390 lines
42 KiB
Markdown
390 lines
42 KiB
Markdown
---
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title: "Cisterna Magna Mass"
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docid: "047add0c-7e4f-40a0-9933-8d6fa00a24f7"
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authors:
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- key: "d19354f3-7ff2-495a-ad3f-064122e45602"
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value: "Bernadette L. Koch, MD"
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- key: "20008105-51da-4bbf-aba6-e8253b2d9c21"
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value: "Daniel E. Meltzer, MD"
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breadcrumbs:
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-
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name: "Head and Neck"
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slug: "head-and-neck"
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treeNodeId: "ed24ed8c-5d57-4629-879b-447b82d2973d"
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-
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name: "Differential Diagnosis"
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slug: "differential-diagnosis"
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treeNodeId: "40d68862-8975-4dde-ac2b-ebc43ab0fb5c"
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-
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name: "CPA-IAC and Posterior Fossa"
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slug: "cpa-iac-and-posterior-fossa"
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treeNodeId: "c590eedb-4a3b-4158-a04f-ad880564c992"
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-
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name: "Anatomically Based Differentials"
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slug: "anatomically-based-differentials"
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treeNodeId: "debfb06c-8656-4f5d-92c1-eaa468185d78"
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-
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name: "Cisterna Magna Mass"
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slug: "cisterna-magna-mass"
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treeNodeId: null
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category: "Head and Neck"
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documentVersionId: "86b48ea6-d9ea-428a-b5cb-32a58aaf84b2"
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imageCount: 37
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lastUpdated: "07/16/24"
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pageDescription: "Cisterna Magna Mass"
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pageKeywords: "Head and Neck, Differential Diagnosis, CPA-IAC and Posterior Fossa, Anatomically Based Differentials, Cisterna Magna Mass"
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pageTitle: "Cisterna Magna Mass | STATdx"
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enhancedTitle: "Cisterna Magna Mass"
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type: "DDX"
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references: true
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breadcrumbs:
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- "Head and Neck"
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- "Differential Diagnosis"
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- "CPA-IAC and Posterior Fossa"
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- "Anatomically Based Differentials"
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- "Cisterna Magna Mass"
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---
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# ESSENTIAL INFORMATION
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- ## Key Differential Diagnosis Issues
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- Cisterna magna (CM) between medulla (anterior), occiput (posterior) (a.k.a. cerebellomedullary cistern)
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- Below/behind inferior vermis
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- Large medullary cistern masses may extend laterally, posteriorly into CM
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- Most common adult lesions are tonsillar associated
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- Indirect (secondary effect on tonsil) > direct (lesion in tonsil)
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- MR and clinical information helps DDx
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- ## Helpful Clues for Common Diagnoses
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- **Herniation Syndromes, Intracranial**
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- Tonsillar herniation most often 2° to posterior fossa (PF) mass effect
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- Tonsils pushed down into CM
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- Peg-like configuration of tonsils
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- Tonsil folia usually oriented horizontally → become vertically oriented when herniated
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- 4th ventricle may obstruct → obstructive hydrocephalus
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- **Chiari 1**
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- Pointed cerebellar tonsils ≥ 5 mm below foramen magnum (FM)
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- Crowded FM + effaced CSF
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- ± brainstem compression
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- ± retroflexed odontoid, horizontal clivus, scoliosis
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- PF usually normal size
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- Syrinx in 30-70%
