Thank you, Donna--I looked up the definition..."reduction in blood flow through the vertebrobasilar arterial system, which supplies the brain stem, cerebellum, occiptial lobe, medial temporal lobe, and thalamus. Symptoms include syncope, lightheadedness, visual disturbances,vertigo and Brain stem/brain infarctions". My gut instinct directed me to the cerebrovascular disease section and I scanned each code for a clue. Due to one of my specialties, I work with SDH, infarctions, etc...daily. I really, really like tough questions. I'm begging to sit in on a brain surgery. (Fingers crossed)