Migraine

Migraine is a primary type of headache, meaning it happens on its own, not because of something like a head injury or tumor. The word “migraine” comes from Greek and means “half of the skull” because the pulsating pain often affects just one side of the head.

Now, let’s take a moment to talk about pain. Imagine you’re trying to hit a nail with a hammer but accidentally smack your thumb instead. Special nerve cells called pain receptors immediately detect the hit and convert it into an electrical signal that travels up your spinal cord to your brain, which interprets the signal as pain. Interestingly, the brain itself doesn’t have pain receptors, so it doesn’t actually feel pain. So, when you have a headache, it’s not the brain that hurts, it’s the structures around it, like the venous sinuses and the meninges, especially the dura mater.

Now, the innervation of these structures comes from the trigeminal ganglion, which sends C fibers and A-delta fibers along the trigeminal nerve, particularly the ophthalmic branch. Together, these fibers form part of the trigeminovascular system, which connects the trigeminal nerve to the blood vessels and meninges.

When this system is activated, the C fibers release calcitonin gene-related peptide, or CGRP, a key chemical involved in pain signaling and inflammation. Interestingly, CGRP receptors are located on A-delta fibers, allowing local cross-talk between these fibers.

When CGRP binds to receptors on nearby A-delta fibers, it makes them more responsive to stimuli, enhancing the transmission of pain signals.

While the exact cause of migraine remains a mystery, we think that the trigeminovascular system and CGRP play a major role. During a migraine episode, C fibers release CGRP, stimulating CGRP receptors on A-delta fibers and vascular smooth muscle cells of the dura mater. Eventually, this leads to vasodilation and promotes neurogenic inflammation, contributing to migraine pain.

Also, migraines tend to run in families, suggesting a genetic predisposition because many individuals with migraines have relatives who also experience the condition. Besides genetics, migraines are about twice as common in biological females than in biological males.

For some individuals, a migraine doesn’t start with pain but with a warning phase called an aura. This happens because of abnormal ion channel activity in cortical neurons, which triggers a process known as cortical spreading depolarization.

During this process, a slow wave of neuronal depolarization moves across the cerebral cortex, followed by a period of hyperpolarization and temporary suppression of neuronal activity.

This wave of electrical changes, also called the spreading depression of Leao, results in temporary sensory disturbances known as aura.

These include visual changes, like flashing lights or blind spots, tingling sensations, and speech difficulties.

Now, several factors are known to trigger migraine episodes.
One major group includes daily habits, such as eating a high-carbohydrate diet, physical inactivity, and stressful life events.

It’s worth mentioning that when psychological stress is involved, migraine attacks often occur after a stressful period, typically at the end of the work week, like on a Friday evening or following a challenging pathology exam.

The second group of triggers covers hormonal changes. For example, estrogen-containing oral contraceptives can worsen migraine symptoms. Additionally, migraines tend to become more frequent during certain phases of the menstrual cycle.

Now, there are several different types of migraines.

First, we have the common migraine, also known as migraine without aura. In this case, migraine usually presents as a one-sided, pulsating headache that gets worse with movement. It can last up to 72 hours and is often accompanied by nausea, vomiting, and sensitivity to light, known as photophobia, as well as sensitivity to sound, known as phonophobia.
Usually, before a migraine episode, patients experience a prodrome of malaise, irritability, or behavioral change that might last for some hours or even days.