intracranial tumors: a radiologic approach

Kenway Louie, HMS IIIGillian Lieberman, MD

Intracranial Tumors: A Radiologic Approach


November 2002

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Our patient R.R.

• 46 y/o woman, with no signficant PMHx, discovered unconscious at home

• 6 mo history of headache, worse at night and early morning

• ? Hx decreasing visual acuity (4-8 mo)

• 1 wk history of nausea/vomiting

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Radiologic anatomy of the brain

http://freud.tau.ac.il/~shakhar/neuro/movies.html http://www.med.harvard.edu/AANLIB/cases/caseM/mr3_t/031.html

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Classification of brain tumors: a framework

** benign vs. malignant distinction less clinically relevant for intracranial tumors(mass effect, infiltration preventing removal, critical location)

brain neoplasm

primary metastatic

extra-axial intra-axial

neuronal glial

meningiomaastrocytomaglioblastomaependymoma

lung (50 %)breast (15%)melanoma (10%)

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Classification of brain tumors: tissue of origin

CATEGORY EXAMPLE

• Tumors of neuroepithelial tissue astrocytoma, glioblastoma, ependymomas• Tumors of peripheral nerves Schwannoma, neurofibroma

• Tumors of meninges meningioma• Lymphomas and hemopoietic neoplasms primary lymphoma of CNS• Germ cell tumors germinoma

• Tumors of sellar region craniopharyngioma, pituitary adenoma

WHO Classification of Tumors of the Central Nervous System (2000)

• Broad categories of tumor nomenclature by tissue of origin• Implied grading scale based on histopathology (I-IV)

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Incidence of brain tumors

http://uptodateonline.com

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Astrocytomas and glioblastomas

• Gliomas comprise the majority of primary CNS tumors

• Histopathological grading: +/- nuclear atypia, mitosis, microvascular proliferation, necrosis

• Astrocytic tumors:- astrocytoma

- anaplastic astrocytoma

- glioblastoma multiforme

• Pathological grading defines treatment and prognosis

astrocytoma

anaplastic astrocytoma

glioblastoma multiformemalignant astrocytomas

DeAngelis LM. Brain tumors. New Engl J Med 2001; 344: 114-23.

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Role of imaging in neurooncology

• Diagnosis- Ddx: tumor vs. infection vs. vascular- Clinical complications: parenchyma compromise, mass effects

• Treatment- Treatment planning- Localization for therapeutic modalities: EBRT, stereotaxic surgery- Evaluation

• Post-treatment surveillance- Tumor recurrence

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Menu of tests for suspected brain tumor

• CT +/- contrast- Quick scan time appropriate for emergent imaging- Low soft tissue delineation limits diagnostic capability- Beam-hardening artifact : can miss structural lesions, esp in

posterior fossa

• MR +/- gadolinium- Procedure of choice for imaging brain tumors- Sensitive for edema- Sensitive for small tumors near bone- Gadolinium-DPTA enhances regions of blood-brain barrier

disruption (T1), increases sensitivity of neoplasm detection

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A brief primer on signal intensity in MRI

XR/CT T1 T2Dense bone bright dark darkAir dark dark darkFat dark gr bright brightWater light gr dark brightBrain light gr ‘anatomic’ int.

XR/CT T1 T2 enhancementInfarct dark dark bright subacuteBleed bright bright bright noTumor dark dark bright yesMS plaque dark dark bright acute

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Differential diagnosis of intracranial masses

• Primary brain tumor• Metastatic brain tumor• Vascular disease

- Aneurysms, AV malformations- Cerebral hemorrhage- Cerebral infarct

• Infection- Abscess- Granulomatous disease- AIDS and associated conditions

• Inflammatory disease• Cyst

Locationintra- vs extra-axial?supra- vs infra-tentorial?WM vs GM?

MultiplicityHeterogeneityEnhancement

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MR characteristics of intracranial masses

• Normal structures• Glioma• Meningioma• Metastases• Abscess• Infarction• White matter disease• Tumor recurrence

http://www.med.harvard.edu/AANLIB/cases/caseM/mr3/032.html

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-- Irregular, dense contrast enhancement-- Ring enhancement common, irregular and

-nodular, often around necrosis-- Infiltrative, can involve WM and cross midline

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- Base of skull (parasellar), cerebral convexities- Adjacent to bone, ‘dural tail’- Characteristic diffuse pattern of enhancement- Slow growing, little edema, histologically benign


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- Tends to occur at gray-white junction- Multifocality in > 50%- Smooth ring-like enhancing rim, necrotic center - Large amounts of vasogenic edema

Gilman S. Imaging the brain. Second of two parts. New Engl J Med 1998; 338: 889-96.

