IMAGING OF SKULL BASEIMAGING OF SKULL BASE

--Dr.A.Joseph Stalin(MCh PG)Dr.A.Joseph Stalin(MCh PG)

PROF .R.R UNIT

DEPT OF SURGICAL ONCOLOGY

GOVT ROYAPETTAH HOSPITAL

CHENNAI

CONTENTSCONTENTS

1.REVIEW OF ANATOMY2.ROLE OF IMAGING3.IMPORTANT PATHOLOGICAL

LEISIONS IN IMAGING4.CLINICAL EXAMPLES

Cranial fossaCranial fossa

Skull Base Anatomy Review

Temporal Bone

Temporal bone- petrous portion

Sphenoid Bone

Occipital Bone

Key Fissures

• Petrosphenoidal fissure

• Petrooccipital fissure

Key Sutures

• Sphenosquamous Suture

• Occipitomastoid Suture

Skull Base Anatomy Review

Key Openings

• Foramen spinosum

• Foramen ovale

• Foramen lacerum

• Foramen rotundum

• Foramen magnum

• Foramen of vesalius

• Jugular foramen

• Superior orbital fissure

• Inferior orbital fissure

• Optic canal

• Vidian canal

• Hypoglossal canal

• Pterygopalatine fossa

Skull Base Anatomy Review

Skull Base Anatomy Review

Foramen spinosum

Sphenoid spine- lower level

Foramen rotundum- higher level

Pterygopalatine fossa

Foramen ovale

Petro-occipital fissure

Pterygoid canal

f. lacerum

ModalityModalityCT

CTA

SPECT

ABOX-CT

MRI

MR SPECTROSCOPY

PET CT

DSA

ROLE OF IMAGINGROLE OF IMAGING

Diagnosis Deciding Resectability Planning of Treatment- Approach

Specialist Help

Reconstruction Follow up/Recurrance

DiagnosisDiagnosis

Site ExtendConsistencyVascularityBony InvolvementPerineural spreadVascular Involvement

Characterisation of the lesionCharacterisation of the lesion

Morphology 1. tissue characterisation 2. pattern of bone involvment 3. vascularity Localisation 1. intrinsic to the skull base 2. arising from intracranial compartment 3. arising from extracranial head and neck Invasion of other structures 1. Direct extension

• infiltrating bone, soft tissue, meninges, cerebrum• preformed channels and foramina

2. Hematogenous spread 3. Perineural spread

Agressive bone involvement patternAgressive bone involvement pattern

Osteolysis Absent bone replaced by soft tissue Thinned bone with soft tissue mass on

its both sides Abnormal signal of the bone marrow Calcifications within the soft tissue mass

Non-aggressive bone involvement patternNon-aggressive bone involvement pattern Bone remodeling with bowing, thin or demineralized walls Bone expansion with smooth contour or interrupted walls Enlarged intramedullary cavity Varying attenuation: ground-glass, radiolucent or sclerotic

INTRACRANIAL <> EXTRA CRANIALINTRACRANIAL <> EXTRA CRANIAL

Pharygeal mucosal space PMS Sinus Morgagni Parapharyngeal space PPS Skull base Carotid space CS Carotid canal Jugular foramen Mandibular space MS Foramen ovale Retropharyngeal space RPS Basiocciput

Sinus frontalis Squamous Cell Sinus frontalis Squamous Cell Cancer with intracranial Cancer with intracranial

spread spread

Nodular dural enhancing have high specificity

Dural thickness > 5 mm Coexistent leptomeningeal

enhancement Hypointense leision Brain parenchymal changes

Perineural spreadPerineural spread

Nerve enlargement and nerve enhancement Obliteration of the fat in the foramina, fosse or fissures Foraminal enlargement or destruction Enhancing soft tissue in the cavernous sinus and Meckel cave Neuropathic atrophy and fat replacement

Tumor growth Tumor growth

Incresed permeability of endoneurial capillariesIncresed permeability of endoneurial capillaries

Rupture of the blood-nerve barrierRupture of the blood-nerve barrier

Contrast-enhancementContrast-enhancement

Dural, PeriNeuralSpreadDural, PeriNeuralSpread

Ethmoidal Adenocarcinoma with Ethmoidal Adenocarcinoma with perineural spread in pterigopalatine fossaperineural spread in pterigopalatine fossa

Cavernous sinus infiltrationCavernous sinus infiltration

Internal carotid artery Internal carotid artery encasementencasement

ABOX CTABOX CT

ABOX-CTABOX-CT

Imaging ChecklistImaging Checklist

Bony involvement- site/extensionScan all FORAMINA- content involvementSA plane/Dural/Brain involvementCarotid Sinus/other sinusesInternal Carotid Artery course/encasementPerineural spread

CRITERIA FOR NON CRITERIA FOR NON RESECTABILITY RESECTABILITY

Cavernous sinus infiltration

B/l optic nerve/optic chiasmal infiltration

Sphenoid sinus infiltration (superior/lateral )

Extensive brain involvement- temporal lobe for anterior resection

Skull Base Pathology

Chordoma

Chondrosarcoma

Dermoid tumors

Epidermoid tumors

Glomus tumors

Meningioma

Metastases

Myeloma

Neuroma

Schwannoma

Vascular Aneurysm

ANTERIOR SKULL BASEANTERIOR SKULL BASE

MENINGIOMA

SINONASAL MALIGNANCY

OLFACTORY NEUROBLASTOMA

MIDDLE SKULL BASEMIDDLE SKULL BASE

Pituitary adenomaCraniopharyngiomaSphenoid sinus malignancySchwanoma

POSTERIOR SKULL BASEPOSTERIOR SKULL BASE

ChordomaAcoustic neuromaChondrosarcomaParaganglioma

SINONASAL MALIGNANCYSINONASAL MALIGNANCY

Bony invasionBony invasion

Bone marrow spaceBone marrow space

Pterygopalatinefossa Pterygopalatinefossa infiltrationinfiltration

orbitorbit

Occular muscleOccular muscle

Normal ethamoid sinusNormal ethamoid sinus

Ethamoid tumourEthamoid tumour

EsthenioneuroblastomaEsthenioneuroblastoma

Anterior cranial fossa tumour Anterior cranial fossa tumour with dural involvementwith dural involvement

CarotidvesselsCarotidvessels

Encased carotidEncased carotid

Cavernous sinus infiltrationCavernous sinus infiltration

Perinueral spreadPerinueral spread

Case 1

Chondrosarcoma

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 circumsribed margins

ChondrosarcomaOrigin:

• 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 dedifferentiated

Case 2

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

Differential Diagnosis:

• Chondroma

• Chondrosarcoma

• Clivus meningioma

ChordomaOrigin

• 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

Case 3

Glomus Tumor

Glomus jugulare CT/MRI Findings:

• Center: jugular foramen

• Limit: hyoid bone

• Enhance w/ contrast

• Salt and pepper appearance on MRI

• Bone erosion

Glomus Tumor

Origin:

• Chemoreceptor cells

Location:

• 10% multiple

• glomus jugulare: jugular bulb

• glomus tympanicum: cochlear promontory

Clinical:

• Pulsatile tinnitus

• Hearing loss

• arrythmia, BP fluctuation

CONCLUSIONCONCLUSION

Thorough anatomical knowledge essential.Both CT and MRI are needed. Histological diagnosis not needed for

managing skull base tumours.Main role of imaging is to plan the

recection .Treatment options for skull base tumours –

resection +/_ radiotherapy

CONCLUSIONCONCLUSION

Anatomy of skull base – complex – not the imaging

Treatment options –simple- not the procedure

Thank u….Thank u….