Dr Jason Toniolo

Thoracic Outlet Syndrome

Thoracic outlet syndrome is a big topic. This article hopes to cover some basics as an introduction.

The thoracic outlet describes the bones that permit structures to pass from the chest to the neck and arms. It comprises the clavicle (collar bone), the 1st rib, the scapula and the vertebral column. Imagine a ring of bones sitting at the top of your chest – this is your thoracic outlet. It is a tight space, and things tend to get squashed in some people!

Some patients have anatomical abnormalities predisposing them to thoracic outlet syndromes, such as additional ribs (a cervical rib) or, anatomical abnormalities in which certain muscles specific from the neck to the ribs (scalene muscles) or abnormal fibrous bands are born with. These patients are more likely to develop thoracic outlet syndrome.

Types of thoracic outlet syndrome

Arterial thoracic outlet syndrome (ATOS)

Venous thoracic outlet syndrome (VTOS)

Neurogenic thoracic outlet syndrome (NTOS)

Arterial thoracic out syndrome

Arterial thoracic outlet syndrome is a rare condition. In ATOS, there is damage to the large vessel that delivers blood from your heart to either arm (the subclavian artery). It passes over the first rub and under the clavicle. When you raise your arm overhead, the space between your first rib and clavicle narrows, which can squash the artery. After years of repeated squashing, the artery wall can get damaged and form an aneurysm. These aneurysms can damage the blood flow down the arm. They can block and mean your arm doesn’t have enough blood, or the aneurysm can burst and cause massive bleeding. Usually, patients with ATOS have some anatomical abnormality, such as an additional rib mentioned in the introduction.

Symptoms

It is such a rare presentation that there is no standard pattern. The main presenting symptoms are:

  1. Numbness or damage to the fingers, as small chunks of clots break off from the aneurysm and travel down to the fingers.
  2. A pulsatile mass just below or above the collarbone
  3. Sudden onset of pain from either aneurysm blockage (pain down the arm) or bleeding (pain around the chest).

Management of A-TOS

All patients require surgery to repair the damaged artery and free up space in the thoracic outlet by removing some bony and muscular structures. Surgical correction is invasive surgery that carries significant risk.

Venous thoracic outlet syndrome

A similar issue occurs with the sizeable subclavian vein as does with the subclavian artery. It gets squashed repeatedly and develops scarring and webs within the vein, which prevent the blood from returning to the heart from the arm. Eventually, if someone spends a prolonged time with their arm over their head, the vein may stay blocked for long enough that they develop a large blood clot in their arm.

Symptoms

  • Swelling of the arm
  • The blue/purple colour changes to the arm
  • Pain in the arm, worse when using the arm for exercise or activities of daily living

Management of V-TOS

The decision to have surgery on a venous thoracic outlet syndrome is a discussion that takes around 30 minutes and is best untaken face to face.

In an attempt to summarise, the options are:

  1. Medical management only, with anticoagulation for six months. The blood thinners keep you safe from the clot going to the lungs. They do not fix the symptoms in the arms. The body generally improves circulation over the next six weeks, but some patients still have mild pain or throbbing when they use their arms a lot during exercise. The medical management approach is probably not a good idea for very keen athletes or people with a job requiring constant overhead arm work, such as a teacher drawing on a whiteboard or a painter.
  2. Dissolve or remove the clot and stay on blood thinners, but do not fix the underlying problem: the compression point between the first rib and the clavicle. Removing the clot will improve symptoms, but the clot will come back when more overhead arm movements are performed. The blood thinners can tip the balance such that the vein stays open, but it would be a lifetime commitment to tablets, and it doesn’t always work; sometimes, the vein reoccludes despite the blood thinning tablets. Dissolving the clot needs to be undertaken ideally within the first two weeks of the clot forming and no more than four weeks of the clot forming. The longer the clot stays in the vein, the more difficult it becomes to dissolve or remove.
  3. Remove the clot by sucking it out or dissolving it, then performing a first rib resection. This is an aggressive, potentially dangerous operation, but it completely resolves the issue. Unfortunately, sometimes the vein has so much damage that it blocks off again despite the two procedures (first, to remove the clot; second, to remove the rib). However, the studies done on this topic generally show that people who have their first rib removed to increase the space in the thoracic outlet, even if their vein stays blocked, have far fewer symptoms in their arm and are happier than patients who have a blocked vein and do not have their rib resected. The risks of rib resection are discussed at the end of the article

Neurogenic thoracic outlet syndrome

This condition describes numbness and pain to the nerve trunks that exit the spine up in the neck and traverse down the arms through the thoracic outlet.

Many people develop symptoms of NTOS. However, there are many causes unrelated to the tight space. Generally, physiotherapy and a conservative approach are preferred, as surgery for the issue is aggressive and can lead to problems.

 

Symptoms:

  • Pain extending the entire arm, to shoulder, neck and upper back
  • Numbness in unpredictable distributions down the arm
  • Weakness is often caused by pain inhibition.
  • Difficulty sleeping at night with the arm raised over the head

 

Diagnosis

Three bedside examination tests are used to elicit symptoms and point towards the diagnosis of NTOS, as listed below. They are performed by a vascular surgeon when you have your consultation.

Nerve conduction studies are usually used to rule out other nerve compression issues, such as carpal tunnel syndrome

A local anaesthetic block of the scalene muscle (muscle in the neck that sits between the spine and the collar bone) can be used to help diagnose the condition, as complete resolution of symptoms after injection of the anaesthetic confirms the likely benefit of decompressing the nerve at that level with surgery.

Management

  1. Physiotherapy – variable response to improve scapula movement mechanics and relax the scalene muscles, with posture improvements and alignment of the scapulothoracic ‘joint’
  2. Surgery, which involves rib resection +/- removal of scalene muscle +/- a surgical technique to ‘free’ up the nerves, known as a neurolysis

 

Risks of surgery – first rib resection

The first rib is removed through one or two incisions, either above the clavicle, below the clavicle, or a combination. Some vascular surgeons use an incision through the armpit as another way of getting to the first rib.

Multiple structures need to be navigated in the procedure. There is a nerve that makes one-half of your diaphragm move. If this is damaged, only one lung will inflate when you breathe. Other nerves are involved in your arm’s function and can rarely be damaged from retraction. The large subclavian artery and vein can be injured, which can lead to severe bleeding. The lining of the lung sits right beneath the first rib. This can sometimes be torn when removing the rib, which causes air to on the outside of the lung and collapses a portion of the lung, requiring a tube in the chest to drain the air (pneumothorax). There are lymphatic vessels that traverse the space, particularly on the left, which, if damaged, can lead to an accumulation of milky lymph fluid, which can take months to resolve.