Ciprian Gradinaru MD, Mark Kelly MD
Brent Griffith MD, Suresh Patel MD
Division of Neuroradiology
Henry Ford Health System
Disclosures
None of the authors have any disclosures
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• 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)
barriers, but tumor can spread through skull base foramina
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are effective
Evaluation of skull
based tumors
require a systematic
approach to narrow
the differential
diagnosis.
•
•
•
•
Anatomic location
Behavior  Benign or Aggressive?
Extension (direct vs. indirect)
Integrity of Eloquent Structures
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• Lesion evaluation
• 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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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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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
http://www.mayfieldclinic.com
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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
http://www.mayfieldclinic.com
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Middle Cranial Fossa
• Central region:
• Pituitary adenoma, meningioma, pseudotumor,
craniopharyngioma, sphenoid sinus carcinoma
• Clival region:
• Chordoma, meningioma, paraganglioma, nasopharyngeal (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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http://www.mayfieldclinic.com
Posterior Cranial Fossa
•Cerebellopontine (CP) angle:
• Schwannoma, meningioma, epidermoid,
arachnoid cyst, cholesterol granuloma, endolymphatic sac tumor, metastasis, leptomeningeal
and granulomatous process
•Jugular foramen:
• Paraganglioma, schwannoma, meningioma,
metastasis
•Foramen magnum:
• Meningioma, schwannoma, chordoma, intramedullary cord tumor, neurenteric cyst
http://www.mayfieldclinic.com
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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)
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T1 Marrow Replacement
(NP Carcinoma)
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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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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Behavior – Benign vs. Aggressive?
•Osseous changes
•Tumor cellularity
•Intra-lesion contents
•Tumor margins
Well-defined (Meningioma)
• MRI  best on T2wi and post T1wi
• Well-defined/smooth  Benign
• Ill-defined/infiltrative  Aggressive
Ill-defined (AdenoCa)
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Extension
 Intracranial
Extracranial  Intracranial
Extra-cranial vs. Intra-cranial
Extracranial
•
Meningioma
SN Neuroendocrine Carcinoma (SNEC)
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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
http://www.imaios.com/Media/Images/e-anatomy/Cranial-nervesanatomy-diagrams/skull-cranial-base-foramen-cranial-nerves-anatomy-en
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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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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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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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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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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
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Enhancing soft tissue replacing fat within a
widened right superior orbital fissure
(Meningioma)
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)
Invasive Pituitary
Macroadenoma
Nasopharyngeal
SCC
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Location
• 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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Location
• 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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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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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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T1 Pre
Location
• Large mass centered in sinonasal cavity
Behavior
• Heterogeneous enhancement
T1 Post
• Irregular tumor margin
Extension
• Superior extension into the anterior
cranial fossa
T2 FS
• Extends into bilateral medial orbits and
maxillary sinuses
Eloquent Structures
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•
Compression of bilateral frontal lobes
with vasogenic edema
•
Mass effect on medial rectus muscles
•
Mass effect on optic chiasm
Location
• Large mass (> 10mm) centered in
central/para-central middle cranial fossa
the
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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Location
• 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
temporal lobe
on
antero-medial
• Slight flattening of anterior pons
• Mass effect on pituitary gland
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left
Location
• 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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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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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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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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Location
• 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
foramen
of
the
left
jugular
Eloquent Structures
• Potential involvement of left internal
carotid artery
• Neurovascular structures within the left
jugular foramen
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Location
• Mass centered at the left petro-occipital
fissure
Behavior
• Heterogeneous enhancement
areas of central necrosis
with
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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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
middle ear cavity
of
the
left
Eloquent Structures
• Neurovascular structures coursing
within the left jugular foramen (pars
nervosa and pars vascularis)
• Left middle ear structures
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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 sigmoid sinus
• Left middle ear structures
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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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• 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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1. Erdem E et al: Comprehensive review of intracranial chordoma. Radiographics. 23(4):995-1009,
2003
2. 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):1528-33, 2001
3. van den Berg R: Imaging and management of head and neck paragangliomas. Eur Radiol.
15(7):1310-8, 2005
4. Razek AA et al: Imaging lesions of the cavernous sinus. AJNR Am J Neuroradiol. 2009
Mar;30(3):444-52. Epub 2008 Dec 18. Review. Erratum in: AJNR Am J Neuroradiol. 30(7):E115,
2009D
5. Schmidinger A et al: Natural history of chondroid skull base lesions--case report and review.
Neuroradiology. 44(3):268-71, 2002D
6. Lo WW et al: Endolymphatic sac tumors: radiologic appearance. Radiology. 189(1):199-204, 1993
7. Chong VF et al: Nasopharyngeal carcinoma. Eur J Radiol. 66(3):437-47, 2008D
8. Yu T et al: Esthesioneuroblastoma methods of intracranial extension: CT and MR imaging
findings. Neuroradiology. 51(12):841-50, 2009D
9. Harnsberger R, Hudgins R, Wiggins P, et al. Diagnostic Imaging: Head and Neck. Salt Lake City,
Utah: Amirsys, Inc. 2004.
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