Name : Hamidreza
Affiliation : Radiology department,ShohadaTajrish Hospital,SBMU
Academic Degree: Associate professor of Radiology
Resident : Ramin Pourghorban
We thank Mrs. Dabbaghi, radiographer of angiography department in Shohada Hospital, for contributing the patient??s images.
Gender : Male
Age : 43
43 year-old male with previous trauma
Axial T1-, corresponding T2-weighted and Fluid-Attenuation Inversion Recovery images (images1-3, respectively) show loss of signal void within right internal carotid artery (ICA), suggesting either slow blood flow or absence of intraluminal normal blood flow. TOF MR-Angiogram (combined image 4) reveals non-visualization of right internal carotid, implying complete obstruction of right ICA. Nevertheless, other intracranial vessels are patent and unremarkable. Conventional Digital Subtraction Angiogram (images 5-8) demonstrates a long tapered stenosis in the origin of right ICA just after the right carotid bulb, representing the string sign. Right ICA is not opacified few centimeters distal to its origin. Cross-filling of blood flow from the left ICA towards the contra-lateral side via anterior communicating artery to supply the right hemisphere territory is depicted on image-8. Axial and longitudinal Color Doppler examinations of the origin of right ICA (images9-10) show complete vascular obstruction. The above-mentioned findings, especially the characteristic conventional agiograhic features, are mostly attributable to right ICA dissection.
1. Fibromuscular Dysplasia 2.Dysgenesis of the ICA 3.Atherosclerosis 4.Radiation Treatment 5.Takayasu Arteritis 6.BehÃƒÂ§et Disease 7.Giant Cell Arteritis
Right ICA Dissection
Discussion (Related Text)
Color Duplex US: The wall of the proximal part of the ICA can be depicted with B-mode imaging and high-frequency linear transducers (4??8 MHz). Mural hematoma and thrombus may be detected as a thickened hypoechoic vessel wall. Usually, wall hematoma and intraluminal thrombus cannot be differentiated with B-mode imaging. Sometimes, an inner intimal echo helps in distinguishing wall hematoma from intraluminal thrombus or plaque in patients with thickening of the ICA wall. The sensitivity of color Doppler US decreases if a dissection causes only a low-grade stenosis. The sensitivity of color Doppler US is 95%??96% for diagnosis of internal carotid dissection causing carotid territory ischemia and 71% for dissection causing no ischemic events. The accuracy of US for craniocervical artery dissection may be improved with ??B-flow?Â US, which improves the visualization of intimal flaps, intramural hematoma, and residual flow. MR Imaging and MR Angiography: TOF MR angiography and contrast-enhanced MR angiography are commonly used to evaluate the intracranial and extracranial vessels. In a prospective blinded study, MR imaging demonstrated excellent sensitivity and specificity of 84% and 99%, respectively, compared with conventional angiography in diagnosis of internal carotid dissection. The criteria used for dissection in this study were increase in the external diameter of the artery and narrowing of the lumen. However, flow void narrowing is a less useful indicator of dissection because it can be encountered in other conditions. MR angiography with 3D TOF imaging demonstrated excellent sensitivity and specificity of 95% and 99%, respectively, in diagnosis of internal carotid dissection but poor sensitivity (20%) in diagnosis of vertebral artery dissection compared with conventional angiography. Digital Subtraction Angiography: Digital subtraction angiography is not always definitive in the diagnosis of dissection because the thickness and configuration of the arterial wall are not appreciable. Nevertheless, it has been commonly regarded as the gold standard diagnostic procedure. The string sign, the angiographic hallmark of ICA dissection, is a long, tapered, usually eccentric and irregular stenosis that begins distal to the carotid bulb. Focal narrowing with a distal site of dilatation is referred to as the ??string and pearl?Â sign. In a series of 42 patients, angiographic findings of spontaneous cervical artery dissection included tapered stenosis in 46% of affected vessels, tapered stenosis with a concomitant dissecting aneurysm in 27%, occlusion in 20%, and only a dissecting aneurysm in 7%. Pathognomonic signs, such as a double lumen or intimal flap, are rarely observed. The ??flame?Â sign, a tapered occlusion that spares the carotid bulb, is highly suggestive of dissection.
1. Rodallec MH, Marteau V, Gerber S, et al. Craniocervical Arterial Dissection: Spectrum of Imaging Findings and Differential Diagnosis. RadioGraphics 2008; 28: 1711-1728.