Introduction

Headache is one of the most common symptoms leading patients to consult general practitioners and neurologists. About 1 in every 20 GP consultations is for headache. It is estimated that there are 190,000 migraine attacks experienced every day in England, and 25 million work or school days are lost because of them each year.^[1]

It occurs most often between late teenage years and age 50, so that it is very disruptive to people's work and lives. Despite this high prevalence, and the impact on people and the economy, migraine is considered to be both under-diagnosed and under-treated.^[2] Migraine prophylaxis is particularly underused.

Classification

In 1988 the International Headache Society produced a classification of migraine. This clarified diagnostic criteria and put the emphasis for diagnosis on a good history. It was revised in 2002. There is also a shorter version that appeared in 2004.^[3] It classified migraine as:

• Migraine without aura that occurs in about 75% (formerly called common migraine).
• Migraine with aura that occurs in about 20% (formerly called classic migraine).
• Childhood periodic syndromes that frequently progress to migraine-like cyclical vomiting and abdominal migraine.
• Retinal migraine.
• Complications of migraine. These include chronic migraine, status migrainosus, migrainous infarction and migraine-triggered seizure.
• Probable migraine.

This article will concentrate on the common varieties of migraine.

Pathophysiology

Migraine was formerly thought to be caused by changes in blood vessels. New imaging techniques suggest that the cause lies within the brain (possibly the dorsolateral pons). Functional imaging during attacks suggests a disorder of brain function.^[4] This may explain some of the odd sensations experienced by patients during attacks (such as muddled thinking, poor concentration, etc.) and facilitate better explanation. It also better directs research into new migraine treatments, particularly those which may prevent attacks.^[5]

Epidemiology

• Numbers may be misleading, as many sufferers do not consult their GP.
• Migraine affects about 6% of men and 18% of women.^[6]
• In children it is more common in boys than in girls.
• The one-year prevalence of migraine is 15% in women, and 6% in men.
• The first attack is often in childhood and over 80% have had their first attack by the age of 30.
• If the onset is at age over 50, other pathology should be sought.
• Usually severity decreases with advancing years.
• A practice of 2,000 can expect about five new cases a year and 40 consultations for existing migraine.
• There is a family history in many.

History

The history gives the diagnosis (there are no diagnostic tests for migraine). It can be useful for patients to keep a headache diary. This can save time and help to identify the type or types of headache experienced.^[7]

Migraine is characterised by the following:

• Paroxysmal headaches that tend to be severe and often unilateral, although in 30%-40% it is bilateral.
• There may be a premonitory phase in 20%-60% of those with migraine. There may also be an aura. There may be photophobia and vomiting with marked headache but the course is highly variable.
• The resolution phase occurs as the headache gradually fades.
• The person may feel tired, irritable, depressed and have difficulty concentrating.

It can be appreciated how important a good history is by considering the box and diagnostic criteria below.

Migraine without aura

This is a recurring disorder, and the diagnosis is not made until the patient has a history of at least five attacks. The headaches should not be secondary to any other headache disorder (exclude by history and examination) - see separate Headache article.

Typically the headaches last between 4 and 72 hours and have at least two of the following features:

• Unilateral.
• Pulsating.
• Moderate or severe intensity of pain.
• Aggravated by, or resulting in the avoidance of, routine physical activity.

In addition, there is at least one of:

• Nausea. This occurs in 80%-90% of migraineurs.
• Vomiting. This occurs in 40%-60% of migraineurs.
• Photophobia. This too is common and occurs in 80% of migraineurs.
• Phonophobia. This occurs in 75%-80% of migraineurs.

General light-headedness is experienced by 70%. It is thus important to stress that migraine can be bilateral and be associated with phonophobia. Tension-type headache (TTH) tends to be over-diagnosed and migraine under-diagnosed in general practice.

Migraine with aura

This affects about a third of migraine sufferers, and is usually easier to diagnose. The premonitory phase is different from an aura and occurs hours to days before the headache. There may be a feeling that a migraine is imminent. Common features are depression, tiredness, difficulty concentrating, irritability, stiff neck and food cravings. Many different features can be present but they tend to be consistent for the individual.

