Vascular Diseases of the Upper Extremities

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CHAPTER 117 Vascular Diseases of the Upper Extremities

Symptomatic arterial occlusive disease of the upper extremity occurs much less frequently compared with arterial occlusive disease of the lower extremities. The spectrum of pathology that one is likely to encounter is also somewhat different. Whereas almost all lower extremity occlusive disease is the result of long-standing atherosclerosis, nonatherosclerotic disease and uncommon causes make up a substantial part of the case mix of clinicians dealing with patients suffering from upper extremity arterial disease. Furthermore, apart from intrinsic vascular disease, there are other well-recognized extrinsic entities that may compromise the arterial supply of the upper extremity.

There are several main reasons why examinations of the upper extremity arterial tree account for a minority of all vascular examinations in the average radiologic practice. The abundant collateral supply in the lower neck, shoulder, and upper arm regions provide a robust means for the reconstitution of distal perfusion, thus delaying symptoms. Also, a large fraction of patients suffer from small vessel disease, which is primarily managed medically instead of with percutaneous or surgical techniques. When the clinical history and laboratory information suggest small vessel disease, many patients are not even referred for vascular imaging because the information obtained does not necessarily influence treatment.

In this chapter, different vascular diseases affecting the upper extremity are discussed, as well as the relative merits and shortcomings of different techniques for imaging the upper extremity vasculature in the context of the most frequent diseases one is likely to encounter.

LARGE VESSEL DISEASE OF THE UPPER EXTREMITY

Large vessel occlusive disease of the upper extremity encompasses several well-recognized disease entities. The most frequently encountered disease underlying upper extremity ischemia is atherosclerosis. Other entities one is likely to encounter are thoracic outlet syndrome, autoimmune vasculitis, thromboembolism, and vascular damage caused by trauma, sports injuries, and radiation therapy.

Patients with atherosclerotic occlusive disease typically present with upper extremity claudication or steal phenomenon. The most common locations for upper extremity large vessel involvement include the brachiocephalic and subclavian arteries. However, atherosclerosis can also cause small vessel obstruction by atheromatous embolization or thromboembolism. A particularly helpful clinical clue in establishing the correct cause is the age of the patient. Atherosclerotic disease of the upper extremity tends to affect older adult patients, whereas nonatherosclerotic upper extremity arterial occlusive disease affects younger patients.¹

The upper extremity is a frequent site for autoimmune vasculitis. Vasculitis is usually defined as a sterile inflammation of the vessel wall. In contrast to patients suffering from atherosclerosis, patients with vasculitis are often younger and have elevated erythrocyte sedimentation rates, antineutrophilic cytoplasmic antibodies (ANCA), and antiendothelial cell antibodies.² In addition to the local symptoms caused by vessel narrowing, many patients also suffer from concomitant constitutional symptoms such as fever, malaise, myalgia, and arthralgia. The upper extremity is most often affected by Takayasu disease and giant cell arteritis (GCA). These are histologically similar diseases but Takayasu disease tends to affect any of the aortic arch vessels as well as the arch itself, and sometimes the pulmonary and coronary arteries, whereas GCA tends to affect the subclavian arteries in a typical symmetrical pattern.³ A specific clinical constellation associated with GCA is polymyalgia rheumatica. In polymyalgia rheumatica, the vasculitis is located more distally in the cervicocranial arteries. Up to 50% of patients suffer from intermittent claudication of the jaw, tongue, or throat, and up to 33% of patients present with visual complaints such as amaurosis fugax or even blindness.⁴

The group of neurovascular disorders caused by extrinsic compression of the subclavian and axillary arteries and veins as well as the brachial plexus is called cervicoaxillary compression syndrome. The more popular name for this disorder is the thoracic outlet syndrome (TOS). Symptoms are caused by compression at the interscalene triangle, costoclavicular space, or retropectoralis minor space.⁵ Compression can be caused by a variety of causes such as a fibrous band, supernumerary cervical ribs, or excessive callus formation subsequent to a clavicular fracture. A large majority of cases (70% to 90%) is caused by involvement of the brachial plexus. In less than one third of cases, arteries and veins are involved.

Blunt and penetrating trauma to the chest and upper extremity may compromise the vascular supply as well. Other causes of injury to the upper extremity vessels are radiation therapy for malignancies of the breast, head, and neck and repetitive injury in athletes such as baseball pitchers, volleyball players, butterfly swimmers, and weight lifters.

Prevalence and Epidemiology

The incidence and prevalence of upper extremity atherosclerotic disease are not known. However, it is important to realize that the prevalence of atherosclerotic lesions in the upper extremity in absolute terms is much lower compared with the aortoiliac arteries and lower extremities. The reasons for this relative paucity of symptomatic atherosclerosis in upper extremity arteries remain unknown at present. Possible explanations include better collateral circulation, reduced muscle mass, and less vigorous use of the upper extremity compared with the lower extremity.

