Dr Graham Exelby revised December 2023
Acknowledgment: this article has been produced with a large contribution by Kjetil Larsen. His work is reproduced with his permission. Details of the impact of posture and management are seen on his website: https://trainingandrehabilitation.com/how-truly-treat-thoracic-outlet-syndrome/
Many of the typical symptoms associated with Postural Orthostatic Tachycardia Syndrome (POTS,) irrespective of the cause, can be traced to a set of mechanical “drivers” aggravated by other inflammatory causes and DNA predisposition.
To summarize the clinic findings in POTS, there are a series of vascular compression syndromes that we have found in all POTS (over 350). Head and neck vascular and mechanical pathology underpins 85% of POTS and drives symptoms, with impaired venous, arterial and lymphatic flow in the head and neck, and consequent vascular flow changes in the brainstem and brain proper. These appear responsible for Intracranial Hypertension, Intracranial Hypotension with CSF leaks, and Intracranial Vascular Pressure Dysfunction.
Jugular outlet syndrome (JOS) , (Venous Eagle, or Styloidogenic Jugular Venous Compression Syndrome) is very common finding in our POTS vascular compression studies with very high level of correlation where the Internal Jugular Vein (s) is compressed between the transverse process of the first cervical vertebra and the stylohyoid ligament, with varying levels of compression. The preliminary studies suggest that Venous Thoracic outlet Syndrome accompanies these, with a strong correlation between VTOS, JOS and cervical spine pathology.
While case studies have found changes in head and neck vascular and musculoskeletal function in most POTS, there are many with intra-abdominal compression areas. Increasingly there is a high incidence of Median Arcuate Ligament Syndrome (MALS), Superior Mesenteric Artery Syndrome (SMA) as well as the Nutcracker and May-Thurner Syndromes presenting as POTS. This concurs with the increased incidence noted between pre-Covid and post-Covid patient numbers.
We cannot as yet ascertain if these “rare diseases, especially MALS and SMA” signify the microglial -induced small fibre neuropathic central sensitization, or a change in collagen or both. Improved radiological methods may also be a significant factor. As we have no way to confirm these, so this remains a series of comparative observations.
The “mechanical and hydraulic” causes we have found in clinic are described as:
· Thoracic Outlet Syndrome (TOS). Arterial TOS can have direct effects on cerebral circulation. Venous TOS is clinically and functionally directly related to JOS and cervical spine dysfunction, generally from poor posture and trauma
· Jugular Outlet Syndrome (JOS) where the Internal Jugular Vein (s) is compressed between the transverse process of the first cervical vertebra and the stylohyoid ligament. Jugular Outlet Syndrome is intricately linked to the Thoracic Outlet Syndrome and upper cervical pathology. Internal Jugular Vein Stenosis (IJVS) and Internal Jugular Vein Obstruction (IJVO)- (36)(35)(34) collectively with Jugular Outlet Syndrome, both affect venous outflow from the brain,(42) but the jugular dilation of the Internal Jugular Vein potentially affects the vagus, carotid baroreceptors, cervical sympathetic chain and jugular nerve.
· Collectively the JOS and IJVS has been referred to as chronic cerebrospinal venous insufficiency (CCSVI) (34). Dynamic scanning of the Subclavian and Internal Jugular veins in a small preliminary study of 15 has shown the Internal Jugular Vein to dilate as the arms are elevated, and when neck flexion is added, obstruction to Internal Jugular Vein flow has been shown, the IJV flow return slow to return. These results mirror the findings by van Campen, Rowe and Visser (41) in middle cerebral artery flow in CFS. As this has been accompanied by POTS symptoms, this requires formal studies to confirm the importance of this finding, and to differentiate the relative importance of each facet -Internal Jugular Vein Dysfunction- Jugular Outlet Syndrome, Internal Jugular Vein Stenosis and Obstruction.
· Loss of cervical lordosis/ flexion kyphosis – potentially impacting on Vertebral Artery flow as found by Bulut (38), Vertebral Vein and surrounding lymphatics
· All the above are likely to cause lymphatic obstruction as these in particular surround the Internal Jugular and Vertebral Veins. This impaired lymphatic flow potentially creates “backpressure” in the Glymphatic System which is affected by genetic predisposition, sleep disorder, and most importantly Covid infections.
