Migraine

Migraine is a chronic neurological disorder characterized by recurrent moderate to severe headaches often in association with a number of autonomic nervous system symptoms. The word derives from the Greek ἡμικρανία (hemikrania), "pain on one side of the head", from ἡμι- (hemi-), "half", and κρανίον (kranion), "skull".

Typically the headache affects one half of the head, is pulsating in nature, and lasting from 2 to 72 hours. Associated symptoms may include nausea,vomiting, and sensitivity to light, sound, or smell. The pain is generally made worse by physical activity.^] Up to one-third of people with migraine headaches perceive an aura: a transient visual, sensory, language, or motor disturbance which signals that the headache will soon occur. Occasionally an aura can occur with little or no headache following it.

Migraines are believed to be due to a mixture of environmental and genetic factors. About two-thirds of cases run in families. Changing hormone levels may also play a role, as migraines affect slightly more boys than girls before puberty, but about two to three times more women than men The risk of migraines usually decreases during pregnancy. The exact mechanisms of migraine are not known. It is, however, believed to be a neurovascular disorder. The primary theory is related to increased excitability of the cerebral cortex and abnormal control of pain neurons in the trigeminal nucleus of thebrainstem.

Initial recommended management is with simple analgesics such as ibuprofen and paracetamol (also known as acetaminophen) for the headache, anantiemetic for the nausea, and the avoidance of triggers. Specific agents such as triptans or ergotamines may be used by those for whom simple analgesics are not effective. Globally, approximately 15% of the population is affected by migraines at some point in life.

Signs and symptoms

Migraines typically present with self-limited, recurrent severe headache associated with autonomic symptoms. About 15-30% of people with migraines experience migraines with an aura and those who have migraines with aura also frequently have migraines without aura. The severity of the pain, duration of the headache, and frequency of attacks is variable. A migraine lasting longer than 72 hours is termed status migrainosus There are four possible phases to a migraine, although not all the phases are necessarily experienced:

1. The prodrome, which occurs hours or days before the headache
2. The aura, which immediately precedes the headache
3. The pain phase, also known as headache phase
4. The postdrome, the effects experienced following the end of a migraine attack

Prodrome phase

Prodromal or premonitory symptoms occur in about 60% of those with migraines, with an onset of two hours to two days before the start of pain or the aura. These symptoms may include a wide variety of phenomena, including altered mood, irritability, depression or euphoria, fatigue, craving for certain food, stiff muscles (especially in the neck), constipation or diarrhea, and sensitivity to smells or noise. This may occur in those with either migraine with aura or migraine without aura.

Aura phase

An aura is a transient focal neurological phenomenon that occurs before or during the headache.^[15] Auras appear gradually over a number of minutes and generally last fewer than 60 minutes. Symptoms can be visual, sensory or motor in nature and many people experience more than one. Visual effects occur most frequently; they occur in up to 99% of cases and in more than 50% of cases are not accompanied by sensory or motor effects. Vision disturbances often consist of a scintillating scotoma (an area of partial alteration in the field of vision which flickers and may interfere with a person's ability to read or drive). These typically start near the center of vision and then spread out to the sides with zigzagging lines which have been described as looking like fortifications or walls of a castle. Usually the lines are in black and white but some people also see colored lines. Some people lose part of their field of vision known as hemianopsia while others experience blurring.

Sensory aurae are the second most common type; they occur in 30–40% of people with auras. Often a feeling of pins-and-needles begins on one side in the hand and arm and spreads to the nose-mouth area on the same side. Numbness usually occurs after the tingling has passed with a loss of position sense. Other symptoms of the aura phase can include speech or language disturbances, world spinning, and less commonly motor problems. Motor symptoms indicate that this is a hemiplegic migraine, and weakness often lasts longer than one hour unlike other auras.

Rarely, an aura occurs without a subsequent headache;^[20] this is known as a silent migraine. However, it is difficult to assess the frequency of such cases, because patients who do not experience symptoms severe enough to drive them to seek treatment, may not realise that anything special is happening to them, and pass it off without reporting anything.

Pain phase

Classically the headache is unilateral, throbbing, and moderate to severe in intensity. It usually comes on gradually and is aggravated by physical activity. In more than 40% of cases however the pain may be bilateral, and neck pain is commonly associated. Bilateral pain is particularly common in those who have migraines without an aura. Less commonly pain may occur primarily in the back or top of the head. The pain usually lasts 4 to 72 hours in adults. however in young children frequently lasts less than 1 hour. The frequency of attacks is variable, from a few in a lifetime to several a week, with the average being about one a month.

The pain is frequently accompanied by nausea, vomiting, sensitivity to light, sensitivity to sound, sensitivity to smells, fatigue and irritability. In a basilar migraine, a migraine with neurological symptoms related to the brain stem or with neurological symptoms on both sides of the body, common effects include a sense of the world spinning, light-headedness, and confusion. Nauseaoccurs in almost 90% of people, and vomiting occurs in about one-third. Many thus seek a dark and quiet room. Other symptoms may include blurred vision, nasal stuffiness, diarrhea, frequent urination, pallor, or sweating Swelling or tenderness of the scalp may occur as can neck stiffness. Associated symptoms are less common in the elderly.

Postdrome

The effects of migraine may persist for some days after the main headache has ended; this is called the migraine postdrome. Many report a sore feeling in the area where the migraine was, and some report impaired thinking for a few days after the headache has passed. The patient may feel tired or "hung over" and have head pain, cognitive difficulties, gastrointestinal symptoms, mood changes, and weakness. According to one summary, "Some people feel unusually refreshed or euphoric after an attack, whereas others note depression and malaise."

Cause

The underlying causes of migraines are unknown. However, they are believed to be related to a mix of environmental and genetic factors.They run in families in about two-thirds of cases^[5] and rarely occur due to a single gene defect.  While migraines were once believed to be more common in those of high intelligence, this does not appear to be true. A number of psychological conditions are associated, including depression, anxiety, and bipolar disorder, as are many biological events or triggers.