The estimated incidence of Takayasu arteritis is 2.6 cases per million in the United States, with higher incidences reported in young women and patients of Asian origin. Women in their second and third decades of life account for the vast majority of patients because they tend to be affected about eight to nine times more often than men. Conversely, GCA tends to affect older patients, peaking in the age group between 70 and 80 years. The estimated incidence of GCA is 2 to 20/million, with women being affected about two to four times more often than men.⁶

The incidence of thoracic outlet syndrome (TOS) is not well established. Although it is generally accepted that TOS is caused by compression of brachial plexus elements or subclavian vessels in their passage from the cervical area toward the axilla and proximal upper arm, there is much disagreement among clinicians regarding its diagnostic criteria and optimal treatment. Because there is no objective confirmatory test for TOS, the true prevalence of the disease remains elusive. Reported prevalence ranges from 3 to 80 cases/1000 population.⁷ TOS is mostly considered a diagnosis of exclusion.

It is estimated that vascular injuries to the upper extremity represent approximately 30% to 50% of all peripheral vascular injuries. Usually, the brachial artery is involved and most injuries are caused by penetrating trauma.⁸ Blunt injuries such as motor vehicle accidents account for 6% to 10% of upper extremity vascular trauma and are often associated with musculoskeletal injuries and neural injuries.⁹ The functional impact of the trauma is often related to concomitant injury to peripheral nerves. The extent of the vascular compromise following radiation therapy is directly proportional to the amount of radiation given, but symptoms may present only decades after therapy.

Cause and Pathophysiology

Atherosclerosis is considered to be a chronic inflammatory disease of the large arteries.¹⁰ The disease starts at an early age and remains clinically silent for decades. For a detailed discussion of the pathophysiology of atherosclerosis, see Chapters 51 and 88. It is important to note that imaging of the vascular lumen alone may underestimate the burden of disease related to atherosclerosis.

Takayasu arteritis is a classic vasculitis of unknown cause involving the upper extremity arteries. Infection, in particular tuberculosis, has been implicated in the pathogenesis of Takayasu arteritis, but a definitive link between the two diseases remains elusive at present.³^,¹¹ The disease can be divided into two stages, with an acute period of large vessel vasculitis, followed by fibrosis and scarring. In the acute stage, the adventitial vessels of the arterial walls become inflamed as a result of unknown causes. This leads to a generalized, smooth, circumferential thickening of the affected segment, including the media. In the chronic stage, elastic tissue is replaced by fibrosis, with thickening of all three layers of the vessel wall, leading to irreversible segmental smooth luminal narrowing. Other vasculitides that affect the upper extremities are thought to be of similar pathogenesis, although the clinical manifestations may vary (see earlier).

Cervicoaxillary compression syndrome can be the result of a heterogeneous set of activities or trauma, as noted. The exact clinical symptoms depend on which anatomic structures are involved. Local vascular injury is often typified by intimal damage, with subsequent aneurysm formation. This, in turn, may lead to mural thrombus and potentially distal embolization.

Manifestations of Disease

Clinical Presentation

The most common presentations of chronic large vessel upper extremity occlusive disease are arm claudication, or steal phenomena. Clinical clues are helpful to elucidate the underlying disease process and a thorough medical, surgical, occupational and sports history should be obtained in every patient. Symptoms of upper extremity occlusive disease that suggest nonatherosclerotic causes are young age, long-standing fatigue and malaise, high erythrocyte sedimentation rate, and vigorous occupational or sports activities involving repetitive strain to the shoulder and hand, such as frequent baseball pitching, mountain biking, and using the hand to pound structures (e.g., carpenters). Patients with vasculitis typically report having had vague complaints for months or even years prior to consulting a physician. A possible explanation for the relative rarity of arm claudication symptoms is the reduced muscle mass, less vigorous use, and abundance of numerous and well-developed collateral pathways compared with the lower extremity.¹²

Patients with steal syndromes present with upper extremity weakness, dizziness, and sometimes angina. The most well-known steal syndrome is subclavian steal, or reversal of antegrade flow in the vertebral artery caused by the presence of ipsilateral significant subclavian artery stenosis or occlusion, proximal to the origin of the vertebral artery. Another well-known steal phenomenon can be seen in the coronary artery circulation after coronary artery bypass grafting using the internal thoracic artery. In the presence of a subclavian artery stenosis, flow may reverse in the internal thoracic artery to supply the upper extremity arterial bed instead of augmenting flow in the coronary arteries. It is important to realize that an angiographic steal phenomenon does not necessarily imply symptoms. In fact, only about one third of all patients with angiographically proven steal syndromes suffer from characteristic complaints.¹³^–¹⁵

Acute injuries to the upper extremity often involve vascular structures and should be managed according to the presumed cause. In many cases, conventional angiography is the diagnostic modality of first choice because it allows for immediate intervention. This is also the case with suspected arterial embolism, for which catheter-based therapies can be used to perform thrombosuction and delivery of clot-lysing agents.

