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Monday, September 28, 2009

migraine

Migraine - classic; Headache - migraine with aura
Definition Return to top
Migraine is a neurological disorder that generally involves repeated headaches. Some people also have nausea, vomiting, and other symptoms.
Most people with migraines do not have any warning before it occurs. However, some people have a visual disturbance called an aura before the headache starts.
Causes Return to top
A migraine is caused by abnormal brain activity, which is triggered by stress, food, or something else. The exact chain of events is not known. However, it seems to involve various nerve pathways and chemicals in the brain. The changes affect blood flow in the brain and surrounding membranes.
Migraines occur in women more than men, most often between the ages of 10 and 46 years. In some cases, they appear to run in families.
Migraine attacks may be triggered by:
Allergic reactions
Bright lights
Loud noises
Physical or mental stress
Changes in sleep patterns
Smoking or exposure to tobacco smoke
Missed meals
Alcohol
Hormonal fluctuations (related to menstrual cycles or use of birth control pills)
Foods associated with migraine include:
Foods containing the amino acid tyramine (red wine, aged cheese, smoked fish, chicken livers, figs, some beans)
Chocolates
Nuts and peanut butter
Fruits (avocado, banana, citrus fruit)
Onions
Dairy products
Baked goods
Meats containing nitrates (bacon, hot dogs, salami, cured meats)
Foods containing monosodium glutamate (MSG)
Any processed, fermented, pickled, or marinated foods
True migraine headaches are not a result of underlying brain tumors or other serious medical problems. However, only an experienced health care provider can determine whether headache symptoms represent migraine or some underlying medical condition that requires further tests. This assessment can only be made after a review of a patient's history and a complete neurological exam.
Symptoms Return to top
When a migraine begins with visual disturbances (aura), these warning symptoms may occur anywhere from a few minutes to 24 hours before the headache. The visual changes are common in one or both eyes. They may occur in any combination:
Seeing zigzag lines
Seeing flashing lights
Other visual hallucinations
Temporary blind spots
Sensitivity to bright light
Blurred vision
Eye pain
Other symptoms that may precede or accompany the headache include:
Loss of appetite
Nausea
Vomiting
Chills
Increased urination
Increased sweating
Swelling of the face
Irritability
Fatigue
The headache itself is often described as a "pounding" feeling that starts on one side of the head and may spread to the other side. For many patients, the headaches start on the same side each time. Many patients describe pain behind the eye or in the back of the head and neck.
The headache typically begins as a dull ache that progressively worsens over several minutes to hours to the point of disabling pain. The headache may last several hours to days, during which patients are sensitive to light or sound. Patients often wish to rest in a quiet, dark room.
Treatment Return to top
To learn what may be triggering your migraine headaches, keep a headache diary. Write down:
When your headaches occurred
How severe they were
Additional symptoms
What you've eaten
Sleep patterns
Menstrual cycles
Any other possible factors
For example, the diary may reveal that your headaches tend to occur more often on days when you awaken earlier than usual. Changing your sleep schedule may then result in fewer migraine attacks.
Some birth control pills and other medications may trigger headaches. Your health care provider should address questions regarding their use.
Even in the absence of a clear factor that triggers migraine attacks, try to keep a regular exercise and sleep schedule. Avoid smoking, caffeine, and alcohol. Some patients have found biofeedback and self-hypnosis to be effective at reducing the frequency of migraine attacks.
MEDICATION
Although there is no cure for migraine headaches, numerous medications are available. These medications are used to:
Prevent migraines from occurring
Stop the migraine once early symptoms develop
Treat the symptoms of migraine
All medications have potential side effects and may be incompatible with other medications you are taking. Also, many migraine medications are associated with birth defects and are therefore not safe to use during pregnancy.
Often, a health care provider will try several classes of medications before one (or a combination) is found to be effective.
