1. Imaging of Skull Base Tumors Henry Ford Health System
Systematic Approach to a Complex Problem
(eDeE-67)
Ciprian Gradinaru MD, Mark Kelly MD
Brent Griffith MD, Suresh Patel MD
Division of Neuroradiology
Henry Ford Health System

2. Disclosures
None of the authors have any disclosures
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3. Introduction
The skull base anatomy can be divided into the anterior, middle and posterior compartments
Tumors can arise from skull base structures or extend into the skull base region from intra or extra cranial lesions
Skull base tumors offer a number of unique challenges:
Deep location
Complex anatomy (neurovascular foramina, adjacent structures)
Close proximity to eloquent structures (brain, orbit, CN’s, vessels)
Diverse pathology (benign/malignant tumors, infectious, congenital)
The osseous skull base and pachymeninges (dura mater) are effective barriers, but tumor can spread through skull base foramina
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4. Introduction Anatomic location Behavior  Benign or Aggressive?
Extension (direct vs. indirect)
Integrity of Eloquent Structures
Evaluation of skull based tumors require a systematic approach to narrow the differential diagnosis.
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5. Role of Imaging Lesion evaluation Prognostic information
Anatomic localization
Extent of disease
Pattern of growth (benign vs. aggressive)
Imaging characteristics
Prognostic information
Disease staging
Morbidity and mortality
Treatment planning
Biopsy/surgical approach
Need for adjuvant therapy
Treatment Follow-up
Treatment response and effects
Recurrence and progression of disease
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6. CT and MR play a complimentary role.
Skull Base Imaging
CT and MR play a complimentary role. CT
Can be performed quickly
Excellent anatomic detail of osseous structures
Information regarding lesion aggressiveness (smooth remodeling vs. erosion of adjacent bone)
Multi-planar reconstructions in any imaging plane from single acquisition
Requires ionizing radiation MR
Longer scan times.
Excellent evaluation of soft tissues
Involvement of neurovascular structures.
Need multiple imaging pulse sequences for characterization of lesions
Prone to artifact (especially at skull base)
No radiation
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7. Skull Base Tumor Classification
Anatomic Location
The skull base is generally grouped into anterior, middle, and the posterior cranial fossae
Location-based classification is helpful because:
Regional specificity of certain tumor types
Similar clinical findings
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8. Skull Base Tumor Classification
Anterior Cranial Fossa
Cancers of the paranasal sinuses or nasal cavity are the most common malignant tumors
Tumor examples:
Meningioma
Esthesioneuroblastoma
Sino-nasal (SN) malignancies
Giant cell tumor (GCT)
Hemangiopericytoma
Multiple myeloma (MM)/plasmacytoma
Sarcomas (Osteo. and Rhabdo.)
Lymphoma
Melanoma
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9. Skull Base Tumor Classification
Middle Cranial Fossa
Central region:
Pituitary adenoma, meningioma, pseudotumor, craniopharyngioma, sphenoid sinus carcinoma
Clival region:
Chordoma, meningioma, paraganglioma, naso- pharyngeal (NP) carcinoma, schwannoma, chondrosarcoma, MM/plasmacytoma, pseudotumor
Para-central/Cavernous Sinus region:
Meningioma, schwannoma, adenoid cystic carcinoma (ACC), NP carcinoma, GCT, pseudotumor
Petro-Clival/Lateral region:
Meningioma, schwannoma, NP angiofibroma, ACC, sarcoma, acquired/congenital cholesteatoma, cholesterol granuloma, pseudotumor
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10. Skull Base Tumor Classification
Posterior Cranial Fossa
Cerebellopontine (CP) angle:
Schwannoma, meningioma, epidermoid, arachnoid cyst, cholesterol granuloma, endo- lymphatic sac tumor, metastasis, leptomeningeal and granulomatous process
Jugular foramen:
Paraganglioma, schwannoma, meningioma, metastasis
Foramen magnum:
Meningioma, schwannoma, chordoma, intra- medullary cord tumor, neurenteric cyst
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11. Systematic Approach Behavior – Benign or Aggressive? Osseous changes
CT  smooth remodeling vs. permeative/destructive pattern
MR  bone marrow involvement (T1 signal abnormality)
Smooth Remodeling
(Pituitary Macro-adenoma)
Permeative/Destructive
(Sarcoma)
T1 Marrow Replacement
(NP Carcinoma)
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12. Systematic Approach Behavior – Benign or Aggressive? Osseous changes
Tumor cellularity (high)
T2WI  hypo to iso-intense signal compared to gray matter
DWI/ADC  restricted diffusion
Iso-intense T2 signal
(Esthesioneuroblastoma)
Restricted Diffusion
(Meningioma)
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13. Behavior – Benign or Aggressive?
