Definition & Classification

Migraine is a primary neurobiologic disorder, resulting from dysfunction of the trigeminovascular system. The disorder manifests as recurring attacks, usually lasting 4-72 hours. These attacks, which can interfere with normal functioning, involve unilateral throbbing headache pain of moderate to severe intensity. They also usually involve nausea, sometimes vomiting, and light, sound, and sensitivity to other sensory stimuli.

Types of Headache

There are many different types of headache, and an accurate diagnosis is critical to the physician’s therapeutic recommendation. Diagnosis is complicated not only because different types of headache exist but also because a patient may suffer from more than one type of headache. The classification system that the Headache Classification Committee of the International Headache Society (IHS) published in 1988 lists more than 100 types of headache [IHS, 1988]. Many of these are attributable to other pathologic conditions (i.e., they are secondary headaches). Others – such as migraine, tension-type headache, and cluster headache – have no obvious underlying cause and are considered primary headache disorders. The following table lists some of the most important primary and secondary types of headache and their prevalence.

Clinical Classification of Headache Disorders and Prevalence of Different Types in the Population

Primary Headache Secondary Headache

Type Prevalence (%) Type Prevalence (%)

Tension-type headache 69 Systemic infection 63

Migraine 15 Head injury 4

Idiopathic stabbing headache 2 Drug-induced headache 3

Exertional headache 1 Vascular disorders 1

Cluster headache 0.1 Subarachnoid headache <1

Adapted from Rasmussen [1995]; with permission.

Tension-type Headaches

The most common form of headache is tension-type headache, which about 69% of the population experiences at some point in life [Rasmussen, 1995]. Such headaches are mild to moderate in intensity and nonthrobbing. They have a "pressing" or "tightening" quality and are generally bilateral. Tension-type headaches can last from 30 minutes to 7 days for each attack. They are classified as episodic if they occur less than 15 days per month and chronic if they occur 15 days or more each month for 6 months or more. Nausea may occur in patients with chronic tension-type headache, but it generally does not occur in patients with episodic tension-type headache. Ordinary physical activities do not usually aggravate tension-type headaches.

Cluster Headaches

Cluster headaches are extremely severe, unilateral headaches that produce pain in the area around and above the eye; this pain may extend back toward the ear. Cluster headaches are commonly associated with one or more of the following signs or symptoms: redness of the eye, lacrimation, nasal congestion, rhinorrhea, forehead and facial sweating, contraction of the pupil of the eye, drooping of the eyelid, or a puffy eyelid on the affected side of the head. These attacks last 15 minutes to 3 hours, occurring as often as eight times daily. Cluster headaches occur in series that last from weeks to months, interrupted by remission periods that last from months to years. Because the episodes tend to "cluster" in time, they are referred to as cluster headaches. Cluster headaches occur predominantly in men. A variation of the cluster headache, termed chronic paroxysmal hemicrania, produces symptoms similar to those of cluster headache, but such headaches are more frequent in occurrence and shorter in duration. This type of headache occurs predominantly in women.

Migraine headaches, in contrast, are longer in duration, do not tend to occur in clusters, are not associated with symptoms localized to the ocular region of the head, may be associated with aura, and are more common in women.

Several miscellaneous types of headache can easily be distinguished from migraine because of their symptoms or initiating triggers.

Idiopathic stabbing headache: characterized by stabbing pains that occur at regular intervals, but last only a fraction of a second.
External compression headache: a constant pain precipitated by wearing a tight band (e.g., swim goggles) around the head.
Cold stimulus headache: precipitated by the ingestion of a cold substance (e.g., ice cream) or exposure of the head to cold temperatures.
Benign cough headache: precipitated by coughing.
Benign exertional headache: precipitated by exercise, lasting 5 minutes to 24 hours.
Headache associated with sexual activity: precipitated by sexual excitement.

Other Types of Headache

Secondary headaches are common in patients with systemic infections and may occur in association with head injury, vascular disorders, and the use or overuse of various drugs. As evidenced by the sheer number of classification types included in the IHS criteria, many pathologic conditions can precipitate headache. Thus, it is important that secondary causes of headache be excluded before making a diagnosis of migraine or other primary headache disorder.

