Thoracic Outlet Syndrome, abbreviatedTOS, describes the compression of the neurovascular structures as they exit a site through the Scalenes and above the 1st Ribs , known as thethoracic outlet. In the vast majority (>90%) of cases, compression is neurological, affecting the Brachial Plexus (SOURCE-3+7+9). TOS is a major pathology of the Thoracic Spine . TOS affects roughly 3-80/1,000 of the general population and is 3-4 times more common in women and usually occurs between the ages of 20 and 50 (SOURCE-9). Compression of the same neuromuscular bundle occurring below the Clavicle is known as Pectoralis Minor Syndrome .
The Thoracic Outlet is marked by three spaces or passageways for the neurovascular structures, each with its own set of potential complications that can narrow the space and cause compression (SOURCE-7+10+11):
Interscalene Triangle- this triangle is defined by the Anterior Scalene anteriorly, the Middle Scalene posteriorly and the medial surface of the 1st Ribs inferiorly. Changes in tonicity of the Anterior Scalene and Middle Scalene or the presence of ascalene minimuscan narrow the passageway
Costoclavicular Triangle- defined by the middle 1/3 of the Clavicle anteriorly, the 1st Ribs posteromedially and the upper border of the Scapula posterolaterally. Compression here can occur as a result of congenital abnormalities or structural changes to the 1st Ribs , Clavicle , Subclavius or Costocoracoid Ligament
Subcoracoid Space- also known as thesub-pectoralis minor space, this passage is defined by the Coracoid Process superiorly, Pectoralis Minor anteriorly and Ribs 2-4 posteriorly. Shortening of the Pectoralis Minor can narrow this space, particularly in extremes of GH Joint - Abduction . This condition is known as Pectoralis Minor Syndrome
The specific neurovascular structures contained within this bundle include (SOURCE-3+5+6+11):
Brachial Plexus - compression resulting inNeurogenic TOS. Symptoms are consistent with other neurological impingements. These symptoms include Pain anywhere between the neck, face and Occipital region down to the chest, shoulder and upper extremity. Also common is altered or absent sensation, weakness or fatigue in the arm or hands. In chronic instances muscle atrophy may develop. In adults Neurogenic TOS most often occurs following muscular trauma, whereas in children it is frequently attributed to anatomic abnormalities such as Cervical Spine or irregular First Ribs , variant Scalenes or Scoliosis (SOURCE-6)
Subclavian Artery and Vein - compression resulting inVenous TOS, which is also referred to asPaget-Schroetter Syndrome. Symptoms include Inflammation / swelling, Pain and discolouration while the affected limb may be described as “heavy”.Venous Collateralsmay also be visible in the Upper Limb or Chest , where venous occlusion causes blood to seek alternative pathways (SOURCE-3+5). Venous TOS is often derived from excessive activity of the Upper Limb leading to hypertrophy of the Subclavius or Costoclavicular Ligament (SOURCE-6). For adolescents activity is typically related to sports participation and symptoms are usually unilateral (SOURCE-6)
Axillary Vein and Artery - compression resulting inAterial TOS. Symptoms are derived from ischemia (reduced blood flow) to the Upper Limb , leading to a cascade which includes claudication, Pain , pulselessness, numbness, coldness and ulcer formation (SOURCE-3+6). Aetiology is often attributed to congenital deformities such as Cervical or anomalous First Ribs , variant Scalenes or Scoliosis (SOURCE-6)
In all three spaces, the Brachial Plexus (>90%) is the predominant structure that is compressed; however, venous (5%) or aterial (1%) obstruction may occur (SOURCE-3). A variation of additional Subclavius fibres, known as theSubclavius Posticus, has also been implicated in Proximal Thoracic Outlet Syndrome (SOURCE-2).
