| Migraine | |
|---|---|
| Classification and external resources | |
The pain of a migraine headache can be debilitating. |
|
| ICD-10 | G43 |
| ICD-9 | 346 |
| OMIM | 157300 |
| DiseasesDB | 8207 (Migraine) 31876 (Basilar) 4693 (FHM) |
| MedlinePlus | 000709 |
| eMedicine | neuro/218 neuro/517 emerg/230 neuro/529 |
| MeSH | D008881 |
Migraine is a chronic neurological disorder characterized by moderate to severe headaches, and nausea. It is about three times more common in women than in men.[1] The word derives from the Greek ἡμικρανία (hemikrania), "pain on one side of the head",[2] from ἡμι- (hemi-), "half", and κρανίον (kranion), "skull".[3]
The typical migraine headache is unilateral (affecting one half of the head) and pulsating in nature and lasting from two to 72 hours; symptoms include nausea, vomiting, photophobia (increased sensitivity to light) and phonophobia (increased sensitivity to sound); the symptoms are generally aggravated by routine activity.[4][5] Approximately one-third of people who suffer from migraine headaches perceive an aura—transient visual, sensory, language, or motor disturbances signaling the migraine will soon occur.[6][7]
Initial treatment is with analgesics for the headache, an antiemetic for the nausea, and the avoidance of triggers. The cause of migraine headache is unknown; the most supported theory is that it is related to hyperexcitability of the cerebral cortex and/or abnormal control of pain neurons in the trigeminal nucleus of the brainstem.[8]
Studies of twins indicate a 60- to 65-percent genetic influence upon their propensity to develop migraine headaches.[9][10] Moreover, fluctuating hormone levels indicate a migraine relation: 75 percent of adult patients are women, although migraine affects approximately equal numbers of prepubescent boys and girls. Propensity to migraine headache sometimes disappears during pregnancy, but in some women, migraines may become more frequent.[11]
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The International Headache Society (IHS) offers guidelines for the classification and diagnosis of migraine headaches, in a document called "The International Classification of Headache Disorders, 2nd edition" (ICHD-2).[4] These guidelines constitute arbitrary definitions, and are not supported by scientific data.[4]
According to ICHD-2, there are seven subclasses of migraines (some of which include further subdivisions):
Migraines typically present with recurrent severe headache associated with autonomic symptoms.[14] An aura only occurs in a small percentage of people.[14] The severity of the pain, duration of the headache, and frequency of attacks is variable.[14] A migraine lasting 72 hours is termed status migrainosus and can be treated with intravenous prochlorperazine. The four possible phases to a migraine attack[4] are listed below — not all the phases are necessarily experienced. Additionally, the phases experienced and the symptoms experienced during them can vary from one migraine attack to another in the same person:
Prodromal symptoms occur in 40–60% of those with migraines. 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), dizziness, hot ears, constipation or diarrhea, increased or decreased urination, and other visceral symptoms.[15] 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 a migraine attack is near.
For the 20–30%[16][17] of migraine sufferers who experience migraine with aura, this aura comprises focal neurological phenomena that precede or accompany the attack. They appear gradually over five 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 (see silent migraine). The pain may also begin before the aura has completely subsided. Symptoms of migraine aura can be sensory or motor in nature.[18]
Visual aura is the most common of the neurological events, and can occur without any headache. There is a disturbance of vision consisting often 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"[19]). Some patients complain of blurred or shimmering or cloudy vision, as though they were looking at an area above a heated surface, looking through thick or smoked glass, or, in some cases, tunnel vision and hemianopsia.
The somatosensory aura of migraine may consist 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. The paresthesia may migrate up the arm and then extend to involve the face, lips and tongue.
Other symptoms of the aura phase can include auditory, gustatory or olfactory hallucinations, temporary dysphasia, vertigo, tingling or numbness of the face and extremities, and hypersensitivity to touch.
Oliver Sacks's book Migraine describes "migrainous deliria" as a result of such intense migraine aura that it is indistinguishable from "free-wheeling states of hallucinosis, illusion, or dreaming."
