Cerebellopontine Angle Cerebellopontine Angle MassesMasses

ALI SAFAR - PGY4ALI SAFAR - PGY4

November 09, 05November 09, 05

University of OttawaUniversity of Ottawa

ENT Dept. Grand RoundsENT Dept. Grand Rounds

IntroductionIntroduction 10% of all intracranial tumors.10% of all intracranial tumors. Fatal without treatment.Fatal without treatment. 78% are acoustic neuromas- mostly on 78% are acoustic neuromas- mostly on

vestibular branch.vestibular branch. Other CPA masses:Other CPA masses:

MeningiomasMeningiomas CN schwannomasCN schwannomas Dermoid tumorsDermoid tumors Arachnoid cystsArachnoid cysts Lipomas, metastatic tumorsLipomas, metastatic tumors Vascular tumorsVascular tumors

AnatomyAnatomy Potential space in the posterior fossa of Potential space in the posterior fossa of

the brain.the brain. CPA boundries:CPA boundries:

Anterior: posterior surface of temporal boneAnterior: posterior surface of temporal bone Posterior: anterior surface of the cerebellumPosterior: anterior surface of the cerebellum Medial: lateral surface of brainstemMedial: lateral surface of brainstem Lateral: petrous boneLateral: petrous bone Superior: inferior border of pons & cerebellar Superior: inferior border of pons & cerebellar

pedunclepeduncle Inferior: cerebellar tonsilInferior: cerebellar tonsil

Cranial nerves: Cranial nerves: VII & VIIIVII & VIII VV IX, X, XIIX, X, XI

Important structures:Important structures: FlocculusFlocculus Lateral aperture of 4Lateral aperture of 4thth

ventricalventrical AICAAICA

Acoustic Neuroma 60 - 92%Acoustic Neuroma 60 - 92% MeningiomaMeningioma Epidermoids Epidermoids Rare CPA lesionsRare CPA lesions Petrous Apex massesPetrous Apex masses Vascular malformationsVascular malformations Intra-axial massesIntra-axial masses

DifferentialDifferential

Acoustic NeuromaAcoustic Neuroma Comprises 60-92% of CPA lesions.Comprises 60-92% of CPA lesions. Usually unilateral.Usually unilateral. Arise from schwann cells, commonly within IAC.Arise from schwann cells, commonly within IAC. Occur with equal frequency on the Superior & Occur with equal frequency on the Superior &

Inferior vestibular nerves.Inferior vestibular nerves. Greatest density of S. cells at scarpa ganglion.Greatest density of S. cells at scarpa ganglion. Majority of cases (95%) are sporadic.Majority of cases (95%) are sporadic. Rarely occur on the cochlear division of the 8Rarely occur on the cochlear division of the 8thth

CN.CN.

Acoustic NeuromaAcoustic Neuroma Type 2 NF:Type 2 NF:

Genetic defect on long arm of Genetic defect on long arm of chromosome 22.chromosome 22.

Autosomal-dominant.Autosomal-dominant. Bilateral or early in life.Bilateral or early in life. Assoc. with intracranial meningiomas & Assoc. with intracranial meningiomas &

spinal cord tumors.spinal cord tumors. Tumors supressor gene is absent.Tumors supressor gene is absent.

PathologyPathology

Composed of Antoni A&B tissue.Composed of Antoni A&B tissue.

Antoni A – compact tissue with spindle Antoni A – compact tissue with spindle cells in palisades (most common).cells in palisades (most common).

Antoni B – loose tissue with cyst Antoni B – loose tissue with cyst formation.formation.

AN ManifestationsAN Manifestations Cochlear:Cochlear:

Asymmetric SNHLAsymmetric SNHL SSNHL SSNHL

Up to 26% of AN may present with SSNHLUp to 26% of AN may present with SSNHL Only 1-2.5% of SSNHL is due to ANOnly 1-2.5% of SSNHL is due to AN

TinnitusTinnitus Decreased discriminationDecreased discrimination Rollover phenomenonRollover phenomenon

Vestibular:Vestibular: Dysequilibrium (more common)Dysequilibrium (more common) Vertigo (less common)Vertigo (less common)

Facial:Facial: Facial weakness (suspect other tumors - epidermoid)Facial weakness (suspect other tumors - epidermoid) Hitselberger’s sign – decreased sensation of EAC due to Hitselberger’s sign – decreased sensation of EAC due to

compression of CN VII sensory rootscompression of CN VII sensory roots

AN ManifestationsAN Manifestations Cerebellar:Cerebellar:

