📌 Start simple. Clinicians choose the fastest, safest study first—often a non-contrast CT—and step up only if symptoms or exam findings warrant more detail.
Study | Typical insurer criteria | Why it matters | Notes & prep |
CT head (no contrast) | Acute trauma, sudden severe headache (“worst ever”), stroke signs, confusion | Rapidly detects bleeding, fractures, large stroke. | ER/urgent; no IV dye; quick scan. |
MRI brain (with/without contrast) | Persistent headaches, seizures, unexplained neuro signs with normal CT, demyelinating disease | High-detail view of brain tissue, tumors, MS plaques. | Longer; no radiation; auth required. |
MRA or MRV (magnetic resonance angiography/venography) | Suspected aneurysm, arterial dissection, venous clot, TIA | Maps arteries or veins without radiation. | Often added to MRI; contrast optional; auth required. |
CTA head/neck (IV contrast) | Acute stroke evaluation when thrombectomy considered, high suspicion of aneurysm/dissection | Fast vessel map to guide emergency treatment. | IV dye; higher dose; ER context. |
CT sinus (no contrast) | Chronic sinus headaches ≥ 12 wks unresponsive to meds | Shows sinus blockage, polyps, anatomy. | Quick; moderate dose; pre-auth uncommon. |
CT maxillofacial/temporal bone | Facial trauma, chronic ear pain/hearing loss, cholesteatoma | Fine bony detail of face or ear. | Radiation; usually elective with auth. |
Carotid ultrasound (neck) | TIA, carotid bruit, stroke risk evaluation | Screens for carotid narrowing without radiation. | No pre-auth; painless; pairs with neuro work-up. |
Typical clinical sequence — general guidance
CT head (no contrast) for any sudden, severe, or trauma-related symptom.
MRI brain when CT is normal yet symptoms persist > 4 wks, or when soft-tissue detail is needed.
MRA/MRV if vascular cause (aneurysm, clot) or venous congestion is suspected.
CTA head/neck in acute stroke/TIA pathways when speed is critical.
CT sinus only after maximal medical therapy for chronic pressure/congestion headaches.
Carotid ultrasound for TIA or stroke-risk work-up when neck vessels are the likely culprit.
📌 Red-flag signs (seek emergency care): sudden “worst” headache, new weakness/numbness, slurred speech, vision loss, seizure, head trauma with vomiting.