TOS definition is brief and it consists of some anatomical anomaly as a precondition and causal event what can be long-term physical activity straining the upper limb and region of upper thoracic aperture or some sudden event in form of trauma in this region. Clinical background of the symptoms on upper limb is a compression of neuro-vascular fascicle in upper thoracic aperture. This fascicle consists of brachial plexus, subclavian artery and vein.

There are three typical anatomical regions for OTS development – first is a scalene triangle demarcated by medial and anterior scalene muscle and clavicula, second is costo-clavicular space between clavicula and first rib with muscle and ligament insertions and the last one is insertion of small pectoral muscle. 

Adopted from Netter´s Atlas of Human Anatomy

In all of these regions there can be some anatomical anomalies which can be a precondition for TOS development. Scalene muscle is variable in its insertions and there can be some tough and thick ligaments causing narrowing of scalene trigonum. A neck rib is an anomaly when there is a rudimentary rib present and connected to the last neck vertebra. Its incidence is up to 1 % with much higher portion of females (7 : 1). This rib is usually present on the left side. The first rib can be also affected by congenital or development anomalies regarding its size and shape. Incidence is the same as for the neck rib but there is no difference in a male and female ratio.

TOS is a disease of young age and in majority of cases it manifests between 20 and 50 years. This age period is logical since TOS needs not only anatomical precondition but also a time of limb straining to develop it manifests in the age of full sport and work activity after 20 years. The same situation is in case of person with anatomical precondition there is high possibility that this disease will manifest most likely till age of 50 years and any later manifestation is usually because of post-traumatic changes. TOS prevalence is clearly higher for female gender (up to 70 % of patients are women), the simple reason is higher incidence of neck rib.

We distinguish three types of TOS based on which part of neuro-muscular fascicle is affected: neurogenic TOS, venous TOS and arterial TOS. The most frequent and unfortunately the most difficult to diagnose and treat is a neurogenic TOS.

Neurogenic TOS is usually caused by a trauma in neck region, e.g. car crash or fall on slippery ground. One side straining of the upper limb such as work at assembling lines leads to micro-trauma in scalene muscle and its fibrotization has its part in the disease development as well. Anatomical precondition for this type of TOS is anomaly of scalene triangle, high insertion of brachial plexus roots and presence of a neck rib.

As mentioned above trauma to scalene muscle (both chronic micro-trauma or acute trauma) lead to stretching and rupture of muscle fibers. Consequent to this trauma is a swelling of the muscle and inflammation causing a compression symptoms in a form of pain and paresthesia of upper limb, numbness and muscle weakness. Damaged parts of the muscle will change to scar in time leading to more tough strains formation and another narrowing of the region. Clinical symptoms are the same plus there can be occipital headaches and vaso-motoric symptoms (e.g. Raynaud syndrome).

For venous TOS manifestation and diagnosis, we have to move one level down to costo-clavicular space, anatomical anomalies in this region and repeated straining of upper limb are the cause of venous TOS manifestation. Repeated micro-trauma to the wall of subclavian vein leads to its fibrotization and stenosis formation which can ultimately lead to vein thrombosis (in case of e.g. dehydration or holding the limb in upper position for long time).

 Sudden swelling and cyanosis of upper limb with pain and forearm veins dilatation are the dominant symptoms of acute subclavian vein thrombosis. If this condition is not recognized and treated early it can lead to venous gangrene of the fingers (this situation is rare). Even after successful treatment there are residual symptoms in up to half of the patients.

Picture shows a clear difference between upper limbs of young man with acute subclavian vein thrombosis.

Adopted from Endovascular today: Management of Subclavian Vein Thrombosis With Mechanical  Thrombectomy; Frank R. Arko III at. Al.

Etiology of arterial TOS is similar to neurogenic TOS, mostly rib anomalies and scalene muscle insertion. If the subclavian artery is compresses there is a post-stenotic dilatation or even aneurysm developing after the stenosis. Turbulent flow in aneurysm can cause thrombus formation with distal embolization or complete aneurysm thrombosis, bot conditions causing acute limb ischemia. Symptoms are paresthesia and pain during exercise or work, ischemic skin wounds and palpable whirl in aneurysm position above clavicula.

