Colloid cyst

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Clinical History:
A 27-year-old woman who began to have headaches over the past 2 months, and then presented with significant nausea, vomiting, and lethargy

Diagnosis:
Colloid cyst, with obstructive hydrocephalus

MR Technique:
4 mm pre-contrast axial FSE (21 echoes) T2- and sagittal FSE (6 echoes) T1-weighted (T1-FLAIR) images are presented, acquired at 3 T on a Siemens Verio MR system. Sequence parameters were TR/TE = 5500/86 and TR/TE/TI = 2100/9/896 respectively. Scan times were 2:22 and 3:18 min:sec.

Imaging Findings:
A round mass is identified measuring 1.4 cm in greatest axial dimension in the region of the foramen of Monro. The mass is hyperintense on the T1-weighted image and intermediate signal intensity on the T2-weighted image. It did not demonstrate restricted diffusion. There is associated prominent hydrocephalus with enlargement of the lateral ventricles. Increased signal intensity is noted involving the immediate periventricular white matter on the T2-weighted scan (better visualized on FLAIR, not illustrated) consistent with transependymal migration of CSF. The cerebellar tonsils are slightly low in position and somewhat pointed. The ventricular and tonsillar findings are consistent with acute obstructive hydrocephalus.

A colloid cyst is a mucin-containing 3rd ventricular cyst. They are classically located in the anterior superior 3rd ventricle, and can cause acute obstructive hydrocephalus by occlusion of the foramen of Monro. Their size is variable, from a few mm to several cm. Small lesions may be difficult to identify. In terms of signal characteristics, this reflects on T1-weighted scans their cholesterol concentration, with 2/3rd hyperintense (as illustrated) and 1/3rd isointense. The majority are isointense to brain on T2-weighted scans.