On MRI, a quadrigeminal plate lipoma appears as a mass with high signal intensity on T1-weighted images and low signal intensity on T2-weighted images. This is because the tumor is composed of fat, which has a high signal intensity on T1-weighted images and a low signal intensity on T2-weighted images. The tumor may also demonstrate a characteristic «Y» shape, which corresponds to the normal anatomic configuration of the quadrigeminal plate region.

In some cases, a quadrigeminal plate lipoma may be associated with hydrocephalus, which is the accumulation of cerebrospinal fluid in the brain. This can occur due to compression of the cerebral aqueduct, which is a narrow channel that connects the third and fourth ventricles in the brain. MRI can also be used to evaluate for the presence and extent of hydrocephalus, which appears as enlargement of the ventricles on T2-weighted images.

It is important to note that quadrigeminal plate lipomas are typically asymptomatic and do not require treatment. However, in some cases, they may be associated with hydrocephalus or other neurologic symptoms, which may require further evaluation and management.