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Arterial TOS Symptoms

Arterial TOS is when the axillary-subclavian artery is compressed within the scalene triangle and the costoclavicular space.  This condition typically involves the presence of a blood clot, aneurysm, and/or damage to the vessel wall leading to physiologic abnormalities of the artery.  A blood clot is a gel-like collection of blood that forms in the veins or arteries when blood changes from liquid to partially solid. A blood clot in an artery carries with it the risk of traveling or spreading clots to smaller arterial branches further downstream.  A blood clot in an artery obstructs the artery preventing blood from flowing through it.  When the axillary-subclavian artery becomes obstructed, blood cannot get to the arm.  When blood cannot get to the arm, it results in ischemia.  With ischemia, part of the arm can begin to die, and if left untreated, the patient can lose the arm. An aneurysm occurs when part of an artery wall weakens, allowing it to abnormally balloon out or widen which can lead to the formation of a clot.  If an aneurysm grows large enough, it can burst or rupture leading to dangerous bleeding which, in the case of ATOS although exceedingly rare, can be life and/or limb threatening.  Because ATOS involves various stages and forms of arterial obstruction, it can present anywhere from asymptomatic to very severe symptoms.

subclavian artery aneurysm

Subclavian artery aneurysm

Symptom Features:

  • Average age at presentation is 35-40 but can occur at any age

  • Patients are typically young, healthy, and active

  • Usually presents on 1 side of the body at a time

  • Can range from asymptomatic to mild symptoms to severe symptoms

  • Can occur suddenly or gradually over a period of time

  • Can occur either at rest or be activity induced particularly with overhead activities

  • Almost aways associated with a cervical rib or other bony abnormality


  • Asymptomatic especially in the setting of aneurysm or pre-aneurysmal widening of the artery

  • Fatigue, cramping, heaviness, or pain/aching in the arm especially with use or exercise

  • Pain in the arm, hand, or fingers

  • Numbness and/or tingling in the arm, hand or fingers

  • Cold feeling arm, hand, or fingers

  • Pale, bluish or mottled appearance of the arm, hand, or fingers

  • Delayed capillary refill in the fingers

  • Pulse near the elbow and wrist (brachial, radial, or ulnar pulses) may be weak or absent

  • A pulsing, non-tender lump or bulge at the base of the neck in the area above and around the collarbone may represent an aneurysm

  • Raynaud’s syndrome phenomenon in the hand or fingers

  • Blood pressure in the affected arm may be lower than the other arm by approx. 30 mmHg

  • In severe cases of ischemia and where a clot in the subclavian artery has traveled or spread to smaller arteries lower down in the arm, there can be non-healing wounds or ulcers on the fingertips or small spots on the fingers that appear as dark bruising or blood blisters under the skin

  • Very rarely, in the presence of a clot in the artery, a stroke can occur.  This happens when the blood flowing through the axillary-subclavian artery reverses and flows in the opposite direction of normal with blood flowing from it to the vertebral artery which can dislodge the clot and allow it to travel to the vertebral artery which provides blood flow to the brain. Symptoms of this stroke can include arm numbness, weakness, or paralysis, speech dysfunction, facial numbness or paralysis, headache, vomiting, difficulty walking, or dizziness.

  • Occasionally, patients with ATOS will also have NTOS.  Click here to learn more about the symptoms of NTOS.


blue cyanotic hand

Blue cyanotic hand due to lack of blood flow

digital emboli - tiny blood clots in fingers
digital emboli  - tiny blood clots in fingers

Tiny blood clots in fingertips that traveled down from the subclavian artery (digital emboli)

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