What is Colloid Cyst?

A colloid cyst is a benign cystic lesion that most often forms in the third ventricle, a fluid-filled space near the center of the brain. Colloid cysts are not cancer, but their location can be important because they may block the normal flow of cerebrospinal fluid, also called CSF.

When a colloid cyst blocks CSF flow near the foramen of Monro, fluid can build up in the brain and cause hydrocephalus. Hydrocephalus means that too much cerebrospinal fluid is collecting in the ventricles, which can increase pressure inside the head and cause neurological symptoms.

De Novo Brain & Spine evaluates adult patients with suspected or confirmed colloid cysts to help determine the appropriate next step. Evaluation may include neurological examination, brain MRI, CT imaging, review of ventricular size, monitoring with repeat imaging, or surgical consultation when symptoms or hydrocephalus are present.

Common Signs and Symptoms

Colloid cyst symptoms depend on the size of the cyst, whether it blocks cerebrospinal fluid flow, and whether hydrocephalus is present. Some colloid cysts are found incidentally on imaging and may not cause symptoms.

Common signs and symptoms may include:

• Headaches, sometimes worsening over time
• Headaches with nausea or vomiting
• Positional headaches, meaning headaches that change with body position
• Dizziness or balance problems
• Blurred vision, double vision, or other visual changes
• Memory problems or difficulty concentrating
• Confusion or changes in alertness
• Trouble walking or problems with coordination
• Fatigue or drowsiness
• Brief episodes of fainting or loss of consciousness in some cases

Seek emergency medical care or call 911 for a sudden severe headache, repeated vomiting, fainting, new confusion, sudden weakness, seizure, loss of consciousness, or rapid neurological decline.

What Causes This Condition

The exact cause of most colloid cysts is not clearly known. Many are described as developmental cysts, meaning they may form from tissue present during early development rather than from cancer or spread of disease.

Important facts about colloid cyst causes include:

• Colloid cysts are usually benign, meaning noncancerous
• They are most often located in or near the third ventricle
• They are not usually caused by head injury, routine activity, or lifestyle factors
• They do not usually spread to other parts of the brain or body
• Symptoms occur mainly when the cyst blocks CSF flow or causes hydrocephalus

The clinical concern with a colloid cyst is usually its location and effect on cerebrospinal fluid flow, not cancer behavior.

How It Is Diagnosed

A colloid cyst cannot be diagnosed by symptoms alone. Diagnosis usually depends on medical history, neurological examination, and brain imaging.

Common diagnostic steps may include:

• Medical history and neurological examination to evaluate headaches, memory, vision, balance, strength, sensation, coordination, and alertness
• MRI of the brain with and without contrast to define the cyst’s location, size, and relationship to the ventricles
• CT scan of the head, especially in urgent situations or when MRI is not immediately available
• Review of ventricular size to determine whether the cyst is causing hydrocephalus
• Comparison with prior imaging when available to assess whether the cyst has changed over time
• Repeat MRI or CT imaging when observation is chosen
• Surgical planning imaging when removal of the cyst is being considered

The goal of diagnosis is to determine whether the colloid cyst is causing symptoms, blocking cerebrospinal fluid flow, enlarging over time, or creating a risk of hydrocephalus.

Treatment Options

Colloid cyst treatment depends on the cyst’s size, location, symptoms, ventricular size, hydrocephalus, imaging findings, neurological examination, and the patient’s overall health. Some colloid cysts can be monitored, while others may require surgery.

Treatment options may include:

• Observation with repeat imaging for selected small or asymptomatic colloid cysts that are not causing hydrocephalus
• Medication for symptom control in limited situations, although medication does not remove the cyst or correct CSF blockage
• Endoscopic colloid cyst removal, a minimally invasive surgical approach that uses a small camera and instruments to reach the cyst through the ventricular system
• Microsurgical colloid cyst removal, which may be considered depending on cyst size, anatomy, surgeon assessment, and patient-specific factors
• Image-guided surgical planning to help identify the cyst’s location and nearby brain structures
• Cerebrospinal fluid diversion, such as temporary drainage or shunt placement, in selected cases when hydrocephalus needs to be treated
• Follow-up imaging after observation or treatment to monitor the ventricles and cyst area when appropriate

Surgery may be considered when a colloid cyst is causing symptoms, obstructing cerebrospinal fluid flow, causing hydrocephalus, increasing in size, or judged to carry a higher clinical risk. The safest plan depends on the patient’s imaging, symptoms, and overall condition.