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ESSENTIAL INFORMATION

Key Differential Diagnosis Issues
- Quadrigeminal cistern - Bounded by quadrigeminal plate, splenium, vermis, & tentorial margin - Extends between layers of 3rd ventricle tela choroidea - Contents: Caudal internal cerebral veins → vein of Galen, distal parts of quadrigeminal artery, posterior cerebral artery P4 segment, & CNIX exit - Synonyms: Cisterna quadrigeminalis, cistern of great cerebral vein, cisterna venae magnae cerebri, Bichat canal, cisternal quadrigeminalis, & superior cistern
Helpful Clues for Common Diagnoses
- Pineal Cyst - Homogeneous fluid-filled mass distinct from tectum - 55-60% slightly T1 hyperintense to CSF; incomplete FLAIR suppression; 60% rim enhancement - Cystic expansion of pineal in some female patients begins in adolescence, decreases with age - Indistinguishable from cystic pineocytoma on basis of imaging studies alone
- Germ Cell Tumors - Pineal region mass that engulfs pineal gland Ca⁺⁺ - Male predominance in pineal region - Germinoma - T1/T2 iso- or hyperintense to gray matter - Strong uniform enhancement ± CSF seeding - CT hyperdense, diffusion restriction - Teratoma - Mature tumors with Ca⁺⁺, cysts, & fat - Immature tumors with heterogeneous enhancement & predominantly soft tissue - Teratoma with somatic-type malignancy, typically sarcoma or carcinoma - Nongerminomatous germ cell tumors - Choriocarcinoma, endodermal sinus tumor, embryonal cell carcinoma, mixed germ cell tumor - Heterogeneously enhancing pineal mass - Elevation of serum β-hCG &/or α-fetal protein
- Pineal Parenchymal Tumors - Enhancing, pineal mass that explodes pineal Ca⁺⁺ - Pineoblastoma - Large heterogeneous mass, adjacent invasion - Evaluate neuraxis for leptomeningeal dissemination - ~ 35-45% of pineal parenchymal tumors - WHO grade 4 - Pineocytoma - Enhancing, circumscribed pineal mass - May mimic normal pineal gland & cyst - Compresses but does not invade adjacent structures - ~ 25% of pineal parenchymal tumors - WHO grade 1 - Pineal parenchymal tumor of intermediate differentiation - Typically larger, heterogeneous, & more aggressive than pineocytomas - Intermediate grade between blastoma & cytoma - Leptomeningeal dissemination has been described - ~ 20-45% of pineal parenchymal tumors - WHO grade 2-3 - Papillary tumor of pineal region - Rare tumors thought to arise from ependymocytes in subcommissural organ - May have T1 hyperintensity from glycopeptides - Heterogeneous enhancement, possible CSF dissemination - WHO grade 2 or 3 - Desmoplastic myxoid tumor of pineal region,SMARCB1-mutant - Rare adolescent to adult tumor, intermediate prognosis - Similar appearance to other pineal gland tumors
Helpful Clues for Less Common Diagnoses
- Cyst of Velum Interpositum - Triangular CSF space between lateral ventricles - Cavum velum interpositum common in infants, rare in adults - Large cyst inferiorly displaces internal cerebral veins - Splays & elevates fornices
- Arachnoid Cyst - Sharply demarcated extraaxial cyst that follows CSF attenuation/signal - Quadrigeminal arachnoid cysts (AC) are 3rd most common infratentorial AC - Symptoms depend on compression of brainstem, cerebellum, & aqueduct - Elevates internal cerebral veins
- Midbrain & Thalamic Neoplasms - Astrocytomas of tectal plate most common - Diffuse midline glioma, H3 K27-altered, atypical teratoid/rhabdoid tumor, CNS embryonal tumors - Tectal plate glioma - Tectal distortion or thickening by localized mass - T1 hypointense, T2 hyperintense, rare enhancement - Onset aqueductal stenosis often without brainstem signs - Indolent, often remaining stable in size for many years
- Neurocysticercosis - May involve cisterns > parenchyma > ventricles - Basal cistern cysts may be racemose or grape-like - Cysts variable in size & may contain 1- to 4-mm scolex - Cystic lesion isointense to CSF, may see discrete, eccentric scolex
- Lipoma - Well-delineated lobulated extraaxial mass with fat attenuation/intensity - 40-50% interhemispheric fissure (over corpus callosum) - Ca⁺⁺ varies from none to extensive - Fat-suppressed MR is diagnostic
- Intracranial Hypotension - Corpus callosal descent can efface quadrigeminal cistern - Sagittal image shows brain descent in 40-50% - Diffusely, intensely enhancing dura in 85% - Bilateral subdural fluid collections in 15%
Helpful Clues for Rare Diagnoses
- Epidermoid Cyst - Lobulated, irregular, CSF-like mass with fronds insinuates cistern - Incomplete FLAIR suppression; decreased diffusion - ~ 1-2% of all primary intracranial tumors - Congenital inclusion cysts; rare malignant degeneration into squamous cell CA
- Dermoid Cyst - Fat-suppression sequence or negative HU to confirm fat - Rupture → fat droplets in subarachnoid spaces with diffuse enhancement from chemical meningitis - < 0.5% of primary intracranial tumors - Rare malignant degeneration into squamous cell carcinoma
- Vein of Galen Malformation - Misnomer: Arteriovenous fistula draining into enlarged median prosencephalic vein - Dilated arteries feeding into large midline venous pouch - < 1% cerebral vascular malformations at any age - Neonatal > infant presentation most common; rare adult presentation
- Meningioma - Avidly enhancing mass, trapped pools of CSF common - Arise from posterior portion of velum interpositum, falx, or tentorium - Velum interpositum meningiomas: M = F, in both pediatric & adult populations - May be symptomatic from compression of quadrigeminal plate

