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13 — Special Considerations in Evaluating Nonatherosclerotic Arterial Pathology
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for about 5 cm before it divides into the frontal and parietal branches. The temporal artery is small and superficial requiring a high-frequency transducer in order to properly insonate it.
If the patient presents with upper extremity symptoms, an upper extremity duplex ultrasound is performed, paying close attention to the subcla- vian, axillary, and brachial arteries. The images in Figure 13-1 were obtained from a 75-year-old Cau- casian female who presented with temporal head- aches. Additionally, she complained of muscle aching in shoulders and arm fatigue with physical activity. A physical examination revealed decreased pulses in both upper extremities. She underwent an upper ex- tremity arterial duplex ultrasound. A high-grade ste- nosis was found within the left axillary artery with a PSV of greater than 300 cm/s (Fig. 13-1A). The gray- scale image of the vessel at this level was unremark- able. Continuing distally down the arm, the brachial artery was identified. Sagittal examination revealed an irregular lumen and mural thickening. An area with echolucency surrounding the residual lumen was observed (Fig. 13-1B). The color imaging displayed several areas of poor filling and aliasing. Within the duplex ultrasound of the right upper extremity, the findings revealed a stenosis in the brachial artery (Fig. 13-1C–E). Changes in color flow were apparent at the stenosis; in addition, areas of echolucency were present within the vessel.
A stenosis due to giant cell or temporal arteritis will produce the typical ultrasound findings associat- ed with any stenosis. The primary tool used to define a stenosis will be a focal increase in PSV. A PSV that is twice the value of the PSV in the adjacent more proximal vessel is indicative of at least a 50% steno- sis. This criterion can be applied to most arteries. On B-mode image, giant cell arteritis often appears as a concentric wall thickening, which is hypoechoic. This thickening can occur over a long segment of the vessel and can lead to a tapering of the arterial lu- men.4 Additionally, an anechoic area may be present surrounding the vessel producing a “halo” around the vessel. This is thought to occur due to white blood cell infiltration. The “halo” should be present in both transverse and sagittal imaging planes.
TAKAYASU’S ARTERITIS
Takayasu’s arteritis mainly impacts the aortic arch and its large branches. The subclavian arteries are involved in more than 90% of the cases, whereas the common carotid arteries are involved in ap- proximately 60% of patients.5 As with other forms of arteritis, the inflammatory process may be part of an immune system disorder. Takayasu’s arteritis involves all three layers of the vessel wall. It can lead
to a partial obstruction of the vessel lumen or com- plete vessel occlusion. Vessel walls may also become weakened such that aneurysm formation may oc- cur. The disease is most common in Southeast Asia. There is an eight to one female to male prevalence with greater than 80% of affected individuals being younger than 40 years of age. The presenting symp- tom of patients is often an absent peripheral pulse. There may be a brachial blood pressure gradient of greater than 30 mm Hg. Lightheadedness, vertigo, amaurosis fugax, transient ischemic attacks, hemi- paresis, diplopia, and upper extremity claudication may also occur. Angiography and ultrasound can be used to diagnose the presence of this disease.
Scanning Technique
The sonographic examination of a patient with sus- pected Takayasu’s arteritis will be similar to that em- ployed for temporal arteritis. The portion of the vascular system interrogated is usually the carotid and subclavi- an vessels. The grayscale image is closely examined for evidence of wall thickening, whereas spectral Doppler and color imaging are used to detect a stenosis.
The ultrasound image typically reveals thickened walls with concentric narrowing. The thickened ar- eas are usually homogeneous in appearance with ad- jacent segments of the vessels appearing normal and disease free (Fig. 13-2A–C). Often, the wall thicken- ing will occur over long segments for several centi- meters. The stenosis will produce elevated velocities within the segment with poststenotic turbulence pre- senting distally. In a transverse view, the circumfer- ential thickening of the vessel wall has been termed the macaroni sign.6 Distal to areas of stenosis, damp- ened arterial signals will be present (Fig. 13-2D).
THROMBOANGITIS OBLITERANS (BUERGER’S DISEASE)
Thromboangiitis obliterans or Buerger’s disease is an- other nonatherosclerotic inflammatory disease. This disease affects the small- and medium-sized arteries involving the upper and lower extremities, including the digital, plantar, tibial, peroneal, radial, and ulnar arteries.7 This disease typically manifests in patients younger than the age of 45 and has a three to one male to female distribution. Presenting symptoms can consist of ischemic digital ulcers. Ulcerations on the toes are slightly more common than finger ulcers. Gangrene of the digits can also occur. Superficial thrombophlebitis can be seen in one-third of patients, and half of patients have symptoms involving numb- ness and tingling in hands and feet. Other symp- toms include claudication in the arch of the foot and also in the arms and hands.8 This disease is always