The typical migraine headache is unilateral, throbbing, and moderate to severe, and can be aggravated by physical activity.[4] Not all these features are necessary. The pain may be bilateral at the onset or start on one side and become generalized, and may occur primarily on one side or alternate sides from one attack to the next. The onset is usually gradual. The pain peaks and then subsides and usually lasts two to 72 hours in adults and one to 48 hours in children. The frequency of attacks is extremely variable, from a few in a lifetime to several a week, and the average sufferer experiences one to three headaches a month. The head pain varies greatly in intensity, and can be very severe.
The pain of migraine is invariably accompanied by other features. Nausea occurs in almost 90 percent of patients, and vomiting occurs in about one third of patients. Many patients experience sensory hyperexcitability manifested by photophobia, phonophobia, and osmophobia and seek a dark and quiet room. Blurred vision, delirium, nasal stuffiness, diarrhea, tinnitus, 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. The extremities tend to feel cold and moist. Vertigo may be experienced; a variation of the typical migraine, called vestibular migraine, has also been described. Lightheadedness, rather than true vertigo, and a feeling of faintness may occur. Acupuncture has been studied as a treatment for migraine headache for more than 20 years. While not all studies have shown benefit with acupuncture, researchers do agree that acupuncture appears safe and that it may be effective for some people. Results from a study published in 2003 suggest that receiving an acupuncture treatment when migraine symptoms first begin is as effective as taking the drug Imitrex; as symptoms continue, however, the medication works better than acupuncture.
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. The patient may feel tired or "hungover" and have head pain, cognitive difficulties, gastrointestinal symptoms, mood changes, and weakness.[20] According to one summary, "Some people feel unusually refreshed or euphoric after an attack, whereas others note depression and malaise."[21]
A temporary Horner's syndrome (ptosis-drooping lid, miosis-smaller pupil) may occur during a migraine attack and disappear afterwards.[22]
The underlying cause of migraines is unknown.[23] There are, however, many biological events that have been clinically associated with migraine.
Migraines may be induced by triggers, with some reporting it as an influence in a minority of cases[14] and others the majority.[24] Many things have been labeled as triggers, however the strength and significance of these relationships are uncertain.[24][25] Common triggers quoted are stress, hunger, and fatigue (these equally contribute to tension headaches).[24] A 2003 review concluded there was no scientific evidence for an effect of tyramine on migraine.[26] A 2005 literature review on dietary triggers found the available scientific studies, mostly relying on subjective assessments, were not rigorous enough to prove or disprove any particular triggers.[27] This is in line with other reviews. A 2009 review of potential triggers in the indoor and outdoor environment concluded the overall evidence was of poor quality, but nevertheless suggested migraineurs take some preventative measures related to indoor air quality and lighting.[28] While monosodium glutamate (MSG) is frequently reported as a dietary trigger[29] evidence does not consistently support this.[30] Migraines are more likely to occur around menstruation.[31] Other hormonal influences, such as menarche, oral contraceptive use, pregnancy, perimenopause, and menopause, also play a role.[32]
The phenomenon known as cortical spreading depression, which is associated with the aura of migraine,[33] has been theorized as a possible cause of migraines. In cortical spreading depression, neurological activity is initially activated, then depressed over an area of the cerebral cortex. This situation has been suggested to result 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 theory is, however, speculative, without any supporting evidence, and there are indeed cogent arguments against it. First, only about one third of migraineurs experience an aura, and those who do not experience aura do not have cortical spreading depression. Second, many migraineurs have a prodrome (see above), which occurs up to three days before the aura.[15]
Studies have shown the aura coincides with constriction of blood vessels in the brain. 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 some individuals who have migraines experience, because the visual cortex is in the occipital area.[34]
When the constriction of blood vessels in the brain stops and the aura subsides, the blood vessels of the scalp dilate.[35] The walls of these 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.[34]
Although cerebral vasodilation can trigger migraine attacks, blood vessel diameters return to normal more than an hour before the migraine headaches occur.[36]
Serotonin is a type of neurotransmitter, or "communication chemical" which passes messages between nerve cells. It helps to control mood, pain sensation, sexual behaviour and sleep, as well as dilation and constriction of the blood vessels, among other things. Low serotonin levels in the brain may lead to a process of constriction and dilation of the blood vessels which trigger a migraine.[34] Serotonergic agonists, such as triptans,[34] LSD or psilocin, activate serotonin receptors to stop a migraine attack.
