Differentiating Thoracic Outlet Syndrome by Type
Thoracic outlet syndrome presents with distinct clinical patterns: neurogenic TOS (95% of cases) causes paresthesias, pain, and weakness in the arm with neck pain and occipital headaches; venous TOS (4-5%) presents with arm swelling, cyanosis, and pain from subclavian vein obstruction; and arterial TOS (1%) manifests with symptoms of arterial ischemia including pallor, arm claudication, and cool extremity. 1, 2
Neurogenic TOS (nTOS) - 95% of Cases
Primary Symptoms
- Upper extremity paresthesias (numbness and tingling) in the arm and hand 2
- Arm and hand pain that is often chronic and positional 2
- Weakness of the affected extremity 2
- Neck pain - a distinguishing feature often overlooked 2
- Occipital headaches - characteristic of neurogenic involvement 2
Physical Examination Findings
- Neck rotation and head tilting elicit symptoms in the contralateral extremity 2
- Upper limb tension test (comparable to straight leg raising) reproduces symptoms 2
- Arms abducted to 90 degrees in external rotation typically brings on symptoms within 60 seconds 2
- The Adson test (radial pulse deficit) has no clinical value and should not be relied upon - it can be positive in asymptomatic controls and normal in most nTOS patients 2
Underlying Pathology
- Most commonly caused by brachial plexus compression from scarred scalene muscles 2
- Neck trauma (especially whiplash injuries) is the most common precipitating factor 2
- Compression occurs most frequently in the costoclavicular space (mostly positional), with rare compression in the pectoralis minor space 3, 4
- Congenital causes include bone variations (36%), fibromuscular anomalies (11%), and positional compression (53%) 4
Venous TOS (vTOS) - 4-5% of Cases
Primary Symptoms
- Arm swelling - the hallmark presentation 1, 2
- Cyanosis of the affected extremity 2
- Arm pain associated with venous congestion 2
- Symptoms often develop with repetitive overhead arm motion 5
Physical Examination Findings
- Visible arm edema on inspection 5
- Blue or dusky discoloration of the extremity 2
- Dilated superficial veins may be present 5
Underlying Pathology
- Subclavian vein compression with or without thrombosis 1, 2
- Repetitive stress leads to vein wall thickening and fibrosis, with restrictive fibrotic tissue surrounding the vein 3
- Intimal damage results in luminal narrowing and a thrombogenic surface 3
- Often presents as Paget-Schroetter syndrome (effort thrombosis) requiring urgent intervention 4
Diagnostic Imaging
- US duplex Doppler is excellent for initial evaluation, showing venous compression during arm abduction 3
- CTV obtained 120-180 seconds after IV contrast demonstrates venous obstruction 3, 4
- Important caveat: Venous compression during arm abduction is commonly seen in both asymptomatic and symptomatic individuals, making clinical correlation essential 4, 6
Arterial TOS (aTOS) - <1% of Cases
Primary Symptoms
- Pallor of the affected extremity 7
- Arm claudication with exertion 7
- Cool arm compared to contralateral side 7
- Symptoms of arterial ischemia including pain with use 7
- Acute limb-threatening ischemia can occur with thrombosis 7
Physical Examination Findings
- Pale, cool extremity on inspection 7
- Diminished or absent pulses (though Adson test is unreliable) 2
- Digital ischemia or gangrene in severe cases from distal emboli 3
- Supraclavicular bruit may be present 7
Underlying Pathology
- Subclavian artery stenosis or aneurysm with emboli 2
- Fixed or dynamic stenosis, aneurysm, mural thrombus, or distal emboli 3
- Cervical rib or anomalous first rib almost always present on x-rays 2
- Arterial changes include intimal damage and thrombosis with risk of distal embolization and aneurysm formation 3
Diagnostic Imaging
- Chest radiography almost always discloses a cervical rib or anomalous first rib 2
- CTA with IV contrast, MRA, or US duplex Doppler are appropriate for diagnosis 3, 4
- Imaging demonstrates arterial stenosis, aneurysm, or thrombosis 3
Key Diagnostic Pitfalls to Avoid
- Do not rely on the Adson test - it has no clinical value and can mislead diagnosis 2
- Do not misdiagnose nTOS as "vascular TOS" - neurogenic is by far the most common type 2
- Do not overlook cervical spine pathology that may mimic or exacerbate TOS symptoms 3, 6
- Do not interpret dynamic venous compression on imaging as pathologic without clinical correlation - it occurs in asymptomatic individuals 4, 6
- Do not miss cervical ribs on imaging in arterial TOS - they are present in nearly all cases 2
Clinical Algorithm for Differentiation
If arm swelling + cyanosis → venous TOS 2, 5
If pallor + cool extremity + claudication + cervical rib on x-ray → arterial TOS 2, 7
If paresthesias + weakness + neck pain + occipital headache + no swelling or ischemia → neurogenic TOS 2