What causes headaches?

In ancient Greece, headaches were considered powerful afflictions. Sufferers prayed for relief from Asclepius, the god of medicine. And if the pain persisted, a medical practitioner would resort to the best-known remedy of that era: trepanation, which involved drilling a small hole in the skull to drain supposedly infected blood. Unfortunately, this drastic technique often replaced the headache with more permanent conditions. Luckily, in modern times, we don't employ such extreme measures to alleviate headaches. However, we continue to explore and research this ancient ailment, striving to better understand its complexities.

Today, we classify headaches into two primary categories: primary headaches and secondary headaches. The former are not symptomatic of any underlying disease, injury, or condition; instead, they are the condition itself. Primary headaches, including migraines, cluster headaches, and tension headaches, account for about 50% of reported cases. Despite their prevalence, much remains to be uncovered about their origins and treatment.

Secondary headaches, on the other hand, are caused by various underlying health problems. Triggers can range from something as common as dehydration or caffeine withdrawal to more serious issues like head and neck injuries or heart disease. In fact, doctors have identified over 150 diagnosable types of secondary headaches, each with distinct potential causes, symptoms, and treatments.

To illustrate, let's consider a common example: a sinus infection. The sinuses, a system of cavities located behind our foreheads, noses, and upper cheeks, become inflamed when infected. This inflammation increases the size of the cavities, leading to pressure on cranial arteries and veins, as well as head and neck muscles. Nociceptors, pain receptors in the area, signal the brain to release neuropeptides, inflaming cranial blood vessels and causing head swelling. This, coupled with sensitive head muscles, results in the characteristic throbbing pain associated with headaches.

It's essential to note that not all headache pain stems from swelling. Tense muscles and sensitive nerves can cause varying degrees of discomfort in each headache, but all cases are reactions to some cranial irritant. While secondary headaches have clear causes, the origins of primary headaches remain elusive. Researchers are actively investigating potential triggers for three common types of primary headaches: migraines, cluster headaches, and tension headaches.

Tension headaches, the most prevalent among primary headaches, often create a sensation of a tight band squeezing the head. These headaches exacerbate the tenderness of pericranial muscles, causing them to pulse painfully with blood and oxygen. Although stress, dehydration, and hormone changes have been suggested as triggers, they don't entirely align with the symptoms. For instance, dehydration headaches involve frontal lobe shrinkage, leading to forehead swelling, a feature not found in tension headaches. The actual causes of tension headaches remain a subject of scientific debate, ranging from spasming blood vessels to overly sensitive nociceptors.

While the mystery of primary headaches continues, most headache research is directed toward more severe primary headaches. Migraines, which are recurring headaches lasting from four hours to three days, produce a vise-like sensation on the skull. In approximately 20% of cases, these attacks are intense enough to overload the brain with electrical energy, resulting in hallucinations known as auras. These can encompass seeing flashing lights, geometric patterns, and experiencing tingling sensations. Cluster headaches, another primary type, provoke burning, stabbing bursts of pain behind one eye, leading to a red eye, constricted pupil, and drooping eyelid.

Managing these conditions is challenging and often dramatically impacts people's quality of life. While tension headaches and most secondary cases can be treated with over-the-counter pain medications like anti-inflammatory drugs to reduce cranial swelling, migraines and cluster headaches are more complex. Currently, there are no universally effective treatments for these conditions. However, researchers in pharmacology and neurology are tirelessly working to unlock the mysteries of these debilitating ailments that weigh so heavily on the minds of those affected.