statdx/docs_md/articles/cystic-cpa-mass_6c60db6d-8093-4df5-8cbb-c6f6570ae167.md

title, docid, authors, breadcrumbs, category, cmeTopicId, documentVersionId, imageCount, lastUpdated, pageDescription, pageKeywords, pageTitle, enhancedTitle, type, references, breadcrumbs

title	docid	authors	breadcrumbs	category	cmeTopicId	documentVersionId	imageCount	lastUpdated	pageDescription	pageKeywords	pageTitle	enhancedTitle	type	references	breadcrumbs
Cystic CPA Mass	6c60db6d-8093-4df5-8cbb-c6f6570ae167	key value 07a2c087-6202-49e7-870b-7aa162d18f06 Bronwyn E. Hamilton, MD	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 Generic Imaging Patterns generic-imaging-patterns ba996846-af9d-4714-b15b-84315b9ad282 name slug treeNodeId Cystic CPA Mass cystic-cpa-mass null	Head and Neck	75974523-991b-4e4d-90c7-5a70d21f2598	dd13cf85-d7fc-40b3-b753-b3231a135c6b	23	02/09/24	Cystic CPA Mass	Head and Neck, Differential Diagnosis, CPA-IAC and Posterior Fossa, Generic Imaging Patterns, Cystic CPA Mass	Cystic CPA Mass | STATdx	Cystic CPA Mass	DDX	true	Head and Neck Differential Diagnosis CPA-IAC and Posterior Fossa Generic Imaging Patterns Cystic CPA Mass

---

title: "Cystic CPA Mass" docid: "6c60db6d-8093-4df5-8cbb-c6f6570ae167" authors:

• key: "07a2c087-6202-49e7-870b-7aa162d18f06" value: "Bronwyn E. Hamilton, MD" breadcrumbs:
• name: "Head and Neck" slug: "head-and-neck" treeNodeId: "ed24ed8c-5d57-4629-879b-447b82d2973d"
• name: "Differential Diagnosis" slug: "differential-diagnosis" treeNodeId: "40d68862-8975-4dde-ac2b-ebc43ab0fb5c"
• name: "CPA-IAC and Posterior Fossa" slug: "cpa-iac-and-posterior-fossa" treeNodeId: "c590eedb-4a3b-4158-a04f-ad880564c992"
• name: "Generic Imaging Patterns" slug: "generic-imaging-patterns" treeNodeId: "ba996846-af9d-4714-b15b-84315b9ad282"
• name: "Cystic CPA Mass" slug: "cystic-cpa-mass" treeNodeId: null category: "Head and Neck" cmeTopicId: "75974523-991b-4e4d-90c7-5a70d21f2598" documentVersionId: "dd13cf85-d7fc-40b3-b753-b3231a135c6b" imageCount: 23 lastUpdated: "02/09/24" pageDescription: "Cystic CPA Mass" pageKeywords: "Head and Neck, Differential Diagnosis, CPA-IAC and Posterior Fossa, Generic Imaging Patterns, Cystic CPA Mass" pageTitle: "Cystic CPA Mass | STATdx" enhancedTitle: "Cystic CPA Mass" type: "DDX" references: true breadcrumbs:
• "Head and Neck"
• "Differential Diagnosis"
• "CPA-IAC and Posterior Fossa"
• "Generic Imaging Patterns"
• "Cystic CPA Mass"

---

ESSENTIAL INFORMATION

• Key Differential Diagnosis Issues

  • This differential diagnosis is constructed around lesions of cerebellopontine angle (CPA) that may have "cystic" imaging features - Typically cystic lesions: Epidermoid, arachnoid, & neurenteric cysts; neurocysticercosis & large endolymphatic sac anomaly - Many solid CPA tumors may have either intramural cysts, necrosis, or extramural cysts as typical or variant MR imaging manifestation - Schwannoma: Vestibular, facial nerve, trigeminal, or jugular foramen schwannoma with intramural or extramural cysts can all be found in CPA area - Hemangioblastoma: Cerebellar cystic & solid tumor that may project into CPA cistern - Endolymphatic sac tumor: CPA involved if large - Cystic meningioma
  • Idealized imaging protocol in evaluating cystic CPA masses - T1 C+ fat-saturated MR is gold standard - Contrast helps differentiate solid from cystic components of tumors, such as vestibular or facial nerve schwannoma & hemangioblastoma - DWI for possible epidermoid cyst (restricted diffusion) - T2 thin-section, high-resolution MR - Also sorts out solid and cystic components of lesions - Helps with cranial nerve & vascular anatomy

