An MRI (magnetic resonance imaging) scan uses a magnetic field rather than X-rays to provide detailed images of the brain, nerves, and tissues around the skull base. It is not needed for every patient — a CT scan is usually enough for routine sinus problems. MRI is most useful in the more complex situations described below. For how the two scans compare, see Understanding CT and MRI Scans.
Complex Chronic Rhinosinusitis
Most chronic rhinosinusitis is evaluated with a CT scan alone. An MRI may be added in more complex cases, such as concern that disease is extending beyond the sinuses, or when a clearer picture of the surrounding areas is needed than a CT scan provides.
Nose, Sinus & Skull Base Tumors
MRI is especially useful for tumors, because it shows the detail needed to determine how far a growth extends, and whether it reaches the brain, nerves, or the areas close to the skull base. It is often used together with a CT scan, which shows the surrounding bone.
CSF Leaks
MRI may help evaluate a suspected CSF (cerebrospinal fluid) leak and localize the site when needed, particularly when the exact site is not clear from a CT scan alone.
What to Expect
An MRI takes longer than a CT scan, usually 30–45 minutes, and means lying still inside a scanner. Some MRI scans use an injected dye to show certain tissues more clearly.