Wide gaitWide gait Falling to side of lesionFalling to side of lesion

Brainstem:Brainstem: HeadacheHeadache Visual LossVisual Loss

Other Cranial nerves:Other Cranial nerves: V – facial numbness (large tumors, trigeminal schwannoma)V – facial numbness (large tumors, trigeminal schwannoma) VI – lateral rectus palsy (rare)VI – lateral rectus palsy (rare) IX – dysphagia (large tumors, J F S)IX – dysphagia (large tumors, J F S) X – hoarseness, aspiration (large tumors, J F S)X – hoarseness, aspiration (large tumors, J F S) XI – shoulder weakness (large tumors, J F S)XI – shoulder weakness (large tumors, J F S)

Diagnostic TestsDiagnostic Tests

Audiometric Testing.Audiometric Testing. Electrophysiologic Testing.Electrophysiologic Testing. Vestibular Testing.Vestibular Testing. CT & MRI.CT & MRI.

Audiometric TestingAudiometric Testing Pure-tone testing:Pure-tone testing:

SNHL- most commonly high frequency (65%).SNHL- most commonly high frequency (65%). Normal hearing (5%).Normal hearing (5%).

Speech discrimination:Speech discrimination: Scores out of proportion with pure-tone Scores out of proportion with pure-tone

thresholds.thresholds. Some may score well.Some may score well. Rollover phenomenon improve the sensitivity.Rollover phenomenon improve the sensitivity.

Acoustic reflex thresholds:Acoustic reflex thresholds: typically elevated or absent.typically elevated or absent. If present then reflex If present then reflex decay decay measured.measured. The sensitivity is 85% for detecting retrocochlear The sensitivity is 85% for detecting retrocochlear

problem.problem.

Electrophysiologic TestingElectrophysiologic Testing ABR:ABR:

Most sensitive & specific audiologic test.Most sensitive & specific audiologic test. Abnormalities seen:Abnormalities seen:

Interaural difference in latency of wave 5 Interaural difference in latency of wave 5 with delay of more than 0.2 msec (40-60%).with delay of more than 0.2 msec (40-60%).

No identifiable wave forms in 20-30%.No identifiable wave forms in 20-30%. Wave 1 present but all remaining waves are Wave 1 present but all remaining waves are

absent in 10-20%.absent in 10-20%. Normal in 10-15%.Normal in 10-15%.

Vestibular TestingVestibular Testing

ENG:ENG: Abnormal in 70-90%.Abnormal in 70-90%. Unilateral weakness in caloric testing.Unilateral weakness in caloric testing. Spontaneous nystagmus.Spontaneous nystagmus. Only test superior nerve.Only test superior nerve. No abnormality for smaller tumors.No abnormality for smaller tumors.

Computerized dynamic Computerized dynamic posturography.posturography.

Rotary chair testing.Rotary chair testing.

Imaging TechniquesImaging Techniques CTCT

Non-contrastedNon-contrasted Iodine based contrast - uptake by selected Iodine based contrast - uptake by selected

lesionslesions CT air cisternogram – no longer performedCT air cisternogram – no longer performed

MRIMRI T1W – Fat density is brightT1W – Fat density is bright T2W – Water density is brightT2W – Water density is bright FLAIR (Fluid Attenuated Inversion FLAIR (Fluid Attenuated Inversion

Recovery)Recovery) GadoliniumGadolinium

Radiologic Features of ANRadiologic Features of AN CTCT

Non-contrast: usually isodense to brain, Non-contrast: usually isodense to brain, calcification is rarecalcification is rare

IV Contrast: Over 90% of non-treated tumors IV Contrast: Over 90% of non-treated tumors enhance homogeneouslyenhance homogeneously

MRIMRI T1W – isointense to brain, hyperintense to CSFT1W – isointense to brain, hyperintense to CSF T2W – hyperintense to brain, iso/hypo-intense T2W – hyperintense to brain, iso/hypo-intense

to CSFto CSF Gadolinium – Intense enhancement of tumor Gadolinium – Intense enhancement of tumor

on T1W on T1W

AN FeaturesCentered on Porus acousticus.Acute angles to petrous boneOften involves the IACHomogeneous enhancementNo dural tailNo calcifications

MeningiomaMeningioma Second most common CPA lesion 3-7 %.Second most common CPA lesion 3-7 %. Arise from cap cells near arachnoid villi which are Arise from cap cells near arachnoid villi which are

more prominent near cranial nerve foramina and more prominent near cranial nerve foramina and venous sinuses.venous sinuses.

