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Neurogenic TOS Diagnosis


The diagnosis of NTOS has long been quite elusive and even controversial, particularly to those health care providers who do not specialize in TOS.  The reason is that there is no single test or imaging study that can definitively prove or disprove the existence of NTOS.  It is a clinical diagnosis which means that the diagnosis relies heavily on the patient’s symptoms, medical history, and physical examination.  The clinical diagnosis of NTOS is then further supported by objective testing and imaging to rule out more common medical conditions that can mimic NTOS and is then supplemented with a few NTOS-specific clinical tests.  It is also often referred to as a diagnosis of exclusion due to the fact that a large part of the diagnostic process is comprised of ruling out other more common conditions whose symptoms can mimic those of NTOS.  Aside from objective testing, ruling out these other conditions often involves doctors who specialize in these conditions to assist with determining whether these conditions are causing or contributing to the patient’s symptoms. The journey for most patients begins with a primary care physician and then often involves referrals to specialists such as orthopedic surgeons, neurologists, peripheral nerve surgeons, neurosurgeons, and physiatrists.  Most of these referrals and specialists will NOT have NTOS in mind.  For some, a chiropractor or physical therapist will be the first to mention TOS, and the patient will then begin getting referrals with the hope of getting a TOS diagnosis.  For many, these referrals and specialist visits will NOT end with a diagnosis of NTOS.  However, luckily, most of these patients will still make progress toward a diagnosis of NTOS through the testing and procedures ordered for them which will have almost certainly ruled out other more common medical conditions.  Unfortunately, for some of them, this process will also include having had unsuccessful surgeries for conditions which are ultimately found to be most likely inaccurate diagnoses.


Who Diagnoses & Treats NTOS?

Any doctor who is familiar with NTOS can give a preliminary diagnosis.  These most commonly are orthopedic surgeons, peripheral nerve surgeons, or neurologists.  Once a diagnosis of NTOS is suspected, referral should be made to a TOS specialist to make a definitive diagnosis.  TOS specialists are usually vascular surgeons and occasionally cardiothoracic surgeons.  However, most vascular surgeons and cardiothoracic surgeons DO NOT specialize in TOS.  In fact, most of them have very little experience with TOS.  Therefore, it needs to be a vascular surgeon or cardiothoracic surgeon who specifically specializes in TOS.  Although it might seem a bit unconventional, these surgeons treat all three types of TOS including NTOS.  There are some orthopedic surgeons, peripheral nerve surgeons, and neurosurgeons who treat NTOS, but those specialties are in the minority and are not generally represented within the community of high volume TOS specialists.  However, outside the US, where TOS experience and knowledge is more limited, it is somewhat more common to see these other specialties represented in the options for TOS specialists.  For help finding a TOS surgeon, click here.


Conditions That Can Mimic NTOS

Below is a list of medical conditions that have symptoms which can mimic the symptoms of NTOS.  Many of these conditions are more common than NTOS, and thus should be definitively ruled out before any further steps toward a diagnosis of NTOS are taken.  To make things even more complex, it is possible for NTOS to coexist with these other conditions meaning that a patient can have both NTOS and one or more of the conditions that can mimic it.  An experienced TOS specialist in combination with specialists in these other conditions will likely be necessary in a scenario where a patient has been found to have both NTOS and another one of these conditions.  Ideally, the specialists will collaborate to confirm all diagnoses and determine a treatment plan for all conditions particularly as to in what order the treatments should occur.

  • Carpal Tunnel Syndrome

  • Cubital Tunnel Syndrome

  • Radial Tunnel Syndrome

  • Cervical Degenerative Disc Disease

  • Cervical Radiculopathy

  • Brachial Plexus Injury

  • Parsonage-Turner Syndrome

  • Rotator Cuff Injury

  • Bicep Tendonitis

  • Multiple Sclerosis

  • Lymphedema

  • Pancoast Tumor

  • Raynaud’s Syndrome

  • Vasculitis

  • ALS (Lou Gehrig’s Disease)

  • Cervical Dystonia

  • Complex Regional Pain Syndrome (CRPS)

  • Fibromyalgia



Radiology (X-Ray Imaging)

There is no radiology test that will definitively show NTOS.  Therefore, most x-ray imaging would be done to rule out other conditions that mimic NTOS.  Specific imaging tests would likely be ordered based on history and symptoms.  The tests listed below will not all be performed and are not all required. 

