Schematic of Locations

PATTERN ANALYSIS

Basic Approach

• Where is the lesion ?
• Supratentorial
• Infratentorial
• Where is the lesion ?
• Intraaxial
• Extraaxial
• How old is the patient ?
• Child
• Adult

PATTERN ANALYSIS

Where is the Lesion?

• INTRAAXIAL
• internal to PIA
• (brain parenchyma)
• EXTRAAXIAL
• external to PIA
• (meninges, nerve sheath)
• INTRAVENTRICULAR
• Lateral
• Third
• Fourth

INTRAAXIAL:

Differential

• CORTEX
• GRAY/WHITE JUNCTION
• DEEP WHITE MATTER
• DEEP GRAY MATTER

INTRAAXIAL:

Differential

• Glioma
• Medulloblastoma
• Hemangioblastoma
• Metastases
• Infarct/hematoma
• AVM/congenital
• Abscess/inflammation

EXTRAAXIAL LESIONS

(Location)

• Subarachnoid
• Subdural
• Epidural
• Calvarium (skull base)
• Subgaleal
• Scalp (soft tissues)

EXTRAAXIAL LESIONS

(Differential):

• Meningioma
• Pituitary adenoma
• Craniopharyngioma
• Schwannoma
• Chordoma
• Dermoid/epidermoid, cyst, lipoma
• Hematoma, metastasis, infection

CLASSIC LOCATIONS

• Foramen magnum
• Cerebellopontine angle
• Fourth ventricle/Cerebellum
• Sella/parasellar/suprasellar
• Basal ganglia/Third ventricle
• Lateral ventricle/Pineal region
• Deep hemispheric/periventricular
• Cortical/subcortical
• Convexity

CPA MASSES:

Differential

• S schwannoma (8th >> > 5th)
• A aneurysm, arachnoid cyst
• M meningioma, mets
• E epidermoid, ependymoma, CPP

CPA MASSES

Demographics

• 7/9 (Schwannoma, 8th > > 5th)
• 1/9 Meningioma (tentorial/petrous)
• 1/9 "Other":
• Epidermoid (1/18)
• Mets, aneurysm, etc.
• Glioma (ependymoma, CPP)
• Arachnoid cyst, Cystadenoma

FEATURES OF CPA MASSES

Differential Diagnosis of CPA Masses

Vestibular Schwannoma	Meningioma	Epidermoid Cyst
Related to IAC	Related to Dura/Tentorium	Cisternal Mass
IAC Enlarged	No relationship	No relationship
Heterogeneous if Large	Homogeneous	Does NOT enhance
Round, Acute Angle	Hemisphere, Obtuse Angle	Undulating/Serpentine

*

Differential

• Medulloblastoma (PNET)
• Astrocytoma (usu. Pilocytic)
• Ependymoma
• Post fossa cysts

DEEP CEREBELLAR (ADULT)

• Metastasis
• Hemangioblastoma
• Hemorrhage, infarct
• Glioma (Ependymoma, Astro)
• Abscess

POSTERIOR FOSSA

INCIDENCE/LOCATION:

• Medulloblastoma (1/4 - 1/3)
• Post. To IVth
• Brainstem glioma (1/6)
• Ant. To IVth
• Ependymoma (1/6)
• Inside IVth
• Pilocytic (1/4 - 1/3)
• Lat. And/or post. IVth
• ( and these are often a cyst w / nodule )

DRAWING

SELLA/PARASELLAR REGION

Differential:

• Pituitary adenoma
• Craniopharyngioma
• Aneurysm (ICA , etc.)
• Meningioma
• Optic/hypothalamic glioma
• Chordoma
• Granuloma, e.g., hamartoma, cyst(arachnoid, dermoid/epi)
• Germ Cell (Germinoma)

PITUITARY ADENOMA

Sexual Dimorphism

paste table

Differential Features:

