Migraine - What makes a migraine

Why Migraines Feel the Way They Do: What's Happening Inside Our Brains?

Migraines are more than just headaches. Migraines are a complex, (typically) temporary neurologic disorder. They are feelings of intense, pounding pain in your head, seeing flashes of light, feeling sick, or being unable to handle bright lights or loud noises. That’s a migraine! But what actually causes these episodes? How do we distinguish that from other types of headache?

The So What

The two most common types of headaches are Tension-type headaches and Migraines. Tension-type headaches are extremely common (80% or more of the population experience them) but they don’t often lead people to see a doctor. Migraines are less common (about 25% of females, 5-10% of males), but if someone is seeing a doctor specifically for a headache, the likelihood of it being a migraine is much higher. The significant distinction between the two is the associated neurologic symptoms, and the neurologic symptoms cause migraines to be much more disabling. Tension-type headaches might involve a minor sensitivity to light or annoyance at loud sounds, and the sensation is that of tightness of the muscles around the head and neck. It generally feels good when massaged and pressure or heat is applied to those muscles.

Migraines are neurovascular phenomena. They have other neurologic symptoms that characterize them, most notably sensitivities of light and sound sensitivity, nausea, brain fog and fatigue, feeling over-heated, and sensitivity to movement. Areas of the scalp and jaw can also become sensitive. It might hurt to brush your hair. Your jaw muscles might feel tight, out of balance, and click (there is a HUGE overlap between migraine and TMJ dysfunction). If you’ve ever felt the overwhelming urge to lie down in a cold, dark room because of a throbbing headache and the instinct that sleep will help your headache—you quite probably had a migraine.

We’ll explore what goes on in the migraine brain.

It’s Not Just About Blood Vessels

A long time ago, we thought migraines happened because blood vessels in the brain would dilate (expand) or constrict (narrow) and that this caused the pain of migraine. Now we know it's more about how nerves in the brain communicate, and how the brain changes its sensitivities to every day sensations. The brain's pain-sensing system goes into overdrive, causing that terrible headache.

The Role of Neurotransmitters and Brain Chemicals

One key player in migraines is a brain chemical called CGRP (Calcitonin Gene-Related Peptide). When too much CGRP is released, it triggers inflammation and makes the nerves in your head sensitive. CGRP is a molecule whose primary action is to dilate (expand) blood vessels when a tissue is not getting enough blood flow. The purpose behind this is to both rescue the target tissue, and it also sensitizes the nerves of the tissue to pain to make us aware of the problem. In migraines, CGRP is released inappropriately. That’s why we thought for a long time that migraines were a vascular process. Now we know it’s a disorder of the nerves and neurotransmitters, and the blood flow changes is an effect (not a cause) of the problem.

The "Warning" Signs: Premonitory Symptoms

Before a migraine even starts, people often get clues that one is coming. These might include yawning a lot, feeling tired, using the bathroom more frequently, craving certain foods, or getting irritable. These signs happen because parts of the brain, like the hypothalamus, are getting activated. Some of the most recent research into migraines highlight the role of the autonomic nervous system including the Hyptothalamic-Pituitary-Adrenal (HPA) axis. That might explain the strong overlaps with dysautonomia, Covid, and other emerging problems.

Cortical Spreading Depression (CSD)

Some migraines come with visual disturbances called an “aura.” This happens because of something called cortical spreading depression (CSD), where a wave of brain activity spreads slowly across the brain’s surface. This causes strange visual effects, like zigzag lines or blind spots. Unlike seizures, which are chaotic and can change consciousness, CSD is a somewhat organized spreading neurologic activity. Auras are a sign of migraine almost by definition. They can even occur without headaches, and we call that “Migraine WITHOUT headache.” Migraines are so much more than only a headache!

The Trigeminovascular System

At the heart of migraine pain is a pathway called the trigeminovascular system. When this pathway gets activated, it sends pain signals to the brain and releases chemicals that cause inflammation. This combination leads to the pounding or pulsing headache of a migraine. The pounding sensation is related to the change in sensitivity of the blood vessels—it’s the feeling of our heartbeat amplified by the sensitivity of the neuroinflammatory process.

Why Do Migraines Cause Light and Sound Sensitivity and Nausea?

Many people with migraines become extremely sensitive to light (called photophobia) and sound (called phonophobia). They also often feel nauseated or may even vomit. But why does this happen?

• Light Sensitivity (Photophobia): During a migraine, the brain's visual processing centers become more sensitive. This makes even normal light seem painfully bright. The brain's pain pathways and visual pathways seem to “cross-talk” during a migraine, which makes the light more unbearable and aggravates the pain.

• Sound Sensitivity (Phonophobia): Similarly, the parts of the brain that handle hearing can become overly active during a migraine. Everyday noises might feel sharp and overwhelming because the brain is in a heightened state of alertness. While the tension causing a Tension-type headache can have light or sound sensitivity, having both makes it much more likely to be a migraine.

• Nausea and Vomiting: The brainstem, which controls basic functions like balance and nausea, is also involved in migraines. When the brainstem is activated during a migraine, the brain can perceive the feeling of nausea. The nerves from the digestive tract send signals to this part of the brain, and when the brainstem is activated, it can produce the same sensations, even if the digestive tract is fine.

These symptoms happen because different areas of the brain are affected during a migraine, not just the parts involved with pain. It's like the brain's whole system is in chaos, which is why migraines feel so overwhelming. It’s also why sleep is one of the most effective treatments for migraine. It is, however, disabling. Sleeping away a migraine can cause significant impairment in work, school, social activities, and missing out on life.

Stick with us as we explore Migraine more over the next several weeks!