statdx/docs_md/articles/prepontine-cistern-mass_e0f71196-85c7-411c-9c71-e2606b2ee52f.md

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Prepontine Cistern Mass	e0f71196-85c7-411c-9c71-e2606b2ee52f	key value 26ebc2e8-e4f7-40ee-8f5c-d23fe383e15c Yoshimi Anzai, MD, MPH key value 83f867a5-a183-4396-82ea-384015da4d2f Gregory L. Katzman, MD, MBA	name slug treeNodeId Head and Neck head-and-neck ed24ed8c-5d57-4629-879b-447b82d2973d name slug treeNodeId Differential Diagnosis differential-diagnosis 40d68862-8975-4dde-ac2b-ebc43ab0fb5c name slug treeNodeId CPA-IAC and Posterior Fossa cpa-iac-and-posterior-fossa c590eedb-4a3b-4158-a04f-ad880564c992 name slug treeNodeId Anatomically Based Differentials anatomically-based-differentials debfb06c-8656-4f5d-92c1-eaa468185d78 name slug treeNodeId Prepontine Cistern Mass prepontine-cistern-mass null	Head and Neck	8526aadd-9d1f-4f3f-8b6a-cab3c86d8196	39	08/02/18	Prepontine Cistern Mass	Head and Neck, Differential Diagnosis, CPA-IAC and Posterior Fossa, Anatomically Based Differentials, Prepontine Cistern Mass	Prepontine Cistern Mass | STATdx	Prepontine Cistern Mass	DDX	true	Head and Neck Differential Diagnosis CPA-IAC and Posterior Fossa Anatomically Based Differentials Prepontine Cistern Mass

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title: "Prepontine Cistern Mass" docid: "e0f71196-85c7-411c-9c71-e2606b2ee52f" authors:

• key: "26ebc2e8-e4f7-40ee-8f5c-d23fe383e15c" value: "Yoshimi Anzai, MD, MPH"
• key: "83f867a5-a183-4396-82ea-384015da4d2f" value: "Gregory L. Katzman, MD, MBA" breadcrumbs:
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• name: "CPA-IAC and Posterior Fossa" slug: "cpa-iac-and-posterior-fossa" treeNodeId: "c590eedb-4a3b-4158-a04f-ad880564c992"
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• name: "Prepontine Cistern Mass" slug: "prepontine-cistern-mass" treeNodeId: null category: "Head and Neck" documentVersionId: "8526aadd-9d1f-4f3f-8b6a-cab3c86d8196" imageCount: 39 lastUpdated: "08/02/18" pageDescription: "Prepontine Cistern Mass" pageKeywords: "Head and Neck, Differential Diagnosis, CPA-IAC and Posterior Fossa, Anatomically Based Differentials, Prepontine Cistern Mass" pageTitle: "Prepontine Cistern Mass | STATdx" enhancedTitle: "Prepontine Cistern Mass" type: "DDX" references: true breadcrumbs:
• "Head and Neck"
• "Differential Diagnosis"
• "CPA-IAC and Posterior Fossa"
• "Anatomically Based Differentials"
• "Prepontine Cistern Mass"

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ESSENTIAL INFORMATION

• Key Differential Diagnosis Issues

  • Anatomy - Extensive CSF space along ventral & lateral pons, dorsal to clivus (a.k.a. pontine cistern) - Bounded superiorly by interpeduncular cistern, inferiorly by subarachnoid space of spinal cord, & continuous about medulla with cerebellomedullary cistern
  • Many abnormalities, often from transspatial processes

• Helpful Clues for Common Diagnoses

  • CSF Flow Artifact - MR artifacts divided into 2 categories: TOF effects & turbulent flow - Worsens with thinner slices, longer TE, & imaging perpendicular to flow - Assess real vs. artifact in other planes & sequences - Minimize TOF losses: Use short TE, image parallel to flow, acquire thicker slices - Use 3D sequence in place of 2D - Typically most pronounced on axial FLAIR - Confirm artifact on T1 & T2 or other planes
  • Dolichoectasia (Vertebrobasilar) - Older patients - Look for ASVD in other vessels - Ectasia often extends into branches - May have significant mass effect on brainstem & cisternal cranial nerves
  • Fusiform Aneurysm, ASVD - Long segment fusiform arterial dilatation - Involves long nonbranching segments - Calcifications common - Lumen enhances strongly, clot does not
  • Meningioma - Clival region dural-based enhancing mass - Infratentorial (8-10%): CPA most common - Retroclival meningioma - Best seen on sagittal T1 C+ FS MR - Causes cranial neuropathies or ataxia
  • Metastases, Skull & Meningeal - Enhancing lesion(s) with skull/meningeal destruction/infiltration - Skull involvement causes low marrow signal on T1 MR & enhancement on T1 C+ MR - Skull involvement can spread to adjacent dura - Metastases may also be dural/meningeal only - DWI (mildly ↑ signal) may ↑ conspicuity of calvarial metastases - Manifestations: May cause smooth linear thickening or nodular, fungating masses - Image entire neuraxis

