A headache can sometimes be just a headache. A little rest, a little relaxation, perhaps the taking of an over-the-counter pain medication, and it goes away. But sometimes a headache is a symptom, a complication, or a causal factor in other conditions.
For example, headaches can be a symptom of high blood pressure, or hypertension. Although it is rare that it is actually the cause, headaches can also be indicator of brain disorders such as a brain tumor or brain cancer. Transient ischemic attack, aneurysms, and other blood-flow-related conditions such as blood clots and embolisms, may also show up with headaches as a symptom.
Headaches occur in some inflammatory conditions, including temporal arteritis and temporomandibular joint dysfunction (TMJ).
It is important to remember that most headaches are due to less-serious conditions such as migraine or tension, not tumors or aneurysms.