Skull base imaging
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This document provides an overview of skull base anatomy and imaging of skull base pathology. It begins with a description of the bones that make up the skull base and key anatomical structures like foramina and sinuses. Common pathologies are then discussed, including tumors originating from within the skull base (intra-axial) or adjacent structures outside the skull base (extra-axial). Example cases of chordoma and glomus tumor are presented with imaging findings. Finally, some hints and tips for skull base MRI interpretation are provided.
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Skull base imaging
- 2. Great teachers – All this is their work . I am just the reader of their books .Prof. Paolo castelnuovo Prof. Aldo Stamm Prof. Mario Sanna Prof. Magnan
- 3. For Other powerpoint presentatioins of “ Skull base 360° ” I will update continuosly with date tag at the end as I am getting more & more information click www.skullbase360.in - you have to login to slideshare.net with Facebook account after clicking www.skullbase360.in
- 4. Dr.Prahlad sir https://www.facebook.com/prahlada?fref=ts skull base imaging lecture Click link for skull base imaging video = https://www.youtube.com/watch? v=HYYB-8pv7k4&feature=youtu.be
- 5. Popular videos of skull base imaging in youtube https://www.youtube.com/playlist? list=PLxfT3LHUjLuJD3JsWQU4vL h4X5f_5OD0g
- 6. • In book of Mario sanna – “Microsurgery of paragangliomas” given – “ Radiological Anatomy ” in 3rd chapter – click https://books.google.co.in/books? id=7k_jwKyT6d0C&lpg=PP1&dq=mario %20sanna %20paraganglioma&pg=PP101#v=snip pet&q=Radiological %20Anatomy&f=false
- 8. Content • Normal skull base anatomy • Pathology intrinsic to skull base – some case examples • Pathology affecting skull base from below – some case examples • A few hints and tips!
- 9. Anatomy Five Bones: • Ethmoid - CP • Sphenoid- GW+LW • Occipital • Temporal- paired • Frontal-paired
- 10. Cranial Fossae • Anterior • Middle • Posterior
- 11. Anterior Cranial Fossa • Anterior • Frontal bone: frontal sinus,supra-orbital foramen • Posterior • Post. edge of lesser wing sphenoid and its ant. Clinoid processes – Intracranial landmarks: foramen ceacum, crista galli, cribiform plate, planum sphenoidal – Extracranial landmarks: nasal cavity, ethmoid and sphenoid sinuses, orbits
- 12. Middle Cranial Fossa • Anterior • Posterior edge of lesser wing of sphenoid • Posterior • Post-sup edge of petrous temporal bone
- 13. Posterior Cranial Fossa • Anteriorly – Post-sup edge of petrous temporal bone • Posteriorly – it is enclosed by the occipital bone. • Laterally – portions of the squamous temporal and mastoid part of the temporal bone form its walls. • It contains the brainstem and cerebellum.
- 14. Skull Base Anatomy Temporal Bone Temporal bone- petrous portion Sphenoid Bone Occipital Bone Key Fissures • Petro-sphenoidal fissure • Petro-occipital fissure Key Sutures • Sphenosquamous Suture • Occipitomastoid Suture
- 18. IAC INTERNAL AUDITORY CANAL CAROTID CANAL OSSICLES MALLEUS INCUS
- 20. Skull Base Anatomy Foramen spinosum Sphenoid spine- lower level Foramen rotundum- higher level Pterygopalatine fossa Foramen ovale Petro-occipital fissure Pterygoid canal f. lacerum
