Pediatric Colloid Cyst Of Third Ventricle

  • Etiology: Benign epithelial lined cyst containing mucin, old blood (hemosiderin), cholesterol and various ions which is located at the Foramen of Monro
  • Imaging CT:
    — Lesion is best seen on CT
    — Well defined high density lesion in the anterosuperior third ventricle at the Foramen of Monro on unenhanced CT
  • Imaging MRI: Variable appearance
    — T1WI: Often hyperintense
    — T1WI post contrast: May have peripheral rim enhancement
    — T2WI: Often isointense
  • DDX:
  • Complications: If large enough can cause acute obstructive hydrocephalus
  • Treatment: Surgical
  • Clinical: Usually asymptomatic but may present with acute obstructive hydrocephalus

Radiology Cases of Colloid Cyst of Third Ventricle

CT of colloid cyst
Axial CT without contrast of the brain shows a small, round, high density lesion in the midline in the anterior superior aspect of the third ventricle at the Foramen of Monro. The lesion could not be seen on an MRI performed at the same time.
CT of colloid cyst of third ventricle
Axial CT without contrast of the brain (above left) shows a small, round, faintly dense lesion in the midline near the Foramen of Monro in the third ventricle while the axial CT more superiorly (above right) shows dilation of the lateral ventricles with transependymal flow of cerebrospinal fluid with the right lateral ventricle herniated to the left. There are additional signs of increased intracranial pressure, evidenced by the effacement of the basilar cisterns and sulci. Coronal CT (below left) shows the faintly dense round lesion in the third ventricle which is much better seen on the coronal CT obtained after placement of a ventriculoperitoneal shunt (below right).