The U.S. Preventive Services Task Force (USPSTF) recommends against screening for carotid artery stenosis in those without symptoms.

Vessel restenosis is typically detected by angiography, but can also be detected by duplex ultrasound and other imaging techniques.

Carotid stenosis is usually diagnosed by color flow duplex ultrasound scan of the carotid arteries in the neck. This involves no radiation, no needles and no contrast agents that may cause allergic reactions. This test has moderate sensitivity and specificity, and yields many false-positive results.

Typically duplex ultrasound scan is the only investigation required for decision making in carotid stenosis as it is widely available and rapidly performed. However, further imaging can be required if the stenosis is not near the bifurcation of the carotid artery.

One of several different imaging modalities, such as angiogram, computed tomography angiogram (CTA) or magnetic resonance imaging angiogram (MRA) may be useful. Each imaging modality has its advantages and disadvantages - Magnetic resonance angiography and CT angiography with contrast is contraindicated in patients with renal insufficiency, catheter angioigraphy has a 0.5% to 1.0% risk of stroke, MI, arterial injury or retoperitoneal bleeding. The investigation chosen will depend on the clinical question and the imaging expertise, experience and equipment available.

In peripheral procedures, rates are still high. A 2003 study of selective and systematic stenting for limb-threatening ischemia reported restenosis rates at 1 year follow-up in 32.3% of selective stenting patients and 34.7% of systematic stenting patients.

The 2006 SIROCCO trial compared the sirolimus drug-eluting stent with a bare nitinol stent for atherosclerotic lesions of the superficial femoral artery, reporting restenosis at 2 year follow-up was 22.9% and 21.1%, respectively.

A 2009 study compared bare nitinol stents with percutaneous transluminal angioplasty (PTA) in superficial femoral artery disease. At 1 year follow-up, restenosis was reported in 34.4% of stented patients versus 61.1% of PTA patients.

A chest X-ray can also assist in the diagnosis and provide clues as to the severity of the disease, showing the degree of calcification of the valve, and in a chronic condition, an enlarged left ventricle and atrium.

Cardiac chamber catheterization provides a definitive diagnosis, indicating severe stenosis in valve area of <1.0 cm (normally about 3 cm). It can directly measure the pressure on both sides of the aortic valve. The pressure gradient may be used as a decision point for treatment. It is useful in symptomatic people before surgery. The standard for diagnosis of aortic stenosis is noninvasive testing with echocardiography. Cardiac catheterization is reserved for cases in which there is discrepancy between the clinical picture and non-invasive testing, due to risks inherent to crossing the aortic valve such as stroke.

In developed countries, with improved public health, infection control and increasing life spans, atheroma processes have become an increasingly important problem and burden for society.

Atheromata continue to be the primary underlying basis for disability and death, despite a trend for gradual improvement since the early 1960s (adjusted for patient age). Thus, increasing efforts towards better understanding, treating and preventing the problem are continuing to evolve.

According to United States data, 2004, for about 65% of men and 47% of women, the first symptom of cardiovascular disease is myocardial infarction (heart attack) or sudden death (death within one hour of symptom onset).

A significant proportion of artery flow-disrupting events occur at locations with less than 50% lumenal narrowing. Cardiac stress testing, traditionally the most commonly performed noninvasive testing method for blood flow limitations, generally only detects lumen narrowing of ~75% or greater, although some physicians advocate nuclear stress methods that can sometimes detect as little as 50%.

The sudden nature of the complications of pre-existing atheroma, vulnerable plaque (non-occlusive or soft plaque), have led, since the 1950s, to the development of intensive care units and complex medical and surgical interventions. Angiography and later cardiac stress testing was begun to either visualize or indirectly detect stenosis. Next came bypass surgery, to plumb transplanted veins, sometimes arteries, around the stenoses and more recently angioplasty, now including stents, most recently drug coated stents, to stretch the stenoses more open.