A melanopsin-based receptor has been linked to the association between light sensitivity and migraine pain,[37] but this is currently speculation.
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.[34]
Both vascular and neural influences cause migraines.
Migraine is a neurovascular disorder.[14] Although migraine is thought by some to be a neurological disease, in the absence of scientific evidence, this remains a hypothesis.
Migraines were once thought to be initiated exclusively by problems with blood vessels, but the vascular changes of migraines are now considered by some to be secondary to brain dysfunction,[34] although this concept has not been supported by the evidence. This was eloquently summed up by Dodick, who wrote, "There is no disputing the role of the central nervous system in the susceptibility, modulation and expression of migraine headache and the associated affective, cognitive, sensory, and neurological symptoms and signs. However, to presume that migraine is always generated from within the central nervous system, based on the available evidence, is naïve at best and unscientific at worst.The emerging evidence would suggest that just as alterations in neuronal activity can lead to downstream effects on the cerebral blood vessel, so too can changes within endothelial cells or vascular smooth muscle lead to downstream alterations in neuronal activity. Therefore, there are likely patients, and/or at least attacks in certain patients, where primarily vascular mechanisms predominate."[38] Some have even attempted to show that vascular changes are of no importance in migraine,[39][40] but this claim is unsubstantiated and has not been supported by scientific evidence. 'If we swing between vascular and neurogenic views of migraine, it is probably because both vascular and neurogenic mechanisms for migraine exist and are important'- J Edmeads[38]
Although the initiating factor of migraine remains unknown, copious, irrefutable evidence shows the pain of migraine (the third phase)[4] is, in some patients, related to painful dilatation of the terminal branches of the external carotid artery, and in particular its superficial temporal and occipital branches.[35][41][42][43][44][45] Dilatation of the arteries in the brain and dura mater previously was thought to be the origin of the vascular pain, but these vessels have been shown to not dilate during migraine.[46][47] Because these arteries are relatively superficial, it is easy to diagnose whether they are the source of the pain. If they are, then they are also accessible to a form of migraine surgery being promoted, largely to the efforts of Dr Elliot Shevel, a South African surgeon, who has reported excellent success using the procedure.[48]
Pericranial (jaw and neck) muscle tenderness is a common finding in migraine.[49][50][51] Muscle tenderness has been shown to be present in 100% of migraine attacks, making muscle tenderness the single most common finding in migraine.[49] Tender muscle trigger points can be at least part of the cause, and perpetuate most kinds of headaches.[52]
Migraines are underdiagnosed,[53] and often are misdiagnosed.[54] 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":[4]
The mnemonic POUNDing (Pulsating, duration of 4–72 hOurs, Unilateral, Nausea, Disabling) can help diagnose migraine. If four of the five criteria are met, then the positive likelihood ratio for diagnosing migraine is 24.[55]
The presence of either disability, nausea or sensitivity can diagnose migraine with:[56]
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 characteristic of a migraine.
Medical imaging of the head and neck may be used to rule out secondary causes of headaches.[14]
Preventive (also called prophylactic) treatment of migraines can be an important component of migraine management. Such treatments can take many forms, including taking preventive drugs, migraine surgery, taking nutritional supplements, lifestyle alterations, such as increased exercise, and avoidance of migraine triggers.
The goals of preventive therapy are to reduce the frequency, painfulness, and/or duration of migraines, and to increase the effectiveness of abortive therapy.[57] Another reason to pursue these goals is to avoid medication overuse headache (MOH), otherwise known as rebound headache. This is a common problem among migraineurs, and can result in chronic daily headache.[58][59]
Many of the preventive treatments are quite effective. Even with a placebo, one-quarter of patients find their migraine frequency is reduced by half or more, and actual treatments often far exceed this figure.[60]
Preventive migraine drugs are considered effective if they reduce the frequency or severity of migraine attacks by at least 50%.[61] The major problem with migraine preventive drugs, apart from their relative inefficacy, is that unpleasant side effects are common. So, preventive medication is limited to patients with frequent or severe headaches.[62]
Many medicines are available to prevent or reduce frequency, duration and severity of migraine attacks. They may also prevent complications of migraine. Beta blockers, such as Propranolol, atenolol, and metoprolol; calcium channel blockers, such as amlodipine, flunarizine and verapamil; the anticonvulsants sodium valproate, divalproex, gabapentin and topiramate; and tricyclic antidepressants are some of the commonly used drugs.