· In the abdomen the primary ones involve the Coeliac axis (MALS and SMA), Renal Vein Compression with gonadal vein reflux (Nutcracker Syndrome) with pelvic congestion, and May-Thurner Syndrome involving the iliac veins. Recent advances in radiology has shown a high incidence of left renal vein compression associated with Superior Mesenteric Artery Syndrome (SMA), providing a potential explanation for intra-abdominal venous (and spinal vein plexus) dysfunction in SMA, previously unable to be explained. The venous congestion potentially involves the Azygous and spinal vein systems. Bowdino, Owens and Shaw (40) describe that in 3% of people, the retroperitoneal venous vessels, such as lumbar or hemiazygos vessels, drain into the right renal vein before it enters the inferior vena cava
· The Azygous system of veins, which includes the hemiazygous and accessory hemiazygous veins provide an alternative blood flow from the lower half of the body to the superior vena cava was recognized by Nicolaides et al as significant in their work on venous outflow abnormalities and MS (37) and explored by Scholbach.(39) This, and its association with the vertebral venous system has a place in POTS pathogenesis, but as yet this has not been fully elucidated. Symptoms occasionally can only be explained by dysfunctional azygous flow, but again we have no evidence to confirm this.
With almost all of the head and neck-driven causes, the impact of posture, trauma, lifestyle, hypermobility usually comes down to the inter-relationship of the neck to the Thoracic Outlet Syndrome.
Thoracic Outlet Syndrome
Thoracic outlet syndrome (TOS) is not the name of a single entity, but rather a collective title that encompasses a variety of conditions produced by compression of nerves, arteries and or veins (or all) because of an inadequate passageway through an area (thoracic outlet) between the base of the neck and the armpit. The thoracic outlet is bordered by the scalene muscles, first rib, and clavicle. Figure 1: Thoracic Outlet Syndrome
Source: http://sportmedschool.com/thoracic-outlet-syndrome/ (22)- an excellent resource of information for clinician.
Kjetil Larsen describes “TOS is considered to be one of modern medicine’s most difficult issues, because of the complex and variable nature of its symptoms. It has potential to cause numerous types and areas of pain, such as neuralgia in the arms, chest, between the shoulder blades and in the back (figure 1), dizziness, brain fog, migraine, headaches, a feeling of being “heavy-headed”, etc.” “(1)
“The reason why the potential symptoms are all over the spectrum, is because it in addition to compression of the entire brachial plexus nerve network which innervates the arms as well as parts of the chest, neck and back, also may compress the subclavian artery & vein. A branch of the subclavian artery include a key vessel, the vertebral artery. The vertebral artery supplies the brain with blood, and is therefore especially important to assess for symptoms of vertebrobasilar insufficiency. It has also been shown that TOS may cause secondary dysautonomic symptoms.”(1)
Shoulder disorders, which include unspecific shoulder pain and specific disorders, are commonly diagnosed in primary care and often lead to prolonged disability. Their 12-month prevalence in the population of working age range between 7 to 47% for shoulder pain, depending on the population studied. The impacts for workers are important in industry such as in office, especially for chronic shoulder pain.(19)
“Although neck and arm pain is a frequent presenting complaint in the general population, the controversial and difficult to diagnose Thoracic Outlet Syndrome should always be considered especially if the risk factors and occupational situations associated with it as assessed. The neurogenic forms are by far the most frequent as they represent more than 95% of all cases of TOS, and these can be classified in the “true” neurological form associated with neurological deficits (mostly muscular atrophy), and painful neurological forms (with no objective neurological deficit). These painful forms are very frequent, especially when patients are systematically screened for these symptoms. The existence of these forms of TOS remains controversial in part because muscular and neurological manifestations are strongly interrelated.”(19)
Christo (20) describes “ Nearly all cases of TOS (95%) are neurogenic in origin. NTOS is an underappreciated and often overlooked cause of shoulder and neck pain and numbness. True NTOS which is confirmed with objective findings accounts for only 1% of cases, whereas common NTOS, which has symptoms suggestive of brachial plexus compromise with no objective findings makes up 99% of cases. The remaining cases of TOS are arterial (1%) and venous (3-5%)” (20)
“Neurogenic TOS occurs in an estimated 3 to 80 per 1,000 individuals, the wide range reflecting the lack of confirmation in many patients with signs and symptoms indicative of the condition. Women with NTOS outnumber men by 3 to 4:1. The syndrome is particularly common in people who perform repetitive tasks with their upper extremities, such as violinists, data entry personnel, and workers on assembly lines. Athletes with repetitive overhead arm motion, including volleyball players, swimmers, baseball pitchers, and weightlifters, also are at increased risk, as are people who have experienced neck trauma.”(20)
Any condition that results in enlargement or movement of these tissues of or near the thoracic outlet can cause the thoracic outlet syndrome. Other risk factors include shoulder trauma, occupations or sports that involve heavy usage of the upper extremities against resistance, including jack-hammer operators and dental hygienists, weight lifting, pregnancy, poor posture and obesity. Rarely, lung tumours can affect the outlet.