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- Treatment aim = restore normal CSF flow at FM
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- **Chiari 2**
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- Small PF → contents herniates inferiorly through FM and superiorly through widened incisura
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- Cascade of tissue (vermis, not tonsil) herniates downward through FM
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- Caudal brainstem herniation with cervicomedullary kink, tectal beaking, falx insufficiency
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- ± ventriculomegaly, subependymal gray matter heterotopia, &/or polymicrogyria
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- ~ 100% secondary to open spinal dysraphism, most often myelomeningocele
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- **Dandy-Walker Continuum**
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- Dandy-Walker continuum is broad spectrum of cystic PF malformations
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- 2/3 have associated CNS &/or extracranial anomalies
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- All may have inner table occipital bone scalloping
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- Dandy-Walker malformation classic triad
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- Vermian agenesis/hypogenesis
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- Cystic dilatation 4th ventricle
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- Large PF with lambdoid-torcular inversion
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- ± hydrocephalus
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- Vermian hypoplasia
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- Varying degrees of vermian hypoplasia
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- ± rotation of vermis
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- No enlargement of PF
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- Blake pouch cyst
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- Open 4th ventricle
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- Elevated tegmentovermian angle
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- Normal size and morphology of vermis
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- Mega CM
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- Enlarged retrocerebellar cistern communicates with normal 4th ventricle
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- Normal vermis
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- ## Helpful Clues for Less Common Diagnoses
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- **Arachnoid Cyst**
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- Sharply demarcated extraaxial cyst that follows CSF attenuation/signal
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- FLAIR suppresses; no diffusion restriction
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- Size varies from few millimeters to giant
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- Often asymptomatic, found incidentally
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- Cerebellopontine angle (CPA) location > CM
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- **Ependymoma**
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- Anywhere in neuraxis: 2/3 in PF, 1/3 in supratentorial
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- 3rd most common malignant pediatric brain tumor arising in PF
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- Heterogeneous T1/T2 signal with mild to moderate enhancement
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- Soft or "plastic" tumor squeezes out of 4th ventricle foramina into cisterns
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- Calcification common (50%)
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- ± cysts, hemorrhage
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- Sagittal imaging can distinguish origin as floor vs. roof of 4th ventricle
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- CSF seeding may occur → image entire neuraxis
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- **Meningioma**
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- CM rare PF location
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- CPA, medullary cisterns more common than CM
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- CM meningiomas usually arise from occipital squamosa
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- Well-demarcated, lobulated/rounded enhancing mass with dural attachment
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- Hyperostosis, tumoral calcifications, ↑ vascular markings
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- **Metastasis**
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- Linear or nodular meningeal enhancement
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- MR CSF flow may be helpful establishing location and degree of CSF obstruction
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- Primary tumors include breast, lung, melanoma, prostate
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- Lymphoproliferative malignancy = lymphoma and leukemia
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- Primary CNS tumor seed basal cisterns (drop metastases)
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- **Image entire neuraxis**
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- **Intracranial Hypotension**
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- Sagittal shows brain descent in 40-50%
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- Caudal displacement of cerebellar tonsils in 25-75%
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- Diffusely and intensely enhancing dura in 85%
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- Bilateral subdural fluid collections in 15%
