Imaging Diagnosis of Neurogenic TOS
Modern imaging provides essential information in patients with neurogenic TOS. Firstly, imaging tests can directly or indirectly demonstrate compression of veins, arteries or nerves. Second, imaging tests can prove secondary damage to these structures, such as an aneurysm. Third, imaging tests can rule in or rule out blood clots, which are a critical factor in determining treatment. Fourth, imaging tests show multiple points of compression that affect treatment differently. Finally, imaging tests rule out abnormalities in the cervical spine, chest, or shoulder.
Clinical tests for neurogenic TOS demonstrate limited sensitivity and specificity. We know that the standard neurological examination often misses the diagnosis of neurogenic TOS. Even specialized provocative TOS tests have proven to be limited in their ability to diagnose or rule out TOS. Additionally, even when these clinical tests are accurate, they do not demonstrate the anatomic or pathologic abnormalities that are causing compression. In contrast, imaging tests demonstrate the anatomy and pathology in patients with TOS in great detail.
Different imaging tests have advantages and disadvantages. X-rays are inexpensive and fast, but do not show crucial soft tissues. Ultrasound is widely-available, and shows soft tissues and blood flow in real time, but is blocked by bones and lung. Direct angiograms and venograms are invasive, and do not show crucial soft tissues outside the blood vessel. CT scans are fast and detailed, show great bone detail, but are limited for soft tissues. CT scans also use higher radiation doses. MRI scans show great soft tissue detail, require no radiation, and can show blood vessels and nerves. Bones do not appear on MRI as brightly as CT. A TOS specialist will know which test to apply for which form of TOS.
Treatment decisions can change according to the results of imaging tests. Different mechanisms cause different types of TOS, and multiple mechanisms can exist in one patient. Doctors can start conservative treatment in one patient, or surgical treatment in another, based on these findings. Additionally, different methods of conservative treatment and different types of surgery may be suggested by imaging findings. Given the anatomic variations in the thoracic outlet, multiple different points of compression are possible. It is hard to imagine that one type of conservative treatment, or one surgery, can correct the unique problem without knowing the detailed anatomy and pathology provided by imaging.
The NeoVista® MRI study gives the patient and doctor unique and valuable information. NeoVista® includes separate and detailed images of the soft tissues, nerves, and blood vessels in one comprehensive study. NeoVista® demonstrates changes on arm motion. And NeoVista® is performed by people with world-class knowledge, earned through years of study, experience, and motivation.
Imaging diagnosis of neurogenic TOS
Imaging of patients with neurogenic TOS provides valuable information to the TOS specialist. While a TOS specialist may strongly suspect that his or her patient has neurogenic TOS, the clinical examination has poor sensitivity and accuracy. Therefore, several outstanding questions must be answered. Firstly, can compression or tension of the brachial plexus be proven? Second, is there intrinsic disease of the brachial plexus? Third, can alternative diagnoses, such as a herniated disc, be ruled out? Fourth, what are the exact anatomic structures that cause compression or tension of the brachial plexus? Fifth, does arm motion contribute to compression? Finally, what other structures are involved, such as arteries or veins?
Fortunately, a dedicated TOS MRI can answer all of these questions and more. Done properly and interpreted by a TOS-specialized radiologist, MRI provides extremely valuable information to the TOS specialist.
What would the ideal imaging test for neurogenic TOS show?
Compression or tension of the brachial plexus
Intrinsic abnormalities of the brachial plexus
Disease of the cervical spine, such as disk herniation
Soft tissues or bones that cause brachial plexus compression or tension
What changes occur on arm movement?
Compression or damage of the arteries or veins
How does a TOS specialist use this data?
It is important to remember that clinical tests used by TOS specialists do not possess very good accuracy. Therefore, while a TOS specialist may suspect neurogenic TOS, he or she cannot easily prove the diagnosis. So, MRI proof of brachial plexus compression or tension provides critical data. Also, rarely, inflammation or trauma of the brachial plexus may cause a similar clinical picture as neurogenic TOS. MRI can clearly rule out such brachial plexus damage.
TOS specialists often find a challenge in distinguishing the symptoms of neurogenic TOS from those caused by cervical spine disease. The NeoVista® MRI examination always includes images of the cervical spine, just for this purpose.