Plain Chest X-Ray can be done to look for any anatomical abnormalities such as anomalous first rib, rib fracture, or collarbone fracture. 

Plain Cervical Spine (Neck) X-Ray can be done to look for cervical degenerative disc disease or any abnormalities of the neck bones or to look for cervical ribs or elongated C7 transverse processes.  Most radiologists are not looking for cervical ribs or elongated C7 transverse processes as they are typically incidental findings and most people who have them do not experience symptoms or develop any conditions related to them.  Even if a radiologist does see them, they often leave them out of the radiology report for these same reasons.  If a patient is having this x-ray specifically to help with diagnosis of NTOS, they should request that the ordering physician state that the purpose of the imaging is to rule out cervical ribs.  However, the presence of cervical ribs alone is not diagnostic of NTOS.  In fact, the majority of patients with NTOS do not have cervical ribs.  Only around 10% or less of NTOS patients have them, and they are not required for diagnosis.


Plain Shoulder X-Ray can be done to look for any bony or joint abnormalities or to check for shoulder joint dislocation.

Cervical Spine (Neck) CT Scan mainly done to look for and rule out degenerative disc disease or any abnormalities of the bones of the cervical spine.  It can also help identify cervical ribs and elongated C7 transverse processes.

Cervical Spine (Neck) MRI mainly done to look for and rule out cervical nerve root compression and radiculopathy in addition to compression of the spinal cord usually in the form of disc herniations or neuroforaminal narrowing.  It can also help look for any other soft tissue abnormalities around the cervical spine and nerve roots as well as help identify cervical ribs although not as good as cervical x-ray or CT.

Shoulder MRI can be done to look for and rule out soft tissue shoulder injuries including rotator cuff injury.

Brachial Plexus MRI mainly done to look for and rule out brachial plexus injuries or other soft tissue abnormalities that can impact the nerves such as lipoma, neuroma, or tumors. The test can be performed both with the arms up and with the arms down.  There are a couple of non-specific findings that can be suggestive of NTOS but not diagnostic.  These would be edema of the brachial plexus or loss of fat surrounding the brachial plexus when the arm is elevated.  It can also help with identifying cervical ribs and some scalene muscle abnormalities and fibrous bands.  A normal brachial plexus MRI cannot rule out NTOS.

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Nerve Testing

Nerve testing usually consists of electromyography (EMG) and/or Nerve Conduction Study (NCS).  EMG involves the use of very fine small needles inserted into muscles to stimulate the muscle while it records the electrical activity response to that stimulation.  NCS involves electrodes being placed on the skin to emit low voltage shocks to activate the nerves while it measures the strength and speed of electrical impulses as they move through nerves.  Both tests are for the purpose of measuring how well the nerves and muscles are working.  For NTOS, this will usually be performed on the arms.  They are mainly done to look for and rule out several other conditions that can mimic NTOS such as carpal tunnel, cubital tunnel, cervical radiculopathy, ALS, or certain nerve injuries.


Most patients with NTOS will have a normal EMG/NCS.  The reasons for this are that:

  • the nerve compression with NTOS is intermittent and transient which is difficult to capture during a test done over a short period of time.

  • unless the nerves are showing permanent damage from the compression, it’s unlikely to show up on the EMG and most people with NTOS do not have permanent nerve damage to that degree.


  • NTOS involves nerve compression at the level of the brachial plexus which has a much deeper location within the body which also makes it more difficult to test.


Therefore, nerve testing that comes back normal CANNOT rule out NTOS. There are situations where EMG/NCS is abnormal in a patient with NTOS, such as:

  • When a patient has had longstanding severe compression of the nerves which has resulted in permanent nerve damage.  This is pretty rare.


