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Colloid Cysts

  • Author: Lawrence S Chin, MD, FACS; Chief Editor: Brian H Kopell, MD  more...
Updated: Apr 18, 2016

History of the Procedure

In 1858, Wallmann first reported on colloid cysts. In 1921, Dandy accomplished the first successful resection of a colloid cyst through a transcortical transventricular approach. Since then, different operative approaches such as transcortical-transventricular and transcallosal were developed.[1, 2, 3, 4, 5, 6, 7, 8, 9, 10] Less invasive techniques were then developed as an alternative to reduce the complications of the open approach. Freehand aspiration of a colloid cyst was performed first by Gutierrez-Lara et al in 1975.[11] The first stereotactic aspiration of a colloid cyst was performed in 1978 by Bosch et al.[12] Endoscopic aspiration of a colloid cyst was reported by Powell et al in 1983[13] and has progressively gained consensus as a safe alternative treatment.



Colloid cysts are non-neoplastic epithelium-lined cysts of the central nervous system that almost always arise from the anterior third ventricle roof (immediately posterior to the foramen of Monro). These epithelium-lined, mucin-containing cysts can be found in asymptomatic patients; however, depending on their location, size, and degree of cerebrospinal fluid (CSF) obstruction, patients may present with a variety of neurological symptoms. These symptoms can range from headaches to death on rare occasions when there is acute hydrocephalus.[14]

In a single-center retrospective review of 163 colloid cysts of the third ventricle according to Beaumont et al, about 60% of colloid cysts of the third ventricle were discovered incidentally during evaluation for other neurologic diseases, such as head trauma, stroke metastatic workup, and metabolic diseases. Five patients with incidental cysts (8.8%) progressed and underwent resection. However, none of the asymptomatic patients with incidental colloid cysts developed acute obstructive hydrocephalus or acute neurologic deterioration. Nearly half (46.2%) of symptomatic patients presented with hydrocephalus. Eight patients (12.3%) presented acutely, and there were 2 deaths due to obstructive,hydrocephalus and herniation.[14]

The image below depicts a colloid cyst at the foramen of Monro causing hydrocephalus.

Axial CT scan that shows a colloid cyst with assoc Axial CT scan that shows a colloid cyst with associated hydrocephalus.


Colloid cysts account for approximately 2% of primary brain tumors, and the majority of cases are identified in the fourth and fifth decade. Eighty percent of the patients with colloid cyst reported in the literature are aged 30-60 years. Approximately 15-20% of all intraventricular masses are colloid cysts. Colloid cysts develop in the rostral aspect of the third ventricle in the foramen of Monro in 99% of cases, and despite their benign histology, they may carry high risks and neurologic complications, with a mortality reported from  3.1% to 10%  in symptomatic cases or 1.2% in total.[14, 15]  

Although these tumors are considered congenital, their presentation in childhood is rare (the youngest reported case involved a 2-month-old infant).  The increased use of CT and MRI has resulted in an increased number of patients being diagnosed. No known genetic relationship has been determined, although familial occurrences of colloid cysts have been reported.



The etiology of this tumor is still a source of debate. In 1910, Sjovall hypothesized that colloid cysts were remnants of the paraphysis, an embryonic midline structure within the diencephalic roof immediately rostral to the telencephalic border. The cells of the paraphysis are similar to those found in colloid cysts, (ie, low columnar epithelial cells without cilia or blepharoplasts). These cysts were called paraphysial cysts for 50 years; however, several reports have been written about colloid cysts found in other locations, including the posterior third ventricle, the fourth ventricle, and the septum. Rare locations in the frontal lobe,[16] cerebellum, and pontomesencephalon have also been described. The origin of these cysts continues to be uncertain. Diencephalic ependyma, invagination of neuroepithelium of the ventricle, or the respiratory epithelium of endodermal origin are other etiologic possibilities.



One leading theory is that colloid cysts form when ectopic endodermal elements migrate into the velum interpositum during central nervous system embryonic development. The fact that they are rarely seen in children indicates that they must enlarge with time. The cyst wall is lined with a mixed array of epithelial and goblet cells secreting proteinaceous mucinous fluid and may be responsible for the increase in size of the cyst. In addition, cyst cavities may be filled with blood degradation products such as cholesterol crystals.



Colloid cysts are often found incidentally, but when symptomatic, they present with obstructive hydrocephalus and paroxysmal headaches. These headaches are typically worse in the morning and may be exacerbated by leaning the head forward. Other symptoms are gait disturbances, short-term memory loss, nausea, vomiting, and behavioral changes.[15] Sudden weakness in the lower limbs associated with falls and without loss of consciousness (drop attacks) have been reported. Additionally, symptoms similar to normal-pressure hydrocephalus (eg, dementia, gait disturbance, urinary incontinence) have been associated with the presentation of colloid cysts.

In a study of 155 patients with newly diagnosed colloid cysts, Pollock et al described the following 4 factors associated with cyst-related symptoms[17] :

  • Younger patient age (44 y vs 57 y)
  • Cyst size (13 mm vs 8 mm)
  • Ventricular dilation (83% vs 31%)
  • Increased cyst signal on T2-weighted MRI (44% vs 8%)

The most significant variable of these was ventriculomegaly. For patients with enlarged ventricles, patient age (≤50 y vs >50 y) was the most important variable because patients aged 50 years or younger with enlarged ventricles were not affected by cyst size.