• Helpful Clues for Common Diagnoses

  • Epidermoid Cyst - Key facts - Definition: Congenital rest of epithelial tissue in CPA - Imaging findings - Insinuating or scalloping brainstem margin - T1 MR: Iso- to slightly hyperintense relative to CSF - T1 C+ MR: Typically nonenhancing cyst; may be hard to see - Minimal marginal cyst enhancement in 25% - Soft tissue enhancement present in rare cases of malignant degeneration to squamous cell carcinoma; PET avidity can help confirm suspicion - T2 MR: High-signal, well-circumscribed CPA mass - FLAIR: Lack of complete fluid suppression - DWI: Restricted diffusion (high signal) makes diagnosis
  • Arachnoid Cyst - Key facts - Definition: Congenital lesion resulting from failure of embryonic meninges to merge results in cyst between split arachnoid membrane - Imaging findings - Fills cistern with rounded margins - T1 C+ MR: No enhancement - FLAIR: Lesion attenuates (black like CSF) - DWI: Isointense to CSF (no restriction)

• Helpful Clues for Less Common Diagnoses

  • Vestibular Schwannoma W****ith Intramural Cyst(s) - Key facts - Definition: Vestibular schwannoma may have either intramural or extramural cysts associated - Imaging findings - Solid CPA-IAC mass with intramural cysts - Bone CT: Larger lesions flare medial IAC component - T1 C+ MR: Enhancing solid tumor component ± intramural cysts (common) ± extramural cyst (rare) - Microhemorrhages on T2* GRE or SWI favor schwannoma over meningioma
  • Hemangioblastoma - Key facts - Definition: Benign tumor composed of stromal cells in small blood vessels of CNS - Adult with intraaxial posterior fossa mass abutting pia - Associated with von Hippel Lindau (VHL) in 25-40% - Supratentorial hemangioblastomas more likely VHL related - Imaging findings - Cerebellar cystic & solid tumor - T1 C+ MR: 60% of tumors with solid enhancing & cystic components (40% solid only)
  • Large Endolymphatic Sac Anomaly (IP-II) - Key facts - Bilateral congenital sensorineural hearing loss that appears in child with cascading hearing loss pattern - Most common congenital imaging abnormality - Recommendation to avoid contact sports - Imaging findings - Bone CT: Enlarged bony vestibular aqueduct - T2 high-resolution MR: Enlarged endolymphatic sac & duct + mild cochlear malformation (modiolar deficiency, deficient apical septation, & scalar chamber asymmetry)
  • Neurocysticercosis - Key facts - Definition: Intracranial infection caused by pork tapeworm (Taenia solium) - Imaging findings - Cysts with "dots" inside - Appearance varies with stage - T1 C+ MR: Cysts with enhancing thin or thick wall - May be associated with hydrocephalus