  • If a patient has both NTOS and another condition such as cervical radiculopathy or carpal tunnel.  It is possible to have both conditions.  When this occurs, it is usually referred to as “double crush” which is when a nerve is compressed at two different places along the same nerve path.  For example, if the median nerve is being compressed both at the cervical spine and within the thoracic outlet.  For another example, if the median nerve is being compressed both at the thoracic outlet and at the carpal tunnel area close to the wrist.  In a double crush scenario, the theory is that when a nerve is compressed at one level, the rest of the nerve downstream from that area sustains swelling, irritation, and is more susceptible to compression injury.  Therefore, if a patient has a nerve study which is positive for carpal tunnel or cubital tunnel, but they are exhibiting symptoms which could not possibly be caused by those conditions, then NTOS diagnosis should not be ruled out and should still be pursued.


  • If NTOS is compressing a nerve within the thoracic outlet which then manifests itself on nerve testing as carpal or cubital tunnel.  Even if not common, sometimes a nerve will show abnormalities on nerve testing that are consistent with carpal or cubital tunnel which are actually being caused by NTOS.

  • If the EMG shows abnormality of the Median Antebrachial Cutaneous Nerve (MACN).  This nerve has recently been shown to have abnormal findings that relate specifically to brachial plexus compression within the thoracic outlet. The problem is that most doctors performing the EMG are not aware of this and are not trained in how to properly test this nerve. It’s typically not part of the standardized testing in most clinics.

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Nerve testing abnormalities indicating NTOS are not required for diagnosis.

Vascular Testing

Venous or Arterial Doppler Ultrasound During the workup for NTOS, these can be done to help rule out any clots or occlusions if the patient is having symptoms that strongly suggest primary vascular obstructions.  Because they are often performed with the arm in several positions, they can also identify if there is loss of blood flow or pulse in these positions.  These tests generally are not useful for the diagnosis of NTOS.  Whether loss of blood flow or pulse occurs with arms in any elevated position is not clinically significant to NTOS diagnosis.  NTOS can occur in patients who do not lose blood flow or pulse with the arms elevated.  Also, healthy asymptomatic individuals can lose blood flow or pulse with the arms elevated.  It should also be noted that these studies assess positional arterial compression which is not diagnostic of ATOS and does not explain the resting symptoms which are more likely being caused by NTOS.  Therefore, findings of loss of blood flow or pulse with arms elevated should not rule out NTOS in favor of an ATOS diagnosis particularly because NTOS is the more likely diagnosis.


Photoplethysmography (PPG)  This test involves infrared sensors being placed on the fingertips which can measure blood flow while the arms are in various positions.  It is sometimes done at the same time as doppler ultrasound but can also be done as a standalone test.  The same diagnostic limitations and qualifications apply to this test as for the doppler ultrasound as stated above.

CT Angiogram of the Chest this is a CT scan of the chest which can show the vessels particularly the axillary-subclavian vein and axillary-subclavian artery.  It is typically done both with the arms up and the arms down.  It can help determine location of compression of the vessels, and the condition of the vessels as far as any clots or damage.  It is not typically done if a patient is only being worked up for NTOS.  However, some TOS specialists do use it for NTOS diagnostic workup, but they only take into consideration compression when the arm is in the down position (at rest).  Their interpretation is that if there is mild compression of the axillary-subclavian artery with the arm at rest, then this can be consistent with NTOS.  The reason for this is that the artery and the nerves are side by side as they travel through the thoracic outlet thus if the artery is compressed, then the nerves must be as well. Unless the patient is seeing a TOS specialist who specifically uses this test as part of his or her NTOS workup, it is not a test that would typically be suggested to be done.

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A thorough and targeted physical exam is an extremely important aspect of any NTOS diagnostic workup.  TOS specialists typically rely heavily on this.  There are actually very specific findings on physical exam that are unique to NTOS.  Below is a list of what is typically assessed during a targeted NTOS physical exam:

  • Resting posture of the patient.  NTOS patients will often have posture where the shoulders are rounded and the head and neck are slumped forward.

  • Range of motion of the arm as well as whether any symptoms are triggered by these movements.

