You are in: eMedicine Specialties > Neurology > Neuro-vascular Diseases Anterior Circulation StrokeArticle Last Updated: Jan 3, 2006AUTHOR AND EDITOR INFORMATIONAuthor: Alison Baird, MD, PhD, National Institute of Neurological Disorders and Stroke, Chief, Stroke Neuroscience Unit, National Institutes of Health Alison Baird is a member of the following medical societies: American Academy of Neurology and American Heart Association Editors: Draga Jichici, HBSc, MD, FRCP(C), FAHA, Assistant Professor, Department of Medicine, Division of Critical Care Medicine, McMaster University Medical School, Canada; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Howard S Kirshner, MD, Professor of Neurology, Psychiatry and Hearing and Speech Sciences, Vice Chairman, Department of Neurology, Vanderbilt University School of Medicine; Director, Vanderbilt Stroke Center; Program Director, Stroke Service, Vanderbilt Stallworth Rehabilitation Hospital; Consulting Staff, Department of Neurology, Nashville Veterans Affairs Medical Center; Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital; Helmi L Lutsep, MD, Associate Professor, Department of Neurology, Oregon Health and Science University; Associate Director, Oregon Stroke Center Author and Editor Disclosure Synonyms and related keywords: carotid artery territory ischemic stroke, major hemispheric syndrome, middle cerebral artery stroke, MCA stroke, MCA syndrome, anterior cerebral artery stroke, ACA stroke, lacunar stroke, reperfusion, anterior circulation stroke INTRODUCTIONBackgroundThe anterior circulation of the brain describes the areas of the brain supplied by the right and left internal carotid arteries and their branches. The internal carotid arteries supply the majority of both cerebral hemispheres, except the occipital and medial temporal lobes, which are supplied from the posterior circulation (see Image 1). Ischemic strokes occurring in the anterior circulation are the most common of all ischemic strokes, accounting for approximately 70% of all cases. The internal carotid artery originates at the bifurcation of the common carotid artery at the level of the thyroid cartilage in the neck. The extracranial portion of the artery passes into the carotid canal of the temporal bone without giving off any branches. The intracranial portion of the artery consists of the petrosal, cavernous (ie, S-shaped carotid syphon), and supraclinoid portions. The major intracranial branches arise from the supraclinoid portion, the first being the ophthalmic artery that enters the orbit through the optic foramen to supply the retina and optic nerve. Next, the posterior communicating artery arises just distal to the ophthalmic artery and joins the posterior cerebral artery. The anterior choroidal artery arises prior to the terminal bifurcation of the internal carotid artery into the middle cerebral and anterior cerebral arteries. The middle cerebral artery (MCA) is the direct continuation of the artery, while the anterior cerebral artery (ACA) branches medially at the level of the anterior clinoid process. The circle of Willis consists of a vascular communication of blood vessels at the base of the brain connecting the anterior and posterior circulations. The vessels of the anterior circulation are connected via the posterior communicating arteries to the posterior circulation. A high degree of variation exists in the normal vascular anatomy. For example, in as many as 20% of patients, the posterior cerebral arteries (ie, fetal) arise from the internal carotid artery as normal vascular variants. Therefore, some variation exists in the exact parts of the brain supplied by the anterior circulation. For additional resources, visit Stroke/Cerebrovascular Disease. PathophysiologyIschemic strokes in the anterior circulation are caused most commonly by occlusion of one of the major intracranial arteries or of the small single perforator (penetrator) arteries. The most common causes of arterial occlusion involving the major cerebral arteries are (1) emboli, most commonly arising from atherosclerotic arterial narrowing at the bifurcation of the common carotid artery, from cardiac sources, or from atheroma in the aortic arch and (2) a combination of atherosclerotic stenosis and superimposed thrombosis. Lacunar strokes are believed to be caused by lipohyalinotic intrinsic disease of the small penetrating vessels. The most common sites of occlusion of the internal carotid artery are the proximal 2 cm of the origin of the artery and, intracranially, the carotid siphon. Factors that modify the extent of infarction include the speed of occlusion and systemic blood pressure. Occlusion of the internal carotid artery is not infrequently silent, because external orbital-internal carotid and willisian collaterals can open up if the occlusion has occurred gradually over a period of time. Mechanisms of ischemia resulting from internal carotid artery occlusion are, most commonly, artery-to-artery