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Introduction
  • Overview
    • thoracic outlet syndrome is a neurovascular disorder resulting from compression of the brachial plexus and/or subclavian vessels in the interval between the neck and axilla 
      • treatment may be nonoperative or include surgical decompression or a vascular procedure depending on the specific etiology
  • Epidemiology
    • incidence
      • 1-2% of the population
    • demographics
      • females > males (3:1)
        • tend to be thin with long necks and drooping shoulders
      • age 20-60
    • type
      • neurogenic is most common (95%)
      • vascular may be venous (4%) or arterial (< 1%) 
        • more common in athletic males compared to athletic females
  • Pathophysiology
    • most cases are thought to stem from anatomic predisposition with superimposed neck trauma (acute or chronic repetitive stress)
      • anatomically, can be organized into soft tissue (70%) and osseous (30%) abnormalities
    • soft tissue
      • scalene muscle abnormalities
        • hypertrophy of anterior scalene
        • passage of the brachial plexus through the anterior scalene muscle
          • rather than posterior within the interscalene triangle
        • variable origin and insertion
          • anterior insertion of the middle scalene muscle on the 1st rib
        • scalenus minimus
          • accessory muscle found in 30-50% of patients with TOS
          • originates from cervical transverse process and inserts onto 1st rib between the subclavian artery and T1 root
      • anomalous ligaments or bands
        • fibromuscular bands
          • increase stiffness and decrease compliance of the thoracic outlet
        • costoclavicular ligament
          • abnormal insertion implicated in Paget-Schroetter syndrome
      • soft tissue tumors
        • Pancoast tumor
          • tumor of the pulmonary apex
          • 1-3% of lung cancer cases
            • generally lack typical symptoms of lung cancer (cough, hemopytsis and dyspnea)
        • neuroblastomas
        • schwannoma of the brachial plexus
      • abnormal pectoralis minor
    • osseous
      • cervical rib 
        • occur in < 1% of the population
        • arise from the 7th cervical vertebra
        • four types
          • type 1: complete rib that articulates with the first rib or manubrium
          • type 2: incomplete rib with a free distal bulbous tip
          • type 3: incomplete rib with distal attachment via fibrous band
          • type 4: short bar of bone (millimeters) extending beyond the C7 transverse process
      • prominent C7 transverse process
      • abnormal clavicle or first rib
        • acute fracture displacement
        • hypertrophic fracture callus formation
        • fracture malunion
      • acromioclavicular (AC) or sternoclavicular (SC) joint injury or dislocation
      • osseous tumors
        • bone metastasis to first rib
          • breast, prostate, kidney
        • osteoid osteoma
    • chronic overuse
      • repetitive shoulder use
        • frequent lifting above the level of the shoulder
        • extreme arm positions, including hyperabduction
      • athletes at risk
        • weight lifting
        • rowing
        • swimming
    • vascular
      • repetitive compression over time can result vessel damage
        • aneursym formation
        • thrombosis
        • embolic events
        • limb-threatening ischemia
  • Associated conditions
    • Paget-Schroetter syndrome
      • type of venous thoracic outlet syndrome seen in well-developed young athletes
      • intermittent obstruction of the subclavian vein in the costoclavicular space by
        • abnormal costoclavicular ligament  
        • anterior scalene muscle hypertrophy
      • results in upper extremity deep vein thrombosis
Anatomy
  • Thoracic outlet
    • comprised of three distinct spaces  
    • interscalene triangle
      • proximal space
      • borders
        • anterior: anterior scalene muscle
        • posterior: middle scalene muscle
        • inferior: first rib
      • contents
        • brachial plexus trunks
        • subclavian artery
      • subclavian vein does not pass through interscalene triangle
        • runs beneath anterior scalene muscle prior to entering the costoclavicular space
    • costoclavicular space
      • middle space
      • separated from the interscalene triangle by the first rib
      • borders
        • anterior: clavicle and subclavius muscle
        • posterior: first rib and scalene muscles
        • medial: costoclavicular ligament
        • lateral: upper scapular border
      • contents
        • brachial plexus divisions
        • subclavian artery and vein
    • retropectoralis minor space
      • distal space
      • also known as the thoraco-coraco-pectoral space or subcoracoid space
      • borders
        • superior: coracoid
        • anterior: pectoralis minor muscle
        • posterior: ribs 2-4
      • contents
        • brachial plexus cords
        • axillary artery and vein
Presentation
  • History
    • presentation is very variable
      • ranges from mild pain to sensory changes to severe vascular compromise
      • can be unilateral or bilateral
    • neurogenic
      • pain over the neck, trapezius, chest, shoulder and/or arm
        • 92% of patients endorse trapezius pain
      • upper extremity weakness, numbness and paresthesias
        • distribution differs from other compression syndromes
          • nonradicular nature
            • cervical nerve root compression presents with radicular pain
          • wide anatomic distribution (plexus)
            • isolated peripheral nerve compression (cubital tunnel syndrome, carpal tunnel syndrome) presents with a clear dermatomal distribution
            • involves the lower plexus (C8-T1) or combined (C5-T1) in 90% of patients
        • upper extremity paresthesias occur in 98%
      • upper extremity heaviness