Yet despite these medical advances, with success in reducing the symptoms of angina and reduced blood flow, atheroma rupture events remain the major problem and still sometimes result in sudden disability and death despite even the most rapid, massive and skilled medical and surgical intervention available anywhere today. According to some clinical trials, bypass surgery and angioplasty procedures have had at best a minimal effect, if any, on improving overall survival. Typically mortality of bypass operations is between 1 and 4%, of angioplasty between 1 and 1.5%.

Additionally, these vascular interventions are often done only after an individual is symptomatic, often already partially disabled, as a result of the disease. It is also clear that both angioplasty and bypass interventions do not prevent future heart attack.

The older methods for understanding atheroma, dating to before World War II, relied on autopsy data. Autopsy data has long shown initiation of fatty streaks in later childhood with slow asymptomatic progression over decades.

One way to see atheroma is the very invasive and costly IVUS ultrasound technology; it gives us the precise volume of the inside intima plus the central media layers of about of artery length. Unfortunately, it gives no information about the structural strength of the artery. Angiography does not visualize atheroma; it only makes the blood flow within blood vessels visible. Alternative methods that are non or less physically invasive and less expensive per individual test have been used and are continuing to be developed, such as those using computed tomography (CT; led by the electron beam tomography form, given its greater speed) and magnetic resonance imaging (MRI). The most promising since the early 1990s has been EBT, detecting calcification within the atheroma before most individuals start having clinically recognized symptoms and debility. Interestingly, statin therapy (to lower cholesterol) does not slow the speed of calcification as determined by CT scan. MRI coronary vessel wall imaging, although currently limited to research studies, has demonstrated the ability to detect vessel wall thickening in asymptomatic high risk individuals. As a non-invasive, ionising radiation free technique, MRI based techniques could have future uses in monitoring disease progression and regression. Most visualization techniques are used in research, they are not widely available to most patients, have significant technical limitations, have not been widely accepted and generally are not covered by medical insurance carriers.

From human clinical trials, it has become increasingly evident that a more effective focus of treatment is slowing, stopping and even partially reversing the atheroma growth process. There are several prospective epidemiologic studies including the Atherosclerosis Risk in Communities (ARIC) Study and the Cardiovascular Health Study (CHS), which have supported a direct correlation of Carotid Intima-media thickness (CIMT) with myocardial infarction and stroke risk in patients without cardiovascular disease history. The ARIC Study was conducted in 15,792 individuals between 5 and 65 years of age in four different regions of the US between 1987 and 1989. The baseline CIMT was measured and measurements were repeated at 4- to 7-year intervals by carotid B mode ultrasonography in this study. An increase in CIMT was correlated with an increased risk for CAD. The CHS was initiated in 1988, and the relationship of CIMT with risk of myocardial infarction and stroke was investigated in 4,476 subjects ≤65 years of age. At the end of approximately six years of follow-up, CIMT measurements were correlated with cardiovascular events.

Paroi artérielle et Risque Cardiovasculaire in Asia Africa/Middle East and Latin America (PARC-AALA) is another important large-scale study, in which 79 centers from countries in Asia, Africa, the Middle East, and Latin America participated, and the distribution of CIMT according to different ethnic groups and its association with the Framingham cardiovascular score was investigated. Multi-linear regression analysis revealed that an increased Framingham cardiovascular score was associated with CIMT, and carotid plaque independent of geographic differences.

Cahn et al. prospectively followed-up 152 patients with coronary artery disease for 6–11 months by carotid artery ultrasonography and noted 22 vascular events (myocardial infarction, transient ischemic attack, stroke, and coronary angioplasty) within this time period. They concluded that carotid atherosclerosis measured by this non-interventional method has prognostic significance in coronary artery patients.

In the Rotterdam Study, Bots et al. followed 7,983 patients >55 years of age for a mean period of 4.6 years, and reported 194 incident myocardial infarctions within this period. CIMT was significantly higher in the myocardial infarction group compared to the other group. Demircan et al. found that the CIMT of patients with acute coronary syndrome were significantly increased compared to patients with stable angina pectoris.

