There are four phases of migraine headaches:
- Prodrome phase
- Aura phase
- Pain (or headache) phase
- Resolution phase
We will review each one in turn.
Phase 1: Prodrome
A prodrome is an indication of an impending migraine attack. Generally, patients will experience a prodrome that they recognize as such.
The prodromal phase usually occurs one to three days before the attack.
Many patients describe a change in mood, while others describe a change in behavior. Many patients describe the feeling that they are going to get a headache. Some describe depression, others, cognitive slowing, and still others, food cravings.
Phase 2: Aura
Some patients will experience a migraine aura. Auras are generally a symptom complex associated with focal neurologic phenomena and may be either positive or negative symptoms. Positive symptoms refer to some added perception; for instance, zigzag lines appearing in the vision or experiencing a sensation of pins and needles. Negative symptoms include loss of some neurologic function; for instance, weakness or vision loss.
Auras generally develop over 5 to 15 minutes, and usually resolve within an hour.
The most typical auras are elementary visual disturbances:
- Scotoma (a localized visual field deficit surrounded by areas of normal vision)
- Seeing clouds
- Seeing spots
- Geometric shapes (e.g., zigzag lines, or fortification spectra)
Visual auras obscure part or all of the visual field, and they may cross the visual field and enlarge.
Alterations of visual perception may also occur:
- Metamorphopsia (a distortion of vision)
- Micropsia (a reduction of the apparent image size)
- Macropsia (an enlargement of the apparent image size)
- Mosaics (a kaleidoscope effect)
More complicated auras include the following:
- Perception difficulties
- Apraxia (the inability to perform a learned task)
- Speech and language dysfunction
- Déjà vu or jamais vu
- Some degree of motor dysfunction (e.g., sensory ataxia)
At the resolution of the aura, the pain or headache phase will begin, generally within an hour.
Phase 3: Pain / headache
A migraine headache is typically unilateral, throbbing in character, and moderate to severe in intensity. The pain is aggravated by physical activity. Sometimes the pain is bilateral, either starting that way and progressing to become unilateral, or vice versa. The pain phase will generally last from a few hours to three days.
Associated symptoms include the following:
- Sensitivity to light and sound
- Smells may be poorly tolerated
The headache phase is generally the result of the activation of meningeal and blood vessel pain receptors by neurotransmitters and peptides released centrally and acting through the trigeminal nerve connections to these pain receptors. Sometimes these centrally acting neurotransmitters and peptides further enhance pain in a process called secondary sensitization. These released chemical mediators ultimately result in inflammation, vasodilation, protein extravasation and platelet activation.
This neurogenic inflammation can then sensitize nerve fibers, a process called peripheral sensitization. These activated fibers will be triggered by normally mild stimuli, such as blood vessel pulsations, creating hyperalgesia, or allodynia. In other words, the process of peripheral sensitization results in pain.
Phase 4: Resolution
During the resolution phase, the pain decreases and gradually resolves.
The patient may feel tired, irritable, and cognitively clouded. There may also be residual scalp allodynia, which can continue even after the headache resolves.
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