embolism or propagating thrombus and perfusion failure from distal insufficiency. The MCA is the largest of the intracerebral vessels and supplies through its pial branches almost the entire convex surface of the brain, including the lateral frontal, parietal, and temporal lobes; insula; claustrum; and extreme capsule. The lenticulostriate branches of the MCA supply the basal ganglia, including the caput nuclei caudati, the putamen, the lateral parts of the internal and external capsules, and sometimes the extreme capsule. Occlusion of the MCA commonly occurs in either the main stem (M1) or in one of the terminal superior and inferior divisions (M2). Occlusion of the M1 segment of the MCA prior to the origin of the lenticulostriate arteries in the presence of a good collateral circulation can give rise to the large striatocapsular infarct. Occlusion of the MCA or its branches is the most common type of anterior circulation infarct, accounting for approximately 90% of infarcts and two thirds of all first strokes. Of MCA territory infarcts, 33% involve the deep MCA territory, 10% involve superficial and deep MCA territories, and over 50% involve the superficial MCA territory. The ACA supplies the whole of the medial surfaces of the frontal and parietal lobes, the anterior four fifths of the corpus callosum, the frontobasal cerebral cortex, the anterior diencephalon, and the deep structures. Occlusion of the ACA is uncommon, occurring in only 2% of cases, often through atheromatous deposits in the proximal segment of the ACA. The anterior choroidal artery supplies the lateral thalamus and posterior limb of the internal capsule. Occlusion of the anterior choroidal artery occurs in fewer than 1% of anterior circulation strokes. Often, ischemia in the distribution of the ophthalmic artery is transient in the setting of symptomatic internal carotid artery occlusion (ie, transient monocular blindness, occurring in approximately 25% of patients), but central retinal artery ischemia is relatively uncommon, presumably because of the efficient collateral supply. Occlusion of single penetrating branches of the middle and anterior cerebral arteries that supply the deep white and gray matter produce the lacunar type of stroke. These occlusions account for as many as 20% of ischemic strokes. The acute ischemic process varies markedly from patient to patient. Patients with similar clinical syndromes may have markedly different pathophysiological profiles. Many new pathophysiological insights have been obtained from studies using functional brain imaging (eg, magnetic resonance imaging [MRI], positron emission tomography [PET], single-photon emission computed tomography [SPECT]). Several pathophysiological ischemic stroke syndromes can be identified on the basis of imaging parameters of perfusion and tissue injury that could be used to target stroke treatment. Using new MRI methods, the following 3 patterns have been identified:
Efforts are now underway to incorporate MR angiography findings as well. Reperfusion is an important part of the ischemic process, and by 24 hours, 20-40% of arterial occlusions have begun to clear, with recanalization rates of 70% by 1 week and 90% by 3 weeks. Early reperfusion (<24 h) may have significant prognostic benefits and is associated with improved outcome and smaller infarct size, but later reperfusion may not alter outcome significantly and may be associated with hemorrhagic conversion of the infarct and edema formation. FrequencyUnited StatesIn a recent study, Broderick et al estimated that approximately 731,000 new and recurrent cases of stroke occur each year in the United States. Approximately 80% of these are ischemic strokes. Anterior circulation ischemic stroke accounts for approximately 70% of all ischemic strokes. Approximately 409,360 new cases of anterior circulation ischemic stroke per year are reported in the United States. InternationalThe risk of stroke is highest in Eastern Europe, followed by Western Europe, Asia, the rest of Europe, and North America. Mortality/Morbidity
RaceThe patterns of arterial occlusion are different in African Americans and Asians than in Caucasians.
SexStrokes at all ages are more likely to occur in men, but overall more strokes occur in women. This is because strokes occur more commonly at older ages and females have a longer life span than males (the native protective effect of estrogen is lost at menopause). This disparity may become greater in the future with the aging of the population. AgeThe incidence of stroke rises exponentially with age, particularly in individuals older than 55 years.
CLINICALHistoryPatients typically present with sudden onset of focal neurological symptoms. Specific features of the time course and evolution, focal neurological symptoms, and global symptoms are listed below.
Physical
CausesRisk factors include epidemiologic risk factors (ie, not modifiable) and potentially modifiable risk factors.