PREVENTING MIGRAINES
Many medications can reduce the frequency of migraines. Generally, these need to be taken daily in order to be effective. These medications are less useful and tolerable to patients with infrequent headaches. Medications in this category include:
Beta-blockers such as propanolol
Anti-depressants such as amitriptyline
Anti-convulsants such as valproic acid and topiramate
Calcium-channel blockers such as verapamil
Serotonin re-uptake inhibitors such as venlafaxine
STOPPING AN ATTACK
Other medications are taken when there is the first sign of an impending migraine attack. In the case of migraine with aura, this is typically when the visual disturbances are first noted. These medications can effectively stop the migraine in its tracks, preventing the progression to other migraine symptoms or reducing the severity of the attack.
Many of these medications cause constriction of blood vessels and cannot be given to patients at risk of heart attack or other conditions. These medications include:
Ergots such as DHE-45
Serotonin agonists / triptans such as sumatriptan
Isometheptene
These medications come in various preparations to enable administration via different routes. For example, patients who have vomiting and cannot keep pills down may benefit from a nasal spray or injection.
Call for an appointment with your health care provider if you are taking an ergotamine-containing medication and you are likely to become pregnant. Such medications can have serious side effects to an unborn baby.
TREATING SYMPTOMS
Other medications are primarily given to treat the symptoms of migraine. Used alone or in combinations, these drugs can minimize pain, nausea, or emotional distress caused by the migraine. Some of these medications may also have some effect on the underlying process in addition to providing symptomatic relief. Medications in this group include:
Anti-emetics such as prochlorperazine
Sedatives such as butalbital
Non-steroidal anti-inflammatories (NSAIDs) such as ibuprofen
Acetaminophen (Tylenol)
Narcotic pain relievers such as meperidine
A headache which is preceded by some type of warning such as an aura or some other visual disturbance. An aura is a visual disturbance where the person feels a sensation of light. A headache is a pain in the head.
Symptoms of Classic migraine
§ - throbbing, or pounding in the forehead, temple, ear, jaw, or around the eye.
§ One-sided headache - that may move to the other side over time.
§ Nausea
§ Weakness
§ Vision disturbance
§ Light sensitivity
§ Aura - a set of specific symptoms affecting the brain and vision that will precede the onset of certain types of migraines, including:
§ Flashing lights
§ Seeing zigzag lines
§ Temporary vision loss
§ Speech difficulty
§ Arm tingling
§ Arm weakness
§ Leg weakness
§ Tingling face
§ Tingling hands
Migraine is a neurological syndrome characterized by altered bodily experiences, painful headaches, and nausea. It is a common condition which affects women more frequently than men.
The typical migraine headache is one-sided and pulsating, lasting 4 to 72 hours[1]. Accompanying complaints are nausea and vomiting, and a heightened sensitivity to bright lights (photophobia) and noise (hyperacusis).[2][3][4] Approximately one third of people who experience migraines get a preceding aura, in which a patient may sense a strange light or unpleasant smell.[5]
Although the exact cause of migraine remains unknown, the most widespread theory is that it is a disorder of the serotonergic control system. Recently, PET scans have demonstrated the aura to coincide with spreading cortical depression after an episode of greatly increased blood flow (up to 300% higher than baseline). There also appear to be migraine variants that originate in the brainstem and involve dysfunction in calcium and potassium ion transport between cell membranes. Genetic factors may also contribute.[6] Studies on twins show that genes have a 60 to 65% influence on the development of migraine.[7][8] Fluctuating hormone levels show a relation to migraine in several ways: three quarters of adult migraine patients are female while migraine affects approximately equal numbers of boys and girls before puberty,[citation needed] and migraine is known to disappear during pregnancy in a substantial number of sufferers.
The treatment of migraine begins with simple painkillers for headache and anti-emetics for nausea, and avoidance of triggers if present. Specific anti-migraine drugs can be used to treat migraine. If the condition is severe and frequent enough, preventative drugs might be considered.