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- Dural venous sinus may be distended (convex margins)
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- Enlarged pituitary
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- Frequently misdiagnosed syndrome of headache caused by ↓ intracranial CSF pressure from spontaneous spinal CSF leak
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- ## Helpful Clues for Rare Diagnoses
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- **Subependymoma**
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- T2-hyperintense lobular, nonenhancing intraventricular mass
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- When arises from 4th ventricle floor, may extend posteroinferiorly into CM
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- More common in middle-aged, older adults
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- 0.7% of intracranial neoplasms
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- **Epidermoid Cyst**
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- Congenital inclusion cysts
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- Lobulated, irregular, CSF-like mass with "fronds" insinuate cistern
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- FLAIR usually does not completely null; diffusion yields high-signal restriction
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- 0.2-1.8% of all primary intracranial tumors
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- CPA cistern (40-50%) > 4th ventricle (17%) > sellar/parasellar (10-15%)
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- Rare malignant degeneration into squamous cell carcinoma
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- **Dermoid Cyst**
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- Fat appearance: Use fat suppression sequence to confirm
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- With rupture, fat droplets in cisterns, sulci, and ventricles with extensive MR enhancement possible from chemical meningitis
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- Rare: < 0.5% of primary intracranial tumors
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- Rupture can cause significant morbidity/mortality
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- Rare malignant degeneration into squamous cell carcinoma
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- **Hemangioblastoma**
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- Intraaxial PF mass with cyst, enhancing mural nodule abutting pia
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- Classified as 1 of mesenchymal, nonmeningothelial tumors
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- Familial = von Hippel-Lindau
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- ≈ 30% of patients with hemangioblastoma have von Hippel-Lindau
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- 7-10% of PF tumors
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- **Neurenteric Cyst**
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- Round/lobulated, nonenhancing, slightly hyperintense to CSF mass
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- Most intracranial NECs found in PF
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- Benign malformative endodermal CNS cyst
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- Part of split spinal cord malformation spectrum; persistent neurenteric canal
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- Location
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- Thoracic (42%), cervical (32%)
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- Others: Lumbar spine, basilar cisterns, brain parenchyma
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- Anterior medullary, CPA cisterns > CM
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## References
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# Selected References
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1. [Pindrik J et al: Imaging in Chiari I malformation. Neurosurg Clin N Am. 34(1):67-79, 2023](http://www.ncbi.nlm.nih.gov/pubmed/?term=36424066%5Bpmid%5D)
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1. [Paun L et al: Foramen magnum meningiomas: a systematic review and meta-analysis. Neurosurg Rev. 44(5):2583-96, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=33507444%5Bpmid%5D)
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1. [Menezes AH et al: Neurenteric cysts at foramen magnum in children: presentation, imaging characteristics, and surgical management-case series and literature review. Childs Nerv Syst. 36(7):1379-84, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32322975%5Bpmid%5D)
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1. [Abdel Razek AA et al: Magnetic resonance imaging of malformations of midbrain-hindbrain. J Comput Assist Tomogr. 40(1):14-25, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26599961%5Bpmid%5D)
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1. [Dorfer C et al: Ependymoma: a heterogeneous tumor of uncertain origin and limited therapeutic options. Handb Clin Neurol. 134:417-31, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26948369%5Bpmid%5D)
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1. [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](http://www.ncbi.nlm.nih.gov/pubmed/?term=27157931%5Bpmid%5D)
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1. [Tao C et al: Prognostic factors affecting the surgical outcome of anterolateral benign tumors in the foramen magnum region. Int J Surg. 33 Pt A:172-6, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27528437%5Bpmid%5D)
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1. [Tian W et al: A quantitative study of intracranial hypotensive syndrome by magnetic resonance. Clin Neurol Neurosurg. 141:71-6, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26745515%5Bpmid%5D)
