H

headache PAIN perceived as coming from the
face and head. Headache is a common experience,
with about 45 million adults in the United States
having frequent headaches. There are numerous
types of headache resulting from various causes.
Among them are tension headache, migraine
headache, cluster headaches, sinus headache, and
rebound headache. Headache may also indicate
HYPERTENSION (high BLOOD PRESSURE), TRANSIENT
ISCHEMIC ATTACK(TIA), or STROKE. Headache also is
common with COLDS, flu, and FEVER. Very rarely
headache may signal an INFECTIONsuch as MENINGI-
TISor an ANEURYSMor a tumor in the BRAIN.
The nerves in the soft tissue of the head, neck,
and face transmit the pain signals familiar as
headache. There are no sensory nerves in the
brain or bones of the skull, even though headache
pain often feels as though it comes from deep
within the head. Pain associated with events
within the brain, such as tumor or stroke, arises
from the increase in pressure within the cranium
(enclosure of the skull) these conditions cause.
The pressure stimulates the network of nerves
that interlace with BLOODvessels at the base of the
brain. This NERVE and blood vessel network
extends into the soft tissue surrounding the skull,
magnifying the perception of pain.

Sudden, severe headache or headache

with stiff neck, high or prolonged FEVER,

or blow to the head may signal a med-

ical emergency that requires urgent

evaluation from a doctor.

Tension Headache
Tension headaches are the most common type of
headache, resulting from MUSCLEtenseness in the
shoulders, neck, and head. Stress, which often

causes people to unknowingly tense their muscles,

is a key factor. The stress may be emotional, related

to job or family issues, or the stress may be physical,

arising from lack of sleep, sitting too long in one

position, going without eating, or loud noise. The

tightened muscles aggravate nociceptors, the sen-

sory molecules that respond to intense stimuli,

which generate nerve signals of pain. The irritated

muscles may also develop some INFLAMMATION, fur-

ther stimulating nociceptors. Researchers believe

biochemical factors, such as altered neurotransmit-

ter balances (which affect the function of neurons)

and increased production of PROSTAGLANDINS(which

influence inflammation and changes in the walls of

blood vessels), may also contribute to tension

headaches by affecting the sensitivity of nocicep-

tors. Tension headaches range in severity from mild

discomfort to pain severe enough to cause NAUSEA,

VOMITING, and disturbances of vision. Many tension

headaches go away when the stressful situation

ends. Others may last for several days or become

chronic (recurring).

Migraine Headache

Migraine is the most common type of vascular

headache. About 28 million Americans experience

chronic migraine headaches. For many people the

pain of migraine is debilitating. The conventional

understanding of migraine is that the pain is a

reaction to extreme changes (constriction and

dilation) in the blood vessels that serve the head,

likely as a consequence of rapid fluctuations in

neurotransmitters, prostaglandins, and other sub-

stances that affect circulation. Recent research

suggests there are genetic components to the

mechanisms that regulate blood vessel constriction

and dilation in the head, postulating that defects

in genetic encoding (the protein messengers genes

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