- 21. Skull Base Anatomy Foramen Spinosum • Middle meningeal artery/vein • CV V3, recurrent branch • Lesser superficial petrosal nerve Foramen Ovale • CN V3 • Lesser petrosal nerve • Accessory meningeal artery • Emissary veins
- 22. Skull Base Anatomy Foramen Lacerum • Ascending pharyngeal artery- meningeal branch • Nerve of pterygoid canal Vidian Canal • aka pterygoid canal • Pterygopalatine fossa - foramen lacerum • Vidian nerve • Vidian artery
- 23. Skull Base Anatomy Foramen rotundum • CN V2 • Artery of foramen rotundum • Emissary veins
- 24. * Skull Base Anatomy Foramen magnum • Medulla oblongata • Vertebral arteries • Anterior/Posterior spinal arteries Hypoglossal canal • CN XII • Hypoglossal artery *
- 25. Skull Base Anatomy Jugular Foramen • Pars nervosa: CN IX, inferior petrosal sinus • Pars vascularis: CN X, XI, jugular bulb * * Carotid canal
- 26. Skull Base Anatomy Pterygopalatine Fossa • Pterygopalatine ganglia V2 • Pterygopalatine plexus • Communicates with: Inferior orbital fissure Orbital apex Sphenopalatine foramen Pterygomaxilary fissure Foramen rotundum Vidian canal Greater/lesser palatine canals and foramina
- 27. Receives: Superior opthalmic vein Inferior opthalmic vein Sphenoparietal sinus Drains via: Petrosal sinuses Basilar plexus Pterygoid plexus Connection: Circular sinus Contains: CN III, IV, V1, V2, VI Skull Base Anatomy Cavernous Sinus Meckel’s Cave • Posterior aspect of cavernous sinus • Gasserian ganglion (sensory root ganglion of CN V)
- 28. Skull Base Anatomy Superior Orbital Fissure • CN III, IV, V1, VI • Middle meningeal artery- orbital branch • Recurrent meningeal artery • Superior opthalmic vein Inferior Orbital Fissure • Infraorbital artery, vein, and nerve (V2 branch) Optic Canal • Optic nerve • Opthalmic artery
- 29. Orbital landmarks • Superior orbital fissure • Optic canal • Inferior orbital fissure – other end of foramen rotundum • Ant. And Post. Ethmoidal foramina • Anterior & Posterior ethmoidal arteries • Foramina = constant guide to level of ethmoid roof as position of fronto-ethmoid suture.
- 30. Skull base Pathology • Intra-axial – brain lesions/tumours • Extra-axial – lesions from adjacent structures, usually from below skull base • Metastatic eg breast, lung, prostate ca
- 31. Extra- axial pathology of anterior and middle cranial fossae • Paranasal sinus Lesions • Malignant: SCC, adenocarcinoma, sarcoma, melanoma, olfactory neuroblastoma, adenoid cystic, distant mets. • Benign: mengioma juvenille nasopharyngeal angiofibroma, fibrous dysplasia, Inverting papilloma, fibro osseous disease
- 32. Paranasal sinus malignancy • Maxillary sinus carcinoma • SCC commonest • T4b- involvement of dura, brain, clivus, nasopharynx (inoperable) • Multiplanar CT with contrast and MRI to fully assess – unilateral sinus mass with bony wall destruction (sinus wall is rarely expanded). • MRI good for perineural, dural and intra cranial spread
- 33. Extra-axial pathology of posterior cranial fossa • CPA lesions • Acoustic neuromas, meningioma’s, other neuromas (rare eg VII nerve neuroma), epidermoids, glomus tumours, arachnoid cysts, haemangiomas • Rare – mets, chordomas, chondrosarcoma, lipoma, dermoids, teratomas • Petrous apex lesions • Cholesterol granuloma, cholesteatoma, meningioma, asymmetric petrous( extra bone marrow – can be mistaken for neoplasm!), mucocele, petrous ICA aneurysm, giant cell tumour.