References

Selected References

Images

Selected Images

Pineal Cyst Sagittal T1 C+ MR shows a nonenhancing cyst in the pineal region related to a pineal cyst. These benign cysts typically require no follow-up.

Germinoma Axial b=1000 DWI shows a pineal region mass with decreased diffusion & thalamic invasion. Note the central susceptibility artifact from engulfed Ca++ . Pure germinomas are hypercellular & typically show decreased diffusion. Engulfed Ca++ favors germinoma over pineoblastoma. Germinomas are the most common pineal region mass.

Teratoma Sagittal T1 MR shows a heterogeneous mass with intrinsic T1 shortening, consistent with fat . In this infant, fat content & midline location suggest teratoma.

Pineoblastoma Sagittal T1 C+ MR shows an enhancing mass of the pineal region with mass effect on the tectal plate & midbrain with resulting hydrocephalus . Pineoblastomas often have CSF dissemination.

Pineoblastoma Axial b=1000 DWI (same patient) shows the almond-shaped mass has intense decreased diffusion, consistent with hypercellularity. Pineoblastomas are WHO grade 4 small round blue cell embryonal tumors & should be considered for any pineal region tumor with decreased diffusion.

Pineocytoma Sagittal T2 MR shows a bubbly, cystic mass of pineal gland in a patient with a headache likely from hydrocephalus. Note lack of flow void through cerebral aqueduct from mass effect on tectal plate, a WHO grade 1 pineocytoma at resection.

Pineal Parenchymal Tumor of Intermediate Differentiation Sagittal T1 C+ MR shows a lobular enhancing mass in the pineal region causing obstructive hydrocephalus . This was a pineal parenchymal tumor of intermediate differentiation at resection.

Papillary Tumor of Pineal Region Sagittal T2 MR shows a bubbly cystic tumor in the pineal region causing mass effect on the tectum. A papillary tumor of the pineal region may show greater cystic changes than other pineal parenchymal tumors. Associated hydrocephalus is common. These rare tumors may be WHO grade 2 or 3.

Cyst of Velum Interpositum Axial T2 MR shows a cystic structure between the leaves of the velum interpositum . Note there is a lack of extension anteriorly to involve the septum pellucidum.

Cyst of Velum Interpositum Sagittal T1 C+ MR shows the nonenhancing cyst that displaces the internal cerebral veins inferiorly . The majority of cysts or masses in the pineal region will typically splay or elevate the internal cerebral veins.

Arachnoid Cyst Axial FLAIR MR demonstrates a FLAIR- suppressed cyst in the pineal region . This follows CSF on all sequences & is related to an arachnoid cyst.

Tectal Plate Glioma Axial FLAIR MR shows a T2-hyperintense mass in the tectal plate & dorsal brainstem . This did not demonstrate enhancement (not shown) & causes aqueductal obstruction leading to hydrocephalus . Tectal gliomas are commonly low-grade tumors. However, a variety of of tumor types may involve the tectal plate.

Lipoma Axial T1 MR shows an intrinsic T1-hyperintense homogeneous mass along the tectal plate . This is consistent with lipoma. Intracranially, lipomas typically occur midline from maldifferentiation of the embryologic meninx primitiva & can be associated malformations.

