Brain tumors in MRI Dr Aminur Rahman FCPS

Brain tumors in MRI Dr. Aminur Rahman FCPS (Med), MD(Neuro) , FINR (Switzerland), MACP (USA) Fellow Interventional Neuroradiology (Thailand) Assistant Professor Department of Neurology Sir Salimullah Medical College

Brain tumors

Epidemiology • Incidence: 8 -25/ 100. 000 • 2. reason of the death • Metastasis – ¼ of all tumors

Etiology • Genetical predisposition • Hereditary factors – m. Recklinghausen (also brain tumors), tuberous sclerosis. . . ) • Viral infections: Epstein-Barr virus - primary brain lymphoma • Environmental factors: pesticides, chemicals, RAT

Brain tumors classification

Primary tumors of the brain • Gliomas – Lowest grade tumors • Pilocytic astrocytoma • Subependymal giant cell astrocytoma • Protoplasmic astrocytoma • Ganglioma • Xanthomatous astrocytoma • Subependymoma – Lower grade malignancies • Fibrillary (gemistocytic, protoplasmic) astrocytoma • Ependymoma • Oligodendroglioma • Mixed oligo-astrocytoma • Optic nerve glioma

Primary tumors of the brain contd. . – Higher-grade malignancies • Anaplastic astrocytoma • Anaplastic oligodendroglioma • Anaplastic mixed glioma – Highest-grade malignancies • Glioblastoma multiforme • Gliosarcoma • Gliomatosis cerebri

Primary tumors of the brain contd. . • Meningioma – Benign – Atypical – Malignant • Primitive neuroectodermal tumors (PNET) – Medulloblastoma – Ependymoblastoma – Pineoblastoma • Pituitary tumors – – Pituitary adenoma Pituitary carcinoma Craniopharyngioma Rathke's cleft cyst

Primary tumors of the brain contd. . • Pineal Tumors – Pineal cyst – Pineocytoma – Pineoblastoma – Germinoma – Mixed germ cell tumor – Pineal gliomas – Pineal teratoma

Primary tumors of the brain contd. . • Choroid plexus tumors – Choroid plexus papilloma – Choroid plexus carcinoma • Others, ( benign primary tumors) – Neurocytoma – Dysembroplastic neuroepithelial tumor (DNT) – Lipoma – Hemangioblastoma – Hamartoma – Teratoma

Primary tumors of the brain contd. . • Tumors of nerves and/or nerve sheaths -Neuroma -Schwannoma -Neurofibroma • Cysts – Colloid cyst – Arachnoid cysts – Dermoid – Epidermoid – Rathke's cleft cyst – Pineal cyst

Primary tumors of the brain contd. . • Other primary tumors, including skull base – Chondroma – Chordoma – Sarcomas – Gliosarcoma – Chondrosarcoma – Rhabdomyosarcoma • Primary Central Nervous System Lymphoma (PCNSL)

Secondary tumors in brain Originate from malignant tumors located primarily in other organs • Lung • Skin - Malignant melanoma • Kidney - hypernephroma • Breast – breast carcinoma • Colon – colon carcinoma These tumors cells reach the brain via the bloodstream

Common brain tumor in adult • • Metastases(50%). Astrocytomas, Glioblastoma multiforme, Meningiomas, Oligodendrogliomas, Pituitary adenomas and Schwannomas.

Tumors of childhood v 20% of all tumors – tumors of childhood v More frequently malignant than in adults v The most frequent localisation - infratentorial (brainstem, cerebellum)

Common brain tumor in children 1. 2. 3. 4. 5. 6. 7. 8. 9. Brain Stem Glioma Craniopharyngioma Ependymoma Juvenile Pilocytic Astrocytoma (JPA) Medulloblastoma Optic Nerve Glioma Pineal Tumor Primitive Neuroectodermal Tumors (PNET) Rhabdoid Tumor

Benign vs malignant? • According histological structure • Biopsy - (cell atypia, mitotic activity, abnormal mitosis) • Localisation !!! • Benign tumors in brainstem or deep structures – bad prognosis

Analysis of potential brain tumour • Age of the patient • Location: o Intra- versus Extraaxial o Compartment o Midline crossing • CT /MRI charecteristics o Calcification/fat/cystic lesions o T 1/T 2/DWI • Contrast enhancement • Effect on surrounding structures o Mass effect- edema • Solitary / multiple

Incidence of CNS tumors v. One-third are metastatic lesions, v. One third are gliomas and v. One-third is of non-glial origin. • Glioma is a non-specific term indicating that the tumor originates from glial cells like astrocytes, oligodendrocytes, ependymal and choroid plexus cells.