- 34. Intra-axial Pathology of skull base • Brainstem – gliomas (commonest CPA tumour in children) • Cerebellum/ brain – medulloblastomas, astrocytomas, haemangioblastomas • Fourth ventricle – choroid plexus papillomas, ependymomas Brainstem Glioma
- 35. Case 1
- 36. Chondrosarcom a CT Findings: • Irregular, destructive mass • Centered off midline • Petro-occipital fissure • Calcifications, 70%; “rings/arcs” MRI Findings: • Low T1 signal, high T2 signal • Enhance with contrast • Scalloped, well circumscribed margins
- 37. Chondrosarcoma Origin: • Preexisting cartilaginous lesion, synchondroses, cartilage endplates Location: • Paranasal sinuses, skull base, parasellar region • Long bones, pelvis, sternum, ribs Clinical: • 45 yo, median age • Classic, mesenchymal, or undifferentiated
- 38. Case 2
- 39. CT/MRI Findings: • Expansile lytic lesion, midline • Well delineated mass arising from bone • Large soft tissue component • Variable calcification • Anteroposterior extension • Heterogeneous enhancement on T1, T2 • Dark on T1, bright on T2 Chordoma Diff. Dx: • Chondroma • Chondrosarcoma • Clivus meningioma
- 40. Chordoma Origin • Notochord remnants Location • Clivus 35% • Sacrum 50%, Vertebral bodies 15% Clinical • age 30-70 • Slow growing, locally aggressive • CN VI- CN deficits • Mets late • Tx: surgery, radiation
- 41. Case 3
- 42. Glomus Tumor Glomus jugulare CT/MRI Findings: • Center: jugular foramen • Limit: hyoid bone • Enhance w/ contrast • Salt and pepper appearance on MRI • Bone erosion
- 43. Glomus Tumor Origin: • Chemoreceptor cells Location: • 10% multiple • glomus jugulare: jugular bulb • glomus tympanicum: cochlear promontory; Clinical: • Pulsatile tinnitus • Hearing loss • arrythmia, BP fluctuation
- 44. Hints and tips! • MRI-Talk about signal intensity (low vs high) • Marrow=hyper intense • Bone=hypointense • High flow blood vessels – black on MR • MRI T1weighted • water=black • Fat=white • Look for CSF around spinal cord to see • MRI T2 weighted • Water=white • Fat=black • Nodes show up brighter on T2 as cystic necrosis
- 45. Hints and tips - MRI • Lipomas signal suppresion on STIR • Adenoid cystics – peri neural spread seen only after gadolinium contrast on T1 – makes them shine! • Parapharyngeal space –Schwannomas and paragangliomas are behind carotid so push carotid antero-medially and up to skull base. Best seen on T1 after gadolinium • Paragangliomas – look shaggy, light up quickly with contrast then wash out • Schwannomas – look smooth and have delayed enhancement after contrast Paraganglioma on T2 Lipoma at petrous apex
- 46. Hints and tips - MRI • Glomus Jugulare – slow growing, shows irregular bone destruction • Fibrous dysplasia – inhomogenous enhancement • Meningioma – bright on T1 and light up with gadolinium, broad based and dural tail
- 48. For Other powerpoint presentatioins of “ Skull base 360° ” I will update continuosly with date tag at the end as I am getting more & more information click www.skullbase360.in - you have to login to slideshare.net with Facebook account after clicking www.skullbase360.in
Editor's Notes
- Supra-orbital foramen Transmits supra orbtal nerve and vessels –supply galae and frontal pericranium Intracranial landmarks: foramen ceacum – nasal veins communicate with sup saggital sinus crista galli – attachment for falx cerebri cribiform plate- 20 olfactory nerves each side planum sphenoidal- roof of sphenoid sinus
- F.S.: V3 recurrent = mandibular branch. Emissary veins in FS and FO connect cavernous sinus with pterygoid plexus of veins = path for nasaopharyngeal tumors. Foramen of vesalius- inconstant. Anterior and medial to f. ovale. When it does occur, it contains (read slide)
- F.L.:read slide Vidian canal = aka pterygoid canal. Connects pterygopalatine fossa to foramen lacerum. Contains vidian artery (branch of maxillary artery) and nerve. Vidian nerve = formed by merger of greater superficial petrosal nerve (branch of facial nerve) and deep petrosal nerve.
- Hypoglossal artery = not always present. Sometimes, can have a small emissary vein that runs through here that can protrude into the cerebellomedullary cistern and mimic a nerve sheath tumor.
- 2 parts: Pars nervosa = anteromedial Pars vascularis aka pars venosa = posterolateral Separated by the jugular spur. Pars nervosa: glossopharyngeal nerve, inferior petrosal sinus- runs along petrooccipital fissure Pars vascularis: vagus and spinal accessory nerve Jugular bulb: confluence b/w sigmoid sinus and internal jugular vein. Anterolateral to pars nervosa = petrous portion of the carotid artery.
- PPF = conduit for spread of tumor and infection Communicates with inf orbital fissure, orbital apex,… PPF - Sphenoplatine foramen = to nasal fossa PPF – pterygomaxillary fissure = to masticator space PPF- foramen rotundum = connection with Meckel’s cave, cavernous sinus PPF- Vidian canal = to foramen lacerum PPF- to greater/lesser palatine canals = to palate
- PPF – foramen rotundum = connection with meckel’s cave, cav sinus, since we’ve mentioned it a few times now and b/c contains a lot of key elements: Cav sinus- read slide. V2- lateral wall of CS- then to foramen rotundum V1- lateral wall of cav sinus- then to superior orbital fissure, along with CN III, IV, VI
- Speaking of the superior orbital fissure… Below SOF = IOF. Optic canal = more superior to SOF.