  • Range of motion of the neck – turning side to side and bending ear to shoulder and whether any symptoms are triggered.  NTOS symptoms are often triggered by turning the head toward the shoulder of the affected side and by side bending the head with ear to shoulder of the non-affected side.

  • Hand grip and strength

  • Hand muscle atrophy

  • Exam of nerves in the lower arm to check for signs of carpal and cubital tunnel.  However, it should be noted that if the explanation for symptoms or physical exam findings is that the patient has multiple nerve compression syndromes of the lower arm such as carpal tunnel and cubital tunnel, then it should be considered that the compression is occurring up at the level of the brachial plexus.

  • Swelling, temperature or color changes of the arm and hand

  • Tenderness of the back of the neck over the cervical spine (may indicate cervical spine disease).

  • Increase in symptoms when tilting the head back or when bending the head down toward the chest (may indicate cervical spine disease).

  • Tenderness and pain when pushing on the shoulder joint (may indicate shoulder soft tissue disease)

  • Shoulder blade winging which can be seen with NTOS but can also be caused by a separate primary nerve injury or entrapment issue.

  • Tenderness or deformity of the collarbone joints

  • Tenderness of the SCM, upper trapezius, and other upper back muscles including muscles surrounding the shoulder blade

  • Tenderness with pushing within the scalene triangle and at the base of the neck just above the collarbone (supraclavicular area) along with whether arm symptoms are triggered by this. This part of the exam can also identify scalene muscle spasm. These findings are unique to NTOS, and this is a very important part of the exam as almost all NTOS patients will have these findings which strongly support NTOS diagnosis.

  • Identification of any signs of NPMS, ATOS or VTOS.



Provocative maneuver testing is tests involving different arm and/or head & neck movements (maneuvers) which are intended to trigger (provoke) certain symptoms.  The two most common tests which are specific to NTOS diagnosis are the Elevated Arm Stress Test (EAST) and the Upper Limb Tension Test (ULTT).  Some physicians, typically those who do not specialize in TOS, will use other provocative maneuver tests which are designed to assess positional artery compression where loss of pulse is triggered by certain elevated arm movements.  These tests are the Adson’s Test and the Wright’s Test which are considered to be positive if there is loss of pulse.  Loss of pulse does not directly relate to NTOS nerve compression, and these tests also have a high positive rate in normal asymptomatic individuals.  In addition, most patients with NTOS will not lose their pulse with arm elevation.  Therefore, the Adson’s and Wright’s tests, when negative, cannot rule out NTOS and, when positive, are nonspecific to NTOS.

Elevated Arm Stress Test (EAST) – aka Roos Test  Some TOS specialists consider this test to be the most useful provocative maneuver test for NTOS.  It involves having the patient raise both arms in a “surrender” position while they repeatedly open and close their hands for 3 minutes.  Most patients with NTOS begin to experience reproduction of their symptoms quite quickly within the first minute and are unable to continue to complete the test. If the patient has no symptoms triggered and does not have any difficulty completing the test, it can be interpreted as such that perhaps an alternative diagnosis should be considered.

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Upper Limb Tension Test (ULTT)  This test involves the patient holding both arms out to their sides at shoulder height with palms facing down.  The patient extends both wrists up so fingers are pointing at the ceiling and the neck is side bent toward the non-affected side.  Majority of NTOS patients will have symptoms reproduced during some stage of this test.


It’s important to note that a muscle block and a nerve block are not the same thing.  Generally, any type of block injection involves using some type of numbing agent such as lidocaine.  A nerve block involves injecting lidocaine around a nerve or nerves basically to completely deaden the nerves so that they cannot transmit any signals.  With respect to a brachial plexus nerve block, injecting lidocaine around the brachial plexus will only deaden all the nerves which may provide pain relief along with possibly an entirely numb arm, but it will not provide any NTOS diagnostic information.  Simply numbing all the brachial plexus nerves will not provide any information about what is causing the symptoms.  It just might provide temporary relief of symptoms.  A muscle block involves injecting lidocaine directly into a muscle which deadens the intramuscular nerves.  The purpose of this is to temporarily interrupt muscle spasm.

