subclavian steal syndrome

Subclavian steal syndrome is usually due to atherosclerotic narrowing of the proximal subclavian artery, which results in flow reversal in the ipsilateral vertebral artery.  This occurs most often on the left side, and many patients are asymptomatic.  A significant percentage has symptoms of arterial insufficiency in the affected upper extremity (eg, exercise-induced fatigue, pain, numbness, coolness, fatigue).  Some patients have symptoms relative to vertebral-basilar artery insufficiency (eg, dizziness, vertigo, disequilibrium, drop attacks).