The word migraine is French in origin and comes from the Greek hemicrania, as does the Old English term megrim. Literally, hemicrania means "half (the) head".

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[edit] Classification
Migraines have been classified by the International Headache Society which periodically revises their classification.[9]
[edit] Defining severity of pain
In addition to classifying the type of headache, the International Headache Society defines intensity of pain on a verbal 4-point scale:[10]
Number
Name
Annotations
0
no pain

1
mild pain
does not interfere with usual activities
2
moderate pain
inhibits, but does not wholly prevent usual activities
3
severe pain
prevents all activities
[edit] Migraine without aura
This is the most commonly seen form of migraine; patients who primarily suffer from migraine without aura may also have attacks of migraine with aura. The International Classification of Headache Disorders[9] defines this condition as follows:
Description: Recurrent headache disorder manifesting in attacks lasting 4–72 hours. Typical characteristics of the headache are unilateral location, pulsating quality, moderate or severe intensity, aggravation by routine physical activity and association with nausea and/or photophobia and phonophobia.Diagnostic criteria:A. At least five attacks fulfilling criteria B-DB. Headache attacks lasting 4-72 hours [when untreated]C. Headache has at least two of the following characteristics:
1. unilateral location
2. pulsating quality
3. moderate or severe pain intensity
4. aggravation by or causing avoidance of routine physical activity...
D. During the headache at least one of the following:
1. Nausea and/or vomiting
2. Photophobia and phonophobia
E. Not attributed to another disorder
– International Classification of Headache Disorders[9]
When these criteria are only partially met, the document specifies possible alternative diagnoses, including "probable migraine without aura" or "episodic tension-type headache".
[edit] Migraine with aura
This is the second most commonly seen form of migraine: patients who primarily suffer from migraine with aura may also have attacks of migraine without aura. According to the International Classification of Headache Disorders[9] it is a recurrent disorder manifesting in attacks of reversible focal neurological symptoms that usually develop gradually over 5–20 minutes and last for less than 60 minutes. Headache with the features of "migraine without aura" usually follows the aura symptoms. Less commonly, the aura may occur without a subsequent headache or the headache may be non-migrainous in type.
In order to diagnose migraine with aura, there must have been at least two attacks not attributable to another cause that fulfill the following criteria:
1. Aura consisting of at least one of the following, but no muscle weakness or paralysis:
o Fully reversible visual symptoms (e.g. flickering lights, spots, lines, loss of vision)
o Fully reversible sensory symptoms (e.g. pins and needles, numbness)
o Fully reversible dysphasia (speech disturbance)
2. Aura has at least two of the following characteristics:
o Visual symptoms affecting just one side of the field of vision and/or sensory symptoms affecting just one side of the body
o At least one aura symptom develops gradually over more than 5 minutes and/or different aura symptoms occur one after the other over more than 5 minutes
o Each symptom lasts from 5 to 60 minutes
Where these criteria are not fully met, a diagnosis of "probable migraine with aura" may be considered, although other neurological causes must also be considered. If the picture complies with the criteria but includes one-sided muscular weakness or paralysis, a diagnosis of "sporadic hemiplegic migraine" or "familial hemiplegic migraine" should be considered.
[edit] Basilar type migraine
Basilar type migraine (BTM), formerly known as basilar artery migraine (BAM) or basilar migraine (BM), is an uncommon type of complicated migraine with symptoms that result from brainstem dysfunction. Serious episodes of BTM can lead to stroke, coma, or even death. The use of triptans and other vasoconstrictors as abortive treatments in BTM is contraindicated. Abortive treatments for BTM often focus on vasodilation and restoration of normal blood flow to the vertebrobasilar territory and subsequent return of normal brainstem function.
