Neuro-ophthalmic manifestations of Colloid Brain Cysts
Colloid cysts (CC) are rare benign intraventricular tumors of neuroectodermal origin that most commonly arise at or near the foramen of Monro at the anterior aspect of the third ventricle. This typical location for CC creates a risk of blockage of the flow of cerebrospinal fluid (CSF) which can lead to hydrocephalus. If the hydrocephalus is severe enough, this can lead to loss of consciousness or even death.
The precise pathogenesis for CC remains debatable but one hypothesis suggests that this cyst from the abnormal infolding of primitive neuroepithelium, specifically the paraphysis elements. While most commonly located in the third ventricle of the brain at the level of the foramen of Monro, CC in rare instances have also been seen in the frontal lobe, cerebellum, and pontomesencephalon.
CC occur in up to 3 in one million people. They account for 0.5%-3% of primary brain tumors and 15%-20% of intraventricular masses. A majority of cases are identified in patients between their third and seventh decades of life, although CC may present at any age. Although familial occurrences have been reported, there is no known genetic relationship.
Due to their delicate position at or near the foramen of Monro, CC can produce potentially life-threatening acute hydrocephalus. As these slow-growing cysts enlarge, they can obstruct CSF flow through the foramen of Monro resulting in increased intracranial pressure (ICP). This increased ICP can manifest as headaches, vision disturbances from papilledema, diplopia (from sixth nerve palsy or dorsal midbrain syndrome), memory and concentration difficulties, coma, and even death due to herniation or cardiac dysfunction. CC can also cause intermittent obstructive hydrocephalus due to the ball valve acting as a pendulum which causes intermittent symptoms.
Most CC are asymptomatic and found incidentally on imaging for evaluation of other conditions. Symptomatic CC are due to non-communicating hydrocephalus which can cause headaches, nausea, vomiting, lethargy, coma, and even death. Slowly progressive hydrocephalus is more likely to cause urinary incontinence, altered mentation, memory deficits, difficulty ambulating, and falls.
Physical exam is normal in cases of asymptomatic CC. If the patient has symptomatic hydrocephalus, physical exam findings may include ataxia, hyperreflexia, lethargy, and the ocular findings listed below. Chronic hydrocephalus can result in papilledema and frontal release signs.
Symptomatic hydrocephalus may result in blurry vision, loss of vision, diplopia, oscillopsia, or vertical gaze palsy due to involvement of the posterior commissure. Acute or chronic intracranial hypertension can lead to papilledema and secondary visual loss. The CC can mimic the presentation of idiopathic intracranial hypertension (IIH) or produce fulminant increased ICP that may require urgent evaluation and management. The ophthalmologist therefore should be aware of these neuro-ophthalmic presentations for CC.
Patients with suspected CC should be evaluated clinically for symptoms and signs of acute hydrocephalus. Urgent evaluation and monitoring for neurologic deterioration may be necessary. Neuroimaging is typically diagnostic for CC.
In a retrospective study of 163 CC, 60% were discovered incidentally during evaluation of the brain for other neurological conditions. Magnetic resonance imaging (MRI) or computer topography (CT) scans of the brain are typically used to diagnose CC. MRI is the optimal diagnostic modality and is superior to CT in fully characterizing the lesion but acute presentations may require an urgent initial cranial CT to evaluate for acute hydrocephalus.
On CT scan, CC appear as unilocular well-demarcated round and typically hyperdense lesions. They are most often seen at the roof of the third ventricle and calcification is uncommon. CC have variable imaging characteristics on MRI depending on their composition. Approximately 50% of the cysts present as a circular hyperintensity on T1 imaging. With administration of gadolinium, CC do not generally enhance (but stretched septal veins may enhance). Most CC are hypointense on T2 imaging but the signal intensity (SI) is variable. The low T2/T2* SI is presumed related to thick "motor oil" consistency fluid within the CC but some CC have a central low T2 SI and high peripheral T2 SI and others are homogeneously high SI on T2. Likewise on fluid attenuation inversion recovery (FLAIR) MRI sequences, CC with low SI on T2 may appear similar to attenuated CSF on FLAIR which may make the CC difficult to appreciate.
CC are epithelium-lined cysts filled with gelatinous material which commonly contain as mucin, hemosiderin, cholesterol, and various ions. Microscopically, the cell wall of these cysts is unicellular and made up of columnar epithelium. Mucin stains for cyst contents stain positive for periodic acid Schiff (PAS), while the epithelial wall stains positive for keratin and epithelial membrane antigen (EMA).
The differential diagnosis for a CC is limited but other cystic lesions may present in the third ventricle of the brain. This short list includes subependymal giant cell tumors with associated tuberous sclerosis complexes and subependymomas. Other lesions that may resemble CC on imaging include:
● Giant cell astrocytoma
● Pilocytic astrocytoma
● Pituitary tumor
In cases of acute and life-threatening hydrocephalus, airway, breathing, and circulation should be ensured. After this, an external ventricular drain can be placed to relieve the hydrocephalus.