The following pathologies are related to Thoracic Outlet Syndrome:
The majority of Thoracic Outlet Syndrome cases occur concomitantly with Pectoralis Minor Syndrome (SOURCE-4)
Cervical Spine Ribs - the rare variant where ribs originate from C7 is highly associated with TOS, occurring in almost 30% of cases (SOURCE-6)
Trapezius - both insufficiency and excessive tone/size of the Trapezius has been described to encroach on the Thoracic Outlet and increase pressure on the contained neurovascular structures, leading to the TOS. Upper Trapezius insufficiency may cause the shoulder to depress which can structurally imdede on the outlet (SOURCE-7). Conversely, with the attachment of the Upper fibres on the Distal Clavicle (a border of the outlet), hypertonicty and/ or hypertrophy may lead to a superoposterior pull which hypothetically narrows the Costoclavicular Space of the Thoracic Outlet (SOURCE-8)
The following observations may be related to Thoracic Outlet Syndrome:
Reduced Cervical Spine Lordosis
Poor Grip Strength
Muscle Atrophy along nerve distribution - seen in chronic cases
Radial and Ulnar Pulse examination is integral for ruling in/ out arterial compromise. Results may be more significant in certain positions such as with the arm overhead as this can narrow the neuromuscular passage (SOURCE-2)
Arm size - the symptomatic arm should be compared in size to the asymptomatic arm as a disparity indicates Venous TOS (SOURCE-6)
Formation of Dilated Collateral Veins - local to the Chest and Deltoid region suggest chronicity of Venous TOS (SOURCE-6)
Pain - distribution may indicate the Nerve Root heights which are compressed (SOURCE-9):
Arm elevation beyond 90º has the capacity to narrow the thoracic outlet space and consequently exacerbate symptoms (SOURCE-13). This narrowing of space is described to be pronounced in those with a rounded or “poor” posture ( Forward Head Posture , Scapulothoracic Joint - Protraction and an Anterior/ Inferior Shoulder) which is often associated with Thoracic Outlet Syndrome (SOURCE-13).
The following Special Tests may be relevant in the diagnosis of TOS:
Roos Test - provocative test
Adson’s Test - should exacerbate pulselessness
Tinel Sign - tapping of Brachial Plexus near the Clavicle may reproduce Cervical - Pain or Headaches (SOURCE-3)
Assessment of relative tone of the Scalenes and Pectoralis Minor may be relevant as hypertonicity is known to cause compression (SOURCE-4+6). Increased pressure on these muscles may be provocative. This may also help decipher whether symptoms are of PMS or Thoracic Outlet Syndrome origin.
Radiographs (X-Rays) should reveal anomalous or asymmetric Ribs (SOURCE-6). Duplex Ultrasound (B-Mode imaging with colour Doppler) can assist in the diagnosis of Venous and Atrial TOS as it clearly identifies thrombosis of the Axillosubclavian vein (SOURCE-6).
Treatment should always be specific to the aetiology, with conservative treatments typically more relevant in the absence of congenital deformities (SOURCE-6). Exercise therapy has been found to be an effective treatment for 50-90% of those with Thoracic Outlet Syndrome (SOURCE-13). Appropriate positioning and motion of the Scapula is a key point of focus for Thoracic Outlet Syndrome treatment (SOURCE-13).
Stretching techniques have be advocated for Thoracic Outlet Syndrome, in particular of the Scalenes and Pectorals (SOURCE-13):
Door Frame Neck Stretch - Scalenes variation
Door Frame Shoulder Stretch - Pectoralis Minor variation
Seated Thoracic Rotation with Breathing - large lateral flexion and rotation range coupled with breathing
Swimmers Oblique Extensions - exercise that may be used to lengthen entire Lateral Line through large body-wide lateral-flexion range
Crocodile Breathing - promotes Thoracic - Extension with the perturbation of Breathing
Strength training should be focused around posture correction, addressing asymmetries where present (SOURCE-6). Scapula positioning/ movement is a key point of focus regarding exercise selection, with emphasis on alignment of the head and Pelvis (SOURCE-13).
