Thoracic Outlet Syndrome

Overview

“Thoracic outlet” is the medical term used to define the space between the cervical spine and the armpit. It contains three important structures: the brachial plexus (the network of nerves that provides movement and sensitivity to the upper limb), the subclavian artery and vein. The brachial plexus and the subclavian vessels together are often called “neurovascular bundle”.

 

THORACIC OUTLET SYNDROME ( TOS) is a medical condition consequent to the compression of  the neurovascular bundle in this passageway.

This picture helps you to locate the thoracic outlet region and to visualize the anatomical elements involved in TOS.

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Causes

According to the structure that is mainly affected by compression, three main type of  TOS are possible: arterial, venous and neurogenic TOS. The vascular forms (arterial and venous TOS) are rare, they affect less than 10% of these patients.  Neurogenic TOS is the most common type and it occurs when the compression is mostly on the proximal course of the nerves (the “roots”) forming the brachial plexus.

Three possible sites of compression are described: between the cervical spine and the clavicle, under the clavicle and under the pectoralis muscle tendon at its insertion on the coracoid process. They are illustrated in the picture below.

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The most frequent site of compression is between the cervical spine and the clavicle and it specifically occurs in the interscalene triangle, a triangular space delimited by two muscles (the anterior and middle scalene muscles) and the clavicle.

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This illustration compares the anatomy of the interscalene triangle in a normal situation with thoracic outlet syndrome.

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The factors that predispose the individual towards the onset of TOS can be divided into innate and acquired.

Innate factors are related to the presence of anatomical anomalies. A type of anatomical anomaly frequently described in association with TOS is a cervical rib, a congenital extra rib that forms above the first rib. Most cases of cervical ribs are not clinically relevant and are not responsible of the onset of symptoms: they are generally discovered incidentally, they are estimated to occur in 0.2 % to 0.5% of the population. However they widely vary in size and shape and, in rare cases, they can contribute to the development of TOS, because they can be responsible of a compression on the eurovascular bundle inside the interscalene triangle.

 

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Normal

Thoracic outlet syndrome due to cervical rib

Thoracic outlet syndrome due to cervical rib

 

Innate factors predisposing to TOS are less common than acquired factors.

People whose work or sport is connected with frequent lifting and abduction of the upper limbs above the level of the shoulders are predisposed to the occurrence of compression on the neurovascular bundle inside the interscalene triangle.

Neurogenic TOS is also related to the adoption of postures that result in the asymmetrical setting of the rim shoulder: for instance, long hours sitting at a desk and working at the computer or long-term, incorrect positioning of the upper limbs during sleep are a common lifestyle in patients that develop symptoms related to TOS. Faulty, non-ergonomic postures lead to a muscle imbalance that makes the anterior scalene “hypertrophic” (bulkier and thicker than it should be) and therefore compressing on the neurovascular bundle.

The development of muscle imbalance affecting the shoulder girdle is not only related to the patient’s profession but can be consequent to constitutional features: it is well known that women  with narrow shoulders and long, slender necks, especially if they have heavy breasts, seem to be more predisposed to thoracic outlet syndrome.

Mild traumas of the cervical spine such as those occurring during a “whiplash injury” (a sudden flexion/extension of the neck usually consequent to a rear-end collision in road traffic accidents)   can cause spontaneous minor bleedings in the interscalene muscles, causing fibrosis and scarring that eventually lead to muscle contractures and consequent scalene hypertrophy.

 

Symptoms

The incidence of thoracic outlet syndrome is at least 1-2% of the population; women are more prone than men, at a ratio of approximately 3:1. The age range of TOS occurrence is between 20 and 60 years old, but there are also cases diagnosed in children and teenagers.

TOS can be bilateral, affecting each side with different intensity or at different times.

Two clinical presentations are described.

Most of the patients experience cervicalgia (neck pain) associated with a painful radiation along the upper limb. Pain often radiates also to the shoulder blade, axilla and the lateral wall of the thorax.