Imaging Indications and Algorithm

The noninvasive nature of Doppler ultrasonography (DUS), magnetic resonance imaging (MRI), and computed tomography (CT) has lowered the threshold for ordering imaging tests in patients with suspected upper extremity vascular involvement. Apart from the arguments in favor of safety and patient comfort, there is another major reason to use modern cross-sectional imaging techniques. DUS, CT, and MRI not only enable visualization of the arterial lumen but also of the arterial wall and surrounding bony and soft tissue structures. Because of this capability, DUS, MRI, and CT can identify lesions amenable to percutaneous transluminal angioplasty (PTA) and surgery, and can inform the surgeon about the best surgical approach.

When a patient presents with clinical symptoms suggestive of vascular involvement in the arteries of the upper arm, forearm, or hand, it is important to evaluate the entire upper extremity vascular tree from the aortic root to the digital arteries so as not to miss relevant lesions in the vascular tree. Suspected peripheral arterial or venous thrombosis is often evaluated with ultrasonography as the first-line imaging modality because it is a rapid, reliable, and less expensive imaging test, with high sensitivity and specificity. In cases of suspected arterial or venous lesions in the chest itself or in the parts of vessels that pass underneath the clavicle, CT and MRI are preferred, because the visualization of vascular structures in these locations is often poor with DUS. The choice of whether to use CT or MRI largely depends on local skill and preference. Both imaging modalities are capable of high-fidelity depiction of the vascular lumen and wall, as well as of the surrounding structures.

For diagnostic purposes, intra-arterial digital subtraction angiography (IA-DSA) has been relegated to a secondary role because the risks associated with the procedure outweigh the benefits for most patients. An exception is the evaluation of patients with suspected arterial thrombosis or embolization. These patients are vascular emergencies that should be treated without unnecessary delay. IA-DSA is the modality of first choice for this condition because it allows for an unequivocal diagnosis and concomitant treatment, if needed.

MEDIUM AND SMALL VESSEL DISEASE OF THE UPPER EXTREMITY

Atherosclerotic lesions in the forearm and hand arteries are rarely the cause of ischemic symptoms. Other diseases predominate in the list of differential diagnoses when distal upper extremity vascular disease is suspected.

The prototypical disease affecting the medium-sized arteries (and veins) of the upper limb is thromboangiitis obliterans, or Buerger disease (or Winiwarter-Buerger’s disease). Although the lower extremity is involved far more often, Buerger disease may affect the radial and ulnar arteries and palmar arch. There are numerous other diseases that affect the distal forearm, hand, and digital arteries of the upper extremity. A full review of all conditions associated with distal upper extremity arterial disease is beyond the scope of this chapter but can be found in the excellent review by Greenfield and colleagues.¹⁶ In many patients, arterial disease of the distal forearm and hand is not isolated but is associated with underlying systemic connective tissue disease such as scleroderma and CREST syndrome (calcinosis cutis, Raynaud syndrome, esophageal motility disorder, sclerodactyly, and telangiectasia) or rheumatologic disorders such as rheumatoid arthritis, mixed connective tissue disease, systemic lupus erythematosus, antiphospholipid syndrome, polymyositis, and dermatomyositis.¹⁷^–¹⁹

Occupational, recreational, and iatrogenic trauma are important sources of distal upper extremity ischemic symptoms. Repetitive pounding with the ulnar side of the hand or fist may result in aneurysm formation and digital artery occlusion. This condition is known as hypothenar hammer syndrome. A similar complex of symptoms can sometimes be encountered in patients with a history of long-standing pneumatic tool use or in mountain bikers, baseball catchers, volleyball players, or practitioners of karate. Arterial occlusion may also be a consequence of traumatic catheterization of the radial or ulnar arteries.

Raynaud phenomenon is a common ancillary finding in patients suffering from upper extremity vascular disease and may be the presenting symptom. It is defined as a reversible spasm of the small and medium-sized arteries, resulting in a characteristic triphasic white-blue-red color response. First, cessation of digital artery flow produces well-demarcated finger pallor. This is followed by vasorelaxation and return of arterial flow and subsequent postcapillary venule constriction, resulting in desaturated blood and producing cyanosis. Finally, postischemic hyperemia replaces cyanosis with rubor.^16,^20,²¹ A distinction is made between primary Raynaud phenomenon (formerly Raynaud disease), if there is no underlying illness, and secondary Raynaud phenomenon (formerly Raynaud syndrome) if there is an associated disorder detected on assessment. In approximately one third of cases, Raynaud phenomenon is an isolated and benign condition not associated with underlying disease. In cases of inflammatory arteritis, Raynaud phenomenon is common.

Prevalence and Epidemiology

Atherosclerotic occlusive disease of the medium and small arteries of the upper extremity is uncommon and comprises a minority of patients presenting with symptoms of forearm and hand ischemia. The exact prevalence is unknown, because many patients may never come to medical attention.

The incidence of Buerger disease is estimated at 8 to 12.6/100,000.²² Patients with Buerger disease are almost always young (younger than 45 years), use large amounts of tobacco, and characteristically show segmental occlusions in the radial, ulnar, palmar, and digital arteries, with typical bridging corkscrew collaterals. The disease is increasingly seen in women, commensurate with the increase in the proportion of female smokers.