“Histologic studies suggest that injury to either the anterior scalene muscle (ASM) or the middle scalene muscle are the main causative factors of NTOS. Muscle fibrosis is a prime finding on examination of excised scalene muscles, with NTOS patients having 3 times as much scar tissue as unaffected subjects. The ASM derives from the transverse processes of the C3-C6 vertebrae. The muscle, which attaches to the first rib, serves as an accessory muscle of respiration, and also rotates the neck slightly. Spasm of the ASM puts traction on the brachial plexus and causes oedema of the muscle and nerves, which, in turn, limits the space of the outlet. Development of scar tissue and fibrosis of the ASM further worsen neural compromise and perpetuate pain.”(20)
Thoracic outlet syndrome symptoms include neck, shoulder pain, arm pain, numbness and paraesthesiae (pins and needles) fingers and impaired circulation of the extremities (so there may be for example, discolouration of the hands.) Symptoms can be constant or intermittent depending on what activities are being performed.
“Painful neurological forms of TOS account for 97% of all cases of TOS according to Roos.(21) They are typically responsible for symptoms in the C8-T1 distribution (medial aspect of the arm, ulnar border of the forearm and hand), but the C7 nerve root and sometimes the superior trunk of the brachial plexus (C5-C6) may be responsible. Clearly systematized symptoms are rarely present.”(19)
“It has been reported that the 3 most disturbing preoperative symptoms are pain at rest (87% of cases), feeling of numbness (66% of cases) and decreased strength (55% of cases). In practice, the patient often reports vague, poorly defined, and inconsistent symptoms, but clinical interview often reveals difficulties during activities requiring elevation of the arms (hanging up the washing, brushing one’s hair, etc.).”(19)
“Functional impairment and pain related to carrying heavy loads are frequent but less specific. Pain of the neck and shoulder region is at least partly due to muscle imbalance but can sometimes be due to a proximal form of TOS (C5-C6). Decompensation fairly frequently occurs after a change of job or in a context of carpal tunnel syndrome (double crush syndrome). These patients present with complex upper limb pain. Carpal tunnel symptoms appear rapidly due to pre-existing irritation of the nerve fibres by TOS.
However, the pathophysiology of the association between upper-limb distal nerve entrapment and TOS is complex, and may not be only on irritation of nerve fibres. For instance, median nerve sensory fibres do not travel with the C8 fibres that are being hypothesized as the site of the double crush. Therefore, other mechanisms could be considered in relationship to increase median or ulnar nerve pressure and scalene muscle activity, or a hypothesis of centralization of pain. The associated TOS must be identified, as it can be responsible for persistent symptoms after treatment of carpal or ulnar tunnel syndrome.”