Scalene Muscle Block  Because the scalene muscles are often one of the main contributors to NTOS nerve compression which often involves muscle tightness and spasm, a good way to test for NTOS is to stop that spasm and see if there is any symptom relief.  Stopping the muscle spasm essentially decompresses the nerves.  This is one of the only diagnostic tests that is specific to diagnosing NTOS as opposed to ruling out other medical conditions.  Even though both the anterior and middle scalene muscles can cause nerve compression, typically the muscle block is only performed in the anterior scalene muscle.  To ensure precise injection location and for safety purposes, it is performed with ultrasound or other imaging guidance such as MRI.  The lidocaine is injected directly into the anterior scalene muscle and is typically fast acting within minutes.  Most TOS specialists consider a positive response to the block to be obtaining at least 50% relief in symptoms.  This measurement does not only apply to pain but to any NTOS symptoms such as range of motion, feeling of arm weakness or fatigue, numbness, tingling, discoloration, or cold sensations, etc.  To help the patient with measuring the block response, most clinics will have the patient fill out a pain/symptom diary for a certain number of hours following the block.  Sometimes they will have the patient do some provocative maneuvers both before the block and after the block to see if there is any difference in ability or symptoms that are triggered.  While the block is active, some patients will try to do certain activities that are usually difficult for them or that trigger symptoms to see if they are better able to do them.  Typically, the block only lasts for several hours at most.  A positive block response is a very strong indication that NTOS is the proper diagnosis, and some specialists consider it a high likelihood that the patient will respond to treatment whether it is conservative or surgical.   


However, a positive scalene block response is not required to make a diagnosis of NTOS.  In addition, a negative scalene muscle block response cannot rule out NTOS and does not mean that a patient will not respond to either conservative or surgical treatment. Some reasons why a patient with NTOS might not get relief from an anterior scalene muscle block are as follows:

  • The amount and location of the lidocaine injected might not have been accurate resulting in no spasm interruption or only partial spasm interruption.


  • the anterior scalene muscle spasm is not the main cause of the patient’s TOS symptoms. Some people with TOS have the middle scalene as the main cause of their symptoms as opposed to the anterior scalene.


  • The patient has extensive scarring in the anterior scalene that makes it less responsive to the lidocaine. The lidocaine stops muscle spasm immediately by causing a complete blockade of the intramuscular nerves within the muscle tissues. If the muscle fibers are very scarred which can be common for many with NTOS, then that tissue might not fully respond to the lidocaine. In this case, the nerves within the muscle will not get completely blocked so the spasm never really gets stopped. 

  • The patient has advanced nerve damage such that even with interruption of the anterior scalene muscle spasm, the nerve symptoms don’t get relieved.

Botox Injections  Botox injections to the scalene muscles for NTOS are more typically used as a symptom relief measure than as a diagnostic tool.  However, some specialists do use them to assist with diagnosis.  They are used under the same principle as the lidocaine muscle blocks in that Botox interrupts the muscle spasm and therefore decompresses the nerves resulting in symptom relief.  Botox does not take effect as quickly as lidocaine because it works in a different manner, but if effective, it can last up to 3 months.  There can be different scenarios under which someone might not respond well to the Botox.  Therefore, the same qualifiers apply here as for the lidocaine muscle block, which is that a negative Botox response cannot rule out NTOS, and it does not mean that a patient will not respond to either conservative or surgical treatment.

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In 2016, the top TOS specialists in the United States collaborated to come up with standardized diagnostic criteria for all 3 types of TOS.  It was published in an article in the Journal of the Society for Vascular Surgery.  Below are the published standardized criteria for the diagnosis of NTOS.

Reporting Standards NTOS Diagnostic Criteria
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Illig KA, Donahue D, Duncan A, Freischlag J, Gelabert H, Johansen K, Jordan S, Sanders R, Thompson R. Reporting standards of the Society for Vascular Surgery for thoracic outlet syndrome. J Vasc Surg. 2016 Sep;64(3):e23-35. 



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