statdx/docs_md/articles/cpa-mass-child_76d2535b-050d-4826-a344-877e5bae4230.md

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CPA Mass, Child	76d2535b-050d-4826-a344-877e5bae4230	key value d19354f3-7ff2-495a-ad3f-064122e45602 Bernadette L. Koch, MD key value e8af6d26-3aad-47c9-9083-5128aab09af2 Susan I. Blaser, MD, FRCPC	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 CPA Mass, Child cpa-mass-child null	Head and Neck	388e4ad1-934e-45b0-8fc0-80caff2df890	11	03/28/22	CPA Mass, Child	Head and Neck, Differential Diagnosis, CPA-IAC and Posterior Fossa, Anatomically Based Differentials, CPA Mass, Child	CPA Mass, Child | STATdx	CPA Mass, Child	DDX	true	Head and Neck Differential Diagnosis CPA-IAC and Posterior Fossa Anatomically Based Differentials CPA Mass, Child

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title: "CPA Mass, Child" docid: "76d2535b-050d-4826-a344-877e5bae4230" authors:

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ESSENTIAL INFORMATION

• Helpful Clues for Common Diagnoses

  • Arachnoid Cyst in CPA-IAC - Sharply demarcated extraaxial cyst with CSF density/signal intensity - Isointense to CSF on all MR sequences, including complete fluid attenuation on FLAIR images - Nonenhancing - No diffusion restriction

• Helpful Clues for Less Common Diagnoses

  • Vestibular Schwannoma - Ovoid when within internal auditory canal (IAC) - Ice cream on cone shape when CPA-IAC - Hypointense relative to hyperintense CSF on T2 or CISS images, ± intramural cysts - Enhancing, well-circumscribed tumor - Rare in children, unless neurofibromatosis type 2
  • Infratentorial Ependymoma - Heterogeneously enhancing 4th ventricular mass with irregular margins - Extends through foramen of Luschka → CPA cistern - Calcification in up to 50%
  • Infantile Hemangioma in CPA-IAC - Smoothly marginated, intensely enhancing mass in CPA-IAC (proliferating phase) - Proliferating, involuting, and involuted phases - Usually, involutional timing similar to extracranial hemangiomas; therefore, no surgical intervention - Glut-1 marker positive - ± PHACE syndrome - Posterior fossa malformations, hemangioma, arterial cerebrovascular anomalies, coarctation of aorta and cardiac defects, eye abnormalities
  • Epidermoid Cyst in CPA-IAC - Insinuating mass with irregular or scalloped margins - ± scalloping brainstem margin - Iso- to slightly hyperintense to CSF - Nonenhancing, with restricted diffusion

• Helpful Clues for Rare Diagnoses

  • Atypical Teratoid/Rhabdoid Tumor - CPA tumor with lytic bone destruction in infants - Hypointense compared with CSF on T2, with restricted diffusion, enhancing
  • Meningioma in CPA-IAC - Dural-based globular or en plaque mass - Enhancing mass ± dural tail: 23% of CPA meningiomas have extension/dural tail into IAC - Permeative-sclerotic or hyperostotic bone
  • Lipoma in CPA-IAC - Ovoid or broad-based against lateral pons - Fat signal intensity/density on MR and CT - May be mistaken for vestibular schwannoma if T1 C+ images are performed without fat saturation
  • Metastases in CPA-IAC - Irregular, invasive mass; single or multiple - Primarily involves leptomeninges, flocculus, choroid plexus, or dura - Unilateral or bilateral
  • Choroid Plexus Papilloma in CPA - Dumbbell-shaped mass in 4th ventricle, extending through foramen of Luschka → CPA cistern - Avid contrast enhancement

