U.C. Irvine - Otolaryngology-Head & Neck Surgery Posterior Fossa Skull Base Posterior Fossa Skull Base Lesions Lesions Ali Sepehr UCI Department of Otolaryngology- Head and Neck Surgery
Jul 16, 2015
U.C. Irvine - Otolaryngology-Head & Neck
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Posterior Fossa Skull Base Posterior Fossa Skull Base LesionsLesionsAli Sepehr
UCI Department of Otolaryngology- Head and Neck Surgery
U.C. Irvine - Otolaryngology-Head & Neck
Surgery
Posterior fossa skull base lesionsPosterior fossa skull base lesions
Common–Acoustic neuroma (60-92%)–Meningioma (3-7%)–Epidermoid (2-6%)–Non-AN (1%)–Paraganglioma –Arachnoid cyst–Hemangioma
Uncommon–Metastatic tumor–Lipoma–Dermoid–Teratoma–Chordoma–Chondrosarcoma–Giant cell tumor
• CPA
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CPACPA
Borders– Medial – lateral surface of the brainstem– Lateral – petrous bone– Superior – middle cerebellar peduncle &
cerebellum– Inferior – arachnoid tissue of lower cranial
nerves– Posterior – inferior cerebellar peduncle
U.C. Irvine - Otolaryngology-Head & Neck
Surgery
Skull base lesions (cont.)Skull base lesions (cont.) Petrous apex
– Cholesterol granuloma– Epidermoid– Asymmetric pneumatization– Retained mucus or mucocele– Petrous carotid artery aneurysm
Intra-axial– Hemangioblastoma– Medulloblastoma– Astrocytoma– Glioma– Fourth ventricle tumor
U.C. Irvine - Otolaryngology-Head & Neck
Surgery
U.C. Irvine - Otolaryngology-Head & Neck
Surgery
U.C. Irvine - Otolaryngology-Head & Neck
Surgery
U.C. Irvine - Otolaryngology-Head & Neck
Surgery
Acoustic Neuroma (AN)Acoustic Neuroma (AN)Benign schwann cells in collagenous matrix
and don’t invade (usually cause symptoms by encroaching)
Usually arise from vestibular (95%) nerve in IAC but if they arise medial then symptoms develop later
95% are unilateral and nonhereditaryM = FSlow growing (0.2-4mm/yr)
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Growth phasesGrowth phases IAC
– acoustic and facial nerve compression
Cisternal– blood from brainstem
Brainstem compression– 4th ventricle compression
occurs at 2-3 cm
U.C. Irvine - Otolaryngology-Head & Neck
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HistopathologyHistopathology– Antoni A – compact
tissue with spindle cells in palisades (most common)
– Antoni B – loose tissue with cyst formation.
U.C. Irvine - Otolaryngology-Head & Neck
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Hereditary AN’sHereditary AN’s
Type I–Only 5% with AN’s and no bilateral AN’s–Intra and extra-cranial–Appear late–Chromosome 17
Type II–Bilateral AN’s in 96%–Cranial nerve schwannomas–Appear by 2nd decade–Chromosome 22
• Neurofibromatosis
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Signs and symptomsSigns and symptoms
SNHL (95%),SSNHL (20%), tinnitus (56%)Dysequilibrium (50%), vertigo, nystagmusFacial hypesthesia and loss of corneal reflexLong tract signs, ataxiaHeadaches and nauseaHitselberger sign
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Diagnostic studiesDiagnostic studies
Auditory and vestibular testing– Audiometry– ABR
Decreasing sensitivity with smaller tumors 90% sensitive with all tumors 58% with tumors < 1cm
– Vestibular tests
U.C. Irvine - Otolaryngology-Head & Neck
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ImagingImaging
MRICT
U.C. Irvine - Otolaryngology-Head & Neck
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U.C. Irvine - Otolaryngology-Head & Neck
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MeningiomaMeningioma Originate cap cells near arachnoid villi which are more
prominent near cranial nerve foramina and venous sinuses. Grossly appear speckled due to psammoma bodies 25% Cause hyperostosis Same symptoms as AN but arise from posterior surface of
petrous bone so audiometric (75% HL) and vestibular testing is less sensitive.
