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
C.N.S
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
Occlusion of the subclan aery proximal to origin of veebral aery