Colloid Cyst

Institute of Cancer Research

What is a colloid cyst?

Colloid cysts are generally slow-growing, non-cancerous brain tumours located in the third ventricle, a fluid-filled cavity in the centre of the brain. 

They are quite rare, and make up less than 2% of all primary brain tumours. This equates to less than 255 people per year in the UK.

Colloid cysts are small fluid-filled sacs.

What are brain tumours?Other types of brain tumours

What are the symptoms of a colloid cyst? 

Patients with colloid cysts are commonly asymptomatic (no symptoms), which is why many cysts are often discovered by accident during imaging for other conditions, such as during MRI or CT scans.

Due to their location in the ventricle, some colloid cysts can block the flow of cerebral spinal fluid (CSF) and cause hydrocephalus (a build-up of fluid in the brain). This can increase the pressure within the brain, which can be life-threatening.

It can also cause the following symptoms:

  • Headaches (most common)

  • Nausea or vomiting

  • Visual disturbances

  • Memory problems

  • Dizziness or vertigo

What causes a colloid cyst? 

The causes of a colloid cyst are currently unclear, though they are believed to form during embryo development.

How is a colloid cyst treated?

If the cyst is small and not causing any symptoms, the patient may be monitored over time with regular MRI scans. If the cyst is large or is causing symptoms, such as hydrocephalus, then it can be removed by surgery.  The treatment plan will vary from person to person.

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