Key to proper TOS diagnosis is rigorous patient medical history and consequent physical examination with test, which can amend and confirm the diagnose. I tis important to combine all acquired data, because none single diagnostic test is effective enough for TOS diagnosis confirmation on its own. Important medical history information is work and sport burden leading to one side limb straining (e.g. painters, work at assembling line), trauma in neck and shoulder region, clinical symptoms like limb pain after exercise or occipital headache. Since the diagnostics and treatment of TOS is difficult patients usually visit several physicians in search for someone who can help. This is the reason why we should ask for previous examinations as well.

Differential diagnostic is rich in case of TOS. In case of neurogenic TOS we have to consider carpal tunnel syndrome and tennis elbow, injury of rotator calf, neck intervertebral discs disease and trauma of brachial plexus.

In case of arterial TOS the symptoms can be similar as for any other ischemic disease like atherosclerosis, trauma, dissection, some vasculitis and we have to consider also another sources of embolization such as atrial fibrillation, aortic arch or stenosis of subclavian artery origin.

If there is a strong TOS suspicion based on rigorous medical history information it is time for physical tests. First of them is Adson´s test which starts with palpable pulsation above radial artery of sitting patient (+hearing of whirl above clavicula). Than patient rises upper limb and turns head on the same and opposite side of the limb. Test is positive if the pulsation gets weaker or when whirl or paresthesia develops. Specificity of the test is not high, because up to 50 % of healthy population have the positive test.

Second test is so called EAST (Elevated Arm Stress Test), which is the most precise physical test. Patient puts his/her arms in „I´m surrender“ position for 3 minutes with closing and opening of hand. According to symptoms we can even distinguish type of the TOS. In case of neurogenic TOS patient feels weight, weakness, numbness, paresthesia from fingers moving proximally. In case of venous TOS there is cyanosis and forearm vein enlargement. And in case of arterial TOS patient feels ischemic spastic pain in the hand.

For confirmation of TOS diagnose based on medical history and physical examination we can also use imaging methods. Classic X-Ray can easily show bone anomalies in case of neck and first limb and post-traumatic changes involving clavicula. Imaging of soft tissue is however limited. The same findings can be acquired using CT or MR scans. These examinations can rather exclude other causes of the patient’s problems e.g. stenosis of subclavian artery origin.

Treatment of TOS differs according to the TOS type. In case of neurogenic TOS the treatment is most difficult and options limited. Main pillar of neurogenic TOS treatment is physical therapy in form of guided rehabilitation, stretching and postural exercise. This treatment can lead to relief of symptoms in up to 30% patients, others require surgical treatment similar to arterial TOS. In case of venous TOS the most effective approach in an acute state is a local thrombolysis with possible PTA and consequent anticoagulation therapy. In case of severe subclavian vein compression surgical treatment is indicated as well.

In case of arterial TOS the basic treatment approach is surgical decompression, if the aneurysm is found its resection and bypass surgery is indicated. In contrary to vein surgery antiaggregating therapy is needed after this kind of arterial surgery. To make surgical decompression there are two surgical site accesses – transaxillar which provides better cosmetic outcome but it doesn´t allow to reach upper structures and implant bypass and supraclavicular access which is more technically difficult but it provides better surgical site view and is feasible for vascular reconstruction.

You can see clear subclavian artery compressing in costo-clavicular space on angiography image. Operation site created by supraclavicular access, on the upper right picture is scalene triangle. On the lower pictures is cut clavicula and subclavian artery aneurysm, which was resected and replaced with PTFE prosthetic bypass.

archive of 2nd Department of Surgery

As any other surgery TOS treatment has its specific complications. The most common are injury of structures during the surgery, pneumothorax or post-operative lymphorhea.

Treatment effect of both surgical accesses is comparable. The effect of surgery can not be assessed by physical tests, rather by data from medical history. The bigger is the extend of symptoms before surgery and longer the time the worse outcome can be anticipated. The treatment effect also depends on the etiology of the TOS. The worst outcomes are after the TOS caused by long-term limb straining, better outcomes are after treatment of TOS caused by trauma or acute condition.