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- Clinically more acute Hx with fever- Ring enhancing lesion, thin rim with uniform

-enhancement- Accompanying mass effect and edema- Can appear similar to necrotic tumors

http://www.xraydoor.com/image/shenjing/pic/nnz5.jpg

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- DWI/PWI T2 imaging in the acute stroke setting- T1 contrast enhancement over days s/p infarct,

-does not acutely enhance- Irregular serpiginous enhancement following

-cortical surface of lobar infarcts- Enhancing abnormality will resolve (6-8 wks)

http://www.med.harvard.edu/AANLIB/cases/case20/mr3/015.html

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-- Multiple lesions in periventricular white matter-- Hypointense on T1, hyperintense on T2-- T2 images extremely sensitive for MS plaques

http://www.med.harvard.edu/AANLIB/cases/case5/mr11/036.html

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- Hyperenhances for several months s/p resection -surgery (hypervascularity, lack of BBB)

- After ~6 mo, hypovascular gliosis should be -hyperintense on T2 and nonenhancing on T1

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Our patient R.R.: CT

CT CT +I

Midline R->L shiftHypodense R occipital/temporal mass and edema

Images courtesy of Chad Brecher, MD

BIDMC BIDMC

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T2

Our patient R.R.: MR +/- gadolinium

T1 post

Contrast enhancing lesionExtensive surrounding edema

Crosses midline at splenium (cc)


BIDMC BIDMC

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Our patient R.R.: diagnosis?• Clinical hx (HA, N/V) c/w raised ICP

• CT: hypodense mass and evidence of significant edema

• MR: large diffuse R temporal lobe mass with extensive temporal, occipital, parietal lobe edema

• MR: multiple necrotic foci within mass

• MR: lesion appears to cross midline at splenium of corpus callosum

Malignant astrocytomaconfirmed on surgical biopsy as III/IV anaplastic astrocytoma

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• Treatment- Treatment planning- Localization for therapeutic modalities: EBRT, stereotaxic surgery- Evaluation


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Evaluation of brain herniation

Types of brain herniation

1) Cingulate

2) Central transtentorial

3) Uncal transtentorial

4) Upward cerebellar

5) Cerebellar tonsillar

6) Transcalvarial

Kaye AH and Laws ER (eds), 2001.

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Uncal herniation

http://medlib.med.utah.edu/WebPath/CNSHTML/CNS057.html

• Medial and downward displacement of basal uncal edge and hippocampal gyrus into posterior fossa

• Occurs most often with temporal lobe or middle fossa tumors

• Midbrain effects: contralateral cerebral peduncle, ipsilateral CN III

BIDMC

BIDMC


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Our patient R.R.: clinical findings

Ventricular compression Uncal herniation

Images courtesy of Chad Brecher, MDBIDMC BIDMC

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• Treatment- Treatment planning- Localization for therapeutic modalities: EBRT, stereotactic surgery- Evaluation


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Additional diagnostic neuroimaging

• MR spectroscopy• SPECT• PET• Echo planar MR (fMRI)

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MR spectroscopy

• USE:

- Detection of tumor infiltration outside border of MR contrast enhancement

- Histopathological grading

• Nuclear magnetic resonance (NMR) spectroscopic analysis of chemical composition in designated area of interest

• Only select compounds detected by H1-MRS, importantly:

- N-acetylaspartate (NAA)

Byproduct of neurotransmitter glutamate, signals neuronal presence

Decreased in gliomas

- Choline

Component of cell membranes

Increased in tumors, may be related to altered membrane turnover

• Pathological spectra: NAA/choline ratios < 1

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MR spectroscopy

Woodruff WW. Fundamentals of neuroimaging. Philadelphia: W. B. Saunders 1993.

