Transcript Paeds brain tumour

Approach to imaging based
diagnosis of an intracranial
space-occupying lesion in a
child
Dr. Flip Otto
Dept Diagnostic Radiology
UFS
Introduction
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CNS tumours 2nd most common after leukemia
Incidence 2.4:100,000 children <15 years
15% of all paediatric neoplasms
15-20% of all primary brain tumours
M>F
Usually presents with signs and symptoms of raised
intracranial pressure and/or increasing head size
Approach – Clues to diagnosis
• Age
• Location
• Local tumour spread
• Solitary or multifocal
• Specific imaging characteristics
• Tumour mimics
Age
• CNS tumours presenting at birth:
• Teratoma (commonest)
• Neuro-epithelial tumours:
• Medulloblastoma
• Astrocytomas
• Ependymomas
• Choroid plexus tumours
• After 2 months, neuro-epithelial tumours more common.
• During this time, supratentorial tumours more common
than infratentorial
Age
• Brain tumours in infants <2 years
• Two thirds are supratentorial
• Most common tumours:
• PNET (primitive neuroectodermal tumour)
• Astrocytoma
• Teratoma
• Choroid plexus papilloma
Most common CNS tumours in
paediatric patients older than 2
years
• Number of infratentorial tumours slightly exceeds
supratentorial tumours
• Medulloblastoma
• Astrocytoma
• Ependymoma
• Craniopharyngioma
• Gliomas
• Metastases are rare in paediatric population (vs. 50% in
adults)
Location
• Intra- vs. extra-axial
• Supra- vs. infra-tentorial
• White matter vs. cortical based
• Specific anatomic sites:
• Sella/suprasellar
• Pineal region
• Intraventricular
Intra- vs. extra-axial
• Signs of extra-axial location:
• CSF cleft
• Displaced subarachnoid blood vessels
• Cortical grey matter between mass and white matter
• Displacement and expansion of subarachnoid space
• Broad dural base
• Bony reaction
• >80% extra-axial tumours are either meningioma or
schwannoma
Intra-axial vs Extra-axial Brain
Tumours
Intra-axial
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Glioma
Medulloblastoma
Hemangioblastoma
Metastases
Infarction/hematoma
AVM
Abscess/inflammation
Extra-axial
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Meningioma
Pituatary adenoma
Craniopharyngioma
Schwannoma
Chordoma
Dermoid/epidermoid cyst
Lipoma
Metastases, hematoma,
infection
Supra- vs. infra-tentorial
• Common intra-axial CNS tumours in paediatric age group
• Supratentorial:
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Astrocytoma
Pleomorphic xanthoastrocytoma
PNET
DNET
Ganglioglioma
• Infratentorial:
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Juvenile pilocytic astrocytoma
PNET (Medulloblastoma)
Ependymoma
Brainstem astrocytoma/glioma
White matter vs. cortical based
• Most intra-axial tumours are white matter
based
• Differential diagnosis for cortical based
tumours:
• DNET (Dysembryoplastic neuroepithelial
tumour)
• Ganglioglioma
Cortical Based Tumour - DNET
Specific anatomic sites
• Sella/suprasellar:
• Optic pathway/hypothalamic glioma
• Craniopharyngioma
• Germ cell tumours
• Pineal region:
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Germ cell tumours
Pinealblastoma (associated with retinoblastoma)
Astrocytoma
Ganglioglioma
Epidermoid
• Intraventricular:
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Ependymoma
Choroid plexus papilloma/carcinoma
Subependymal giant cell astrocytoma (associated with tuberous sclerosis )
Lesions arising from suprasellar region may involve 3rd ventricle
Colloid cyst (3rd ventricle, usually young adults)
Intraventricular tumours: Choroid
plexus papilloma and carcinoma
Pineal region: Pineal Germinoma
Suprasellar tumour:
Craniopharyngioma
Local tumour spread
• Astrocytomas spread along white matter tracts
and don’t respect lobar boundaries
• Ependymomas in 4th ventricle may extend
through foramen of Magendie into cisterna
magna, and through foramina of Luschka into
cerebellopontine angles
• Subarachnoid seeding: PNET; ependymomas;
choroid plexus carcinoma
Mass effect
• Primary brain tumours usually have less mass
effect and oedema than expected for size, due to
infiltrative growth pattern
• Metastases and extra-axial tumours have more
significant mass effect due to expansile growth
pattern
Solitary vs. multifocal lesions
• Metastases and CNS lymphoma, often presenting with
multiple lesions, are rare in children
• Seeding metastases may be seen with PNET-MB
(Medulloblastoma) and ependymoma
• Multiple brain tumours may occur in phacomatoses:
• NF I: optic gliomas; astrocytomas
• NF II: meningiomas; ependymomas; choroid plexus papillomas
• Tuberous sclerosis: subependymal tubers; ependymomas;
intraventricular giant cell astrocytomas
• Von Hipple Lindau: hemangioblastomas
Specific imaging characteristics
• Fat
• Calcification
• Cystic mass vs. cyst
• T1WI signal intensity
• T2WI signal intensity
• Contrast enhancement
• Advanced MRI
Fat
• Fat is characterised by high signal on T1
and T2WI, with associated chemical shift
artefact
• Fat suppression sequences help distinguish
from other causes of high signal e.g.
