Subarachnoid hemorrhage vs Migraine
How to tell Subarachnoid hemorrhage and Migraine apart when a board question makes them look alike.
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Thunderclap onset to peak intensity within 1 minute.
Side by side
Sudden thunderclap headache reaching maximal intensity within minutes with meningismus or altered consciousness indicates subarachnoid hemorrhage.
Recurrent unilateral throbbing headache with photophobia, nausea, and possible aura that follows a stereotyped pattern suggests migraine.
Arterial bleeding into the subarachnoid space, often from ruptured saccular aneurysm, causes abrupt meningeal irritation and intracranial pressure rise.
Trigeminovascular activation and neurovascular signaling produce episodic headache and sensory symptoms without intracranial bleeding.
Noncontrast head CT is highly sensitive in first 6 hours; if CT is negative and suspicion remains, CSF xanthochromia or elevated red cells without clearing supports SAH.
Migraine has no hemorrhage on CT and no xanthochromia on lumbar puncture when imaging workup is performed for red flags.
The trap
Treating thunderclap headache as routine migraine before excluding hemorrhage can be catastrophic. A normal neurologic exam does not rule out early SAH.
The repair move
Next best step: obtain immediate noncontrast head CT, and if CT is negative but suspicion remains high, perform lumbar puncture for xanthochromia, then secure aneurysm treatment and start nimodipine 60 mg orally every 4 hours for vasospasm prevention.
Try a free question
CoreA 49-year-old woman reports abrupt severe headache during weight lifting that peaked within 30 seconds and now has neck stiffness. What is the most likely diagnosis?
Show answer and explanation
Answer: B. Subarachnoid hemorrhage. Thunderclap onset with meningismus is highly concerning for subarachnoid hemorrhage.
Why the other choices are tempting
- A. Incorrect because migraine usually has recurrent pattern and not abrupt maximal onset within seconds.
- C. Incorrect because cluster headache is unilateral orbital with autonomic features and not meningeal signs.
- D. Incorrect because tension headache is gradual and noncatastrophic in onset.
- E. Incorrect because idiopathic intracranial hypertension causes chronic pressure-type headache, not sudden thunderclap collapse.
Flashcards
Tap a card to flip it.
What onset pattern most strongly favors subarachnoid hemorrhage over migraine?
Headache that reaches maximal intensity within about 1 minute.
What historical pattern favors migraine rather than SAH?
Recurrent stereotyped unilateral throbbing episodes with aura or photophobia over time.
Quick answers
What is the fastest way to tell Subarachnoid hemorrhage from Migraine?
Thunderclap onset to peak intensity within 1 minute.
What is the key clue for Subarachnoid hemorrhage?
Sudden thunderclap headache reaching maximal intensity within minutes with meningismus or altered consciousness indicates subarachnoid hemorrhage.
What is the key clue for Migraine?
Recurrent unilateral throbbing headache with photophobia, nausea, and possible aura that follows a stereotyped pattern suggests migraine.
What is the common trap with Subarachnoid hemorrhage vs Migraine?
Treating thunderclap headache as routine migraine before excluding hemorrhage can be catastrophic. A normal neurologic exam does not rule out early SAH.