Diagnostic ultrasound ( PDFDrive )

946 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
A
B
C
FIG. 26.39 Fibromuscular Dysplasia. (A) Longitudinal color Doppler image
of the middle to distal portion of the ICA shows velocity elevation and signiicant
stenosis. (B) Same patient’s proximal portion of the ICA shows no stenosis. (C)
Angiogram demonstrates typical appearance of ibromuscular dysplasia in the mid
and distal ICA. Note the beaded appearance resulting from focal bands (arrow) of
thickened tissue that narrow the lumen.
carotid dissection or subsequent thromboembolic events (Fig.
26.39). Arteritis resulting from autoimmune processes (e.g.,
Takayasu arteritis, temporal arteritis) or radiation changes can
produce difuse concentric thickening of carotid walls, which
most frequently involves the CCA 23,216,217 (Fig. 26.40).
Cervical trauma can produce carotid dissections or aneurysms.
Carotid artery dissection results from a tear in the intima,
allowing blood to dissect into the wall of the artery, which
produces a false lumen. he false lumen may be blind ended or
may reenter the true lumen. he false lumen may occlude or
narrow the true lumen, producing symptoms similar to carotid
plaque disease. Dissections may arise spontaneously or secondary
to trauma or to intrinsic disease with elastic tissue degeneration
(e.g., Marfan syndrome) or may be related to atherosclerotic
plaque disease. 20 he ultrasound examination of a carotid dissection
may reveal a mobile or ixed echogenic intimal lap,
with or without thrombus formation. 218 Frequently, there is a
striking image/Doppler mismatch with a paucity of gray-scale
abnormalities seen in association with marked low abnormalities
(Fig. 26.41).
Color or power Doppler ultrasound can readily clarify the
source of this mismatch by demonstrating abrupt tapering of
the patent, illed lumen to the point of an ICA occlusion. When
the ICA is occluded, the proximal ipsilateral CCA will demonstrate