Colloid cyst - MRI

Axial non enhanced T1 magnetic resonance image showing a bright mass in the roof of third ventricle (foramen of Monro).

Axial non enhanced T2 magnetic resonance image showing a hypointense mass in the roof of third ventricle.

Sagittal non enhanced T1-weighted magnetic resonance image. This image demonstrates a round area of increased signal intensity lesion in the anterosuperior portion of the third ventricle.

Discussion:

Colloid cysts are benign, congenital epithelium-lined cysts that almost always arise in the anterior third entricle. However, rare reports describe cysts in other locations. The cysts are believed to derive from either primitive neuroepithelium of the tela choroidea or from endoderm.
Patient may present with intermittent head ache. Rarely may cause sudden death .

CT scan:

• Rounded small mass with high attenuation at the anterior third ventricle - due to proteinacious material.
• Rarely the lesion is isoattenuating or hypoattenuating relative to brain parenchyma.
• Intermittent hydrocephalus - colloid cyst act as ball valve.

MRI:

• Usually found at the foramen of Monro just posterior to the fornices in the anterosuperior third ventricle.
• MR signal intensities are variable: Variation due to contents of the cyst.
• Commonly hyperintense on T1 and iso to hypointense on T2.
• Colloid cysts do not have intrinsic enhancement; the presence of enhancement suggests a solid tumor. Peripheral enhancement may be present because of vascularity in the outer wall.