Signs and Symptoms
Headache pain results from signals interacting between the brain, blood vessels, and surrounding nerves. During a headache, specific nerves of the blood vessels and head muscles are activated and send pain signals to the brain. It's not clear, however, why these signals are activated in the first place.
Headaches that occur suddenly (acute-onset) are usually due to an illness, infection, cold, or fever. Other conditions that can cause an acute headache include sinusitis (inflammation of the sinuses), pharyngitis (inflammation or infection of the throat), or otitis (ear infection or inflammation).