02 December 2008

What causes headaches?

We look at primary and secondary headaches and its triggers.

Headaches are broadly divided into two groups, primary and secondary.

Primary headaches

  • The most common type of primary headache is scalp and neck "muscle contraction" or tension headache. This affects 20% of the population. Tension headaches are primarily caused by abnormal tension in the muscles of the head and neck, which is often exacerbated by stress or anxiety.
  • Migraine, which has an important vascular component, makes up the other large group of primary headaches – affecting 5 to 10% of the population.
  • Cluster headaches are primary headaches that affect only about one percent of headache sufferers. They are important, though, because they are so severe – so severe in fact that they are often referred to as “suicide headaches”.
  • Tension headaches and vascular headaches such as migraine can occur in an individual at the same time. In fact, in practice, the distinction between these two entities is seldom clear-cut, and muscle tension and vascular pain almost always occur simultaneously to varying degrees.

Secondary headaches

Secondary headaches are those headaches caused by some other identifiable condition. With secondary headache, once the underlying medical condition has been identified and treated, the headache subsides. Examples of secondary headache are:

  • Headaches due to infection of surrounding structures: sinus infection, tonsillitis, toothache, meningitis.
  • Headache due to inflammation of surrounding tissues: cervical spine arthritis, constant coughing, straining of the eyes, acute glaucoma, trigeminal neuralgia (a neural disorder) and temporal arteritis (a disorder of the arteries).
  • Certain conditions will cause a stretching or pulling of pain-sensitive parts and inner structures of the head. These include concussion and other head trauma, strokes, brain tumours and spinal taps (lumbar puncture).

If a headache is caused by a serious illness, other symptoms are often present, such as vomiting, dizziness or changes in vision.

Danger signs to be aware of may be:

  • A “first time” headache, or a headache that has changed in nature
  • Headache brought on by exertion
  • Headache accompanied by fever
  • Headache accompanied by drowsiness or confusion
  • Headache with stiff neck (especially if fever and nausea are also present)
  • Headache accompanied by physical abnormalities, such as muscular weakness, sensory loss, tremor and gait disturbances.
  • Headache in a patient who simply “looks ill”

Although the above can be signs of a serious or life threatening problem, this is not always the case.

Headache triggers

One of the main reasons why headaches are difficult to treat is that there is a bewildering array of triggers that can set off a headache. As a result, these triggers are often blamed for the headache, whereas in reality, the patient’s body is reacting abnormally to the trigger. In other words, there is an underlying abnormal condition that makes the body react to the trigger. If the underlying abnormality is identified and treated, then very often the trigger no longer has the same effect.

Of course, if a trigger is identified, and can be easily avoided, then one should do so. This is particularly true of dietary triggers, over which the patient has the ultimate control. The problem comes in with triggers such as stress, which is a normal phenomenon that everyone has to some extent. It is in most cases impossible to avoid stress – most people can’t change their lifestyle, job, relationships, etc. The same is true for hormonal triggers – most women with hormone-related migraines have normal hormone levels. However, their bodies are reacting abnormally to the normal cyclical changes in hormone levels.

Identifying triggers is further complicated by the fact that in most people, migraine attacks are not triggered by just one thing. They often have several migraine triggers. When these triggers occur on their own, they may not bring on an attack, but when they occur together, they result in a migraine.

Dietary triggers are numerous and varied, but the most common are (remember that often what affects one person is fine for another):

  • peanuts and peanut butter
  • caffeine in all products, not just coffee
  • dairy products
  • yeast
  • some beans (which includes peanut), as well as broad, lima, Italian, lentil, soy, peas
  • avocados
  • dried meats
  • sauerkraut
  • pickled herrings
  • canned soups and packet soup mixes
  • chicken livers
  • banana
  • soya products as well as the bean itself
  • sodium nitrate, which is used to preserve hot dogs, bacon and cured meats
  • the preservative benzoic acid and its associated compounds
  • MSG, common name for monosodium glutamate, a flavor enhancer. Eating foods (such as Chinese food) prepared with monosodium glutamate is often cited as a trigger. Interestingly, research has not confirmed that this is true. If it were true, then one would also expect a greater prevalence of headache in Chinese people. The incidence, however, is the same as in other populations.
  • nuts
  • sourdough breads
  • cheeses which have been aged, i.e. cheddar
  • red wines, beer, champagne, vermouth
  • chocolate
  • anchovies

A number of metabolic, toxic or environmental triggers are:

  • Certain medications
  • Eating or drinking iced foods and fluids
  • The use or withdrawal of alcohol ("hangover"), caffeine, or other analgesic drugs (Medication Overuse Headache)
  • Breathing in smoke or fumes from chemicals
  • Repeated exposure to nitrate compounds (found in heart medicine and dynamite; also used in a meat preservative; sodium nitrate – such as in hot-dogs and bacon)
  • Exposure to materials containing chemical solvents (for example benzene, turpentine, spray adhesives, rubber cement and certain inks)
  • Exposure to poisons such as insecticides, lead and carbon tetrachloride
  • Use of drugs such as amphetamines
  • High altitudes (above 4 500m)
  • High blood sugar (hyperglycemia)
  • Low blood sugar (hypoglycemia)
  • Low calcium levels in the blood (hypocalcaemia)
  • Kidney failure (uraemia)

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