pediatric brain tumors dr. muhammad bin zulfiqar

Infratentorial Pediatric Brain Tumors

Dr. Muhammad Bin Zulfiqar PGR IV FCPS SHL / SIMSradiombz@gmail.com

AIMS• Brief Introduction of MRI Sequences• Posterior Fossa Tumors • Most Common Posterior Fossa Tumors

Commonly Used Sequences In Brain• T1WI• T2WI• FLAIR (Fluid Attenuation Inversion Recovery)• DWI• ADC MAP• GRE sequence• MR Spectroscopy

• T1WI• T2WI• FLAIR (Fluid Attenuation Inversion Recovery)• CE T1WI

• DWI• ADC MAP• GRE sequence

MR spectroscopy• MR spectroscopy (MRS) allows tissue to be interrogated for the

presence and concentration of various metabolites. • May help in improving our ability to predict histological grade.• lactate: resonates at 1.3 ppm• N-acetylaspartate (NAA): resonates at 2.0• creatine: resonates at 3.0 ppm• choline: resonates at 3.2 ppm

ppm—Parts per million

MRS In Tumors

Posterior Fossa Tumors

Brainstem

Tectum /CerebellumFourth VentricleCP angle

Tectum / CerebellumFourth Ventricle

CP Angle

Pilocytic astrocytomaMedulloblastomaHemangioblastoma

MedulloblastomaEpendymomaChoroid Plexus Papilloma

Acoustic neuromaMeningiomaChoroid plexus papillomaEpidermoid Cyst

Brainstem

• Glioma• Ganglioglioma• Astrocytoma

Tectum / Cerebellum

• Pilocytic astrocytoma• Medulloblastoma• Hemangioblastoma

Fourth Ventricle

• Medulloblastoma• Ependymoma• Choroid Plexus Papilloma

CP Angle

• Acoustic neuroma• Meningioma• Choroid plexus papilloma• Epidermoid Cyst

Most Common Tumors • Pilocytic Astrocytoma• Medulloblastoma• Ependymoma• Brainstem Glioma• NF2• Schwanoma• Meningioma

• Epidermoid Cyst• Arachnoid Cyst

Posterior Fossa Tumors—CF• Developemental delay• Sleepiness• Nausea and vomiting (area postrema)• Truncal or gait ataxia• Head tilt• Cranial nerve palsies• Macrocrania

Medulloblastoma• Most common pediatric CNS malignancy(25%)• Peak incidence 5-9 years (75% under 10years)• M>F 3:1• Fourth ventricle obstruction leads to hydrocephalus• Present with headache, ataxia and vomiting• Macrocephaly if have open sutures• Cranial nerve abnormalities uncommon.

Medulloblastoma—Imaging features• Originates from the roof of the 4th ventricle• Superior medullary velum or inferior vermis at the level of posterior velum

medullaris

• Cleavage plane between mass and 4th ventricle• Hyperdense to gray matter on CT (90%)• Hypo / isointense to gray matter on T2WI• >90 % enhance (relatively homogeneously)• Mildly restricted diffusion.

CT and MRI of medulloblastoma.

• CT demonstrates a hyperdense lesion with eccentric calcifications encompassing 4th ventricle.• MRI demonstrates a mass centered on the roof of the fourth

ventricle. It enhances heterogeneously but vividly and has restricted diffusion on DWI consistent with high cellularity. There is evidence of extensive leptomeningeal spread.

• Proton MR spectroscopy image showing prominent choline peak in a mass arising from roof of 4th ventricle---- Medulloblastoma.

CT and MRI of medulloblastoma.

Classical Medulloblastoma—Leptomeningeal spread

Medulloblastoma with anaplastic features

Medulloblastoma with extensive nodularity

DDX for Medulloblastoma• Ependymoma is usually more heterogeneous with calcifications and

hemorrhage, extends out of the 4th ventricle.• Juvenile pilocytic astrocytoma is usually hemispheric with cystic and

nodular component.• Brainstem glioma location is main differentiating point.• Atypical rhabdoid tumor can be indistinguishable by imaging but are

usually younger (< 3 years old), often more heterogeneous.