Aura is also highly variable in nature but it also tends to be constant for the individual. Typically, aura symptoms are progressive, of gradual onset over minutes, last five minutes to an hour and occur before the headache:

• Visual disturbance starts in one eye and may spread. It may be homonymous, ie it affects just one side of the visual field but in both eyes. A fortification spectrum is common or a spreading, scintillating scotoma in the shape of a jagged crescent. Geometric visual patterns and even hallucinations may occur. This is fully reversible. An aura has no motor symptoms.
• Sufferers may also have sensory symptoms (paraesthesia or numbness) that are unilateral and also fully reversible. Numbness usually starts in the hand and moves up the arm before involving the face, lips and tongue. The leg is sometimes affected. Numbness may follow the paraesthesia. Sensory auras rarely occur alone and usually follow visual auras.
• The headache either begins before the end of the aura or within an hour of the end and has the same features as migraine without aura (above).
• One patient may at different times have migraine attacks with and without aura. Sometimes no headache may follow a typical aura - but always consider the possibility of transient ischaemic attack (TIA) rather than migraine in these patients, particularly if the patient says the aura was different from their usual aura.^[9].

Migraine in children

The classification of migraine has been modified for children, allowing for headache with fewer associated features:

• Migraine often starts in childhood and is more common than is realised.
• Childhood periodic syndromes (including cyclical vomiting and abdominal migraine) are thought by many to be a precursor of migraine.
• Features of migraine in children are fairly similar to those of adults, including being completely well between attacks. However, the headache is often bilateral or in the middle of the head, and gastrointestinal symptoms are more prominent.^[9]
• Attacks may be shorter and last between 1 and 72 hours.^[9]
• Some features are inferred from the child's behaviour, like covering the eyes or ears, closing the curtains and wanting to lie in a quiet dark room.

Menstrual migraine

• This is migraine without aura, occurring regularly within a day or two of the onset of menstruation and at no other time.
• It is probably due to falling oestrogen levels.
• Timing is critical for this diagnosis. Only 14% of women with migraine suffer from menstrual migraine but up to 60% suffer from menstrual-associated migraine.
• Migraine diaries can accurately differentiate menstrual migraine from menstrual-associated migraine. This is important, as the preventative treatment of menstrual migraine is different from that of menstrual-associated migraine.

Examination

Always examine the following in patients with headache:^[9]

• Optic fundi.
• Blood pressure.
• Head and neck (scalp, neck muscles and temporal arteries).
• Head circumference in children.

Neurological examination between attacks is normal. Abnormalities suggest another cause.

Examination during an attack may reveal localised oedema of the scalp, face, or under the eyes; scalp tenderness; prominence of temporal blood vessels; neck stiffness and tenderness.

Investigations

Investigations are required only to exclude an alternative diagnosis if one is suspected. If second-line treatment of acute symptoms fails, or diagnosis of migraine is not certain, referral to a neurologist is usually required.

The following are suggestive of more serious pathology:

• Headache of new onset after 50 years of age or under 10 years of age.
• Headache with an atypical aura (eg aura lasting more than one hour or with muscular weakness).
• Systemic symptoms like myalgia, fever, malaise or weight loss.
• Described as the worst headache of the patient's life, especially if it was rapid in onset.
• A change in frequency, severity, or clinical features of the attack from what is normally experienced.
• A new progressive headache that persists for days.
• Precipitation of headache by Valsalva manoeuvres, as in coughing, sneezing or bearing down.
• Scalp tenderness or jaw claudication.
• Focal neurological abnormalities or confusion, seizures or impaired level of consciousness.
• Focal neurological findings that occur with the headache and persist temporarily after the pain resolves suggest a migraine variant. In hemiplegic migraine, the patient may have paralysis of one side of the body and possibly aphasia. In ophthalmoplegic migraine, the patient may present with a third nerve palsy, with ocular muscle paralysis, including or sparing the pupillary response, as well as ptosis. This is more common in children, with the abnormal motor findings lasting hours to days after the headache.

Differential diagnosis

The most severe and disabling headaches are usually primary headaches:

• Cluster headache.^[11] This is a severe recurrent headache with characteristic periodicity and pronounced autonomic features. The genetics differ from migraine.
• Tension-type headache (TTH).^[12] This is common. It lacks the specific features of migraine with none of the range of associated symptoms (featureless head pain). It can produce attacks of headache but is usually generalised (tight, band-like character) and arises from the neck. It can, of course, occur together with migraine.
• Medication overuse headache (MOH).^[13] This has also been called drug or analgesic abuse headache. Classically it occurs with incorrect use of codeine but can occur with other analgesics (aspirin, paracetamol, ergotamine, triptans, etc). It can be difficult to treat and often requires admission. It is best prevented with good advice when treatment is initiated.
• Chronic daily headache. This is really a convenient label for headache which occurs for months on more than 50% of days. It excludes cluster headache and chronic migraine (migrainous headache occurring every day) but includes TTH and MOH.
• Sinusitis. Ethmoid sinusitis can produce headache similar to migraine.
• Brain tumour is rarely the cause of a headache, especially in the absence of other symptoms.
• Temporal arteritis.
• Pseudotumour cerebri.
• Cerebrovascular pathology (for example, leaking berry aneurysm, stroke and transient cerebral ischaemia).

