In ancient Greece, headaches were considered powerful afflictions. Victims prayed for relief from Asclepius, the god of medicine. And if pain continued, a medical practitioner would perform the best-known remedy— drilling a small hole in the skull to drain supposedly infected blood. This dire technique, called trepanation, often replaced the headache with a more permanent condition.
Fortunately, doctors today don’t resort to power tools to
cure headaches. But we still have a lot to learn about this ancient ailment.
Today, we’ve classified headaches into two camps— primary
headaches and secondary headaches. The former are not symptomatic of an
underlying disease, injury, or condition; they are the condition. Primary
headaches account for 50% of reported cases, we actually know much more about
secondary headaches.
Secondary headaches are caused by other health problems,
with triggers ranging from dehydration and caffeine withdrawal to head and neck
injury, and heart disease. Doctors have classified over 150 diagnosable types,
all with different potential causes, symptoms, and treatments. But we’ll take
just one common case —a sinus infection—as an example.
The sinuses are a system of cavities that spread behind our
foreheads, noses, and upper cheeks. When our sinuses are infected, our immune
response heats up the area, roasting the bacteria and inflaming the cavities
well past their usual size. The engorged sinuses put pressure on the cranial
arteries and veins, as well as muscles in the neck and head. Their pain
receptors, called nociceptors, trigger in response, cueing the brain to release
a flood of neuropeptides that inflame the cranial blood vessels, swelling and
heating up the head.
This discomfort, paired with hyper-sensitive head muscles,
creates the sore, throbbing pain of a headache. Not all headache pain comes
from swelling. Tense muscles and inflamed, sensitive nerves cause varying
degrees of discomfort in each headache. But all cases are reactions to some
cranial irritant.
While the cause is clear in secondary headaches, the origins
of primary headaches remain unknown. Scientists are still investigating
potential triggers for the three types of primary headaches: recurring,
long-lasting migraines; intensely painful, rapid-fire cluster headaches; and,
most common of all, the tension headache.
As the name suggests, tension headaches are known for
creating the sensation of a tight band squeezed around the head. These
headaches increase the tenderness of the pericranial muscles, which then
painfully pulse with blood and oxygen. Patients report stress, dehydration, and
hormone changes as triggers, but these don’t fit the symptoms quite right. For
example, in dehydration headaches, the frontal lobe actually shrinks away from
the skull, creating forehead swelling that doesn’t match the location of the
pain in tension headaches.
Scientists have theories for what the actual cause is,
ranging from spasming blood vessels to overly sensitive nociceptors, but no one
knows for sure. Meanwhile, most headache research is focused on more severe
primary headaches.
Migraines are recurring headaches, which create a vise-like
sensation on the skull that can last from four hours to three days. In 20% of
cases, these attacks are intense enough to overload the brain with electrical
energy, which hyper-excites sensory nerve endings. This produces hallucinations
called auras, which can include seeing flashing lights and geometric patterns
and experiencing tingling sensations.
Cluster headaches, another primary headache type, cause
burning, stabbing bursts of pain behind one eye, leading to a red eye,
constricted pupil, and drooping eyelid.
What can be done about these conditions, which dramatically
affect many people’s quality of life? Tension headaches and most secondary
cases can be treated with over-the-counter pain medications, such as
anti-inflammatory drugs that reduce cranial swelling. And many secondary
headache triggers, like dehydration, eye strain, and stress, can be proactively
avoided.
Migraines and cluster headaches are more complicated, and we
haven’t yet discovered reliable treatments that work for everyone. But
thankfully, pharmacologists and neurologists are hard at work cracking these
pressing mysteries that weigh so heavily on our minds.
References: All data is provided by TED-Ed