Infratentorial Ependymoma• Clinical features• Third most common posterior fossa tumor after medulloblastoma and

brainstem glioma (15% Infratentorial tumors in kids)• Usually older than medulloblastoma• Peak incidence 1-5 years, but may present as adolescent

• More subacute and prolonged presentation than medulloblastoma• Younger age associated with worse prognosis.

Infratentorial Ependymoma• Plastic tumor arising from floor of the 4th ventricle• Extends through foramen of luschka and magendie

• Calcifications (50%)• Cysts and hemorrhage common• Heterogeneous enhancement• No restricted diffusion

Infratentorial Ependymoma

• MRI demonstrates a large heterogeneous mass centred in then fourth ventricle and herniating out of the left foramen of Luschka and magendi. It is mostly isointense to the adjacent cerebellum on T1 weighted images, hyperintense on T2 (with areas of higher signal / cystic change), and without significant restricted diffusion. Post contrast images demonstrate vivid but heterogeneous contrast enhancement.

• There is no surrounding oedema, and although the fourth ventricle is effaced there are no features to suggest significant hydrocephalus on the images provided.

Infratentorial Ependymoma

Infratentorial Ependymoma

Cerebellar pilocytic astrocytoma• Middle aged child 5-15 years old • > 80 % under 20

• Prolonged duration of symptoms—years• Headache, nausea, vomiting• Visual loss (optic pathway)• Ataxia / cerebellar signs.

Cerebellar pilocytic astrocytoma• Location

• Cerebellum (60%) > optic nerve chiasma (25-30%) > near 3rd ventricle > brainstem

• Cyst and enhancing mural nodule• > 95 % enhance

• 50 % cyst and enhancing mural nodule• 40 % solid lesion with heterogeneous enhancement and necrotic center• 10 % solid homogeneous enhancement

• Cyst contents usually bright on T2• Leptomeningeal mets rare.

Cerebellar pilocytic astrocytoma

• MRI shows heterogeneous cystic mass with mural nodule hypointense on T1WI, Hperintense on T2WI with surrounding edema and mural nodule shows avid enhancement on Postcontrast images.

Cerebellar pilocytic astrocytoma

Cerebellar pilocytic astrocytoma

Brainstem gliomas• 15 % of all brain tumors.• 25-30 % of all brain tumors in chidren.• Most are low grade astrocytoma• Predominantly in the pons• Less frequently in the medulla• May infiltrate extensively throughout the brainstem.

Brainstem glioma—clinical• Subtyped by location• Location• Tectal• Mesencephalic• Pontine (most common location)• Medullary

• Tectal gliomas and NF associated tumors are distinct entities.

Brainstem glioma—clinical• Peak incidence 3-10 years• M=F• Most have poor prognosis• JPA, NF1 associated and tectal glioma have good prognosis

• Median survival 1 year, 20 % survival at 2 years• Tx—radiation therapy only.

Brainstem glioma—Imaging features• T2 hyperintense, T1 low to isointense• Enhancement variable, associated with higher grade tumors and

worse prognosis• DWI usually not restricted, worse grade and prognosis if positive.• May encase basilar artery, without narrowing it• Beware the effects of steroid therapy on enhancement characteristic.

Brainstem glioma• MRI shows expansile pons

based T2 hyperintense mass with minimal enhancement on Postcontrast images.

Brainstem glioma

DDX Brainstem glioma• Brainstem / rhombencephalitis—usually febrile• Listeria, herpes, West nile, EBV, etc

• NFI, characteristic increased T2 signal in brainstem, cerebellum, basal ganglia• Increase in childhood, decrease in adolescence

• Histiocytosis • Langehans cell and hemophagocytic lymphohistiocytosis• Look for other sites of disease in brain, meninges, pituitary and skull.