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Single photon emission computed tomography (SPECT)

• USE:

- Preoperative diagnosis of nonmalignant vs. malignant brain lesions

- Histopathological grading

- Localizing areas of maximum uptake for biopsy

• Single photon scintigraphy using Thallium-201, a measure of perfusion and uptake

• Correlation between early and delayed tumor uptake and subsequent surgically-determined tumor grade

• Not as useful as FDG-PET in distinguishing between radiation necrosis and tumor recurrence

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Single photon emission computed tomography (SPECT)

T2 SPECT-TI

http://www.med.harvard.edu/AANLIB/

• 51 y/o woman L parietal anaplastic astrocytoma• High thallium uptake indicative of tumor recurrence• Lg region of mixed signal on T2, only subset corresponds to tumor

http://www.med.harvard.edu/AANLIB/cases/case1/mr1/034.gif

http://www.med.harvard.edu/AANLIB/cases/case1/mr1-tl4/034.gif

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Positron emission tomography (PET)

http://www.med.harvard.edu/AANLIB/cases/caseSLU2/mr1-dg2/012.html

• 53 y/o man R parietal-occipital grade IV astrocytoma• s/p focused external beam radiation therapy• FDG-PET shows increased glucose metabolism 3 mos later, indicating

tumor recurrence rather than radiation necrosis

T = 0 T = 3 mos

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Our patient R.R.: clinical course• 5/00 - Initial presentation

- Diagnosed with anaplastic oligoastrocytoma grade III/IV- Underwent surgical debulking -> partial resection

• 6/00 - Post-surgical followup- Began involved-field external beam radiation therapy

• 8/00 - Preevaluatiion for chemotherapy- Favorable response to irradiation, mass effect resolved- Scheduled to start multiple cycle PCV

• 6/01 - Recurrent tumors and increasing headaches- Surgical redebulking of tumor

• 1/02 - Post-chemotherapy followup- Clinically stable, but enlargement of tumor into surgical cavity- MR spectroscopy: increase choline:NAA ratio- New chemotherapy regimen started: CPT-11

• 10/02 - Stable followup

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5.23.00 s/p craniotomy and partial surgical resection

BIDMC

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8.7.00 3 mos s/p partial resection, focused EBRT

BIDMC BIDMC

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6/11/01 s/p surgical redebulking

BIDMC

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1.7.02 clinically stable, radiologic evidence of tumor recurrence

BIDMC BIDMC

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10.11.02 clinically stable, radiologic evidence of tumor recurrence

BIDMC

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Summary

• Initial neurologic imaging exam guided by history and clinical suspicion

• CT applicable if concern for intracranial bleed

• MRI is the diagnostic modality of choice for the evaluation of suspected intracranial neoplasms

• Additional functional imaging (MR spectroscopy, Th201-SPECT, and FDG-PET) may improve diagnostic capability, currently not used for initial diagnosis

Leeds NE and Taveras JM. 1969.

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References

• Atlas SW. Adult supratentorial tumors. Semin Roentgenol 1990; 25: 130-54.• DeAngelis LM. Brain tumors. New Engl J Med 2001; 344: 114-23.• Gilman S. Imaging the brain. First of two parts. New Engl J Med 1998; 338: 812-20.• Gilman S. Imaging the brain. Second of two parts. New Engl J Med 1998; 338: 889-96.• Hesselink JR and Press GA. MR contrast enhancement of intracranial lesions with Gd-DTPA.

Radiol Clin North Am 1988; 26: 873-87.• Johnson KA and Becker JA. The Whole Brain Atlas. http://www.med.harvard.edu/AANLIB/• Kaye AH and Laws ER (eds). Brain tumors: an encyclopedic approach (2nd ed). New York:

Churchill Livingstone 2001.• Leeds NE and Taveras JM. Dynamic factors in diagnosis of supratentorial brain tumors by

cerebral angiography. Philadelphia: W. B. Saunders 1969.• Lindsay KW, Bone I, and Callander R. Neurology and neurosurgery illustrated. Philadelphia:

Churchill Livingstone 1997.• Reeder MM. Reeder and Felson’s gamuts in radiology: comprehensive lists of roentgen

differential diagnoses (3rd ed). New York (Springer-Verlag) 1993.• UpToDate. http://uptodateonline.com• Woodruff WW. Fundamentals of neuroimaging. Philadelphia: W. B. Saunders 1993.

http://www.med.harvard.edu/AANLIB/

http://uptodateonline.com/

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Acknowledgements

• Chad Brecher, MD• Larry Barbaras and Cara Lyn D’amour, our Webmasters• Pamela Lepkowski• Gillian Lieberman, MD

intracranial tumors: a radiologic approach

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