 [ Symptoms ] what causes silent migraines [ Disease ] 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 is 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 is thought that the swelling activates pain pathways in the nervous system