Preliminary Diagnosis: Thoracic Outlet Syndrome

I. What imaging technique is first-line for this diagnosis

Cervical plain radiography should be obtained first to rule out pertinent bone abnormalities, followed by Magnetic resonance imaging (MRI) without contrast performed with maneuvers (arm in neutral and elevated positions).

II. Describe the advantages and disadvantages of this technique for diagnosis of thoracic outlet syndrome.

Cervical plain radiography
Advantages

  • Excellent demonstration of bony abnormalities.

  • Inexpensive.

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  • Quickly performed.

Disadvantages

  • Exposure to ionizing radiation.

  • Does not characterize the soft tissues well.

Magnetic resonance imaging (MRI) without contrast performed with maneuvers
Advantages

  • Demonstrates the anatomical structures of the thoracic outlet well and can demonstrate compression of neurovascular structures.

  • Able to detect muscular hypertrophy of the scalene, subclavius, and pectoralis minor.

  • Can demonstrate venous thrombosis and collateral circulation utilizing time of flight imaging which does not require contrast.

  • Does not use ionizing radiation.

Disadvantages

  • Expensive.

  • Time-consuming.

  • Requires significant patient cooperation to limit motion artifact.

  • May be a difficult procedure for claustrophobic individuals.

III. What are the contraindications for the first-line imaging technique?

Plain-film radiography

  • No contraindications. However, some institutions may require informed consent for pregnant women.

Magnetic resonance imaging (MRI) without contrast performed with maneuvers

  • Non-MRI compatible embedded devices.

  • Body weight beyond the limit of the table.

IV. What alternative imaging techniques are available?

  • CT/CTA.

  • Ultrasound.

  • Conventional angiography.

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of thoracic outlet syndrome.

CT/CTA
Advantages

  • CT scan with maneuvers may be diagnostic for thoracic outlet syndrome.

  • The use of intravenous contrast is particularly helpful for detecting vascular compression.

  • Relatively quick imaging procedure.

  • Requires minimal patient cooperation.

  • Offers excellent anatomical detail of the thoracic outlet and can characterize the structure causing the compression.

Disadvantages

  • Resolution of the brachial plexus is less than MRI.

  • Patient positioning and maneuvers may not be possible within the limited space of the CT machine.

  • Exposes the patient to ionizing radiation.

  • Has the risk of contrast induced nephropathy or renal failure.

  • Risk of contrast-induced allergic reaction.

Ultrasound
Advantages

  • Patient positioning is not limited by the imaging equipment.

  • No weight limit.

  • May be helpful for characterizing thoracic outlet syndrome when the patient has clinical symptoms, but CT and/or MRI are negative.

  • May be able to diagnose extrinsic compression and structure causing it.

  • Relatively inexpensive.

  • Does not use ionizing radiation.

  • Portable.

Disadvantages

  • Operator-dependent.

  • Resolution is less than MRI or CT.

  • Does not characterize the pulmonary apices and may miss pertinent pathology, such as a Pancoast tumor.

Conventional angiography
Advantages

  • Excellent at detecting underlying vascular compression and/or thrombosis.

  • Diagnostic, but may be therapeutic if direct intraluminal catheter thrombolysis, angioplasty, or stent placement is indicated.

Disadvantages

  • More invasive with higher morbidity, i.e., bleeding, infection, dissection of vessel wall.

  • Does not demonstrate anatomic detail beyond the vessels of interest like CT or MRI.

  • Structure causing the compression is not characterized.

  • Requires use of iodinated contrast.

  • Uses a high dose of ionizing radiation.

  • Expensive.

  • Requires a fluoroscopy suite and interventional radiologist to perform the exam.

  • Sedation is recommended.

VI. What are the contraindications for the alternative imaging techniques?

CT/CTA

  • Contraindicated in patients with known contrast allergy. If absolutely necessary, must be pre-treated with corticosteroids and antihistamines.

  • Contraindicated in pregnant women, especially within the first two trimesters.

Ultrasound

  • No significant contraindications exist.

Conventional angiography

  • Coagulopathy.

  • Pregnancy.

  • Creatinine > 1.6.

  • Allergy to iodinated contrast dye.

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