Acute and chronic headaches can be precipitated by head trauma. These headaches tend to disappear within about 8 weeks of onset. Also, secondary headaches may be related to vascular disorders; disorders that change the pressure of cerebrospinal fluid; viral or bacterial infection; metabolic disorders; disorders of the eyes, ears, nose, sinuses, or other facial or cranial structures; and neuralgias. All these headache types can be distinguished from migraine based on specific symptoms and patient history. Unlike other forms of headache, migraine involves both head pain and symptoms associated with sensitivity to sensory stimuli (i.e., light, sound, and odor).

Finally, there is a phenomenon known as rebound headache, whereby headache medications that are taken daily or almost daily may perpetuate headaches. Rebound mechanisms are poorly understood and may cause headaches to become chronic, more severe, and less likely to respond to both acute and prophylactic treatments.

Migraine Headaches

Several types or classifications of migraine exist. Migraine may have a strong family history and may vary in frequency, intensity, duration, pattern of associated symptoms, and degree of disability. They are usually moderate to severe in intensity, and may be incapacitating. They are episodic in nature, with some patients experiencing one attack annually and others experiencing attacks several times a week. The average number of migraine attacks is about three or four per month. They generally last from 4-72 hours. Migraine headaches usually have a "pulsating" quality; the pain is described as "pounding" or "throbbing" in nature, and is usually unilateral.

The headache phase of a migraine is commonly associated with signs and symptoms such as nausea, photophobia, phonophobia, emesis, diarrhea, vertigo, tremors, sweating, irritability, confusion or loss of concentration, and chills. Normal physical activity typically exacerbates the pain.

Migraine may occur with or without an aura that, when present, generally lasts between 5 and 60 minutes. Aura occurs in about 15-20% of patients with migraine. The most common type of aura is visual; it can cause scotomas, teichopsia, fortification spectra, and photopsias.

Aura may also consist of virtually any type of neurologic symptom, such as focal paresthesia or weakness, visual or auditory hallucination, vertigo, fainting, or a confusional episode.

In most patients who experience aura, the aura develops before the head pain begins, but on occasion an aura may appear or recur when the headache is most intense. An aura is present before every migraine attack in some individuals, but in other patients, aura accompanies only a small proportion of attacks. The intensity of aura varies among attacks; it may be vivid and impressive or nearly indiscernible. The symptoms of aura may remain constant from attack to attack in a particular person or may vary in successive attacks in the same person. Also remember that aura only occurs in a minority of patients with migraine.

Furthermore, premonitory symptoms, called prodrome, may precede migraine attack; these symptoms occur 24-72 hours before the onset of other symptoms. During this period, patients may experience feelings of well-being, talkativeness, surges of energy, hunger, anorexia, drowsiness, excessive yawning, depression, irritability, restlessness, or tension.

Classification of Migraine

Migraine headaches are classified according to their clinical features, as well as according to current concepts of pathophysiology. Patients who have migraine without aura generally have normal cerebral blood flow and do not report focal neurologic symptoms. In those who have migraine with aura, changes in regional cerebral blood flow can be demonstrated and neurologic symptoms originating in the brain or brain stem are reported.

The current IHS classification system recognizes several subtypes of migraine with aura and several other specific types of migraine (see table below).

IHS Classification of Migraine

1. Migraine

1.1 Migraine without aura

1.2 Migraine with aura

1.2.1 Migraine with typical aura

1.2.2 Migraine with prolonged aura

1.2.3 Familial hemiplegic migraine

1.2.4 Basilar migraine

1.2.5 Migraine aura without headache

1.2.6 Migraine with acute onset aura

1.3 Ophthalmoplegic migraine

1.4 Retinal migraine

1.5 Childhood periodic syndrome that may be precursors to or associated with migraine

1.5.1 Benign paroxysmal vertigo of childhood

1.5.2 Alternating hemiplegia of childhood

1.6 Complications of migraine

1.6.1 Status migrainosus

1.6.2 Migrainous infarction

1.7 Migranous disorders not fulfilling above criteria

Adapted from IHS [1988]; with permission.

Migraine without aura

Migraine without aura is an idiopathic recurring headache disorder that manifests in the form of attacks that last 4-72 hours. Typically, the headaches are unilateral, have a pulsating quality, and are moderate to severe in intensity. These headaches are aggravated by routine physical activity and are associated with nausea or vomiting, photophobia, and phonophobia.