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In some cases, patients complain about pain in the anterior aspect of the neck from the clavicle to the mandible, ear, the side of the face and occipital headache.

Pain is associated with sensory disturbances, described as numbness and tingling radiating along the limb and especially in the hand until the finger tips, in the majority of cases mostly affecting the little finger and the index.  Symptoms usually worsen at night, often completely disrupting the sleep quality. At their awakening, patients often find that their hand is swollen and stiff.

Pain, numbness and tingling are systematically worsened also when carrying weights (ladies usually report that they are not even able to carry their bag on the affected shoulder) and whenever working in prolonged abduction (with the arm lifted up to the shoulder level or higher): even daily activities such as talking on the phone, applying make-up on or drying their hair can trigger the worsening of the pain intensity or the numbness and tingling,  especially on the little finger and the index.

In a minority of cases, usually teenagers or young ladies in their early 20s, TOS may manifest as progressive development of a waste of the hand muscles, without premonitory pain or sensory disturbances.

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Diagnosis

The diagnosis of TOS is not easy: pain and numbness along the upper limb are frequent complaints and related to several medical conditions. Moreover, this syndrome is often associated with cervical spine pathology and /or other nerve entrapments (such as carpal tunnel syndrome or ulnar nerve entrapment at the elbow) and the clinical presentation can be misleading for physicians that are unexperienced in peripheral nerve pathology.

TOS is essentially diagnosed according to clinical evaluation (that means that Your history is suggesting that this is what can explain Your symptoms), after ruling out the possibility of other pathologies (first of all cervical spine pathology). The radiological finding of a cervical rib does not justify a diagnosis of TOS and, on the contrary, the absence of a cervical rib is not enough to rule out this possibility.

Radiological investigations such as a cervical spine MRI (to rule out cervical spine pathology such as a herniated disc) and a dynamic MRI study of the brachial plexus (to exclude other brachial plexus pathology and evaluate the neurovascular bundle topography in neutral position and during shoulder abduction) are regularly prescribed.

Electrodiagnostic tests (EMG and nerve conduction study) are also routinely utilized to complete the diagnostic assessment. Findings are usually unremarkable in cases of “pure” TOS but they may detect the presence of another pathology (e.g. a carpal tunnel syndrome associated with TOS is a frequent occurrence)

All the information provided by the investigations are finally evaluated by Your surgeon to confirm the diagnosis.

 

Treatment Options

  • Conservative treatment

Conservative treatment:in the initial forms of thoracic outlet syndrome, physiotherapy is usually prescribed in order to correct the postural imbalance. At least 3 months of regular physiotherapy are usually necessary to relieve the symptoms. Some physicians also advocates the prescription of corticosteroids but these medications provide only temporary subsidence of pain and numbness.

Surgery:as the symptomatology is the consequence of mechanical compression, surgery (that is decompression of the nerves and the artery) is certainly the elective treatment option.

 

  • Surgical treatment

Your treating doctor may recommend surgery if other treatment hasn’t been effective and if you’re experiencing ongoing symptoms or if you have progressive neurological problems.

Thoracic Outlet Surgery

Indications for surgery:if muscle atrophy is present, indication for surgery is straightforward: there is no possibility to recover without surgical decompression. Moreover, if denervation (that means that signs of nerve damage are detected given the progressive muscle waste) occurs, surgery is necessary also to prevent further worsening.

Surgery is also advocated in initial cases when conservative treatment failed, symptoms have been ongoing for long periods or their intensity is so severe to remarkably disrupts the patient’s quality of life.

Type of surgery:The procedure is performed under general anesthesia. The surgeon performs an intervention named scalenectomy. Through a 5-6 cm long incision above the clavicle, the insertion of the thick and bulky anterior scalene muscle is resected close to its insertion on the first rib.

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The anterior scalene resection has no consequences. There are 6 scalene muscles (3 on each side) and they are only additional muscles during inspiration (the main motor being the hemidiaphragma).