Small vessel disease of the upper extremity is relatively common, especially as manifested as Raynaud disease and in the presence of systemic connective tissue disease. For example, over 90% of patients with scleroderma exhibit Raynaud-like symptoms (see later).

Hypothenar hammer syndrome (HHS) is an infrequent condition and its true prevalence is not known. Marie and associates ²³ have found HHS to be the cause of symptoms in 47 of 4148 patients (1.1%) referred for evaluation of Raynaud phenomenon. Serious complications, defined as requiring surgical intervention, caused by iatrogenic injury of the upper extremity arteries are also relatively rare. Myers and coworkers²⁴ have reported 11 patients over 4 years, whereas Deguara and colleagues²⁵ have reported 6 patients over 20 years. The incidence of serious iatrogenic upper extremity injury depends largely on the case mix of patients seen in the hospital and on the types of procedures performed.

Raynaud’s complex of symptoms is very common. Various studies that have been conducted in the general population in several different countries found the prevalence to range from 3% to 6% up to 30%. In these studies, between 70% and 90% of all reported patients were women. In a large United States registry of 1137 patients presenting with Raynaud, 356 (31.3%) suffered from pure vasospasm with no associated disease, 391 patients (34.4%) had associated connective tissue disease, and 389 patients (34.3%) suffered from other underlying diseases.²⁶

Etiology and Pathophysiology

For a detailed discussion of the pathophysiology of atherosclerosis, see Chapters 51 and 88.

Although the cause of Buerger disease is not known, there is a strong association between the use of tobacco and Buerger disease. Most patients are heavy smokers, but Buerger disease has also been reported in users of smokeless tobacco such as chewing tobacco and snuff. Tobacco use plays a central role in the pathogenesis, initiation, and continuation of the disease and is an absolute requirement for diagnosis. Buerger disease is characterized pathologically by highly cellular thrombus with relative sparing of the blood vessel walls. Multinucleated giant cells can even be observed within the clot in Buerger disease.

Involvement of the small arteries of the upper extremity is frequently encountered in rheumatic diseases. Szekanecz and Koch ²⁷ have recently reviewed the vascular biology underlying this process. Vascular injury is caused primarily by activated neutrophils and inflammatory mediators released by these cells. Rheumatic diseases are associated with accelerated atherosclerosis and increased cardiovascular morbidity and mortality.

Repetitive occupational or recreational trauma may damage the ulnar artery when it enters the hand through Guyon’s canal. The type of arterial abnormality often depends on the nature of the damage to the vessel. Intimal damage favors thrombotic occlusion, whereas injury to the media favors palmar aneurysms.²⁸^,²⁹ Thrombosis and aneurysm are common features seen angiographically with HHS.³⁰

In primary Raynaud phenomenon, patients have an abnormally strong vasospastic response to cold or emotional stimuli, with anatomically normal arteries. Primary Raynaud typically occurs in young women, is bilateral and not associated with ischemic ulcerations, has a benign course, and requires only symptomatic treatment. Secondary Raynaud is suggested by the following findings: an age of onset older than 30 years; episodes that are intense, painful, asymmetrical, or associated with skin lesions; clinical features suggestive of a connective tissue disease (e.g. arthritis and abnormal lung function); specific autoantibodies and evidence of microvascular disease on microscopy of nail fold capillaries.^21,^31,³²

Manifestations of Disease

Clinical Presentation

Atherosclerosis of the distal upper extremity, although relatively rare, typically presents with classic symptoms of ischemia. Patients suffering from Buerger disease are mostly young tobacco smokers who present with complaints of distal extremity ischemia such as claudication and secondary Raynaud phenomenon of the hand, ischemic ulcers, or gangrene of the fingertips. The prevalence of disease has declined in the West over the last 30 years, which can be attributed to the decline in smoking. The disease is more prevalent in areas with a high proportion of smokers such as the Mediterranean, Middle East, and Asia. Because of the proclivity to involve more than one limb, arteriography of the upper and lower extremities should be performed in patients who present clinically with involvement of only one limb. It is common to see angiographic abnormalities consistent with Buerger disease in limbs that are not yet clinically involved.

Raynaud phenomenon is the classic presenting symptom of small vessel disease of the hand. As noted, Raynaud phenomenon is not specific, because it is associated with a variety of conditions. As is the case with large vessel disease of the upper extremity, a thorough medical and surgical history should be obtained in every patient and will provide additional clues about the underlying disease. Occupational and recreational trauma to the small distal vessels of the hand may also present with Raynaud phenomenon.

Traumatic injury can also involve small and medium-sized vessels. Occupational exposure can lead to vibration or impact-induced small vessel vasospasm in the hand, followed by intimal injury, aneurysm formation, thrombosis, occlusion, and/or distal embolization. Blunt and penetrating hand trauma can lead to ischemia if the palmar arch is incomplete.

