Dissection occurs when blood extrudes into the connective tissue framework of a vessel wall, causing separation of the natural vessel layers. When a dissection occurs between intima and media layers, luminal narrowing or occlusion can occur. Dissection between the media and adventitia results in aneurysmal dilation, which can lead to rupture. Rupture of an artery with subsequent encapsulation of the extravascular hematoma results in pseudoaneurysm, which can lead to luminal narrowing. Dissection of the cervical and intracranial vessels is an uncommon but increasingly recognized condition.
The cervical (extracranial) internal carotid artery is affected in 75% of patients (usually approximately 2 cm distal to the bifurcation) and the extracranial vertebral artery in 15% of patients. The remaining cases usually involve the intracranial internal carotid artery, intracranial vertebral artery, middle cerebral artery, or basilar artery. Cervicocephalic dissections may occur spontaneously or secondary to major or minor trauma. In some patients, they are associated with an underlying arteriopathy. Fifteen percent of cases are bilateral, and one half of these occur in patients with underlying fibromuscular dysplasia.
The hallmark of dissection is hemorrhage within the vessel wall. In some patients, an intimal tear allows intravascular blood to communicate directly with the vessel wall cavity. In others, an intramural hematoma develops without a direct connection with the vessel lumen.
In extracranial carotid and vertebral dissections, hemorrhage into the medial-adventitial layers occurs most commonly. This occasionally causes the external vessel wall to bulge outward, forming a dissecting aneurysm that can compress local structures. In intracranial carotid and vertebral dissections, subintimal tears occur more commonly, leading to formation of intramural hematomas that protrude inward and narrow the vessel lumen. Most ischemic symptoms (85-95%) are caused by emboli from the site of the dissection, while the remainder are due to vessel narrowing with hemodynamic insufficiency (5-15%) or a combination of both.
Hospital-based series suggest that cervicocephalic dissections are responsible for 1–2.5% of ischemic strokes in the general population and for 5–20% of strokes in individuals younger than 45 years. In one community-based study, the average annual incidence of spontaneous cervical internal carotid artery dissections was 2.6 cases per 100,000. While improved imaging techniques and growing awareness of the disorder have led to increased recognition of these syndromes, mild cases likely will remain undiagnosed. Multiple dissections occur in 10%, with the most common being bilateral vertebrobasilar lesions.[1]
International frequency of dissection syndromes is similar to that in the United States.
Mortality/Morbidity
Morbidity and mortality of cervicocephalic dissections vary according to the vessel and location of the dissection. Death rates for extracranial carotid and vertebral dissections are approximately 5-10%. In contrast, mortality rates for intracranial carotid and basilar dissections approach 70% or higher.
Demographics
Persons of all ages may be affected; however, dissections occur more frequently in younger individuals. In extracranial carotid dissection, 70% of cases occur in persons aged 35–50 years. Intracranial carotid dissection tends to occur particularly in adolescents and adults younger than 30 years.
While some studies have reported that males and females are affected equally in extracranial carotid dissections, the Cervical Artery Dissection and Ischemic Stroke Patients (CADISP) group reported that cervical artery dissection was more common in men and men were older at onset. Intracranial dissections are more common in younger males than in females. Extracranial vertebral artery dissections and multiple vessel dissections are more common in women than in men.
In patients younger than 30 years old, the most common presentation is internal carotid artery dissection without subarachnoid hemorrhage (SAH). In patients older than 30 years old, vertebrobasilar artery dissection with SAH is most common.
The most frequent presenting complaints with cervicocephalic dissections are ischemic symptoms that include transient ischemic attack (TIA) or stroke (cerebrovascular accident).
Up to two thirds of patients complain of ipsilateral neck, scalp, or head pain, occurring in both carotid and vertebral artery dissections.
Up to one fourth of patients report pulsatile tinnitus or a subjective bruit, particularly with carotid artery dissections.