Incidence of CNS tumors cotnd. . • Astrocytoma is the most common glioma and can be subdivided into: o Low-grade pilocytic type, o Intermediate anaplastic type and o High grade malignant- Glioblastoma multiforme (GBM). • GBM is the most common type (50% of all astrocytomas). • The non-glial cel tumors are a large heterogenous group of tumors of which meningioma is the most common.

Age distribution • Specific tumors occur under the age of 2, like o Choroid plexus papillomas, o Anaplastic astrocytomas and o Teratomas. • .

Age distribution • In the first decade : o Medulloblastomas, o Astrocytomas, o Ependymomas, o Craniopharyngeomas and o Gliomas. (metastases are very rare)

Age distribution contd. . In adults: • About 50% of all CNS lesions are metastases. • Other common tumors: o Astrocytomas, o Glioblastoma multiforme, o Meningiomas, o Oligodendrogliomas, o Pituitary adenomas and o Schwannomas.

Age distribution contd. . Older age: • Astrocytomas occur at any age but glioblastoma multiforme is mostly seen in older people.

Age distribution contd. . • Brain tumors are the most common type of childhood cancer after leukemia and lymphoma. • Most of the tumors in children are located infratentorially. • The most common supra- and infratentorial tumors are listed in the table on the left.

Intra- versus Extraaxial • Extra-axial tumours ( 80% ) : o Meningioma or o Schwannoma. • Intra-axial tumor (20%) : o Metastasis or o Astrocytoma 75%

Sign of Extra axial location • CSF Cleft • Displaced subarachnoid vessels • Cortical gray between mass and white matter • displaced and expand subarachnoid space • Broad Dural base • Bony reaction

Extra axial location of tumour The T 2 W-images show a schwanoma located in the cerebellopontine angle (CPA). This case nicely demonstrates the typical signs of an extra-axial tumor. There is a CSF cleft (yellow arrow). The subarachnoid vessels that run on the surface of the brain are displaced by the lesion (blue arrow). There is gray matter between the lesion and the white matter (curved red arrow).

Extra axial location of tumour Coronal enhanced T 1 WI. Meningioma with dural tail, hyperostosis of adjacent bone and homogeneous enhancement. Another sign of an extra-axial origin are bony changes. Bony changes are seen in bone tumors like chordomas, chondrosarcomas and metastases. They can also be secondary, as is seen in meningiomas and other tumors. On the left an example of a meningioma with a broad dural base and a dural tail of enhancement.

Intra axial location of tumour • MRI resulting in hyperintensity on T 1 and hypointensity on T 2 images suggestive of Melanoma metastasis: • However, there is gray matter on the anteromedial and posteromedial side of the lesion (red arrow). This indicates that the lesion is intra-axial.

Midline crossing • 1. 2. 3. 4. 5. 6. The ability of tumors to cross the midline limits the differential diagnosis. Glioblastoma multiforme (GBM) frequently crosses the midline by infiltrating the white matter tracts of the corpus callosum. Radiation necrosis can look like recurrent GBM and can sometimes cross the midline. Meningioma is an extra-axial tumor and can spread along the meninges to the contralateral side. Lymphoma is usually located near the midline. Epidermoid cysts can cross the midline via the subarachnoid space. MS can also present as a mass lesion in the corpus callosum.

Fat - Calcification - Cyst - High density • Fat has a low density on CT (- 100 HU). • On MR, fat has a high signal intensity on both T 1 - and T 2 WI. • On sequences with fat suppression fat can be differentiated from high signal caused by subacute hematoma, melanin, slow flow etc. • When you see high signal on T 1 WI always look for chemical shift artefact, as this indicates the presence of fat. • Fat within a tumor is seen in o Lipomas, o Dermoid cysts and o Teratomas.

Fat - Calcification - Cyst - High density • High density tumors CT : o Lymphoma, o Colloid Cyst and o PNET-MB (Medulloblastoma).

Calcification

Figure. Non-enhanced CT shows a low-density mass with mural calcifications in the juxtasellar region (A). T 1 -weighted MRI without contrast reveals high signal of the lesion representing its fatty content (B) and hyperintense droplets in the interpeduncular cistern (B), the frontal horns and sulci (C) after subarachnoid rupture. The anterior misregistration of the lipid droplets which appear to lie anterior to the ventricles (C) is a chemical shift artefact along read-out gradient direction.

