Erfan Bashar
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Headache Prognosis and Complications

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Educational scope notice: This is a study note for medical students, not medical advice, diagnosis, or treatment guidance. Clinical management should follow local protocols and current guidelines.

Most primary headaches do not damage the brain. Three things change the outlook: chronification through medication overuse, prolonged or infarcting migraine variants, and the complications of a missed secondary cause.

The chronification and medication-overuse loop

Medication-overuse headache means headache on at least 15 days per month after regular overuse of acute medication for more than 3 months. The day threshold is 10 or 15 days per month depending on the drug class. These thresholds are expert opinion, not trial-derived cut-points. Stopping the overuse usually improves the headache, but not invariably.

A patient can meet the criteria for chronic migraine and medication-overuse headache at the same time. That patient receives both diagnoses. About half of apparent chronic migraine reverts to episodic after withdrawal. Opiates and barbiturates carry about twice the risk of migraine progression. Triptans raise risk mainly when baseline frequency is already high. Baseline frequency itself is the major predictor. Breaking the loop is covered in /notes/neurology/headache-treatment/.

Status migrainosus

Status migrainosus is a debilitating migraine attack lasting more than 72 hours. Brief remissions of up to 12 hours from sleep or medication still count. Milder prolonged attacks are coded as probable migraine. A prolonged attack driven by medication overuse is coded as medication-overuse headache plus the migraine type, not status migrainosus.

Migrainous infarction and stroke risk

Migrainous infarction means aura symptoms persisting beyond 60 minutes with imaging proof of infarction in matching brain territory during a typical migraine-with-aura attack. It mostly affects posterior circulation in younger women. Separately, migraine with aura carries about twice the population risk of ischaemic stroke. Those strokes are not migrainous infarctions, and the mechanism behind the extra risk is unknown.

Complications of missed subarachnoid hemorrhage

A missed subarachnoid hemorrhage can rebleed. Rebleeding affects 9–17% within the first 72 hours, with up to 50% mortality. Securing the aneurysm drops rebleed risk to about 1%, preferably within 24 hours. About 60% of patients develop radiographic vasospasm and about 39% clinical vasospasm causing delayed cerebral ischaemia. Early enteral nimodipine prevents delayed ischaemia and improves functional outcome. A 21-day oral course is standard of care. Statins and intravenous magnesium are not recommended. Hydrocephalus affects up to 30%, often within the first 3 days. Vasospasm surveillance concentrates approximately around days 3–10. The alarm pattern itself is described in /notes/neurology/headache-secondary-causes/.

Course of post-dural puncture headache

Post-dural puncture headache usually starts within 48–72 hours and within 5 days of the puncture. Over two-thirds of patients recover spontaneously within about 2 weeks. Epidural blood patch with 10–30 mL of autologous blood is definitive when conservative care fails. It succeeds in over 75–90%, especially when repeated. Rare severe sequelae include subdural haematoma, cerebral venous thrombosis, and seizures.

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