Anatomy of a Headache
Surprisingly enough, the exact mechanism by which headache occurs is not known. There are numerous theories, but no one universally agreed upon cause. What we do know for certain is the basic anatomy of a headache. We know the pain you feel is real and we know the physiology behind the pain.

Headache sufferers may feel as though their brain hurts, but in reality actual brain matter itself is entirely insensitive to pain. Instead, it's the three membranes that cover the brain, called the meninges, that are sensitive to pain.

According to the most widely accepted theory of headache, pain-sensing nerve cells called nociceptors release chemicals called neuropeptides. These neuropeptides cause the vascular smooth muscle surrounding cranial blood vessels to relax, which in turn causes vessel dilation and increased blood flow. Neuropeptides also promote inflammation and tissue swelling. The combination of increased pain sensitivity and tissue and vessel swelling is what causes headache pain. The pain may be confined to one area or it may be generalized and encompass the entire head.

In the final analysis, most headache sufferers don't care about the physiology of pain -- they simply want relief. Diagnosing your headache type and identifying those triggers that affect you personally is the key to alleviating pain.

Headache Classification
In 1988, The International Headache Society (IHS) developed a classification system to assist physicians in the differential diagnosis of headache. This classification system has since become the standard for headache diagnosis and research the world over. The classification criteria, updated in 2004, divide headaches into 14 categories:

1. Migraine
2. Tension-type headache
3. Cluster headaches and other trigeminal autonomic cephalalgias
4. Other primary headaches
5. Headache associated with head trauma
6. Headaches associated with vascular disorders
7. Headaches associated with nonvascular intracranial disorder
8. Headache associated with substances or their withdrawal
9. Headache associated with infection
10. Headache attributed to disorder of homeostasis
11. Headache or facial pain attributed to disorder of cranium, neck,
    eyes, ears, nose, sinuses, teeth, mouth, or other facial or cranial structures
12. Headache attributed to psychiatric disorder
13. Cranial neuralgias and central causes of facial pain
14. Other headaches, cranial neuralgia, central or primary facial pain

So what does all this mean? To your doctor, this classification system means he or she can begin to categorize and treat your headache based on established and proven criteria. To you, the headache sufferer, it means that there are many different types of headaches and diagnosing your particular disorder is the first step to finding relief.