COLLOID CYST OF THE THIRD VENTRICLE: REPORT OF TWO CASES N. EZZAAIRI, M. MAATOUK, M.A. JELLALI, W.MNARI, A. ZRIG, W. HARZALLAH, R.SALEM, M. GOLLI Service.

COLLOID CYST OF THE THIRD VENTRICLE: REPORT OF TWO

CASESN. EZZAAIRI, M. MAATOUK, M.A. JELLALI, W.MNARI, A. ZRIG, W. HARZALLAH, R.SALEM, M. GOLLI

Service d’imagerie médicale, CHU Fattouma Bourguiba Monastir –TUNISIE

NR 32

Colloid cysts (CC) are relatively rare intracranial benign congenital

tumors accounting for 0.5%–1% of primary brain tumors and

15%–20% of intraventricular masses.

Colloid cysts are slowly growing non-neoplastic cysts that are

predominantly arising in the anterior region of the 3rd ventricle

(more than 99%).

They are classically presenting during the 3rd to 4th decades.

Introduction

Typically, patients are asymptomatic, although

colloid cysts may cause symptoms by obstructing

the foramen of Monro.

Both magnetic resonance imaging (MRI) and

computed tomography (CT) can be used for the

diagnosis.

Introduction

In this report, we present 2 cases of CC of the

3rd ventricle, along with the findings of

radiological imaging.

Case report

A 57-year-old man, admitted following head injury.

A unenhanced CT scan (NECT) did not demonstrate

any intracranial hemorrhage but there hyperdense

foramen of Monro mass.

Patient one

MRI confirmed the presence of a small colloid cyst at the foramen of Monro which was homogeneously hyperintense to brain on T1 WI (B). T2WI (C) shows a mixed signal mass with a focus of profound hypointensity. FLAIR sequence (D) shows the cyst does not suppress. There was no restriction in DWI (E)

A

B

C

D

E

A 48-year-old man presented to the emergency

department, with a 2 day history of frontal headache

and nausea associated with an episode of vomiting.

He was neurologically intact, with no signs of

meningism.

Patient 2

NECT shows a small, Well-

demarcated round, hyperdense

foramen of Monro mass with

obstructive hydrocephalus.

There was no enhancement

after injection.

MRI imaging shows a colloid cyst at the foramen of Monro (A). The cyst is

hyperintense on T1 WI (B) and is causing moderate hydrocephalus with

transependymal CSF flow (C). T1WI with gadolinium revealed no enhancement (D).

A

B

C

D

Colloid cyst or paraphyseal cyst is the most common tumours in

the 3rd ventricle.

It’s wedged into foramen of Monro in over 99% of cases.

Rare reports describe other locations including the leptomeninges,

cerebellum, lateral and 4th ventricles.

CC, like neurenteric and Rathke cysts, is derived from embryonic

endoderm.

Discussion

Age : 3rd to 4th decade

Rare in children

40-50% asymptomatic, discovered incidentally

The most common sign is a headache (50-60%)

Acute foramen of Monro obstruction may lead to rapid

onset hydrocephalus, herniation and death

Discussion

Prognosis is variable:

• 90% of CC are stable

• 10% can expand rapidly, causing coma and death.

• Criteria of poor prognosis are:

• Younger patients

• Larger cyst, hydrocephalus

• Iso/hypodense on NECT, often hyperintense on T2WI

Discussion

CC is a smooth, spherical, well-delineated cysts.

The content is composed of a viscous gelatinous material

(colloid) with variable viscosity.

Histologically, CC is characterized by a simple or

pseudostratified epithelial lining with interspersed goblet cells and

scattered ciliated cells.

The cyst contents is PAS positive and composed of.

It may contain necrotic leucocytes and cholesterol clefts.

Pathologic findings

Either CT or MRI may help in diagnosing a CC,

although MRI has a few advantages.

The multiplanar capabilities of MRI optimally

demonstrate the classical location of the cyst, and

typical signal intensities in the cyst help helpful in the

early and correct diagnosis of this entity.

Imaging

On NECT, approximately 2/3 of CC are slightly hyperdense. It

may occasionally be hypodense or isodense.

The density is correlated inversely with hydratation state.

Calcification or hemorrhage are rare.

After administration of iodinated contrast material, no

enhancement of the mass lesion or a thin rim of enhancement

may be present.

Imaging : CT

On T1WI, the signal of CC is correlates with cholesterol concentration:

• 2/3 are hyperintense

• 1/3 are isointense

On T2 WI, the signal is more variable:

• the majority are isointense to brain.

• ¼ are mixed “black hole” effect

On FLAIR sequence; the signal cyst is not suppressed

There are not restriction on DWI

Imaging : MRI

The imaging appearance of a colloid cyst is almost

pathognomonic.

The most common “lesion” mistaken for a colloid cyst is

CSF flow artifact (MR pseudocyst) caused by pulsatile

turbulent CSF flow around the foramen of Monro.

Multiplanar technique confirms artifact.

Differential diagnosis

Occasionally, a neurocysticus cyst may occur at the

foramen of Monro. However, multiple lesions within

parenchyma and cisterns are usually shown in

neurocysticercosis.

Neoplasms such as subependymoma or choroid plexus

papilloma that may occur at the foramen of Monro are

much less common and typically enhanced.

Differential diagnosis

Prophylactic surgery for asymptomatic CC of the 3rd ventricle

remains controversial. However, the possibility of spontaneous

rupture of these cysts should also be kept in mind.

The most common treatment consist on complete surgical

resection.

Recurrence is rare, if resection is complete

Treatement