Migraine

From Ganfyd

A syndrome characterised by episodes of headaches and other unpleasant symptoms thought to be caused autonomic dysfunction. It is common with a female preponderance and an estimated prevalence of 10%.

Pathogenesis

The precise trigger factors remain unclear and may vary between individuals, but the central neurobiological event appears to be a wave cortical spreading depression that moves through the cortex at a rate of about 3mm a minute. If the CSD starts in the occipal cortex, a visual aura results. At the front of the spreading wave of CSD is an abnormally high concentration of extracellular potassium. Restoration of potassium and therefore membrane potential is achieved in the following minutes, but this process is a metabolically-demanding task resulting in focal transient hypoxia with associated vasoconstriction that further contributes to the relative ischaemia. The CSD therefore leaves a trail of relative neural inactivity in its wake. Furthermore, the CSD disrupts the blood-brain barrier with resulting leakage of plasma proteins factors that activate pain receptors in the trigeminal nucleus.

A small subset of migraines in the form of familial hemiplegic migraine are known to be inherited and are due to a genetic mutations in various ion channels, about half in a voltage-gated calcium channel. This is thought to lower the threshold for the initiation of CSD.

Terminology

Migraines are classified into two types:

1. Migraine with aura ~20% (previously called classic migraine)
2. Migraine without aura ~80% (previously called common migraine)

Features

• prodrome
  • yawning
  • depression
  • hyperexcitability/euphoria
  • increased sense of smell
• aura/visual disturbance
• headache
• nausea and vomiting
• malaise
• sensitivity to light (photophobia)

International Headache Society Criteria for Migraine without Aura

A. At least 5 attacks fulfilling criteria B-D
B. Headache attacks lasting 4-72 h (untreated or unsuccessfully treated)
C. Headache has >= 2 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 (eg, walking, climbing stairs)

D. During headache >= 1 of the following:

1. nausea and/or vomiting
2. photophobia and phonophobia

E. Not attributed to another disorder

International Headache Society Criteria for Migraine with Aura

A. At least 2 attacks fulfilling criteria B–D
B. Aura consisting of one of the following, but no motor weakness:

1. fully reversible visual symptoms including positive and/or negative features
2. fully reversible sensory symptoms including positive and/or negative features
3. fully reversible dysphasic speech disturbance

C. At least two of the following:

1. homonymous visual symptoms and/or unilateral sensory symptoms
2. at least one aura symptom develops gradually over 5 min and/or different aura symptoms occur in succession over 5 min
3. each symptom lasts 5 and 60 min

D. Headache fulfilling criteria B-D for 1.1 Migraine without aura begins during the aura or follows aura within 60 min
E. Not attributed to another disorder

Investigation

A full neurological examination should be performed to exclude focal signs. Migraine is otherwise a clinical diagnosis based on criteria specified by the International Headache Society. Investigation is only required when the diagnosis of migraine is equivocal and other diagnoses need to be excluded.

Drug prophylaxis

The PRODIGY guideline on migrainehas a section on drug prophylaxis. It lists a number of drugs which it states are "relatively safe and effective, and are licensed for the prevention of migraine or are commonly used for this purpose.":

• Beta-blockers are first-line drugs in the absence of contraindications
• Amitriptyline is a first-line drug
• Anti-convulsants have been extensively used, and studied, as second line drugs
  • Sodium valproate at 300mg bd increasing to 1200mg/day or even 1000mg bd. (Best start on 100mg bd and raise)
  • Topiramate is another anti-convulsant which may acquire a licence for this use.
  • Gabapentin
• A botulinum toxin has been licensed in the EU for the prophylaxis of headaches in adults with chronic migraine (headaches on at least 15 days per month of which at least 8 days are with migraine). It may not be available on the NHS in the UK.

The same guideline also reports on drugs which should not be used for prophylaxis.

Drug therapy for acute attacks

Clinial Evidence has a chapter on migraine headaches which includes a section on treating acute migraine. It reports:

Beneficial

• Eletriptan
• Ibuprofen
• Naratriptan
• Rizatriptan
• Salicylates
• Sumatriptan
• Zolmitriptan

Likely to be beneficial

• Diclofenac
• Ergotamine
• Naproxen
• Tolfenamic acid

The PRODIGY guideline on migrainealso has an extensive section on management of acute attacks.

External Links

• International Headache Society
• Br. Assoc. for Study of headache (BASH) Migraine guideline (PDF)
• The collection on Migraine from the Bandolier is extremely good.