Bilateral subclavian steal: a review of an unusual twist in a common disorder.

The authors present two cases of bilateral subclavian steal syndrome, a rare condition that does not commonly cause neurovascular symptoms. Lateralizing hemispheric events occur usually with carotid lesions. Vertebral-basilar insufficiency is three times more common in bilateral than in unilateral subclavian steal syndrome. Arm-exercise-induced brain-stem dysfunction is rare, and is seen only in bilateral subclavian steal syndrome.