Only 75% have abnl ABR Histopathologic subtypes
– Syncitial– Transitional– Fibrous– Angioblastic– Sarcomatous
U.C. Irvine - Otolaryngology-Head & Neck
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U.C. Irvine - Otolaryngology-Head & Neck
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EpidermoidEpidermoid
Originates from epithelial rests within temporal bone or CPA.
Stratified squamous epithelial cells lining desquamated keratin
Same symptoms as AN but facial tic and paresis more common
Expand along least resistance so irregular shapes and borders and discovered in 2nd-4th decades.
U.C. Irvine - Otolaryngology-Head & Neck
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EpidermoidEpidermoid
DDX– Cholesterol granuloma - Hemorrhage into
petrous apex air cells with foreign body reaction and granuloma formation
– Arachnoid cysts smooth surfaced sac containing CSF Low intensity on DWI MR whereas epidermoid has
moderate intensity
U.C. Irvine - Otolaryngology-Head & Neck
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U.C. Irvine - Otolaryngology-Head & Neck
Surgery
U.C. Irvine - Otolaryngology-Head & Neck
Surgery
Non-acoustic neuromasNon-acoustic neuromas V VII
– Facial weakness is a late finding unless location is intratemporal
– Facial tic IX-XI
– Smooth enlargement of the jugular foramen – Jugular foramen syndrome; soft palate (dysphagia);
vocal cords (hoarseness, aspiration); shoulder (numbness and weakness)
XII – enlargement of hypoglossal canal and hemiatrophy of the tongue
U.C. Irvine - Otolaryngology-Head & Neck
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U.C. Irvine - Otolaryngology-Head & Neck
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Glomus tumorsGlomus tumors
Order of symptoms: pulsatile tinnitus, conductive loss.
Deficits of the cranial nerves of the jugular foramen
Irregular destruction of jugular foramen on CT
Flow voids cause “salt and pepper” appearance on T1 and T2
Characteristic angiography pattern
U.C. Irvine - Otolaryngology-Head & Neck
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U.C. Irvine - Otolaryngology-Head & Neck
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HemangiomasHemangiomas
Arise in area of geniculate ganglionPulsatile tinnitusEarly facial weaknessEnhancingHoneycomb bone with irreagular and
indistinct margins and intratumoral bone spicules
U.C. Irvine - Otolaryngology-Head & Neck
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U.C. Irvine - Otolaryngology-Head & Neck
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Lipomas and Asymmetric Lipomas and Asymmetric petrous apex pneumatizationpetrous apex pneumatization
Fat content on less pneumatized side appears hyperintense on T1
Lack of bone destruction or expansion, non-enhancing, and hypointense on T2
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Other petrous apex tumorsOther petrous apex tumors
Mucocele – Nonenhancing mass; hypointense on T1 and hyperintense on T2,
Petrous carotid aneurysm – can be confused with chondrosarcoma
Giant cell tumors – originate from supporting connective tissue cells and consist of multinucleated giant cells in spindle-shaped stromal cells
U.C. Irvine - Otolaryngology-Head & Neck
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U.C. Irvine - Otolaryngology-Head & Neck
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ChordomaChordoma
Arise from notochord remnantsCause extensive bone destructionUsually present with frontoorbital
headaches and changed vision (diplopia, decreased acuity, visual field deficits)
Homogeneous and enhance on CT with bony destruction
Isointense on T1 and hyperintense on T2
U.C. Irvine - Otolaryngology-Head & Neck
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U.C. Irvine - Otolaryngology-Head & Neck
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Approach to TreatmentApproach to Treatment
Preservation of life– Mass effect, hydrocephalus
Preservation of function:– Facial nerve– Hearing nerve– Balance nerve
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ObservationObservation Indications
