiography, we evaluated 29 consecutive patients (32 hemispheres at risk) with angiographically proved occlusion of the internal carotid artery. Four collateral pathways to the occluded vessel were evaluated: the proximal segment of the anterior cerebral artery, the posterior communicating artery, the ophthalmic artery, and leptomeningeal collateral vessels from the posterior cerebral artery.

RESULTS

Only features of the ipsilateral posterior communicating artery were related to the risk of watershed infarction. The presence of posterior communicating arteries measuring at least 1 mm in diameter was associated with the absence of watershed infarction (13 hemispheres, no infarcts; P < 0.001). Conversely, there were 4 watershed infarcts in the 6 hemispheres with posterior communicating arteries measuring less than 1 mm in diameter and 10 infarcts in the 13 hemispheres with no detectable flow in the ipsilateral posterior communicating artery.

CONCLUSIONS

A small (< 1 mm in diameter) or absent ipsilateral posterior communicating artery is a risk factor for ischemic cerebral infarction in patients with internal-carotid-artery occlusion.

Natural history of patients with chronic occlusion of the internal carotid artery

Although 3% of the elderly population may have asymptomatic unilateral internal carotid artery occlusion (ICAO), between 10% and 20% of patients with initial stroke in the carotid territory have appropriate ipsilateral extracranial ICAO. In the latter instance, it is often difficult to establish whether ICAO is (a) an acute thrombotic process on an underlying atheromatous stenosis; (b) an acute embolic ICAO (from heart or aorta); or (c) an old ICAO that was previously asymptomatic. Intracranial studies show that the first stroke ipsilateral to ICAO is usually associated with occlusions distal to ICAO, which suggest artery-to-artery embolism. On the other hand, the follow-up of stroke patients with ICAO shows that delayed cerebral infarction distal to the established ICAO often involves watershed areas and may correspond to hemodynamic disturbances. Because the international extracranial/intracranial arterial bypass study did not show any surgical benefit, current management is mainly directed to stabilization of associated causes of hemodynamic failure (hypotension, bradycardia, etc.). Attempts to find subgroups that may benefit from bypass surgery are still ongoing. However, the prognosis of these patients is negatively influenced by a particularly high risk of cardiac death.

Caudate hemorrhage with moyamoya-like vasculopathy from atherosclerotic disease

BACKGROUND AND PURPOSE

Caudate hemorrhage usually results from hypertension, rupture of arteriovenous malformation or aneurysm, or rarely, moyamoya disease. Moyamoya-like changes related to severe atherosclerotic occlusive disease, usually causing ischemic stroke, have been reported.

CASE DESCRIPTION

A 51-year-old normotensive patient was admitted with headache due to a left caudate hematoma with ventricular extension. There was a history of smoking, leg claudication, elevated cholesterol, and coronary artery disease. Angiography demonstrated complete extracranial carotid occlusion on the left and atherosclerotic stenosis at the bifurcation on the right, with supraophthalmic occlusion distally. At the base of the brain, bilateral moyamoya-like vessels, presumed to be secondary to atherosclerotic occlusion, were evident, but neither aneurysm nor arteriovenous malformation was present. Cerebral blood flow and transcranial Doppler studies indicated severely impaired cerebral perfusion that improved after bilateral extracranial-to-intracranial bypass surgery.

CONCLUSIONS

Atherosclerotic occlusive carotid disease with moyamoya-like changes may be a rare cause of caudate hemorrhage. A decrease in moyamoya vessels with bypass surgery may reduce the risk of recurrent hemorrhage.