THORACIC OUTLET SYNDROME

 

Description

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

 

Anatomy

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 nerves 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, movement, sweating, degree of blood supply etc. Additionally, brachial plexus gives branches to the front and back portions of the chest as well as neck. 

 

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. 

 

Classification

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. 

 

Causes

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 band or a thick ligament around the 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 the 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

 

Symptoms

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 aggravated 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. In addition to pain patient develop numbness and weakness. Numbness may be constant or intermittent. Early morning numbness upon wake-up if a frequent sign in nTOS patients. Weakness initially present as early fatigue but later may progress to significant muscle wasting especially in the affected 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 is significant compromise of blood flow. In some cases, network of collateral veins gets enlarged and visible in the arm and upper chest to compensate for blocked subclavian vein. 

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

Combined symptoms. Vascular TOS cases may be associated with neurogenic symptoms. In these cases, nerve compression symptoms are mixed with vascular phenomena. 

Diagnosis

Careful history and physical examination are essential keys to suspect thoracic outlet syndrome. Throughout examination with provocative tests is an essential part of patient’s evaluation. MRI of the cervical spine should be performed to rule out cervical disc herniation and nerve root compression. Brachial plexus MR neurography is an excellent tool evaluate the brachial plexus yet it lacks diagnostic specificity. However, it may reveal tumors and traumatic lesions in the brachial plexus. X-ray and CT examination is very helpful if cervical accessory rib is present. Yet, in the vast majority of cases accessory ribs are absent. Ultrasound examination with Doppler flow assessment is helpful to evaluate blood flow in subclavian vessels and especially useful when combined with provocative arm positioning. In some instances, angiography maybe used to visualize subclavian vessels. 

Below, there is 3-dimensional angiographic reconstruction from a patient with TOS. Note that subclavian artery narrows as it passes over accessory rib. The acessory 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. 

Treatment 

Light cases are managed conservatively. Armrest, physical therapy, pain killers, and stretching exercises are usually used. In some patients, local anesthetic or Botox injections can be very helpful. Yet, these injections usually provide only temporary relief. 

Severe cases are treated with surgery. Surgery requires complete decompression of the nerves, artery and vein.  In order to achieve this goal, a surgeon must remove significant portion of the first rib, find and free up the nerves, artery and the vein by cutting all bands stretching them. There is abundant scientific and clinical evidence indicating that the extend of 1st rib removal is the most and single important factor affecting long-term success. With insufficient resection recurrences are frequently seen after surgery.vUsually the surgery is performed either from the front or from the side.

Anterior approach

Surgeon approaches brachial plexus and subclavian vessels from the front. An incision is performed above the clavicle (collar bone) and surgeon proceeds with exposure and manipulation of the brachial plexus. The major handicap of this approach is limited ability to expose and manipulate on deep sections of the brachial plexus. Also removal of the first rib requires significant manipulation of the brachial plexus which may lead to temporary or permanent damage. 

Lateral approach

Surgeon approaches thoracic outlet from the armpit. Usually this approach is preferred by thoracic surgeons. It provides sufficient exposure to remove midsection of the first rib. Therefore vascular TOS (arterial and venous) can be effectively treated. Posterior section of the first rib is very hart to reach with this approach and therefore nTOS treated with this type of surgery frequently 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 considered by some surgeons as the mosf effective technique for treating thoracic outlet syndrome. Another significant advantage of our PURE technique is high level of safety. When compared with other techniques it has a unique feature of being the least risky. Incrasing number of patients have been treated by Dr. Aghayev's method and no recurrence has been observed so far. 

The surgery is done from the back and provides an excellent exposure of all brachial plexus nerves and subclavian vessels. The insicision size is approximately 5 cm (2 inches) and the patients are discharged on the second or third day after surgery. Patients are recommended to avoid excessive arm use for one month. Usual recovery period is about 3 month.

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.