Because the brain lacks its own pain receptors, headaches are excruciating.
Headaches are extremely common, and they can range from mild to debilitating, lasting minutes to days. When your cranium is in pain, it’s natural to believe that your brain tissue is as well. But that is unlikely.
Ironically, the brain detects pain throughout the body but lacks its own pain receptors. So, why do headaches hurt?
Headaches can be caused by an underlying medical condition, such as swollen sinuses, low blood sugar, or a head injury. However, most headaches are caused by “referred pain,” which means you feel the pain in a different location than where it is actually occurring, according to Dr. Charles Clarke(opens in new tab), a neurologist and headache specialist at Vanderbilt Health in Tennessee. It’s similar to how a herniated disc in your back can cause sciatica (leg pain). According to him, most headaches are caused by an issue elsewhere in the body, such as the jaw, shoulders, or neck, which causes pain in the muscles and nerves surrounding the brain.
Take, for example, tension headaches, which are the most common type of recurring headaches, according to the World Health Organization(opens in new tab). Clarke describes tension headaches as pain in the muscles across the top of your head or forehead, where a sweatband or a headband would sit. According to the National Institute of Health(opens in new tab), the pain is caused by tightened muscles in the face, neck, and scalp and can be stress-related (NIH). However, head pain and cranial muscle tightening can be secondary to another stress response, such as tight shoulders or a clenched jaw, according to Clarke.
According to the National Institutes of Health, pain-sensing nerves in the muscles and blood vessels surrounding the head, neck, and face can be triggered by a variety of factors such as enlarged blood vessels, stress, or muscle tension. When these nerves are activated, they send messages to the brain, but the pain may feel as if it is coming from deep within the brain tissue.
Migraines are another type of headache, though they are technically only one symptom of a neurological disorder. Migraine headaches can be felt in a variety of ways and locations, including deep pain, surface pain, the back, left, or right side of the head, and behind the eyes. The severity of migraines, according to Clarke, distinguishes them.
Migraine pain is more intense than other types of headaches and can last longer. The disorder is frequently inherited and can result in additional symptoms such as nausea. The causes of migraines are unknown, but one theory is that the pain is caused by the trigeminal nerve, the sensory nerve for the head and face, and the dura, the brain’s protective layer where blood vessels expand and contract.
One theory for migraine pain is that an electrical event in the brain stimulates the trigeminal nerve pathways, causing an inflammatory response (opens in new tab). The inflammation spreads through the dural blood vessels, and the trigeminal nerve fibres transmit signals to the brain stem (opens in new tab). The inflammation then spreads to the pain-sensitive meninges, which are protective tissue surrounding the brain, causing a headache.
This cascade of inflamed blood vessels and irritated nerves is “a fire that is burning out of control,” according to Clarke. He described it as “a feedback loop that becomes more and more irritated, causing the experience of a migraine to build.” As a result, many migraine treatments work better if used sooner.
While the links between pain in the body and headaches are well established, the mechanisms that cause headaches remain unknown, according to Clarke. The good news, however, is that “we are very good at treating these,” he said. For example, lifestyle changes like yoga, over-the-counter medications like ibuprofen and aspirin, and prescription medication for more severe headache disorders can all help reduce headache severity and frequency.
“If people need help [with headaches], we can frequently make them much better,” Clarke said.
Erin Balsa is a highly skilled and knowledgeable health journalist with a passion for educating the public on important health and wellness topics. With extensive experience in both traditional and digital media, Erin has established herself as a trusted voice in the field.