References

Selected References

1. Vernon V et al: Surgical management of cerebellopontine angle epidermoid cysts: an institutional experience of 10 years. Br J Neurosurg. 1-10, 2021
2. Bartindale M et al: Facial schwannoma management outcomes: a systematic review of the literature. Otolaryngol Head Neck Surg. 163(2):293-301, 2020
3. D'Arco F et al: The link between inner ear malformations and the rest of the body: what we know so far about genetic, imaging and histology. Neuroradiology. 62(5):539-44, 2020
4. Giordano M et al: Surgical management of cerebellopontine angle arachnoid cysts associated with hearing deficit in pediatric patients. J Neurosurg Pediatr. 21(2):119-23, 2018
5. 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

Images

Selected Images

Arachnoid Cyst in CPA-IAC Axial T2WI MR in a 3-year-old child demonstrates a moderate-sized right extraaxial CPA cyst , isointense to intraventricular fluid, moderately compressing the right cerebellar hemisphere and midbrain.

Arachnoid Cyst in CPA-IAC Axial T2WI MR in a 3-year-old child demonstrates a moderate-sized right extraaxial CPA cyst , isointense to intraventricular fluid, moderately compressing the right cerebellar hemisphere and midbrain.

Arachnoid Cyst in CPA-IAC Axial T2WI MR in a 3-year-old child demonstrates a moderate-sized right extraaxial CPA cyst , isointense to intraventricular fluid, moderately compressing the right cerebellar hemisphere and midbrain.

Arachnoid Cyst in CPA-IAC Axial FLAIR MR in the same patient demonstrates complete attenuation of signal intensity within the cyst , typical of an arachnoid cyst. There was no diffusion restriction on DW images (not shown), unlike an epidermoid cyst, which typically demonstrates diffusion restriction.

Vestibular Schwannoma Axial T1 C+ MR in a 12-year-old boy shows bilateral enhancing CPA-IAC masses and a well-defined, enhancing mass involving the left 6th cranial nerve , consistent with multiple schwannomas in a child with NF2.

Infratentorial Ependymoma Axial T1 C+ MR in a 2-year-old child demonstrates a large, heterogeneously enhancing posterior fossa mass filling the 4th ventricle, extending through the foramen of Luschka and into the right CPA cistern . Notice extension across the midline toward the left foramen of Luschka .

Infantile Hemangioma in CPA-IAC Axial T1 C+ MR in a 1-year-old infant shows a massive facial hemangioma , a right CPA-IAC hemangioma , and ipsilateral cerebellar hemisphere hypoplasia . These findings are consistent with PHACE syndrome.

Epidermoid Cyst in CPA-IAC Axial T1 C+ MR in a teenager with occipital headaches shows an extraaxial hypointense mass , similar in signal intensity to intraventricular CSF, compressing the pons. Differential diagnosis would include arachnoid cyst or dermoid/epidermoid cyst.

Epidermoid Cyst in CPA-IAC Axial FLAIR MR in the same patient as shows heterogeneous, "dirty" signal intensity within the lesion adjacent to the pons, hyperintense relative to CSF. Incomplete suppression on FLAIR sequences is typical of epidermoid cysts.

Epidermoid Cyst in CPA-IAC Axial DWI MR in the same patient shows hyperintense signal intensity relative to intraventricular CSF, which on ADC map proved to be hypointense (not shown), consistent with restricted diffusion typical of epidermoid cysts.

Additional Images

Arachnoid Cyst in CPA-IAC Axial FIESTA in a teenager with epilepsy shows an incidental left CPA arachnoid cyst , isointense to intraventricular CSF, without mass effect on the cisternal segments of the 7th/8th cranial nerves and without extension into the IAC.

Epidermoid Cyst in CPA-IAC Axial T2WI MR in a teenager with occipital headaches demonstrates an oblong, T2-hyperintense epidermoid cyst , mildly compressing the left ventral pons.

Epidermoid Cyst in CPA-IAC Axial ADC map in the same patient shows hypointense signal on ADC map image consistent with diffusion restriction within the lesion, typical of epidermoid cyst.