[edit] Familial hemiplegic migraine
Main article: Familial hemiplegic migraine
Familial hemiplegic migraine 'FHM' is a type of migraine with a possible polygenetic component. These migraine attacks may last 4–72 hours[9] and are apparently caused by ion channel mutations, three types of which have been identified to date. Patients who experience this syndrome have relatively typical migraine headaches preceded and/or accompanied by reversible limb weakness on one side as well as visual, sensory or speech difficulties. A non-familial form exists as well, "sporadic hemiplegic migraine" (SHM). It is often difficult to make the diagnosis between basilar-type migraine and hemiplegic migraine. When making the differential diagnosis is difficult, the deciding symptom is often the motor weakness or unilateral paralysis which can occur in FHM or SHM. While basilar-type migraine can present with tingling or numbness, true motor weakness and/or paralysis occur only in hemiplegic migraine.
[edit] Abdominal migraine
According to the International Classification of Headache Disorders[9], abdominal migraine is a recurrent disorder of unknown origin which occurs mainly in children. It is characterised by episodes of moderate to severe central abdominal pain lasting 1–72 hours. There is usually associated nausea and vomiting but the child is entirely well between attacks.
In order to diagnose abdominal migraine, there must be at least five attacks, not attributable to another cause, fulfilling the following criteria:
1. Attacks lasting 1–72 hours when untreated
2. Pain must have ALL of the following characteristics:
o Location in the midline, around the umbilicus or poorly localised
o Dull or 'just sore' quality
o Moderate or severe intensity
3. During an attack there must be at least two of the following:
o Loss of appetite
o Nausea
o Vomiting
o Pallor
Most children with abdominal migraine will develop migraine headache later in life and the two may co-exist during adolescence.
[edit] Acephalgic migraine
Acephalgic migraine is a neurological syndrome. It is a variant of migraine in which the patient may experience aura symptoms such as scintillating scotoma, nausea, photophobia, hemiparesis and other migraine symptoms but does not experience headache. Acephalgic migraine is also referred to as amigrainous migraine, ocular migraine, or optical migraine.
Sufferers of acephalgic migraine are more likely than the general population to develop classical migraine with headache.
The prevention and treatment of acephalgic migraine is broadly the same as for classical migraine. However, because of the absence of "headache", diagnosis of acephalgic migraine is apt to be significantly delayed and the risk of misdiagnosis significantly increased.
Visual snow might be a form of acephalgic migraine.
If symptoms are primarily visual, it may be necessary to consult an ophthalmologist to rule out potential eye disease before considering this diagnosis.
[edit] Menstrual migraine
Menstrual migraine is distinct from other migraines. Approximately 21 million women in the US suffer from migraines,[11] and about 60% of them suffer from menstrual migraines.[12]
There are two types of menstrual migraine – Menstrually Related Migraine (MRM) and Pure Menstrual Migraine (PMM)
· MRM is a headache of moderate-to-severe pain intensity that happens around the time of a woman’s period and at other times of the month as well.
· PMM is similar in every respect but only occurs around the time of a woman’s period.[13]
The exact causes of menstrual migraine are uncertain but evidence suggest there may be a link between menstruation and migraine due to the drop in estrogen levels that normally occurs right before the period starts.[14]
Menstrual migraine has been reported to be more likely to occur during a five-day window, from two days before to two days after menstruation.[15]
When compared with migraines that occur at other times of the month, menstrual migraines have been reported to
Last longer—up to 72 hours[16]
Be more severe[15][17]
Occur more often with nausea and vomiting[12]
Be more difficult to treat—occur more frequently[18]
[edit] Signs and symptoms
The signs and symptoms of migraine vary among patients. Therefore, what a patient experiences before, during and after an attack cannot be defined exactly. The four phases of a migraine attack listed below are common but not necessarily experienced by all migraine sufferers. Additionally, the phases experienced and the symptoms experienced during them can vary from one migraine attack to another in the same migraineur:
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.
