Thursday, 17 April 2014

Migraines

Pathophysiology


I think this picture from the amazing Calgary guide summarises everything very well.

Basically, something starts it off - we don't know why. Everything gets sensitised, and the patient has lots of pain. The pain fibres in the walls of intercerebral blood vessels are part of the trigemial nerve, which also supplies sensation to the face. This is why referred pain is common.

Epidemiology and Triggers
Migraine is three times more prevalent in women (about 18% of the population) than in men (about 6%).

Food includes MSG, tyramine - containing foods and nitrate containing foods (and skipped meals!)
Menstruation is a migraine trigger in 10% of women with migraine. This is often overestimated by the patient: true menstrual migraine can be diagnosed only after examining a few months of the headache and menstrual diary. The OCP may help, but the helpful effect is lost during the pill free week.

There is an increased risk of fatal ischaemic stroke in people with migraine with aura, increased in people using combined hormonal contraception.morrhagic stroke.

Clinical Features
To officially diagnose migraines, the following criteria must be met:
The headache should have two or more of the following characteristics:
    Unilateral location
    Pulsating quality
    Moderate to severe pain intensity
    Aggravated by or causing avoidance of routine physical activity.

The headache should be accompanied by one or more of:
    Nausea
    Vomiting
    Photophobia
    Phonophobia.
The headache should not be attributable to another disorder and there should be no red flags (abnormal neurology, systemic symptoms such as fevers, chills, and weight loss, rapid increase in headache frequency, orthostatic worsening of symptoms, exertional worsening of symptoms, new onset, thunderclap headaches (very severe headache that reaches maximum intensity in <1 min), with existing risk factors for a secondary headache (such as cancer or hypercoagulable state) or overuse of headache abortive drugs.
This is nicely summarised with this mneumonic:


When does a "normal headache" become a migraine? You can have migraine with or without aura. Most of my headaches could be officially diagnosed as migraine. I call them a migraine if I HAVE to go to bed, and a headache if I struggle on with pain killers. But officially... Officially migraine causes bed rest or severe impairment in more than half of people.

Other useful pointers to a diagnosis of migraine include:
    family history of headache/ migraine
    motion sickness or cyclical vomiting as a child
    delayed headache following alcohol, or "unfair" tendency to hangovers
    typical migraine triggers, for example sleep disturbance, missing meals, relaxation, pre- or perimenstrual timing, cheese, wine, chocolate, citrus, etc

Typical aura symptoms include visual, sensory and speech symptoms. Visual symptoms are most common, and include flickering lights, spots or lines, or loss of vision (blind spots or scotoma). An aura typically lasts for <60 minutes, and usually precedes or sometimes accompanies the headache. Around a third of migraine sufferers report the experience of aura symptoms. Only just over half of migraine sufferers who experience aura experience it with every attack. Most aura symptoms last between 30 minutes and one hour and occur before the onset of pain.

Chronic migraine is properly defined as >15 days of headache per month, with >eight days being migraine, for at least three months. The definition excludes people who overuse medication

Treatment
Consider rectal treatment if IV inappropriate or for home. Do NOT  use opiates!
Naproxen: NNT of 11.
Aspirin: 1000mg
Ibuprofen
is more effective than paracetamol at pain relief for migraine attacks in children

Chlorpromazine: IV + NaCl
Prochlorperazine: 10mg IV + NaCl is better than metoclopramide
Metoclopramide: Conflicting evidence
Haloperidol: 2.5 mg of haloperidol as a substitute (the literature on this is scarce, and some of it is old).

Triptans: More effective if taken in the prodromal window. They block the stimulation of the trigeminal ganglion and preventing the sensation of pain. The triptans are selective 5-hydroxytryptamine (5HT) receptor agonists, with high affinity for the 5HT1B and 5HT1D receptors. 5HT1B receptors are on smooth muscle cells of blood vessels and cause vasoconstriction when stimulated.
Around 1-7% of participants in clinical trials (without cardiovascular disease) experience “triptan sensations”—a burning, tingling, or tightness in the face, neck, limbs, or chest—which is not associated with electrocardiographic or enzymatic evidence of myocardial ischaemia.
Triptans are not recommended for use in pregnancy or in the presence of coronary heart disease, as there are also receptors in the coronary arteries.

Propofol:
20-30mg every 3 - 5minutes reduces pain quickly and effectively. I don't think it'd ever be in my top million treatments!
Dexamethasone: 26% relative reduction in headache recurrence (number needed to treat=9) in 72 hours.

Prophylaxis
Pharmacological prophylaxis is recommended in those who:
-    Have frequent, high impact migraine attacks (>4 per month)
-    Are not treated satisfactorily with appropriate acute medications
-    Have concomitant conditions that do not allow the use of acute medications (for example, a migraine variant)
-    Are overusing acute medications, or have chronic primary headache, or both
-    Advice on behavioural and physical therapies, including acupuncture, relaxation, biofeedback, stress reduction, cervical manipulation, massage, exercise and avoiding migraine triggers. Change in sleeping times at weekends and irregular shift work may usefully be avoided, as is the abrupt let-down from stress.
-    Feverfew, magnesium, and vitamin B2

Propanolol, topiramate and acupuncture should be considered.



References:
http://jnnp.bmj.com/content/early/2012/07/23/jnnp-2012-302487
http://circ.ahajournals.org/content/118/14/1405.full
http://emupdates.com/2009/11/23/migraine-criteria-for-diagnosis/
http://socmob.org/2013/11/propofol-migraine-part-2/
http://bestbets.org/bets/bet.php?id=545
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http://bestbets.org/bets/bet.php?id=2074http://bestbets.org/bets/bet.php?id=2458
http://academiclifeinem.com/on-the-horizon-propofol-for-migraines/
http://annals.org/article.aspx?articleid=715803http://empharmd.blogspot.co.uk/2013/05/milking-it-propofol-for-migraine.html
http://jnnp.bmj.com/content/72/suppl_2/ii10.full
http://learning.bmj.com/learning/module-intro/preventive-%CE%B2-blocker-migraine-optimised-acute-migraine.html?moduleId=10017044&searchTerm=%E2%80%9Cmigraine%E2%80%9D&page=1&locale=en_GB
http://www.bmj.com/content/348/bmj.g1416.pdf%2Bhtml
http://www.bmj.com/content/347/bmj.f6952.pdf%2Bhtml
http://bestbets.org/bets/bet.php?id=1416
http://www.enlightenme.org/node/2331
http://learning.bmj.com/learning/module-intro/migraine-diagnosis-prevention.html?moduleId=5003207&searchTerm=%E2%80%9Cmigraine%E2%80%9D&page=1&locale=en_GB
http://learning.bmj.com/learning/module-intro/migraine-patient-experience-pathology-therapies.html?moduleId=10021852&searchTerm=%E2%80%9Cmigraine%E2%80%9D&page=1&locale=en_GB
http://learning.bmj.com/learning/module-intro/migraine-haemorrhagic-stroke-women.html?moduleId=10016760&searchTerm=%E2%80%9Cmigraine%E2%80%9D&page=1&locale=en_GB
http://calgaryguide.ucalgary.ca/slide.aspx?slide=Migraines%20and%20Auras%20Pathogenesis%20and%20Clinical%20Findings.jpg

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