Systematic Approach
Behavior – Benign or Aggressive?
Osseous changes
Tumor cellularity
Intra-lesion contents (hemorrhagic or necrotic components)
T1WI pre  hyper-intense signal (hemorrhage)
T1WI post  non-enhancing necrotic tissue
T1 Pre
T1 Post
Hemorrhage
(Chondroblastoma)
Central Necrosis
(Chondrosarcoma)
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14. Behavior – Benign vs. Aggressive?
Systematic Approach
Behavior – Benign vs. Aggressive?
Osseous changes
Tumor cellularity
Intra-lesion contents
Tumor margins
MRI  best on T2wi and post T1wi
Well-defined/smooth  Benign
Ill-defined/infiltrative  Aggressive
Well-defined (Meningioma)
Ill-defined (AdenoCa)
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15. Extracranial  Intracranial Extracranial  Intracranial
Systematic Approach
Extension
Extra-cranial vs. Intra-cranial
Extracranial  Intracranial
Extracranial  Intracranial
SN Neuroendocrine Carcinoma (SNEC)
Meningioma
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16. Systematic Approach Extension Extra-cranial vs. Intra-cranial
Direct vs. Indirect (perineural)
Skull base bone and pachymeninges (dura mater) act as barrier
Neurovascular foramina and cranial nerves provide conduit
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17. Systematic Approach Extension
Perineural involvement includes perineural invasion and spread
Perineural invasion  microscopic feature of malignancy is often confined to the main tumor mass
Perineural spread  clinico-radiologic observation of distant spread of tumor via perineural spaces or within the nerve sheath/nerve itself
Most often seen with extra-cranial squamous cell carcinoma
Most commonly seen with salivary gland tumors (mainly ACC and Muco-epidermoid carcinoma)
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18. Imaging of Peri-neural Involvement
Systematic Approach
Extension
Imaging of Peri-neural Involvement
Focal/segmental/diffuse enhancement and enlargement of the cranial nerve
Skull base foramen enlargement and replacement of the normal fat within the foramen
Look for denervation atrophy of the muscles supplied by the involved cranial nerve
Heterogeneously enhancing mass of the left parotid gland (Mucoepidermoid Carcinoma) with enlargement and enhancement of the left facial nerve as it enters the stylomastoid foramen (normal right facial nerve)
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19. Integrity of Eloquent Structures
Systematic Approach
Integrity of Eloquent Structures
Dural, leptomeningeal and parenchymal invasion
T1WI (post-contrast) and T2WI/FLAIR are best
Leptomeningeal or dural enhancement (nodular or linear > 5 mm)
Enhancement or edema of brain adjacent to tumor
SN Poorly Differentiated Adenocarcinoma
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20. Integrity of Eloquent Structures
Systematic Approach
Integrity of Eloquent Structures
Dural, leptomeningeal and parenchymal invasion
Skull base foramina and contents
Foraminal anatomy is key
MRI  Loss of normal fat and enhancement within neuroforamina
CT  Helpful for evaluation of osseous walls of neuroforamina
Left cavernous sinus meningioma spreading into the left masticator space via the left foramen ovale and into the left pterygopalatine fossa via the left foramen rotundum
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21. Systematic Approach Integrity of Eloquent Structures
Dural, leptomeningeal and parenchymal invasion
Skull base foramina and contents
Orbit and optic nerve
Orbital fissures and apex are most commonly involved
Periorbital and CN-II dural sheath closely related at orbital apex
Lymphoma encasing left optic nerve
Meningioma invading the left orbital apex
Enhancing soft tissue replacing fat within a widened right superior orbital fissure (Meningioma)
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22. Systematic Approach Integrity of Eloquent Structures
Dural/Parenchymal invasion
Skull base foramina and contents
Orbit and optic nerve
Cavernous sinus (CS) involvement
Loss of normal CS enhancement
Convex bulging of the lateral wall of the CS (normally concave)
Nasopharyngeal SCC
Invasive Pituitary Macroadenoma
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23. Case 1: Meningioma HOME Location Behavior Extension
Floor of the anterior cranial fossa
Behavior
Hyperostosis of adjacent skull base (non-aggressive)
Hyperdense mass (indicates high cellularity, but not behavior)
Extension
Intact skull base without evidence of extra-cranial extension
Eloquent Structures
Compression of the bilateral frontal lobes with vasogenic edema
Effacement of the frontal horn of the right lateral ventricle
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24. Case 1: Meningioma HOME Location Behavior Extension
Floor of the anterior cranial fossa
Behavior
