What causes haedaches?

In ancient Greece, headaches were considered powerful afflictions. Sufferers prayed for relief from Asclepius, the god of medicine. If the pain persisted, a medical practitioner might resort to trepanation—a procedure involving drilling a small hole in the skull to drain supposedly infected blood. This dire technique often replaced the headache with a more permanent condition.

Fortunately, modern doctors no longer use such extreme measures to treat headaches. However, headaches remain a complex ailment. Today, we classify them into two categories: primary headaches and secondary headaches. Primary headaches are not symptomatic of an underlying disease or condition; they are the condition itself. While primary headaches account for 50% of reported cases, we understand secondary headaches much better. These headaches are caused by other health problems, with triggers ranging from dehydration and caffeine withdrawal to head and neck injuries and heart disease. Over 150 types of secondary headaches have been classified, each with different potential causes, symptoms, and treatments.

One common example of a secondary headache is a sinus infection. The sinuses are cavities located behind our foreheads, noses, and upper cheeks. When infected, the immune response heats up the area, inflaming the cavities beyond their usual size. The engorged sinuses put pressure on the cranial arteries, veins, and neck and head muscles. Pain receptors, called nociceptors, trigger the brain to release neuropeptides, inflaming cranial blood vessels and causing the head to swell and heat up. This discomfort, paired with hypersensitive head muscles, creates the throbbing pain of a headache.

Not all headache pain results from swelling. Tense muscles and inflamed, sensitive nerves cause varying degrees of discomfort. However, all headaches are reactions to some cranial irritant. While the cause of secondary headaches is clear, the origins of primary headaches remain unknown. Scientists are investigating potential triggers for the three types of primary headaches: recurring, long-lasting migraines; intensely painful, rapid-fire cluster headaches; and the most common, tension headaches.

Tension headaches create the sensation of a tight band around the head, increasing the tenderness of the pericranial muscles, which pulse painfully with blood and oxygen. Patients report stress, dehydration, and hormone changes as triggers, but these don't fully explain the symptoms. For instance, dehydration headaches cause the frontal lobe to shrink away from the skull, creating forehead swelling that doesn't match the pain's location in tension headaches. Theories about the cause range from spasming blood vessels to overly sensitive nociceptors, but the exact cause remains unknown. Most headache research focuses on more severe primary headaches.

Migraines are recurring headaches that create a vise-like sensation on the skull, lasting from four hours to three days. In 20% of cases, these attacks hyper-excite sensory nerve endings, producing hallucinations called auras, which include flashing lights, geometric patterns, and tingling sensations. Cluster headaches, another primary type, cause burning, stabbing pain behind one eye, leading to a red eye, constricted pupil, and drooping eyelid.

What can be done about these conditions that significantly affect quality of life? Tension headaches and most secondary headaches can be treated with over-the-counter pain medications, such as anti-inflammatory drugs that reduce cranial swelling. Many secondary headache triggers, like dehydration, eye strain, and stress, can be proactively avoided. Migraines and cluster headaches are more complicated, and reliable treatments that work for everyone have not yet been discovered. Thankfully, pharmacologists and neurologists are diligently working to solve these pressing mysteries that weigh heavily on our minds.