“Apart from double crush syndrome, other secondary painful diseases may be associated, such as epicondylar pain secondary to medial or lateral insertion tendinitis. However, referred pain is not always easy to distinguish from a possible associated tendinitis (medial aspect of the elbow, which also raises the problem of the real (or at least the initial) cause of the pain . Nevertheless, some of these forms of medial or lateral epicondylitis may resolve in response to rehabilitation for TOS.”(19)
Arterial / Vascular TOS
Larsen explains “the most common symptoms of arterial and/or venous TOS are:
• Dizziness / vertigo
• Suboccipital, or mastoidal pain and pressure
• Migraine and/or headaches
• Cold hands and arms
• Feeling “heavy-headed” or as if wearing a tight helmet
• Difficult to concentrate/brain fog
• Fatigue
• More rare; ischemia of the arm or hand
• Also rare; swelling
Most of these symptoms may have several other potential causes, which is why you need to do a probability estimate of whether thoracic outlet compression may be involved or not. One factor that often holds true, is visible increase of pressure in the external jugular vein. This is almost always caused by tightness of the SCM and scalenes, and/or depression of the clavicle (we now know that these two often go hand in hand), as it compresses the subclavian artery and thus compromises these structures.”(1)
“Despite more than 2600 references to TOS on PubMed, there is still wide controversy regarding TOS; no concrete diagnostic criteria have been established, and many practitioners claim that the whole problem is a fad which does not really exist.” (1)
Figure 2: Referred Pain Patterns
Source: Kjetil Larsen. How to truly identify and treat thoracic outlet syndrome (TOS). 2017
“The name thoracic outlet syndrome suggests chronic irritation (compression) of the brachial plexus and the subclavian vessels. Due to continuous compression within spaces that the nerves and vessels pass through. The cause of the compression is mainly tightness of the surrounding muscles and clavicular depression, strangulating the thoracic outlet vascular and nervous structures.”(1)
Figure 3: Mechanism of Thoracic Outlet Syndrome
Source: Kjetil Larsen. How to truly identify and treat thoracic outlet syndrome (TOS). 2017
“In turn, the main cause of the muscle tightness and clavicular depression, is faulty movement and postural strategies. This can be rooted in habits alone, or triggered by injuries such as a clavicular fracture, whiplash injury or similar. Slouching of the neck (forward head posture) and shoulder, belly-(only)-breathing and lack of diverse movement will cause the scalenes that form the interscalene triangle of which the brachial plexus pass through, to inhibit/deactivate. This in turn may cause severe tightening of the scalenes, compressing all of the thoracic outlet’s structures and may thus (potentially) cause all of the initially mentioned symptoms.”(1)
“The (anterior and medial) scalenes are involved in many actions. They elevate the ribs during inspiration (inhalation), ipsilaterally rotate, cause lateral translation, laterally flex and forward flex (bend) the neck. In normal breathing patterns, the ribs and clavicle should elevate slightly during inspiration, and this is done in syncronization by the scalenes, trapezius and several other muscles. Severe slouching habits will inhibit this pattern as well as proper cervical (axial) rotation, causing degeneration of the involved muscles. In turn, severe inhibition of the scalenes will often develop over time.”(1)
“Because the trapezius muscle holds the scapula and clavicle, the loss of optimal function of this muscle will cause chain reactions of muscular inhibition down the line (arm), creating the potential for several nervous and vascular entrapment points, such as the triangular interval in the posterior shoulder. This is especially important when there is pre-compression within the scalenes and costoclavicular passage, as this sensitize the whole nervous chain and make the distal branches more vulnerable to additional irritation.”(1)
“Additionally, because the scalenes attach to the ribs, they may elevate the first rib, greatly increasing the potential of secondary compression between the 1st rib and the clavicle. Compression within the scalenes often attribute to between 60-80% of the patients’ direct symptoms in my experience; a considerable amount.”(1)