[edit] Prodrome phase
Prodromal symptoms occur in 40–60% of migraineurs (migraine sufferers). This phase may consist of altered mood, irritability, depression or euphoria, fatigue, yawning, excessive sleepiness, craving for certain food (e.g. chocolate), stiff muscles (especially in the neck), constipation or diarrhea, increased urination, and other visceral symptoms.[19] These symptoms usually precede the headache phase of the migraine attack by several hours or days, and experience teaches the patient or observant family how to detect that a migraine attack is near.
[edit] Aura phase
For the 20–30%[20][21] of individuals who suffer migraine with aura, this aura comprises focal neurological phenomena that precede or accompany the attack. They appear gradually over 5 to 20 minutes and generally last fewer than 60 minutes. The headache phase of the migraine attack usually begins within 60 minutes of the end of the aura phase, but it is sometimes delayed up to several hours, and it can be missing entirely. Symptoms of migraine aura can be visual, sensory, or motor in nature.[22]
Visual aura is the most common of the neurological events. There is a disturbance of vision consisting usually of unformed flashes of white and/or black or rarely of multicolored lights (photopsia) or forma­tions of dazzling zigzag lines (scintillating scotoma; often arranged like the battlements of a castle, hence the alternative terms "fortification spectra" or "teichopsia"). Some patients complain of blurred or shimmering or cloudy vision, as though they were look­ing through thick or smoked glass, or, in some cases, tunnel vision and hemianopsia. The somatosensory aura of migraine consists of digitolingual or cheiro-oral paresthesias, a feeling of pins-and-needles experienced in the hand and arm as well as in the nose-mouth area on the same side. Paresthesia migrate up the arm and then extend to involve the face, lips and tongue.
Other symptoms of the aura phase can include auditory or olfactory hallucinations, temporary dysphasia, vertigo, tingling or numbness of the face and extremities, and hypersensitivity to touch.
[edit] Pain phase
The typical migraine headache is unilateral, throbbing, moderate to severe and can be aggravated by physical activity. Not all of these features are necessary. The pain may be bilateral at the onset or start on one side and become generalized, and usually alternates sides from one attack to the next. The onset is usually gradual. The pain peaks and then subsides, and usually lasts between 4 and 72 hours in adults and 1 and 48 hours in children. The frequency of attacks is extremely variable, from a few in a lifetime to several times a week, and the average migraineur experiences from one to three headaches a month. The head pain varies greatly in intensity.
The pain of migraine is invariably accompanied by other features. Nausea occurs in almost 90 percent of patients, while vomiting occurs in about one third of patients. Many patients experience sensory hyperexcitability manifested by photophobia, phonophobia, osmophobia and seek a dark and quiet room. Blurred vision, nasal stuffiness, diarrhea, polyuria, pallor or sweating may be noted during the headache phase. There may be localized edema of the scalp or face, scalp tenderness, prominence of a vein or artery in the temple, or stiffness and tenderness of the neck. Impairment of concentration and mood are common. Lightheadedness, rather than true vertigo and a feeling of faintness may occur. The extremities tend to be cold and moist.
[edit] Postdrome phase
The patient may feel tired, have head pain, cognitive difficulties, "hungover", gastrointestinal symptoms, mood changes and weakness.[23] Some people feel unusually refreshed or euphoric after an attack, whereas others note depression and malaise. Often, some of the minor headache phase symptoms may continue, such as loss of appetite, photophobia, and lightheadedness. For some patients, a 5 to 6 hour nap may reduce the pain, but slight headaches may still occur when standing or sitting quickly. Normally these symptoms go away after a good night's rest.
[edit] Diagnosis
Migraines are underdiagnosed[24] and misdiagnosed.[25] The diagnosis of migraine without aura, according to the International Headache Society, can be made according to the following criteria, the "5, 4, 3, 2, 1 criteria":
5 or more attacks
4 hours to 3 days in duration
2 or more of - unilateral location, pulsating quality, moderate to severe pain, aggravation by or avoidance of routine physical activity
1 or more accompanying symptoms - nausea and/or vomiting, photophobia, phonophobia
For migraine with aura, only two attacks are required to justify the diagnosis.