• Helpful Clues for Less Common Diagnoses

  • Epidermoid Cyst - Usually extends medially from CPA cistern - Lobulated, irregular, insinuating CSF-like mass - Doesn't completely suppress on FLAIR; restricts on DWI - Cranial nerve involvement not infrequent
  • Chiari 2 ("Creeping Cerebellum**"****)** - Small posterior fossa with low torcular Herophili - Cerebellar hemispheres/tonsils herniate anteriorly → "creeping" cerebellum - Pons, cranial nerve roots often elongated - Fusion & inferior displacement of superior & inferior colliculi: "Tectal beaking"
  • Exophytic Brainstem Glioma, Pediatric - Nonenhancing mass markedly expanding pons - May engulf basilar artery - Infiltrative have poor survival - Diffuse intrinsic brain stem glioma is now called diffuse midline glioma under 2016 WHO classification; H3, K23M mutant - Focal glioma uncommon, better prognosis
  • Pituitary Macroadenoma (Giant) - No distinct pituitary gland is visible - Bone CT variable; may be benign appearing or erosive - Heterogeneous contrast enhancement - Dural tail may mimic meningioma - Typically extends to suprasellar cistern, though occasionally extends posteriorly to prepontine cistern
  • Neurocysticercosis - Cisterns > parenchyma > ventricles - MR best modality; most isointense to CSF - Appearance varies depending on stage - Basal cistern cysts may be racemose - Lobulated cisternal cysts, usually no scolex - Cysts variable, typically 5-20 mm with 1-4 mm scolex - Scolex is small enhancing soft tissue "dot" - Colloidal vesicular stage - Result from implantation of cestode Taenia solium(pork tapeworm) in human host - 3D MR sequences optimize detection
  • Intracranial Hypotension - Sagittal shows brain descent in 40-50% - Pons may be compressed against clivus - Diffusely, intensely enhancing dura in 85% - Bilateral subdural fluid collections in 15%

• Helpful Clues for Rare Diagnoses

  • Inflammatory Mass - Tuberculosis - Basilar meningitis, pulmonary TB - Thick basilar exudate ± tuberculomas/abscesses - Basilar meningitis may cause infarction due to vascular wall invasion - Fungal diseases - Blastomycosis, coccidiomycosis, histoplasmosis, candidiasis - Meningeal enhancement, multiple enhancing brain lesions - Frequently ring-enhancing - Neurosarcoid - Classically infiltrates dura, leptomeninges, basal cisterns - Solitary or multifocal CNS mass(es) ± abnormal CXR
  • Clival Neoplasms - Chordoma, clivus - Destructive midline mass centered in clivus with high T2 signal intensity - Sagittal images show tumor "thumb" indenting anterior pons - Chondrosarcoma, skull base - Arises from petrooccipital fissure - May extend posteriorly into prepontine cistern - Hyperintense on T2, enhances strongly but heterogeneously - Chondroid matrix mineralization on CT in 50% - Plasmacytoma, skull base - Solitary intraosseous osteolytic soft tissue mass with nonsclerotic margins - Peripherally displaced osseous expansion/fragmentation may be seen - Nasopharyngeal tumor (invading clivus) - Often squamous cell carcinoma arising from nasopharyngeal mucosal space - MPR images best show invasion of clivus & prepontine cistern extension
  • Schwannoma - T2-hyperintense, enhance - Larger lesion may be associated with cystic degeneration
  • Arachnoid Cyst - Extraaxial cyst follows CSF attenuation/signal - Suppresses completely with FLAIR; no DWI restriction
  • Craniopharyngioma - 90% Ca⁺⁺, 90% cystic, 90% enhance - May extend behind sella into posterior fossa - Location: Anywhere along infundibulum, sellar, suprasellar, & floor of 3rd ventricle - Adamantinomatous is most common type (> 90%) - May contain T1 hyperintense cyst due to high protein content
  • Neurenteric Cyst - Round/lobulated nonenhancing mass, slightly hyperintense to CSF on T1, FLAIR - Benign malformative endodermal CNS cyst
  • Ecchordosis Physaliphora - Congenital benign hamartomatous lesion from notochord remnant - Extends from clivus into prepontine cistern - Hyperintense on T2, no contrast enhancement - Bone CT: Well-corticated defect in dorsal clivus - Usually asymptomatic, found in 2% of autopsies