        • particularly with overhead activities
      • symptoms can be activity-related and/or occur at night-time
        • night-time symptoms thought to result from decreased pressure on the brachial plexus with return of sensation manifesting as pain
    • vascular
      • venous
        • episodic cyanotic discoloration and swelling of the limb
          • distended veins
        • diffuse deep pain in the arm and forearm
        • upper extremity heaviness
          • worse after activity
      • arterial
        • unilateral Raynaud-type symptoms
          • episodic coolness and pallor of the limb, followed by cyanosis and ultimately erythema
          • worsens in cold temperatures
          • pain and numbness
          • symptoms tend to predominantly involve the hand (distal circulation)
  • Physical examination
    • inspection
      • note specific postures, can increase loading on the brachial plexus
        • rounded shoulders
        • increased thoracic kyphosis
        • downward rotation or depression of the scapula
      • skin
        • cyanosis, congestion, pallor
        • distal ulcerations, signs of microembolic events (rare)
        • hair distribution
        • nail changes
      • muscle atrophy
        • Gilliatt-Sumner hand
          • characteristic finding of neurogenic TOS
          • atrophy of the abductor pollicus brevis (APB), hypothenar muscles and interossei
    • palpation
      • over the supraclavicular area 
        • may reveal tenderness and/or masses
      • skin temperature
    • provocative tests
      • high rate of false positives
      • supraclavicular pressure test
        • evaluates for compression at the interscalene triangle
        • technique  
          • patient seated with arm resting at side
          • apply pressure to upper trapezius and anterior scalene muscle, squeezing for 30 seconds
        • positive result
          • reproduction of pain or paresthesias
      • Adson test 
        • evaluates for compression at the interscalene triangle
        • technique 
          • patient seated with shoulder slightly abducted and externally rotated, elbow extended, forearm supinated
          • examiner palpates radial pulse
          • patient maximally extends and laterally rotates the neck towards side being tested, then inhales and holds breath
        • positive result
          • reduction in amplitude or loss of radial pulse
            • 51% of normal population has diminished pulse with this manuever
          • reproduction of pain or paresthesias
      • costoclavicular manuever
        • evaluates for compression at the costoclavicular space
        • technique  
          • patient seated with the arm at the side, elbow extended, forearm supinated
          • examiner palpates radial pulse
          • patient retracts and depresses the bilateral shoulders, protruding the chest anteriorly and superiorly ("at attention" stance)
          • examiner extends the shoulder ~30° for 1 minute
        • positive result
          • reduction in amplitude or loss of radial pulse
          • reproduction of pain or paresthesias
      • Wright test
        • evaluates for compression at the retropectoralis minor space
        • technique 
          • patient seated with arm at the side, elbow extended, forearm supinated
          • examiner palpates radial pulse
          • patient laterally rotates neck away from side being test
          • examiner externally rotates and maximally abducts the shoulder, holding the arm above the level of the head for 1 minute
        • positive result
          • reduction in amplitude or loss of radial pulse
            • 7% of the normal population has dimished or lost radial pulse with this manuever
          • reproduction of pain or paresthesias
      • Roos test / elevated arm stress test
        • evaluates the entire thoracic outlet
        • technique 
          • in seated position, patient abducts the bilateral shoulders to 90° with the elbow flexed 90°
          • patient opens and closes the hands for 3 minutes
        • positive result
          • reproduction of pain or paresthesias
            • will often prevent the patient from completing the test for the full 3 minutes
            • normal person have discomfort with this manuever, but are able to complete it
          • resolution of pain or paresthesias with dropping of the arms
      • Cyriax release test
        • evaluates the result of unloading the brachial plexus
        • technique  
          • examiner stands behind patient and grasps the bilateral forearms with the elbows in flexion and forearms in pronation
          • examiner leans against the patient's trunk to passively elevate the shoulder girdle for 3 minutes
        • positive result
          • reproduction of pain or paresthesias
Evaluation
  • Radiographs
    • recommended views
      • chest radiograph and cervical spine radiographs
    • findings
      • cervical rib
      • prominent C7 transverse process
      • low lying shoulder girdle
      • Pancoast tumor
  • CT
    • indications
      • identify osseous space-occupying lesions
      • evaluate malunited fractures of the ribs or clavicle
  • MRI
    • indications
      • evaluate for soft tissue anatomic anomalies
  • Nerve conduction studies
    • EMG and NCV
    • historically thought to be equivocal and unhelpful
      • studies were often normal unless significant permanent nerve damage was already established
    • recently discovered that nerve fibers from C8 and T1 may show early changes in neurogenic TOS
      • abnormal nerve conduction velocities in the medial antebrachial cutaneous nerve and median motor nerve to the abductor pollicis brevis
  • Vascular studies
    • doppler ultrasound
      • helpful for evaluating subclavian vein for obstruction or thrombosis
        • 92% specificity and 95% sensitivity for diagnosis of venous TOS
    • angiography
      • CT or MR angiography
      • arteriography