• Helpful Clues for Rare Diagnoses

  • Vestibular Schwannoma W****ith Extramural Cyst - Key facts - Vestibular schwannoma with extramural cyst - Cyst may be "trapped CSF" or actual arachnoid cyst - Neurootologists call extramural cyst "herald cyst" - Imaging findings - CPA-IAC mass with extramural cyst - Bone CT: Large lesions flare IAC medial component - T1 C+ MR: Enhancing solid tumor component ± extramural cyst - Microhemorrhages on T2* GRE or SWI favor schwannoma over meningioma
  • Facial Nerve Schwannoma in CPA-IAC W****ith Cyst - Key facts - Rare CPA-IAC mass with labyrinthine tail involving labyrinthine segment of facial nerve canal - Often presents with hearing loss before facial nerve symptoms - Imaging findings - Bone CT: Labyrinthine segment of facial nerve may be enlarged - T1 C+ MR: Enhancing tubular mass in CPA-IAC & labyrinthine segment of facial nerve; intramural or extramural cyst visible
  • Schwannoma, Trigeminal, Skull Base - Key facts - Most common presentation is ipsilateral facial pain - Imaging findings - CPA cystic enhancing mass with tail extending toward or into Meckel cave is characteristic - Look for denervation of masticator space muscles
  • NeurentericCyst - Key facts - Arises at time of notochordal development during transitory existence of neurenteric canal - Benign endodermal lesion of CNS - Often presents as incidental rounded to ovoid mass in prepontine cistern - Imaging findings - MR shows intermediate- to high-signal T1 prepontine "cystic" mass
  • Jugular Foramen Schwannoma W****ith Intramural Cyst - Key facts - Presents with mixture of 9-12 cranial neuropathy - Imaging findings - Bone CT: Enlarged, sharply marginated jugular foramen - T1 MR: Iso-g to hyperintense compared to CSF - T1 C+ MR: Enhancing mass with intramural cysts arising from jugular foramen - Intramural cysts in 25% of jugular foramen schwannomas - Other MR findings: Mass projects superomedially into CPA cistern, often with brainstem compression
  • Cystic Metastasis in CPA - Key facts - Usually in patients with known primary cancer - Imaging findings - T1 C+ MR: Enhancing mass with cystic component may mimic schwannoma or cystic meningioma - Likely to exhibit rapid growth pattern and more symptoms, such as facial nerve palsy, than benign tumors like schwannoma
  • Endolymphatic Sac Tumor - Key facts - Sporadic or associated with VHL - Bilateral tumors &/or concurrent hemangioblastoma indicates VHL - Imaging findings - Bone CT: Permeative destruction of posterior petrous temporal bone centered at vestibular aqueduct - T1 MR: Hyperintense foci due to internal hemorrhage are characteristic - T1 C+ MR: Partly cystic, heterogenous enhancing mass - DOTATATE scan may show mild uptake due to somatostatin receptor type 2A expression in tumor vasculature not tumor cells
  • Meningioma, Cystic - T1 C+ MR: Rare, heterogeneous, partly cystic enhancing mass - Rare meningioma variant that mimics schwannoma; most are clear cell subtype

