Third ventricular colloid cyst
Colloid cysts of the third ventricle are benign, slow-growing cranial tumors believed to have an epithelial wall, the same type of cells that compose skin. These mucous-filled masses most commonly appear near the center of the brain, at the point where two of the natural fluid chambers of the brain, the lateral ventricles, drain into the third ventricle. They are typically found in the anterior portion of the third ventricle near the foramen of Monro.
By obstructing the flow of fluid into the third ventricle, colloid cysts can cause headache, confusion, acute hydrocephalus, brain herniation, and lead to death. Relatively rare, third ventricular colloid cysts are usually found in adults age 40 to 50.
In the vast majority of cases, colloid cysts are found incidentally and are asymptomatic. Their position in the roof of the third ventricle may result in sudden acute hydrocephalus and severe headaches. The headaches are typically worse in the morning and may worsen when the head is leaned forward.
Other symptoms include:
- Difficulty walking
- Short-term memory loss
- Nausea and vomiting
- Behavioral changes
- Sudden weakness in the lower limbs associated with falls
Acute hydrocephalus can occur if the cyst blocks the flow of cerebrospinal fluid, causing nausea, vomiting, headache and lethargy. Death may occur due to the rapid obstruction of cerebrospinal fluid at the foramen of Monro. The fluid build-up behind the blockage puts pressure on the brain, which can cause the brain to herniate through the base of the skull.
Diagnosis is made with an MRI or a CT scan. Head CT scans reveal a very dense lesion. MRI provides a better picture of the regional anatomy around the cyst. Lumbar puncture should never be performed in a patient with a colloid cyst due to the risk of brain herniation.
Treatment of colloid cysts is surgical. There are a number of approaches, including the use of an endoscope or the use of stereotactic guidance systems. Open microsurgical removal is still considered the gold-standard treatment. In patients with contraindications to surgery, bilateral cerebrospinal fluid shunts can be placed to prevent acute hydrocephalus from developing. Surgery to remove the colloid cyst generally cures the patient.