In a large, pooled, observational study of 982 patients with cervical artery dissections, significant differences were observed in patients with internal carotid artery dissections (ICAD) compared to vertebral artery dissections (VAD). Most notably, patients with ICAD were older, more often men, more frequently had a recent infection, and less frequently had cerebral ischemia. In contrast, patients with VAD more frequently reported a history of neck trauma and cervical pain and less frequently presented with headache. Of those patients with cerebral ischemia, ICAD patients had more severe baseline National Institutes of Health Stroke Scale scores.[2]
Dissection aneurysms may present with alterconsciousness and cause SAH. Rebleeding can occur in up to 30% of cases resulting in high mortality. Traumatic dissections or pseudoaneurysms can present similary but may also produce massive external hemorrhage or hematomas.[3]
Cerebral ischemia occurs in at least 75% of reported cases (TIAs in 30%, infarcts in 45-50%).
Neurologic deficits reflect the ultimate site of ischemia in the ipsilateral anterior circulation.
In extracranial carotid dissections, local symptoms may occur as the intramural hematoma expands outward, compressing local structures.
Examination findings may include the following:
Ipsilateral partial Horner syndrome (32-82% of patients in various series)
Ipsilateral cranial nerve palsies, particularly cranial nerves IX, X, XI, and XII (5-12% of patients in various series)
Audible bruit (up to 20% of patients)
Intracranial carotid artery
Patients with intracranial carotid dissections usually present with headache followed by a major ischemic stroke.
Some patients initially may present with a seizure, syncope, or altered level of consciousness.
One fifth of patients develop subarachnoid hemorrhage.
Extracranial vertebral artery
This dissection is characterized by headache (often occipital) or neck pain and signs of ischemia in the posterior circulation.
Infarcts in the territory of the posterior inferior cerebral artery (commonly with a lateral medullary syndrome) are frequent.
Intracranial vertebrobasilar dissection
This dissection may present with symptoms of posterior circulation ischemia (particularly brainstem), subarachnoid hemorrhage (occurs in one half of patients), or both.
Major blunt trauma to the head and neck can produce cervicocephalic dissection. In spontaneous dissections (dissection in absence of major trauma), a history of minor trauma is a precipitating factor in at least 25% of dissections. The CADISP study group reported that 40.5% of cervical artery dissection patients had prior cervical trauma, which was mild in 88% of cases.
Types of trauma associated with cervicocephalic dissections include chiropractic neck manipulations[4] , sporting activities, coughing, sneezing, sexual activity, and more intense forms of blunt trauma (eg, motor vehicle accidents, falls, strangulation, hanging).
Arteriopathies have been associated with cervicocephalic dissections.
Fibromuscular dysplasia (the most common underlying arteriopathy, found in as many as 15% of patients)
Extreme vessel tortuosity
Marfan syndrome
Ehlers-Danlos syndrome
Alpha-1-antitrypsin deficiency
Cystic medial necrosis
Type 1 collagen point mutation
Other connective tissue disorders
Moyamoya disease
Meningovascular syphilis
Associations also have been reported with systemic infections, hypertension, migraine, elevated homocysteine levels, alcohol use, and oral contraceptive use. Hypercholesterolemia and obesity have been reported to be inversely associated with cervical artery dissection.
Historically, catheter angiography has been considered the criterion standard for diagnosing cervicocephalic dissections. A variety of abnormal patterns may be seen (see image below). The diagnosis is confirmed if an intimal flap or double-barrel lumen (secondary to a dissecting aneurysm) is seen.
View Image
Cerebral angiogram of a left internal carotid dissection showing gradual vessel tapering to occlusion.
Typical angiographic findings can include luminal stenosis "string sign," fusiform dilation with proximal or distal narrowing, vessel occlusion, or initimal flap typically at the proximal end of the dissection. The "string sign" indicating vessel luminal narrowing is the most common angiographic sign.
Frequently, only irregular vessel narrowing may be found, often with a string sign, gradual vessel tapering, and/or distal embolic occlusions. While these findings may suggest an underlying dissection, in some patients they may not be diagnostic. Evidence of fibromuscular dysplasia or vessel tortuosity also may be found, suggesting an underlying predisposing condition.
Brain magnetic resonance imaging (MRI) may be normal or show evidence of infarction related to the dissection. Magnetic resonance angiography (MRA) may show patterns similar to those on catheter angiography, but this study is frequently not as sensitive. Axial T1 sequences through the vessel lumen may be particularly helpful in confirming diagnosis, especially if a crescent sign (elliptical bright signal within a vessel wall that surrounds a signal flow void) is visualized (see image below).
