Presentation
Sudden onset of headache and decreased conscious state.
Patient Data
An oval extraaxial, partially cystic mass with calcified rim appears to be centered in the pineal region and measures 31 x 20 mm. There is no convincing enhancement. The mass compresses the cerebral aqueduct, extends into the third ventricle with associated obstructive hydrocephalus.
The patient was taken to theater and a ventricular drain inserted to relieve the hydrocephalus. Following this, they were taken to the MRI scanner for more imaging.
Centered on the posterior third ventricle in the midline, inseparable from the pineal, is a 31 x 21 x 21 cystic mass with a fluid/fluid level with supernatant effect with blood product in the dependent portion, and T1 hyperintense anterior compartment. Thickened septations lie within the cyst, and do not enhance. Apart from some subtle capsule enhancement, there is no definite enhancing component.
The mass causes compression of the cerebral aqueduct-the degree of hydrocephalus has been decreased by placing a right ventricular shunt catheter since the earlier CT scan. The third ventricle anterior to the mass is distended and contains water density CSF. The vein of Galen and internal cerebral veins are displaced superiorly.
No other intracranial mass lesions, or abnormal enhancement is shown.
The cystic pineal region mass (yellow) compresses the tectum of the midbrain (green) and displaces the internal cerebral veins (blue) which are located above it. Inside the mass a fluid fluid level is present with CT hypderdense and T2 hypointense component layering dependently (red) representing the red blood cells / hematocrit above which floats the serum (orange). On T2 weighted images septations are seen to cross the mass.
The patient was taken back to the operating room, and via a posterior fossa craniotomy the cyst was removed.
MACROSCOPIC DESCRIPTION: An opened cyst 14 mm in diameter. The wall is composed of a thin dark fawn membrane and has a roughened inner surface. Separate fragment of soft fawn tissue up to 3 mm included.
MICROSCOPIC DESCRIPTION: The sections include tissue from normal pineal gland with glandular structures and rosettes divided by thin connective tissue membranes and the presence of corpora arenacea are noted. The cyst noted macroscopically appears to be lined by glial cells and compressed pineal gland parenchyma. There are scattered Rosenthal fibers and refractile brown pigment consistent with hemosiderin. The topoisomerase index is 1%. IDH-1 immunostain is negative.
FINAL DIAGNOSIS: Pineal cyst
Case Discussion
Although pineal cysts are common and in the majority of cases asymptomatic, large cysts can cause compression of the aqueduct and result in hydrocephalus. More rarely still, acute hemorrhage can cause sudden expansion of the cyst with acute obstructive hydrocephalus.
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