Cerebellopontine Angle Tumors: Diagnosis and ManagementAndrew Coughlin, MDTomoko Makishima, MDUniversity of Texas Medical BranchDepartment of OtolaryngologyGrand Rounds Presentation September 30, 2010

OutlineHistory of CPA tumorsDiscuss Relevant AnatomyEpidemiology and Tumor BiologySigns/Symptoms of CPA tumorsBrief overview of other CPA tumorsTreatment optionsPresent a case presentation

Overview of CPA TumorsRepresent 10% of all intracranial tumorsVestibular Schwannomas/Acoustic Neuroma represent 78% of these tumors (1)DifferentialMeningiomasEpidermoidsOther Cranial Nerve SchwannomasDermoid Tumors ( Chordomas, Teratomas)Arachnoid CystsLipomasMetastatic TumorsVascular Tumors (Hemangioma/Glomus Tumor)

History of CPA TumorsSir Charles Balance (2,3)1894 First successful removal of Vestibular Schwannoma1907 Patient still alive but had CN VII paresisHarvey Cushing1917 Monograph described CPA syndrome Pioneered subtotal resection through bilateral suboccipital craniectomy

History ContinuedWalter Dandy (5)Advocated debulking with capsule removal and decreased operative mortality to 10%William House (6-8)Advocated Translabyrinthine approach 1960’sIntroduced the microscope and dental drill to identify the facial nerveIntroduced middle cranial fossa approach

CPA Syndrome (4)Ipsilateral Hearing LossFacial HypesthesiaHydrocephalusRespiratory Failure and Death

Anatomy

EpidemiologyAutopsy series have shown incidence of 1.7 to 2.7% (9,10)MRI of 10,000 patients seen for non-otologic reasons showed 7 positive cases or 0.07% (11)Denmark reports of 1.3 per 100,000 population (12)

Acoustic Neuroma MisnomerThey are not NeuromasThey rarely are found on the acoustic portion of the nerve*Involvement of the acoustic portion of the nerve often leads to erosion of the cochlea.

Tumor BiologyArise from Schwann cells within the IAC (1)Equal frequency between inferior and superior divisions of the vestibular nerve. Arise from Scarpa Ganglion instead of Obersteiner-Redlich zone. Scarpa’s ganglion has highest density of schwann cells

GeneticsNF 2 Gene found at 22q12Tumor suppressor gene preventing schwann cell proliferationSporadic Variety (95%) (13)Hypothesized that there are two hits to the normal NF geneNeurofibromatosis type IIAutosomal DominantInherit one abnormal and one normal gene with one hit to the normal allele. Blood tests available to screen family members.

Biochemical EffectsNeuregulinExpressed by schwann cells to control proliferation and survival of schwann cellsChemokinesFGF, TGF-β, VEGF, PDGF (14-17)Sex Hormones (18)Previous studies showed increased growth in pregnancyRecent studies have not shown growth modulation or receptors for sex hormones

WorkupHistory and Physical ExamAudiologic testingVestibular TestingImaging

SymptomsIntracanalicular tumorsHearing LossTinnitusVestibular dysfunction/VertigoCPA extensionDisequilibrium/AtaxiaBrainstem ExtensionMidface HypesthesiaHydrocephalus (vision loss and headache)Other Cranial Neuropathies*SNHL>tinnitus>disequilibrium>facial hypesthesia (13)

Unilateral Hearing LossPresent in >85% of patients (19)5% of patients with VS have no associated hearing loss (20)Speech discrimination out of proportion to HLMany notice difficulty on the telephone

Association with SSNHLOccurs in up to 20% of patients (13)1% of patients with SSNHL have a vestibular schwannoma (21)48% of patients with SSNHL will have some recovery of hearing (21)Don’t rule out VS if they recover

Tinnitus2nd most common presenting signOften precedes hearing lossCan be present without hearing lossCan be high pitch, hissing, or a roarCan localize to the opposite earUnilateral tinnitus should be evaluated

Vestibular Complaints36-50% of patients describe disequilibrium (1)Vague, transient lightheadednessAcute vertigo is presenting symptom in 27% of patients but is associated with smaller tumors.

