Diagnosis

There is no medical test that can specifically diagnose migraine. A comprehensive question-and-answer session with a patient can often produce a sufficient amount of information for a diagnosis. Patients may be asked: How often do you have headaches? Where is the pain? How severe are the headaches? How long do they last? When did you first develop headaches? Are there any other symptoms that accompany your headaches? They may also be asked about their sleep habits and family and work situations

Most doctors will also obtain a full medical history from the patient, inquiring about past head trauma or surgery, eye strain, sinus problems, dental problems, difficulties with opening and closing of the jaw, and the use of medications. This may be enough to suggest strongly that the patient has migraine. A blood test may be ordered to screen for thyroid disease, anaemia, or infections which might cause a headache. Part of the process of diagnosing migraine headaches requires including other possible causes of headache.

There are a number of factors that possibly indicate a disorder other than migraine:

• headaches are in an accelerating pattern
• they started suddenly or after the age of 50
• a new-onset headache in a patient with cancer or infected with HIV
• headaches are accompanied by fever, stiff neck, or rash
• neurological symptoms other than the typical aura
• optic disk swelling (swelling of the head of the optic nerve, caused by a pressure rise in the brain)

An electroencephalogram (EEG) may be given to measure brain activity. EEG's can indicate a malfunction in the brain, but they cannot usually pinpoint a problem that might be causing a headache. A doctor may suggest that a patient with unusual headaches undergo a computed tomographic (CT) scan and/or magnetic resonance imaging (MRI). The CT scan produces images of the brain that show structures or variations in the density of different types of tissue. The scan enables the physician to distinguish, for example, between a bleeding blood vessel in the brain and a brain tumour, and is an important diagnostic tool in cases of headache associated with brain lesions or other serious disease. MRI uses magnetic fields and radio waves to produce an image that provides information about the structure and biochemistry of the brain.

An eye exam is usually performed to check for weakness in the eye muscle or unequal pupil size. If an aneurysm-an abnormal ballooning of a blood vessel-is suspected, a physician may order a CT scan to examine for blood and then an angiogram. In this test, a special fluid which can be seen on an X-ray is injected into the patient and carried in the bloodstream to the brain to reveal any abnormalities in the blood vessels there.

Thermography, an experimental technique for diagnosing headache, promises to become a useful clinical tool. In thermography, an infrared camera converts skin temperature into a colour picture or thermogram with different degrees of heat appearing as different colours. Skin temperature is affected primarily by blood flow. Research scientists have found that thermograms of headache patients show strikingly different heat patterns from those of people who never or rarely get headaches.

A physician analyses the results of all these diagnostic tests along with a patient's medical history and examination in order to arrive at a diagnosis.