An aura is a distinct perception –- either visual, motor, sensory, or psychological –- felt around the time a seizure occurs. Although an aura may signal a seizure because it usually happens a few seconds before a seizure occurs, an aura and a seizure may be separated by as much as an hour. Auras are not experienced with all types of seizures. They are mostly seen in individuals who suffer from complex or generalized seizures. Additionally, auras vary from person to person, and can manifest in a number of ways: 

• Vision – includes distortion of images, seeing bring flashes of light or dark spots, or tunnel vision.
• Smell – certain smells may be experienced during an aura.
• Hearing – certain sounds or voices, or a distortion of sounds that are already present, may occur during an aura.
• Feeling an impending sense of doom, anxiety, or fear.
• Nausea
• Weakness, numbness, or tingling of a limb or limbs.

An aura is usually consistent in the person experiencing it. For instance, if a person is seeing flashes of light before he has a seizure, this aura will be somewhat similar each time before that person has a seizure.

While auras can be helpful in signaling to the individual that he is about to have a seizure and needs to be in a safe place, they can also help healthcare providers pinpoint the area of the brain where the seizure is originating.

http://epilepsy.about.com/od/symptomsandcauses/f/aura.htm

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