Chronic headache, dizziness, migraine pain, drowsiness, forgetfulness and other illnesses can have a cerebrovascular origin. Brain perfusion is controlled in the understanding of stroke (stroke). This exam requires a very good mastery of the cerebral anatomy and much more of the vascularization circuit at the base of the brain (circulus williti or polygon of willis) and a solid training on the physics of fluids on the one hand and tomography of the fluids on the other hand.