Once the diagnosis of neurogenic TOS is confirmed, treatment decisions can be based on the underlying cause. Patients who have extra ribs or abnormal ribs may need surgery as the primary treatment. On the other hand, patients with soft tissue abnormalities or abnormalities of shoulder motion can respond quite well to conservative treatment. Additionally, given the anatomic complexity of the thoracic outlet, surgeons may use the MRI to plan their surgical goals before the procedure. In most surgical specialties, surgeons have refined and minimized their procedures over many decades. Many surgeons plan to get every pathologic element resolved, while minimizing their effect on normal structures. MRI is widely used in other surgical fields for this purpose. In a similar fashion, MRI may be used in TOS patients for the same reason.
Most neurogenic TOS patients experience symptoms or worsen their symptoms when performing activities. If these changes can be evaluated, conservative treatment plans can be tailored to a specific patient. The NeoVista® MRI uses a proprietary quantitative method of evaluating arm motion on each side, in each patient. We believe this data adds a level of detail that a TOS specialist would find quite important and helpful.
The same process that damages the brachial plexus may compress or damage arteries or veins. Should such compression or damage exist, the surgical plan might require a second, specialist surgeon. MRI provides this data before surgery, which could change the surgical plan.
X-rays show good bone detail, but do not show soft tissue detail, and they are limited to two dimensions. X-rays do not show the brachial plexus, and are almost always normal in patients with neurogenic TOS. In addition, the presence of cervical ribs does not increase the likelihood of neurogenic TOS in any single patient. Therefore, x-rays hold little diagnostic or therapeutic value in patients with neurogenic TOS.
Ultrasound is performed without any radiation, and can distinguish fat, muscle, blood vessels and nerves. Additionally, ultrasound can demonstrate real-time dynamic movement of the arms. At the same time, bones interfere with ultrasound and create blind spots. Thus, ultrasound cannot demonstrate compression of the brachial plexus in the costoclavicular interval, which occurs commonly in these patients. Finally, ultrasound does not clarify fibrous bands and muscle anomalies in detail, which commonly cause brachial plexus compression.
CT, also known as ‘CAT scan,’ utilizes a spinning x-ray generator to create images in 3 dimensions. CT is widely available, and fast, and it shows excellent bone detail. CT images can be reformatted into 3-dimensional models. While CT can easily prove narrowing of the costoclavicular interval, it does not show the brachial plexus well. Additionally, CT does not show other soft tissues well, including fibrous bands and muscle anomalies that frequently compress the brachial plexus. Finally, the patient receives a significant radiation dose during a CT scan. In many centers, CT is the first-line test for patients with neurogenic TOS.
MRI can show the soft tissues of each thoracic outlet in great detail. Scalene muscles and their anomalies, fibrous bands, the brachial plexus and its branches, and the fat that surrounds these structures are very well seen. Bones such as the clavicle, scapula, first rib, cervical rib, and cervical spine can also be seen. MRI can be performed with the arms in different positions. Radiologists can see the changes that arm motion causes.Where can you find an imaging test that answers these questions?
Obviously, we believe in the value of MRI as the best imaging tool for patients with neurogenic TOS. Further, the test and interpretation of this complex disease should be placed in the hands of experienced TOS specialists. At the risk of sounding biased, we feel strongly that the NeoVista® MRI examination answers each of the important questions in patients with neurogenic TOS, and provides experienced TOS expertise.
The full NeoVista® MRI examination is completed in one visit. It includes detailed images and expert interpretation, including the soft tissues and bones of each thoracic outlet, the cervical spine, the brachial plexus, and the subclavian artery and vein. Arm motion is evaluated and measured. This evaluation can be repeated on follow-up examination. In addition, we support your TOS specialist by offering review and discussion of each case. In many cases, we can provide a video teleconference with your specialist and you, including review of your images.
You can try this simple example that shows one component of our test. Grab the handle and slide back and forth to see two different levels of detail of the brachial plexus.
Interactive Media
MRI can demonstrate the brachial plexus in detail. A radiologist can zoom in to evaluate the branching pattern, size, brightness, and course of each nerve root in the brachial plexus.
Treatment of Neurogenic TOS
Primary treatment is performed by urgent treatment of the venous blood clot. Following this, structures that compress the vein are often reduced or removed, and repair of the vein is performed if it is damaged. Learn more about the treatment of venous TOS here.