Arteriovenous malformations (AVMs) are congenital vascular anomalies characterized by a tangle of abnormal vessels (nidus) connecting arteries directly to veins, bypassing capillaries. They are important causes of intracranial hemorrhage, seizures, and headaches in young patients.
📌 CT Imaging
- Non-contrast CT (NCCT):
- May show acute intraparenchymal hemorrhage (most common presentation).
- Serpiginous or tubular hyperdensities (thrombosed vessels).
- CT Angiography (CTA):
- Non-invasive, rapid.
- Demonstrates feeding arteries, nidus, and draining veins.
- Useful for screening and surgical planning.
📌 MRI Imaging
- T1/T2: Multiple serpiginous flow voids (signal void tubular structures in nidus).
- FLAIR: May show perilesional gliosis or edema.
- GRE/SWI: Detects associated microhemorrhages or calcifications.
- Contrast MRI: Intense vascular enhancement of nidus and draining veins.
- MRA: Non-invasive evaluation of feeders/drainage; less sensitive than DSA.
📌 Digital Subtraction Angiography (DSA) – Gold Standard
- Provides dynamic vascular anatomy.
- Identifies:
- Feeding arteries
- Nidus
- Early venous drainage
- Essential for Spetzler–Martin grading and treatment planning (embolization, radiosurgery, or surgery).
📌 Complications Seen on Imaging
- Hemorrhage (intraparenchymal, intraventricular, subarachnoid).
- Gliosis/encephalomalacia from prior bleeds.
- Venous hypertension → ischemia.
- Associated aneurysms in feeding arteries (rupture risk).
📌 Teaching Pearls
- MRI/MRA is best for initial non-invasive diagnosis.
- CTA is fast and widely available, excellent in acute hemorrhage.
- DSA remains gold standard for full anatomical delineation and therapeutic planning.
- Always evaluate for associated aneurysm in AVM patients.
🧾 Imaging Modalities in AVMs – Comparison
| Modality | Strengths | Limitations | Best Use |
|---|---|---|---|
| CT / CTA | – Rapid, widely available – Excellent for acute hemorrhage – Visualizes nidus, feeding arteries, draining veins – 3D reconstructions helpful for surgery | – Radiation + contrast exposure – Limited hemodynamic information compared to DSA | First-line in acute bleed, quick vascular screening |
| MRI / MRA | – No radiation – Superior soft-tissue contrast – Flow voids on T1/T2 → nidus detection – Detects gliosis, encephalomalacia, microbleeds (SWI) – Good for follow-up | – Longer acquisition time – Less sensitive than DSA for small vessels/aneurysms | Non-invasive diagnosis, chronic evaluation, follow-up |
| DSA (Digital Subtraction Angiography) | – Gold standard for AVMs – Dynamic, high-resolution vascular anatomy – Precise identification of feeding arteries, nidus, and early venous drainage – Allows therapeutic intervention (embolization) | – Invasive, risk of complications (stroke, dissection) – Requires expertise and contrast exposure | Definitive diagnosis, grading (Spetzler–Martin), pre-treatment planning |
📌 Teaching Pearl
- CTA → Fast & first-line in emergencies.
- MRI/MRA → Best for non-invasive diagnosis and follow-up.
- DSA → Gold standard for anatomy + treatment planning.
