What is migraine aura?

These are recurrent attacks, lasting minutes, of one-sided fully-reversible visual, sensory, or other central nervous system symptoms that usually develop gradually, and usually followed by headache and associated migraine symptoms.

Visual aura is the most common type of aura and may start as a zigzag figure or geometric pattern in a convex (sickle or C-shape) form that may gradually spread right or left and leave varying degrees of relative scotoma (blind spot) in its wake. 

Sensory aura can be a sensation of pins and needles moving slowing from a point of origin and affecting a greater or smaller part of one side of the body, face and/or tongue. Numbness may follow and could potentially be the only symptom. 

Less frequent aura symptoms are speech disturbances, motor weakness, retinal disturbance, and brainstem symptoms with no motor weakness. 

Two important characteristics of aura is the gradual spread over at least five minutes, and that the symptoms can be positive (for example, flashing lights in the vision, or pins and needle feeling in the hand). This is important to distinguish from transient ischemic attacks (TIA) which can also mimic migraine aura. 

Aura without headache can occur but is less common than migraine with aura.