Epidermoid Cyst Axial b=1000 DWI shows a hyperintense lobular mass in the pineal region & 3rd ventricle. This had cyst-like T1 & T2 signal with incomplete FLAIR suppression & no enhancement (not shown), classic for epidermoid cyst.

Vein of Galen Malformation Sagittal T2 MR shows a large flow void from enlargement of the median prosencephalic vein . Note the enlargement of the pericallosal arteries & vertebrobasilar arteries , which fistulize into the aneurysmal vein. This causes steal phenomenon & high-output cardiac failure with resulting cerebral atrophy.

Meningioma Axial T1 C+ MR shows a homogeneous enhancing mass in the pineal region. Note the border with the posterior falx , suggesting a broad dural base, typical of meningioma.

Additional Images

Pineal Cyst Sagittal T1 C+ MR shows how difficult pineal cysts can be to distinguish from pineocytoma. Pineal cysts can display a spectrum of enhancement from thin to thick rim to nodular.

Pineal Cyst Axial FLAIR MR shows the classic finding of a presumed pineal cyst that does not suppress & is moderately hyperintense.

Germinoma Axial T1 C+ MR demonstrates that germinomas can present with synchronous masses. These will typically be in the pineal & suprasellar locations.

Germinoma Sagittal T1 C+ MR shows an enhancing germinoma . Note compression of the tectal plate and CSF tumor seeding .

Pineal Parenchymal Tumors Coronal T1 C+ MR shows a typical MR case of small, cystic, centrally & peripherally enhancing pineocytoma.

Pineal Parenchymal Tumors Axial CECT shows a typical CT case of a pineocytoma with "exploded" preexisting Ca++ . Also note the typical lack of significant mass effect.

Cyst of Velum Interpositum Axial CECT shows a CSF collection between the fornices , splaying the internal cerebral veins & choroid plexus inferolaterally . Note the septum pellucidum is intact.

Cyst of Velum Interpositum Axial T2WI MR demonstrates a classic CVI appearance: Triangular-shaped CSF collection between the fornices .

Arachnoid Cyst Axial FLAIR MR shows a quadrigeminal cistern arachnoid cyst which followed CSF on all sequences & shows complete FLAIR suppression .

Arachnoid Cyst Sagittal T1WI MR shows an arachnoid cyst extending posteroinferiorly from the quadrigeminal cistern, compressing the superior vermis inferiorly .

Midbrain & Thalamic Neoplasms Sagittal T2WI MR demonstrates a typical tectal plate low-grade astrocytoma as a predominantly homogeneous, slightly hyperintense mass involving the tectal plate proper .

Neurocysticercosis Axial T2WI FS MR shows multiple cysticercosis cysts in the quadrigeminal cistern , atrium right lateral ventricle . (Courtesy E. Bravo, MD.)

Neurocysticercosis Axial T2WI MR shows a typical case of racemose (grape-like) cisternal neurocysticercosis within the quadrigeminal plate & ambient cisterns .

Lipoma Axial T1WI MR reveals a fat-intensity lesion within the quadrigeminal cistern exerting mass effect upon the quadrigeminal plate (R > L). Fat suppression (not shown) confirmed lipoma.

Lipoma Axial T1 C+ FS MR confirms the presence of a lipoma that was T1 hyperintense (not shown).

Intracranial Hypotension Sagittal T1 C+ MR in a patient with intracranial hypotension shows cisternal effacement by the splenium impacting the internal cerebral veins & quadrigeminal plate . Note loss of the suprasellar cistern & dural enhancement .

Epidermoid Cyst Axial T2WI MR shows a T2 hyperintense lobulated mass centered in ambient cistern extending into suprasellar & quadrigeminal cisterns displacing the quadrigeminal plate .

Epidermoid Cyst Coronal T1WI MR reveals a small T1 hypointense epidermoid within the quadrigeminal cistern with mild mass effect displacing bilateral cerebral & cerebellar hemispheres.

Dermoid Cyst Sagittal T1WI MR shows a ruptured dermoid with intrinsic mixed signal , lipid droplets present throughout the subarachnoid spaces , & hydrocephalus from chemical meningitis.

Dermoid Cyst Axial CECT demonstrates a low-density ruptured dermoid in the pineal region with fat droplets in subarachnoid spaces . Note ventricular shunt placed for chemical meningitis.

Vein of Galen Malformation Lateral angiography shows an enlarged vein of Galen, falcine sinus, & augmented flow into superior sagittal sinus , supplied by enlarged choroidal & thalamoperforating arteries .