Facial HypesthesiaPresenting symptom in 4% of patientsLarger tumors >2cmMaxillary division 1stCorneal reflex is the first to goFacial weakness is rare If present should assume a different type of tumor.

Ocular ComplaintsRareLoss of corneal reflexNystagmus (toward affected side)DiplopiaInvolvement of CN VIBlurry visionPapilledema and optic atrophy from compression

SignsHitselberger SignDecreased sensation of EACSensory VII more sensitive than Motor VIIAbsent corneal reflex, nystagmusHypesthesia to pinprick and touchWeakness of Temporalis/Masseter musclesOther cranial neuropathy’sGait disturbances or difficulty with finger to nose testing

Audiologic TestingDownsloping high frequency SNHL 65% (22)5% of patients show no hearing loss (23)Rollover: Speech discrimination worse than expected and worse with increased sound intensitiesRetrocochlear losses more common than cochlear

Hearing Classification Scales (24)

Acoustic Reflexes**Positive test has 85% sensitivity for identifying retrocochlear problemAcoustic Reflex ThresholdIncreased (compared with cochlear norms) or absent if retrocochlear process

Auditory Brainstem Evoked ResponseSensitivity of 85 to 90% (25)False Positive rate 10%False Negative rate 18-30% for intracanalicular tumors Number larger than in the pastFive waveforms are produced with the most common being a latency in wave V compared to the normal ear of >0.2msec.Recommended as a screening test for those with low suspicion of vestibular schwannoma.

Vestibular Testing70-90% of patients will show some abnormality (26)50% of small tumors produce no abnormalities (27)Caloric testing is commonly the only abnormality Inferior vestibular nerve tumors may be missedSuperior nerve showed decrease in 98%Inferior nerve shows decrease in only 60% (28)Therefore not used as a screening test

CT Imaging90% of vestibular schwannomas will enhance with contrastFrequently misses tumors that are not intracanalicular and do not extend >5mm to the CPA.63% accuracy at diagnosis (29)

MRIGold Standard for Vestibular SchwannomasCan identify tumors as small as 3mm (30)Gadolinium is preferentially taken up by tumorBetter visualization of small tumorsGadolinium enhanced studiesHyperintense on T1 and T2 studiesNon-contrasted studiesHypointense T1, Isointense on T2Some recommend T2 fast spin-echo MRI as screening test but most will likely require at thin slice MRI if abnormalities are found (31)

MRI continuedVestibular SchwannomaMeningiomaCentered on IACGlobular appearanceIce cream cone appearance in IACBony erosion of IACCystic degeneration or hemorrhage may be present Extend along petrous ridgeSessile appearance“Dural Tail” at peripheryIso/Hypointense on T1Hypo to Hyperintense on T2

Acoustic vs Meningioma

Differential Diagnosis

Meningiomas3% of all CPA tumors (13)Do not metastasize but do recur due to bony invasionAre formed from cap cells around arachnoid villi near dural sinus’ and where CN’s enter their foraminaGenerally are not intracanalicular so must be larger to cause hearing concerns

MeningiomaSigns and Symptoms (32)Usually cause spontaneous nystagmus, facial hypesthesia, and gait ataxiaIf inferior can cause hoarseness, dysphagia, tongue atrophyIf within the IAC can produce similar symptoms as Vestibular SchwannomaHearing tests will show retrocochlear process if large enough, and 25% will have normal ABR’s (33)

MeningiomaTreatmentSurgical ExcisionMust remove rim of normal dura and possibly bonePoor hearing Translabyrinthine approachGood hearing Suboccipital or Middle Fossa ApproachMiddle Fossa is better for more superiorly based tumors.