        • indicated in cases of embolic disease or suspected arterial aneursym
      • venography
        • indicated in work up of suspected subclavian or axillary venous thrombosis
Treatment
  • Nonoperative 
    • activity modification, pain control, physical therapy and modalities
      • indications 
        • first line of treatment
      • technique 
        • activity modification to avoid provocative activities
          • limiting repetitive overhead motion
          • changing employment if necessary
        • pain control 
          • NSAIDs, muscle relaxants
        • physical therapy
          • core and back strengthening, shoulder girdle strengthening, improving posture and relaxation techniques
        • modalities 
          • transcutaneous electrical nerve stimulation
      • outcomes 
        • less successful in 
          • obese patients
          • patients on worker's compensation
          • patients with double-crush neurologic pathology involving the carpal or cubital tunnels
    • anterior scalene blocks
      • indications 
        • neurogenic TOS related to scalene muscule contracture
      • technique 
        • ultrasound-guided lidocaine or botulinum toxin injections
      • outcomes 
        • successful block correlates with 14% higher rate of good surgical outcomes
  • Operative
    • thoracic outlet decompression 
      • indications
        • symptoms that have failed conservative treatment for 6 months
        • progressive muscle atrophy and/or worsening neurologic deficits
      • technique
        • decompression includes a combination of the following depending on etiology
          • first rib resection, anterior and middle scalenectomy, neurolysis
            • most common procedure
            • 95% good outcomes
          • isolated scalenectomy
            • indications
              • upper plexus symptoms
              • absence of abnormal bony architecture
              • excessively muscular or obese patients
              • recurrent TOS following prior first rib resection
          • isolated pectoralis minor tenotomy
            • indications
              • neurogenic TOS with symptoms reproducible to the retropectoralis minor spacw
          • cervical rib resection
          • release of fibromuscular bands
          • costoclavicular ligament resection
          • ORIF of clavicle malunion
    • vascular intervention
      • indications
        • embolic events
        • stenosis with persistent pain and vascular insufficiency
        • subclavian aneursym
        • thrombosis with critical ischemia
      • technique indications
        • heparin IV, +/- embolectomy, +/- local thrombectomy, +/- TPA, systemic anticoagulation
          • acute embolic event
          • small vessel embolism - TPA, systemic anticoagulation
          • large / proximal vessel embolism - embolectomy, systemic anticoagulation
        • endovascular stent placement
          • mild stenotic disease
        • vascular resection +/- primary repair, +/- saphenous vein graft, +/- arterial autograft, +/- synthetic graft
          • subclavian aneursym
          • severe stenosis or thrombosis with critical ischemia
        • vascular bypass
          • chronic emboli with critical ischemia
Technique
  • Thoracic Outlet Decompression
    • approaches
      • transaxillary
        • most commonly used approach
        • pros
          • superior exposure for the first rib resection
          • allows resection of cervical ribs, costoclavicular ligament, fibromuscular bands and scalene muscles
          • access to lower plexus for neurolysis (C7-T1)
          • more cosmetic scar
          • no retraction of neurovascular structures necessary for first rib removal
        • cons
          • risks brachial plexus injury
      • supraclavicular
        • pros
          • superior exposure of upper plexus (upper and middle trunks), scalene muscles, neck of the first rib and vascular structures
            • best approach for isolated scalenectomy and arterial reconstruction
          • allows resection of first rib (but requires significant retraction)
        • cons
          • inferior visualization for first rib resection
            • requries retraction of brachial plexus and vascular structures for complete first rib exposure
      • posterior
        • pros
          • favored for recurrent TOS and in cases of prior neck surgery
          • may allow better exposure of proximal elements of the brachial plexus
        • cons
          • requires extensive muscle dissection that can lead to postoperative shoulder disfunction
          • risks injury to the long thoracic, dorsal scapular and accessory nerves
    • decompression techniques
      • first rib resection, anterior and middle scalenectomy, neurolysis
        • usually performed with combined approach
          • transaxillary: to access first rib and lower plexus
          • supraclavicular: to access anterior and middle scalene muscles and upper plexus
        • specific complications
          • pneumothorax is one of the most common complications of first rib resection
Complications
  • Pneumothorax
    • is one of the most common complications of first rib resection
 

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Questions (1)

(OBQ06.247) A 35-year-old businessman complains of tingling and numbness in his fingers of both hands, mostly in the ring and small fingers, made worse with overhead activity. Neurologic exam and electromyography-nerve conduction study is normal. His cervical spine x-ray is shown in figure A. What is the most likely diagnosis? Review Topic

QID: 258
FIGURES:
1

C5-6 cervical disk herniation

1%

(8/1591)

2

C6-7 cervical disk herniation

3%

(49/1591)

3

Bilateral cubital tunnel syndrome

2%

(27/1591)

4

Bilateral radial tunnel syndrome

0%

(1/1591)

5

Thoracic outlet syndrome

94%

(1497/1591)

ML 1

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