Vestibular Schwannomas: History, Diagnosis, and Management. Kiley Trott PGY 4 Advisors: Dr. Willcox and Dr. Pelosi

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1 Vestibular Schwannomas: History, Diagnosis, and Management Kiley Trott PGY 4 Advisors: Dr. Willcox and Dr. Pelosi

2 OUTLINE History of Vestibular Schwannomas Relevant Anatomy Review Epidemiology and Tumor Biology Signs and Symptoms Diagnostic Approaches Differential of Cerebellopontine Angle Masses Management Options and Considerations

3 Acoustic Neuroma or Vestibular Schwannoma They are not technically neuromas Arise from the vestibular components of the nerve

4 Overview of Cerebellopontine Angle Masses 10% of intracranial tumors are found in the Cerebellopontine Angle (CPA) Roughly 80% are Vestibular Schwannomas (VS) Differential of CPA masses Meningiomas Epidermoids Schwanommas of other nerves Dermoid Tumors Arachnoid Cysts Lipomas Metastatic Tumors Vascular Tumors

5 Historical Perspective Acoustic Neuromas were first described in the late 1700s Sandifort 1777 during an autopsy in a deaf patient documented a small body adherent to the right auditory nerve In the mid 1800s an understanding that unilateral deafness, facial numbness, and progressive blindness from optic neuritis (papilledema) likely due to a CPA mass

6 Historical Perspective Sir Charles Ballance 1894 first removal of VS, but patient died from complications 1907 first successful excision without patient mortality Overall high surgical mortality Horsley, von Eiselsberg, and Krause Largely performed unilateral suboccipital craniotomy with removal by finger dissection 1913 Presented data on 63 patients, 78% mortality Harvey Cushing Developed bilateral suboccipital craniectomy for subtotal resection Described CPA syndrome Reduced mortality to 4% Critical of translabyrinthine approach

7 If the otologist has ambitions to treat these lesions there is no possible route more dangerous or difficult Cushing 1917

8 Historical Perspective Walter Dandy 1916 Advocated for unilateral occipital flap with total tumor removal Decreased mortality to 10%, lower recurrence rate William House 1960s Resurrected translabyrinthine approach Pioneered use of operating microscope and surgical drill Also introduced middle cranial fossa approach

Relevant Anatomy Cerebellopontine Angle Located in Posterior Fossa Contains origin of many cranial nerves Medial Border: brainstem Lateral Border: petrous portion of

9 Relevant Anatomy Cerebellopontine Angle Located in Posterior Fossa Contains origin of many cranial nerves Medial Border: brainstem Lateral Border: petrous portion of temporal bone Superior Border: middle cerebellar peduncle Inferior Border: arachnoid of lower cranial nerves Anterior Border: Clivus Posterior Border: cerebellar tonsil

10 Epidemiology 80-90% of all CPA masses Incidence of 10 cases per million every year 2005 study suggested prevalence of incidental VS to be 2 in 10,000 people Autopsy studies have detected higher rates indicating VS may not become clinically apparent 95% sporadic, 5% associated with neurofibromatosis type 2 Presents in Adulthood: mean age 50 (31 for NF2)

11 Tumor Biology Arise from vestibular division of 8 th cranial nerve Likely equal distribution between superior and inferior divisions Historically thought to originate from Obersteiner-Redlich zone Transitional area from central to peripheral myelin Now hypothesized to originate from Scarpa s ganglion Highest concentration of schwann cells

12 Genetics Neurofibromatosis type 2 Autosomal Dominant NF 2 gene at 22q12.2: tumor suppressor gene normally prevents cell proliferation Codes merlin protein Sporadic cases Double Hit hypothesis: 2 hits to normal genes

13 Histology Antoni A Antoni B

Natural History Intracanalicular Phase Hearing loss tinnitus, vertigo Cisternal Phase Hearing loss, disequilibrium Compressive Phase Trigeminal

14 Natural History Intracanalicular Phase Hearing loss tinnitus, vertigo Cisternal Phase Hearing loss, disequilibrium Compressive Phase Trigeminal symptoms, Headaches Hydrocephalic Phase 4 th ventricle obstruction Clinical deterioration Facial weakness, vision loss Respiratory Failure and death

15 Symptoms Common Findings Unilateral/asymmetric hearing loss Up to 95% Tinnitus Up to 70% Disequilibrium Up to 50% Greater than 70% with tumors >3cm Facial Anesthesia Found in 50% in those with tumors >2cm Typically midface hypoesthesia Less Frequent Findings Vertigo Roughly 20% predominantly with smaller tumors Headache Mid sized 1-3cm tumors: 20% Tumors >3cm: approaching 40% Facial Spasm 10% typically orbicularis oculi Ophthalmic Manifestations Nystagmus and Papilledema Lower Cranial Neuropathies <3.5%

16 Signs Hitselberger s Sign Sensory component of CN 7 Nystagmus Trigeminal dysfunction Absent Corneal Reflex Temporal Wasting and Masseter Weakness Found rarely in advanced disease Cerebellar Signs Gait ataxia Poor finger to nose testing

17 Workup Audiologic Testing Pure Tone and Speech Audiometry Auditory Brainstem Responses Vestibular Testing Imaging

18 Hearing Loss Most common symptom Unilateral/Asymmetric 20% atypical pattern 5% present without hearing loss High frequencies typically affected Speech discrimination out of proportion to pure tone SSNHL Occurs in 20% of patients 1% of those with SSNHL will have a VS Audiometry

