What causes aura?
Migraine FAQs: What causes aura?
When migraine sufferers undergo MRI (magnetic resonance imaging) during aura, in certain patients, the changes in the brain (officially called a cortical spreading depression) can be seen slowly moving across part of the brain.
It is thought that auras are caused by a wave of nerve signals or impulses that move across the brain, causing a disruption in normal activity in those parts of the brain.
These changes are thought to cause the changes in vision or feelings of numbness.