References

Selected References

1. Ali NE et al: Natural history of cystic vestibular schwannomas. Ann Otol Rhinol Laryngol. 132(7):795-9, 2023
2. Adachi S et al: Unusual imaging characteristics of cystic meningioma in cerebellopontine angle. Neuroradiol J. 35(6):777-9, 2022
3. Geng Y et al: Endolymphatic sac tumour: exploring the role of CT and MRI features in the diagnosis of 22 cases. Clin Radiol. 77(8):e592-8, 2022
4. Talukdar R et al: Endolymphatic sac tumor: single-institution series of seven cases with updated review of literature. Eur Arch Otorhinolaryngol. 279(5):2591-8, 2022
5. Parlak S et al: 3 Tesla MR imaging of the large endolymphatic duct and sac anomaly with audiological correlation. Eur J Radiol. 145:110064, 2021
6. Saigal G et al: Utility of microhemorrhage as a diagnostic tool in distinguishing vestibular schwannomas from other cerebellopontine angle (CPA) Tumors. Indian J Otolaryngol Head Neck Surg. 73(3):321-6, 2021
7. Lou R et al: 68Ga-DOTATATE uptake in an endolymphatic sac tumor: radiologic-pathologic correlation. Clin Nucl Med. 45(7):563-5, 2020
8. Connor SEJ et al: Is CT or MRI the optimal imaging investigation for the diagnosis of large vestibular aqueduct syndrome and large endolymphatic sac anomaly? Eur Arch Otorhinolaryngol. 276(3):693-702, 2019
9. Eliezer M et al: Clinical and radiological characteristics of malignant tumors located to the cerebellopontine angle and/or internal acoustic meatus. Otol Neurotol. 40(9):1237-45, 2019
10. Le H et al: Clinicoradiologic characteristics of endolymphatic sac tumors. Eur Arch Otorhinolaryngol. 276(10):2705-14, 2019
11. Touska P et al: Temporal bone tumors: an imaging update. Neuroimaging Clin N Am. 29(1):145-72, 2019
12. Schnack DT et al: Sporadic endolymphatic sac tumor-a very rare cause of hearing loss, tinnitus, and dizziness. J Int Adv Otol. 13(2):289-91, 2017
13. Agarwal A: Intracranial trigeminal schwannoma. Neuroradiol J. 28(1):36-41, 2015
14. Dispenza F et al: Imaging of vestibular schwannoma with prevalent cystic component: cystic vestibular schwannoma. Otol Neurotol. 30(5):681-2, 2009
15. Piccirillo E et al: Cystic vestibular schwannoma: classification, management, and facial nerve outcomes. Otol Neurotol. 30(6):826-34, 2009
16. Zhang L et al: Trigeminal schwannomas: a report of 42 cases and review of the relevant surgical approaches. Clin Neurol Neurosurg. 111(3):261-9, 2009
17. Bonneville F et al: Imaging of cerebellopontine angle lesions: an update. Part 1: enhancing extra-axial lesions. Eur Radiol. 17(10):2472-82, 2007
18. Bonneville F et al: Imaging of cerebellopontine angle lesions: an update. Part 2: intra-axial lesions, skull base lesions that may invade the CPA region, and non-enhancing extra-axial lesions. Eur Radiol. 17(11):2908-20, 2007
19. Kiliçkesmez O: Endolymphatic sac tumor in a patient with von Hippel-Lindau disease: MR imaging findings. Diagn Interv Radiol. 12(1):14-6, 2006
20. Patel NP et al: The radiologic diagnosis of endolymphatic sac tumors. Laryngoscope. 116(1):40-6, 2006
21. Preece MT et al: Intracranial neurenteric cysts: imaging and pathology spectrum. AJNR Am J Neuroradiol. 27(6):1211-6, 2006
22. Nelson MD Jr et al: A different approach to cysts of the posterior fossa. Pediatr Radiol. 34(9):720-32, 2004
23. Bonneville F et al: Unusual lesions of the cerebellopontine angle: a segmental approach. Radiographics. 21(2):419-38, 2001
24. Davidson HC et al: MR evaluation of vestibulocochlear anomalies associated with large endolymphatic duct and sac. AJNR Am J Neuroradiol. 20(8):1435-41, 1999
25. Koeller KK et al: Congenital cystic masses of the neck: radiologic-pathologic correlation. Radiographics. 19(1):121-46; quiz 152-3, 1999
26. Lau KY et al: MRI demonstration of subarachnoid neurocysticercosis simulating metastatic disease. Neuroradiology. 40(11):724-6, 1998
27. Mukherji SK et al: Papillary endolymphatic sac tumors: CT, MR imaging, and angiographic findings in 20 patients. Radiology. 202(3):801-8, 1997
28. Tong KA et al: Large vestibular aqueduct syndrome: a genetic disease? AJR Am J Roentgenol. 168(4):1097-101, 1997
29. Friedman DP et al: Vascular neoplasms and malformations, ischemia, and hemorrhage affecting the spinal cord: MR imaging findings. AJR Am J Roentgenol. 162(3):685-92, 1994
30. Kollias SS et al: Cystic malformations of the posterior fossa: differential diagnosis clarified through embryologic analysis. Radiographics. 13(6):1211-31, 1993
31. Smirniotopoulos JG et al: Cerebellopontine angle masses: radiologic-pathologic correlation. Radiographics. 13(5):1131-47, 1993

Images

Selected Images

Epidermoid Cyst Axial T1 C+ MR reveals a low signal intensity, nonenhancing epidermoid cyst that insinuates into the foramen of Luschka and along the right cerebellar hemisphere . DWI MR sequence would show restricted diffusion. FLAIR would show lack of complete fluid suppression.

Epidermoid Cyst Axial T1 C+ MR reveals a low signal intensity, nonenhancing epidermoid cyst that insinuates into the foramen of Luschka and along the right cerebellar hemisphere . DWI MR sequence would show restricted diffusion. FLAIR would show lack of complete fluid suppression.

Arachnoid Cyst Axial T1 C+ FS MR demonstrates a right cerebellopontine angle (CPA) cistern arachnoid cyst displacing the proximal facial and vestibulocochlear nerves anteriorly .

Vestibular Schwannoma With Intramural Cyst(s) Axial T1 C+ MR shows a large enhancing vestibular schwannoma projecting from the internal auditory canal (IAC) into the CPA cistern. The tumor has a large intramural cyst that compresses the brainstem and cerebellum.

Vestibular Schwannoma With Intramural Cyst(s) Axial T2 MR shows a heterogeneous CPA mass extending into the left internal auditory canal. Note numerous large intramural tumor cysts .

