What is the name of the rare cystic lesion typically found at the anterior roof of the third ventricle near the foramen of Monro, often presenting with obstructive hydrocephalus due to its location?

Colloid cyst. These lesions are generally hyperdense compared to brain parenchyma on CT and do not enhance with contrast. MRI may show variable signal intensity on T1 and T2-weighted images. Clinically, they can cause headaches, memory disturbances, or sudden death due to acute hydrocephalus. Common mimickers include ependymal cysts and neurocysticercosis.