On the left are images of a tumor with a small calcification. The calcification is not appreciated on the MR images, but is easily seen on CT. The calcification and the extension of the tumor to the cortex are very typical for an oligodendroglioma. D/D: Astrocytoma

Cystic versus Solid • There are many cystic lesions that can simulate a CNS tumor. • These include: epidermoid, arachnoid, neuroenteric and neuroglial cysts. • In order to determine whether a lesion is a cyst or cystic mass look for the following characteristics: o Morphology o Fluid/fluid level o Content usually isointense to CSF on T 1, T 2 and FLAIR o DWI: restricted diffusion

• • • arachnoid cyst • As an arachnoid cyst is filled with CSF that follow CSF on all sequences, including FLAIR and DWI. Tumor necrosis may sometimes look like a cyst, but it is never completely isointense to CSF. On the far left a craniopharyngioma with an enhancing rim surrounding the cystic component. In the middle a neuroenteric cyst with the contents of which have the same signal intensity as CSF. On the right a glioblastoma multiforme (GBM) with a central cystic component. The enhancement in GBM is usually more irregular.

High Intensity on T 1 • Most tumors have a low or intermediate signal intensity on T 1 WI. • Exceptions to this rule can indicate a specific type of tumor. • On the left is a list of causes for T 1 - shortening. • Calcifications are mostly dark on T 1 WI, but depending on the matrix of the calcifications they can sometimes be bright on T 1. • Especially on gradient echo images slow flow can be seen as bright signal on T 1 WI and should not be confused with enhancement. • This is particularly pronounced on gradient echo images.

Primary brain tumors Astrocytoma: o 4 grades: • • • I, II Benign III (Anaplastic Astrocytoma) – Malignant IV (Gliobastoma Multiforme) o Adults o Frontal and temporal lobe. o Rarely in childhood – Pons.

Astrocytoma • A low grade glioma or astrocytoma may show only a low density area (dark area) • whereas high grade gliomas (Glioblastoma) usually show more contrast enhancement (white on the outside) and necrosis in the middle (looks black on the MRI)

Astrocytoma A grade 3 glioma (sometimes called anaplastic astrocytoma) will have less necrosis in the center (compared to a grade 4 or glioblastoma) but still look more abnormal (more enhancement) than a low grade (grade 1 or grade 2).

Astrocytoma Glioblastoma (above- LEFT) looks more necrotic (gray area in the center, which contains dead or necrotic cells) than a low grade glioma (above- RIGHT)

Astrocytoma Malignant Glioma can appear as a complex cystic structure

Astrocytoma Glioblastoma may appear as multiple separate tumors and look metastatic disease (Multicentric glioblastoma)

Gliobastoma multiforme The most malignant tumor of CNS Rapid progression 5. a 6. decade , men 2 x more often Deep part of hemispheres (bazal ganglia, talamus, white matter) • Spreading by CSF, infiltration of corpus callosum, spreadin on the other side, infiltration of meninges) • MTS also outside of CNS • CT scan – cystic, necrosis, heamorrhages • •

Glioblastoma multiforme MRI T 1 weighted T 2 weighted

Glioblastoma multiforme MRI T 2 weighted SPECT

Glioblastoma multiforme

Primary brain tumors Oligodendroglioma The CT shows a mass with calcifications, which extends all the way to the cortex. Although this is a large tumor there is only limited mass effect on surrounding structures, which indicates that this is an infiltrating tumor. The most likely diagnosis is oligodendroglioma. Differential diagnosis includes • Malignant astrocytoma

Neuroepitelial tumors Oligodendroglial tumors • Adults • Frequently with calcifications • Frontal lobe • 5% of CNS tumors • Low % is histological malignant

Neuroepitelial tumors Ependymal cells tumors • 4% of CNS tumors • Adults, children • IV. Ventricle – obstructive hydrocefalus • Spreading by CSF • MTS in CNS

Ependymoma

Neuroepitelial tumors Plexus choroideus tumors • Papiloma or papilocarcinoma • Rare • Childhood • Ventricles • Hydrocefalus