View Image
Axial T1-weighted MRI demonstrating a crescent sign (arrow) in a patient with a left internal carotid artery dissection.
Computed tomography angiography (CTA) may show patterns similar to those seen on MRA or catheter angiography.
In proximal carotid dissections, carotid duplex ultrasonography most commonly shows evidence of a distal severe stenosis or occlusion. Occasionally, a double lumen may be visualized on B mode imaging.
Transcranial Doppler studies may demonstrate collateral flow patterns or evidence of microemboli.
Plain CT of the head can be useful for evaluating for subarachnoid hemorrhage or ischemic stroke.
Pathologic specimens commonly demonstrate evidence of an intramural hematoma. In some patients, evidence of an underlying connective tissue disorder or arteriopathy may be identified.
Medical therapy should be started immediately for cervicocephalic dissections except in cases of associated with intracranial hemorrhage, large ischemic stroke, or traumatic injuries contraindicating anticoagulation. Anticoagulation therapy typically consists of a heparin drip in the acute period followed by transition to oral agents such as coumadin. Antiplatelet therapy can also be effective.[5]
Patients with symptoms of cerebral ischemia generally should be admitted to a monitored bed and provided supportive stroke care (eg, intravenous fluids, prevention of hyperglycemia).
Patients presenting within 3–4 1/2 hours of stroke symptom onset may be considered for treatment with intravenous tissue plasminogen activator. A growing number of studies have suggested that there is not an increased rate of symptomatic hemorrhage or unfavorable outcomes in this population. However, the CADISP co-investigators also failed to find any trend towards benefit in dissection patients treated with thrombolysis compared with those not treated.[6] Thus, the role of thrombolysis in patients with acute infarction secondary to dissection is unproven.[7]
No randomized controlled trials have been performed to determine the optimum antithrombotic treatment regimen. Current options include anticoagulants[8] , antiplatelet agents, and surgical and/or endovascular treatment.
Since most ischemic strokes caused by dissections are likely to be due to emboli originating from a thrombus at the site of dissection, many experts recommend anticoagulation for the first 3–6 months. This practice is supported by several small case series demonstrating good outcome with low complication rates in patients receiving anticoagulation. However, no data from a randomized, controlled trial are available to determine if antiplatelet therapy is as effective as or superior to anticoagulation. In the nonrandomized arm of the Cervical Artery Dissection Stroke Study (CADISS-NR), there was no evidence for superiority of anticoagulation or antiplatelet therapy in prevention of stroke.[9] However, mean time to treatment from symptom onset in this study was 10.8 days, which may have been beyond the window of highest risk.
Anticoagulation is contraindicated in intracranial dissections complicated by subarachnoid hemorrhage.
In patients with hemodynamically significant dissections, hypertensive and/or hypervolemic therapy may be initiated.
Some experts recommend avoidance of oral contraception and hormonal replacement therapy in patients with cervicocephalic dissections, since these agents may promote intimal proliferation.
Repeat imaging (angiography, MRA, CTA) generally is recommended at 3-6 months. In most patients, the vessel wall is fully healed at that time; thus, patients may be switched to aspirin. Alternatively, all therapy may be discontinued.
In rare patients with symptoms refractory to medical management, patients with subarachnoid hemorrhage, and those with expanding dissecting aneurysms, or intradural dissections, endovascular therapy or surgical procedures may be indicated. Endovascular procedures include angioplasty and stenting, vessel occlusion by embolization or coiling. In cases where endovascular techniques are not an option, open surgical treatments include vessel occlusion by clipping, vessel clipping followed by bypass, and clipping or wrapping of associated aneurysms.
Anticoagulation with intravenous heparin followed by conversion to oral warfarin has been recommended as first-line treatment of patients with extracranial carotid artery dissections to prevent the risk of thromboembolic complications in patients with no contraindications to anticoagulation.
After 6 months of therapy, patients should be reimaged and assessed for arterial recanalization.
Antiplatelet therapy can also be effective in patients with dissections.
