On MRI, which finding indicates breakdown of the blood-brain barrier in the context of tumors?

• A. Calcifications
• B. Blood-brain barrier breakdown
• C. Edema
• D. Hyperintensity

Answer: (B)

When a tumor disrupts the blood-brain barrier, the tight junctions between endothelial cells become leaky. This allows gadolinium-based contrast to escape from the vessels into the surrounding interstitial tissue. On MRI, that leakage shows up as enhancement on post-contrast T1-weighted images, which is the direct imaging sign of barrier disruption. Edema often accompanies tumors and reflects fluid accumulation, but it is not itself the specific indicator of barrier breakdown. Calcifications are a different feature and do not indicate permeability changes, and hyperintensity can occur on various sequences for various reasons, not specifically the barrier status. So the most definitive indication of blood-brain barrier breakdown in this context is the contrast enhancement resulting from gadolinium leakage into the tumor interstitium.