Lucan · Conditions

Migraine

Australian guidance: eTG Neurology — Headache + RACGP

1. Definition and epidemiology

Migraine is a primary headache disorder characterised by recurrent episodes of moderate to severe unilateral pulsating pain, typically lasting 4 to 72 hours, often accompanied by nausea, photophobia, or phonophobia. In Australia, migraine affects approximately 15% of the population, making it one of the most prevalent disabling neurological conditions; it is roughly three times more common in women than men following puberty, a disparity attributed to hormonal influences. The global burden is substantial, with migraine ranking among the leading causes of years lived with disability worldwide.

2. Pathophysiology

The pathophysiology of migraine involves a complex interplay between cortical, trigeminal, and vascular mechanisms (Robbins Ch 28). The leading model centres on cortical spreading depression (CSD): a wave of neuronal and glial depolarisation that propagates across the cortex at roughly 3 to 5 mm per minute, causing transient neurological symptoms that manifest clinically as the aura phase. CSD activates trigeminal nerve fibres innervating the meningeal vasculature, triggering release of vasoactive neuropeptides including calcitonin gene-related peptide (CGRP), substance P, and neurokinin A. These mediators produce sterile neurogenic inflammation around dural blood vessels, sensitising trigeminal afferents and generating the characteristic throbbing pain. Central sensitisation of second-order trigeminal neurons in the trigeminocervical complex then accounts for the cutaneous allodynia many patients report during an established attack. The premonitory phase, which can precede pain by hours, is mediated by hypothalamic activation, explaining prodromal symptoms such as yawning, food cravings, and mood change. Serotonin (5-HT) signalling is integral; triptans act as 5-HT1B/1D agonists, producing vasoconstriction and inhibiting neuropeptide release to abort attacks.

3. Clinical presentation and diagnostic criteria

Diagnosis is clinical and follows International Headache Society (IHS) ICHD-3 criteria, which are accepted in Australian practice. Migraine without aura requires at least five attacks lasting 4 to 72 hours, with two of four pain features (unilateral, pulsating, moderate to severe intensity, aggravated by routine physical activity) and at least one of nausea/vomiting or combined photophobia plus phonophobia. Migraine with aura additionally requires at least two attacks with fully reversible aura symptoms developing over 5 to 60 minutes; typical aura includes visual disturbances (zigzag lines, scotomata), unilateral paraesthesia, or speech disturbance. Red flags mandating urgent investigation include sudden onset thunderclap headache, fever with meningism, focal neurological signs persisting beyond aura, new headache over age 50, headache worsening with Valsalva, and recent head trauma.

4. Investigations and AU-specific cutoffs

For patients meeting ICHD-3 criteria with no red flags, no investigations are required; migraine is a clinical diagnosis and routine neuroimaging has a low yield. Brain MRI (preferred over CT to avoid radiation, particularly in reproductive-age women) is indicated when red flags are present, when the headache pattern changes significantly, or when the diagnosis is uncertain. Cerebrospinal fluid examination is indicated when subarachnoid haemorrhage is suspected and CT head is negative: in the Australian context, xanthochromia visible on spectrophotometry is the accepted CSF finding because visual inspection alone is insufficiently sensitive. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) should be checked in patients over 50 with new-onset headache to exclude giant cell arteritis, where a temporal artery biopsy remains the gold standard. Coagulation screen and thrombophilia testing are considered in patients with hemiplegic migraine or migraine with prolonged aura given the association with patent foramen ovale and inherited thrombophilias.

5. Management

Management follows a stratified approach recommended by eTG and RACGP and is divided into acute (abortive) and preventive (prophylactic) treatment.

