What is the thoracic outlet syndrome?

Thoracic outlet syndrome is a collective term describing several conditions associated with compression of nerves and blood vessels at the upper portion of chest. 

What are the organs affected by the thoracic outlet syndrome?

The nerves and vessels supplying the arm pass at the top of the lung in the region called thoracic outlet. It is a heart shaped area bounded by the first thoracic vertebra, left and right first ribs and upper edge of sternum. It is called thoracic outlet because it forms the exit from the thoracic (chest) cavity.


Illustration of a chest wall with thoracic outlet in red color

At the central portion of this outlet several important anatomical structures pass through the neck to chest and vice versa. At the side portion it is occupied by the top of the lung as well as nerves and blood vessels passing to and from the arm.

Five nerve roots emanating from the spinal cord (C5, C6, C7, C8, and T1) form a complex network called brachial plexus. Brachial plexus itself branches off to several nerves that eventually reach the arm. These nerves conduct impulses to and from the spinal cord to the arm. They control every aspect of arm function: skin sensation, muscle contraction, sweating, blood supply, etc. Additionally, brachial plexus gives branches to the skin and muscles in the front and back portions of the chest around the shoulder. 


Schematic illustration of brachial plexus

Subclavian artery and subclavian vein are the major vessels providing blood flow to and from the arm. They pass together with brachial plexus over the first rib at the thoracic outlet. 

Subclavian artery, vein and brachial plexus at thoracic outlet

The nerves and the vessels pass through a narrow space at the upper part of the lung called scalene triangle. This triangle is located just above the first rib in between two scalene muscles. The scalene triangle or space is densely packed and therefore is vulnerable for compression. 

What are the types of thoracic outlet syndrome?

There are three different clinical variations of TOS:

Neurogenic TOS – nTOS. The most common form (approximately 95-98%). Brachial plexus is involved and symptoms are due to nerve compression. Some physicians further divide this group into disputable and definite groups. Definite TOS diagnosis is made when the patient symptoms are proven to be due to brachial plexus compression. Disputable TOS is referred to cases when it is not possible to clearly attribute patient’s symptoms to brachial plexus compression.

Venous TOS – vTOS. Far less common (3-4%). Subclavian vein is affected and the symptoms are due to insufficient blood return from affected arm.

Arterial TOS – aTOS. The least common form (1-2%). Subclavian artery is compressed and the symptoms are due to insufficient flow to the affected arm. Arterial and venous cases are sometimes collectively called vascular TOS. 

What are the causes of the thoracic outlet syndrome?

Women are affected more often than men. There might be several reasons for compression. Some people possess an additional or accessory cervical rib.  Normally, a developing fetus has cervical ribs which should completely disappear. In some people those accessory ribs fail to vanish and cause compression. Anomalous first ribs can also cause TOS. Although rib abnormalities are easy to identify on X-rays they contribute to small percentage of TOS patients.

In the vast majority of cases the cause of compression is a fibromuscular (combination of tough fibrous tissue with muscle) band or a thick ligament around nerves and vessels.  These sturdy bands of fibrotic tissue run from various portions of spine and first rib stretching and tethering the softer nerves, artery and vein. 

In some cases, hypertrophic muscles may cause compression. People extensively using their arms and hands for work and sports are especially prone to TOS. This condition is frequently seen in athletes. Scalene muscle hypertrophy usually results in n- and a-TOS (since both the artery and brachial plexus run inside the scalene triangle). Sublclavius muscle hypertrophy on the other hand, may cause compression and even thrombosis of the subclavian vein (Paget–Schroetter disease).

The site of compression is the scalene triangle above the first rib in the vast majority of cases. However, alternative areas such as subclavian space and costo-clavicular space may contribute to TOS (see picture below – circles demonstrate potential compression sites).

Three compression sites causing thoracic outlet syndrome


What are the symptoms of the thoracic outlet syndrome?

Symptoms of thoracic outlet syndrome depend on the involved structure. 