Imaging Indications and Algorithm

Imaging of the distal forearm and hand arteries is usually performed with CT angiography or MR angiography, or most often with IA-DSA. The latter modality remains the gold standard for depiction of the small vessels of the palmar arch and the digits. However, because of progressively better noninvasive imaging, such as 64-row (or more) multidetector computed CT angiography, or high spatial resolution (blood pool) contrast-enhanced MR angiography catheter angiography may not always be necessary. Although duplex ultrasonography allows real-time evaluation of arterial patency, interobserver variability limits its use to highly specialized centers with dedicated and experienced technicians.

In general, indications for imaging of the distal forearm and hand vessels may include arterial mapping prior to plastic surgery or radial or ulnar artery bypass grafting, HHS, suspected emboli from cardiac disease or atherosclerotic stenoses, or aneurysms in the subclavian artery, Raynaud syndrome, Buerger disease, scleroderma, rheumatoid arthritis, vasculitis, and repetitive trauma. Another indication is the presurgical evaluation of soft tissue tumors of the hand and fingers. Both CT and MR angiography can be combined with additional cross-sectional imaging to evaluate the surrounding soft tissue and bony structures. Raynaud syndrome or suspected distal emboli are particularly good indications for noninvasive vascular imaging techniques such as CTA and MRA; IA-DSA is generally not preferred because of the risk for embolic complications. In a small minority of patients suffering from Buerger disease, the disorder is exclusively located in the upper extremity; thus, when the disease is suspected, the lower extremities should be imaged as well.

Imaging Techniques and Findings

Radiography

When there is clinical suspicion of proximal upper extremity arterial disease, conventional radiographs of the thoracic outlet should be ordered. This will allow identification of supernumerary ribs, elongated transverse processes, or excessive callus formation in close proximity to vascular structures (Fig. 117-1). In patients with upper extremity trauma, conventional radiographs enable identification of fracture sites and the subsequent apposition of bone fragments and presence of radiopaque foreign material.

FIGURE 117-1 Conventional x-ray of the lower cervical and upper thoracic spine showing bilateral cervical ribs (asterisks) in a 29-year-old woman with long-standing complaints of numbness and tingling in both arms.

Ultrasound

Ultrasonography is a powerful first-line screening technique for evaluation of extrathoracic upper extremity arteries and veins. In contrast to the central large arteries and veins close to the heart or underneath the clavicle, the arteries of the upper extremity are easily accessible for ultrasonographic evaluation. There are enough imaging windows available so that the transducer can be placed over the artery of interest, without the presence of overlying bone. High-frequency transducers (more than 5 MHz) can normally be used because arteries and veins lie close to the skin, usually at a depth of several centimeters at most. Gray-scale imaging is useful for evaluating vascular diameter and the presence of atherosclerotic plaque or thrombotic material. Color Doppler flow imaging enables characterization of blood flow patterns and vascular patency. Because it is a noninvasive technique, ultrasonography is well suited for serial examinations. Arteries and veins can be evaluated reliably with ultrasonography from the axillary artery down to the distal radial and ulnar arteries, as well as the palmar arch and smaller digital branches. The normal flow pattern is triphasic. Expert ultrasonographers may be able to evaluate the subclavian artery for the presence of wall thickening associated with GCA or the presence of aneurysm formation and mural thrombus in patients with suspected TOS (Fig. 117-2).

FIGURE 117-2 Upper extremity deep venous thrombosis in 29-year-old male patient with recurrent non-Hodgkin lymphoma presenting with upper extremity swelling. Over the course of almost the entire left upper extremity, the radial and brachial veins could not be compressed at ultrasonography. A, Note the irregular shape of the brachial vein (arrowheads). B, There was normal flow in the brachial artery and thrombus material was in both accompanying veins (arrow and arrowhead).

A particularly powerful application of color Doppler ultrasonography is the evaluation of forearm arteries with regard to suitability for coronary artery bypass grafting as well as suspected pseudoaneurysms. Blood flow signals within a mass contiguous to an artery suggest the diagnosis of pseudoaneurysm, which is a complication that sometimes develops following arterial catheterization or penetrating trauma (Fig. 117-3). With an iatrogenic pseudoaneurysm of a native artery (e.g., after catheterization, unsuccessful arterial puncture, or placement or removal of indwelling arterial catheters), there is usually a small-diameter channel communicating with a larger contained collection of (partially thrombosed) blood. Color Doppler imaging shows blood flow signals and the pseudoaneurysm cavity. A jet and/or swirling motion or color yin yang sign is typically seen within the collection itself.³³ Color DUS is also well suited for the emergency evaluation of the upper extremity arteries in cases of suspected acute arterial embolus—for example, in patients with atrial fibrillation.

FIGURE 117-3 Color Doppler ultrasonography in 55-year-old male patient presenting with a hypoechoic pulsatile mass in the left upper extremity after removal of an indwelling arterial catheter. Color Doppler analysis reveals a characteristic jet of blood directed into the false aneurysm (arrow; arrowheads demarcate the boundaries of the aneurysm). Thr, thrombus material.

Computed Tomography

The main strength of cross-sectional imaging modalities such as CT and MRI is that the central thoracic vessels, which are often involved in upper extremity arterial disease, are much better accessible compared with color DUS. The resolution of current equipment allows high spatial resolution depiction of the arterial lumen and arterial wall. The capability for rapid image acquisition over a large field of view further increases the attractiveness of these techniques.

