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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 HOME • 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 HOME 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 HOME • 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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) HOME 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) HOME 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) HOME 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) HOME Extension Intracranial Extracranial Intracranial Extra-cranial vs. Intra-cranial Extracranial • Meningioma SN Neuroendocrine Carcinoma (SNEC) HOME 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 HOME 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) HOME 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) HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME • 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME 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 HOME • 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 HOME . 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. HOME
