Colloid Cyst of the 3rd Ventricle

General Considerations

• Benign, epithelium-lined cysts
• Most common tumor of the third ventricle but rare overall
• Usually found in adults in their 40s or 50s
• Arise from anterosuperior aspect of 3^rd ventricle near the foramina of Monro
• Cysts are usually filled with a thick mucus-like material although some are filled with thinner, serous fluid

Clinical Findings

• Typically asymptomatic
• Normally, CSF exits lateral ventricles through the foramina of Monro to enter 3^rd ventricle
• Colloid cysts obstruct the foramina leading to hydrocephalus
• Headaches
• Coma
• Sudden death

Imaging Findings

• CT or MRI may be used to diagnose a colloid cyst
• CT
  • Round mass in anterior 3^rd ventricle with high attenuation
  • Hydrocephalus
• MRI
  • Imaging characteristics of the cyst are variable
  • Most commonly, they are hyperintense on T1 and isointense to hypointense on T2
  • They do not enhance

Treatment

• Hydrocephalus is generally considered an indication for surgery
• Cysts with high T2-signal intensity are more easily treated with minimally invasive surgical techniques

Complications

• Hydrocephalus can remain after surgery so a ventricular drainage catheter (shunt) is frequently inserted

Prognosis

• Colloid cysts are cured following their removal

Colloid Cyst of the Third Ventricle. There is a high attenuation mass in the anterior aspect of the third ventricle (white arrow) causing obstruction at the foramina of Monro with resultant hydrocephalus, left (yellow arrow) frontal horn worse than right (blue arrow) on the axial CT scans (above). The bodies of the lateral ventricles are dilated (green arrows). Below, the mass is hypoattenuating on T1 FLAIR image (white arrow) and hyperattenuating on T2 FLAIR image (yellow arrow).
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Colloid Cyst. eMedicine. Andrew L Wagner, MD