Vanguard Specialty Imaging · September 29, 2026

Three syndromes, one narrow space

Thoracic outlet syndrome is not one disease. It is three, and they share a single cramped corridor above the collarbone. On each side of the body, the brachial plexus, the subclavian artery and the subclavian vein squeeze between the clavicle and the first rib on their way from the neck and chest into the arm. Compress the nerves and you get neurogenic TOS. Compress the vein and you get venous TOS. Compress the artery and you get arterial TOS.

Each type behaves differently. Neurogenic TOS is by far the most common, yet the hardest to prove: its pain, numbness, tingling and weakness mimic cervical disc disease, shoulder pathology, carpal tunnel syndrome and a long list of other conditions. Venous TOS, which accounts for roughly 5% of cases or fewer, often announces itself with a swollen, blue arm and a clot in the subclavian vein. Arterial TOS is the rarest form, around 1% of cases, but also the most dangerous, with the potential for aneurysm, embolism and sudden loss of blood flow to the hand.

That mix creates a real diagnostic problem. Standard imaging was never designed for the thoracic outlet. A routine MRI of the neck or shoulder looks in the wrong place. A conventional MR angiogram suppresses everything except the vessels, so it cannot show what is pressing on them. An MR neurogram brightens the nerves but darkens the muscles, bands and bones that compress them. And most standard studies are acquired with the arms at rest, even though TOS is fundamentally a disorder of movement.

Dr. Scott Werden, a radiologist board-certified in both internal medicine and diagnostic radiology, saw his first TOS patient in 2003. The next year he performed the first NeoVista® MRI in San Francisco. Over three decades of practice and roughly 4,000 patients, that exam has become the reference imaging study that TOS specialists across the country rely on. This article explains how a single NeoVista® examination evaluates all three types of TOS, and why that matters for patients and the physicians who treat them.

What makes NeoVista® different

NeoVista® is a single, comprehensive MRI and MR angiography examination built specifically for the thoracic outlet. It takes about 45 minutes, uses no ionizing radiation, and is protected by three U.S. patents. Four design principles set it apart from piecing together conventional studies.

Both sides, one injection. Conventional contrast-enhanced MRA typically delivers good vascular detail on only one side. Published guidance even advises placing the IV on the side opposite the symptoms, which leaves patients with bilateral complaints poorly served. NeoVista® uses a diluted gadolinium contrast technique that Dr. Werden developed to achieve high-quality images of both subclavian arteries and veins from a single injection. For a condition that is frequently bilateral, that alone changes what the study can answer.

Vessels and surroundings together. TOS is caused by extrinsic structures: ribs, muscles, fibrous bands and the collarbone itself. An angiogram that erases the background shows a narrowed vessel but not the culprit. NeoVista® acquires angiographic, venographic and anatomic images in the same session, so the radiologist can match an abnormal vessel to the exact structure compressing it.

Motion, not just anatomy. Patients are imaged with their arms at rest and again with their arms raised. That provocative positioning reproduces the conditions under which compression actually happens. NeoVista® also includes a proprietary method to measure and compare shoulder girdle movement on each side.

Expert interpretation. Dr. Werden supervises and interprets every NeoVista® study. Reports are detailed, often running several pages, and referring physicians can review findings with him directly by videoconference.

The full examination covers:

• Detailed anatomy of each thoracic outlet
• Images of each brachial plexus
• Angiograms of both subclavian arteries and their branches
• Venograms of the subclavian veins, jugular veins and chest veins
• Soft tissue anomalies, including scalene variants and fibrous bands
• Cervical ribs and anomalous first ribs
• Changes with arm elevation
• The cervical and upper thoracic spine, to rule alternative diagnoses in or out

Acquiring all of these separately at a typical imaging center would take hours in the scanner, and still would not deliver the same integrated view.

Neurogenic TOS: finding the point of compression

Neurogenic TOS is where NeoVista® does its most distinctive work. It is the most common form of TOS and the one most often dismissed, because the standard tools rarely show anything.

The clinical exam has well-known limits. Provocative maneuvers such as Adson's, Wright's and Roos' tests have modest sensitivity and specificity, and none reveals the underlying anatomy. Electrodiagnostic studies measure large motor fibers, while early neurogenic TOS affects smaller sensory fibers deep in the plexus. As a result, EMG often turns positive only in late-stage disease, when treatment success rates are lower. Ultrasound can show the scalene muscles but is blind to the space between the clavicle and first rib, one of the most frequent sites of compression.

NeoVista® addresses each of these gaps by examining the brachial plexus across its entire course through the outlet, at each of the three classic compression sites:

• The scalene triangle. Here the nerve roots pass between the anterior and middle scalene muscles, above the first rib. NeoVista® looks for scalene hypertrophy, muscle slips that pass between or around nerve trunks, scalene minimus variants, and fibrous bands, many of which are invisible on X-ray and difficult to resolve on routine MRI.
• The costoclavicular space. Between the clavicle and the first rib, the plexus is most vulnerable when the arm is raised. Comparing images at rest and with arms elevated shows whether this space collapses around the nerves, and by how much on each side.
• The retropectoralis minor (subcoracoid) space. Below the collarbone, the plexus passes beneath the pectoralis minor tendon. Arm elevation can tighten this space, a pattern increasingly recognized in overhead athletes and in patients with posture-related symptoms.

