Migraine

What is Migraine?

Migraines are recurrent headaches which can occur in conjunction with gastrointestinal and visual symptoms. The name is derived from the Greek word meaning 'pain in half the head', as migraines often produce a unilateral (one-sided) headache.

The headache or migraine is due to vasodilation or oedema of intra- and extra-cranial blood vessels and the subsequent stimulation of nerve endings near these blood vessels.

Types of migraine

There are several types of migraine - the two main types are classical migraine and common migraine.

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Classical migraines are preceded by an aura (neurological symptoms which develop before the headache). This may include visual symptoms (e.g. zig-zagging lines, flashing lights, loss of half the visual field, scotoma (loss of a small area of vision), or it may include other symptoms such as weakness, loss of sensation in the limbs or inability to talk.

The aura may last from 15 minutes up to an hour and the headache then follows often beginning locally and then becoming generalised. Nausea and vomiting then follow. The migraine lasts for several hours and the patient may then fall into a deep sleep.

Common migraines are not preceded by an aura. The headache lasts 4-72 hours, and is pulsating and unilateral. Nausea and vomiting, photophobia (pain from bright light) and phonophobia (pain from noise) may occur.

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Statistics on Migraine?

Migraine is common, affecting at least one in 10 people. It is more common in females and most frequently affects those between 20 and 50 years of age. 25% of migraines first occur in childhood.

Risk Factors for Migraine

The exact cause of migraine is not known. However, migraine headaches are thought to result from a combination of environmental factors (such as diet or stress) interacting with biochemical factors in the brain. Around 70% of migraine sufferers have a family history of migraine, suggesting a genetic component.

There are a number of 'triggers' which seem to cause migraines in susceptible people:

Stress or tension: and in particular the relief of tension after a stressful period (sometimes known as 'weekend migraine')
Tiredness, physical exhaustion, oversleeping
Alcohol (especially red wine).
Some foods: foods high in tyramine, such as aged cheese, or high in phenylalanine, such as chocolate
Hormonal factors: puberty, menstruation, pregnancy
Exercise
Some medications: vasodilators (drugs used to treat angina, high blood pressure, or erectile dysfunction), oestrogens (such as the oral contraceptive pill), MSG, or nitrites
Strong sensory stimulation, eg. glare or bright light, strong smells, loud noise
Head trauma

Progression of Migraine

The frequency of migraine headaches varies greatly between patients. They may be more frequent around times of hormonal change, such as puberty or menopause.

Migraine headaches can be preceded by an aura (classical migraine) which may last from 15 minutes to an hour. 'Aura' refers to symptoms such as flashes of light or visual changes, thought to be caused by disturbances in the electrical activity of the brain. After the aura, the headache begins. The headache usually lasts 6-8 hours, although it can last for up to 72 hours. Nausea and vomiting may follow the onset of the headache.

Not all patients with migraines experience aura. Migraine headache without aura is known as 'common migraine'.

A migraine may occur at any time of day. Migraine headaches resolve on their own, often after sleep. However, many patients feel drained and tired and may experience muscle aches for up to a day after the headache resolves.

Symptoms of Migraine

The pain of migraine headache is typically described as unilateral (one-sided) and throbbing. It is present behind the eye and extends around the scalp to the occiput (back of the head).

How is Migraine Diagnosed?

Usually, no tests are needed for diagnosis of migraine headache. However, sometimes a sudden severe headache is caused by a serious condition other than migraine (such as intracranial haemorrhage, brain tumour, meningitis or temporal arthritis). If these conditions cannot be excluded clinically, the following tests may be required:

CT or MRI scan of the head.
ESR (for temporal arthritis)
Blood cultures (if the temperature is elevated and meningitis is suspected)
Lumbar puncture: if CT is normal but subarachnoid haemorrhage is still suspected.

Prognosis of Migraine

Migraine is not a life-threatening condition, although the attacks (especially the aura) can be very frightening and can mimic strokes. Nothing can be done to 'cure' the patient from this condition however the symptoms of an attack can be relieved with appropriate treatment and measures can be taken to reduce the frequency of attacks.

Migraine symptoms often change over time, and can become less severe. This is often the case when women who suffer migraine reach menopause.

How is Migraine Treated?

Migraine Treatment can include non-medication and medication approaches. Therapy that does not involve medications can be both symptomatic and preventative therapy. Using ice, biofeedback, and relaxation techniques may be helpful at stopping an attack once it has started.

Patients should learn to identify and avoid the triggers that can lead to an attack.

Individuals with occasional mild migraine headaches that do not interfere with daily activities usually medicate themselves with over-the-counter (OTC, non-prescription) pain relievers such as paracetamol, aspirin, or NSAIDs (eg. ibuprofen).

Moderate to severe migraine attacks may require different types of medication.

5HT-1 agonists: these include drugs such as sumatriptan and zolmitriptan. They may be taken orally, by nasal spray, or as injections. Their efficacy varies greatly between patients and they usually need to be taken early in an attack to be effective. Triptans should be avoided in patients with vascular disease.
Dopamine antagonists: including metoclopramide or parenteral chlorpromazine. These medications can reduce the nausea and vomiting associated with migraine, and can also help improve absorption of other migraine tablets.

Prophylaxis

For people who suffer migraines very frequently, preventative medications that are taken on a daily basis may be a good option. As a general rule, patients who experience migraines twice or more per month or have migraines which interfere with their quality of life may benefit from prophylactic (preventative) medication.

Many different types of medication are available which can help prevent migraine:

B-adrenergic antagonists: propranolol, metoprolol or atenolol
Anticonvulsants: Topiramate and sodium valproate in particular have been evaluated in a large number of clinical trials and have been shown to reduce frequency of migraine attacks
Tricyclic antidepressants: low-dose nortriptyline, amitriptyline
Pizotifen: this medication has antihistamine and 5-HT antagonist effects, however common side effects include drowsiness and weight gain
Calcium channel blockers: nifedipine, verapamil
Phenelzine, methysergide: these medications should be reserved for severe, unresponsive migraine as they have potentially serious side effects.

Migraine References

Braunwald, Fauci, Kasper, Hauser, Longo, Jameson. Harrison's Principles of Internal Medicine. 16th Edition. McGraw-Hill. 2001
Chronicle EP, Mulleners WM. Anticonvulsant drugs for migraine prophylaxis. Cochrane Database of Systematic Reviews 2004, Issue 3. Art. No.: CD003226. DOI: 10.1002/14651858.CD003226.pub2
Hankey G., Wardlaw J. Clinical Neurology. Demos Medical Publishing, United Kingdom, 2002.
Kumar P, Clark M. Clinical Medicine. WB Saunders 2002;
Murtagh, J. General Practice. Second Ed. McGraw-Hill, 1998. pp 683-684