I started out having constant lightheadedness (a woozy, foggy feeling) and nausea, and when I raised my arms, for example, to wash my hair, I almost passed out; then it progressed to full-on vertigo (the room spinning around me sensation). I have bilateral arterial and venous TOS. I researched it and yes, subclavian steal can be caused by TOS. My thoracic surgeon (who will be performing my rib surgeries) confirmed this. This is what I found:

In subclavian steal syndrome, occlusion or marked stenosis are present, usually due to atherosclerosis, of either the subclavian or innominate artery proximal to the origin of the vertebral artery (VA). The established difference of pressure between the subclavian and basilar artery may lead to a siphoning effect with blood flowing from the opposite VA across the basilar artery and down the VA on the occluded side. This results in a steal blood phenomenon at the expense of the basilar artery, as blood flow is reversed to the ipsilateral occlusion VA, which leads to a hypoperfusion state in the vertebrobasilar arterial (VBA) system and thus vertebrobasilar insufficiency (VBI). in patients suffering from SSS, who developed dizziness, hearing loss or tinnitus, careful neurological examination and follow-up are mandatory in order to prevent other neurological deficits in the VBA territory.