Tricyclic antidepressants have been found to be more effective than SSRIs.[63] Tricyclic antidepressants have been long established as efficacious prophylactic treatments.[61] These drugs, however, may give rise to undesirable side effects, such as insomnia, sedation or sexual dysfunction. There is no consistent evidence that SSRI antidepressants are effective for migraine prophylaxis. While amitryptiline (Elavil) is the only tricyclic to have received FDA approval for migraine treatment, other tricyclic antidepressants are believed to act similarly and are widely prescribed, often to find one with a profile of side effects that is acceptable to the patient.[61] In addition to tricyclics a, the antidepressant nefazodone may also be beneficial in the prophylaxis of migraines due to its antagonistic effects on the 5-HT2A[64] and 5-HT2C receptors[65][66] It has a more favorable side effect profile than amitriptyline, a tricyclic antidepressant commonly used for migraine prophylaxis. Antidepressants offer advantages for treating migraine patients with comorbid depression.[61] SSRIs are not approved by the FDA for treatment of migraines, but have been found to be effective by some practitioners.[61]
There is some evidence that low-dose asprin has benefit for reducing the occurrence of migraines in susceptible individuals.[67][68][69]
Migraine surgery is a field that shows a great deal of promise, particularly in those who suffer more frequent attacks, and in those who have not had an adequate response to prophylactic medications. Patients often still experience a poor quality of life despite an aggressive regimen of pharmacotherapy.[70] For these reasons, surgical solutions to migraines have been developed, which have excellent results.[71][72][73][74][75][76][77][78][79][80][81][82][83] A major advantage of migraine surgery is that, with the correct diagnostic techniques, a definite diagnosis can be made before the surgery is undertaken. Once a positive diagnosis has been made, the results of surgery are outstanding and provide permanent pain relief, as well as relief from the associated symptoms, such as nausea, vomiting, light sensitivity, and sound sensitivity. Surgical cauterization of the superficial blood vessels of the scalp (the terminal branches of the external carotid artery) is only carried out if it has been established with certainty that these vessels are indeed the source of pain. It is a safe and relatively atraumatic procedure which can be performed in a day facility.[71] The value of arterial sugery for migraine treatment is gaining recognition as a result of the efforts of a South African surgeon, Dr Elliot Shevel, who has produced a number of papers on the subject.
The removal of muscles or nerves in areas known as "trigger sites" provides good results, but only in patients who respond well to Botox injections in specific areas.[72]
There is also evidence that the correction of a congenital heart defect, patent foramen ovale (PFO), reduces migraine frequency and severity.[84] Recent studies have advised caution, though, in relation to PFO closure for migraines, as insufficient evidence exists to justify this dangerous procedure.[85][86]
Medical devices, such as biofeedback and neurostimulators, have some advantages in the migraine treatment, mainly when common antimigraine medication is contraindicated or in case of medication over use. Biofeedback helps patient to be conscious of some physiologic parameters to control them and try to relax. This method is considered to be efficient for migraine[87] and tension-type headache treatment.[88] A recent clinical trial has demonstrated that simple use of biofeedback as a relaxation technique has similar efficacy for migraine treatment to sophisticated sessions in clinics.[89] Neurostimulation used initially implantable neurostimulators similar to pacemakers for the treatment of intractable chronic migraines[90][91] with encouraging good results. But the needed surgery with implantable neurostimulators is limiting the indication to sever cases.[92] Recently, a new technique of external trigeminal (V1) or occipital nerve (CII) neurostimulation (Cefaly) could offer a larger use for migraine treatment or prevention.