DIFFERENTIALSCardioembolic Stroke Cavernous Sinus Syndromes Cerebral Aneurysms Glioblastoma Multiforme Head Injury Herpes Simplex Encephalitis Intracranial Hemorrhage Low-Grade Astrocytoma Meningioma Metastatic Disease to the Brain Migraine Variants Primary CNS Lymphoma Seizures and Epilepsy: Overview and Classification Subarachnoid Hemorrhage Subdural Hematoma Transient Global Amnesia Viral Encephalitis
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| Drug Name | Alteplase (Activase) |
|---|---|
| Description | Recombinant plasminogen activator that forms plasmin after facilitating cleavage of endogenous plasminogen. In clinical trials, has been shown effective in achieving TIMI 2 or 3 patency at 90 min. Heparin and aspirin are not given for 24 h after tPA. Must be given within 3 h of stroke onset. Exclude hemorrhage by CT scan. If hypertensive, lower BP with labetalol, 10 mg IV. |
| Adult Dose | 0.9 mg/kg IV; not to exceed 90 mg Give bolus of 10% of total dose to be administered, infuse remainder over next 60 min |
| Pediatric Dose | Not established |
| Contraindications | Beyond 3 h after stroke onset; cerebral hemorrhage; recent stroke (within 3 mo); serious bleeding disorder or history of GI hemorrhage; BP >200/110 mm Hg; recent surgery |
| Interactions | Anticoagulants and antiplatelets may increase risk of bleeding (do not administer aspirin, heparin, or other anticoagulants for 24 h after infusion) |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Caution in cardiovascular arrhythmias, hypotension, and perfusion arrhythmias |
Emergent heparin therapy may be given for specific indications, such as internal carotid artery dissection or cerebral venous thrombosis. Heparin therapy also may be commenced in conjunction with warfarin therapy for secondary prevention of high-risk cardioembolic stroke; it may be started either on admission (if not receiving rt-PA) or 3-5 days after stroke onset. Early use of IV heparin has not, however, been proven to be of benefit in clinical trials. For patients confined to bed who do not have excessive risk of hemorrhagic transformation, administer subcutaneous heparin to prevent deep venous thrombosis.
| Drug Name | Heparin sodium |
|---|---|
| Description | In addition to heparin sodium, low-molecular-weight heparins may be associated with lower rate of hemorrhagic complications. |
| Adult Dose | 100,000 U IV over 24 h 5000 U SC bid |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; subacute bacterial endocarditis; active bleeding; history of heparin-induced thrombocytopenia |
| Interactions | Digoxin, nicotine, tetracycline, and antihistamines may decrease effects; NSAIDs, aspirin, dextran, dipyridamole, and hydroxychloroquine may increase toxicity |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | In neonates, preservative-free heparin recommended to avoid possible toxicity (ie, gasping syndrome) by benzyl alcohol, which is used as preservative; caution in severe hypotension and shock; monitor for bleeding in peptic ulcer disease, menstruation, increased capillary permeability, and when giving IM injections |
| Drug Name | Warfarin (Coumadin) |
|---|---|
| Description | Inhibits synthesis of 6 vitamin K-dependent proteins involved in anticoagulation system (factors II, VII, IX, X; proteins C, S). Many other coumarin derivatives are used worldwide. |
| Adult Dose | Initial dose: 5 mg/d PO for 2-4 d (lower in very elderly patients) Subsequent doses determined by INR achieved and source of embolism (INR 2-3 for most cardiac sources) |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; active bleeding; heparin-induced thrombocytopenia; severe renal or hepatic disease; open wounds; gastric ulcer |
| Interactions | Extensive literature available regarding warfarin-drug interactions, with variable level of evidence; drugs that increase anticoagulant effects include co-trimoxazole, erythromycin, fluconazole, isoniazid, amiodarone, aspirin, simvastatin, sulfinpyrazone, phenylbutazone, alcohol, cimetidine, and omeprazole; drugs that inhibit anticoagulant effect include rifampin, nafcillin, cholestyramine, barbiturates, carbamazepine, sucralfate, and azathioprine; OTC NSAIDs (eg, Naprosyn, ibuprofen) and aspirin are associated with increased risk of upper GI bleeding when used with warfarin; high doses of acetaminophen can prolong INR |
| Pregnancy | X - Contraindicated in pregnancy |
| Precautions | Do not switch brands after achieving therapeutic response; caution in active tuberculosis or diabetes; patients with protein C or S deficiency are at risk of developing skin necrosis |
These agents are used for secondary prevention of ischemic stroke caused by atherosclerotic disease of small or large arteries. Data also support aspirin use within 48 h of an acute stroke.