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1. [Yamahata H et al: Exploitation of simple classification and space created by the tumor for the treatment of foramen magnum meningiomas. World Neurosurg. 87:1-7, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26409077%5Bpmid%5D)
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1. [Cesmebasi A et al: The Chiari malformations: a review with emphasis on anatomical traits. Clin Anat. 28(2):184-94, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25065525%5Bpmid%5D)
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1. [Liao CC et al: Clinical features and surgical outcomes of sporadic cerebellar hemangioblastomas. Clin Neurol Neurosurg. 125:160-5, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=25156409%5Bpmid%5D)
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## Images
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### Selected Images
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**Herniation Syndromes, Intracranial**
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*Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='img/arrows/WC.png'/>, enlarged foramen of Monro <img src='img/arrows/CS.png'/>, and enlarged 3rd <img src='img/arrows/CO.png'/> and lateral <img src='img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.*
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**Herniation Syndromes, Intracranial**
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*Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='img/arrows/WC.png'/>, enlarged foramen of Monro <img src='img/arrows/CS.png'/>, and enlarged 3rd <img src='img/arrows/CO.png'/> and lateral <img src='img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.*
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**Herniation Syndromes, Intracranial**
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*Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='img/arrows/WC.png'/>, enlarged foramen of Monro <img src='img/arrows/CS.png'/>, and enlarged 3rd <img src='img/arrows/CO.png'/> and lateral <img src='img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.*
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**Herniation Syndromes, Intracranial**
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*Sagittal T1 C+ MR shows a cystic mass with an enhancing nodule <img src='img/arrows/WS.png'/>, consistent with hemangioblastoma, pushing the tonsils inferiorly through the foramen magnum <img src='img/arrows/WO.png'/>. Note effaced 4th ventricle <img src='img/arrows/WC.png'/>, enlarged foramen of Monro <img src='img/arrows/CS.png'/>, and enlarged 3rd <img src='img/arrows/CO.png'/> and lateral <img src='img/arrows/CC.png'/> ventricles, consistent with obstructive hydrocephalus.*
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**Chiari 1**
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*Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='img/arrows/WO.png'/>, effacement of CSF at the foramen magnum, and associated cervicothoracic syrinx <img src='img/arrows/WC.png'/>.*
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**Chiari 1**
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*Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='img/arrows/WO.png'/>, effacement of CSF at the foramen magnum, and associated cervicothoracic syrinx <img src='img/arrows/WC.png'/>.*
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**Chiari 2**
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*Sagittal T2 MR shows a small posterior fossa with extension of the cerebellar peg <img src='img/arrows/WS.png'/> through the foramen magnum to the level of C6. The cervicomedullary junction and 4th ventricle <img src='img/arrows/WO.png'/> are low-lying and there is mild tectal beaking <img src='img/arrows/WC.png'/> and moderate prominence of the massa intermedia <img src='img/arrows/BS.png'/>.*
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**Dandy-Walker Continuum**
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*Sagittal T2 MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='img/arrows/WS.png'/>, upward rotation of severely hypoplastic vermis <img src='img/arrows/WO.png'/>, markedly enlarged posterior fossa, and elevated torcula.*
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**Arachnoid Cyst**
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*Sagittal T1WI MR shows a CSF isointense arachnoid cyst <img src='img/arrows/WO.png'/> filling the lower posterior fossa, effacing the cisterna magna, flattening the cervicomedullary junction <img src='img/arrows/WS.png'/>, and extending caudally into the upper cervical canal.*
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**Ependymoma**
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*Sagittal T1WI C+ MR shows enhancing tissue extruding through the foramen of Magendie, filling the cisterna magna <img src='img/arrows/WS.png'/>. Resultant obstruction has caused enlargement of the cerebral aqueduct <img src='img/arrows/WC.png'/> and dilated 3rd ventricle <img src='img/arrows/WO.png'/>.*
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**Meningioma**
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*Sagittal T1WI MR demonstrates dural-based tumor <img src='img/arrows/WS.png'/> with significant mass effect compressing and displacing the cerebellum. Note the trapped CSF clefts <img src='img/arrows/WC.png'/>. The tumor encroaches on the cisterna magna.*
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**Metastasis**
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*Axial T1WI C+ MR shows a typical case of primary CNS lymphoma with subependymal tumor spread. Note a posterior fossa mass near the foramen of Luschka <img src='img/arrows/WS.png'/> as well as a 2nd dural-based mass <img src='img/arrows/WO.png'/>.*
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**Intracranial Hypotension**