Costoclavicular Syndrome
Costoclavicular syndrome is a component of the Thoracic outlet syndrome. This was first described in in 1942 in soldiers with loaded backpacks who developed pain, numbness and arm fatiguability as they stood at attention, and results published in 1943.(2) “The mechanism of compression involved downward movement of the clavicle against the first rib, with a resultant tendency to shearing of the neurovascular bundle.”(3) This same mechanism was thought to explain subclavian vein thrombosis precipitated by prolonged heavy exercise of the upper extremities- Paget-Schroetter Syndrome. De Silva then described the same mechanism occurring in heavy breasted women with tight bra straps again shearing the neurovascular bundle. Peet et al formalized the diagnosis in 1956.(16)
Larsen describes: “Costoclavicular syndrome is such a common problem with a wide spectrum of possible consequent problems. The most common symptom of mild compressive brachial plexopathy is upper back pain, especially dorsal scapular nerve pain. This is frequently misdiagnosed as thoracic facet joint problems or rhomboid myalgia. As the problem amplifies, usually due to a combination of stress and poor posture, but also head and neck injuries, then fulminant arm, chest and neck symptoms can occur as well. In aggressive cases, paresis of several myotomes or even the entire arm can develop. This is also known as "Rucksack palsy", but really, it is costoclavicular syndrome. “
TOS association with Cervical Plexus entrapment
Larsen describes: “Cervical plexus entrapment is a very little known, but somewhat common comorbidity in thoracic outlet syndrome. The cervical plexus is comprised of C1-4 nerve roots, and mainly carry sensory functions. The cervical plexus itself can become entrapped between the middle scalene and levator scapula muscles, and in these cases, symptoms will usually trigger either with [excessive] stimulation of the scalenus or levator scapula. This can be hyperventilation, heavy carrying and working overhead, or especially horizontal pushing. The cervical plexus can also be symptomatic in the absence of direct stress, meaning that its symptoms are mainly invoked by stress exerted on the brachial plexus.
Symptoms of cervical plexus entrapment are neck and throat tightness, ear pain, mastoidal pain, occipital neuralgia (may implicate any of the three different occipital nerves: The greater occipital, lesser occipital and 3rd occipital nerves), supraclavicular pain, and of course, generalized neck pain.
The suboccipital symptoms in TOS are usually vascular, and as such, hypertensive migraines. But some patients suffer from legitimate neurogenic suboccipital symptoms in TOS, and these will respond favourably to a nerve block, whereas the vasculogenic one will not.”(1)
“The brachial plexus directly anastomoses with the sympathetic chain, and in aggressive cases, strange dysautonomic symptoms and sympathalgias can occur.
Urschel et al., and other authors as well, have published tendencies of pseudoangina, tremors, CRPS and other unexpected and seemingly strange outcomes of brachial plexopathy.
The key to diagnosis in these cases, first and foremost, is to determine whether or not costoclavicular activity ("arm loading") instigates the patient's strange symptoms. The next step would be trialling with costoclavicular decompression.”(1)
Normal management involves physiotherapy as the mainstay of treatment, focused on improving posture, strengthening the shoulder girdle muscles, and stretching exercises to relieve compression.
Figure 5: The Brachial Plexus
Source: Larsen, K. Costoclavicular Syndrome. 2023. Facebook post.
Figure 5: The Cervical Sympathetic Chain
Source: Larsen, K. Costoclavicular Syndrome. 2023. Facebook post.
Neural sensitisation
Dovetailing into this concept of neural sensitivity is the increasing realization of glial hypersensitization causing the pain of Fibromyalgia Syndrome (FMS), and characteristic of POTS and its autonomic chaos. FMS is characterized by widespread musculoskeletal pain, fatigue and cognitive difficulties. Central nervous system sensitization is a major component where various external stimuli eg infection, trauma and stress contribute to symptoms. The pain is neuropathic in nature, with changes in dermal unmyelinated nerve fibre bundles, while myelinated fibres are not affected.
