Imaging of Petrous Apex: Anatomy and Pathology

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1 University of Utah Head and Neck Conference 2018 Petrous apex Imaging of Petrous Apex: Anatomy and Pathology Philip Chapman MD University of Alabama, Birmingham Good News PAs tend to be symmetric A quick glance at axial MRI or CT is usually all that is required to evaluate Isolated PA lesions are relatively rare Many abnormalities are incidental or don t touch me lesions Bad News Obvious asymmetry creates an automatic dilemma Once you see a possible lesion you have to answer bunch of questions in order to narrow down differential It seems that additional study is always necessary Its our responsibility to determine the significance of a lesion and narrow the differential Petrous Portion of Temporal Bone Petrous Apex Overview Petrous Portion of Temporal Bone includes middle ear and inner ear Petrous Apex is medial to the inner ear Anatomic Relationships of Petrous Apex 3-Sided Pyramid The petrous apex is a pyramidal shaped, variably pneumatized structure of the temporal bone that has unique anatomic relationships to: central skull base intracranial compartments suprahyoid neck Posterior face IAC Anterior face 1

2 3-Sided Pyramid Petrous Apex: Anatomic Relationships Exocranial face IAC PA is intimately related to several important anatomic structures Cavernous sinus & CNS POF Clivus Meckel s cave and trigeminal nerve Carotid Artery Jugular foramen Sphenoid Sinus Nasopharynx Tentorium cerebelli Petroclinoid Folds and Roof of Cavernous sinus Interclinoid fold Fixed edge with superior petrosal sinus Free edge Anterior Petroclinoid fold Posterior Petroclinoid fold Oculomotor Triangle Arcuate Eminence & SCC Superior Petrosal Sinus 2

3 Trigeminal Impression Lacerum segment CN VI Trabecular bone Dorello s Canal Petroclival Junction Greater Superficial Petrosal Nerve Greater Superficial Petrosal Geniculate Ganglion Lacerum segment Notice how thin the bone is here Greater Superficial Petrosal Nerve PA Facial nerve Greater Superficial Petrosal Nerve 1. Parasympathetics /lacrimation 2. Potential site of PNTS 3. Surgical Landmark for geniculate ganglion Facial Nerve Schwannoma PNTS involving GSPN Greater Superficial Petrosal Nerve 3

4 PPF Foramen rotundum Petroclival Junction Foramen Ovale Vidian Canal Vidian Canal Foramen Ovale POF Foramen Lacerum 4

5 Nasopharyngeal Relationships of Petrous Apex Petrous Apex Petrous Apex Most commonly, PA is composed of rim of cortical bone and intrinsic trabecular bone containing bone marrow Pneumatization of the petrous apex occurs in 9 30% of patients Normal imaging appearance on CT or MR is highly dependent on presence of marrow space vs. pneumatized air cells within PA 5

6 Asymmetric Pneumatization Petrous Apex Effusion Petrous Apex Effusion Petrous Apex Effusion Expansile or not? Asymmetric PA Is there a lesion or process that replaces normal bone marrow? Is there a lesion/process that replaces normal air density/hypointensity related to pneumatized air cells? Is the lesion enhancing? Is there associated bone expansion, erosion, or destruction? 6

7 Pathology Pathology Intrinsic Lesions Pathology of Petrous Apex Bone/ Bone Marrow/Cartilage Petrous apex air cells Internal Carotid Artery Chondrosarcoma of POF Metastatic disease Myeloma Lymphoma/Leukemia Sarcoma Osteomyelitis Effusion Petrous apicitis Cholesterol granuloma Cholesteatoma Aneurysm Thrombosis Extrinsic Lesions/Extracranial Pathology of Petrous Apex Nasopharyngeal carcinoma Sinonasal carcinoma Sarcoma Lymphoma Invasive infection Glomus Endolymphatic Sac Tumor Pathology Petrous Apex: Pathology Pathology of Petrous Apex Extrinsic Lesions/Intracranial Invasive Meningioma PA Cephalocele Dural Mets 44 year old patient with left 6 th nerve palsy In Search of Dorello s Canal In Search of Dorello s Canal 7