Patients with contraindications to anticoagulation should be evaluated for endovascular or surgical treatments.
Extracranial vertebral artery dissection
Similar to extracranial carotid dissections, first-line treatment of extracranial vertebral artery dissections consists of anticoagulation with intravenous heparin followed by transition to oral Coumadin for 3 to 6 months.
Endovascular options include angioplasty and stent placement to recanalize the vertebral artery. Vertebral artery sacrifice through endovascular obliteration or surgical ligation may also be considered in select patients.
Intracranial arterial dissection
First-line treatment for intracranial arterial dissections is surgical or endovascular intervention. Intracranial dissections are typically associated with subarachnoid hemorrhage and anticoagulation is contraindicated due to high risk of rebleeding.
Clinical Context:
Augments activity of antithrombin III and prevents conversion of fibrinogen to fibrin; does not actively lyse but is able to inhibit further thrombogenesis; prevents reaccumulation of a clot after spontaneous fibrinolysis.
Clinical Context:
Interferes with hepatic synthesis of vitamin K–dependent coagulation factors; used for prophylaxis and treatment of venous thrombosis, pulmonary embolism, and thromboembolic disorders.
The risk of recurrent dissection is approximately 1% per year. Recurrent dissections are more likely to occur in previously unaffected vessels than at the sites of previous dissections.
In extracranial carotid dissections, 50% of patients have no residual neurologic deficits, 20% have mild deficits, and 25% have moderate-to-severe residual deficits.
In intracranial carotid dissections, one half of survivors have moderate-to-severe residual deficits.
Of patients with extracranial vertebral dissections, 80-85% have mild neurologic deficits or are neurologically normal at the follow-up point. Moderate-to-severe deficits are found in 10%.
The morbidity and mortality rates for intracranial vertebrobasilar dissection are not well defined but tend to be higher due to increased occurrence of subarachnoid hemorrhage and brainstem infarction.
Gaurav Gupta, MD, Assistant Professor, Section Head, Endovascular and Cerebrovascular Neurosurgery, Fellowship Director, Endovascular Neurosurgery Fellowship (Site), Department of Surgery, Division of Neurosurgery, Rutgers Robert Wood Johnson Medical School
Disclosure: Nothing to disclose.
Coauthor(s)
Arthur Carminucci, MD, Resident Physician, Department of Neurological Surgery, Rutgers New Jersey Medical School
Disclosure: Nothing to disclose.
Sudipta Roychowdhury, MD, Clinical Associate Professor of Radiology, Department of Radiology, Rutgers Robert Wood Johnson Medical School; Attending Radiologist/Neuroradiologist, University Radiology Group, PC
Disclosure: Nothing to disclose.
Specialty Editors
Francisco Talavera, PharmD, PhD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference
Disclosure: Received salary from Medscape for employment. for: Medscape.
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
Disclosure: Nothing to disclose.
Chief Editor
Helmi L Lutsep, MD, Professor and Vice Chair, Department of Neurology, Oregon Health and Science University School of Medicine; Associate Director, OHSU Stroke Center
Disclosure: Medscape Neurology Editorial Advisory Board for: Stroke Adjudication Committee, CREST2; Physician Advisory Board for Coherex Medical; National Leader and Steering Committee Clinical Trial, Bristol Myers Squibb; Consultant, Abbott Vascular, Inc. .
Additional Contributors
Chelsea S Kidwell, MD, Professor, Department of Neurology, University of Arizona College of Medicine
Disclosure: Nothing to disclose.
William J Nowack, MD, Associate Professor, Epilepsy Center, Department of Neurology, University of Kansas Medical Center
Disclosure: Nothing to disclose.
Acknowledgements
Richard E Burgess, MD, PhD Assistant Professor, Department of Neurology, Georgetown University Hospital; Medical Director, Clinical Stroke Service
Richard E Burgess, MD, PhD is a member of the following medical societies: American Academy of Neurology and American Heart Association
Disclosure: Nothing to disclose.
References
Yamaura A. Nontraumatic Intracranial Arterial Dissection: Natural History, Diagnosis, and Treatment. ContempNeurosurg. 1994. 16:1-6.
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