Plexus choroideus tumors MRI histology

Neuroepitelial tumors Neuroectodermal tumors • • Childhood High grade of malignity – MEDULOBLASTOMA 23% of CNS tumors in childhood Vermis, cerebellar hemispheres Rapid progression, compression of CSF athways, intracranial hypertension MTS in brain and outside of CNS – bones, lymphatic nodes

Meduloblastoma

Tumors of the meninges Meningioma • 15% of brain tumors • Localisation - hemisphers convexity, parasagital, n. olfactorius, sella turcica, pontocerebellar angle, tentorium • Benign • Bone usuration or hyperostosis

Meningioma CT MRI T 1 weighted

Meningioma • Parasagital – Monoparesis of contralateral lower extremity or paraparesis • Near bulbus olfactorius – Unilateral anosmia • Near optic nerve – Exoftlamus, monocular blindnsess, ipsilateral mydriasis with absent FR

Meningioma near optic nerve on the right side

Meningioma • Near sphenoidal bone wings – Epileptic seazures, lesion of cranial nerves – process near fissura orbitalis superior • Pontocerebellar angle – Loss of hearing, dizziness, Bells palsy

Brain CT – PCA meningioma

Brain CT - PCA meningioma

Tumors of sellar region • Adenoma, adenocarcinoma • Chiasma opticum compression – bitemporal hemianopsy • Endocrinne lesions • Skull X-ray – enlargment of sella turcica

Tumors of sellar region A B C A. The images of tumors with high signal intensities on T 1 WI which is the patient with a metastasis of a melanoma. The high signal intensity is due to the melanin content. B. The patient of a glioblastoma multiforme, which caused a hemorrhage in the splenium of the corpus callosum causing high signal intensity. C. On the images of a patient who presented with apoplexy. The high signal is due to hemorrhage in a pituitary macroadenoma.

Tumors of sellar region

Imaging protocol of Pituitary gland • A typical targeted MRI examination of the pituitary region includes coronal and sagittal small field of view T 1 and T 1 post contrast images, as well as dynamic contrast enhanced coronal images, which are critical for the identification of small microadenomas. • T 2 weighted sequences are often also included, although are of relatively littleadded benefit.

Figure: Upward displacement of diaphragma sella

Figure: Downward displacement of diaphragma sella

Figure: Pituitary separate to mass

Diagnosis • Slowly progressive focal neurological signs and signs of intracranial hypertension, epilepsy in a patient with negative history of epilepsy • Optic fundus (oedema) • Imaging – CT – MRI – Skull X-ray • Angiography • EEG, Histological examination of brain tumor tissue samples obtained either by means of brain biopsy or open surgery – definitive diagnosis

Peripheral or ring enhancing cerebral lesions includes: 1. 2. 3. 4. 5. 6. 7. 8. Cerebral abscess Tuberculoma Neurocysticercosis Metastasis Glioblastoma Subacute infarct /haemorrhage /contusion Demyelination (incomplete ring) Tumefactive demyelinating lesion (incomplete ring) 9. Radiation necrosis 10. Postoperative change 11. Lymphoma - in an immunocompromised patient

Peripheral or ring enhancing cerebral lesions includes: • Enhancing wall characteristics – Thick and nodular favours neoplasm – Thin and regular favours abscess – Incomplete ring often opened toward the cortex favours demyelination – Intermediate to low T 2 signal capsule favours abscess – Restricted diffusion of enhancing wall favours GBM or demyelination

Peripheral or ring enhancing cerebral lesions includes: • Surrounding oedema – extensive oedema relative to lesion size favours abscess – increased perfusion favours neoplasm (metastases or primary cerebral malignancy)

Peripheral or ring enhancing cerebral lesions includes: • Central fluid content – Restricted diffusion favours abscess – Absence of diffusion restriction favour a tumour with a central necrotic component (classically a metastases)

Peripheral or ring enhancing cerebral lesions includes: • Number of lesions – Similar sized rounded lesions at grey-white matter junction favours metastases or abscesses – Irregular mass with adjacent secondary lesions embedded in the same region of 'oedema' favours GBM – Small (<1 -2 cm) lesions with thin walls especially if other calcific foci are present suggest neurocysticercosis.

Ring enhancing cerebral lesions Abscess Acute disseminated encephalomyelitis

Single Ring enhancing cerebral lesions • Glioblastoma (GBM) Radiation necrosis

Multiple Ring enhancing cerebral lesions Tuberculomas Multiple Sclerosis

Multiple Ring enhancing cerebral lesions Metastases Tuberculoma

Secondary tumors CT MRI

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