A headache describes any acute or throbbing pain felt throughout the skull. It is caused by any one of a number of conditions that cause inflammation of the nerve endings in the scalp and face. The brain itself does not have any nerve endings, so a headache in and of itself does not always indicate that anything is wrong with the brain. Most headaches are caused by stress and lack of sleep, which tighten the muscles in the head.
Severe headaches such as migranes and cluster headaches can be dehabilitating even though they are not symptomatic of any serious underlying condition. However, a severe persistent headache in a patient without a medical history of such headaches can be an indication of a serious condition.
Most headaches can be treated with mild painkillers, rest and fluids. However, a persistent headache usually indicates a condition that requires immediate medical attention. In addition, a very severe headache is also an indication that a person is suffering from a serious medical condition and requires immediate hospitalization.