Write a short note on migraine and trigeminal neuralgia.

Migraine — Definition

Migraine is a primary headache disorder characterised by recurrent attacks of moderate to severe, often unilateral, throbbing headache lasting 4–72 hours, aggravated by routine activity, and accompanied by nausea, vomiting, photophobia and phonophobia. It affects up to 15% of the population, women three times more often than men.

Pathophysiology

The old vascular theory has been replaced by a neurovascular model: cortical spreading depression (a wave of neuronal depolarisation followed by suppression, moving across the cortex at 3–5 mm/min) underlies the aura; activation of the trigeminovascular system releases calcitonin gene-related peptide (CGRP) and substance P, causing neurogenic inflammation, meningeal vasodilatation and pain. CGRP is the target of the newest and most effective preventive drugs.

Clinical Features — the Four Phases

1. Prodrome (hours to days before): mood change, yawning, food craving, neck stiffness, fatigue.

2. Aura (in about 25%): fully reversible focal neurological symptoms developing over 5–20 minutes and lasting under 60 minutes. Most commonly visual — fortification spectra, zigzag lines, scintillating scotoma; less often sensory (spreading paraesthesiae), speech disturbance, or motor (hemiplegic migraine).

3. Headache: unilateral (though may be bilateral), pulsating, moderate to severe, worsened by movement, with nausea, vomiting, photophobia and phonophobia; the patient seeks a dark quiet room.

4. Postdrome: exhaustion, poor concentration, "hangover" feeling for a day.

Triggers: stress and relief from stress, missed meals and fasting, sleep deprivation or excess, menstruation and the oral contraceptive pill, alcohol (especially red wine), specific foods (cheese, chocolate, MSG, aspartame), bright light, strong smells, and weather change.

Diagnosis and Red Flags

Migraine is a clinical diagnosis; no investigation confirms it. Imaging is required only if there are red flags — the SNOOP features:

• Systemic symptoms (fever, weight loss) or Secondary risk (HIV, cancer, immunosuppression)
• Neurological signs or deficit
• Onset sudden ("thunderclap" — think subarachnoid haemorrhage)
• Older age at onset (new headache over 50 — think giant cell arteritis or tumour)
• Papilloedema, Pattern change, Positional or Precipitated by Valsalva.

Management

Acute treatment — take early, at the first sign:

• Simple analgesics: aspirin, paracetamol, NSAIDs — effective for many attacks.
• Antiemetics: metoclopramide or domperidone — treat nausea and also improve absorption of analgesics through gastric stasis.
• Triptans (sumatriptan, rizatriptan) — 5-HT1B/1D agonists; the specific acute treatment for moderate to severe attacks. Contraindicated in ischaemic heart disease, uncontrolled hypertension, and hemiplegic or basilar migraine.
• CGRP receptor antagonists (gepants) and ditans where triptans are contraindicated or ineffective.
• Avoid opioids — they are ineffective and promote medication-overuse headache.

Preventive treatment — indicated for four or more attacks per month, disabling attacks, or acute treatment failure:

• Beta-blockers (propranolol) — first-line; avoid in asthma.
• Amitriptyline — useful where there is coexisting tension headache, insomnia or depression.
• Topiramate and sodium valproate (valproate must be avoided in women of childbearing potential).
• Flunarizine — widely used in India.
• CGRP monoclonal antibodies (erenumab, fremanezumab, galcanezumab) — highly effective for refractory chronic migraine.
• Botulinum toxin for chronic migraine.
• Preventives must be given an adequate trial of 2–3 months at a therapeutic dose before being judged ineffective.

Non-pharmacological: headache diary to identify triggers, regular sleep and meals, hydration, exercise, stress management, and limiting acute medication to fewer than 10–15 days per month to prevent medication-overuse headache — an under-recognised and very common cause of chronic daily headache.

Trigeminal Neuralgia

Definition: a disorder of paroxysmal, brief, severe, electric shock-like or stabbing facial pain confined to one or more divisions of the trigeminal nerve, triggered by innocuous stimuli. Also known as tic douloureux. It is commoner in women over 50.

Aetiology:

• Classical: neurovascular compression of the trigeminal root entry zone, usually by an aberrant loop of the superior cerebellar artery, causing focal demyelination.
• Secondary: multiple sclerosis (suspect strongly in a young patient or where the pain is bilateral), cerebellopontine angle tumour, brainstem infarct, herpes zoster.

Clinical features:

• Unilateral, in the maxillary (V2) and mandibular (V3) divisions most often; ophthalmic division is least commonly involved.
• Paroxysms lasting seconds to two minutes, repeated many times a day, with complete freedom between attacks in the early years.
• Triggered by light touch — washing the face, shaving, brushing teeth, chewing, talking, cold wind. Patients may avoid eating and washing, and lose weight.
• The neurological examination is NORMAL in classical trigeminal neuralgia. Sensory loss, corneal reflex depression, or other cranial nerve signs indicate a secondary cause and mandate MRI.

Investigations: MRI brain with dedicated trigeminal sequences — to demonstrate neurovascular compression and to exclude multiple sclerosis and tumour, particularly in the young or where there are abnormal signs.

Management:

• Carbamazepine — the drug of choice and first-line, with a response that is so characteristic that failure should prompt review of the diagnosis. Monitor for hyponatraemia, rash including SJS/TEN (HLA-B*1502 association), leucopenia and ataxia.
• Oxcarbazepine — better tolerated alternative; also lamotrigine, baclofen, gabapentin, pregabalin and phenytoin.
• Surgical options for drug failure or intolerance: microvascular decompression (Jannetta procedure — the most durable, addressing the cause), percutaneous procedures (radiofrequency thermocoagulation, glycerol injection, balloon compression), and stereotactic radiosurgery (gamma knife).