For acute attacks, mild to moderate episodes are treated with simple analgesics taken early: oral aspirin 900 mg or ibuprofen 400 to 800 mg with an antiemetic (metoclopramide 10 mg orally or prochlorperazine 10 mg orally) is first-line. Adding an antiemetic improves analgesic absorption by reversing gastroparesis and reduces nausea independently. For moderate to severe attacks or those failing simple analgesics, triptans are first-line: sumatriptan 50 to 100 mg orally is the most widely used in Australia, with sumatriptan 6 mg subcutaneous as the fastest-acting option for severe attacks or when vomiting precludes oral dosing. If one triptan fails, trialling a different triptan or route is reasonable before declaring class failure. Ergotamine preparations are less preferred due to a narrower therapeutic window and vasoconstriction risk. Non-steroidal anti-inflammatory drugs (NSAIDs) should be avoided in the third trimester; paracetamol is the safest analgesic option in pregnancy.

Preventive treatment is indicated when attacks occur four or more days per month, when acute medications are overused (creating medication overuse headache), or when attacks are severely disabling despite adequate acute therapy. First-line preventive agents in Australian practice include propranolol 40 to 160 mg daily (PBS listed), amitriptyline 10 to 75 mg nocte, and topiramate 25 to 100 mg daily. Candesartan 8 to 16 mg daily is an effective evidence-based alternative, particularly in patients with comorbid hypertension. Valproate is effective but is absolutely contraindicated in women of childbearing potential given teratogenicity (Neural Tube Defect Program AU). CGRP monoclonal antibodies (erenumab, fremanezumab, galcanezumab) are approved by the TGA and available under PBS authority for chronic migraine (15 or more headache days per month, 8 or more of which are migrainous) after failure of at least two conventional preventives. Non-pharmacological strategies including regular sleep, hydration, trigger avoidance, and cognitive behavioural therapy have good evidence and should be integrated into any management plan. Menstrual migraine may benefit from short-course NSAID or triptan perimenstrual prophylaxis.

6. Pharmacology and AU PBS notes

Sumatriptan 50 mg and 100 mg tablets are PBS general benefit items (no streamlined authority required). Sumatriptan 6 mg/0.5 mL subcutaneous injection is PBS listed. Zolmitriptan, rizatriptan, eletriptan, and naratriptan are also PBS listed as general benefit. Erenumab (Aimovig) 70 mg and 140 mg monthly subcutaneous injection is PBS authority (Streamlined Authority Code 11282) for chronic migraine with documented failure of at least two preventive agents; the prescriber must be or have consulted a neurologist or headache specialist. Metoclopramide is listed on the PBS; prochlorperazine is not PBS listed but is widely available as an OTC or private script item. Topiramate is PBS listed for epilepsy; its use in migraine prevention is off-label for PBS purposes, meaning patients pay private price unless the prescriber argues Section 100. Amitriptyline and propranolol are general benefit PBS items. Valproate prescribing in women of childbearing age requires compliance with the AU Pregnancy Prevention Programme including mandatory contraception and specialist oversight.

7. Complications and monitoring

Medication overuse headache (MOH) arises when acute analgesics, triptans, or ergotamines are used on 10 or more days per month for three or more months; it transforms episodic migraine into a daily or near-daily headache that paradoxically worsens with continued use. Management requires withdrawal of the overused agent, which often causes a temporary worsening for 2 to 4 weeks before improvement. Bridging with a short course of naproxen or prednisolone can ease withdrawal. Status migrainosus is a debilitating attack lasting beyond 72 hours, requiring parenteral treatment (sumatriptan subcutaneous, prochlorperazine intravenous, or IV ketorolac) and exclusion of secondary causes. Migrainous infarction is rare but defined as an ischaemic stroke occurring in the territory corresponding to the aura; combined oral contraceptive use in women with migraine with aura significantly elevates stroke risk and is a RACGP-endorsed relative contraindication. Patients on long-term topiramate should be monitored for nephrolithiasis, cognitive side effects, and weight loss. All patients on preventive therapy should be reviewed at 3 months to assess efficacy (target 50% reduction in headache days) and annually thereafter for medication rationalisation.

Written for Australian practice and grounded in the guidance named above. Study material only — not medical advice. Always check against current guidelines.