How to Diagnose Arachnoid Cysts

Arachnoid cysts are benign and are located on the cerebrospinal column. They normally contain clear, colorless cerebrospinal fluid but may be filled with a yellowish fluid on rare occasions. Arachnoid cysts arise from the arachnoid membrane usually as a congenital anomaly but also may be caused by a tumor or an adhesion from a hemorrhage, leptomeningitis or surgery. The following steps will show how to diagnose arachnoid cysts.

Instructions

1. Perform a Magnetic Resonance Image (MRI) as the diagnostic procedure of choice for identifying an arachnoid cyst. The MRI is able to determine the exact location, size and shape in relation to the brain or spinal cord. Use a myelography or CT Myelography as valuable alternatives in cases where an MRI is not definitive.

2. Rely on a cranial ultrasonography to detect and characterize cysts in patients less than a year old. Ultrasound is noninvasive and effective, although arachnoid cysts are relatively rare in infants.

3. Run an MRI with diffusion-weighted images (DWIs) to differentiate between arachnoid and epidermoid cysts. Epidermal cysts usually have a higher signal but the diagnosis can be made more difficult if the cyst contains proteinaceous fluid such as blood. Fluid-Attenuated Inversion Recovery (FLAIR) imaging will not show a signal from cerebrospinal fluid, which can make it easy to identify arachnoid cysts.

4. Differentiate between an arachnoid cyst and a large cisterna magna. An arachnoid cyst may show a mass effect and displace the cerebellum and vermis, whereas a citerna manga usually does not.

5. Detect an arachnoid cyst unexpectedly on a Computerized Tomography (CT) scan. This is not an uncommon finding in asymptomatic patients and no further investigation is needed.