For about one in five people with migraines, the experience begins with a distinct and often surreal prelude: the migraine aura.
These auras are most often visual, but they can also manifest as sensory, motor, or even verbal disturbances—a temporary disruption of the senses.
Imagine a slow-moving electrical or chemical wave sweeping across the visual cortex—the part of your brain that processes sight. As this wave propagates, it can create a cascade of vivid, sometimes disorienting, visual hallucinations.
The most classic example is the "fortification spectrum," named for its resemblance to the shimmering, jagged walls of a medieval fortress. It might begin as a small, shimmering spot of light or a cluster of geometric shapes that slowly drift across your field of vision.
This phenomenon can expand into a crescent or C-shape, often with a scintillating, zigzagging edge. As it moves, it seems to grow, sometimes leaving a temporary blind spot (a scotoma) in its wake. While each person's experience is unique—ranging from bright spots to brilliant flashes—these captivating disturbances typically last between 10 and 30 minutes before fading away.