Modality
CT and MR angiography
Vascular imaging answers the most time-critical question in vertigo — is the posterior circulation compromised? CT angiography offers spatial resolution and speed; MR angiography offers a contrast-free, radiation-free alternative with slightly lower sensitivity for subtle pathology.
Choosing CTA versus MRA
When acute vertigo carries vascular features — sudden onset, vascular risk, neck pain, headache, focal neurology — angiography is the test that finds the substrate. CTA is faster and higher-resolution; MRA avoids radiation and iodinated contrast.
CTA uses iodinated contrast and a fast volumetric CT acquisition. Resolution is sub-millimetre, so subtle pathology — small dissection flaps, short stenoses, mural haematomas — is more reliably caught.1It is the preferred test in the emergency setting and the natural follow-on from a stroke-protocol CT.
MRA in its TOF form is contrast-free and works from intrinsic flow contrast. Sensitivity for subtle dissection or slow flow is lower, and motion sensitivity is higher; for the uncooperative or unstable patient CTA usually wins. In elective workup of younger patients or those with contrast contraindications, MRA is the comfortable first choice.
Three clinical pictures should provoke an angiographic study:
- Acute vestibular syndrome with central HINTS — to define the vascular substrate of a suspected cerebellar/brainstem infarct; consider thrombectomy candidacy.
- Vertigo with occipital headache or neck pain, particularly in a younger patient or after manipulation — to evaluate for vertebral artery dissection.
- Recurrent dizziness in an older adult with vascular risk — to confirm or exclude VBI as the substrate.2
Beware: even a normal MRI does not rule out a small infarct — small posterior- fossa strokes can be missed in the first 24–48 h.3Angiography may be the only positive finding in that window.
Posterior-circulation territories — and their bedside signatures
Match the syndrome to the territory. Each cerebellar artery serves a different bit of brain and produces a different combination of vertigo plus other neurology. AICA, in particular, is the territory to remember — it co-supplies the inner ear and so produces a clinical picture that imitates labyrinthitis.
Reading the dissection
- Intimal flap — a thin, linear filling defect within the lumen.
- Crescent-shaped mural haematoma — high-signal crescent narrowing the lumen on fat-suppressed axial T1.
- Double-lumen sign — true and false channels visible together.
- Tapering “string-of-beads” stenosis — a long, smoothly tapered narrowing of the affected vertebral segment.
Limitations
- CTA: ionising radiation; iodinated contrast cautions in renal disease and allergy.
- MRA: lower sensitivity for short or subtle pathology; motion sensitivity; slow flow can mimic stenosis.
- Both: cannot characterise the perfusion deficit itself — DWI MRI is needed for the parenchymal lesion.