It has been reported in another study that a maximal CIMT value of 0.956 mm had 85.7% sensitivity and 85.1% specificity to predict angiographic CAD. The study group consisted of patients admitted to the cardiology outpatient clinic with symptoms of stable angina pectoris. The study showed CIMT was higher in patients with significant CAD than in patients with non-critical coronary lesions. Regression analysis revealed that thickening of the mean intima-media complex more than 1.0 was predictive of significant CAD our patients. There was incremental significant increase in CIMT with the number coronary vessel involved. In accordance with the literature, it was found that CIMT was significantly higher in the presence of CAD. Furthermore, CIMT was increased as the number of involved vessels increased and the highest CIMT values were noted in patients with left main coronary involvement. However, human clinical trials have been slow to provide clinical & medical evidence, partly because the asymptomatic nature of atheromata make them especially difficult to study. Promising results are found using carotid intima-media thickness scanning (CIMT can be measured by B-mode ultrasonography), B-vitamins that reduce a protein corrosive, homocysteine and that reduce neck carotid artery plaque volume and thickness, and stroke, even in late-stage disease.

Additionally, understanding what drives atheroma development is complex with multiple factors involved, only some of which, such as lipoproteins, more importantly lipoprotein subclass analysis, blood sugar levels and hypertension are best known and researched. More recently, some of the complex immune system patterns that promote, or inhibit, the inherent inflammatory macrophage triggering processes involved in atheroma progression are slowly being better elucidated in animal models of atherosclerosis.

While a single ruptured plaque can be identified during autopsy as the cause of a coronary event, there is currently no way to identify a culprit lesion before it ruptures.

Because artery walls typically enlarge in response to enlarging plaques, these plaques do not usually produce much stenosis of the artery lumen. Therefore, they are not detected by cardiac stress tests or angiography, the tests most commonly performed clinically with the goal of predicting susceptibility to future heart attack. In contrast to conventional angiography, cardiac CT angiography does enable visualization of the vessel wall as well as plaque composition. Some of the CT derived plaque characteristics can help predict for acute coronary syndrome. In addition, because these lesions do not produce significant stenoses, they are typically not considered "critical" and/or interventionable by interventional cardiologists, even though research indicates that they are the more important lesions for producing heart attacks.

The tests most commonly performed clinically with the goal of testing susceptibility to future heart attack include several medical research efforts, starting in the early to mid-1990s, using intravascular ultrasound (IVUS), thermography, near-infrared spectroscopy, careful clinical follow-up, and other methods, to predict these lesions and the individuals most prone to future heart attacks. These efforts remain largely research with no useful clinical methods to date (2006). Furthermore, the usefulness of detecting individual vulnerable plaques by invasive methods has been questioned because many "vulnerable" plaques rupture without any associated symptoms and it remains unclear if the risk of invasive detection methods is outweighed by clinical benefit.

Another approach to detecting and understanding plaque behavior, used in research and by a few clinicians, is to use ultrasound to non-invasively measure wall thickness (usually abbreviated IMT) in portions of larger arteries closest to the skin, such as the carotid or femoral arteries. While stability vs. vulnerability cannot be readily distinguished in this way, quantitative baseline measurements of the thickest portions of the arterial wall (locations with the most plaque accumulation). Documenting the IMT, location of each measurement and plaque size, a basis for tracking and partially verifying the effects of medical treatments on the progression, stability, or potential regression of plaque, within a given individual over time, may be achieved.

Patients can lower their risk for vulnerable plaque rupture in the same ways that they can cut their heart attack risk: Optimize lipoprotein patterns, keep blood glucose levels low normal (see HbA1c), stay slender, eat a proper diet, quit smoking, and maintain a regular exercise program. Researchers also think that obesity and diabetes may be tied to high levels of C-reactive protein.

Because artery walls enlarge at locations with atheroma, detecting atheroma before death and autopsy has long been problematic at best. Most methods have focused on the openings of arteries; highly relevant, yet totally miss the atheroma within artery walls.

Historically, arterial wall fixation, staining and thin section has been the gold standard for detection and description of atheroma, after death and autopsy. With special stains and examination, micro calcifications can be detected, typically within smooth muscle cells of the arterial media near the fatty streaks within a year or two of fatty streaks forming.

