There are two types of migraines, chronic and episodic. Both types are sometimes preceded by a phenomenon known as aura.
The term aura refers to various symptoms that commence approximately 30 minutes or so before the headache begins. These symptoms are thought to be caused by neurotransmitters in the brain.
The symptoms of aura are usually visual and may include such disturbances as seeing flashing lights or wavy lines or losing part or all of your vision for a short period of time. Aura can sometimes include verbal disruptions; sensory disturbances such as mild hallucinations; vertigo; dizziness; or motor problems such as tingling, weakness, or numbness in the extremities.
Migraine with aura is less common than migraine without; it is probably experienced by less than 20 percent of all migraine sufferers. Treatment for migraine with aura is usually the same as treatment for migraine without. It is also possible to experience aura without having a headache or any other symptoms afterward; this situation becomes more common as people get older.