The mnemonic POUNDing (Pulsating, duration of 4–72 hOurs, Unilateral, Nausea, Disabling) can help diagnose migraine. If 4 of the 5 criteria are met, then the positive likelihood ratio for diagnosing migraine is 24.[26]
The presence of either disability, nausea or sensitivity, can diagnose migraine with:[27]
sensitivity of 81%
specificity of 75%
Migraine should be differentiated from other causes of headaches such as cluster headaches. These are extremely painful, unilateral headaches of a piercing quality. The duration of the common attack is 15 minutes to three hours. Onset of an attack is rapid, and most often without the preliminary signs that are characteristic of a migraine.
[edit] Pathophysiology
Migraines were once thought to be initiated exclusively by problems with blood vessels. The vascular theory of migraines is now considered secondary to brain dysfunction[28] and claimed to have been discredited by others.[29]
The effects of migraine may persist for some days after the main headache has ended. Many sufferers 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.
Migraine headaches can be a symptom of hypothyroidism.[citation needed]
[edit] Depolarization theory
A phenomenon known as cortical spreading depression can cause migraines.[30] In cortical spreading depression, neurological activity is depressed over an area of the cortex of the brain. This situation results in the release of inflammatory mediators leading to irritation of cranial nerve roots, most particularly the trigeminal nerve, which conveys the sensory information for the face and much of the head.
This view is supported by neuroimaging techniques, which appear to show that migraine is primarily a disorder of the brain (neurological), not of the blood vessels (vascular). A spreading depolarization (electrical change) may begin 24 hours before the attack, with onset of the headache occurring around the time when the largest area of the brain is depolarized. A French study in 2007, using the Positron Emission Tomography (PET) technique identified the hypothalamus as being critically involved in the early stages.[31]
[edit] Vascular theory
Migraines can begin when blood vessels in the brain contract and expand inappropriately. This may start in the occipital lobe, in the back of the brain, as arteries spasm. The reduced flow of blood from the occipital lobe triggers the aura that some individuals who have migraines experience because the visual cortex is in the occipital area.[28]
When the constriction stops and the blood vessels dilate, they become too wide. The once solid walls of the blood vessels become permeable and some fluid leaks out. This leakage is recognized by pain receptors in the blood vessels of surrounding tissue. In response, the body supplies the area with chemicals which cause inflammation. With each heart beat, blood passes through this sensitive area causing a throb of pain.[28]
The vascular theory of migraines is now seen as secondary to brain dysfunction.[28]
[edit] Serotonin theory
Serotonin is a type of neurotransmitter, or "communication chemical" which passes messages between nerve cells. It helps to control mood, pain sensation, sexual behaviour, sleep, as well as dilation and constriction of the blood vessels among other things. Serotonin levels in the brain may lead to a process of constriction and dilation of the blood vessels which trigger a migraine.[28] Triptans activate serotonin receptors to stop a migraine attack.[28]
[edit] Neural theory
When certain nerves or an area in the brain stem become irritated, a migraine begins. In response to the irritation, the body releases chemicals which cause inflammation of the blood vessels. These chemicals cause further irritation of the nerves and blood vessels and results in pain. Substance P is one of the substances released with first irritation. Pain then increases because substance P aids in sending pain signals to the brain.[28]
[edit] Unifying theory
Both vascular and neural influences cause migraines.
1. stress triggers changes in the brain
2. these changes cause serotonin to be released
3. blood vessels constrict
4. chemicals including substance P irritate nerves and blood vessels causing pain[28]
[edit] Triggers
A migraine trigger is any factor that, on exposure or withdrawal, leads to the development of an acute migraine headache. Triggers may be categorized as behavioral, environmental, infectious, dietary, chemical, or hormonal. In the medical literature, these factors are known as 'precipitants.'