Usually arise from posterior surface of the petrous Usually arise from posterior surface of the petrous bone and usually do not extend into IAC.bone and usually do not extend into IAC.

SymptomsSymptoms Ataxia.Ataxia. Nystagmus.Nystagmus. Facial hypesthesia.Facial hypesthesia. Audiologic findings may show retrocochlear pattern or Audiologic findings may show retrocochlear pattern or

may be normal.may be normal.

MeningiomaMeningioma Radiologic featuresRadiologic features

Tumors generally hemispherical with obtuse Tumors generally hemispherical with obtuse angles to petrous boneangles to petrous bone

Dural tail often present (50-75%)Dural tail often present (50-75%) May herniate into middle fossa (50%)May herniate into middle fossa (50%) May show calcification (25%)May show calcification (25%) Pial blood vessels with flow voids may be Pial blood vessels with flow voids may be

present at the margins.present at the margins. TreatmentTreatment

Surgical removal is treatment of choiceSurgical removal is treatment of choice XRT if complete excision not possibleXRT if complete excision not possible

Meningioma Features:

• Arise from surface of petrous bone.• Obtuse angles to petrous bone.• Uncommonly involves the IAC.• Frequently with dural tail.• Calcifications common.• Pial vessel flow voids.

EpidermoidEpidermoid Accounts for 2-6% of CPA massesAccounts for 2-6% of CPA masses Physiology:Physiology:

Congenital lesions that present in adulthoodCongenital lesions that present in adulthood Rests of ectodermal tissue containing stratified Rests of ectodermal tissue containing stratified

squamous lining and keratinsquamous lining and keratin May arise within the temporal bone or in the May arise within the temporal bone or in the

CPACPA Benign and slow growingBenign and slow growing SymptomsSymptoms

Similar to acoustic neuroma and meningiomaSimilar to acoustic neuroma and meningioma Facial nerve paresis and facial twitching may occurFacial nerve paresis and facial twitching may occur

EpidermoidEpidermoid Radiologic FeaturesRadiologic Features

May dumbell into middle fossa or contralateral May dumbell into middle fossa or contralateral cisterncistern

Highly variable in shape with a cauliflower surface Highly variable in shape with a cauliflower surface appearanceappearance

CT CT mass hypodense to CSFmass hypodense to CSF Do not enhanceDo not enhance

MRI – homogeneous lesion MRI – homogeneous lesion T1 – isointense to CSFT1 – isointense to CSF T2 – isointense to CSFT2 – isointense to CSF

Differentiation from arachnoid cyst may be difficultDifferentiation from arachnoid cyst may be difficult Diffusion weighting will show moderate intensity for Diffusion weighting will show moderate intensity for

epidermoids, but low intensity for arachnoid cysts.epidermoids, but low intensity for arachnoid cysts.

Arachnoid CystArachnoid Cyst

Other Extra-axial MassesOther Extra-axial Masses

PrimaryPrimary Arachnoid CystArachnoid Cyst Schwannomas (CN V-XII)Schwannomas (CN V-XII) HemangiomasHemangiomas LipomaLipoma Dermoid/TeratomaDermoid/Teratoma

SecondarySecondary ParagangliomaParaganglioma ChondromaChondroma ChordomaChordoma

Extension of Petrous bone tumorsExtension of Petrous bone tumors

SchwannomasSchwannomas CN VIICN VII

Symptoms may be identical to acoustic schwannomaSymptoms may be identical to acoustic schwannoma Differentiation from acoustic schwannoma may not be Differentiation from acoustic schwannoma may not be

possible by radiography unless lesion extends distal to possible by radiography unless lesion extends distal to geniculate ganglion.geniculate ganglion.

CN IX – XICN IX – XI Jugular Foramen syndromeJugular Foramen syndrome

DysphagiaDysphagia HoarsenessHoarseness Shoulder weaknessShoulder weakness

Enlargement of Jugular ForamenEnlargement of Jugular Foramen CN XIICN XII

Hemiatrophy of tongueHemiatrophy of tongue Enlargement of hypoglossalEnlargement of hypoglossal

CN V SchwanomaCN V Schwanoma

CN VII SchwanomaCN VII Schwanoma

CN XCN X SchwanomaSchwanoma

VascularVascular Vertebrobasilar dolichoectasiaVertebrobasilar dolichoectasia

Enlongation and dilatation of the Enlongation and dilatation of the vertebrobasilar artery. vertebrobasilar artery.

