Page 95 - Libro 2

5 — Uncommon Pathology of the Carotid System
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ARTERITIS
Arteritis is an inflammation of the artery wall that results in breakdown of parts of the wall structure and may conclude in occlusion and sometimes distal ischemia. In the vascular laboratory, two forms of arteritis may be seen in a carotid artery examination, Takayasu’s disease, or temporal arteritis, a form of giant cell arteritis.
Takayasu’s arteritis affects the aortic arch and great vessels, including the brachiocephalic, carotid, and subclavian arteries. Giant cell arteritis affects medium and larger sized arteries, so it may also af- fect the aortic arch and carotid arteries, but the vas- cular laboratory is usually asked to look specifically at the superficial temporal artery to assist in the di- agnosis. There are no definitive ultrasound criteria for arteritis, and it is diagnosed through a series of blood tests and clinical presentations.
SIGNS AND SYMPTOMS
There is a wide variety of clinical presentations for arteritis and no known etiology. However, autoim- mune deficiencies are thought to be the suspect in these diseases, and women outnumber men 2:1. Al- though both young and old can be afflicted with arte- ritis, young people generally present with Takayasu’s disease, and temporal arteritis generally affects the elderly. In Takayasu’s disease, there may be claudica- tion of the arms with no radial pulses if the subclavi- an arteries are affected. TIA, visual changes, stroke, and multiple bruits may also be encountered.12 Tem- poral arteritis is likely to cause headaches, low-grade fever, jaw claudication, tenderness in the temporal region, and visual problems, including blindness.
SONOGRAPHIC EXAMINATION TECHNIQUES
Takayasu’s arteritis will generally be suspected in young people, especially young women. It may re- sult in a vascular laboratory request for a carotid and renal examination because the obstruction of the arch and great vessels are most commonly seen in this order: subclavian, common carotid, aorta, and renal arteries. If lesions are seen in the carotid arter- ies, they are likely to appear as long, smooth, ho- mogeneous narrowings in the artery, and appear to be more of a general wall thickening as opposed to typical atherosclerotic plaque within the lumen.
Giant cell arteritis may affect branches of the ECA including the facial, occipital, and internal maxillary, but the most accessible branch is the superficial tem- poral artery (STA). The STA can be scanned as it pro- gresses up the temporal side of the head above the ear
and across the forehead. If an echolucent or lightly echogenic “halo” surrounds the artery at any point, it is a positive sign of arteritis. The inflammation in this disease may be spotty, affecting segments of the artery and may include stenosis or occlusion. It is best to use the highest frequency transducer, such as a 12-MHz or 15-MHz transducer. The STA is best located anterior to the ear, and if normal in that area, a pulse can be palpated. The course of the artery should be followed transversely along the side of the head and across the forehead where there are branches. Look for the char- acteristic “halo” to identify areas of inflammation and avoid “spot checking” because the inflamed areas are intermittent and may be missed without a complete scan of the temporal artery. Look for areas of stenosis or occlusion, if possible with color. It is best to obtain a Doppler waveform if any areas of aliasing are found in color. Otherwise, a sample Doppler signal with a high-resistance waveform can be documented and is considered normal.
Technical Considerations
When performing an ultrasound on a patient with Takayasu’s arteritis, pay special attention to obtain Doppler waveforms in the most proximal areas pos- sible (i.e., the brachiocephalic artery on the right and as proximal as possible on the left). Be sure to obtain bilateral brachial pressures and subclavian artery waveforms to assess the involvement of the subclavian arteries in the disease and/or the proxi- mal or distal aorta. Take multiple B-mode images in longitudinal and transverse views and closely exam- ine these for any arterial thickening or stenoses, es- pecially in the common carotid arteries.
With temporal arteritis, the entire course of the STA should be examined with transverse B-mode im- aging. This approach is used to identify any areas with a halo or document no evidence of a halo with at least three representative images in transverse view. Use color-flow imaging to get an overview rep- resentation of flow within the temporal artery. Ob- tain a Doppler sample of a normal segment and any areas suspected of stenosis or occlusion.
DIAGNOSIS
Although there is no definitive test for these inflam- matory diseases, duplex ultrasound can assist with information used to affirm the diagnosis. Takayasu’s patients will typically have an unusual appearance of thickened artery walls with some patients dem- onstrating long, narrowed stenoses of the common carotid arteries. Often, the disease appears to be concentric and evenly distributed when imaged in transverse view. This is in contrast to atherosclerotic