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*Sagittal T1WI C+ MR shows obliteration of the suprasellar cistern <img src='img/arrows/WS.png'/>, sagging/fat midbrain with closed angle between the peduncles and the pons <img src='img/arrows/WO.png'/>, dural enhancement <img src='img/arrows/WC.png'/>, and tonsillar descent <img src='img/arrows/BO.png'/> with effacement of the cisterna magna.*
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**Subependymoma**
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*Sagittal T1WI C+ MR in 40-year-old man shows an enhancing mass at the bottom of the 4th ventricle <img src='img/arrows/WS.png'/> filling the cisterna magna.*
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**Epidermoid Cyst**
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*Sagittal T1WI MR shows a typical case of a large 4th ventricular epidermoid cyst <img src='img/arrows/WS.png'/>, which follows CSF intensity but is often slightly brighter and mildly heterogeneous in signal.*
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**Dermoid Cyst**
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*Axial T2WI MR demonstrates a T2- hyperintense mass <img src='img/arrows/WS.png'/> encroaching laterally upon the ventral CSF at the foramen magnum. There was evidence of rupture (not shown) causing recurrent meningitis.*
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**Hemangioblastoma**
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*Sagittal T1WI C+ MR shows an enhancing vermian mass protruding through the foramen magnum <img src='img/arrows/WS.png'/>. An associated cyst <img src='img/arrows/WO.png'/> is deforming the 4th ventricle <img src='img/arrows/WC.png'/>.*
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**Neurenteric Cyst**
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*Axial T1WI C+ MR shows a neurenteric cyst encroaching <img src='img/arrows/BS.png'/> upon the prepontine cistern. Although most often these are located anteriorly, they may arise posteriorly at the cisterna magnum.*
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### Additional Images
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**Chiari 2**
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*Sagittal T1WI MR shows a small posterior fossa with extension of the cerebellar peg <img src='img/arrows/WS.png'/> through the foramen magnum to the level of C3. The cervicomedullary junction and 4th ventricle <img src='img/arrows/WO.png'/> are low-lying, and there is tectal beaking <img src='img/arrows/WC.png'/>.*
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**Dandy-Walker Continuum**
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*Sagittal T1WI MR demonstrates a markedly enlarged posterior fossa with cystic dilatation of the 4th ventricle <img src='img/arrows/WO.png'/>, upwardly rotated hypoplastic vermis <img src='img/arrows/WS.png'/>, and low-lying torcular Herophili <img src='img/arrows/WC.png'/>.*
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**Chiari 1**
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*Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='img/arrows/WO.png'/> and effacement of CSF at the foramen magnum.*
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**Chiari 1**
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*Sagittal T2 MR in a patient with occipital headaches shows a significantly pointed configuration of a low-lying cerebellar tonsil <img src='img/arrows/WS.png'/> to the level of the midposterior ring of C2. Notice also the dorsally tilted dens <img src='img/arrows/WO.png'/> and effacement of CSF at the foramen magnum.*
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**Chiari 1**
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*Sagittal T1WI MR shows inferior extension of the peg-like cerebellar tonsils <img src='img/arrows/WS.png'/> well below the level of the foramen magnum <img src='img/arrows/BO.png'/>, consistent with Chiari 1.*
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**Chiari 1**
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*Sagittal T1WI MR shows inferior extension of the peg-like cerebellar tonsils <img src='img/arrows/WS.png'/> well below the level of the foramen magnum <img src='img/arrows/BO.png'/>, consistent with Chiari 1.*
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**Herniation Syndromes, Intracranial**
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*Axial T2WI MR at the level of the foramen magnum demonstrates downward tonsillar herniation <img src='img/arrows/WS.png'/> secondary to mass affect from brain death.*
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**Herniation Syndromes, Intracranial**
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*Axial T2WI MR at the level of the foramen magnum demonstrates downward tonsillar herniation <img src='img/arrows/WS.png'/> secondary to mass affect from brain death.*
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**Herniation Syndromes, Intracranial**
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*Sagittal T1WI MR shows cerebellar tonsillar herniation <img src='img/arrows/WC.png'/> from a large left posterior fossa mass. Note compression of 4th ventricle <img src='img/arrows/WO.png'/>. Supratentorial ventricles are enlarged <img src='img/arrows/WS.png'/>.*
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**Herniation Syndromes, Intracranial**
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*Sagittal T1WI MR shows cerebellar tonsillar herniation <img src='img/arrows/WC.png'/> from a large left posterior fossa mass. Note compression of 4th ventricle <img src='img/arrows/WO.png'/>. Supratentorial ventricles are enlarged <img src='img/arrows/WS.png'/>.*
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**Chiari 1**
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*Sagittal CINE phase-contrast CSF flow - diastolic shows diminished posterior CSF flow <img src='img/arrows/WS.png'/> compared to anterior CSF flow <img src='img/arrows/BO.png'/> at the site of tonsillar impaction.*
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**Chiari 1**
