Laboratory Studies
Laboratory studies are primarily used to exclude an underlying connective tissue disorder.
Studies may include erythrocyte sedimentation rate (ESR), antinuclear antibody (ANA), alpha 1-antitrypsin, and homocysteine level.
Imaging Studies
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.
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).
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.
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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.
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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.
Procedures
Lumbar puncture may be performed in selected patients with intracranial vessel dissections to exclude subarachnoid hemorrhage.
Connective tissue biopsy may be performed in patients in whom an underlying connective tissue disorder is suspected.
Histologic Findings
Pathologic specimens commonly demonstrate evidence of an intramural hematoma. In some patients, evidence of an underlying connective tissue disorder or arteriopathy may be identified.
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Cerebral angiogram of a left internal carotid dissection showing gradual vessel tapering to occlusion.
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Axial T1-weighted MRI demonstrating a crescent sign (arrow) in a patient with a left internal carotid artery dissection.