Neurogenic TOS – nTOS. Pain in the shoulder radiating to head, neck, back, armpit, chest, arm, hand and fingers. Pain may be constant or intermittent. Sometimes chest pain may mimic heart attack and patients may undergo coronary angiography for suspected myocardial infarction. Pain is exasperated by physical activity and raising the affected arm. One of the typical finding is avoiding phone conversations on the affected side due to early arm fatigue and pain. Headache located at the back of the head is quite common in these patinets. In addition to pain patients frequently develop arm and hand numbness and weakness. Numbness may be constant or intermittent. Early morning numbness upon wake-up if a frequent sign in n-TOS patients. Weakness is initially present as early fatigue, but later progresses to significant weakness and wasting (atrophy) especially in the affected hand (Gilliatt-Sumner hand).  

Venous TOS – vTOS. Pain, cyanosis (bluish discoloration) and edema (fluid accumulation) are the presenting symptoms. Symptoms may diminish when the arm is raised up so blood easily flows back. In some cases, subclavian vein is thrombosed resulting in significant compromise of blood flow. In some cases, network of collateral veins is visible in the shoulder and upper chest. 

Arterial TOS – aTOS. Pain, paleness, early fatigue, and coldness are presenting symptoms. Acute cases may require immediate intervention to avoid arm gangrene. Chronic cases may be misdiagnosed as Raynaud syndrome.

Combined symptoms. Vascular symptoms may be combined with neurogenic. In these cases, a combination of above mentioned symptoms may be present. 

How is TOS diagnosis made?

Careful history and physical examination are essential keys to suspect thoracic outlet syndrome. Throughout examination with provocative tests is essential part of patient evaluation. Clinical examination may reveal pain and tenderness in the supraclavicular area. Neurological examination  of the arm and hand is of paramount importance and may demonstrate hypesthesia (numbness) as well as muscle paresis (weakness) and even atrophy (wasting). The presence of muscle weakness is particularly important since it is an indicator of disease severity. 

Provocative testing is essential part of clinical examination. The purpose of these tests is to elicit TOS symptoms using specific clinical maneuvers in order to establish diagnosis. Elevated arm stress test (EAST or Roos test), upper limb tension tests (ULTT’s) and Adson tests are most commonly used. 

Radiographic examination plays an important role in diagnosing TOS. X-ray, CT scan, MRI, Doppler USG are commonly used radiological tools.

X-ray is a very good tool to visualize bone structures. If an accessory cervical rib is present it is visible on plain X-ray. It is also helpful to differentiate advanced cervical degenerative disc disease from TOS.

CT scan is also an excellent tool to visualize bone as well as soft tissue. CT angiography (CTA) is a superb tool to demonstrate subclavian vessels in a non-invasive way. 3 dimensional CT and/or CTA reconstructions can be particularly helpful for preoperative assessment. 

Doppler ultrasonography or Duplex scan is a non-invasive method to evaluate blood flow in the vessels. It is particularly useful in vascular TOS cases. It can demonstrate the presence of subclavian vein thrombosis. High resolution USG of brachial plexus is relatively new method to visualize brachial plexus and can directly demonstrate the site of compression. 

MRI is the most effective tool to demonstrate soft tissue. It can differentiate TOS from cervical disc disease. MRI neurography visualizes brachial plexus itself with high accuracy. Diffusion tensor imaging (DTI) can demonstrate nerve fiber orientation in the brachial plexus and show potential compression sites.

Below, there is 3-dimensional CT angiographic reconstruction from a patient with TOS. Note that subclavian artery narrows as it passes over accessory rib. The accessory rib makes an abnormal joint with the first rib (white circle).

CT angiography of thoracic outlet syndrome showing subclavian artery narrowing by accessory cervical rib

Nerve conduction studies like EMG and ENG may be helpful, but in the majority of cases do not provide definitive diagnosis. Thus, the diagnosis is mainly made by careful clinical examination. 

What is the treatment for thoracic outlet syndrome? 