In general, three different CT angiography (CTA) protocols can be distinguished. For evaluation of the central thoracic vessels, one should use an aortic arch or proximal upper extremity protocol. For imaging the distal forearm and hands, a distal upper extremity runoff protocol should be used. Distinguishing these two indications allows for increased spatial resolution for imaging the distal arteries, which allows better depiction of subtle abnormalities such as those seen in small palmar and digital vessels. Upper extremity venous structures are usually imaged using indirect venographic protocols. Indirect imaging refers to the acquisition of a late-phase dataset after the injection of contrast medium (i.e., after the initial arterial first pass of contrast bolus) to avoid streak artifacts caused by undiluted iodinated contrast agents in the first pass. Delayed acquisitions may be useful in the setting of suspected vasculitis, vascular masses, and hemorrhage.

Properly executed, CTA allows recognition of arterial stenoses (Fig. 117-4) and aneurysm formation (Fig. 117-5) as seen in atherosclerosis, and the typical circumferential wall thickening as seen in vasculitis. An added benefit of CT over MRI is the improved ability to recognize and display bony abnormalities. However, in most cases, these have already been detected with conventional radiography, which remains the first-line imaging study in patients with upper extremity complaints. With the current generation of 64-detector row CT scanners, care should be taken not to outrun the arrival of the contrast bolus—because incomplete vascular filling may erroneously suggest embolic occlusion of the vessel—as a result of the extremely fast acquisition speeds of these machines. Submillimeter collimation, a low pitch, and slower gantry speed are options to avoid this problem. Arterial embolism is usually characterized by an acute filling defect in the affected vessel, and is sometimes accompanied by increased density of contrast medium proximal to the occlusion, which often shows a typical meniscus sign.

FIGURE 117-4 Curved multiplanar reformation of 64-slice multidetector (MD) CT examination in a 67-year-old male patient with upper extremity intermittent claudication. There is a relatively short stenosis in the proximal left subclavian artery (arrow). Note the jagged appearance of the lesion. Also, there is no vessel wall thickening, suggesting that this lesion is of atherosclerotic origin.

FIGURE 117-5 Curved multiplanar reformation of 64-slice MDCT examination in a 60-year old male patient presenting with acute chest pain. There is a giant aneurysm in the aberrant right subclavian artery. AL, arteria lusoria; L, arterial lumen; T, thrombus.

When imaging the distal upper extremity, best image quality is achieved with the patient in the supine position, with the forearm and hand raised above the head. In patients with Buerger disease, arterial (and sometimes venous) occlusion can be seen, with typical bridging corkscrew collaterals that reconstitute distal flow. Key findings in small vessel disease are generally diminished enhancement in the radial, ulnar, and interosseous arteries and poor enhancement of the palmar and digital arteries in the hand (Fig. 117-6). Sometimes, narrowing and tapering of digital vessels can be seen.

FIGURE 117-6 Color volume rendering of the distal upper extremity and hand arteries in a 75-year-old male patient presenting with intermittent claudication of the upper extremity. Image shows poor filling of the ulnar artery with an occlusion of the part of the ulnar artery (U) at the level of the wrist that connects to the palmar arch (arrowhead). Also note lack of filling of the proper digital arteries of the fingers (asterisks) and kinked radial artery (R).

In cases of suspected trauma, it is important to review the scout images for the presence of foreign material, such as bullets or shrapnel (Fig. 117-7).

FIGURE 117-7 Color volume rendering of 64-slice CTA image of the left upper extremity of a 25-year-old male with a gunshot trauma. There is a comminuted fracture of the ulna (arrowhead). Both the radial (R) and ulnar artery (U) are patent and intact. The ulnar artery is slightly deviated because of soft tissue damage but is also intact and patent. B, bullet with streak artifacts.

Magnetic Resonance Imaging

Because of the wide array of different soft tissue contrasts and angiographic techniques, MRI has become one of the preferred modalities in the work-up of suspected upper extremity arterial disease. Although contrast-enhanced MRA (CE MRA) remains the standard of reference for evaluation of the vasculature, recent developments in nonenhanced pulse sequences for vascular imaging, combined with clinical concerns for potential risks of nephrogenic systemic fibrosis, have rekindled interest in these techniques.

There is a paucity of literature on the efficacy and diagnostic accuracy of nonenhanced techniques, so this section will focus on contrast-enhanced techniques. The limited maximum field of view (FOV) of 40 to 50 cm in commercially available MR scanners necessitates dedicated protocols for the central vessels in the chest and forearm and hand vessels, analogous to the dedicated protocols as described earlier for CT. An important pitfall of MRI is susceptibility-induced pseudostenosis in the subclavian artery ipsilateral to the site where the gadolinium (Gd) chelate contrast medium is injected. Because of the high concentration of Gd in the subclavian vein during the initial intravenous injection, it is possible to encounter signal drop-off (also known as T2* susceptibility artifact), which obscures visualization of the subclavian vein but also of the adjacent subclavian artery (Fig. 117-8). To avoid this artifact, it is necessary to acquire early and late arterial phase images; the signal drop-off will disappear on the later phase images because of the natural reduction in the concentration of Gd over time, with hemodilution of the contrast agent.

