Migraine Headache

What Differentiates Migraine Aura from Headache?

Migraine Aura is a visual (related to vision) symptom of migraine that occurs due to an alteration in the brain of a migraine sufferer. It serves as a warning sign about the onset of headache. A patient suffering from it sees shining zigzag lines or blot-out vision. The patient may experience other symptoms related to brain like weakness, unsteadiness, altered consciousness or numbness of hands and face.

Migraine aura is a disorder which recurs over the time. Auras are usually related to sight but can also be motor, verbal or sensory disturbances. A visual aura resembles a chemical or electrical wave that moves across the brain's visual cortex. Visual cortex is that part of the brain that processes visual signals. As this wave spreads, the patient tends to experience visual hallucinations.

It develops gradually over 5-20 minutes and lasts for less than 60 minutes. This is followed by headache with migraine symptoms. Sometimes headache lacks the features of migraine or is completely absent, though it is not common. This condition is known as migraine aura without headache.

The aura occurs because of the changes that take place in the outer layer of the brain, that is, the cortex. The decline in the activity of the nerve cell is responsible for the typical pattern of development of the aura. Migraines may progress through four stages:
  • Predrome
  • Aura
  • Attach
  • Post-drome

It is not necessary that everyone has to undergo all the four stages. About 60% of the patients go through the stage of predrome. About 20 percent of the people experience a distinct warning sign in the second phase called the migraine aura.

The decline in nerve cell activity is responsible for the pattern of the particular aura. In migraine aura, symptoms emerge in one region of the body and gradually move to the visual regions. For example, the patients first see a black spot surrounded by bright zigzag line or flashing lights in their field of vision. The size of this black spot increases over a period of few minutes, engulfing the entire region of sight. Another typical feature of migraine aura is the blacking out of vision because of depressed nerve activity.

Auras can vary from person to person. People may experience bright spots or flashes. A sensory aura also occurs in some cases. Sensory aura starts as numbness or a tingling effect in one limb for over 10-20 minutes. This sensation sometimes spread to one side of the face and the tongue.

These internal and external events stimulate the various nerves of the brain. This stimulus is then relayed to one of the brain's nerve centers. From there, another set of nerve impulses are sent to the cortex which results in the aura. The biochemical phenomenon that leads to headache also begins in these brain centers.