The MedlinePlus Medical Encyclopedia, for example, offers the following list of migraine triggers:
Migraine attacks may be triggered by:
Allergic reactions
Bright lights, loud noises, and certain odors or perfumes
Physical or emotional stress
Changes in sleep patterns
Smoking or exposure to smoke
Skipping meals
Alcohol
Menstrual cycle fluctuations, birth control pills, hormone fluctuations during the menopause transition
Tension headaches
Foods containing tyramine (red wine, aged cheese, smoked fish, chicken livers, figs, and some beans), monosodium glutamate (MSG) or nitrates (like bacon, hot dogs, and salami)
Other foods such as chocolate, nuts, peanut butter, avocado, banana, citrus, onions, dairy products, and fermented or pickled foods.
—MedlinePlus medical encyclopedia[46]
Sometimes the migraine occurs with no apparent "cause". The trigger theory supposes that exposure to various environmental factors precipitates, or triggers, individual migraine episodes. Migraine patients have long been advised to try to identify personal headache triggers by looking for associations between their headaches and various suspected trigger factors and keeping a "headache diary" recording migraine incidents and diet to look for correlations in order to avoid trigger foods. It must be mentioned, that some trigger factors are quantitative in nature, i.e., a small block of dark chocolate may not cause a migraine, but half a slab of dark chocolate almost definitely will, in a susceptible person. In addition, being exposed to more than one trigger factor simultaneously will more likely cause a migraine, than a single trigger factor in isolation, e.g., drinking and eating various known dietary trigger factors on a hot, humid day, when feeling stressed and having had little sleep will probably result in a migraine in a susceptible person, but consuming a single trigger factor on a cool day, after a good night's rest with minimal environmental stress may mean that the sufferer will not develop a migraine after all. Migraines can be complex to avoid, but keeping an accurate migraine diary and making suitable lifestyle changes can have a very positive effect on the sufferer's quality of life. Some trigger factors are virtually impossible to avoid, e.g. the weather or emotions, but by limiting the avoidable trigger factors, the unavoidable ones may have less of an impact on the sufferer. [47]
[edit] Food
A 2005 literature review found that the available information about dietary trigger factors relies mostly on the subjective assessments of patients.[48] Some suspected dietary trigger factors appear to genuinely promote or precipitate migraine episodes, but many other suspected dietary triggers have never been demonstrated to trigger migraines. The review authors found that alcohol, caffeine withdrawal, and missing meals are the most important dietary migraine precipitants, that dehydration deserved more attention, and that some patients report sensitivity to red wine. Little or no evidence associated notorious suspected triggers like chocolate, cheese, histamine, tyramine, nitrates, or nitrites with migraines. The artificial sweetener aspartame has not been shown to trigger headache, but in a large and definitive study monosodium glutamate (MSG) in large doses (2.5 grams) was associated with adverse symptoms including headache more often than was placebo. The review authors also note that while general dietary restriction has not been demonstrated to be an effective migraine therapy, it is beneficial for the individual to avoid what has been a definite cause of the migraine.
The National Headache Foundation has a specific list of triggers based on the tyramine theory, detailing allowed, with caution and avoid triggers.[49]
[edit] Weather
Several studies have found some migraines are triggered by changes in weather. One study noted 62% of the subjects thought weather was a factor but only 51% were sensitive to weather changes.[50] Among those whose migraines did occur during a change in weather, the subjects often picked a weather change other than the actual weather data recorded. Most likely to trigger a migraine were, in order:
1. Temperature mixed with humidity. High humidity plus high or low temperature was the biggest cause.
2. Significant changes in weather
3. Changes in barometric pressure
Another study examined the effects of warm chinook winds on migraines, with many patients reporting increased incidence of migraines immediately before and/or during the chinook winds. The number of people reporting migrainous episodes during the chinook winds was higher on high-wind chinook days. The probable cause was thought to be an increase in positive ions in the air.[51]
[edit] Other
One study found that for some migraineurs in India, washing hair in a bath was a migraine trigger. The triggering effect also had to do with how the hair was later dried.[52]

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