Initial Phase - rehabilitation should begin by promoting muscular endurance of the Scapula stabilisers, in particular the Middle and Lower Trapezius , Rhomboids and eventually the Serratus Anterior (SOURCE-13). Range should initially be restricted between 0-30º GH Joint - Flexion while in 40º GH Joint - Abduction and horizontal adduction should be minimised to avoid perpetuating injury (SOURCE-13):
Scapulothoracic Joint - Retraction
Prone Horizontal Abduction - rudimentary Scapulothoracic Joint - Retraction exercise
Band Pull-Apart - basic isotonic exercise for Scapular Retractors
Scapulothoracic Joint - Depression
Banded Unilateral Lat Activations - activate lat, posteroinferior drawer on Humerus
Shoulder Sling - Scapula setting exercise
Rotator Cuff Pendulums - oscillatory motion that afford a distracting glide to the Humeral Head
Prone Cobra - isometric exercise that emphasises Middle and Lower Trapezius
Standing Shoulder External Rotations - incorporates upright torso posture
Straight Arm GH Joint - Extension
Bird-Dog - bodyweight isotonic exercise that emphasises Posterior Sling / Core
Circumduction Row - isotonic exercise with variable load used to emphasise mid-to-lower Trapezius
Banded High Rows
Mid-Phase:
Inverted Rows - rudimentary isotonic horizontal pull exercise that utilises bodyweight
Front Raises - isotonic GH Joint - Flexion exercise with many variations
Straight Arm Lat Pulldown - isotonic motion that emphasises Lats and straight arm strength
Side Raises - isotonic GH Joint - Abduction exercise with many variations
Lat Pulldown - rudimentary weighted isotonic vertical pull movement with a high range of motion
Scapular Punches - isotonic exercise that emphasises Scapulothoracic Joint - Protraction
Push-Up Plus - push-up variation with additional Scapulothoracic Joint - Protraction
One Arm Row - unilateral DB version of Seated Row
Face Pulls - bilateral isotonic horizontal pull exercise that emphasises GH Joint - External Rotation
DB Pullover - moderate isotonic movement with large overhead and Thoracic - Extension range
Chest Fly - large horizontal abduction range to emphasise lengthening of the Chest
Farmers Carry - upperbody/ Core isometric exercise with perturbation of walking
Late Phase:
Prone Lat Pulldown - Lat Pulldown variation that emphasises Thoracic - Extension
Lu Raises - large GH Joint - Abduction range with no Humerus rotation to promote Scapulothoracic Joint - Upward Rotation
Bottoms-Up Kettlebell Walk - typically isometric exercise for entire arm musculature with perturbation from walking
Pull-Up - bodyweight or greater load through large overhead motion
Suitcase Carry - unilateral farmers carry which emphasises crossbody functional patterns
Massage of the following structures may be indicated in those with Neurogenic TOS:
Fascia - given the aforementioned muscles relevance to TOS, myofascial release along the follow structures may also be beneficial:
The following Mobilisation techniques may be relevant for the treatment of Thoracic Outlet Syndrome:
Joint Play - passive accessory movements performed without active movement
Cervical Spine - Nerve Roots may be treated at their origin using a PACVP , PAUVP or TVP applied to relevant Cervical segment(s) in addition to the following techniques:
Mobilisation with Movement - mobilisations applied with active movement
Shoulder - MWM 1 - applied to the Clavicle and Scapula
Shoulder - MWM 2 - applied to the medial Clavicle and Scapula
Shoulder - MWM 3 - applied to the Scapula and Humerus
Shoulder - MWM 4 - applied to the Scapula and Humerus
Shoulder - MWM 5 - applied to the Scapula and Humerus
Sleeper Stretch MWM - self-guided Posterior Capsule release
Cervical Spine - Nerve Roots may be treated at their origin using the following techniques:
SMWAM - Cervical mobilisations with arm movement
Neurodynamic SMWAM - Cervical mobilisations with neurodynamic arm movement
Cervical SNAGS - Cervical mobilisations with neck movement
NAGS - particularly useful for restriction or Pain associated with movement for C2-C7
Surgical restoration of blood flow through Thrombectomy or Thrombolysis may be indicated for patients with acute thrombosis of the Brachial Artery (SOURCE-6). Surgical decompression of the following structures may also be indicated (SOURCE-6):
Thoracic Outlet - removal of the Anterior Scalene and resection of the First Ribs
Cervical Ribs
Infraclavicular or Transaxillar - indicated for Venous TOS to ensure adequate blood flow is restored to the vein. Transaxillary decompression is also indicated for Aterial TOS where veinous reconstruction is not needed. Where reconstruction is needed an Infraclavicular and/ or Supraclavicular approach is recommended
Anticoagulants are recommended for acute Venous TOS for a minimum of 3 months, usually in conjunction with surgical intervention (SOURCE-6). This medication appears less effective in the young and often provides less benefit when used in isolation (SOURCE-6).
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