Migraine with aura

Migraine with aura is also an idiopathic recurring disorder that manifests in some women as migraine without aura but is also accompanied by transient neurologic symptoms. Aura symptoms usually develop gradually, over 5-20 minutes, and last less than 60 minutes. Headache, nausea, or photophobia usually follow neurologic aura symptoms directly or after a free interval of less than 1 hour. The headache usually lasts 4-72 hours, but rarely will be completely absent (migraine aura without headache).

The six subtypes of migraine with aura are:

Migraine with typical aura: migraine characterized by an aura consisting of unilateral visual disturbances, sensory disturbances, and muscular weakness or partial paralysis. The aura develops gradually, lasts less than 1 hour, and is completely reversible.
Migraine with prolonged aura: migraine accompanied by an aura that lasts more than1 hour but less than 1 week. Diagnostic studies must fail to show evidence of neurologic disease.
Familial hemiplegic migraine: a rare migrainous disorder that runs in families and involves an aura characterized by muscular weakness or partial paralysis on one side of the body.
Basilar migraine: an uncommon migrainous disorder in which the aura clearly originates from the brain stem or from both occipital lobes of the brain. It may be accompanied by dramatic neurologic events, such as total blindness, followed by vertigo, incoordination, difficulty speaking or concentrating, and other signs and symptoms.
Migraine aura without headache: a migrainous aura that is not associated with a headache.
Migraine with acute onset aura: a migraine headache in which the aura develops fully in less than 5 minutes.

Other types of migraine

Ophthalmoplegic migraine, an extremely rare condition that may affect the ocular nerves, is characterized by drooping of the eyelids and dysfunction of the extraocular muscles that results in double vision. Another rare form of migraine is retinal migraine, in which inadequate blood supply to the retina results in a scotoma or transient blindness affecting one eye. This differs from the visual disturbances usually associated with migraine aura in that only one eye is affected in retinal migraine compared with the visual disturbances being perceived in both eyes in migraine with visual aura.

Many recurrent disorders that occur in childhood have migraine-like features and may represent precursors to typical migraine syndromes or alternative forms of migraine. Although not all of these disorders have been classified, the IHS classification of headache disorders lists two such syndromes along with diagnostic criteria.

Benign paroxysmal vertigo of childhood is characterized by recurrent attacks of vertigo, which is an illusory sense that either the environment or one’s own body is moving or rotating. Alternating hemiplegia of childhood is a disease that occurs primarily in infants and is characterized by muscle weakness or partial paralysis on one side of the body. Different sides of the body can be affected during different attacks, and each attack is accompanied by other neurologic phenomena, some of which are reminiscent of epilepsy.

Complications of migraine include status migrainosus, in which the headache phase of a migraine attack lasts more than 72 hours despite treatment. Another very rare complication of migraine is migrainous infarction, in which one or more aura symptoms is not reversible within 7 days of onset or diagnostic studies indicate that an associated area of the brain has had a stroke due to inadequate blood supply.

Stages of a migraine attack

Patients with migraine typically experience moderate to severe, unilateral headaches associated with nausea or vomiting, photophobia, and phonophobia. In Phase I, about 20% of patients experience prodromal symptoms such as mood changes, hypoactivity or hyperactivity, food cravings, fluid retention, and hypersensitivity to light, sound, or smell (see figure below). Phase II consists of the migraine aura, which includes various transient neurologic (usually visual) symptoms that last 5-60 minutes.

Symptoms and Signs during Phases of "Complete" Migraine Attacks with Aura

Adapted from Blau [1992]; with permission.
Click on image for larger version.

Phase III is the headache phase, whereas Phase IV represents the resolution phase, during which the intensity of migraine symptoms gradually abates. Many migraine headaches resolve while a patient sleeps.

The last phase of a migraine, Phase V, is the recovery period, or postdrome, during which the headache has resolved, but the patient feels tired and has a limited tolerance for food. If fluid retention characterized the prodromal period (Phase 1), a period of diuresis may occur.

References

Blau JN. Migraine: theories of pathogenesis. Lancet.1992;339:1202-1207.

International Headache Society. Classification and diagnostic criteria for headache disorders, cranial neuralgias and facial pain. Headache Classification Committee of the International Headache Society. Cephalagia. 1988:8(suppl 7):1-96.

Rasmussen BK. Epidemiology of headache. Cephalagia. 1995;15:45-68.

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