8 Petrous Apex: Pathology Petrous Apex: Pathology T2 Hyperintensity Petrous Apex: Pathology Petrous Apex: Pathology Post Contrast Robust Enhancement Petrous Apex: Pathology Petrous Apex: Pathology The least likely diagnosis for this destructive, enhancing lesion of the petrous apex is: 1. Metastatic disease 2. Myeloma 3. Chondrosarcoma 4. Chordoma 5. PA cephalocele The least likely diagnosis for this destructive, enhancing lesion of the petrous apex is: 1. Metastatic disease 2. Myeloma 3. Chondrosarcoma 4. Chordoma 5. PA cephalocele 8

9 Classic POF Chondrosarcoma Chondrosarcoma: Companion Case POF (or PA) Chondrosarcoma Enhancement is diffuse Usually markedly hyperintense on T2 Fingerlike or polypoid extensions (cauliflower) CT appearance: Typically lytic expansile lesion with peripheral irregular calcification 50%?? contain chondroid calcifications Chondrosarcoma: Companion Case Chondrosarcoma: Companion Case Chondrosarcoma: Companion Case #2 Classic Chondrosarcoma: Boards/CAQs 9

10 Chordomas vs Chondrosarcomas Chordomas vs Chondrosarcomas Chordoma vs. Chondrosarcoma Both are rare skull base tumors Both are typically hyperintense on T2 Both are typically slow growing At light microscopy, chordomas were thought to have chondroid features (ex: chondroid chordoma) Chordoma vs. Chondrosarcoma These tumors are immunohistochemically distinct. Chordoma actually has no chondroid elements. Chordomas tend to occur in midline: Clivus Chondrosarcomas tend to occur off midline : Petro-occipital Fissure Classic Chordoma Off-Midline Chordoma Chordomas vs Chondrosarcomas Chordomas vs Chondrosarcomas Intermediate Grade Chondrosarcoma 10

11 Chordomas vs Chondrosarcomas Petrous Apex: Neoplasms Can we tell the difference? None of the MRI or CT features appear to be useful for differentiating chordomas from chondrosarcomas Metastatic Breast Cancer Petrous Apex: Neoplasms Petrous Apex: Neoplasms Companion Case: Metastatic Breast Cancer Petrous Apex: Neoplasms Petrous Apex: Neoplasms 11

12 Petrous Apex: Neoplasms Petrous Apex: Neoplasms Multifocal Disease Petrous Apex: Neoplasms Multifocal Lymphoma Petrous Apex: Neoplasms Companion Case: Metastatic Lung Cancer 57 year old female followed for bilateral cavernous carotid aneurysms also with history of lung cancer presents with headache Petrous Apex: Neoplasms Right petrous apex plasmacytoma Petrous Apex: Benign Intrinsic Lesions Fibrous Dysplasia 12

13 Petrous Apex: Benign Intrinsic Lesions Paget s Petrous Apex: Benign Intrinsic Lesions Osteopetrosis Petrous Apex: Endocranial Lesions Petrous Apex: Endocranial Lesions Petrous Apex Meningioma Petrous Apex: Endocranial Lesions Petrous Apex: Endocranial Lesions Large Petroclival Meningioma Invasive Meningioma Transforaminal extension through Foramen Rotundum Sphenoid Sinus Invasion Petrous Apex Marrow Involvement Enhancing Stuff Most meningiomas invasive to skull base are WHO grade I or II, and not malignant 13

14 Petrous Apex: Endocranial Lesions Petrous Apex: Endocranial Lesions Companion case: Invasive Meningioma 11 year old female with headache and facial pain Petrous Apex: Endocranial Lesions Trigeminal Schwannoma Petrous Apex: Endocranial Lesions Trigeminal Schwannoma Petrous Apex Cephalocele Petrous Apex Cephalocele 70 year old with vertigo 14

15 Petrous Apex Cephalocele Petrous Apex Cephalocele Pseudomeningoceles, meningoceles Rarely associated with symptoms Tracks like CSF on all sequences!! Subset may be related to Intracranial hypertension Petrous Apex Cephaloceles AJNR Nov 2001; 22: Petrous Apex Cephalocele Petrous Apex Cephalocele Petrous Apex Cephalocele Petrous Apex Cephalocele FLAIR POST 15