Interventional and non-interventional methods to detect atherosclerosis, specifically vulnerable plaque (non-occlusive or soft plaque), are widely used in research and clinical practice today.

Carotid Intima-media thickness Scan (CIMT can be measured by B-mode ultrasonography) measurement has been recommended by the American Heart Association as the most useful method to identify atherosclerosis and may now very well be the gold standard for detection.

IVUS is the current most sensitive method detecting and measuring more advanced atheroma within living individuals, though it is typically not used until decades after atheroma begin forming due to cost and body invasiveness.

CT scans using state of the art higher resolution spiral, or the higher speed EBT, machines have been the most effective method for detecting calcification present in plaque. However, the atheroma have to be advanced enough to have relatively large areas of calcification within them to create large enough regions of ~130 Hounsfield units which a CT scanner's software can recognize as distinct from the other surrounding tissues. Typically, such regions start occurring within the heart arteries about 2–3 decades after atheroma start developing. Hence the detection of much smaller plaques than previously possible is being developed by some companies, such as Image Analysis. The presence of smaller, spotty plaques may actually be more dangerous for progressing to acute myocardial infarction.

Arterial ultrasound, especially of the carotid arteries, with measurement of the thickness of the artery wall, offers a way to partially track the disease progression. As of 2006, the thickness, commonly referred to as IMT for intimal-medial thickness, is not measured clinically though it has been used by some researchers since the mid-1990s to track changes in arterial walls. Traditionally, clinical carotid ultrasounds have only estimated the degree of blood lumen restriction, stenosis, a result of very advanced disease. The National Institute of Health did a five-year $5 million study, headed by medical researcher Kenneth Ouriel, to study intravascular ultrasound techniques regarding atherosclerotic plaque. More progressive clinicians have begun using IMT measurement as a way to quantify and track disease progression or stability within individual patients.

Angiography, since the 1960s, has been the traditional way of evaluating for atheroma. However, angiography is only motion or still images of dye mixed with the blood with the arterial lumen and never show atheroma; the wall of arteries, including atheroma with the arterial wall remain invisible. The limited exception to this rule is that with very advanced atheroma, with extensive calcification within the wall, a halo-like ring of radiodensity can be seen in most older humans, especially when arterial lumens are visualized end-on. On cine-floro, cardiologists and radiologists typically look for these calcification shadows to recognize arteries before they inject any contrast agent during angiograms.

The differentiating presentations are suggestive of FMD being a unique syndrome in respect to the pediatric population. Experienced FMD clinicians warn against relying in the “string of beads” angiography for a diagnosis. In fact, it is suggested that FMD may be both under and over-diagnosed in children with stroke.

It may occur as the result of carotid artery stenosis (though some disagree); however, most carotid bruits, particularly those found in younger or asymptomatic patients, are not related to any disease and are termed "innocent carotid bruits". A carotid bruit is unlikely to be heard if the stenosis occludes less than 40% of the diameter of the artery. Likewise, a stenosis of greater than 90% may not be heard, as the flow may be too low.

Many carotid bruits are discovered incidentally in an otherwise asymptomatic patient. The presence of a carotid bruit alone does not necessarily indicate the presence of stenosis, and the physical examination cannot be used to estimate the degree of stenosis, if present; therefore, any bruit must be evaluated by ultrasound or imaging.

It is the lack of specific symptoms and its potential to appear anywhere that makes FMD a challenge to detect early on. The most accurate diagnosis comes from combining clinical presentation and angiographic imaging. According to the Michigan Outcomes Research and Reporting Program (MCORRP, 2013) the length of time from a patient’s first signs or symptoms to diagnosis is commonly 5 years.

FMD is currently diagnosed through the use of both invasive and non-invasive tests. Non-invasive testing includes duplex ultrasonography, magnetic resonance angiography (MRA), and computed tomographic angiography (CTA). Invasive testing through angiography is the gold standard. However, due to the higher risk of complications this is typically not done early on. Occasionally, FMD is diagnosed asymptomatically after an unrelated x-ray presents the classic ‘string of beads’ appearance of the arteries, or when a practitioner investigates an unexpected bruit found during an exam. When a diagnosis of FMD is considered for a patient thorough medical history, family history as well as vascular examination should be completed.