Epidermoids Identical to cholesteatomaDevelop from epithelial rest cellsSlow growingCommonly don’t present until 20-30’sArise adjacent to brainstem and infiltrate areas of least resistanceCan have irregular shape and infiltrate widely

Epidermoids Signs/SymptomsFacial twitching is commonly describedCan become quite large before causing symptomsProgressive facial paralysis more common than schwannomasAudio/ABR/Speech discrimination consistent with other retrocochlear lossesTreatment is surgical excision

MRI Epidermoid (13)T2T1 post GadoliniumT1 FlairT1 post Gadolinium

MRI Arachnoid Cyst (13)T2T1T1T1

Facial SchwannomaHistologically identical to Vestibular SchwannomasCharacteristicsRarely restricted to IACCommonly have skip lesionsGenerally involve part of geniculate ganglion

Facial SchwannomaSigns/SymptomsUnilateral hearing lossTinnitusVertigoAural fullness (if distal to geniculate)Facial weakness is rare unless very largeHearing tests show retrocochlear process but impedance testing can show ipsilateral absent acoustic reflex

Facial SchwannomaTreatment is observationIf growth or facial nerve dysfunctionResection of nerve with cable graftingTranslabyrinthine approach most commonly usedFacial nerve decompression can be used if paresis is developing

Other CPA Tumors (1)Glomus TumorsJugular Foramen Syndrome (IX,X,XI), Surgical excisionHemangiomasCentered on geniculate, slow progressive facial weakness, surgical excision with facial nerve graftingArachnoid CystsTreatment is drainageCholesterol GranulomasBright on T1 and T2, Drained via infralabyrinthine approachEmbryonic tumors (Dermoids, teratomas, chordomas)Excision with dysfunctionPrimary Axial Tumors of CNS (glioma, hemangioblastoma, medulloblastoma)Surgical excision +/- radiation therapy

ManagementObservationSurgeryStereotactic RadiosurgeryRadiation Therapy**Generally tumors <3cm can be treated with stereotactic radiosurgery but microsurgery is the treatment of choice

ObservationGrowth rates vary from 0 to 2cm per year with an average of 2mm (34)38.9-82% have some growth at ≥38 months (24)14 to 24% of patients watched will go on to have some treatment (12)Age should not be determining factorYoung patient with small tumorOlder patient with large tumorOlder patient with small tumorSingle MRI is not adequateRepeat at 6 months and then again yearlyLongstanding hearing loss may represent a slow growing tumor (35)

Radiation Therapy

Stereotactic RadiosurgeryFirst Introduced Leskell in 1969Gamma KnifeUses 201 ionizing beams of gamma rays from cobalt 60 sourceOne sessionLINACUses multiple beams from a linear acceleratorOne sessionFractionated RadiotherapyNewer therapy to eradicate cells in different cell cycle stagesMultiple sessionsGoal is to stop tumor growth, not shrink or remove tumor

Stereotactic Radiosurgery (24)Local control = not requiring salvage therapy87 to 100% local control rates all three combined23% of cases have transient increase tumor volume due to central necrosis6mo to 5yr to disappear Therefore some patients receive unnecessary salvage therapy

Gamma KnifeHasegawa et al. 2005 (36)317 patientsMedian follow up 7.8 years10 yr local control >92%Partial or complete radiographic response 62%Progression free survival96% if <15cm3 vs 57% if >15cm3 p<0.001Better with no brainstem compression/4th ventricle obstruction p<0.001Most tumor progression within 3 years

LINACFreidman et al. 2006 (37)390 patientsMedian follow up 40 monthsMedian dose of 12.5 Gy5- and 10-year local control 90%Only 1% of patients required surgery for treatment failure

FSRT (24)Many different regimens studiedDose 15-57.6 Gy/3-32fxMedian Follow ups of 48 months5- year local control of >90%**Relatively new idea so no long term outcomes available

Radiosurgery vs FSRT (38)Tumor Control73.8 to 100% for Radiosurgery91.4 to 100% for FSRTTumor Shrinkage38 to 76.2% for Radiosurgery with single dose34 to 76% for FSRTTumor Growth0-26.2% for Radiosurgery0-12.5% for FSRTHearing Preservation47-71% for Radiosurgery57-100%for FSRT

Hearing PreservationDefined as G-R class I/IIEarly studies 16Gy = 46% Later Studies 12-13Gy = 68-78% with no change in control (24)Prasad et al. (39)153 patientsMedian follow up of 4.2 yearsUseful hearing preservation rate of 58% Size matters<1cm3 = 75% hearing preservation>1cm3 = 57% hearing preservation

