This case illustrates recurrence of a colloid cyst.
Colloid cysts are benign intracranial lesions comprising of 0.5%–1% of primary brain neoplasms and 15%–20% of intraventricular masses 1-3. They commonly occur in the third to fifth decades of life 4. They originate from the primitive neuroepithelium (which gives rise to the choroid plexus and ependyma) and studies have shown that their contents include secretory and breakdown products of the epithelial lining of the cyst, including old blood, foamy cells, fat, hemosiderin-laden macrophages, cholesterol crystals, and CSF 5.
More than 99% are found wedged in the foramen of Monro 1. The cysts are typically attached to the anterosuperior portion of the third ventricular roof, with the fornix pillars straddling the cyst and lateral splaying of the frontal horns (posterior aspect of) 1.
Clinical presentation is variable, as most colloid cysts are found incidentally and are thereby asymptomatic. The most common presenting symptom is headache associated with nausea and/or vomiting, and relieved/diminished by reclining 4. Gait disturbance, temporary loss of consciousness, sudden weakness in extremities, blurred vision, and dizziness are among the less-frequent symptoms 4.
Both CT and MRI can be used in the radiologic diagnosis of colloid cysts. On CT, colloid cysts appear 2,4,5:
- hyperdense to brain parenchyma (although rarely may be hypo/isodense)
- well-delineated, oval or rounded hyperattenuated mass on non-enhanced CT scan
- following administration of iodinated contrast material, a thin rim of enhancement may be present and may represent the cyst capsule
- periventricular hypodensity or enlarged temporal horns could be seen on a CT view due to increased intraventricular pressure and transependymal CSF leak
Using MR imaging, colloid cysts have a variable appearance 2,4,5:
- approximately half of the cysts are hyperintense when compared with brain parenchyma on T1-weighted images; the remaining cysts are iso- or hypointense
- on T2-weighted images, most colloid cysts are hypointense to the brain
- usually, there is no diffusion restriction in colloid cysts on diffusion-weighted images
- cysts that are hypointense on T2-weighted sequences may be difﬁcult to visualize using FLAIR
MR imaging may occasionally show intracystic ﬂuid levels or central and peripheral components in the lesion
Where surgical treatment is indicated (based on clinical history, examination, size and anatomical location of colloid cyst), this can be performed via a transcallosal approach, endoscopic aspiration or stereotactic excision 3. Post-surgery, it is very important to monitor for recurrence.
Case courtesy of Associate Professor Pramit Phal.