T1 sagittal pre gad T1 coronal post gad T2 axial

Diagnosis: Presumed colloid cyst.

Colloid cysts are invariably located in the third ventricle at the foramen of Monro. They contain thick, viscous, proteinaceous or mucinous fluid and may grow to as large as 4 cm in diameter. Colloid cysts present in adults and make up 1/5 of all intraventricular masses. Patients often have intermittent headache secondary to obstruction of the flow of CSF through the foramina of Monro. On CT, most colloid cysts are hyperdense masses and may resemble acute hemorrhage. Calcification is not seen. Enhancement is unusual but if present is in the periphery of the cyst. They may demonstrate almost any combination of signal characteristics on MR. Usually, the central portion has increased signal on T1 with decreased signal on T2 due to the high protein content. A rind of variable thickness and signal is typical.

There is no differential in this case. The general differential of anterior third ventricular masses includes meningioma, ependymoma, choroid plexus papilloma, astrocytoma, and metastasis among others. Artifact associated with a CSF pulsation through the foramina of Monro into third ventricle can simulate a small colloid cyst on T2 weighted scans. This patient was shunted years earlier to relieve his headache and has been followed with MR ever since. Due to the typical appearance of the mass, no biopsy was performed. Related Cases

Meningioma Cavernous hemangioma Presumed colloid cyst