FIGURE 117-8 Whole-volume maximum intensity projection (MIP) by proximal upper extremity MRA in a 40-year-old male patient with complaints of bilateral upper extremity claudication. The physical examination was unremarkable and there was no blood pressure difference between both arms. Following a left antecubital venous injection of a Gd chelate contrast agent during CE MRA, the arterial phase MIP image suggests a stenosis in the left subclavian artery (arrow, A), which is confirmed on the accompanying source images (arrow, C). In the late arterial–early venous phase, the stenosis has disappeared on the MIP and source images (arrows, B and D). The stenosis is caused by T2* susceptibility-induced signal loss because of the highly concentrated gadolinium in the left subclavian vein. Note that this vessel exhibits far lower signal intensity compared with the jugular veins in A.

Atherosclerotic lesions present as stenoses or occlusions in the aortic arch and brachial vessels over a relative short length and can be recognized by their typical serrated or jagged appearance (Fig. 117-9). This is opposed to the smooth, longer segmented stenoses with concomitant circumferential arterial wall thickening, which may be seen with vasculitis (i.e., arteritis). In cases of stenoses in one of the arch vessels, it is useful to supplement the MRI examination with phase contrast imaging of the cervical vessels to detect the presence of retrograde flow, or steal, in the vertebral artery.

FIGURE 117-9 Whole-volume maximum intensity projection of proximal upper extremity MRA in 61-year-old male patient with complaints of bilateral upper extremity claudication. A, There is a short high-grade stenosis in the proximal left subclavian artery (arrow) and low-grade narrowing of the aberrant right subclavian artery. Note the serrated appearance of the lesion (asterisks in A and B). The absence of vessel wall thickening suggests that this lesion is of atherosclerotic origin.

Bilateral symmetrical smooth stenoses in the subclavian arteries are highly suggestive of GCA (Fig. 117-10). In patients with clinically suspected temporal arteritis, it is also useful to evaluate the superficial temporal artery with a dedicated high spatial resolution imaging protocol. The degree of arterial wall enhancement in this vessel has been found to correlate well with the amount of inflammatory activity at histology. Conversely, a return to lower degrees of enhancement and normal wall thickness detected by MRI after the institution of therapy reliably signifies a reduction of clinical disease activity.³⁴^,³⁵

FIGURE 117-10 Whole-volume maximum intensity projection of the aortic arch and branch vessels in a 67-year-old female patient with histologically proven giant cell arteritis. Note bilateral high-grade smooth subclavian artery stenoses (arrows). This finding is highly suggestive of arterial involvement caused by caused by giant cell arteritis.

(Courtesy of Dr. Thorsten Bley, Klinik und Poliklinik für Diagnostische und Interventionelle Radiologie, Universitätsklinkum Hamburg-Eppendorf, Hamburg, Germany.)

Aneurysmal widening of the subclavian artery can be seen in vasculitis but is more often encountered in patients with TOS. It is important to identify the presence of luminal thrombus in the artery, because this may pose a risk for distal embolization. It is often useful to image patients in the neutral anatomic position and with the arm(s) elevated above the head to assess the effect of postural changes on vascular patency (Fig. 117-11). Sagittal T1- and T2-weighted images in the neutral and elevated positions may also be of use to identify nonosseous compression of vascular structures such as fibrous bands. In patients with Buerger disease, arterial (and sometimes venous) occlusion can be seen, with typical bridging corkscrew collaterals (see later, “Angiography”).

FIGURE 117-11 Whole-volume maximum intensity projection (A) and corresponding source image (B) of proximal upper extremities in 57-year-old female patient with complaints of pain in the left shoulder and proximal upper extremity when lifting her arm above her head. The referring clinician wanted to rule out thoracic outlet syndrome. First-pass images were acquired in the anatomic position. Subsequent steady-state images were acquired in the anatomic position (C) and with the arms elevated above the head (E). There is a short 70% stenosis in the proximal left subclavian artery (arrows). Curved multiplanar reformations of the left subclavian artery reveal the stenosis in the proximal part (asterisks in D and F), but no compression or aneurysm formation was seen of the subclavicular portion of the subclavian artery. Gadofosveset, 10 mL, was used for the examination.

As is the case with CT, the best image quality is achieved with the patient in the supine position, with the forearm and hand raised above the head when imaging the distal upper extremity. Key findings in small vessel disease are slow and generally diminished enhancement of the forearm arteries and poor enhancement of the palmar and digital arteries in the hand (Fig. 117-12). The ability to perform time-resolved MR imaging is particularly helpful in this regard because it can readily demonstrate differential filling between both upper extremities or globally slowed arterial opacification. The introduction of the blood pool agent gadofosveset trisodium (Lantheus Medical Imaging; North Billerica, Mass) has facilitated ultrahigh spatial resolution equilibrium phase imaging of the vascular system in the hand and fingers, with voxel sizes as small as 64 µm. Narrowing and tapering of digital vessels can easily be appreciated on these images (Fig. 117-13).

