The Migraine Brain: A Sensitive System
Think of a migraine-sufferer’s brain as being extra-sensitive or “hyperexcitable.” Basically, it is like a finely tuned instrument that is easily set off by certain internal or external changes known as triggers.
The current understanding is that a migraine attack starts deep inside the brain, not just in the blood vessels or muscles.
Change like stress, lack of sleep, or hormonal changes (especially in women) can set off a migraine attack.
In about one-third of people, a slow-moving wave of electrical activity sweeps across the brain’s surface. This is called Cortical Spreading Depression (CSD). It is thought to be the cause of the migraine aura. The aura phenomenon can be a temporary visual changes (like flashing lights or zigzag lines) or sensory changes (like tingling). Interestingly, migraine aura can happen before or during the headache.
As the brain activity changes, nerve cells in the brain release various chemicals, most famously Calcitonin Gene-Related Peptide (CGRP) and serotonin.
These chemicals interact with the trigeminal nerve (the main nerve that sends feeling from the face and head to the brain). The chemicals cause irritation and inflammation around the blood vessels that surround the brain.
The irritation of the trigeminal nerve and the surrounding inflammation send strong, pulsating pain signals to the brain. This is what you experience as the characteristic throbbing migraine headache.
It Runs in the Family
A very strong piece of evidence is that migraine is largely a genetic disorder. Hence, ff your parents have migraines, you are much more likely to have them too. This suggests a built-in sensitivity in the brain’s wiring.
A Migraine episode has different stages, and it starts way before the onset of headache. In fact, the headache is only the tip of the Iceberg.
The symptoms at this phase seem closely tied to things that hypothalamus in your brain does automatically in order to keep your body running smoothly, such as controlling how alert you are, when you sleep, and when you eat.
The activities in Hypothallus may start 48hrs before the headache phase which leads to a series of symptoms such as craving, yawning, fluid retention and mood swings.
Think of your aura as a brief short-circuit in one area of your brain.
The dominant theory is that the aura is caused by something called 'cortical spreading depression.'
This is like a slow-moving, domino effect of electrical disruption:
01: A group of brain cells suddenly fires too much (the hyperactivity).
02: Right after, they get completely worn out and shut down (the inhibition).
in summary, this wave of 'fire-then-silence' spreads across the sensory part of the brain, causing the temporary, reversible symptoms (like vision changes or tingling) that make up the aura.
However, not every Migraineurs experience aura. Hence, International Classification of Headache Disorders (ICHD-3, 2013), has divided migraine into 2 major types:
Migraine without aura
Migraine with aura
That means you get a brief, odd sensation—such as visual changes or tingling—right before or during the bad headaches. You may also experience the aura without any headaches
Even though you feel the headache pain deep inside your head—like it's coming from the brain's coverings (dura matter) or blood vessels—the pain signal actually starts with one of your brain’s nerves - the trigeminal nerve.
Think of the trigeminal nerve as the main wire for pain in your face and head. When the headache phase begins, this nerve gets activated, and it sends the pain message up a specific "highway" in the brain (the trigeminothalamic pathway) to reach the processing centres where you finally register the feeling of a headache.
So, the pain isn't just felt locally inside; it's an electrical signal travelling up a specific nerve route from the beginning.
Typically, around 80% of people with migraines (called migraineurs) report at least one symptom that isn't a headache but still causes major problems and makes it hard to function normally. Unfortunately, these non-headache issues such as nausea, vomiting, light, sound, smell sensitivity are often what makes the overall migraine experience so disabling.
This final stage of the migraine is the biggest mystery to doctors and researchers.
What the Brain Does
While the headache is fading, brain imaging often shows a widespread drop in blood flow throughout the brain. This suggests the brain is still recovering and generally slowing down.
A Confusing Exception
Oddly, a few studies suggest that one part of the brain—the occipital cortex (which handles vision)—might still have increased blood flow even after the pain is gone, which adds to the mystery of what's happening during this recovery phase.
Basically, the diagnose of Migraine is based on a comprehensive consultation. Therefore, your clinicians only considers a brain scan when there is a cause of concern for your headaches.
At Belfast Migraine Clinic, Maryam Shafiei, our experienced Advanced Practitioner in headache disorders carries out a thorough consultation and neurological examination. She will write a clinic letter to your GP and advise accordingly should there be a need for further neurological investigation by A & E or your GP.
Comprehensive review of your symptoms and patterns.
Physical assessment of your nervous system function.
Advanced scans to rule out other underlying concerns in case of red flags .