References

Selected References

1. Bazan R et al: Clinical symptoms, imaging features and cyst distribution in the cerebrospinal fluid compartments in patients with extraparenchymal neurocysticercosis. PLoS Negl Trop Dis. 10(11):e0005115, 2016
2. Louis DN et al: The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. Acta Neuropathol. 131(6):803-20, 2016
3. Park HH et al: Ecchordosis physaliphora: typical and atypical radiologic features. Neurosurg Rev. 40(1):87-94, 2016
4. Carrillo Mezo R et al: Relevance of 3D magnetic resonance imaging sequences in diagnosing basal subarachnoid neurocysticercosis. Acta Trop. 152:60-65, 2015
5. Garcia HH et al: Clinical symptoms, diagnosis, and treatment of neurocysticercosis. Lancet Neurol. 13(12):1202-15, 2014
6. Lerner A et al: Imaging of neurocysticercosis. Neuroimaging Clin N Am. 22(4):659-76, 2012

Images

Selected Images

CSF Flow Artifact Axial FLAIR MR reveals a hyperintense artifact due to turbulent flow within the prepontine cistern. This is a common location for flow artifacts. Also note sulcal hyperintensity (not artifact) from subarachnoid hemorrhage .

CSF Flow Artifact Axial FLAIR MR reveals a hyperintense artifact due to turbulent flow within the prepontine cistern. This is a common location for flow artifacts. Also note sulcal hyperintensity (not artifact) from subarachnoid hemorrhage .

Dolichoectasia (Vertebrobasilar) Axial T1 C+ MR demonstrates luminal enhancement of a dolichoectatic basilar artery with associated deformation of the pons .

Fusiform Aneurysm, ASVD Sagittal T1 MR shows a large mass anterior to the pons and medulla . Note mixed hyper-, isointense signal caused by slow flow and laminated clot in this classic ASVD fusiform aneurysm.

Meningioma Sagittal T1 C+ MR demonstrates avid meningioma enhancement with prepontine cistern extension and mass effect on the brainstem. Note the presence of enhancing dural tails .

Metastases, Skull & Meningeal Axial T1 C+ MR demonstrates extensive renal cell metastatic disease involving the clivus and overlying dura , effacing the prepontine cistern .

Metastases, Skull & Meningeal Axial T1 C+ MR shows a typical MR case of leptomeningeal seeding of carcinoma along the folia of the cerebellum and the brainstem as well as within bilateral Meckel caves .

Epidermoid Cyst Sagittal T1 MR depicts a nearly CSF isointense, nonenhancing, multilobulated epidermoid within prepontine, interpeduncular, & quadrigeminal cisterns . Note associated flattening of the ventral pons .

Chiari 2 (“Creeping Cerebellum”) Axial T2 MR shows cerebellar hemispheres herniating or "creeping" anteriorly due to a congenitally small posterior fossa of Chiari 2 malformation.

Exophytic Brainstem Glioma, Pediatric Axial FLAIR MR shows a diffuse brainstem glioma asymmetrically involving the pons with a small anterior exophytic component extending into the right prepontine cistern , next to the basilar artery .

Pituitary Macroadenoma (Giant) Sagittal T2 MR shows a giant macroadenoma with suprasellar extension , invading anteriorly into basisphenoid , and posteriorly into the basiocciput . The pons and basilar artery are displaced posteriorly and flattened .

Neurocysticercosis Axial T2 MR shows multiple racemose cysts in the subarachnoid spaces including the CPA and quadrigeminal and prepontine cisterns . Also note cysts within suprasellar cistern .

Intracranial Hypotension Sagittal T1 C+ MR demonstrates typical findings of intracranial hypotension, with obliteration of the suprasellar and prepontine cisterns with a sagging midbrain. Note pontine flattening against the clivus, dural enhancement, and cerebellar tonsillar descent.

Tuberculosis Axial T1 C+ MR demonstrates typical enhancement and thickened meninges filling the basilar cisterns in exudative tuberculous meningitis.

Tuberculosis Sagittal T1 C+ MR shows tuberculous abscesses within the basal and prepontine cisterns as well as within the anterior 3rd ventricle .

Fungal Diseases Axial T1 C+ MR shows thick enhancement in the subarachnoid space and along the pia filling the prepontine cistern and extending into the left internal auditory canal due to coccidioidal meningitis. Note also thin linear ependymal enhancement lining the 4th ventricle .

Fungal Diseases Axial T1 C+ MR demonstrates fine linear enhancement along the pia from candida meningitis.

Neurosarcoid Sagittal T1 C+ MR demonstrates a typical neurosarcoid appearance and location, with marked multifocal nodular appearing dural-based enhancement . The sella, parasellar, and basal cisternal locations are classic.