A systematic review stated that chiropractic manipulation, physiotherapy, massage and relaxation might be as effective as propranolol or topiramate in the prevention of migraine headaches; however, the research had some problems with methodology.[93]
"The therapeutic potential of magnesium, coenzyme Q(10), riboflavin, and vitamin B(12) can be cautiously inferred from some published open clinical trials."[94] A review has concluded that "[c]urrent clinical data support the use of fever-few, butterbur, magnesium, and riboflavin in migraine prophylaxis."[95]
A migraine diary allows the assessment of headache characteristics, to differentiate between migraine and tension-type headache and to record the use and efficacy of acute medication. A diary also helps to analyse the relationship between migraine and menstruation.[96] Finally, the diary can help to identify trigger factors. A trigger may occur up to 24 hours prior to the onset of symptoms;[14] the majority of migraines, though, are not caused by identifiable triggers.[14]
There are three main aspects of treatment: trigger avoidance, acute symptomatic control, and pharmacological prevention.[14] Medications are more effective if used earlier in an attack.[14] The frequent use of medications may, however, result in medication overuse headache, in which the headaches become more severe and more frequent. These may occur with triptans, ergotamines, and analgesics, especially narcotic analgesics.[4]
A number of analgesics are effective for treating migraines including:
Triptans such as sumatriptan are effective for both pain and nausea in up to 75% of people.[14][104] The different forms available include oral, injection, nasal spray, and oral dissolving tablets.[14] Most side effects are mild, such as flushing; however, rare cases of myocardial ischemia have occurred.[14] They are not addictive, but may cause medication overuse headaches if used more than 10 days per month.[105]
Ergotamine[14] and dihydroergotamine are older medications still prescribed for migraines, the latter in nasal spray and injectable forms.[14] They were the primary drugs available to abort a migraine prior to the triptans, and are much less expensive than triptans.
A single dose of intravenous dexamethasone, when added to standard treatment of a migraine attack, is associated with a 26% decrease in headache recurrence in the following 72 hours.[106]
Antiemetics by mouth may help relieve symptoms of nausea and help prevent vomiting, which can diminish the effectiveness of orally taken analgesics. In addition, some antiemetics, such as metoclopramide, are prokinetics and help gastric emptying, which is often impaired during episodes of migraine. In the UK, three combination antiemetic and analgesic preparations are available: MigraMax (aspirin with metoclopramide), (paracetamol/codeine for analgesia, with buclizine as the antiemetic) and paracetamol/metoclopramide (Paramax in UK).[107] The earlier these drugs are taken in the attack, the better their effect.
The risk of stroke may be increased two- to three-fold in migraine sufferers. Young adult sufferers and women using hormonal contraception appear to be at particular risk.[108] The mechanism of any association is unclear, but chronic abnormalities of cerebral blood vessel tone may be involved. Women who experience auras have been found to have twice the risk of strokes and heart attacks over nonaura migraine sufferers and women who do not have migraines.[108][109] (Note: Women who experience auras and also take oral contraceptives have an even higher risk of stroke).[110] Migraine sufferers seem to be at risk for both thrombotic and hemorrhagic stroke as well as transient ischemic attacks.[111] Death from cardiovascular causes was higher in people with migraine with aura in a Women's Health Initiative study, but more research is needed to confirm this.[109][112]
Worldwide, migraines affect more than 10% of people.[23] In the United States, about 6% of men and 18% of women get a migraine in a given year, with a lifetime risk of about 18% and 43% respectively.[14] In Europe, migraines affect 12–28% of people at some point in their lives.[1] Based on the results of a number of studies, one-year prevalence of migraine ranges from 6–15% in adult men and from 14–35% in adult women.[1] These figures vary substantially with age: approximately 4–5% of children aged under 12 suffer from migraine, with little apparent difference between boys and girls.[113] A rapid growth in incidence amongst girls occurs after puberty,[114][115][116] which continues throughout early adult life.[117] By early middle age, around 25% of women experience a migraine at least once a year, compared with fewer than 10% of men.[1][118] After menopause, attacks in women tend to decline dramatically, so that in the over 70s, approximately equal numbers of males and females are sufferers, with prevalence returning to around 5%.[1][118]