Homogeneous enhancement
Restricted diffusion (indicates high cellularity, but not behavior)
Extension
Intact skull base without evidence of extra-cranial extension
Eloquent Structures
Compression of the bilateral frontal lobes
Displacement of vessels
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25. Case 2: Esthesioneuroblastoma
Location
Tumor is centered in the superior olfactory recess region
Behavior
Homogeneous solid enhancement
Destroys the cribriform plate, bilateral ethmoid air cells, nasal septum as well as the bilateral superior and middle nasal conchae
Extension
Tumor extends into the floor of the anterior cranial fossa
Post obstructive changes in the left frontal sinus
Eloquent Structures
Slight mass effect on the bilateral infero-medial frontal lobes
Preserved medial orbital walls
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26. Case 3: Sinonasal Neuroendocrine Carcinoma (SNEC)
Location
Large mass centered in sinonasal cavity
Behavior
Poorly defined tumor margins
Destruction of the cribriform plate, bilateral medial orbital walls, nasal cavity, ethmoid air cells and maxillary sinuses
Extension
Tumor extends into the infero-medial anterior cranial fossa, bilateral medial orbits and bilateral maxillary sinuses
Eloquent Structures
Compression of the bilateral infero-medial frontal lobes with vasogenic edema
Mass effect on the bilateral medial rectus muscles
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27. Case 3: Sinonasal Neuroendocrine Carcinoma (SNEC)
T1 Pre
Location
Large mass centered in sinonasal cavity
Behavior
Heterogeneous enhancement
Irregular tumor margin
Extension
Superior extension into the anterior cranial fossa
Extends into bilateral medial orbits and maxillary sinuses
Eloquent Structures
Compression of bilateral frontal lobes with vasogenic edema
Mass effect on medial rectus muscles
Mass effect on optic chiasm
T1 Post
T2 FS
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28. Case 4: Invasive Pituitary Macroadenoma
Location
Large mass (> 10mm) centered in the central/para-central middle cranial fossa
Behavior
Homogeneous avid enhancement
Smooth well defined margins
Extension
Left cavernous sinus with convex lateral bulge
Supra-sellar region
Eloquent Structures
Encasement of the left internal carotid artery
Mass effect on the optic chiasm
Mass effect on anteromedial left temporal lobe
Slight flattening of the left anterior pons
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29. Case 5: Chordoma HOME Location Behavior Extension Eloquent Structures
Midline mass originating from the clivus
Behavior
Infiltrative mass with irregular margins
Bony destruction
Extension
Anteriorly into sphenoid sinuses, ethmoid air cells, and nasal cavity
Posteriorly into pre-pontine cistern
Superorly into sellar/supra-sellar region
Inferiorly into nasopharynx
Left lateral into medial middle cranial fossa and left maxillary sinus
Eloquent Structures
Mass effect on antero-medial left temporal lobe
Slight flattening of anterior pons
Mass effect on pituitary gland
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30. Case 5: Chordoma HOME Location Behavior Extension Eloquent Structures
Midline mass originating from the clivus
Behavior
Infiltrative mass with irregular margins (aggressive)
Extension
Anteriorly into sphenoid sinuses, ethmoid air cells, and nasal cavity
Posteriorly into pre-pontine cistern
Superorly into sellar/suprasellar region
Inferiorly into nasopharynx
Left lateral into middle cranial fossa
Eloquent Structures
Mass effect on medial left temporal lobe
Slight flattening of the anterior pons
Mass effect on the pituitary gland
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31. Case 6: Cavernous Sinus Meningioma
Location
Mass located in the right para-central middle cranial fossa
Behavior
Homogeneously enhancing mass
Smooth widening of the right superior and inferior orbital fissures (non-aggressive)
Hyperostosis of the greater wing of the right sphenoid bone (non-aggressive)
Extension
Right orbital apex
Right superior and inferior orbital fissures
Right pterygopalatine fossa
Eloquent Structures
Neurovascular structures involving right cavernous sinus, superior orbital fissure and pterygopalatine fossa
Compression of optic nerve at orbital apex
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32. Case 6: Cavernous Sinus Meningioma
Location
Mass located in the right para-central middle cranial fossa
Behavior
Homogeneously enhancing mass with smooth margins (non-aggressive)
Widening of right pterygomaxillary fissure
Extension
Right pterygopalatine fossa (replacement of fat on precontrast T1)
Eloquent Structures
Encasement and narrowing of the right internal carotid artery
Slight compression of the medial right temporal lobe