| Drug Name | Aspirin (Anacin, Bayer Aspirin, Ascriptin, Bayer Buffered Aspirin) |
|---|---|
| Description | Inhibits prostaglandin synthesis, preventing formation of platelet-aggregating thromboxane A2. May be used in low dose to inhibit platelet aggregation and improve complications of venous stases and thrombosis. |
| Adult Dose | 75-325 mg/d PO |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; liver damage; hypoprothrombinemia; vitamin K deficiency; bleeding disorders; asthma Because of association with Reye syndrome, do not use in children ( <16 y) with flu |
| Interactions | Antacids and urinary alkalinizers may decrease effects; corticosteroids decrease salicylate serum levels; anticoagulants may cause additive hypoprothrombinemic effects and increase bleeding time; may antagonize uricosuric effects of probenecid and increase toxicity of phenytoin and valproic acid; doses > 2 g/d may potentiate glucose-lowering effect of sulfonylurea drugs |
| Pregnancy | D - Unsafe in pregnancy |
| Precautions | May cause transient decrease in renal function and aggravate chronic kidney disease; avoid use in patients with severe anemia, with history of blood coagulation defects, or taking anticoagulants |
| Drug Name | Aspirin plus slow-release dipyridamole (Aggrenox) |
|---|---|
| Description | Aspirin inhibits prostaglandin synthesis, preventing formation of platelet-aggregating thromboxane A2. May be used in low dose to inhibit platelet aggregation and improve complications of venous stases and thrombosis. Dipyridamole is platelet adhesion inhibitor that possibly inhibits RBC uptake of adenosine, itself an inhibitor of platelet reactivity. In addition, may inhibit phosphodiesterase activity, leading to increased cyclic-3', 5'-adenosine monophosphate within platelets and formation of potent platelet activator thromboxane A2. European Stroke Prevention Trial 2 demonstrated that combination therapy was better than aspirin alone for prevention of recurrent stroke or transient ischemic attack. |
| Adult Dose | 25 mg aspirin + 200 mg dipyridamole SR PO bid (1 tab bid) |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; liver damage; hypoprothrombinemia; vitamin K deficiency; bleeding disorders; asthma Because of association with Reye syndrome, do not use in children ( <16 y) with flu |
| Interactions | Aspirin: Antacids and urinary alkalinizers may decrease effects; corticosteroids decrease salicylate serum levels; anticoagulants may cause additive hypoprothrombinemic effects and increase bleeding time; may antagonize uricosuric effects of probenecid and increase toxicity of phenytoin and valproic acid; doses > 2 g/d may potentiate glucose-lowering effect of sulfonylurea drugs Dipyridamole: Theophylline may decrease hypotensive effects; antiplatelet activity may increase heparin toxicity |
| Pregnancy | D - Unsafe in pregnancy |
| Precautions | Aspirin may cause transient decrease in renal function and aggravate chronic kidney disease; avoid use in patients with severe anemia, with history of blood coagulation defects, or taking anticoagulants Caution in hypotension when using dipyridamole; dipyridamole has peripheral vasodilating effects |
| Drug Name | Clopidogrel (Plavix) |
|---|---|
| Description | Selectively inhibits ADP binding to platelet receptor and subsequent ADP-mediated activation of glycoprotein GPIIb/IIIa complex, thereby inhibiting platelet aggregation. |
| Adult Dose | 75 mg/d PO qd |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; active pathological bleeding, such as peptic ulcer; intracranial hemorrhage |
| Interactions | Naproxen associated with increased occult GI blood loss; safety of coadministration with warfarin not established |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Caution in patients at increased risk of bleeding from trauma, surgery, or other pathological conditions; caution in patients with lesions (eg, ulcers) with propensity to bleed; prolongs bleeding time |
| Drug Name | Ticlopidine (Ticlid) |
|---|---|
| Description | Reported to be 15% more effective than aspirin. However, is associated with risks of neutropenia and thrombocytopenia and requires regular blood testing; therefore, use in patients who do not respond to aspirin or are allergic to aspirin. |
| Adult Dose | 250 mg PO bid |
| Pediatric Dose | Not established |
| Contraindications | Documented hypersensitivity; neutropenia or thrombocytopenia; liver damage; active bleeding disorders |
| Interactions | Corticosteroids and antacids may decrease effects; theophylline, cimetidine, aspirin, and NSAIDS increase toxicity |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Discontinue if absolute neutrophil count decreases to <1200/mm3 or if platelet count falls to <80,000/mm3 |
| Media file 1: Anterior circulation stroke. Vascular territories. | |
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Anterior Circulation Stroke excerpt
Article Last Updated: Jan 3, 2006