Hearing PreservationGK vs FSRTAndrews et al. 2001 (40)109 patients63 GK at 12Gy 46 FSRT at 50Gy/25fxFollow up was 3 years33% vs 81% hearing preservation (GK/FSRT)98% vs 97% local control (GK/FSRT)Thought is that lower dose in multiple fractions leads to decreased late normal tissue damage

Facial NeuropathyGK dose decrease from 16Gy to 12-13Gy decreased rates from 15% to 0% (41)LINAC dose decrease of 16Gy to 12.5Gy showed drop in neuropathy from 4.4% to 0.7% (37)RS vs FSRT ranges of 0-52% vs 0-4%(38)

Trigeminal NeuropathyGK dose decrease from 16Gy to 12-13Gy decreased rates from 16% to 4.4% (41)LINAC dose decrease of 16Gy to 12.5Gy showed drop in neuropathy from 3.7% to 0.7% (37)RS vs FSRT ranges of 2.4-29% vs 0-16% (38)

Other complicationsHydrocepahlus0-11% (24), with highest rates in FSRTTinnitus0.2 to 5%Ataxia1.4 to 3.6%Vertigo1.4 to 1.7%Peritumoral cyst formation3.6%Malignant transformation0 to 0.3%3 cases in all studies reviewed with time to presentation of 5, 7.5, and 18 yrs post therapyDisequilibrium33% likely due to weaker central compensation (42)

SurgeryTranslabyrinthine ApproachMiddle Cranial Fossa ApproachRetrosigmoid-Suboccipital Approach**All will require discussion/collaboration with Neurosurgery

Translabyrinthine Approach (43)AdvantagesDisadvantagesLeast cerebellar retractionWide exposure of posterior fossaNo size limit for resectionFacial nerve easily identified throughout Ease of facial nerve repair if damaged/resected during removalLow recurrenceLow headachesResidual hearing is sacrificedRequires abdominal fat graft

Middle Cranial Fossa Approach (43)AdvantagesDisadvantagesBest hearing preservation<30db PTA>70% speech discriminationGood exposure of lateral IAC, CPA, and clivusDrilling is extradural decreasing morbidityLimited to tumors <2cm in greatest dimensionTemporal lobe retractionMust dissect around facial nerve due to its superior positionLimited posterior fossa exposure

Retrosigmoid/Suboccipital Approach (43)AdvantagesDisadvantagesCan attack any size tumorHearing preservation possibleWide exposure of brainstem and lower cranial nervesNeurosurgeon familiarityConsistent facial nerve identificationMust be medially located with <2cm CPA extensionLateral tumors risk injury to endolymphatic sac and vestibular labyrinthCerebellar retraction occulomotor abnormalities and postop disequilibriumIncreased air embolism risk (Sitting vs Park Bench position)

Microsurgery Control RatesTranslabyrinthineTotal Resection 99.5 to 99.7% (44-45)Near total resection (<25mm2 or 2mm thick)Visible on MRI in 50% of patients with 3% risk of recurrence (46-47)Middle Cranial FossaTotal Resection 98% (48)Retrosigmoid Total resection 95% (49)

Hearing PreservationServiceable hearing defined as class A/B or 1/2 (24)Middle cranial fossa 51% Retrosigmoid 31% Meyer et al. 2006 (50)162 consecutive patients via MCF approachClass A/B hearing preserved in 41%56/113 (50%) with WR >70% preoperatively maintained that level.Tumor 0.2-1.0cm = 59%Tumor 1.1-1.4cm = 39%Tumor 1.5-2.5cm = 33%

Facial Nerve ParalysisReporting function at 6-12 month point is gold standardPreserved = Grade I/II (24)Retrosigmoid 91% Middle Cranial Fossa 88% Translabyrinthine 77%Delayed paralysis (>72hrs after surgery)Described by Grant et al. 2002Incidence 5% (51)79% regain postoperative function by 1 yr

CSF LeakPooled data from 19 studies 360/4297 (8%) rate (52)MCF approach 6%TL approach 8%RS approach 11%Occurs at two different time pointsPOD 2-3 (Early)POD 10-14 (Late)