Other neurovascular structures within the cavernous sinus and pterygopalatine fossa
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33. Case 7: Nasopharyngeal SCC
Location
Soft tissue density involving the left pterygopalatine fossa
Behavior
Intense FDG uptake on PET
Widening of the left sphenopalatine foramen and left pterygomaxillary fissure
Bony erosion (aggressive) of posterior left maxillary sinus wall and left pterygoid plate
Extension
Left inferior orbital fissure
Left pterygopalatine fossa (replacement of fat on CT)
Eloquent Structures
Neurovascular structures within the left pterygopalatine fossa and inferior orbital fissure
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34. Case 8: Chondrosarcoma HOME Location Behavior Extension
Lesion centered at the left petro-occipital fissure
Behavior
Permeative osseous destruction of the clivus and left petrous apex (aggressive)
Extension
Erosion of the wall of the left carotid canal
Anterior aspect of the left jugular foramen
Eloquent Structures
Potential involvement of left internal carotid artery
Neurovascular structures within the left jugular foramen
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35. Case 8: Chondrosarcoma HOME Location Behavior Extension
Mass centered at the left petro-occipital fissure
Behavior
Heterogeneous enhancement with areas of central necrosis
Extension
Involvement of the clivus and left petrous apex
Extension into the left pre-pontine and cerebello-pontine cisterns
Eloquent Structures
Compression of the pons
Close proximity to the basilar artery
Focal encasement of the left internal carotid artery
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36. Case 9: Glomus Jugulotympanicum
Location
Mass centered within the region of the left jugular foramen
Behavior
Moth-eaten bony destruction (aggressive) of the left jugular foramen walls and posteromedial aspect of the left middle ear cavity
Extension
Posteromedial aspect of the left middle ear cavity
Eloquent Structures
Neurovascular structures coursing within the left jugular foramen (pars nervosa and pars vascularis)
Left middle ear structures
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37. Case 9: Glomus Jugulotympanicum
Location
Mass centered within the region of the left jugular foramen
Behavior
Heterogeneous enhancement
Extension
Left jugular foramen (pars nervosa and pars vascularis)
Left sigmoid sinus
Eloquent Structures
Neurovascular structures within the left jugular foramen (pars nervosa and pars vascularis)
Left middle ear structures
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38. Case 10: Endolymphatic Sac Tumor
Location
Mass in the posterolateral aspect of the left petrous temporal bone
Behavior
Partially cystic mass with enhancement of the non-cystic component
No restriction diffusion
Erosive changes of the posterior left petrous temporal bone (aggressive)
Extension
Left cerebello-pontine cistern
Left vestibular aqueduct is not identified
Eloquent Structures
Slight mass effect on the left cerebellum
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39. Take-Home Points
Large variety of pathology  histological diagnosis by imaging is not possible.
Imaging plays important role in evaluation:
Anatomic localization and extent of disease
Biologic behavior (benign vs. aggressive)
Involvement of adjacent eloquent structures
Treatment planning (3-D surgical navigation)
Post-treatment morbidity and mortality
Follow-up post-treatment
Complex anatomy and diverse pathology
Systematic approach for evaluating skull base tumors is important
Location and behavior can help shorten the differential diagnosis
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40. References .
Erdem E et al: Comprehensive review of intracranial chordoma. Radiographics. 23(4): , 2003
Nakasu Y et al: Tentorial enhancement on MR images is a sign of cavernous sinus involvement in patients with sellar tumors. AJNR Am J Neuroradiol. 22(8): , 2001
van den Berg R: Imaging and management of head and neck paragangliomas. Eur Radiol. 15(7):1310-8, 2005
Razek AA et al: Imaging lesions of the cavernous sinus. AJNR Am J Neuroradiol Mar;30(3): Epub 2008 Dec 18. Review. Erratum in: AJNR Am J Neuroradiol. 30(7):E115, 2009D
Schmidinger A et al: Natural history of chondroid skull base lesions--case report and review. Neuroradiology. 44(3):268-71, 2002D
Lo WW et al: Endolymphatic sac tumors: radiologic appearance. Radiology. 189(1): , 1993
Chong VF et al: Nasopharyngeal carcinoma. Eur J Radiol. 66(3):437-47, 2008D
Yu T et al: Esthesioneuroblastoma methods of intracranial extension: CT and MR imaging findings. Neuroradiology. 51(12):841-50, 2009D
Harnsberger R, Hudgins R, Wiggins P, et al. Diagnostic Imaging: Head and Neck. Salt Lake City, Utah: Amirsys, Inc
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