Arterial Thoracic Outlet Syndrome
Arterial thoracic Outlet Syndrome is the least common type of TOS comprising of approximately 1% of all thoracic outlet syndrome cases. It is however the type which has the most serious consequences and the strongest indication for surgical repair.
Almost all cases of aTOS are associated with a bony abnormality, usually an accessory cervical rib. These extra ribs originate one level higher than that usual 1st rib and form a bony fusion with the first rib. The cervical rib often pushes the subclavian artery forward where it is compressed against the scalenus anterior muscle. Over time, this compression may result in a decreased blood supply to the arm, as well as the potential to develop a dilatation or aneurysm of the artery just after where it is compressed. Any dilatation of aneurysm may be a source of clot which may dislodge and travel into the arm, thereby potentially blocking off one of the arteries.
Arterial thoracic outlet syndrome usually happens in young fit patients and most often comes to be diagnosed when the patient presents with either a pulsatile swelling above their collarbone or with evidence of a small clot lodging in one of the arteries in the hand. A simple neck X-ray is all it takes to definitely diagnose the presence of an accessory or cervical rib. A contrast-CT is then usually organised to assess the arterial problem and degree of compression.
Surgery is recommended for all patients who present with signs of an aneurysm or evidence of a small clot lodging in the arm/hand. Similar to other forms of thoracic outlet syndrome, the surgery involves excising the cervical rib, fibrous bands, part of the scalene muscle and usually the first rib as well. Surgery is successful in vast majority of cases with the chance of recurrence being very small.