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Classical Migraine Attack
Migraine Pathophysiology – Aura – What is Allodynia – Migraine Equivalents
Migraine Under the Hood (Migraine Pathophysiology)
Migraine aura is caused by physiological process called Cortical Spreading Depression. Imagine a brush fire. It starts in some point of the grass field and gradually spreads outwards. The fire (like zigzag lines in visual aura) spreads leaving the burnt area behind.
Some brain nerve cells get agitated spreading the excitation to the neighboring cells like a brush fire. This process leaves burnt and exhausted cells inside the circle. The tired cells go into “sleep mode”. They cannot function normally for some time. The described phenomenon leaves a large area of the brain unable to function properly. A “soup” of chemicals released in the process cause inflammation in the blood vessel walls, which irritates the nerve endings. At this point the migraineur starts feeling the pain. This stage is called peripheral sensitization. The attack can be fully terminated by multiple medications at this moment.
Letting this process to continue activates the next level in the pain processing system. This stage is called central sensitization. It is felt as allodynia, described in “migraine headache”. Pain is much harder to control at this stage and effective medications are limited. This is why it is recommended to treat migraine attack as soon as possible.
Brain has its own “fire department”. Special areas (periaqueductal mid brain is an example) are trying to put down the fire of pain. Ability to do so appears to be limited. It might take from hours to days before the pain attack fire is finally contained.
Now, it will be easier to understand the sequence of events during classical migraine attack. I intentionally use an old-fashioned terminology below since it is easier to digest and you don’t need to pass Neurology Board exams.
Some of the attacks appear to be set off by certain events or conditions. They are called migraine triggers. Common triggers are: skipped meals, insufficient or excessive sleep, stress, noisy environment, and so on.
In about 20 to 30% of migraine sufferers the attacks are triggered by the chain of events described in “Migraine Under the Hood ” section. Corresponding symptoms are called Migraine Aura.
Migraine aura is a transient neurological phenomenon. The most common migraine aura is visual: unformed flashes of light in the visual fields or partial loss of sight. Classical migraine visual aura is an arch of flickering light in the center of the visual field. The arch is gradually expanding and eventually forms a circle with a zigzag border. The zigzag line may be colored or flashing (scintillating scotoma).
A rear type of visual aura (more common in kids) is “Alice in Wonder Land” like phenomenon. Shapes of the surroundings may be distorted: too large, too small, or broken in pieces. A child may tell someone’s head is getting bigger and bigger until it becomes larger than the rest of the body.
Numbness and tingling is the second most common type of aura. A classical sensory presentation is numbness in the hand, which moves up the arm, jumps to the face, lips, and the tongue. Numbness often spreads to the opposite side of the body followed by a classical visual aura. This type of aura is commonly misdiagnosed as an epilepsy or a stroke.
Although rear, migraine aura may present as loss of speech, confusion, personality change, hallucinations or a trance like state.
The next stage is migraine headache. This is a classical textbook version of a migraine attack. Aura is not always followed by a headache. Dizziness might come as a headache substitute in some patients.
Headache may commence at any time but it occurs most frequently upon awakening. Pain intensity ranges from moderate to severe. The intensity of pain builds up and subsides gradually. Sudden explosive headache is not consistent with migraine diagnosis. Untreated migraine headache usually lasts from 4 to 72 hours in adults and from 2 to 48 hours in children.
Excessive sensitivity of the scalp or the upper body can develop during untreated attack of migraine. A simple touch or temperature change may elicit pain. This phenomenon is called allodynia.
Allodynia develops after exposure to an intense pain. Pain processing nerve cells get overexcited and natural pain control systems fail to function properly (central sensitization). Once this type of pain develops, many medications (Sumatripnan for example) do not work. At this stage, it is felt as if even the hair hurt.
Migraineurs may experience brief stabbing pains, lasting for seconds, occurring between more typical migraine attacks. It is often called an “Ice-pick headache”. About 40% report this type of pain.
Migraine Associated Phenomena
Hypersensitivity to light, noise and smells peak at this stage. Most migraineurs are forced to search for dark and quiet place. Mood and mental changes are almost universal.
Most migraine sufferers report inability to perform even simple routine activities during migraine attack. Pain related discomfort is only partially responsible. Brain simply refuses to function normally and ability to concentrate and process any information is poor.
Lightheadedness and vertigo are common. Pale puffy face, stuffed nose and blurred vision are typical as well.
Resolution of the headache phase leaves the person with a poor concentration, sense of being drained and tired for some time. Some people feel unusually refreshed or have elated mood after the attack. Postdrome symptoms may last from hours to days.