Confusable diagnoses · PANCE / PANRE

Subarachnoid Hemorrhage vs Migraine

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Subarachnoid Hemorrhage and Migraine are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Subarachnoid Hemorrhage vs Migraine at a glance

  • Subarachnoid Hemorrhage: Bleeding into the subarachnoid space; most spontaneous (nontraumatic) cases are from a ruptured saccular aneurysm.
  • Migraine: Recurrent primary headache disorder with unilateral throbbing pain, photophobia, nausea.

Try two board-style questions on Subarachnoid Hemorrhage vs Migraine

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Question 1NeurologyMedium
A 28-year-old female has sudden-onset thunderclap headache (10/10, worst headache of her life) reaching maximum intensity within seconds. CT head is negative. Lumbar puncture shows xanthochromic CSF and 2,000 RBCs per tube that do not clear from tube 1 to tube 4. Which of the following is the most likely diagnosis?
  • ASubarachnoid hemorrhage
  • BViral meningitis
  • CReversible cerebral vasoconstriction syndrome
  • DCervical artery dissection
Reveal answer & full explanation
Correct answer: A — Subarachnoid hemorrhage
  • ASubarachnoid hemorrhage✓
  • BViral meningitis
  • CReversible cerebral vasoconstriction syndrome
  • DCervical artery dissection

Why Subarachnoid hemorrhage is correct

  • Thunderclap headache (sudden maximum-intensity onset) is subarachnoid hemorrhage (SAH) until proven otherwise
  • CT sensitivity is ~98-100% in the first 6 hours but declines to ~85% at 24 hours, so a negative CT obtained later does not rule out SAH
  • After a negative CT obtained more than 6 hours from onset (or with a new neurologic deficit), lumbar puncture (LP) is indicated; a negative high-quality CT within 6 hours in a neurologically intact patient can exclude SAH
  • Xanthochromia (yellow CSF from hemoglobin breakdown) can begin within a few hours but is reliably present only about 12 hours after the bleed, and persists for about 2 weeks
  • Non-clearing RBCs (RBCs do not decrease from tube 1 to tube 4) support true SAH over a traumatic LP, but tube-to-tube clearing is unreliable, so xanthochromia is the more reliable discriminator
  • Most common cause of spontaneous (nontraumatic) SAH: ruptured saccular (berry) aneurysm (85%) — anterior communicating artery is most common

Why the others are wrong

  • Viral meningitis — CSF would show pleocytosis, not xanthochromia and non-clearing RBCs; onset is typically not thunderclap
  • Reversible cerebral vasoconstriction syndrome — also causes thunderclap headache, but the CSF is typically normal without xanthochromia
  • Cervical artery dissection — a real cause of abrupt severe headache in a young adult, but it usually brings neck pain, a partial Horner syndrome, or ischemic deficits, and an extracranial dissection leaves the CSF clear rather than xanthochromic with non-clearing red cells

Additional high-yield points

  • CT angiography (CTA): sensitive (above 95%) for aneurysms above 3 mm — first-line non-invasive vascular imaging
  • Catheter angiography (digital subtraction angiography (DSA)) is the gold standard if CTA is negative
  • Treatment: urgent neurosurgical consultation; aneurysm securing by clipping or coiling (ISAT trial: coiling superior for eligible aneurysms)
  • Nimodipine 60 mg PO q4h x21 days reduces delayed cerebral ischemia
  • Additional management: strict BP control; euvolemia; avoid fever; monitor for hydrocephalus
Question 2NeurologyEasy
A 32-year-old woman has 8 migraine days per month despite trials of sumatriptan and naproxen. She has tried propranolol and topiramate without benefit and would like to start preventive therapy that targets the calcitonin gene-related peptide pathway. Which of the following is the most appropriate medication?
  • AErenumab
  • BOnabotulinumtoxin A
  • CVerapamil
  • DAmitriptyline
Reveal answer & full explanation
Correct answer: A — Erenumab
  • AErenumab✓
  • BOnabotulinumtoxin A
  • CVerapamil
  • DAmitriptyline

Why erenumab is correct

  • Calcitonin gene-related peptide (CGRP) monoclonal antibodies — including erenumab, fremanezumab, galcanezumab, and eptinezumab — are FDA-approved for episodic and chronic migraine prevention and specifically target the CGRP pathway.
  • They reduce migraine days by ~50% in roughly half of patients, with excellent tolerability and no CNS side effects.
  • Most are monthly subcutaneous injections; eptinezumab is administered intravenously quarterly.