FMS has been “linked to inflammatory reactions and changes in the systemic levels of pro-inflammatory cytokines that modulate responses in the sympathetic nervous system and hypo-pituitary-adrenal axis”. Mendieta et al found higher levels of IL-6 and IL-8 than in healthy volunteers, and these 2 interleukins were 2 of the most constant inflammatory mediators in fibromyalgia, with levels corresponding to the severity of fibromyalgia symptoms, and that IL-6 and IL-8 could have additive effects in the continuous pain in fibromyalgia. (13)
Coronavirus disease 2019 (COVID-19) is the greatest public health crisis in the early 21st century. Its causative agent, Severe Acute Respiratory Syndrome (ARDS) coronavirus 2 (SARS-CoV-2), is an enveloped single stranded positive-sense ribonucleic acid virus that enters cells via the angiotensin converting enzyme 2 receptor or several other receptors. While COVID-19 primarily affects the respiratory system, other organs including the brain can be involved. (49)
SARS-Co-2 activates threat receptors, or Toll-Like Receptors (in particular TLR2 and TLR4 where mutations have been found,) triggering a dysfunctional immune response provoking the excessive cytokine storm with interleukin 6 (IL-6) and tissue necrosis factor alpha (TNFα) that sensitise microglial cells with consequent small-fibre neuropathy which in turn causes autonomic instability and other neuropathic symptoms.(50)(51)
Inflammatory microglial activation (IL-6 and TNFa) is the most common brain pathology found in patients who died of COVID-19: 42% are affected, and another 15% have microclots in brain tissue.(52) Dong et al (24) demonstrated that brain inflammation plays a critical role in the pathophysiology of brain diseases. Microglia, the resident immune cells in the brain, play an important role in brain inflammation, while brain mast cells, rather than microglia, are the "first responders" to brain injury. They showed that site-directed injection of a “mast-cell degranulator” compound in the hypothalamus initiated the acute inflammatory response by inducing mast-cell degranulation, activating microglia, and triggering the production of inflammatory factors.
Microglia are a type of neuroglia (glial cell) located throughout the brain and spinal cord. Microglia account for 10% to 15% of all cells found within the brain. As the resident macrophage cells, they act as the first and main form of active immune defence in the CNS.
The consequence of the microglial sensitisation that causes small fibre neuropathy is abnormal functioning of the autonomic nervous system, that controls everyday body activities- autonomic dysfunction or dysautonomia. Symptoms of this include: lightheadedness, presyncope, abnormal heart rhythms, shortness of breath, dry eyes, loss of saliva, temperature dysregulation, excessive sweating, constipation or diarrhoea, nausea, unexplained anxiety, abnormal bowel and bladder function, and other symptoms.(44) Many have a “cross-over” with mast cell activation (47)(48) and mechanical effects on the vagus, brainstem, sympathetic ganglia and other areas.
The complex nature of the immune response and mast cell activation in now an integral part of Long Covid pathogenesis. The same microglial activation has been demonstrated in other conditions -CFS (43), ADHD (45), migraine, Fibromyalgia syndrome (43) and Endometriosis (46).
Thrombosis and microemboli from the Subclavian, Internal Jugular and Axillary veins
Thrombosis of the subclavian and axillary veins have been associated with pulmonary emboli, just as popliteal vein compression is a cause of DVT and pulmonary emboli. In the migraine research from Drs David Grosser and Ross Sharpe, they found microemboli from the occluded popliteal veins in the legs can pass through a Patent Foramen Ovale (PFOs) to affect the brain, and the same risk is present from the TOS vein compression.(5) In recent research from USA looking at people seen at emergency departments after syncope or sudden collapse, 20% have been found to have had pulmonary emboli.(6)
Dyspnoea in patients with known chronic obstructive pulmonary disease (COPD) can be a clinical challenge due to the nonspecific nature of atypical presentations. Typical features of fever, productive cough, and wheezing on presentation support COPD exacerbation, while absence of such findings may warrant further evaluation for underlying aetiologies, including pulmonary embolism (PE). It is suspected that one in four patients with atypical COPD exacerbation may have PE as an underlying or concomitant cause of acute dyspnoea.(7)
The very real risk of microemboli and emboli from occluded subclavian veins in the thoracic outlet plays an important role in the cause of “unexplained” pulmonary emboli, as an underlying cause of “asthma” where adequate investigation has not been performed, in emphysema, idiopathic pulmonary hypertension, and probably disease such as sarcoidosis.
The lungs should filter out any microscopic emboli from the compression areas, unless a PFO is present. I strongly suspect many of the people with “asthma” not confirmed on formal lung function testing, sometimes presenting at emergency departments with chest pain and shortness of breath, have had microscopic embolic cascades. In persisting chest pain and shortness of breath after Covid, microemboli are a real concern that is commonly ignored.