At all ages, migraine without aura is more common than migraine with aura, with a ratio of between 1.5 and 2.0:1.[119][120] Incidence figures show the excess of migraine seen in women of reproductive age is mainly due to migraine without aura.[119] Thus, in prepubertal and postmenopausal populations, migraine with aura is somewhat more common than amongst 15–50 year olds.[117][121]
There is a strong relationship between age, sex and type of migraine.[122]
Studies in Asia and South America suggest the rates there are relatively low,[123][124] but they do not fall outside the range of values seen in European and North American studies.[1][118]
The incidence of migraine is related to the incidence of epilepsy in families, with migraine twice as prevalent in family members of epilepsy sufferers, and more common in epilepsy sufferers themselves.[125]
Trepanation, the deliberate and (usually) nonfatal drilling of holes into a skull, was practiced 9,000 years ago and earlier.[126] Some scholars have (controversially) speculated this drastic procedure might have been a migraine treatment, based on cave paintings[127] and on the fact that trepanation was a historical migraine treatment in 17th-century Europe.[126][128] An early written description consistent with migraines is contained in the Ebers papyrus, written around 1200 BC in ancient Egypt.[126]
In 400 BC, Hippocrates described the visual aura that can precede the migraine headache, and the relief which can occur through vomiting. Aretaeus of Cappadocia is credited as the "discoverer" of migraines because of his second-century description of the symptoms of a unilateral headache associated with vomiting, with headache-free intervals in between attacks.
Galenus of Pergamon used the term "hemicrania" (half-head), from which the word "migraine" was derived. He thought there was a connection between the stomach and the brain because of the nausea and vomiting that often accompany an attack. For relief of migraine, Andalusian-born physician Abulcasis, also known as Abu El Qasim, suggested application of a hot iron to the head or insertion of garlic into an incision made in the temple.
In the Middle Ages. migraine was recognized as a discrete medical disorder. Followers of Galenus explained migraine as being caused by aggressive yellow bile. Ebn Sina (Avicenna) described migraine in his textbook "El Qanoon fel teb" as "... small movements, drinking and eating, and sounds provoke the pain... the patient cannot tolerate the sound of speaking and light. He would like to rest in darkness alone." Abu Bakr Mohamed Ibn Zakariya Râzi noted the association of headache with different events in the lives of women, "...And such a headache may be observed after delivery and abortion or during menopause and dysmenorrhea."
In Bibliotheca Anatomica, Medic, Chirurgica, published in London in 1712, five major types of headaches are described, including the "Megrim", recognizable as classic migraine. The term "classic migraine" is no longer used, and has been replaced by the term "migraine with aura"[4] Graham and Wolff (1938) published their paper advocating ergotamine tartrate for relieving migraine. Later in the 20th century, Harold Wolff (1950) developed the experimental approach to the study of headache and elaborated the vascular theory of migraine, which has come under attack as the pendulum again swings to the neurogenic theory. Recently, there has been renewed interest in Wolff's vascular theory of migraine led by Elliot Shevel, a South African headache specialist, who has published a number of articles providing compelling evidence that Wolff was correct.[42][47][48][129]
Chronic migraine attacks are a significant source of both medical costs and lost productivity. It has been estimated to be the most costly neurological disorder in the European Community, costing more than €27 billion per year.[130]
Merck Corp new drug, Telcagepant, intended to relieve pain without causing vasoconstriction (narrowing of blood vessels) as current medications such as triptans do, was pulled from the market after clinical trials showed liver function abnormalities in some study subjects. ^ Merck & Co.: Memo to all US study locations involved in protocol MK0974-049
Recently, calcitonin gene related peptides (CGRPs) have been found to play a role in the pathogenesis of the pain associated with migraine, as triptans also decrease its release and action. CGRP receptor antagonists, such as olcegepant and telcagepant, are being investigated both in vitro and in clinical studies for the treatment of migraine.[131]
In 2010, scientists identified a genetic defect linked to migraines which could provide a target for new drug treatments.[132]
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