Symptomas - Facial spasm, trigeminal neuralgiaSymptomas - Facial spasm, trigeminal neuralgia AICA loopAICA loop

May loop over, under, or between CN VII & CN May loop over, under, or between CN VII & CN VIII.VIII.

Symptoms - vertigoSymptoms - vertigo Giant Aneurysms Giant Aneurysms HemangiomaHemangioma Paragangliomas (may extend to CPA)Paragangliomas (may extend to CPA)

Glomus JugulareGlomus Jugulare Glomus TympanicumGlomus Tympanicum

Vertebrobasilar Vertebrobasilar DolichoectasiaDolichoectasia

AICA loopAICA loop

Giant AneurysmsGiant Aneurysms

Glomus JugulareGlomus Jugulare

Petrous ApexPetrous Apex

Cholesterol granulomas (most Cholesterol granulomas (most common)common)

Epidermoid cystEpidermoid cyst Trigeminal schwannomaTrigeminal schwannoma Carotid artery aneurysmCarotid artery aneurysm ChondromaChondroma ChondrosarcomaChondrosarcoma

Cholesterol GranulomasCholesterol Granulomas

Intra-axialIntra-axial

AstrocytomaAstrocytoma EpendymomaEpendymoma MedulloblastomaMedulloblastoma Hemangioma / HemangioblastomaHemangioma / Hemangioblastoma Choroid plexus papillomaChoroid plexus papilloma MetastasisMetastasis

TreatmentTreatment

ObservationObservation SurgerySurgery

TranslabrynthineTranslabrynthine RetrosigmoidRetrosigmoid Middle FossaMiddle Fossa

RadiotherapyRadiotherapy Conventional radiation therapyConventional radiation therapy Stereotactic radiosurgeryStereotactic radiosurgery

ObservationObservation IndicationsIndications

Advanced age (over 65 or 75)Advanced age (over 65 or 75) Poor healthPoor health Lack of symptomsLack of symptoms Non-progression of symptomsNon-progression of symptoms Only hearing earOnly hearing ear Isolated IAC tumors in the elderlyIsolated IAC tumors in the elderly

ContraindicationsContraindications Young patientYoung patient Healthy patientHealthy patient Symptomatic progressionSymptomatic progression Compression of brainstem structuresCompression of brainstem structures

Trans-labrynthineTrans-labrynthine

IndicationsIndications Extension into CPA > 0.5 - 1cmExtension into CPA > 0.5 - 1cm Non-serviceable hearingNon-serviceable hearing Adequate contralateral hearing in large Adequate contralateral hearing in large

tumorstumors ContraindicationsContraindications

Serviceable hearingServiceable hearing

Middle FossaMiddle Fossa

IndicationsIndications Small tumorSmall tumor Intracanallicular tumorIntracanallicular tumor Moderate CPA involvementModerate CPA involvement Adequate hearing (SRT<50 db, Disc >50%)Adequate hearing (SRT<50 db, Disc >50%)

ContraindicationsContraindications Large tumorsLarge tumors Extensive CPA involvement ( > 0.5 – 1 cm)Extensive CPA involvement ( > 0.5 – 1 cm) Older patients ( > 60 yrs. may have higher rate Older patients ( > 60 yrs. may have higher rate

of bleeding or stroke)of bleeding or stroke)

RetrosigmoidRetrosigmoid

IndicationsIndications Serviceable hearingServiceable hearing Large tumorsLarge tumors Compression of brainstemCompression of brainstem

ContraindicationsContraindications Functional hearing with extensive IAC Functional hearing with extensive IAC

involvementinvolvement Intracanallicular tumorsIntracanallicular tumors

Stereotactic RadiosurgeryStereotactic Radiosurgery IndicationsIndications

Small tumorsSmall tumors Functional hearingFunctional hearing Older patients (>75)Older patients (>75) Medically unstable patients Medically unstable patients Previous resection Previous resection

ContraindicationsContraindications Tumors > 3 cmTumors > 3 cm Prior radiotherapyPrior radiotherapy Tumor compressing brainstemTumor compressing brainstem

Stereotactic RadiosurgeryStereotactic Radiosurgery

OutcomeOutcome Local control (non-progression): 94%Local control (non-progression): 94% Hearing preservation: 47 – 77%Hearing preservation: 47 – 77%

ComplicationsComplications Facial nerve injury: 5 - 17%Facial nerve injury: 5 - 17% Trigeminal nereve injury: 2 - 11%Trigeminal nereve injury: 2 - 11% Hyrodcephalus: 3%Hyrodcephalus: 3%