Beyond compression, the exam evaluates the plexus itself: variant branching patterns, distortion, displacement, and stretch or tension across bony structures. It also identifies cervical ribs, elongated C7 transverse processes, and abnormally shaped or broad first ribs.

Finally, because neurogenic TOS is so often confused with cervical spine disease, NeoVista® includes the cervical and upper thoracic spine. A disc herniation or foraminal narrowing can be confirmed or excluded in the same session, sparing the patient another scan.

Patients describe the difference plainly. Many arrive after shoulder MRIs, cervical spine MRIs, brachial plexus neurograms and repeated nerve conduction studies that were all read as normal. For a meaningful share of them, NeoVista® is the first study to show positive evidence of brachial plexus impingement, and the first to tell their surgeon or therapist exactly where it is.

Venous TOS: seeing the vein and what squeezes it

Venous TOS results from repeated compression of the subclavian vein, most often at the front of the costoclavicular space, where the vein is pinched between the clavicle, the first rib and the subclavius muscle. Over time that compression damages the vein wall. In some patients it leads to effort thrombosis, known as Paget-Schroetter syndrome: a sudden clot that leaves the arm swollen, heavy and discolored. Others have intermittent positional obstruction without clot, sometimes called McCleery syndrome.

When a patient arrives with an acutely swollen arm, ultrasound usually confirms the clot quickly. The harder questions come next. Where exactly is the vein narrowed? Is the narrowing fixed scar or dynamic compression? Are collateral veins carrying the load? And is the other side at risk too? Those answers shape the definitive treatment, which typically involves thrombolysis followed by first rib resection and, when needed, repair of the damaged vein segment.

NeoVista® answers them with bilateral MR venography of the subclavian veins, jugular veins and central chest veins, acquired with the arms both at rest and elevated. That combination separates three findings that can look alike on a single static image:

• Positional compression: a vein that is open at rest but narrows or occludes with the arm raised
• Fixed stenosis: a narrowing that persists in both positions, suggesting wall injury or scarring
• Thrombus or chronic occlusion: clot within the vein, or long-standing blockage with collateral pathways around it

Because the anatomic images are acquired in the same session, the radiologist can identify the structure responsible, whether that is a hypertrophied subclavius muscle, a prominent costoclavicular ligament, an abnormal first rib or a narrowed costoclavicular angle on elevation. The bilateral view is especially valuable in venous TOS. Contralateral compression is common, and knowing whether the asymptomatic side shows the same pattern helps surgeons decide whether to monitor it or address it. NeoVista® also plays a role after treatment, documenting whether decompression has restored normal venous flow across the outlet and whether residual stenosis remains.

Arterial TOS: catching damage before it becomes an emergency

Arterial TOS is rare, but it carries the highest stakes. Mild compression of the subclavian artery with arm movement is common and often harmless. When compression is severe and prolonged, however, it injures the arterial wall. The damaged segment can dilate into a post-stenotic aneurysm, or scar and narrow. Clot can form inside the damaged segment and break off, sending emboli to the fingers or blocking the artery outright. The result ranges from exercise fatigue and cold, pale fingers to acute limb ischemia.

The most common culprit is bony: a cervical rib or an anomalous first rib that elevates and angulates the artery as it crosses. That makes arterial TOS a disorder in which both the vessel and the bone must be seen clearly and in relation to each other.

NeoVista® provides bilateral MR angiography of both subclavian arteries and their branches from a single diluted-gadolinium injection, with images at rest and with arms elevated. The study evaluates:

• Positional stenosis: narrowing of the artery that appears or worsens with arm elevation
• Aneurysm and post-stenotic dilation: enlargement of the artery just beyond the point of compression
• Mural thrombus and occlusion: clot along the vessel wall or blockage of the lumen
• Branch vessel involvement: changes in the vertebral, thyrocervical and other branches that matter for surgical planning

Alongside the angiography, NeoVista® displays the bony and soft tissue anatomy that caused the injury. A cervical rib, a fibrous band extending from an incomplete cervical rib, a prominent first rib tubercle or a scalene anomaly can each be tied directly to the arterial abnormality it produced. Imaging-based detection of cervical ribs is highly reliable on MRI, and NeoVista® characterizes not just their presence but their length, articulation and relationship to the artery. That detail changes who operates and how. As Vanguard notes, a patient with a subclavian artery aneurysm needs a different surgical team and approach than a patient with isolated plexus compression. Knowing in advance that a cervical rib must be removed and an arterial segment repaired allows the vascular surgeon to plan both steps in one procedure.

Because NeoVista® is noninvasive and radiation-free, it also offers an alternative to catheter angiography, which requires arterial puncture, high radiation doses and cannot show the extrinsic cause of compression.