melanin, hematoma and slow flow
• Masses containing fat include teratoma,
lipoma and dermoid cyst
Calcification
• Intra-axial:
• Astrocytoma
• Ependymoma
• Choroid plexus papilloma
• Ganglioglioma
• Extra-axial:
• Meningioma
• Craniopharyngioma
Cystic mass vs. cyst
• Cystic lesions that may simulate tumours include epidermoid,
dermoid, arachnoid, neurenteric and neuroglial cysts
• To differentiate cystic masses from cysts:
• Morphology
• Fluid/fluid level
• Content intensity compared to CSF on T1, T2 and FLAIR
sequences
• Restricted flow on DWI
T1WI signal intensity
• Most brain tumours have low to intermediate
signal intensity on T1WI
• High T1 signal may be due to:
• Methaemoglobin in a haemorrhagic tumour
• High protein content eg neurenteric cyst,
dermoid cyst
T2WI signal intensity
• Most brain tumours appear bright on T2WI due to high
water content
• Causes for low signal on T2:
• Hypercellular tumours with high nuclear-cytoplasmic
ratio : PNET, meningioma, germinoma
• Calcifications
• Hemosiderin in old haematomas
• High protein content e.g. colloid cyst
• Flow voids e.g. haemangioblastoma
Contrast enhancement
• Extra-axial tumours, pituitary, pineal and choroid
plexus tumours enhance (outside blood-brain
barrier)
• Contrast enhancement does not visualise full
extent of infiltrative tumours eg gliomas
• In gliomas, enhancement indicates higher degree
of malignancy
• Ganglioglioma and pilocytic astrocytomas are
exceptions, low grade tumours that enhance
vividly
Contrast enhancement
patterns
• No enhancement:
• Low grade astrocytoma
• Cystic non-tumoral lesions
• Homogeneous enhancement
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Germinoma and other pineal tumours
Pituitary adenoma
Pilocytic astrocytoma(solid component) and haemangioblastoma
Ganglioglioma
Meningioma, schwannoma
• Patchy enhancement
• Radiation necrosis
• Ring enhancement
• High grade glioma
• Metastases
• Abscess
Advanced MRI techniques
• Diffusion weighted imaging
• Diffusion tensor imaging
• Perfusion weighted imaging
• Magnetic resonance spectroscopy
Application of Advanced MRI in
Paediatric Brain Tumours
• Improving the accuracy of the initial diagnosis
• Evaluating the risk at initial diagnosis
• Monitoring the effectiveness of therapy
DWI
• Most tumours do not show significant restriction
of diffusion
• High signal on DWI is seen with abscesses,
epidermoid cysts and acute infarction
DWI
PWI
• Signal intensity depends on vascularity, not on
breakdown of blood-brain barrier
• Better correlation with grade of malignancy than
degree of contrast enhancement
PWI
MRS
• H-1 MRS analyzes signal of protons attached to
other molecules
• Output is collection of peaks at different
radiofrequencies, representing proton nuclei in
different chemical environments, proportional to
number of contributing protons.
• Peaks include: N-acetylaspartate; choline;
creatine; myo-inositol; taurine; lactate; methyl
groups(lipids); methylene groups
MRS
Tumour mimics
• Abscesses can mimic metastases
• Multiple sclerosis can present with mass like lesions with
enhancement (tumefactive MS)
• Aneurysms should always be excluded in the parasellar region
Conclusion
• Primary CNS tumours relatively common in children
• Age of child helps narrow differential diagnosis
• Anatomical localization very important
• CT and MRI findings characterize tumour
composition
• Advanced MRI techniques can aid in diagnosis,
grading and monitoring treatment response
References
• Daehnert, W. Radiology Review Manual 6th ed. Philadelphia:
Lippincott Williams & Wilkins; 2007.
• Panigrahy, A., Blueml, S.(2009) Neuroimaging of Paediatric
Brain Tumors: From Basic to Advanced Magnetic Resonance
Imaging (MRI). Journal of Child Neurology. 24(11),1342-1365.
• Smithuis, R., Montanera, W. Brain Tumor - Systematic
Approach. www.radiologyassistant.nl
• Weisleder, R, Wittenberg, J, Harisinghani, MG, Chen, JW.
Primer of Diagnosic Imaging 5th ed. St. Louis: Elsevier Mosby;
2011.