On rare occasions, a colloid cyst may obstruct the foramen of Monro completely and irreversibly, resulting in sudden loss of consciousness and, if patients are not treated, coma and subsequent death due to herniation. An alternative theory suggests that sudden death in patients with colloid cysts may be related to acute neurogenic cardiac dysfunction (secondary to the acute hydrocephalus) and subsequent cardiac arrest rather than herniation. The risk of sudden death remains difficult to predict. The presence of symptoms may be usefu,l as one study found that 8% of asymptomatic patients with a colloid cyst of the third ventricle eventually became symptomatic,[17] whereas a different study found 34% of symptomatic patients presented to a hospital with acute deterioration and in some cases sudden death.[18]

Cyst size and extent of ventricular dilatation do not seem to predict for acute deterioration.[19] In a study of 163 patients diagnosed with a colloid cyst of the third ventricle, Beaumont et al demontrated a strong correlation between the diameter of the cyst and the obstructive hydrocephalus. A similar correlation was also demostrated in this study between the hypersignal on FLAIR images of the cyst and the obstructive hydrocephalus.[14]



The most common indication for surgery is hydrocephalus associated with a colloid cyst. This usually occurs in the setting of a large cyst that obstructs the foramen of Monro. A more difficult clinical situation occurs when patients present with few or no symptoms and have small colloid cysts and large ventricles. In many cases, these patients may be managed conservatively and observed with serial MRIs, but they should be counseled about the potential symptoms of hydrocephalus. Lastly, patients who have small cysts and normal-sized ventricles are not likely to deteriorate and do not need surgery.

Sudden death associated with colloid cysts has been reported, but the risk of sudden death does not seem to correlate with tumor size, degree of ventricular dilatation, or duration of symptoms. Fortunately, the incidence of sudden death appears to be low; therefore, prevention of sudden death should not be used as an indication for surgery in asymptomatic patients with small cysts and no hydrocephalus.


Relevant Anatomy

Colloid cysts usually arise in the anterior portion of the third ventricle between the fornices. The cysts are attached to the roof of the third ventricle and frequently to the choroid plexus. Usually, the cysts are immediately dorsal to the foramen of Monro. These cysts have also been reported to frequently arise in the septum pellucidum, the fourth ventricle, and the sella turcica.



If patients are too ill to tolerate surgical resection, then cerebrospinal fluid (CSF) diversion, often requiring bilateral shunts, may be considered. This situation is suboptimal because sudden death has been reported in the absence of acute obstructive hydrocephalus.

Contributor Information and Disclosures

Lawrence S Chin, MD, FACS Robert B and Molly G King Endowed Professor and Chair, Department of Neurosurgery, State University of New York Upstate Medical University

Lawrence S Chin, MD, FACS is a member of the following medical societies: Alpha Omega Alpha, American Association for the Advancement of Science, American Association for Cancer Research, Children's Oncology Group, Society for Neuro-Oncology, Congress of Neurological Surgeons, American Association of Neurological Surgeons, American College of Surgeons, Phi Beta Kappa

Disclosure: Nothing to disclose.


Mayur Jayarao, MD, MSc Resident Physician, Department of Neurosurgery, University of Missouri-Columbia School of Medicine

Mayur Jayarao, MD, MSc is a member of the following medical societies: American Association of Neurological Surgeons, American College of Surgeons, American Medical Association, Congress of Neurological Surgeons

Disclosure: Nothing to disclose.

Gentian Toshkezi, MD Resident Physician, Department of Neurosurgery, State University of New York Upstate Medical Center

Gentian Toshkezi, MD is a member of the following medical societies: Congress of Neurological Surgeons, American Academy of Neurological Surgery

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Ryszard M Pluta, MD, PhD Associate Professor, Neurosurgical Department Medical Research Center, Polish Academy of Sciences, Poland; Clinical Staff Scientist, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health (NIH); Fishbein Fellow, JAMA

Ryszard M Pluta, MD, PhD is a member of the following medical societies: Polish Society of Neurosurgeons, Congress of Neurological Surgeons

Disclosure: Nothing to disclose.

Chief Editor

Brian H Kopell, MD Associate Professor, Department of Neurosurgery, Icahn School of Medicine at Mount Sinai

Brian H Kopell, MD is a member of the following medical societies: Alpha Omega Alpha, American Association of Neurological Surgeons, International Parkinson and Movement Disorder Society, Congress of Neurological Surgeons, American Society for Stereotactic and Functional Neurosurgery, North American Neuromodulation Society

Disclosure: Received consulting fee from Medtronic for consulting; Received consulting fee from St Jude Neuromodulation for consulting; Received consulting fee from MRI Interventions for consulting.

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Axial CT scan that shows a colloid cyst with associated hydrocephalus.
Coronal MRI shows a colloid cyst in the roof of the third ventricle. The patient has mild hydrocephalus.
Intraoperative photograph through the operating microscope shows a colloid cyst in the Monro foramen. Choroid plexus is observed overlying the cyst, and the thalamostriate vein is along the inferior border.
Intraoperative photograph that shows removal of the cyst, leaving a dilated Monro foramen. The third ventricle can be seen through the opening.
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