– Advanced age (over 65 or 75)– Poor health– Small tumors, especially if hearing is good– Lack of symptoms– Non-progression of symptoms– Only hearing ear– Isolated IAC tumors in the elderly– Slow growth 1-3mm/yr
Contraindications– Young patient– Healthy patient– Symptomatic progression– Compression of brainstem structures– Cystic tumors
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Stereotactic RadiosurgeryStereotactic Radiosurgery Examples:
– Gamma knife– Linac
Cyber knife X knife Novalis Peacock
– Proton beam Indications
– Small tumors (< 3 cm) who have very characteristic radiographic appearance– Funtional hearing– Older patients (>75)– Medically unstable patients– Previous resection– Young patients who don’t want surgery
U.C. Irvine - Otolaryngology-Head & Neck
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Stereotactic RadiosurgeryStereotactic Radiosurgery Contraindications
– Tumors > 3 cm– Prior radiotherapy– Tumor compressing brainstem– Uncertain diagnosis– Dizzy patients– Facial nerve symptoms– Cystic Tumors
Outcome– 94% Local control = 62% smaller, 32% unchanged, 6% larger– 51% no change hearing
Complications– Early
Facial nerve injury: 5 - 17% trigeminal hypesthesia: 27% Hyrodcephalus: 3% 7% imbalance
U.C. Irvine - Otolaryngology-Head & Neck
Surgery
Stereotactic RadiosurgeryStereotactic Radiosurgery Complications
– Early Facial nerve injury: 5 - 17% trigeminal hypesthesia: 27% Hyrodcephalus: 3% 7% imbalance
– Early Benign tumor formation (16-30 yrs) Malignant tumor formation (4-5 yrs)
U.C. Irvine - Otolaryngology-Head & Neck
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SurgerySurgery
Approaches– Translabyrinthine– Middle Fossa– Retrosigmoid
Considerations– Size– Hearing– Age
U.C. Irvine - Otolaryngology-Head & Neck
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Trans-labrynthineTrans-labrynthine
Indications– Extension into CPA > 0.5 - 1cm– Non-serviceable hearing
Average hearing 50dB Speech discrim 50%
– Adequate contralateral hearing in large tumors (>2.5cm)
Contraindications– Serviceable hearing
U.C. Irvine - Otolaryngology-Head & Neck
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TranslabyrinthineTranslabyrinthine Advantages
– No retraction of cerebellum
– Allows good identification of CN VII
– Allows good exposure of IAC
– Less risk of CSF leak
Disadvantages– Hearing is sacrificed
U.C. Irvine - Otolaryngology-Head & Neck
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Middle FossaMiddle Fossa Indications
– Small tumor– Intracanallicular tumor– Moderate CPA involvement (<1cm)– Adequate hearing (SRT<50 db, Disc >50%)
Contraindications– Large tumors– Extensive CPA involvement ( > 0.5 – 1 cm)– Older patients ( > 60 yrs. may have higher rate of bleeding
or stroke)
U.C. Irvine - Otolaryngology-Head & Neck
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Middle Fossa ApproachMiddle Fossa ApproachAdvantages
– Excellent for intracanalicular tumors, especially at the lateral end of the IAC
– Hearing preservation is possible– Extradural with low risk of CSF leak
Disadvantages– Lack of access to CPA and posterior fossa– Need to retract temporal lobe
U.C. Irvine - Otolaryngology-Head & Neck
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Middle Fossa ApproachMiddle Fossa Approach
U.C. Irvine - Otolaryngology-Head & Neck
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Middle Fossa CraniotomyMiddle Fossa Craniotomy
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Retrosigmoid/SuboccipitalRetrosigmoid/SuboccipitalApproachApproach
Indications– Serviceable hearing– Large tumors– Compression of brainstem
Contraindications– Functional hearing with
extensive IAC involvement– Intracanallicular tumors
U.C. Irvine - Otolaryngology-Head & Neck
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Retrosigmoid/SuboccipitalRetrosigmoid/SuboccipitalApproachApproach
Advantages– Hearing preservation is possible– Access to CPA
Disadvantages– Limited access to lateral IAC/Fundus– Difficulty repairing or grafting CN VII– Increased risk of air embolism/CSF leak/
post-op headache – Cerebellar retraction is necessary
U.C. Irvine - Otolaryngology-Head & Neck
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Retrosigmoid/Suboccipital Retrosigmoid/Suboccipital ApproachApproach