In other patients it appears to be a cascade of inflammatory cytokines rather than microemboli, although any microembolic phenomena would also produce an inflammatory response. Sometimes there is a positive D-Dimer test suggesting a pulmonary embolus, but with no sign of DVT or embolus in VQ lung scans, the usual tests, they are discharged. These findings are common in Long COVID.
Researchers are now looking at “microtrauma” in blood vessels, and that concept is very appealing to me, with particular importance for unexplained chest pains (also from cascades of catecholamines and cytokines, and simple nerve compression at the axillae. With the evolving concept of microembolic and inflammatory cause of cardiovascular disease (MINOCA) it is highly probably TOS will be shown to have a significant role. It all becomes very murky and complex, but does allow a path to recovery from the problems by addressing the mechanical issues, certainly until we have clear confirmation of the exact pathogenesis of the diseases. Another area of clear association we have found is in aortic arch dilatation. Our research has shown this problem to have a very high association with TOS and sportsmen.
Myofascial Pain Syndrome (MPS)
Complicating the issue is the presence of myofascial pain where the fascia that surrounds the muscles is affected, most notably with the trigger points where muscles fibres that when compressed is painful and can give rise to referred pain elsewhere and is associated with motor dysfunction and autonomic changes. Trigger points might be “active” or “latent.” An active trigger point is always sore and can prevent the full use of the muscle, leading to weakness and decreased range of motion. A latent trigger point does not cause pain during normal activities, but is tender when touched and can be activated when the muscle is strained, fatigued, or injured.
Other authors look at the syndrome as “Scalene Myofascial Pain,” where patients present “with unilateral neck and shoulder pain associated with typical referred pain in the radial distribution of the affected arm/hand, simulating C6 radicular pain. When the referred pain is due to MPS of the scalene muscle, the referred pain and numbness can be due to brachial plexus irritation as a result of direct compression between two scalene muscles. This phenomenon justifies the established fact that MPS of the scalene muscle is one of the causes of TOS.” (17)
The cause of myofascial pain syndrome is uncertain in traditional medical literature. Causes appear to include mechanical factors — such as having one leg longer than the other — poor posture, stress, and overuse of muscles. Exercising or performing work activities using poor techniques can also put excessive strain on muscles seem most likely. Prior injury, poor sleep patterns, stressful life situations, and depression are common underlying conditions that may play a role in inciting and exacerbating myofascial pain syndrome. It is currently felt that risk factors such as these may lead to a change in the ability of the brain to properly process pain perception, but it implicates the linking with the autonomic changes that are found in TOS.
The close association between adhesive capsulitis (frozen shoulder) and TOS is most likely associated with autonomic changes associated with this. There is a high association between TOS, myofascial pain and fibromyalgia. It becomes an esoteric discussion what label is applied as long as the mechanical causes and physical signs are identified and other pathology excluded.
Population studies
As yet we have simply no idea of what percentage of compression is in the normal population – in arm movements it must be said that venous compression is probably a normal occurrence. In the very biased population of migraine, fibromyalgia, POTS and auto-immune patients seen at this clinic, TOS of various types is found in around 80+ % of patients.
Rodante et al identified a myofascial component of pain in 30% of all patients, and up to 95% at a chronic pain centre.(15) It is quite likely that this myofascial component accounts for the bulk of the neurogenic symptoms, and as traditional investigations such as nerve conduction studies are normal, the diagnosis is missed.
Sport Specific Biomechanics
Thoracic outlet syndrome is most often seen in patients who engage in repetitive motions that place the shoulder at the extreme of abduction and external rotation. An example of such activity is swimming, especially with the freestyle, butterfly, and backstroke. When a swimmer reports tightness and pain around the shoulder, neck, and clavicle as his or her hand enters the water, thoracic outlet syndrome should be suspected. Other athletes affected include water polo, baseball, and tennis players and athletes in any other activity that places repetitive stress on the shoulder at the extremes of abduction and external rotation. It is also found in musicians, waiters and others working above their shoulders.
