Migraines are one of four types of primary headaches, and they come in two forms, those with an aura and those without. The other three primary headaches are tension headaches, cluster headaches and, the catch-all type known as, other primary headaches. These include things like exercise induced or cough induced headaches.
No one knows for sure the exact mechanisms that cause migraines, but we do know it's a neurobiological disorder, which I'll get to in a minute..
To begin with, let's look at headaches in general. Headaches come in two forms, primary and secondary. A primary headache is one where the headache is the problem, and as such, is the cause of your symptoms. A secondary headache is one where the headache is the result of something else, like a stroke or a hangover. (See: What Causes Strokes)
Whether a migraine, or a headache caused by binge drinking, it's extremely difficult for medical professionals to differentiate between the different types. This is because they all come with very similar symptoms.
For your doctor to diagnose you with having migraines, and as such be treated with medications for them,your headache must meet the following criteria: you must have at least 5 attacks per year that all have the same presentation; the headache last 4-72 hours; be associated with nausea and/or vomiting; and come with photophobia (intolerance to light) or phonophobia (intolerance to sound). The pain associated with your headache must also meet some criteria: it should only be on one side of your head; have a pulsating quality that is moderate or severe; and is aggravated, or causes the avoidance of, physical activity.
To say your migraine comes with an aura (a specific sensation that precedes the migraine), the aura itself has to meet some benchmarks. Specifically, it has to be fully reversible, and at least one aura symptom gradually spreads over 5 minutes or longer, or you have two or more symptoms that occur in succession. Each aura must last 5-60 minutes and be accompanied by a migraine within an hour (although some studies have suggested this time frame be extended to days). Common aura symptoms include nausea, fatigue, difficulty concentrating, stiff neck, and repetitive yawning. The most common aura is a visual one that can involve sensitivity to light or blurred vision.
Migraines without an aura were once thought to blood-flow related, specifically a decrease in blood flow to the brain. Brain images of people with migraines have shown this to be, most likely, false. The only blood-flow changes to any specific brain area have been to the brain stem. It has been suggested that these changes are more likely the result of pain, and not the cause itself.
While no one has definitively shown the exact origin of migraines, as mentioned, it's now known to be a neurobiological disorder. This basically means, it's an illness of the nervous system that's caused by biological factors like genetics or metabolism. This is known because of several ancillary findings.
Studies have shown the messenger molecules nitric oxide, 5-hydroxytryptamine, and calcitonin gene-related peptide are involved with this type of headache. A class of drugs, known as triptans, has also shown to be extremely effective in treating this type of migraine. This drug class specifically targets the receptor sites for these messenger molecules and either inhibits them, or helps them. Researchers have shown that if you help the messenger molecule for 5-hydroxytryptamine, or inhibit the molecule calcitonin gene-related peptide, headache symptoms can be greatly reduced.
While the migraine itself isn't blood flow related, the aura's associated are. Studies show blood flow to the region of the cortex associated with the headache is decreased before, or happens simultaneously, with the onset of aura symptoms. This decrease tends to start in the back of the affected area and spreads to the front. It can also reach levels that indicate the cells in that area aren't getting enough oxygen and nutrients for normal function.
Due to the fact that no one has nailed down the exact cause of migraines- outside of generic external triggers ranging from things like bright lights to certain foods, to specific smells- the treatment for them revolves around two things: prevention, and pain management during an episode. Prevention can include drugs from many different classes, such as ones that treat high blood pressure, like Beta-blockers, to ones that treat seizures, like Depakote. Prevention can also include identifying and then avoiding triggers for a given individual.
Medications used to manage the symptoms during an attack can include the aforementioned Triptans, like Imitrex. Drugs that affect Seratonin levels can also be prescribed. Anti-nausea drugs like Benadryl, and pain medications, like Codeine, are also extremely common.
In the end, basic neuroscience, as well as clinical research, is rapidly advancing our understanding of migraines and their underlying causes. With any luck, and a lot of continued research, migraines will soon become a thing of the past.
Scott writes for the wildly popular interesting fact website TodayIFoundOut.com. To subscribe to Today I Found Out's "Daily Knowledge" newsletter,click here or like them on Facebook here. You can also check 'em out on YouTube here.