The "subclan steal syndrome" occurs due to
*Subclan steal:when the arm is used,blood is stolen from the brain the veebral aery .this lead to veebro-basilar ischemia ,which is characterised by dizziness ,coical blindness and/or collapse. Ref Harrison20th edition pg 2456
Occlusion /stenosis of the veebral aery
Occlusion/stenosis of the carotid aery
Occlusion of the subclan aery proximal to origin of veebral aery
Occlusion of the subclan aery distal to origin of veebral aery
C.N.S