As you've learned, headache is caused by a wide variety of environmental and physical factors. And when chronic head pain resembles the vascular, pulsating headache of migraine, it can be difficult for both doctors and patients to distinguish between the two.

Following are some causes of vascular headache that can be mistaken for migraine:

• Viral and bacterial infections. Many infections and illnesses, especially those associated with fever — such as pneumonia, mumps, measles, flu, chicken pox, salmonella, and Lyme disease — have associated headache.

• Caffeine withdrawal. Caffeine is actually used in some migraine treatments to help relieve migraine pain. But if you overdo your caffeine intake, cutting back or going cold turkey can result in a pounding vascular headache.

• Lumbar puncture. This medical procedure, in which a needle is inserted into the spinal canal to remove a small amount of cerebrospinal fluid (CSF), can cause a change in CSF pressure that triggers what is known as a lumbar puncture headache. Like a migraine, the headache is frequently accompanied by nausea and vomiting, but easily distinguishing it from migraine is the sharp worsening upon standing and rapid relief upon lying down.

  A lumbar puncture headache caused by continued leaking of CSF from the puncture site can be easily treated with a blood patch — an injection of the patient's blood into the epidural space to create a blood clot over the puncture hole.

• Nitrates and nitrites. Nitrates are drugs prescribed to patients with angina and congestive heart failure. They dilate, or open, the blood vessels, which can cause vascular headache and facial flushing in some people. A similar compound, sodium nitrite, is used as a preservative in many processed meats, including hot dogs and lunchmeat. Look for sodium nitrite or nitrate on food labels to identify nitrites.

• Temporal arteritis. Also called giant cell arteritis, temporal arteritis is caused by chronic inflammation of the large vessels that supply blood to the face and scalp, branches of the external carotid artery. The condition is most frequently found in adults over age fifty. Because the main symptom is a pulsating headache associated with visual disturbances, it may be misdiagnosed as migraine. This is a potentially serious condition, and prompt treatment with corticosteroids is required to reduce inflammation and prevent vision loss.

Headache can be caused by literally hundreds of medical conditions and environmental factors, from hangover to head injury. Seeing a qualified medical health care professional and keeping a written record of your symptoms is the best way to get an accurate diagnosis of the cause of your head pain.