Chordoma, Clivus Sagittal T1 C+ MR shows a honeycomb pattern of enhancement with replacement of the clivus , "thumbing" of the pons posteriorly , and anterior extension of tumor into the sphenoid sinus .

Chondrosarcoma, Skull Base Axial T2 MR reveals hyperintense chondrosarcoma originating from the right petrooccipital fissure, extending posterosuperiorly into Meckel cave, petrous apex, and the prepontine and cerebellopontine angle cisterns .

Plasmacytoma, Skull Base Sagittal T1 MR demonstrates plasmacytoma expanding the clivus, invading sphenoid sinus and posterior nasal cavity, and elevating the pituitary gland .

Nasopharyngeal Tumor (Invading Clivus) Sagittal T1 C+ FS MR demonstrates nasopharyngeal squamous cell carcinoma infiltration of the mucosal space as well as abnormal marrow signal and cortical destruction of the expanded clivus. Prepontine soft tissue cistern extension is noted posterior to the clivus .

Schwannoma Axial T2 MR shows a partly cystic mass in the left prepontine and cerebellopontine angle cistern . The mass displaces and compresses the brainstem. This was a large cystic trigeminal schwannoma.

Arachnoid Cyst Sagittal T1 MR demonstrates a primarily suprasellar cistern arachnoid cyst extending into the interpeduncular and prepontine cisterns . Note flattening of the ventral pons .

Craniopharyngioma Sagittal T1 C+ MR demonstrates a partially cystic and solid enhancing craniopharyngioma in the suprasellar cistern with extension inferior into the prepontine cistern .

Neurenteric Cyst Sagittal T1 MR reveals a well-delineated, slightly ovoid, lobulated mass that was hyperintense to cerebrospinal fluid on all sequences.

Ecchordosis Physaliphora Axial T2 MR shows a lobulated cystic appearing mass in the prepontine cistern that indents the ventral pons . The mass is hyperintense relative to CSF. Note subtle dehiscence of clivus from where the lesion arose.

Additional Images

Fusiform Aneurysm, ASVD Axial T2WI MR shows a predominately hypointense fusiform aneurysm , representing a combination of slow intraluminal flow and subacute mural thrombus.

Epidermoid Cyst Axial DWI MR shows typical restricted diffusion with an epidermoid cyst involving the basal cisterns. Irregular "insinuating" margins as seen here are typical of larger epidermoid cysts, unlike the smooth lobulated borders of arachnoid cysts.

Pituitary Macroadenoma (Giant) Axial CECT shows a large, lobulated, enhancing, and destructive, skull base mass that extends into the anterior, middle, and posterior cranial fossae.

Neurocysticercosis Sagittal T1WI MR demonstrates a typical case of racemose (grape-like) neurocysticercosis in the basal cisterns and 3rd ventricle.

Chordoma, Clivus Axial T2WI MR shows typical marked T2 hyperintensity . Notice how the chordoma displaces the basilar artery towards the right and causes "thumbing," or indentation of the ventral pons .

Chondrosarcoma, Skull Base Axial bone CT demonstrates a typical case of a large chondrosarcoma involving the right petrooccipital fissure and the greater wing of the sphenoid. Internal matrix calcifications are present.

Plasmacytoma, Skull Base Axial T2WI MR reveals a plasmacytoma nearly isointense to brain . These T2 signal characteristics of this lesion would be unusual for a chordoma or chondrosarcoma.

Nasopharyngeal Tumor (Invading Clivus) Axial T1 C+ MR shows extensive clival invasion, perineural extension into the left petrous apex and Meckel cave , as well as invasion and widening of the left pterygopalatine fossa .

Schwannoma Axial T1 C+ FS MR shows a typical, isolated, intracranial, trigeminal schwannoma bridging the prepontine cistern and Meckel cave affecting the preganglionic segment of the trigeminal nerve .

Arachnoid Cyst Axial T2WI MR demonstrates a primarily suprasellar cistern arachnoid cyst extending into the interpeduncular and prepontine cisterns. Note flattening of the pons .

Craniopharyngioma Axial NECT shows the classic findings of craniopharyngioma including a cystic suprasellar mass with rim and globular calcifications and fluid-fluid levels .

Craniopharyngioma Sagittal T1WI MR demonstrates hyperintense mass in prepontine cistern that is connected to suprasellar mass by a thin stalk . Craniopharyngioma was found at surgery. Predominance of tumor mass in posterior fossa is unusual.

Neurenteric Cyst Sagittal T1WI MR shows a large, well-delineated, extraaxial mass elevating and displacing the pons and medulla. Note that the cyst internal signal intensity is slightly brighter than cerebrospinal fluid.