Light cases are managed conservatively. Armrest, physical therapy, pain killers, breathing and stretching exercises are usually helpful. In some patients, local anesthetic and/or Botox injections can provide temporary relief. 

Severe cases are treated with surgery. It requires complete decompression of the nerves comprising brachial plexus, subclavian artery and subclavian vein.  In order to achieve this goal, a surgeon must remove significant portion of the first rib, find  all nerves, artery and the vein and free them up by cutting all fibrotic bands stretching/compressing them. There is abundant scientific and clinical evidence indicating that the extent of 1st and accessory (if present) rib removal is the single most important factor affecting long-term success. Failure to accomplish total removal results in recurrence of symptoms post-operatively. 

Anterior approach

Surgeon approaches brachial plexus and subclavian vessels from the front. An incision is made above the clavicle (collar bone) and surgeon proceeds with exposure and manipulation of the brachial plexus. The major handicap of this approach is limited access to brachial plexus nerves located at depth of the wound. The subclavian artery and the vein are in front of the nerves further impending the access. 1st and accessory cervical rib removal is technically very difficult because they are located even deeper — under the brachial plexus. Therefore, in some cases the brachial plexus cannot be fully visualized and decompressed and the 1st rib is either left untouched or partially removed. These patients usually either do not benefit from surgery or develop relapse of symptoms after brief improvement period. Not infrequently some patients become significantly worse than before surgery due to significant nerve manipulation during surgery. 

Lateral approach

Surgeon approaches the first rib from the armpit. This approach is preferred by thoracic surgeons. The wound is usually narrow and deep and only midsection of the first rib with subclavian artery and vein can be adequately accessed. Therefore, vascular TOS (arterial and venous) can be effectively treated. Posterior section of the first rib is very hard to expose and remove with this approach. Even if the entire 1st rib resection is performed only very limited lower portion of the brachial plexus can be visualized and decompressed. Therefore like with anterior approach, nTOS treated with this type of surgery may recur.  


PURE procedure

Dr. Aghayev has developed a unique, posterior approach which allows complete removal of the first rib and decompression of all involved nerves and vessels. It is the most effective surgical technique for treating thoracic outlet syndrome.

The surgical procedure is performed from the back with approximately 5 cm (2 inch) incision. The 1st rib and accessory cervical rib (if present) are resected first, without significant exposure and manipulation of the brachial plexus nerves. Bone removal provides decompression of the subclavian artery and vein and increases space for further manipulation. Then the brachial plexus is freed from all compressing fibrotic bands and decompressed. There are several advantages of posterior approach over others. First, the first and accessory rib removal is easy and safe since there are no overlaying and overpassing nerves and vessels. Second, the brachial plexus is very close to the skin allowing the surgeon to work in a shallow area. Therefore, the decompression is easy and effective. Third (and probably the most important), advantage of PURE technique is the absence of recurrence due to total resection of the first rib. Forth advantage is very high level of safety compared to other approaches due to minimal vascular and nerve manipulation. 

Postoperative scar after thoracic outlet surgery


Recurrent thoracic outlet syndrome

Recurrent thoracic outlet syndrome refers to the condition when signs and symptoms of the disease persist or worsen after surgery. This condition is usually due to inadequate decompression. There is strong scientific evidence indicating that the degree of first rib resection and extend of decompression are the strongest factors influencing the long-term success. Typically, patients with TOS undergo surgery either from the front or from the armpit. Yet it is very difficult and risky for the surgeon to remove the first rib totally and therefore deep sections remain untouched. This is the main cause for recurrence after surgery. Symptoms may return from months to years following the surgery. 

Our unique PURE (posterior upper rib excision) technique allows surgeons to totally remove the first rib and pressure from the nerves. That is why our patients never experience recurrence. Recurrent TOS cases can be successfully treated with PURE technique. 


first rib syndrome, cervical rib syndrome, brachial plexus compression, TOS, diagnosis of the thoracic outlet syndrome, symptoms of the thoracic outlet syndrome, treatment of the thoracic outlet syndrome, surgery for the thoracic outlet syndrome