Headaches are extremely common and can take many forms, ranging from mild to debilitating and lasting from minutes to days. When your skull is sore, it’s easy to think that your brain tissue itself must be sore. But that’s not likely.
Ironically, the brain senses pain throughout the body, but doesn’t actually have its own pain receptors. So why do headaches hurt?
Headaches may stem from an underlying medical condition, for example, swollen sinuses, hypoglycemia or a head injury. But generally speaking, most headaches happen because of “referred pain”, which means you feel the pain in a different place than where it actually happens. Dr Charles Clarke (opens in a new tab), neurologist and headache specialist at Vanderbilt Health in Tennessee, told Live Science. It’s similar to how a herniated disc in the back can cause sciatica, pain in the leg. For most headaches, a problem elsewhere in the body — such as the jaw, shoulders and neck — causes pain in the muscles and nerves around the brain, he said.
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Take tension headaches which, according to the World Health Organization (opens in a new tab), are the most common type of recurring headache. Tension headaches often manifest as pain in the muscles at the top of the head or forehead, where a headband or headband would sit, Clarke said. The pain is caused by tight muscles in the face, neck and scalp and may be stress-related, according to the National Institute of Health (opens in a new tab) (NIH). But head pain and tightening of cranial muscles may be secondary to another stress response, such as tight shoulders or a clenched jaw, Clarke said.
According to the NIH, pain-sensing nerves in muscles and blood vessels around the head, neck, and face can be triggered by different processes, such as enlarged blood vessels, stress, or muscle tension. Once activated, these nerves send messages to the brain, but it can feel like the pain is coming from deep within the brain tissue.
Migraines are another type of headache, although technically the headache is just a symptom of the neurological disorder. Migraines can be felt in different ways and in different places: deep pain, superficial pain; the back, left or right of the head; or behind the eyes. What sets migraines apart, Clarke said, is their severity.
Migraine pain is more intense than other headaches and can last longer. The disorder is often genetic and can cause additional symptoms, such as nausea. The underlying causes of migraines are not fully understood, but one theory is that the pain is linked to the trigeminal nerve, the sensory nerve in the head and face; and the dura, the protective layer of the brain where blood vessels expand and contract.
A possible explanation for migraine pain is that an electrical event in the brain stimulates the trigeminal nerve pathways and triggers an inflammatory reaction (opens in a new tab). The inflammation spreads through the dural blood vessels and the trigeminal nerve fibers send signals back to the brainstem (opens in a new tab). The inflammation then spreads to the pain-sensitive meninges – protective tissue around the brain – triggering a headache.
This cascade of inflamed blood vessels and irritated nerves is “a fire that’s spiraling out of control,” Clarke said. It’s like a feedback loop that gets more and more irritated, causing a migraine to develop, he said. This is why many migraine treatments work better if they are deployed earlier.
While the relationships between pain around the body and pain in the head are well established, the mechanisms that cause headaches are still not fully understood, Clarke said. But the good news is that “we’re very good at dealing with them,” he said. For example, lifestyle changes, such as practicing yoga; over-the-counter medications, such as ibuprofen and aspirin; and prescription medications for more severe headaches can go a long way in reducing the severity and frequency of headaches.
“If people need help (with headaches), we can often make them a lot better,” Clarke said.