researchers are now looking at migraine aura and pain as two distinct mechanisms. doing so is leading to a better understanding of silent migraine. in the past experts thought migraines were primarily a problem with blood flow in the brain. that is they thought of them as "vascular" events. they now believe aura is a "neurovascular" event. that means it involves the way nerve cells are firing in the brain and how nerve cell activity relates to the brain's blood flow. aura appears to be a case of overstimulation and then depression of nerve cell activity in the brain. this pattern of reduced brain activity is called "cortical spreading depression. " it literally spreads across the cortex (top layer) of the brain. when it does it often travels from the visual part of the brain (occipital lobe) to the bodily sensation part of the brain (parietal lobe) to the hearing part of the brain (temporal lobe). this pattern mirrors the visual sensation and hearing symptoms common to migraine. the wave of depressed cortical activity has been confirmed by functional mri a high-tech way of mapping how the brain works. migraine pain is thought to be partly caused by blood vessels in the brain dilating. it's thought that the swelling activates pain pathways in the nervous system.
what causes silent migraines?