Why the others are wrong

  • B) OnabotulinumtoxinA — FDA-approved for chronic migraine prevention (≥15 headache days/month) but does not target the CGRP pathway; this patient has 8 migraine days/month (episodic migraine).
  • C) Verapamil — Used for cluster headache prevention, not the preferred agent for migraine and does not target the CGRP pathway.
  • D) Amitriptyline — A tricyclic antidepressant used as migraine prophylaxis but does not target the CGRP pathway, which is what the patient specifically requests.

Additional high-yield points

  • Gepants (ubrogepant, rimegepant) are CGRP receptor antagonists used for acute treatment and, for some agents, prevention.
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Side-by-side comparison

FeatureSubarachnoid HemorrhageMigraine
At a glanceBleeding into the subarachnoid space; most spontaneous (nontraumatic) cases are from a ruptured saccular aneurysm.Recurrent primary headache disorder with unilateral throbbing pain, photophobia, nausea.
Classic presentationThunderclap headache + meningismus + LOC. Hunt-Hess and World Federation of Neurosurgical Societies (WFNS) grading scales predict outcome.; Sudden severe headache ('thunderclap,' 'worst headache of life,' maximal within seconds); Brief loss of consciousness in ~50%; Nausea, vomiting, photophobia; Meningismus develops over hours from…POUND mnemonic: Pulsatile, One-day duration (4-72 h), Unilateral, Nausea, Disabling — 4 of 5 features highly suggest migraine.; Prodrome (hours-days before): mood changes, food cravings, neck stiffness, yawning, urinary frequency; Aura (~25%): visual (scintillating scotoma, fortification spectra, hemianopia), sensory (paresthesias…
Workup / key labsSubarachnoid blood on CT in basal cisterns, sylvian fissure, or interhemispheric fissure; or xanthochromia on LP.; CBC, coagulation panel, BMP, troponin (neurogenic stunned myocardium common); Type and screenICHD-3 criteria for migraine without aura: ≥5 attacks lasting 4-72 hours, with ≥2 of [unilateral, pulsating, moderate-severe, aggravated by activity] AND ≥1 of [nausea/vomiting, photophobia + phonophobia]. Migraine with aura: ≥2 attacks of fully reversible aura symptoms (most often visual, sensory, or speech/language) with typical…
ImagingNon-contrast head CT within 6 h of symptom onset is ~100% sensitive (drops to ~85% at 24 h, ~50% at 1 week); Lumbar puncture if CT negative but clinical suspicion remains — xanthochromia (yellow CSF from hemoglobin breakdown) confirms SAH; RBCs that don't clear between tubes 1 and 4 support SAH, but tube-to-tube clearing is unreliable,…Neuroimaging NOT routinely indicated for typical migraine with normal exam; MRI brain indicated for: red flags (SNOOP: Systemic symptoms/Secondary risk factors, Neurologic signs, Onset sudden/thunderclap, Older age >50 with new headache, Pattern change/Progressive/Positional/Precipitated by Valsalva); Lumbar puncture if SAH or…
First-line treatmentABCs; intubate if GCS ≤8 or airway compromise; BP control: target SBP <160 (or MAP <110) until aneurysm secured — IV nicardipine, clevidipine, or labetalol; Pain control (acetaminophen, opioids; avoid antiplatelet/NSAID); Antiemetics, stool softeners (avoid Valsalva); Nimodipine 60 mg PO/NG q4h × 21 days — improves neurologic outcomes…Abortive: NSAIDs (ibuprofen 400-800 mg, naproxen 500 mg) for mild-moderate attacks; Triptan (5-HT1B/1D agonist: 1B causes cranial vasoconstriction, the basis of its cardiovascular contraindications; 1D inhibits trigeminal CGRP and substance P release) — sumatriptan 50-100 mg PO (also 6 mg SC, 20 mg nasal), rizatriptan 10 mg, eletriptan…

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Full outlines

Subarachnoid Hemorrhage (SAH) Migraine All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.