Once the anterior scalene muscle is resected, the surgeon explores the area searching for further causes of compression. The presence of fibrous bands is occasionally the  cause of additional   compression on the neurovascular elements, therefore their resection is also necessary to completely release the nerves and the subclavian artery.

At the end of the procedure a drain is put to allow the outflow of possible bleeding in the hours following the surgery

 

Length of hospitalization:Thoracic outlet syndrome is usually requiring 2 to 4 days in the hospital. The drain is generally removed the day after the surgery.  After the procedure, You can move Your upper limb without restrictions and resume your daily activities with the exception of  performing efforts (such as carrying weights) with the operated arm.

 

Specific risks and issues related to thoracic outlet surgery

  • Damage to the brachial plexus and the subclavian vessels:In thoracic outlet surgery there are potential risks to have remarkable bleeding from the subclavian artery and veins if they are damaged but the real possibility for such an occurrence in the hands of an experienced surgeon is definitelyvery remote. The possibility to damage the nerves is also unlikelyfor the same reason.

 

  • Bleeding:every surgical procedure entails the risk of bleeding. The possibility that post-operative excessive bleeding  is going to require additional surgery to drain the blood clot is statistically very rare. Patients taking aspirin, warfarin or snit-inflammatory medications are usually the ones at risk for this complication.

 

  • Lymphatic loss:the thoracic outlet also harbors lymphatic ducts and they might be damaged during the procedure. Rarely there might be a lymphatic leak in the early days after surgery and if it is excessive, the surgeon can give indication for revision surgery: persisting lymphatic leak in the surgical area not only exposes to the risk of recurrence of the preoperative symptoms (lympha “irritates” the nerves) but only leads to protein loss that might have remarkable consequences on Your general health. Lymphatic leak is anyway a very rare

 

  • Pneumothorax: the “floor” on which the subclavian artery and the lower trunks of the brachial plexus run is the apex of the ipsilateral lung. As you might know, the lung is covered by a membrane called pleura. If during the surgery, a pleural tear occurs, air can get into the space between the pleura and the lung given compression on the latter. Most of the times, the quantity of air is very little and it will progressively reabsorbed in a few days but occasionally there might be the need to put a drain to let the air in excess out. The possibility to develop a pneumothorax after scalenectomy is very rare.    

 

  • Infection and/or bad healing of the scar: every surgical procedure can be associated with the potential risk of infection and/or bad healing of the scar but this is also rare:diabetic patients (especially if their sugar blood is not under good control) may be at risk for this complications.

 

  • Firmness and change in skin sensation:excessive firmness and diminished skin sensation can be experienced in the area where the surgery was performed. This is not usually considered a complication but a normal sequela of cutting the skin and underlying tissues and occasionally can be more pronounced due to internal scarring.

 

  • Non improvement: thoracic outlet syndrome is often ongoing for years before the patient gets the treatment. Being an uncommon decease, it is very often undiagnosed and therefore the indication for surgery is often delayed. In these cases the successful outcome is less likely due to fact that the prolonged compression can have caused an irreversible damage to the nerves.

If thoracic outlet syndrome is associated with other conditions (such as cervical spine arthrosis), this also may reduce the benefit after the surgery.

It is important to follow post-operative instructions to minimize possible risks and complications.

 

Specific risks and issues of not doing surgery

If the compression on the nerves is ongoing, there will be persistence of pain, numbness and tingling. Risks to develop an impairment of the sensory and motor function of the upper limb/ hand are rare but this possibility cannot be excluded.

 

 What to expect after surgery

 Relief of preoperative symptoms (pain, numbness and tingling) is usually progressive in the weeks following the procedure although the patient mostly reports she/he perceives the limb “lighter” and the hand is not anymore swollen in the morning immediately after the surgery. Improvement can be noted even 6 months after the procedure.

Recovery instructions will be provided by your surgeon after the procedure according to her evaluation of your case.




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