When you have a headache, you may wonder what is going on inside your brain. Brain tissue itself cannot feel pain. Instead, your brain processes pain sensations that it receives from the rest of the body. Depending on the type of headache you have, pain signals may come from nerves, blood vessels or membranes that surround the brain, or from muscles of the head and neck. Some headaches are also associated with electrical changes in brain activity.
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Tension-type headaches are the most common variety. Dull, pressurelike pain on both sides of the head is typical, sometimes extending to the back of the head. Muscles of the head and neck might be tender. The cause of tension-type headache is not known, though some suggest that the pain originates from excess muscle tension. Pain-sensitive nerves within tense muscles carry these signals to the spinal cord and then to higher brain areas involved in touch, emotions and movement.
Migraines cause throbbing pain on one side of the head, typically with other symptoms such as light and sound sensitivity, nausea and vomiting. Some people experience an aura before the headache, with symptoms like seeing flashing lights. A wave of electrical activity spreads across the brain during the aura. Migraine pain primarily involves the trigeminal and cervical nerves, which carry pain signals from the face, head and neck, and from the blood vessels and membranes around the brain. Pain signals from these nerves are amplified as they enter the brainstem, making them hypersensitive. This sets up a vicious cycle of worsening pain.
Headaches may result from increased pressure inside the head. This can happen when a tumor or bleeding blocks the flow of cerebrospinal fluid, which surrounds and cushions the brain. Increased pressure can also be caused by brain swelling due to head trauma, stroke or infection. In all of these cases, pain results from stretching of blood vessels inside the head and is sensed by the trigeminal and cervical nerves. Headaches from increased intracranial pressure may be worse in the morning and associated with vomiting and blurry or double vision.
When to Seek Medical Attention
Seek emergency medical attention if you have a headache that is sudden or severe, if you have a stiff neck or changes in your vision. See your doctor if you have a headache with nausea or vomiting, trouble with speech or swallowing, changes in sensation or problems walking.