The best treatment for symptomatic CC is surgical removal. Current treatment options include craniotomy with excision, endoscopic removal, and stereotactic aspiration. Transcallosal and transcortical routes can be used to remove CC. The transcallosal approach involves splitting the two frontal hemispheres of the brain to create a surgical corridor through the rostral end of the genu of the corpus callosum to allow for access to the CC. The transcortical approach involves creating a surgical corridor through the brain cortex itself. This occurs most commonly through the right frontal, middle gyrus to allow for access to the lateral ventricle from where the colloid cyst can be removed. This method may have a higher surgical risk but lower recurrence rate. Endoscopic access to the lateral ventricle may have less risk than open craniotomy but may have a slightly higher reoperation and recurrence rate (10). Stereotactic aspiration can decrease the size and reduce symptoms in some cases, but the CC can recur.
Asymptomatic colloid cysts do not typically warrant treatment and CC less than 1 cm in size and are more centrally located in the third ventricle are less likely to be obstructive. Asymptomatic colloid cysts should be monitored over time with serial neuroimaging. Patients should be aware of symptomology of increased intracranial pressure as there have been reported cases of colloid cysts which were followed clinically but resulted in death.
The prognosis of CC is good following complete surgical resection. Asymptomatic and small lesions usually remain stable but sudden death has been reported in cases of acute obstructive hydrocephalus and thus neurosurgical consultation is advised.
Clinicians should be aware of the ophthalmic presentations of colloid cysts including loss of vision (papilledema) and double vision (sixth nerve palsy or dorsal midbrain syndrome). Neuroimaging studies show typical features for CC and the differential diagnosis is usually limited. The ophthalmologist’s role is to determine if symptoms or signs of increased intracranial pressure are present. CC can cause obstructive hydrocephalus and sudden death and therefore neurosurgical consultation should be considered even in asymptomatic cases. Treatment of the acute and chronic papilledema may require urgent evaluation and surgical management.
- ↑ Ahmed SI, Javed G, Laghari AA, et al. Third Ventricular Tumors: A Comprehensive Literature Review. Cureus. 2018;10(10):e3417. Published 2018 Oct 5. doi:10.7759/cureus.3417
- ↑ 2.0 2.1 Waggenspack GA, Guinto FC Jr. MR and CT of masses of the anterosuperior third ventricle. AJR Am J Roentgenol. 1989 Mar;152(3):609-14. doi: 10.2214/ajr.152.3.609. PMID: 2783815.
- ↑ Barbagallo GM, Raudino G, Visocchi M, Maione M, Certo F. Out-of-third ventricle colloid cysts: review of the literature on pathophysiology, diagnosis and treatment of an uncommon condition, with a focus on headache. J Neurosurg Sci. 2019 Jun;63(3):330-336.
- ↑ Osborn AG, Preece MT. Intracranial cysts: radiologic-pathologic correlation and imaging approach. Radiology. 2006 Jun;239(3):650-64. doi: 10.1148/radiol.2393050823. PMID: 16714456.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Tenny S, Thorell W. Colloid Brain Cyst. [Updated 2021 Jun 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470314/
- ↑ Stoodley, M.A., Nguyen, T.P. and Robbins, P. (1999), Familial Fatal and Near-Fatal Third Ventricle Colloid Cysts. Aust. N.Z. J. Surg., 69: 733-736. https://doi-org.ezproxy.lib.utexas.edu/10.1046/j.1440-1622.1999.01676.x
- ↑ 7.0 7.1 7.2 7.3 Beaumont TL, Limbrick DD Jr, Rich KM, Wippold FJ 2nd, Dacey RG Jr. Natural history of colloid cysts of the third ventricle. J Neurosurg. 2016 Dec;125(6):1420-1430. doi: 10.3171/2015.11.JNS151396. Epub 2016 Mar 11. PMID: 26967781.
- ↑ Glastonbury CM, Osborn AG, Salzman KL. Masses and Malformations of the Third Ventricle: Normal Anatomic Relationships and Differential Diagnoses. RadioGraphics. 2011;31(7):1889-1905. doi:10.1148/rg.317115083
- ↑ Muralidharan R. External ventricular drains: Management and complications. Surg Neurol Int. 2015;6(Suppl 6):S271-S274. Published 2015 May 25. doi:10.4103/2152-7806.157620
- ↑ 10.0 10.1 Yadav YR, Yadav N, Parihar V, Kher Y, Ratre S. Management of colloid cyst of third ventricle. Turk Neurosurg. 2015;25(3):362-71. doi: 10.5137/1019-5149.JTN.11086-14.1. PMID: 26037175.