- T1 post contrast MR showing extra axial lesion arising from the middle cranial fossa. Heterogeneous enhancement. Low signal areas = flow voids or calcs. Coronal = involvement with skull base. Mass effect on temporal lobe.
- Chondrosarcomas can occur anywhere in the skeletal system. Often = preexisting cartilaginous lesion like previously benign osteochondroma. In skull base = usually at cartilage endplates. E.g. petrooccipital suture. Location: read slide Clinical: Most commonly, patients are diagnosed with chondrosarcomas during the third or fourth decade of life. Males are affected more often than females. Chondrosarcomas can be divided into classic, mesenchymal, and dedifferentiated tumors. Mesenchymal, Dedifferentiated = high grade. Classic low grade = like chordoma. DDX: Chordoma- usually has marked bone destruction, midline (clivus) Chondrosarcoma = significant soft tissue component, little bone destruction, arcs/nodules of calcification, eccentric locations- often centered in foramen lacerum.
- Sagittal T1-weighted MR image shows a large, hypo intense soft-tissue mass that arises from the distal clivus with anterior extension into the nasopharynx (arrows) and extradural extension into the posterior fossa (arrowhead).
- CT to assess degree of bone involvement. MRI to evaluate extension of tumor. CT Findings: The most characteristic appearance of intracranial chordoma is of a centrally located homogeneous soft tissue mass arising from the clivus and causing adjacent bone destruction. Calcification is common but variable. Areas of low attenuation within the soft tissue mass occasionally are found on CT, representing the myxoid and gelatinous material found on pathologic examination. CT reliably demonstrates petrous apex involvement and lysis of the skull base foramina. MRI Findings: Mass originating from midline with extension primarily in the anteroposterior axis rather than laterally. Well delineated. Expands bone in the early stage = indicator that it arises from bone, not from adjacent structures. Post gad = lobulated area, heterogeneous on T1 and T2 b/c of mucinous and gelatinous contents. DDX: Chondroma- similar appearance but extend more laterally into sellar and cerebellopontine angles. Clivus meningioma – homogeneous signal, dural attachment
- Contrast enhanced T1 spin echo image. Chordoma of the upper part of the clivus with posterior extension into the pontine cistern. Chordomas = benign tumor but has significant problems b/c of location, local invasion, recurrence. Origin: Notochord = early fetal axial skeleton. Gets surrounded by cartilage. Cartilage ossifies and notochord = squeezed out into intervertebral regions = nucleus pulposus of intervertebral disks. Can get remnants then, along any position of the neural axis- turn into chordomas. Location: read slide. Rare. <0.2% of all intracranial tumors. Clinical:read slide CN deficits: HA, dysphagia, facial pain, facial paresis, visual loss, hearing loss, and ataxia. CT to assess degree of bone involvement. MRI to evaluate extension of tumor. CT Findings: The most characteristic appearance of intracranial chordoma is of a centrally located homogeneous soft tissue mass arising from the clivus and causing adjacent bone destruction. Calcification is common but variable. Areas of low attenuation within the soft tissue mass occasionally are found on CT, representing the myxoid and gelatinous material found on pathologic examination. CT reliably demonstrates petrous apex involvement and lysis of the skull base foramina. MRI Findings: Mass originating from midline with extension primarily in the anteroposterior axis rather than laterally. Well delineated. Expands bone in the early stage = indicator that it arises from bone, not from adjacent structures. Post gad = lobulated area, heterogeneous on T1 and T2 b/c of mucinous and gelatinous contents.
- CT imaging demonstrates the extent of bony destruction (white and black arrows) by the tumor. The normal jugular foramen on the left (arrow head) is shown for comparison.
- Salt and pepper: multiple low signal intensity areas = flow voids in tumor. When large- erode bone.
- Glomus tumors arise from chemoreceptor cells. These tumors are slow-growing hypervascular tumors that usually occur in the temporal bone. Location: read slide- check other places for them b/c = multiple. E.g. Carotid body Patients usually present with gradual hearing loss, unilateral pulsatile tinnitus, and lower cranial nerve palsies. Approximately 1-3% of gangliogliomas produce catecholamines, so can get arrythmia, BP fluctuation. May be locally invasive but rarely metastasize.