Hemangioblastoma Axial T1 C+ FS MR shows a superficial, intracerebellar mixed cystic-solid hemangioblastoma projecting into the left CPA cistern area. The solid nodule is avidly enhancing.

Large Endolymphatic Sac Anomaly (IP-II) Axial T2WI MR shows a large endolymphatic sac within the posterior wall of the temporal bone. CT (not shown) would reveal a large bony vestibular aqueduct in this patient with large endolymphatic sac anomaly.

Neurocysticercosis Axial T1 C+ FS MR demonstrates a cystic mass in the right CPA cistern with a peripherally enhancing wall . Adjacent enhancing, thickened meninges are also seen.

Vestibular Schwannoma With Extramural Cyst Axial T2WI MR shows a vestibular schwannoma projecting from the IAC into the CPA cistern. An associated (extramural) arachnoid cyst is visible compressing the brainstem and 4th ventricle .

Facial Nerve Schwannoma in CPA-IAC With Cyst Axial T1 C+ MR reveals an enhancing CPA mass , with intramural cysts, which projected into the IAC but did not involve the labyrinthine segment. Note atrophy of the right platysma muscle from CNVII denervation.

Schwannoma, Trigeminal, Skull Base Axial T1 C+ MR demonstrates a large CPA cystic mass "pointing" toward the Meckel cave , providing a clue to the origin of this mass. Note chronic denervation changes of volume loss and fatty infiltration in the left suprazygomatic masticator space compared to the right , partly seen here.

Neurenteric Cyst Axial T1WI MR shows a small mass anterior to the pontomedullary junction . The neurenteric cyst is well delineated, demonstrating nearly isointense signal to brain, and does not enhance significantly.

Jugular Foramen Schwannoma With Intramural Cyst Axial T2 FS MR reveals a large, sharply marginated lesion expanding the left jugular foramen . The high-signal mass projects medially into the low CPA cistern where it compresses the brainstem .

Cystic Metastasis in CPA Parasagittal T1 C+ FS MR shows a heterogeneous, cystic enhancing mass in the right CPA . Adjacent brain edema is noted . Although the mass might mimic a cystic schwannoma, the presence of a 2nd enhancing mass and a clinical history of lung cancer helps establish diagnosis of metastasis.

Endolymphatic Sac Tumor Axial high-resolution T2 MR shows a heterogeneous cystic CPA mass . The key to diagnosis is identifying the mass origin from the posterior temporal bone in the expected location of the endolymphatic sac.

Additional Images

Vestibular Schwannoma With Extramural Cyst Axial T1 C+ MR shows an atypical heterogeneously enhancing left vestibular schwannoma with an associated arachnoid cyst .

Jugular Foramen Schwannoma With Intramural Cyst Coronal T1 C+ MR shows variant MR case of a jugular foramen schwannoma with intramural cyst and very large cisternal component. The jugular foramen connection is seen on the next image.

Jugular Foramen Schwannoma With Intramural Cyst Coronal T1 C+ MR reveals an enhancing schwannoma in the jugular foramen . The tumor projects superomedially to fill the CPA cistern and compress the brainstem.

Schwannoma, Trigeminal, Skull Base Axial T1 C+ MR in a patient presenting with left facial pain demonstrates a peripherally enhancing cystic mass in the left CPA with a vector of spread extending towards Meckel cave , that was the clue to its origin.

Neurocysticercosis Coronal T1 C+ FS MR shows multiple cysts in the right CPA cistern causing mass effect on the brainstem. Secondary hydrocephalus is present.

Hemangioblastoma Axial T2WI MR reveals an intracerebellar high signal hemangioblastoma projecting into the CPA cistern area. Contrast is required to define enhancing nodule if present.

Jugular Foramen Schwannoma With Intramural Cyst Axial T1 C+ MR demonstrates an ovoid enhancing mass in the low CPA cistern . Multiple intramural cysts suggest the diagnosis of schwannoma. Extension into the jugular foramen is evident.

Epidermoid Cyst Axial T1 C+ MR shows nodular soft tissue enhancement along the margins of a cystic prepontine and left CPA epidermoid cyst , due to a rare complication: Malignant degeneration into squamous cell carcinoma.

Meningioma, Cystic Axial T1 C+ MR shows a partly cystic, partly solid mass in the right CPA and posterior Meckel cave . Biopsy supported meningioma, which rarely may have cystic morphologies that mimic schwannoma.