Thoracic outlet syndrome is a disorder where there is compression of the brachial plexus and blood vessels in the space between the thorax and clavicle bone. It is characterized by pain down the shoulder with tingling, numbness and burning in the compressed nerve distribution down the arm.

Type:

• Neurogenic (most common)
• Vascular

Causes:

• Anatomic predisposition with associated trauma
• Congenital cervical rib or soft tissue band
• Prominent C7 transverse process
• Clavicle or 1st rib abnormalities
• Muscle predisposition include scalene muscle abnormalities that include muscle hypertrophy, abnormal muscle position, intra-muscular brachial plexus entrapment or accessory scalenus minimus muscle
• Space occupying lesions (example include a Pancoast tumour)
• Aggravating factors include pregnancy

Risk factors:

• Weight gain
• Muscle thoracic hypertrophy
• Pregnancy with fluid retention

Potential compression sites for thoracic outlet syndrome.

Presentation:

• Pain in neck/chest/shoulder/arm
• Tingling and numbness and burning
• Heaviness in arm while doing overhang arm activities
• Vascular manifestations include cold limb with skin discoloration, swelling and venous distension
• Chronic obstruction manifestation include: arm claudication, coldness and pallor

Examination:

• Assess skin changes
• Assess limb for microembolic metastasis and ischaemia that include nail and hair changes
  • Vascular assessment: Vascular obstruction with arterial bruits
• Clinically provocative entrapment tests: Adson, Wright, Roos tests

Risk factors:

• X-rays/CT of Chest/Neck will reveal extra rib.
• Nerve conduction studies: signs of chronic partial denervation of intrinsic hand muscles with decreased amplitude of evoked potentials of the Ulnar nerve and motor evoked potentials of the Median nerve. Electroneuromyography (ENMG) reveals abnormal signal pattern in severe cases with a reduction in velocity in permanent nerve compression. Electrodiagnostic testing useful to exclude nerve compartment syndromes.
• MRI: demonstrate fibrous band connecting spine to rib, vascular compression.
• Static and dynamic vascular examinations include doppler ultrasound and angiography: useful when vascular signs are present.

Compression for 30 seconds to trapezius and anterior scalene muscles reproduces arm pain and paraesthesia.

Technique:

• First step: patient head held straight forward while arm in abduction and external rotation to 90.
• Elbow flexed to 45 and arm held for 1min and examiner measures the radial pulse.
  Second step: Examiner monitors the quality of the radial pulse with arm in extreme adduction position
• Positive test: A decrease in radial pulse with pulse absence and/or reproducible pain/paraesthesia.

Wrist test:

• Bring shoulder to abduction with elbow at 45 ° flexion for 1min.
• Then palpate radial pulse in extreme adduction position.
• + test: reduction in radial pulse ± pain/paraesthesia reproduced.

Technique:

• Seated patient with arm in slight abduction and external rotation with forearm supinated and elbow extended. Radial pulse is assessed.
• Patient then maximally extends and laterally rotates the neck towards the tested side and inhales and holds a breath.
• Positive test: reduction or loss in radial pulse or reproduction of pain and/or paraesthesia.

Adson test:

• Bring shoulder to abduction with elbow at 45 ° flexion for 1min.
• Then palpate radial pulse in extreme adduction position.
• + test: reduction in radial pulse ± pain/paraesthesia reproduced.

Technique:

• In a seated position, abduct and external rotate shoulder bilateral to 90° with elbow flexed to 90°.
• Perform task by opening and closing hands for 3mins.
• Positive test: Reproduction of pain and/or paraesthesia.

Roos test:

• Keep shoulders/elbows in 90 ° abduction and flexion respectively.
• Open and close hands for 3 mins.
• + test: reproduction of arm pain/paraesthesia.

Conservative

• Avoid aggravating factors
• Medication such as pregabalin (Lyrica) may help with neuralgia pain
• Nonsteroidal anti-inflammatory medication
• Administration of anesthetic agents, steroids and Botulinum toxin type A (BTX-A) injections
• Rehabilitation: strengthening and stretching exercises of the shoulder with improving range of motion and core stability of the structures surrounding the thoracic chest/shoulder girdle area
• Anticoagulation is a consideration in select cases where there is a risk of thromboembolism

Surgery include thoracic outlet syndrome decompression

• For intractable syndrome not responsive to conservative measures
• Release of entrapped nerves and blood vessels

Surgical approach include the supraclavicular, infraclavicular or transaxillary approaches.

Surgery options:

• Removal of extra rib
• Excision of fibrous band
• Muscle release

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4. Thoracic outlet syndrome: definition, aetiological factors, diagnosis, management and occupational impact. J Laulan, B Fouquet, C Rodaix, P Jauffret, Y Roquelaure, A Descatha. J Occup Rehabil. 2011 Sep;21(3): 366-73.