Vein of Galen Malformation Sagittal T1WI MR shows a large well-delineated area of signal loss behind the 3rd ventricle . Note phase artifact from high flow & large persistent primitive falcine sinus .

Meningioma Sagittal T2WI FS MR shows an isointense mass with flow voids . Visualization of a normal pineal gland & elevation of midbrain tectum helps exclude pineal tumors from the differential diagnosis.

Meningioma Sagittal T1 C+ MR reveals a small, rounded, avidly enhancing, falcotentorial meningioma without quadrigeminal plate abutment.

Pineal Cyst Axial T2 MR shows a cystic lesion in the expected location of the pineal gland. This large pineal cyst is causing obstruction of the distal 3rd ventricle & aqueduct with hydrocephalus .

Germinoma Sagittal T1 C+ FS MR shows a lobular enhancing mass in the pineal region. The central hypointensity is consistent with an engulfed pineal calcification consistent with germ cell tumors. Compared with other germ cell tumors, germinomas are typically homogeneous with rapid response to chemotherapy.

Teratoma Axial T1 C+ MR in an infant shows a lobular heterogeneously enhancing tumor in the pineal region causing obstructive hydrocephalus . This was a mature teratoma at resection.

Nongerminomatous Germ Cell Tumors Sagittal T1 C+ FS MR shows a heterogeneous enhancing mass in the pineal region with a central hypointensity from an engulfed pineal Ca++. There is a large lobular enhancing lesion in the 4th ventricle from leptomeningeal dissemination of this mixed germ cell tumor.

Pineoblastoma Axial NECT shows an isodense pineal mass with eccentric pineal Ca++ causing hydrocephalus. Pineoblastomas & other pineal parenchymal tumors typically explode calcifications. Germ cell tumor arises from germ cell rests outside of the pineal gland & engulfs Ca++.

Pineocytoma Sagittal T1 C+ MR shows a homogeneous enhancing mass in the pineal region with mass effect on the tectal plate. This was a low-grade pineocytoma at resection.

Pineal Parenchymal Tumor of Intermediate Differentiation Axial T1 C+ FS shows an oblong pineal tumor, which causes obstructive hydrocephalus. Pineal parenchymal tumors of intermediate differentiation are WHO grade 2 tumors in between pineocytoma & pineoblastoma.

Cyst of Velum Interpositum Sagittal T1 MR shows a cystic mass causing anterior displacement of the fornix & downward displacement of the tectal plate & internal cerebral veins . Note the pineal parenchyma posterior to the cyst . This is an arachnoid cyst within a cavum velum interpositum.

Arachnoid Cyst Axial T2 FS MR shows a cyst in the pineal region causing mass effect on the midbrain with resulting hydrocephalus. This cyst was inferior to the pineal gland (not shown).

Tectal Plate Glioma Axial FLAIR MR shows a hyperintense mass arising from the tectal plate . This is consistent with a tectal plate glioma. These are low-grade astrocytomas, which typically grow very slowly. Hydrocephalus from aqueductal stenosis is typically managed with shunting. Note the artifact from a shunt reservoir .

Lipoma Axial T1 MR shows a T1 hyperintense mass associated with the quadrigeminal plate. This mass showed signal loss on a fat saturation sequence (not shown) consistent with lipoma.

Meningioma Sagittal T1 C+ MR shows a homogeneous enhancing mass arising below the pineal gland . Note the broad dural base with the tentorium & inferior displacement of the cerebellum from an extraaxial mass consistent with meningioma.

Epidermoid Cyst Axial DWI shows a mass with central decreased diffusion arising from the pineal region & causing mass effect & hydrocephalus. On T1- & T2-weighted images, this approximated the appearance of a cyst typical for epidermoids. Incomplete FLAIR suppression is also typical.

Vein of Galen Malformation Sagittal T1 C+ MR shows a heterogeneous mass in the pineal region with extension along the straight sinus to a dilated torcula . This child has a history of vein of Galen malformation treated with coiling, which causes the internal hypointense signal.

Neurocysticercosis Sagittal T1 C+ MR shows a cystic lesion below the pineal gland with faint wall enhancement. Another ring enhancing cyst with central enhancement is noted between the occipital lobes consistent with the colloidal vesicular phase of neurocysticercosis.

Dermoid Cyst Sagittal T1 MR shows a heterogeneous cystic lesion with internal T1 hyperintensity . In addition, there are droplets of T1 hyperintensity along the adjacent leptomeninges consistent with rupture of a dermoid cyst.

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ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Helpful Clues for Common Diagnoses

Helpful Clues for Less Common Diagnoses

Helpful Clues for Rare Diagnoses