Case Analysis - Colloid Cyst

Male, 25 years old

Complaints: headache progressively worsening for 2 months

Admission for CT and MRI

Clinical diagnosis: intracranial mass lesions

Results of imaging examinations

CT: a circular slightly dense opacity in front of the third ventricle, calcification visible in the right posterior, clear margins, bilateral ventricular dilatation
.

MRI: a class of circular abnormal signals were seen in the anterior part of the third ventricle near the Marsh foramen, T1WI showed high signal, T2WI showed low signal, and no obvious enhancement was seen on enhanced scanning; Bilateral ventricular dilation, with midline structure centered
.

discuss

Colloidal cyst, also known as mitochondrial cyst, interventricular foramen cyst or paracranial cyst, originates from neuroepithelial tissue and is a rare intracranial lesion, accounting for 0.
14%~2%
of intracranial tumors.

Russe II and Rubincein report accounting for 2%
of confirmed intracranial tumors in cadavers.
Men are twice as likely as
women.

Colloidal cysts are generally located anterior to the third ventricle, and are individually longer than the lateral ventricle, extracerebral area, sellar area, and hyaline septum
.
It is generally believed to be formed by mutation of the primitive neural
epithelium during the formation of the third ventricular ependym, choroid plexus, and paracrastige bodies.

pathology

Colloidal cyst is spherical or oval, 0.
3~4.
0cm in size, smooth, thin and complete cyst wall, dense mucus jelly sample with yellow or grayish white contents, which is a viscous liquid secreted by the membrane columnar cells of the cyst wall; It contains thick and high-protein ingredients, and also contains a large number of other ingredients, such as old bleeding, hemosiderin, cholesterol crystals and paramagnetic substances sodium, calcium, magnesium, iron, copper, phosphorus, aluminum, etc.
; It can also be the center of granulation, and some may have calcification and bleeding
.
Large cysts can intermittently or persistently block the interventricular foramen, causing hydrocephalus
.

Clinical manifestations

Clinical manifestations depend on cyst size and the degree of
ventricular obstruction.

Small cysts can remain asymptomatic for life and are found
only incidentally during autopsy.
Cysts are mostly located in the anterior and upper part of the third ventricle, close to the posterior interventricular foramen, and mostly attached to the ependymal or choroid plexus there, because cysts often cause obstruction of the interventricular foramen, resulting in obstructive hydrocephalus and increased intracranial pressure, so headache and vomiting are the main symptoms
.

CT findings

1.
The flat-scan cyst is round or oval, with sharp edges, located near the glenoon foramen in the anterior part of the three ventricles,

2.
2/3 of the lesions are homogeneous and high-density (45-75 Hu) around the brain parenchyma, 1/3 is isodensely shadowed surrounding brain parenchyma, and a very few cysts have low density
in the center.

3.
The high density of CT scan may be due to cyst wall-like discharge, hemosiderin and tiny calcifications
that cannot be seen on CT.

4.
After enhancement, the cyst occasionally has thin edge strengthening, but typically no strengthening and no calcification
.

MRI findings

1.
Round or oval mass in the anterior part of the third ventricle, T1WI is hyperintensive, and T2WI is also hyperintensive;

2.
Some colloidal cysts are equal signal on T1WI and low signal with equal signal capsule wall in T2WI;

3.
Non-signal calcified spots can be seen in the cyst;

4.
Obstructive hydrocephalus, bilateral ventricular enlargement, third ventricle shrinkage or unclear display;

5
.
After enhancement, the cyst can be strengthened to varying degrees.

differential diagnosis

1.
Central nervous system cell tumor: derived from the hyaline septum, connected to the transparent septum with a wide base, CT plain scan is a slightly high-density mass, which can be uneven, irregular morphology, and can be significantly enhanced after enhancement, T2, T1, etc.
or high signal
on MRI.

2.
Ependymoma: CT is characterized by irregular morphology, uneven density, accompanied by intratumor cystization and calcification, and the enhancement is strengthened
to varying degrees.
MRI is similar to CT, with uneven signals and varying degrees of strengthening
.

3.
Pituitary microadenoma: When the colloidal cyst < 10mm and is located in the saddle, the T1WI with low signal should be distinguished from the pituitary microadenoma, the former has a smoother and sharper edge and lower
signal.
If a small cyst is hyperintense at T1WI, it is more suggestive of a colloidal cyst
.

4.
Chordoma occurs on the slope of the saddle area, with uneven density and obvious bone destruction
of the skull base.

5.
The CT of aneurysms near the Willis ring is equal or high density, which is consistent with vascular enhancement after enhancement, and the flow air effect
can be seen on MRI.