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*Sagittal CINE phase-contrast CSF flow - diastolic shows diminished posterior CSF flow <img src='img/arrows/WS.png'/> compared to anterior CSF flow <img src='img/arrows/BO.png'/> at the site of tonsillar impaction.*
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**Chiari 1**
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*Sagittal T2WI MR shows a classic case of Chiari 1 with pointed cerebellar tonsils <img src='img/arrows/WO.png'/> protruding through the foramen magnum and effacing the cisterna magna.*
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**Chiari 1**
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*Sagittal T2WI MR shows a classic case of Chiari 1 with pointed cerebellar tonsils <img src='img/arrows/WO.png'/> protruding through the foramen magnum and effacing the cisterna magna.*
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**Chiari 2**
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*Sagittal T2WI MR shows a small posterior fossa with caudal descent of cerebellar tonsillar tissue <img src='img/arrows/WS.png'/>, elongation of the 4th ventricle <img src='img/arrows/WC.png'/>, and cervical cord syrinx <img src='img/arrows/WO.png'/>.*
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**Chiari 2**
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*Axial FSPGR image demonstrates caudally displaced cerebellar tissue <img src='img/arrows/WO.png'/> wrapping around the brainstem. This is sometimes referred to as a "creeping cerebellum" due to a small posterior fossa.*
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**Chiari 2**
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*Sagittal T1WI MR shows caudal descent of cerebellar vermian tissue <img src='img/arrows/WS.png'/> and elongated 4th ventricle <img src='img/arrows/WC.png'/> as well as callosal dysgenesis <img src='img/arrows/WO.png'/> and a small posterior fossa.*
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**Chiari 2**
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*Sagittal T1 C+ MR shows a small posterior fossa with extension of the vermis through the foramen magnum to the level of C1/2 <img src='img/arrows/WS.png'/>. The 4th ventricle is small <img src='img/arrows/WO.png'/>, and there is tectal beaking <img src='img/arrows/WC.png'/>.*
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**Dandy-Walker Continuum**
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*Axial T2WI MR shows a normal 4th ventricle and vermis; however, there is a prominent retrocerebellar CSF space <img src='img/arrows/WO.png'/>, which does not cause compression but does remodel endosteum, leading to mega cisterna magna.*
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**Arachnoid Cyst**
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*Sagittal T1WI MR demonstrates a CSF-intensity arachnoid cyst remodeling the endosteum <img src='img/arrows/WS.png'/> and filling the cisterna magna <img src='img/arrows/WO.png'/>.*
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**Ependymoma**
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*Sagittal T2WI MR shows heterogeneous features of an ependymoma. Focal hyperintense regions correspond to focal necrosis <img src='img/arrows/WS.png'/> and hypointense regions correlate to calcification <img src='img/arrows/WC.png'/>.*
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**Ependymoma**
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*Axial T1 C+ MR demonstrates a heterogeneously enhancing ependymoma <img src='img/arrows/BS.png'/> containing cystic elements <img src='img/arrows/WO.png'/>.*
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**Ependymoma**
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*Sagittal T1 C+ MR shows an enhancing mass expanding the 4th ventricle <img src='img/arrows/WS.png'/>. The mass is also distending the obex <img src='img/arrows/WO.png'/> and protruding through the foramen of Magendie into the cisterna magna <img src='img/arrows/WC.png'/>.*
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**Meningioma**
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*Axial T2WI MR demonstrates a posterior fossa meningioma <img src='img/arrows/WS.png'/> with significant mass effect upon the cerebellum with interposed trapped CSF clefts <img src='img/arrows/WO.png'/> and vessels <img src='img/arrows/WC.png'/>.*
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**Meningioma**
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*Axial T1 C+ MR of a meningioma shows an avidly enhancing, dural-based mass splaying the cerebellar hemispheres, flattening the 4th ventricle <img src='img/arrows/WC.png'/>, with dural tail <img src='img/arrows/WO.png'/>.*
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**Metastasis**
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*Coronal T1 C+ MR demonstrates the diffuse enhancement of meningeal carcinomatosis from metastatic xanthoastrocytoma <img src='img/arrows/WS.png'/> spread throughout the posterior fossa, folia, and also more cephalad.*
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**Intracranial Hypotension**
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*Sagittal T1WI MR shows tonsillar descent <img src='img/arrows/WC.png'/> and dural thickening <img src='img/arrows/WS.png'/> secondary to intracranial hypotension.*
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**Epidermoid Cyst**
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*Axial DWI MR shows a hyperintense mass <img src='img/arrows/WS.png'/> in the midline posterior fossa.*
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**Hemangioblastoma**
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*Sagittal T1 C+ MR demonstrates a mostly solid hemangioblastoma <img src='img/arrows/WS.png'/> involving the cerebellar tonsils and effacing the cisterna magna.*
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