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1. Barkovich AJ. Pediatric Neuroimaging. 4rd Ed. Philadelphia: Lippincott, Williams and Wilkins, 2005.

2. Castillo M. Neuroradiology Companion. 2nd Ed. Philadelphia: Lippincott, Williams and Wilkins, 1998.

3. Fischbein NJ, Dillon WP, Barkovich AJ. Teaching Atlas of Brain Imaging. New York: Thieme, 2000.

4. Gean AD. Imaging of Head Trauma. New York: Raven, 1994.

Table 8. Common extra-axial masses

Mass

Location

Imaging Appearance

Other Features

Figures

Arachnoid cyst

Posterior fossa Sylvian fissure Middle cranial fossa Suprasellar region

Homogeneous, isodense and isointense to CSF

No enhancement

Mass effect may be present

Longstanding cysts cause bone remodeling

Non-neoplastic

14

Choroid plexus tumors

Intraventricular, along choroid plexus; most commonly in ventricular trigone

Lobulated mass Intense enhancement

Papilloma: iso- or hyperdense, and T1 -isointense and JT2 SI Carcinoma: heterogeneous; invade parenchyma and cause edema Hydrocephalus

Feeding vessels often visible on post-contrast sequences

15

Epidermoid

Most commonly in CP angle, pineal region, suprasellar region and middle cranial fossa

Hypodense, lobulated mass T1 and T2-isointense to CSF Hyperintense on FLAIR and DWI No enhancement

Rupture can lead to chemical meningitis

Dermoid

Often midline Most commonly in vermis, fourth ventricle, or pineal region

Fat-density mass Heterogeneous T1 and T2 SI

|T1 SI related to fat elements, which become hypointense on fat saturated sequences. No enhancement

If midline, evaluate for dermal sinus tract Rupture can lead to chemical meningitis

f = increased; J = decreased; CP = cerebellopontine; CSF = cerebrospinal fluid; DWI = diffusion-weighted imaging; FLAIR = attenuated inversion recovery; SI = signal intensity

Table 8. Continued

Mass

Location

Imaging Appearance

Meningioma

Schwannoma

Teratoma

Along dura, including talx and tentorium

Along cranial nerves, most commonly the 8th cranial nerve

Pineal region Third ventricle Midline posterior tossa

Isodense; lso-T1 and |T2 Homogeneous enhancement

Frequently have characteristic "tail" of dural thickening and enhancement Iso- or hypodense mass T1 -isointense and |T2 SI Prominent enhancement Large tumors can have cystic degeneration Enlarged neural foramina, e.g., internal auditory canal in vestibular schwannomas

Heterogenous mass with fat and calcium Heterogeneous T1 and T2 SI; |T1 SI due to fat Variable enhancement

Very rare in children

Associated with NF2

Bilateral tumors associated with NF2

Most are benign, but few can be highly malignant

f = increased;NF2 = neurofibromatosis type ; SI = signal intensity

Figure 14. Arachnoid cyst. Homogeneous extra-axial collection along the left medial superior frontal lobe. Isointense to CSF. (sagittal T1-WI; axial T2-WI)

Figure 15. Choroid plexus papilloma in the fourth ventricle. Noncommun-icating hydrocephalus with dilation of the temporal horns of the lateral ventricles. (transaxial T1-WI with contrast)

Table 9. Posterior fossa tumors

Tumor Type Location Imaging Appearance Other Features Figures

Table 9. Posterior fossa tumors

Tumor Type Location Imaging Appearance Other Features Figures

Astrocytoma

Cerebellum, 40%

Juvenile pilocytic astrocytomas (JPA): cyst with enhancing

Most common pediatric

18

Cerebrum, 40%

mural nodule(s), or solid enhancing mass

brain tumor

Brainstem, 20%

Higher grade astrocytomas are more heterogeneous and mixed

Most cerebellar

in density and enhancement; can be cystic and necrotic

astrocytomas are JPA

Atypical

Cerebellum

Mimics medulloblastoma mixed ependymoma

Earlier age of presentation

19

teratoid /

Less commonly, in

Variable pattern of enhancement

(<2 years) than

rhabdoid

cerebrum, pineal

medulloblastoma

tumor

region mixed

(~6 years)

hypothalamus

Poor prognosis

Brainstem

Pons

Hypodense mass

Differential diagnosis:

20

glioma,

Diffuse: >50% maximum

|T1 and ]J2 SI

abscess, encephalitis,

diffuse

involvement of

Heterogeneous enhancement

demyelination,

brainstem in transaxial

Expands brainstem and can be exophytic

Langerhans' cell

plane

Hydrocephalus with obstruction of aqueduct or fourth

histiocytosis, vascular

ventricle

malformation

Brainstem

Medulla, tectum

Medullary tumors usually enhance uniformly

Medullary tumors are

21

glioma,

Focal: <50% brainstem

Tectal gliomas are discrete, do not enhance, present with

usually JPA

tocal

involvement, margins

hydrocephalus

Tectal gliomas are

usually well defined

grade I

Î = increased; J = decreased; SI = signal intensity

Î = increased; J = decreased; SI = signal intensity

Table 9. Continued

Tumor Type

Location

Imaging Appearance

Other Features

Figures

Ependymoma

Int'ratentorial, 70% Supratentorial, 30%

Iso- or hyperdense mass JT1 and heterogeneous T2 SI Enhancement

Frequent calcification and cysts Hydrocephalus

Commonly involve floor of the fourth ventricle and extend into foramina of Luschka and Magendie Can present with subarachnoid seeding

22

Hemangio-blastoma

Cerebellum or brainstem

Enhancing nodule with associated flow voids and frequently a nonenhancing cystic component

Associated with von Hippel-Lindau disease

23

Medullo-blastoma (Posterior tossa PNET)

Vermis and roof of fourth ventricle, vermis in children Cerebellar hemispheres in adolescents

Hyperdense, heterogeneous mass JT1 and iso- or JT2 SI Can either enhance or not Occasional calcification Hydrocephalus

Most common pediatric posterior fossa tumor Spread through the subarachnoid space

24

f = increased; J = decreased; PNET = primitive neuroectodermal tumor; SI = signal intensity f = increased; J = decreased; PNET = primitive neuroectodermal tumor; SI = signal intensity

Figure 18. Cerebellar juvenile pilocytic astrocytoma. Small enhancing nodule in the cerebellum without prominent flow voids. Mild mass effect. (transaxial T1-WI with contrast, and T2-WI)
Figure 20. Diffuse brainstem glioma. Tl-hypointense and T2-hyperintense intra-axial mass involving most of the midbrain and pons. (transaxial T1-WI with contrast, and T2-WI)
Figure 22. Ependymoma. Heterogeneous enhancing T1-hypointense and T2-hyperintense mass in the fourth ventricle. The tumor extrudes through the foramen magnum. (transaxial T2-WI, and sagittal T1-WI with contrast)
Figure 23. Hemangioblastoma. Irregular, strongly enhancing mass in the cerebellum. Cysts present. Prominent flow voids seen on transaxial T2-WI. (transaxial T1-WI with contrast, T2-WI)
Figure 24. Medulloblastoma. Heterogeneous Tl-hypointense and T2-hyperintense mass inseparable from roof of the fourth ventricle. (transaxial T1-WI, and sagittal T2-WI)

Table 10. Supratentorial intra-axial tumors

Tumor Type

Location

Imaging Appearance

Other Features

Figures

Astrocytoma

Ependymoma

Dysembryoplastic neuroepithelial tumor (DNET)

Ganglioglioma

Cerebrum, 40% Cerebellum, 40% Brainstem, 20%

Juxtaventricular, off midline Frontal > parietal > temporal lobes

Cortical; frontal > temporal lobes » remainder of cerebrum

Peripheral cerebrum, temporal lobes

Oligodendroglioma Frontal > temporal lobes

Primitive neuroectodermal tumor (PNET)

Cerebrum or in lateral ventricle

Intra-axial mass with J,T1 and fT2 SI Variable enhancement

Higher grade astrocytomas are more heterogeneous and have varying patterns of enhancement Can have cystic and necrotic components JPA: cyst with enhancing mural nodule(s), or solid enhancing mass Iso- or hyperdense mass J,T1 and heterogeneous T2 SI Enhancement

Frequent calcification and cysts

Well-defined lobulated mass

Hypodense

JT1 and fT2 SI

Can be partially cystic

Variable enhancement

Frequent calcification

Iso- or hypodense

Variable T1 and fT2 SI

Variable enhancement

Minimal mass effect and edema

Frequent calcification and cysts

Iso- or hypodense

JT1 and fT2 SI

Variable enhancement

Large well-defined homogeneous or heterogeneous mass

Hyperdense solid components

Variable T1 and T2 SI

Heterogeneous enhancement

Frequent calcification, cysts and necrosis

Most common 25

pediatric brain tumor

Usually are close to ependymal surface CSF metastases are common Benign histology Seizures

Can be adjacent to cortical dysplasia

Rare, slow growing 26

Seizures Associated with mesiotemporal sclerosis Rare, slow growing Seizures

Rare; usually occur 27

<5 years age CSF and distant metastases possible f = increased; J = decreased; CSF = cerebrospinal fluid; JPA = juvenile pilocytic astrocytoma; SI = signal intensity fk * W

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