A definitive diagnosis of FMD can only be made with imaging studies. Catheter-based angiography (with contrast) has proven to be the most accurate imaging technique: this test involves a catheter is inserted into a large artery and advanced until it reaches the vessel of question. The catheter allows practitioners to view and measure the pressure of the artery aiding in the categorization and severity of the FMD diseased artery. According to Olin, “catheter-based angiography is the only imaging modality that can accurately identify the changes of FMD, aneurysm formation, and dissection in the branch vessels.” Practitioners believe it is important to utilize IVUS imaging because stenosis can sometimes only be detected through the methods of pressure gradient or IVUS imaging. In addition, computed tomography angiography and magnetic resonance angiography are commonly used to evaluate arteries in the brain. Doppler ultrasound may be used in both the diagnosis and follow-up of FMD.

70% of patients with carotid arterial dissection are between the ages of 35 and 50, with a mean age of 47 years.

Smith (2015) conducted a study that looked into specific biological markers that correlate to Moyamoya disease. Some of the categories of these biomarkers include phenotypes - conditions commonly related to Moyamoya, radiographical markers for the diagnosis of Moyamoya, and proteins as well as cellular changes that occur in cases of Moyamoya.

Similar to Moyamoya Disease, there are conditions that are closely associated with Moyamoya Syndrome. Some of the more common medical conditions that are closely associated with Moyamoya Syndrome include trisomy 21 (Down's Syndrome), sickle cell disease, and neurofibromatosis type 1. There is also evidence that identifies hyperthyroidism and congenital dwarfing syndromes as two of the more loosely associated syndromes that correlate with the possibility of being diagnosed with Moyamoya Disease later in life.

There is also research that has shown that certain radiographic biomarkers that lead to the diagnosis of Moyamoya Disease have been identified. The specific radiographic markers are now considered an acceptable key component to Moyamoya Disease and have been added to the INternational Classification of Diseases (ICD). These biomarkers of Moyamoya are "stenosis of the distal ICA's up to and including the bifurcation, along with segments of the proximal ACA and MCA...dilated basal collateral vessels must be present" Some other common findings that have not been added to the classification index of those with Moyamoya Disease which are found using radiography involve very distinct changes in the vessels of the brain. These changes include newly formed vessels made to compensate for another change noted, ischemia and cerebrovascular reserve, both found on MRI. Functional changes include evidence of ischemia in vessels of the brain (ICA, ACA, MCA, specifically). It is important to also note that the radiographic biomarkers, in order to be classified as Moyamoya Disease, all findings must be bilateral. If this is not the case and the findings are unilateral, it is diagnosed as Moyamoya Syndrome.

There are also several protein biomarkers that have been linked to the Moyamoya Disease diagnosis. Although the sample size of the studies performed are small due to the rarity of the disease, the findings are indicative of a correlation between the disease and several specific protein biomarkers. Other studies have confirmed the correlation of Moyamoya and adhesion molecule 1 (ICAM-1) being increased as compared to normal vascular function counterparts Furthermore, it has been concluded that the localization of inflammatory cells suggests that the inflammation stimulus iteself may be responsible for the proliferation and occlusion in the ICA, ACA, and MCA found in those with Moyamoya Disease.

Various diagnostic modalities exist to demonstrate blood flow or absence thereof in the vertebral arteries. The gold standard is cerebral angiography (with or without digital subtraction angiography). This involves puncture of a large artery (usually the femoral artery) and advancing an intravascular catheter through the aorta towards the vertebral arteries. At that point, radiocontrast is injected and its downstream flow captured on fluoroscopy (continuous X-ray imaging). The vessel may appear stenotic (narrowed, 41–75%), occluded (blocked, 18–49%), or as an aneurysm (area of dilation, 5–13%). The narrowing may be described as "rat's tail" or "string sign". Cerebral angiography is an invasive procedure, and it requires large volumes of radiocontrast that can cause complications such as kidney damage. Angiography also does not directly demonstrate the blood in the vessel wall, as opposed to more modern modalities. The only remaining use of angiography is when endovascular treatment is contemplated (see below).