16 Petrous Apex: Intrinsic Expansile Petrous Apex: Intrinsic Expansile 43 yo with right 6 th nerve palsy and HA Petrous Apex: Intrinsic Expansile Petrous Apex: Intrinsic Expansile Cholesterol Granuloma Hyperintense on T1- smoky appearance T2-Can be markedly hyperintense or heterogeneous NOT fat signal No internal enhancement T1 T2 POST Well circumscribed bony margins May be lobulated or cauliflower-like Petrous Apex: Intrinsic Expansile Petrous Apex: Intrinsic Expansile MRI: Hyperintense on T1- smoky appearance T2- Can be hyperintense or markedly heterogeneous and rim of hypointensity NOT fat signal No internal enhancement May be lobulated or cauliflower-like CT: Expansile, lytic lesion Well circumscribed bony margins Cholesterol Granuloma Cholesterol Granuloma Cholesterol crystals can be formed in any location where there has been cellular degeneration prior hemorrhage degenerating inflammatory cells necrotic inflammatory tissue Cholesterol crystals act as foreign bodies, and they incite a strong granulomatous reaction from the tissue in which they form. Clefts Polarized Crystals 16

17 Petrous Apex: Cholesterol Granuloma Petrous Apex: Cholesterol Granuloma Companion Case: Cholesterol Granuloma Obstruction Expansion Inflammatory Response Hemorrhage Granulation Tissue Petrous Apex: Cholesterol Granuloma Companion Case: Cholesterol Granuloma Petrous Apex: Cholesterol Granuloma Companion Case: Cholesterol Granuloma Petrous Apex: Cholesterol Granuloma Companion Case: Cholesterol Granuloma Exocranial Lesions Nasopharyngeal Carcinoma 60 Year old patient with history of Nasopharyngeal Carcinoma Now with right facial pain and neck nodes Post Operative Appearance: Fat Packing 17

18 Exocranial Lesions Nasopharyngeal Carcinoma Petrous Apex: Carotid lesion Petrous Apex Mass Petrous Apex: Carotid lesion Infection Petrous ICA Apex Aneurysm Mass Teaching Point: Vascular Lesions in the skull base may have: slow flow complex flow mixed signal thrombus partial thrombosis Confusing MRI appearance 55 year old with Type 2 Diabetes, congenital deafness and inability to communicate verbally presents with low grade fever, severe pain and drainage from left ear. Coronal MIP CTA Aneurysm Always consider CTA to fully evaluate the ICAs and the cavernous sinuses for a lesion in central skull base seen on MRI. Had been treated for several weeks for otomastoiditis, but symptoms progressed Infection Infection Erosion of bone at the central skull base Infiltrating process of the central skull base region and nasopharyngeal soft tissues 18

19 Infection Otomastoiditis and Central Skull Base Osteomyelitis Infection Otomastoiditis and Central Skull Base Osteomyelitis Staph aureus Infection Infection Typical Skull Base Osteomyelitis Elderly diabetic or immunocompromised pts Typically complication of Malignant Otitis Externa Process originates as a soft-tissue infection of the EAC, then spreads to the skull base through the fissures of Santorini along the floor of cartilaginous EAC Pseudomonas, Aspergillosis It causes bone destruction of the skull base Affects the skull base foramina and cavernous sinuses, causing cranial neuropathies Skull Base Osteomyelitis Secondary to Fungal MOE Courtesy of Christine Glastonbury 75yM asian, with DM Had ear discharge, admitted to OSH where multiple biopsies obtained searching for NPC All negative Increasing ear pain and fevers then Dx of skull base osteomyelitis Not responding to pseud-covering AB Clinical and MRI findings progressed until final biopsy demonstrated Aspergillosis Infection Infection Skull Base Osteomyelitis Secondary to Fungal MOE Skull Base Osteomyelitis Secondary to Fungal MOE 19

20 Infection Skull Base Osteomyelitis Infection Skull Base Osteomyelitis Petrous apex marrow space Occipital Bone marrow space Streptococcus pneumonia PA Lesions Endolymphatic Sac Tumor PA Lesions Giant Jugulotympanicum Paraganglioma 73 yo female with multiple right sided lower cranial neuropathies, including right vocal cord paralysis and hearing loss 20