What Causes Migraines
Migraines are one of 4 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. What we do know is, there are anatomical differences between migraines with an aura and those without.
Migraines without an aura were once thought to be caused by a decrease in blood flow to the brain. Current research however, has shown those decreases are likely caused by the pain associated with the migraine and not the migraine itself. Aura symptoms before a migraine, however, do have blood-flow changes associated with their symptoms. To better understand what’s going on with migraines, 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. You may have a headache, but the problem is the bleeding in your brain or the excessive amounts of alcohol you consumed.
Arguably, the organization most responsible for the job of classifying headaches, and making recommendations on treatment, is the International Headache Society (IHS). Since their inception in 1982, they’ve had 3 versions of classification and recommendations for treatment. These versions being re-written when significant changes in the science and understanding of headaches occur.
The IHS recognizes migraines as a significant problem world-wide. In 2010, the Global Burden of Disease Survey was conducted and recognized migraines as the 3rd most prevalent disorder. It was also the seventh-highest cause of disability.
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. The difference being the exact mechanisms causing those symptoms. Often times, the only thing to separate one cause from the other, is what you tell the doctor.
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 a year that all have the same presentation. The headache lasts 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. 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 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, it’s now known to be a neurobiological disorder. Basically meaning, 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 no one has nailed down the exact cause of migraines, the treatment for them revolves around two things. Prevention, and pain management during an episode.
Prevention can include drugs from many different classes. Ones that treat high blood pressure, like Beta-blockers, to ones that treat seizures, like Depakote.
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 advancing our understanding of migraines and their causes. With any luck, and a lot of continued research, migraines will become a thing of the past.