More modern methods involve computed tomography (CT angiography) and magnetic resonance imaging (MR angiography). They use smaller amounts of contrast and are not invasive. CT angiography and MR angiography are more or less equivalent when used to diagnose or exclude vertebral artery dissection. CTA has the advantage of showing certain abnormalities earlier, tends to be available outside office hours, and can be performed rapidly. When MR angiography is used, the best results are achieved in the "T" setting using a protocol known as "fat suppression". Doppler ultrasound is less useful as it provides little information about the part of the artery close to the skull base and in the vertebral foramina, and any abnormality detected on ultrasound would still require confirmation with CT or MRI.

A carotid bruit is a systolic sound heard over the carotid artery area during auscultation.

The diagnosis of renal artery stenosis can use many techniques to determine if the condition is present, a clinical prediction rule is available to guide diagnosis.

Among the diagnostic techniques are:

- Doppler ultrasound study of the kidneys

- refractory hypertension

- auscultation (with stethoscope) - bruit ("rushing" sound)

- captopril challenge test

- captopril test dose effect on the differential renal function as measured by MAG3 scan.

- renal artery arteriogram.

The goal of treatment is to prevent the development or continuation of neurologic deficits. Treatments include observation, anticoagulation, stent implantation and carotid artery ligation.

The diagnosis of moyamoya is suggested by CT, MRI, or angiogram results. Contrast-enhanced T1-weighted images are better than FLAIR images for depicting the leptomeningeal ivy sign in moyamoya disease. MRI and MRA should be performed for the diagnosis and follow-up of moyamoya disease. Diffusion-weighted imaging can also be used for following the clinical course of children with moyamoya disease, in whom new focal deficits are highly suspicious of new infarcts.

Proliferation of smooth muscle cells in the walls of the Moyamoya affected arteries has been found to be representative of the disease. A study of six autopsies of six patients who died from Moyamoya disease lead to the finding that there is evidence that supports the theory that there is a thickening, or proliferation, of the innermost layer of the vessels affected by Moyamoya. These vessels are the ACA (anterior cerebral artery), MCA (middle cerebral artery), and ICA (internal carotid artery). The occlusion of the ICA results in concomitant diminution of the "puff-of-smoke" collaterals, as they are supplied by the ICA.

Often nuclear medicine studies such as SPECT (single photon emission computerized tomography) are used to demonstrate the decreased blood and oxygen supply to areas of the brain involved with moyamoya disease. Conventional angiography provided the conclusive diagnosis of moyamoya disease in most cases and should be performed before any surgical considerations.

Dr. Darren B. Orbach, MD, PhD explains how the disease progresses as well as the role angiography plays in detecting the progression of Moyamoya in a short video

Upon suspicion of PAD, the first-line study is the ankle–brachial index (ABI). When the blood pressure readings in the ankles is lower than that in the arms, blockages in the arteries which provide blood from the heart to the ankle are suspected. Normal ABI range of 1.00 to 1.40.The patient is diagnosed with PAD when the ABI is ≤ 0.90 . ABI values of 0.91 to 0.99 are considered "borderline" and values >1.40 indicate noncompressible arteries. PAD is graded as mild to moderate if the ABI is between 0.41 and 0.90, and an ABI less than 0.40 is suggestive of severe PAD. These relative categories have prognostic value.

In people with suspected PAD but normal resting ABIs, exercise testing of ABI can be done. A base line ABI is obtained prior to exercise. The patient is then asked to exercise (usually patients are made to walk on a treadmill at a constant speed) until claudication pain occurs (or a maximum of 5 minutes), following which the ankle pressure is again measured. A decrease in ABI of 15%-20% would be diagnostic of PAD.

It is possible for conditions which stiffen the vessel walls (such as calcifications that occur in the setting of long term diabetes) to produce false negatives usually, but not always, indicated by abnormally high ABIs (> 1.40). Such results and suspicions merit further investigation and higher level studies.