Povlsen and Povlsen (14) describe “It is becoming increasingly recognised that high-level repetitive physical activity involving the upper extremity may put individuals at risk for development of thoracic outlet syndrome. Indeed, in one centre >40% of patients requiring first rib resection and scalenectomy for NTOS relief were competitive athletes. This risk also appearsto extend to the vascularsubtypes of TOS, where such events may be antecedents for effort-induced thrombosis. Although cases of thoracic outlet syndrome in musicians have been documented, until now it had not been rigorously studied.
Povlsen and Povlsen (14) evaluated 64 high-performance string instrument musicians and 52 healthy age-matched controls. They found positive elevated arm stress test (EAST) or upper limb tension test (ULTT) in 44% of musicians compared with 3% in the control group. Abnormal ultrasound scan with vascular compressions was detected in 69% of musicians versus 15% of controls. Interestingly, they also noted abnormal ultrasound scans with vascular compression were more commonly noted in violinists and viola players than cellists.
Furthermore, in violinists and viola players, the left arm, which is elevated to hold up the instrument, was more commonly affected than the right bow-holding hand. This underscores the theory that it is the overhead repetitive-strain aspect of these activities that predisposes to thoracic outlet syndrome.”(14)
Illig and Doyle (8) write: “the subclavian vein is highly vulnerable to injury as it passes by the junction of the first rib and clavicle in the anterior-most part of the thoracic outlet. In addition to extrinsic compression, repetitive forces in this area frequently lead to fixed intrinsic damage and extrinsic scar tissue formation. Venous thoracic outlet syndrome progressing to the point of axillo-subclavian vein thrombosis, variously referred to as Paget-Schroetter syndrome or effort thrombosis, is a classic example of an entity which if treated correctly has minimal long-term sequelae but if ignored is associated with significant long-term morbidity.”
Management
Surgery in cases of thoracic outlet syndrome is indicated for acute vascular insufficiency and progressive neurologic dysfunction. Neurological symptoms may persist in patients following surgery to remove the first ribs, thus freeing the venous compression, but scarring of the nerves that envelop the vessels may cause prolongation of symptoms after surgery.
Increasingly botox into the scalene muscles is being used as a diagnostic tool in this sub-group of patients , and increasingly literature suggests it may be effective as a therapeutic one. It is being used primarily in neurogenic TOS, and as yet I can find no use in venous TOS, so I await responses to botox trials when used in mixed forms of TOS. John Hopkins provides a useful graphic to demonstrate the surgical and botox procedures, although I feel the site presents an overly-glowing presentation-https://www.hopkinsmedicine.org/heart_vascular_institute/vascular-surgery/our-specialties/thoracic-outlet-syndrome/index.html
Physiotherapy focuses on pain control and range of motion with specific stretching exercises that addresses postural abnormalities and muscle imbalance relieves symptoms in most patients with thoracic outlet syndrome by relieving pressure on the thoracic outlet. Once pain control and cervical motion are regained, strengthening exercises of the lower scapular stabilizers are begun, as is an aerobic conditioning program. When surgery is performed, best results do appear to be in those where appropriate physiotherapy is undertaken.
Postural correction focuses on positions of most risk and least risk for compression, with integration into the patient's activities of daily living at work, home, and sleep. In addition, the impact of obesity and general physical conditioning should be assessed.
Treating TOS is not simple, and requires a dedicated physiotherapist or a musculo-skeletal trained physician or suitable other therapist. The work described by Kjetil Larsen in: https://trainingandrehabilitation.com/how-truly-treat-thoracic-outlet-syndrome/ is I believe a step forward to help therapists in other areas where specialized teams do not exist, deal with the complexity of this problem.
References:
1. Larsen,K. How to truly identify and treat thoracic outlet syndrome (TOS). 2017, https://trainingandrehabilitation.com/how-truly-treat-thoracic-outlet-syndrome/
2. Falconer, M., Weddel,G.,Costoclavicular Compression of the Subclavian Artery and Vein. Lancet, 1943: ii: 539-44
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