Investigations
1st investigations to order
CXR
Test
Obtained in all suspected types of thoracic outlet syndrome (TOS).[1][108]
Evaluates for bony abnormalities of the neck and shoulder girdle, which are present in 5% to 10% of patients with neurogenic TOS and almost all patients with arterial TOS.
Result
bony abnormalities include: cervical rib, hypoplastic first rib, bridging fusion between first and second ribs, or clavicular deformities
cervical spine x-ray
Test
Obtained in suspected neurogenic thoracic outlet syndrome.
Evaluates for bony abnormalities and degenerative changes in the spine.
Result
bony abnormalities include: kyphoscoliosis, disc disease, arthropathy, previous surgical alterations
electrodiagnostic testing (nerve conduction velocity and electromyography)
Test
Performed in suspected neurogenic thoracic outlet syndrome (TOS) primarily to rule out alternative aetiologies (e.g., carpal tunnel syndrome).[1][4][107]
Nerve conduction velocity measures the ability of nerves to transmit electrical impulses/signals. Electromyography measures muscle electrical activity at rest and during contraction.
Result
usually negative in neurogenic TOS, but may show reduced motor amplitude of the median nerve and reduced sensory amplitudes of the medial antebrachial cutaneous and ulnar nerves in some cases
duplex ultrasonography
Test
Recommended in suspected venous and arterial thoracic outlet syndrome.[1][108]
Evaluates blood as it flows through vessels and can identify venous and arterial thromboses. Best performed both in neutral position and with shoulder abduction.
Also used to confirm thrombosis resolution after treatment.
Limitations include: false-negative rate of 21%, operator-dependent examination.[112][113]
Result
venous thrombus, stenosis, or compression of the subclavian or axillary vein of the affected upper extremity; will show venous patency after treatment, and the presence of complications, such as haematoma or fluid collection; arterial thrombosis, stenosis, or aneurysmal changes
contrast venography, catheter-directed therapy
Test
Venous catheter-directed injection of contrast under fluoroscopy.
Diagnostic standard for detecting venous thoracic outlet syndrome (TOS).
Definitive diagnostic test for venous TOS if clinical suspicion remains high after negative Doppler ultrasonography.
Permits immediate treatment with dissolution or removal of venous thrombus and possible balloon angioplasty if within 6-8 weeks of symptom onset.[79][108]
May be used to assess venous caliber postoperatively.
Result
venous thrombus, occlusion, stenosis, or compression of the subclavian or axillary veins; thrombolysis, suction thrombectomy, and balloon angioplasty help restore a patent axillary-subclavian vein; allows assessment of any residual vein stenosis or compression after clot dissolution/removal; definitive standard for assessment of vein patency after surgical treatment
CT angiography
Test
Recommended if arterial thoracic outlet syndrome is suspected.[1][108]
Intravenous contrast is injected into a contralateral vein and timed with concurrent spiral CT scan to obtain an angiogram.
Evaluates for the presence and location of subclavian or axillary artery aneurysm.
Can demonstrate arterial mural thrombus and/or distal embolism.
Provides anatomical detail regarding adjacent osseous structures that may be contributing to arterial pathology. Best performed both in neutral position and with shoulder abduction.
May be used postoperatively to assess for arterial patency and complications.
Result
arterial aneurysm, thrombus, stenosis, or compression of the subclavian or axillary artery of the affected upper extremity; may demonstrate distal embolism; may evaluate arterial patency after successful thrombolysis or surgical repair and may help detect potential complications (e.g., arterial occlusion, haematoma)
Investigations to consider
MRI neck/clavicle/shoulder
Test
Considered in neurogenic thoracic outlet syndrome to help provide anatomical detail for diagnosing brachial plexus compression sites and preoperative surgical planning.
Non-contrast MRI is typically sufficient, unless a vascular component is suspected. Images are obtained with the patient in both neutral and shoulder abduction positions to best localise the area of impingement.
Result
soft-tissue abnormalities: congenital bands, relative muscle hypertrophy (e.g., well-developed scalenus minimus muscle)
muscle block
Test
Potentially of use in patients with neurogenic thoracic outlet syndrome (TOS), involving imaging-guided local anesthetic injection into the anterior scalene muscle and/or pectoralis minor muscle.[1][116]
Can help reinforce the clinical diagnosis and demonstrate reversibility of symptoms.
Positive scalene muscle block associated with more predictable good outcomes for surgical treatment.
May help distinguish symptoms attributable to neurogenic TOS from those attributable to other conditions (i.e., cervical spine, shoulder).
Result
temporary subjective symptom relief; may also have negative provocative manoeuvres on repeat physical examination during symptom relief window
conventional arteriography
Test
Catheter-directed arterial injection of contrast under fluoroscopy.
Has largely been replaced by less invasive modalities for diagnosis.
Used during catheter-directed therapies (e.g., thrombolysis).
May be used postoperatively to assess for arterial patency, and to diagnose and treat complications.
Result
arterial thrombus, stenosis, or compression of subclavian or axillary artery; arterial patency after successful thrombolysis, or the presence of complications (e.g., dissection or aneurysm formation)
magnetic resonance angiography (MRA)
Test
May identify the cause and severity of arterial thoracic outlet syndrome (TOS), and guide surgical or endovascular management.[108]
May be considered in cases of concurrent neurological TOS when soft-tissue anatomical detail is needed.
Result
arterial thrombus, stenosis, or compression of subclavian or axillary artery; may also show aneurysm formation; concurrent soft-tissue abnormalities may be visualised including congenital bands or relative muscle hypertrophy (e.g., well-developed scalenus minimus muscle)
magnetic resonance venography (MRV)
Test
Indicated in patients who have had symptoms of venous thoracic outlet syndrome (TOS) lasting more than several weeks who are not candidates for contrast venography with catheter-directed therapy.
May be considered in cases of concurrent neurological TOS when soft-tissue anatomical detail is needed.
Result
venous thrombus, stenosis, or compression of the subclavian or axillary vein; concurrent soft-tissue abnormalities may be visualised including congenital bands, relative muscle hypertrophy (e.g., well-developed scalenus minimus muscle)
FBC, coagulation, and thrombophilia studies
Test
Consider in patients with venous or arterial thoracic outlet syndrome (TOS).
Used to evaluate for a hypercoagulable state or thrombophilia, which may influence the type and duration of anticoagulation treatment.[121]
Tests include prothrombin time, partial thromboplastin time, INR, antiphospholipid antibodies, and studies for hereditary thrombophilias such as antithrombin-III deficiency, Protein C deficiency, Protein S deficiency, Factor V Leiden mutation, prothrombin G20210A mutation, and methylenetetrahydrofolate reductase (MTHFR) mutation.
The presence of a thrombophilia or hypercoagulable condition does not necessarily exclude the diagnosis of venous TOS, as both disorders may co-exist.
Result
may suggest an underlying thrombophilia or hypercoagulable state
Use of this content is subject to our disclaimer