• Acute disseminated encephalomyelitis (ADEM)

DDX of Posterior Fossa TumorsTumor Age

(yrs)Site Commonest

featureTIWI T2WI Post Contrast Diffusion

Restriction

Medulloblastoma 5-9 Roof of 4th ventricle Fast growing, ho fits, cerebellar ataxia

Hypo Variable Heterogeneous,Leptomeningeal

positive

Pilocytic Astrocytoma

5-15 hemispheric Cyst with mural noduleSurrounding edema

Hypo Hyper Mural nodule enhances

No

Brain Stem Glioma 3-10 Pons, midbrainmedulla

Slow growing Hypo Hyper Minimal enhancement usually

No

Ependymoma 1-5 Floor of 4th ventricle Slow growingForamina Ext.

Iso / hypo Hyper with cystic components

Vivid heterogeneous

No

Cerebellopontine angle masses• Acoustic neuroma (60-92%)• Meningioma• Choroid plexus papilloma• Epidermoid Cyst

Acoustic Neuroma• Comprises 60-92 % of CPA lesions.• Usually unilateral• Arise from schwann cells, commonly within IAC.• Occur with equal frequency on the superior and inferior vestibular

nerves.• Greatest density of S. cells at scarpa ganglion.• Majority of cases are sporadic.• Rarely on Cochlear division of the 8th CN.

Acoustic Neuroma• NF2:• Genetic defect on long arm of chromosome 22.• Autosomal dominant.• Bilateral or early in life.• Associated with intracranial meningiomas and spinal cord tumors.• Tumors suppressor gene is absent.

Features• Centered on porous acousticus• Acute angles to petrous bone• Often involves the IAC• Homogeneous enhancement• No dural tail• No calcifications

Acoustic Neuroma MRI Findings.

Meningioma• Second most common CPA lesion 3-7 %• Arise from cap cells near arachnoid villi which are more prominent

near cranial nerve foramina and venous sinuses.• Usually arise from posterior surface of the petrous bone and usually

do not extend to external auditory canal• Ataxia, Nystagmus, facial hyperesthesia

Meningioma• Tumors generally hemispherical with obtuse angles to petrous bone• Dural tail often present (50-75%)• May herniate into middle fossa (50%)• May show calcification (25%)• Pial blood vessels with flow voids may be present at the margins

Meningioma

Acoustic Neuroma Vs Meningioma

DD of Acoustic Neuroma / Meningioma

Features Acoustic Neuroma Meningioma

Site of origin Schwan cells, Internal auditory canal

Posterior surface petrous bone

Angle with petrous bone Acute Obtuse

Internal auditory canal extension Yes No

Dural tail No Yes

Enhancement Intense Intense---Cogwheel / Spiral pattern

Extension to Middle cranial fossa No Yes (50% cases)

Hyperostosis No Yes

Epidermoid Irregularly lobulated Insinuating Common in CP angle, 4th ventricle, supra & parasellar

regions. Intra cerebral < 10% Incorporation during 4-5th week of development. No dermal appendages & hair follicles. Dermoids contain dermal appendages.

Epidermoid Similar to CSF on T1 & T2 High signal in case of white epidermoids Incomplete nulling on FLAIR DWI – Restriction No enhancement, Thin enhancement at the periphery 25% may show rim enhancement White epidermoid – More protein and debris ---- high

signal on T1 & CT.

Epidermoid

• Characteristic appearance of an epidermoid cyst in the cerebellopontine angle. The lesion has similar signal intensity to CSF on both T1 and T2 weighted sequences, but is 'dirty' on FLAIR. The diagnosis is confirmed on DWI which demonstrates very bright signal.

Arachnoid Cyst• Benign intra-arachnoid CSF filled mass• Almost always extraaxial• No restricted diffusion

• MRI show TI, Flair hypo, T2 hyper non enhancing lesion at right cerebellopontine angle (following CSF signals on all sequences) with no diffusion restriction.

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