• CHILD - Craniopharyngioma / Glioma (hypothalamus or optic )
• ADULT - Pituitary adenoma
• SELLA NORMAL - NOT pituitary
• Ca++ - Craniopharyngioma, but...
• HYPEROSTOSIS - Meningioma ( exp. "blistering" )
• CLIVUS - Chordoma, mets, NP Ca
• Remember - rule out vascular lesions (aneurysms)

HYDROCEPHALUS

Differential Diagnosis:

• Over production of CSF (CPP)
• Obstruction of CSF flow:
• Obstructive/internal hydrocephalus
• Communicating/external hydrocephalus
• Under reabsorption of CSF: SAH
• Compensatory:
• Ex vacuo/enlargement

THIRD VENTRICLE

Differential:

• Colloid cyst
• Craniopharyngioma
• Hypothalamic and thalamic glioma
• CPP, ependymoma
• Basilar tip aneurysm
• Neurocytoma

BASAL GANGLIA/THALAMUS:

• BILATERAL SYMMETRIC (toxic/metabolic):
• PUTAMEN - Methanol
• GLOBUS PALLIDUS - CO Poisoning
• BILATERAL ASYMMETRIC (hematogenous):
• INFECTION (TOXO, etc.)
• UNILATERAL (acquired/neoplastic):
• THALAMUS GLIOMA (astrocytoma)
• HYPERTENSIVE HEMATOMA (exclusion)

ABOVE FORAMEN OF MONRO

Lateral Ventricle/caudate

• Subependymal Giant Cell Astro.
• TUBEROUS SCLEROSIS, Enhances & Ca++
• Subependymoma (variant of Ependymoma)
• No Ca++, no enhancement
• Central Neurocytoma
• (septum pellucidum)
• Cyst/Cavum septum pellucidum
• Huntington's Chorea
• ATROPHY

INTRAVENTRICULAR NEOPLASMS:

• Ependymoma (and subependymoma)
• Choroid plexus papilloma
• Subependymal giant cell astro.
• Meningioma
• Colloid cyst (3rd)
• Dermoid/epidermoid
• Central neurocytoma
• Medulloblastoma (4th)
• Mets, lymphoma, Germ Cell

PINEAL/QUAD. CISTERN REGION:

• "Pinealomas"
• Germ cell tumors
• Pineal cell tumors
• Pineoblastoma
• Pineocytoma
• Gliomas (regional)
• Brainstem, callosum, thalamus
• Other
• Dermoid, lipoma, arachnoid cyst
• Meningioma
• Vein of Galen malformations

DEEP AND PERIVENTRICULAR:

• Glioma (astrocytoma)
• Lymphoma
• Toxoplasmosis, CMV
• Leukoencephalopathy (WM)
• Arteriolar sclerosis (HT)
• Infarcts (lacunar)
• Hemorrhage

CONVEXITY (INTRAAXIAL)

• Gray-White Junction
• HEMATOGENOUS Neoplasm
• HEMATOGENOUS Infection
• HEMATOGENOUS Thrombi (multiple infarcts)
• INFARCTION/ISCHEMIA
• VASCULITIS

CEREBRAL INFARCTION

1. Abrupt Onset
2. Gray Matter Involved
3. Little Mass Effect
4. Vascular Wedge

CONVEXITY (EXTRAAXIAL)

Differential

• EPIDURAL (HEMATOMA empyema, mets)
• (biconvex, acute, limited by sutures)
• SUBDURAL (HEMATOMA empyema, mets)
• (Crescentic, subacute, crosses sutures)
• MENINGIOMA
• (hyperdense, hemispheric, hyperostosis, homogeneous enhancement)

END OF SECTION

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James G. Smirniotopoulos, M.D.
Professor of Radiology, Neurology, and Biomedical Informatics
Chairman, Department of Radiology and Radiological Sciences
Uniformed Services University of the Health Sciences
4301 Jones Bridge Road
Bethesda, MD 20814
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