HeadacheOccurs roughly 10% of patients >3 months postop (52)RS approach 21%MCF approach 8%TL approach 3%MechanismsBone dust contacting CSF/Meninges  Aseptic MeningitisOccipital nerve entrapmentScarred neck muscles and duraMigraine

Other Microsurgical Complications (53)Mortality1% due to neurovascular injuryMeningitis 1-8% Aseptic more common than bacterial (bone dust/inflammation)S. aureus most common pathogenTinnitus50% with preop tinnitus will have resolution postopBalance abnormalitiesOccurs in most patients but gone by 6-9 monthsSeizure/Hydrocephalus/Stroke (24)Rare and <2% of cases

Microsurgery vs RadiosurgeryMyrseth et al 2005 (53)Retrospective review 189 patients tumors ≤3cm86 by microsurgery vs. 103 by GK5.9 year mean follow upLocal control rates of 89.2% Surgery vs 94.2% GK HB 1-2 in 79.8% Surgery vs 94.8% GK p=0.0026 Quality of life significantly lower in surgery group compared to gamma knife group*MCF approach was not utilized

Microsurgery vs RadiosurgeryPollock et al. 2006 (54)Prospective cohort of 82 patients unilateral VS <3cm36 Surgery vs 46 GKAverage follow up of 42 monthsLocal control 96% Surgery vs 100% GK p= 0.50HB 1/2 in 75% Surgery vs 96% GK p<0.01Hearing Preserved 5% Surgery vs 63% GK p<0.001Quality of life all statistically better for GKPhysical functioningBodily pain scoresDizziness Handicap Inventory

SummaryVestibular schwannomas are the most common CPA tumorUnilateral Tinnitus or SNHL must be evaluatedTumors <3cm in size treated with radiosurgeryGK or LINAC have comparable resultsFSRT may prove more beneficial but requires more than 1 day of treatmentFor patients with no serviceable preoperative hearing, translabyrinthine approach is best choiceFor Hearing Preservation options the middle cranial fossa approach appears to be slightly better than the retrosigmoid approach due to decreased rates of complications.

Case Report55 y/o female with 2 year history of falls and disequilibriumFalls are now progressive and dailyDenies true vertigo just imbalancedAlso has tinnitus, neck spasms, and migrainesShe denies any hearing loss but family feels otherwise

Case ReportPMHx: HTN, HypothyroidismPSHx: Partial hysterectomy and R thyroid lobectomyFHx: NoncontributorySHx: 45pack year history of smoking, -EtOHMedications: HCTZ, metoprolol, sydol prn, soma, and ambien prn Allergies: SulfaROS: Otherwise negative. No vision or constitutional problems

Case ReportGeneral: NAD oriented x3Head: NCATEyes: No nystagmus, PERRLA, EOMIENT: TM’s intact, Tuning forks normalNeck: No masses or lymphadenopathyNeuro: CN II-XII intact, unsteady Romberg, tandem gait falling to the left, and left finger to nose ataxia

Case ReportAudiogramNormal hearing with mild high frequency SNHL at 4000Hz bilaterallyENG Decreased accuracy on horizontal smooth pursuit54% weakness on left air caloric testingMRI1.5 to 2cm lesion closely associated with CN VII/VIII. It is intracanalicular with extension into CPA. No evidence of brainstem compression or ventricular obstruction

Image 1

Image 2

Image 3/4

Treatment Plan?Finger to nose and gait ataxiaEssentially normal hearingENG positive for left lateral canal weakness2cm tumor, no hydrocephalus

Case ReportPatient had previous MRI 2005 showing no tumorTherefore it is decided that we perform suboccipital craniotomy for excision of tumor

Images of SurgeryTumorRetracted CerebellumTentorium Cerebelli

Images of SurgeryTentorium CerebelliTumorRetracted CerebellumCN VII/VIII Complex

Images of SurgeryCN V

Images of Surgery

Case ReportFinal Pathology: MeningiomaNo complications at this pointTuning forks 256hz and 512hz normalHB I immediately and 72 hours postoperatively

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