Some headaches cannot easily be diagnosed and the British Association for the Study of Headaches, amongst others, recognises this.^[9] In such cases it is important to exclude serious pathology.

Management

The separate article Migraine Management covers this in detail. In general the aim should be:

• To relieve the symptoms of an acute attack of migraine.
• To reduce the frequency and severity of migraine attacks.
• To identify possible trigger factors.

Migraine management covers the different drugs used for acute attacks.

General measures include identification and avoidance of trigger factors. A migraine diary is often helpful for this. Other therapies include relaxation therapy, biofeedback, cognitive or behavioural therapy, psychotherapy, acupuncture and hypnosis. All have their advocates but good evidence of efficacy is lacking.

Migraine prophylaxis may be used if attacks are happening at least twice a month or tend to be severe or prolonged. It may also be employed if there is overuse of medication. If medication is required once or twice a week then prophylaxis should certainly be considered. See separate article Migraine Prophylaxis in Adults.

Associated conditions

Migraine and contraception

There is much evidence that migraine with aura is associated with a two-fold increased risk of ischaemic stroke.^[14][15] Other risk factors for stroke, like use of the combined oral contraceptive pill (COCP), high blood pressure or smoking, have multiplicative effects on the risk for ischaemic stroke. Contra-indications for the use of COCPs in women with migraine are based on expert opinion. They are intended to enable most women with migraine to use COCPs safely with minimal risk of ischaemic stroke, while protecting those at higher risk.

If an aura occurs for the first time while a woman is using the COCP, she should stop the pill immediately, use emergency contraception if necessary and consider other methods.

Advice is to avoid the COCP in:^[16]

• Migraine with aura.
• Migraine without aura if there is more than one additional risk factor for stroke. These include age 35 years or over, diabetes mellitus, close family history of arterial disease in those under 45 years of age, hyperlipidaemia, hypertension, obesity or smoking.
• If the headache phase lasts over 72 hours it is called status migrainosus.
• If the migraine is treated with ergot derivatives.

Which contraceptives can be used?

• Women with migraine without aura and no additional risk factors for ischaemic stroke may use a COCP. If focal symptoms start, or frequency increases, the COCP should be stopped due to the risk of ischaemic stroke.
• All other forms of contraception are acceptable, including progestogen-only pills and depot and implant hormonal contraception.

Pregnancy and breast-feeding

Migraine often improves during pregnancy, only to return to its former pattern after delivery. Paracetamol is the drug of choice for use in pregnancy and breast-feeding.

• Ibuprofen or aspirin may be used but should be avoided after 30 weeks because of the risk of premature closure of the ductus arteriosus. Aspirin should be avoided by breast-feeding mothers, due to the potential risk of Reye's syndrome.
• Promethazine is the anti-emetic of choice although it is not prokinetic.
• Triptans should be avoided in pregnancy and breast-feeding because of limited evidence of safety.
• If prophylaxis must be used, propranolol or amitriptyline could be considered.

Complications

• Migraine is associated with an increased risk of depression, manic depression, anxiety disorder and panic disorder.
• Status migrainosus is defined as a debilitating migraine that lasts for more than 72 hours.
• Migrainous infarction is when a cerebral infarction occurs during the course of a typical attack of migraine with aura. The aura lasts over an hour and neuro-imaging shows ischaemic infarction. Migraine is associated with increased risk of ischaemic, but not haemorrhagic, stroke. A meta-analysis of 14 studies showed that the relative risk of ischaemic stroke was 2.16 (confidence interval 1.89 to 2.48). This meta-analysis also showed that oral contraceptive use increased risk of ischaemic stroke approximately eight-fold compared with non-users.^[17]

Prognosis

Many children and adolescents with migraine find that their attacks cease during adulthood. This is unpredictable and a few continue to suffer attacks into old age.