Part 6: Where Does Migraine Pain Begin?
Most people assume pain begins in the tissues.
Touch a hot stove, stub your toe, or cut your finger, and it certainly feels that way. But from a neuroscience perspective, that's not actually what happens.
Specialized sensory receptors detect potentially harmful stimuli—such as heat, pressure, or chemical irritation—and send electrical signals toward the brain. This process is called nociception. Pain comes later. Pain is the brain's interpretation of those incoming signals.
That distinction may sound subtle, but it's one of the most important concepts in modern pain neuroscience. It's also one of the keys to understanding migraine.
Nature Gives Us a Clue
One of the easiest ways to understand nociception is to look at the animal kingdom.
Consider a camel walking across the desert. The sand beneath its feet may reach temperatures that would quickly become painful for a human, yet the camel continues walking without injury.
Why?
Because its heat-sensitive nociceptors don't become activated until a much higher temperature than ours. In humans, many heat-sensitive receptors begin responding around 42°C (108°F). Camels tolerate substantially higher temperatures before those same warning systems activate.
The environment hasn't changed.
The nervous system has.
That's an important distinction. Pain isn't determined solely by the stimulus. It also depends on how the nervous system is designed to detect and interpret that stimulus.
Migraine Changes the Threshold
Migraine works much the same way.
The trigeminovascular system is constantly monitoring the tissues of the head and face. Most of the time, this remarkable sensory network quietly sends information to the brain without us ever noticing.
In the migraine brain, however, the threshold changes.
Signals that would normally remain below conscious awareness become amplified. The trigeminovascular system becomes increasingly sensitive, activating inflammatory pathways involving CGRP, substance P, and other neuropeptides.
The result isn't simply "more pain." It's a nervous system that has become easier to activate.
The Overactive Smoke Detector
Imagine a home smoke detector.
A normal detector sounds when smoke fills the room.
A hypersensitive detector goes off every time someone burns toast.
Nothing is wrong with the alarm.
Its threshold has changed.
Migraine behaves much the same way.
The nervous system isn't necessarily damaged.
It's become easier to activate.
Meet the Brain's Sensory Surveillance Network
Every second of every day, your brain receives an enormous amount of sensory information from your face and head.
Is something too hot or too cold? Are your eyes becoming dry? Is there pressure on your teeth? Have you inhaled a noxious chemical? Is there inflammation surrounding the blood vessels covering your brain?
Most of this information never reaches conscious awareness. Instead, it's continuously monitored by an extraordinary sensory network known as the trigeminovascular system.
Although we often refer to the trigeminal nerve as a single cranial nerve, that description doesn't really capture its scale. It is better understood as an extensive communication network. Three major divisions spread across the forehead, eyes, cheeks, jaw, teeth, sinuses, scalp, and meninges before branching into hundreds of smaller sensory fibers. Together, they create one of the most densely innervated regions of the entire body.
Its job isn't to create pain.
Its job is to collect information.
Temperature.
Pressure.
Inflammation.
Chemical irritation.
Mechanical forces.
It doesn't decide whether something hurts. It simply reports what's happening.
The brain determines what those signals mean.
Clinical Pearl: Why the Neck Can Trigger a Migraine
One of the reasons neck pain and migraine are so closely linked is that much of the sensory information from the head doesn't stay separated.
Signals from the trigeminal nerve converge with sensory input from the upper cervical nerves (C1-C3) in an area of the brainstem known as the trigeminocervical complex (TCC).
Think of the TCC as a major communication hub where sensory information from the face, jaw, scalp, meninges, and upper neck all arrives at the same location.
Because these signals converge, the brain doesn't always distinguish where the nociceptive input originated.
An irritated upper cervical joint, tight suboccipital muscles, occipital neuralgia, whiplash injury, or chronic neck dysfunction can all increase nociceptive input into the trigeminocervical complex, potentially lowering the threshold for migraine in susceptible individuals.
This convergence helps explain why so many migraine patients also complain of neck pain—and why treating the cervical spine is often an important part of migraine management.
Continue Rethinking Migraine
This is Part 6 of the Rethinking Migraine series.
Previous Article → Part 5: The Electrical Storm Behind Migraine Aura
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