A reference library of more than 3,000 TOS cases

The scanner produces the images, but interpretation is where TOS is won or lost. Dr. Werden draws on a proprietary database of more than 3,000 NeoVista® studies, spanning every form of TOS and every known compression point. No textbook or training program offers anything comparable.

That library matters because TOS is a diagnosis of subtleties. Several factors make every patient different:

• Anatomic variation. Dozens of documented variants of the scalene muscles, fibrous bands, cervical ribs and first ribs can narrow the outlet, alone or in combination.
• Brachial plexus variation. Branching patterns differ between people, and even in a typical plexus the distribution of nerve fibers varies widely. The same compression can produce different symptoms in two patients.
• Motion. Each thoracic outlet changes shape as the arm moves. A finding that is trivial at rest can be decisive with the arm raised, and the reverse.
• Side-to-side differences. Many patients have findings on both sides, but only one side is symptomatic. Telling meaningful asymmetry from normal variation takes a large frame of reference.
• The line between normal and abnormal. Mild compression of the vessels on arm elevation occurs in many people without symptoms. Knowing where the normal range ends is the heart of the diagnosis.

With a new study, Dr. Werden can compare each patient's findings against thousands of prior cases with similar compression patterns: scalene triangle, costoclavicular, subcoracoid, or combinations of all three. Many of those prior cases have known outcomes. Since the exam's earliest days, Dr. Werden has observed TOS operations, followed patients clinically and gathered feedback from treating surgeons and therapists. That surgical and clinical correlation lets him judge which imaging patterns actually predict what surgeons find and which patients tend to improve with treatment.

The result is an interpretation tailored to the individual rather than a checklist applied to everyone. A radiologist who sees a handful of TOS studies a year has no reliable way to tell a meaningful narrowing from a normal variant. Dr. Werden has seen the same pattern hundreds of times, in patients who went on to surgery, conservative care or no treatment at all. That experience is what turns a detailed image into a confident diagnosis.

Why one examination matters

The three types of TOS are taught as separate categories, but patients do not always cooperate. A cervical rib can compress the lower trunk of the brachial plexus and the subclavian artery at the same time. A narrow costoclavicular space can affect the vein and the plexus together. A patient referred for suspected neurogenic TOS may turn out to have unsuspected positional arterial stenosis on the other side.

A workup built from separate studies can miss those overlaps. Each test answers its own narrow question, often read by a different radiologist, often with the arms in only one position. NeoVista® captures nerves, arteries, veins, bones and soft tissues on both sides, in both positions, in one session, read by one radiologist who has focused on TOS for more than two decades.

For referring physicians, the integrated view pays off in four ways:

• Confirming or excluding TOS. A positive finding supports the clinical diagnosis. A normal outlet, or an alternative diagnosis such as cervical radiculopathy, redirects care early.
• Identifying the type. Vascular TOS usually needs prompt surgical care; neurogenic TOS is typically treated conservatively first, often for six to twelve months.
• Guiding the operation. Surgeons know in advance which structures to remove, such as a cervical rib, first rib, scalene muscle or pectoralis minor tendon, and which to repair.
• Tracking results. Post-treatment imaging shows whether decompression was adequate and whether any compression remains.

Don't guess with TOS

Thoracic outlet syndrome usually strikes young, active people: office workers, overhead athletes, musicians, and people recovering from car accidents or falls. Many spend months or years moving between specialists, collecting normal reports, before anyone names the condition. Every delay matters. Neurogenic TOS responds best when treated early, and vascular TOS can turn into an emergency without warning.

NeoVista® was built to shorten that journey. By imaging the nerves, arteries and veins of both thoracic outlets, at rest and in motion, alongside the bones and soft tissues that compress them, one 45-minute examination can show which type of TOS is present, where compression occurs, what is causing it and what the surgeon or therapist needs to address. Dr. Werden's decades of focus, his surgical correlation and his direct availability to referring physicians turn those images into answers.

For physicians: If you suspect TOS, or are weighing surgery for a patient with an unclear workup, NeoVista® provides the anatomic evidence to support your decision. Dr. Werden is available for physician consultations and videoconference reviews of your patients' studies.

For patients: If you have been told "everything looks normal" but your symptoms persist, ask your physician about NeoVista®. Vanguard Specialty Imaging can help you find an imaging partner and connect with an experienced TOS specialist.

Contact Vanguard Specialty Imaging at (678) 674-4867 or visit tosmri.com.

Related reading: How the NeoVista MRI Evaluates Thoracic Outlet Syndrome.

Sources

• NeoVista® Thoracic Outlet Syndrome MRI, Vanguard Specialty Imaging
• Thoracic Outlet Syndrome: Diagnosis, Treatment, Specialists, Vanguard Specialty Imaging
• ACR Appropriateness Criteria: Thoracic Outlet Syndrome, Journal of the American College of Radiology
• Thoracic outlet syndrome registry protocol, PLOS ONE, 2023