FIGURE 117-12 Time-resolved MR angiogram with subsequent steady-state acquisition in 47-year-old female patient with long-standing antiphospholipid syndrome. The patient presented with a cold hand that would not resolve. A, Four subsequent arterial phase images show very slow filling of the distal forearm and hand arteries. Note the absence of opacification of the digital arteries. B, Images acquired in the steady state (after distribution of contrast material in both the arterial and venous systems) show two digital arteries (arrows) in the proximal part of the hand (left) as well as the fingers (right). C, Intra-arterial digital subtraction angiography (DSA) was performed to ensure that MRA did not miss any arteries. As can be seen, even with vasodilation, DSA was not able to show any digital arteries, most likely because of the extremely slow flow in combination with the higher viscosity of the iodinated contrast agent. i, interosseous artery; r, radial artery; u, ulnar artery.

FIGURE 117-13 Whole-volume maximum intensity projection in 63-year-old female patient with gangrenous fingertips caused by steal after dialysis access creation in the proximal forearm. There is an almost complete lack of digital vessels, as well as a short occlusion of the palmar arch. Images were acquired in the steady state with an isotropic resolution of 0.4 × 0.4 × 0.4 mm³ (64 mµ) voxel size.

MRI is not the preferred modality in cases of trauma. Patients are best imaged with CT or IA-DSA in these cases.

Nuclear Medicine and Positron Emission Tomography

The introduction of scanners capable of combined ¹⁸fluorodeoxyglucose (¹⁸FDG ) positron emission tomography (PET) and CT imaging is potentially attractive for imaging inflammatory large vessel disease. Although no large-scale studies have been performed to date, there is anecdotal evidence that the combination of CT with PET (PET-CT) is of use for the evaluation of patients with large vessel vasculitis. A recent study by Henes and associates ³⁶ in 13 patients who were newly diagnosed or re-evaluated for large vessel vasculitis has found that PET-CT could provide additional information over conventional serologic markers, such as erythrocyte sedimentation rate and C-reactive protein levels in blood. Stenotic lesions at CT were found in only 8 of 13 patients, whereas all patients with clinically active disease (N = 12) demonstrated uptake of ¹⁸FDG in the aortic arch and branch vessels, indicating that PET imaging may be more sensitive in the early phases of the disease, when angiographic evaluation does not yet show luminal abnormalities (Fig. 117-14). Whether nuclear medicine techniques will still be used in the future remains to be determined because of the very high radiation doses involved (10 to 20 mSv/examination). No large comparative studies between MRI and PET-CT have been published so it is unclear to what extent these imaging modalities are complementary. Because of the high radiation burden and because many patients with vasculitis are young women, PET-CT is not a very attractive technique for repetitive imaging, as is often needed in the follow-up of vasculitis. In the foreseeable future, MRI remains the modality of first choice for these patients.

FIGURE 117-14 Whole-body PET-CT studies showing CT findings (upper left panels), PET findings (lower panels), and fused axial PET-CT images (upper right panels) at the upper chest level in three patients with minor (A), moderate (B), and extensive (C) vasculitis involving the subclavian arteries. A, The patient with minor disease was a 69-year-old woman suffering from weight loss, polymyalgia, and inadequate response to steroids. There is moderately increased uptake of ¹⁸FDG in the left subclavian artery (arrow). B, The patient with moderate disease was a 75-year-old man with initial complaints of polymyalgia, fever, visual impairment, jaw claudication, and inadequate response to steroid therapy as well. The CT, PET, and fusion images show mild thickening of both subclavian artery walls, with corresponding increased ¹⁸FDG uptake (arrowheads). C, The patient with extensive disease presented with fever, weight loss, arm claudication, and pulselessness of the left arm. There is extensive patchy arterial wall thickening with corresponding increased uptake of ¹⁸FDG in the aortic arch and branch vessels (arrowheads). Also note the strong vascular wall enhancement throughout the entire peripheral vascular tree in the lower right image.

(Courtesy of Dr. Christina Pfannenberg and Dr. Jörg Henes, Erberhard Karls University Hospital, Tübingen, Germany.)

Angiography

Although CTA and MRA have largely overtaken DSA for the evaluation of the central thoracic arteries and veins, IA-DSA with the administration of vasodilators remains the standard for evaluation of digital arteries in most centers because of its unparalleled spatial and temporal resolution (Fig. 117-15). The major drawback, however, is the invasiveness and discomfort of the procedure, especially when vasodilators are used. Typical findings with regard to atherosclerotic or aneurysmal arterial disease, as well as findings suggestive of vasculitis or Buerger disease, are identical to those described earlier for CTA and MRA (Fig. 117-16). A limitation of IA-DSA is its inability to image the vessel wall. In clinical practice, IA-DSA of the central vessels is primarily performed in the context of endovascular treatment.