How do arterial dissections occur?
Arterial dissections occur when there is a hemorrhage into the arterial wall, separating the layers, allowing blood to collect in the media or the adventitia layer, and creating a false lumen. Dissections may occur due to a tear in the intima or direct hemorrhage into the media from the vasa vasorum. However, because intracranial arteries lack a vasa vasorum, hemorrhage occurs due to an intimal tear at that site. The mural hematoma can dissect through the media, which results in luminal narrowing or the subadventitial plane, resulting in pseudoaneurysm formation.
What age internal carotid artery (ICA) occurs most frequently?
ICA dissection occurs at any age, but it is more common in people younger than age 50 years of age. Carotid dissection should be suspected in young adults presenting with an acute stroke.
How is the etiology of internal carotid artery dissection?
The etiology can be spontaneous, traumatic, and iatrogenic.
Which are some risk factors for ICA dissection?
Some important risk factors for ICA dissection are cervical trauma, hypertension, connective tissue disorder (fibromuscular dysplasia, Ehlers-Danlos syndrome, Marfan syndrome, osteogenesis imperfecta). Other predisposing factors are cystic media necrosis, segment mediolytic arteriopathy, reticular fiber deficiency, homocystinuria, alpha-1 antitrypsin deficiency, autosomal dominant polycystic kidney disease, migraine with aura, reversible cerebral vasoconstriction syndrome, infection, smoking, alcohol use, using birth control pills, low cholesterol levels, long styloid process (Eagle syndrome).
Which occurs more frequently, the extracranial or the intracranial internal carotid artery dissection?
Extracranial internal carotid artery dissection is more common than intracranial internal carotid artery dissection. The cervical segment is the most common site of ICA dissection; it typically occurs 2-3 cm beyond the common carotid bifurcation.
How are the clinical manifestations of internal carotid artery dissection?
Some patients are asymptomatic, and the clinical presentation is often nonspecific. Many patients may present ipsilateral headaches and neck pain. Retroorbital headache with the presence of oculosympathetic paresis (Horner’s syndrome) is suggestive of internal carotid artery dissection. Other signs and symptoms may include weakness on one side of the body, difficulty understanding speech or speaking, pulsing sound in an ear, trouble swallowing, lost sense of taste, retinal ischemia, ischemic stroke, intracranial hemorrhage, and subarachnoid hemorrhage.
What are the CT findings for dissection of the internal carotid artery?
The CT findings are cerebral ischemia/infarct and hematoma in the wall of the ICA as a spontaneous crescent-shaped hyperattenuating focus surrounding a narrowed lumen. A CT may demonstrate enlargement of the dissected artery, an abnormal vessel contour, narrowed eccentric lumen surrounded by a crescent-shaped mural thrombus, and intimal flap. Other findings are dissecting aneurysm (pseudoaneurysm), occlusion of the ICA due to a luminal thrombus, and a thin annular enhancement surrounding the mural hematoma, possibly resulting from enhancement of the vasa vasorum.
What are the MR findings for dissection of the internal carotid artery?
The MR findings are cerebral ischemia/infarct on DWI/ADC and FLAIR. Dissections usually show a periarterial rim of intramural hematoma detected as a crescent sign with high signal on fat-suppressed T1-weighted images, T2-WI, and DWI, which may be eccentric or circumferential. Intimal flaps are usually at the proximal margin of the dissection. Vessel wall MR imaging may be helpful for the detection of arterial dissection and mural injury. MRA shows luminal compromise, ranging from slight stenosis to severe narrowing or complete occlusion, with absent flow void. Occasionally pseudoaneurysms may occur, which are outpouchings of an arterial wall, resulting in luminal dilation.
Which are the treatment options for internal carotid artery dissection?
The treatment options depend on age, overall health, and symptoms. Early treatment with antithrombotic therapy is essential for decreasing the incidence of ischemic strokes. Occasionally, endovascular treatment putting a stent into the artery may be the best therapeutic option. Surgical intervention has a limited role.
Which is the differential diagnosis of ICA dissection?
The differential diagnosis is fibromuscular dysplasia, atherosclerosis, carotid web, dysgenesis of the ICA, isolated traumatic ICA pseudoaneurysm.
Digital subtraction angiography (DSA) demonstrates stenosis of the proximal right internal carotid artery shortly after the carotid bifurcation, followed by parietal irregularities extending from the cervical portion to the petrous segment – grade II injury. DSA also reveals an occluded left internal carotid artery after the carotid bulb without intracranial opacification – grade IV injury. Collateral refilling of the left middle cerebral artery via vertebrobasilar / circle of Willis.
Impression: Angiogram confirms the diagnosis of bilateral ICAs dissection.