If ABIs are abnormal the next step is generally a lower limb doppler ultrasound examination to look at site and extent of atherosclerosis. Other imaging can be performed by angiography, where a catheter is inserted into the common femoral artery and selectively guided to the artery in question. While injecting a radiodense contrast agent an X-ray is taken. Any flow limiting stenoses found in the x-ray can be identified and treated by atherectomy, angioplasty or stenting. Contrast angiography is the most readily available and widely used imaging technique.

Modern multislice computerized tomography (CT) scanners provide direct imaging of the arterial system as an alternative to angiography.

Magnetic resonance angiography (MRA) is a noninvasive diagnostic procedure that uses a combination of a large magnet, radio frequencies, and a computer to produce detailed images to provide pictures of blood vessels inside the body. The advantages of MRA include its safety and ability to provide high-resolution three-dimensional (3D) imaging of the entire abdomen, pelvis and lower extremities in one sitting.

Subclavian steal syndrome (SSS), also called subclavian steal phenomenon or subclavian steal steno-occlusive disease, is a constellation of signs and symptoms that arise from retrograde (reversed) blood flow in the vertebral artery or the internal thoracic artery, due to a proximal stenosis (narrowing) and/or occlusion of the subclavian artery. The arm may be supplied by blood flowing in a retrograde direction down the vertebral artery at the expense of the vertebrobasilar circulation. This is called the "subclavian steal". It is more severe than typical vertebrobasilar insufficiency.

It is not clear if screening for disease is useful as it has not been properly studied.

Prognosis of spontaneous cervical arterial dissection involves neurological and arterial results. The overall functional prognosis of individuals with stroke due to cervical artery dissection does not appear to vary from that of young people with stroke due to other causes. The rate of survival with good outcome (a modified Rankin score of 0–2) is generally about 75%, or possibly slightly better (85.7%) if antiplatelet drugs are used. In studies of anticoagulants and aspirin, the combined mortality with either treatment is 1.8–2.1%.

After the initial episode, 2% may experience a further episode within the first month. After this, there is a 1% annual risk of recurrence. Those with high blood pressure and dissections in multiple arteries may have a higher risk of recurrence. Further episodes of cervical artery dissection are more common in those who are younger, have a family history of cervical artery dissection, or have a diagnosis of Ehlers-Danlos syndrome or fibromuscular dysplasia.

Median arcuate ligament syndrome is a diagnosis of exclusion. That is, the diagnosis of MALS is generally considered only after patients have undergone an extensive evaluation of their gastrointestinal tract including upper endoscopy, colonoscopy, and evaluation for gallbladder disease and gastroesophageal reflux disease (GERD).

The diagnosis of MALS relies on a combination of clinical features and findings on medical imaging. Clinical features include those signs and symptoms mentioned above; classically, MALS involves a triad of abdominal pain after eating, weight loss, and an abdominal bruit, although the classic triad is found in only a minority of individuals that carry a MALS diagnosis.

Diagnostic imaging for MALS is divided into screening and confirmatory tests. A reasonable screening test for patients with suspected MALS is duplex ultrasonography to measure blood flow through the celiac artery. Peak systolic velocities greater than 200 cm/s are suggestive of celiac artery stenosis associated with MALS.

Further evaluation and confirmation can be obtained via angiography to investigate the anatomy of the celiac artery. Historically, conventional angiography was used, although this has been largely replaced by less invasive techniques such as computed tomography (CT) and magnetic resonance (MR) angiography. Because it provides better visualization of intraabdominal structures, CT angiography is preferred to MR angiography in this setting. The findings of focal narrowing of the proximal celiac artery with poststenotic dilatation, indentation on the superior aspect of the celiac artery, and a hook-shaped contour of the celiac artery support a diagnosis of MALS. These imaging features are exaggerated on expiration, even in normal asymptomatic individuals without the syndrome.

Proximal celiac artery stenosis with poststenotic dilatation can be seen in other conditions affecting the celiac artery. The hook-shaped contour of the celiac artery is characteristic of the anatomy in MALS and helps distinguish it from other causes of celiac artery stenosis such as atherosclerosis. This hooked contour is not entirely specific for MALS however, given that 10-24% of normal asymptomatic individuals have this anatomy.