19 Hearing Loss Classification Systems Used in research to compare pre- and post-operative hearing Can aid in determining surgical approach AAO-HNS: Grade A and B considered serviceable hearing Gardner-Robertson: Grade 1 and 2 considered serviceable hearing Scheme SDS PTA WRS I II III 1-49 IV 0 AAO-HNS A B C > D < Gardner-Robertson I II III IV V 0

20 Hearing Loss Acoustic Reflex Decay Thresholds increased or absent if retrocochlear Acoustic Reflexes

21 Hearing Loss Most common finding (40-60%) increased wave V latency Most specific finding only wave I present Pattern present in only 10-20% of cases Normal ABR in 10-15% of cases 33% of intracanalicular tumors High false positive rate >80% Auditory Brainstem Responses

22 Vestibular Testing Electronystagmography Not very sensitive or specific for VS 70-90% will show an abnormality 50% of small tumors produce no abnormality

23 Imaging CT Non-contrast: Poor Sensitivity Contrasted: Ok for intracanalicular tumors 90% of tumors enhance Can miss tumors <2cm MRI Gold standard

Pre- and post-contrast T1 images Fast spin echo T2 images T1: mildly

24 Imaging MRI Findings Most Sensitive and Specific False negatives are rare Viral neuritis can produce false positives Sequences to obtain Pre- and post-contrast T1 images Fast spin echo T2 images T1: mildly hypointense to brain, hyperintense to CSF T1 Gd: contrast enhancement

25 Imaging MRI Findings Most Sensitive and Specific False negatives are rare Viral neuritis can produce false positives Sequences to obtain Pre- and post-contrast T1 images Fast spin echo T2 images T2: Fast Spine Echo

26 Imaging MRI Triggers When to get an MRI? 15dB or greater asymmetry in 2 or more frequencies Discrimination asymmetry of 16% or greater Unilateral tinnitus Asymmetric SNHL + trigeminal symptoms Asymmetric SNHL + disequilibrium Goal of detection Small tumors have great surgical outcomes 98% cure, 99% intact facial nerve function, 80% preserved hearing Cost Analysis of ABR vs MRI: Study reviewed >300 cases of ASNHL ABR screening: $125,000, with 29% of tumors unidentified MRI screening: $156,000, with 0% lesions missed (at a cost of $99 more per case)

27 Imaging Reflexive MRI vs Serial Audiograms VS is not the only cause of asymmetric SNHL Tumor growth is generally slow Cost analysis of serial audiograms comparing MRI early vs after progression Early MRI: $210,000 After audiogram progression: $186,000 May risk: Delayed diagnosis Irreversible hearing loss Inability to perform hearing preservative procedure Decision to obtain MRI should be based on global clinical picture

28 Imaging Meningioma Dural tail Extend along petrous ridge Iso/hypointense on T1 Hypo to hyperintense on T2 Sessile appearance Vestibular Schwannoma Ice cream cone appearance in IAC Bony erosion in IAC Globular appearance Can have cystic degeneration.

29 Imaging Meningioma Vestibular Schwannoma

30 Differential Diagnosis Epidermoids: similar to cholesteatomas, from epithelial rest cells Hypointense T1 and bright on T2 Arachnoid Cysts Treat with drainage Schwanommas of other nerves Cholesterol Granulomas bright on T1 and T2 Embryonic Tumors excise when they cause dysfunction Hemangiomas can form near geniculate producing progressive facial weakness Glomus Tumors Jugular Foramen Syndrome

31 Management Options Observation with Serial Imaging Stereotactic Radiation Microsurgery

32 Management Set Expectations Observation 14-24% of patients being observed will go on to some form of treatment Average growth 2mm/year, but can range from 0 to 2cm annually Factors favoring observation Minimal symptoms Long standing stable history, may indicate slow growth rate Comorbid conditions and general health Refusing other treatment Protocol Follow up scan in 6 months, then serial imaging yearly

33 Management Introduced by Leskell in 1969 Damages vascular endothelium Stereotactic Radiosurgery Goal is to arrest tumor growth Gamma Knife uses multiple beams of ionizing radiation LINAC uses a linear accelerator as its source of radiation Benefits Non-invasive Early return to function Avoids surgery Fractionated Radiotherapy Multiple sessions

34 Management Stereotactic Radiosurgery Outcomes Transient increase in tumor size due to central necrosis in roughly 20% Gamma Knife study by Boari et al Tumor control in 97.1% Tumor volume reduction in 82.7%, mean relative volume reduction 34.1% May require salvage surgery Increased trigeminal neuropathy Does not address disequilibrium

35 Management Surgery Translabyrinthine Approach Middle Cranial Fossa Approach Retrosigmoid-Suboccipital Approach

36 Management: Translabyrinthine Advantages Least cerebellar retraction Wide exposure of posterior fossa No size limitations for resection Easy identification of facial nerve Low recurrence rates Less headaches Disadvantages Sacrifices residual hearing Fat graft donor site morbidity

37 Management Translabyrinthine Postauricular incision

38 Management Translabyrinthine Postauricular incision Mastoidectomy Dural Exposure

39 Management Translabyrinthine Postauricular incision Mastoidectomy Dural Exposure Facial Nerve Identification Labyrinthectomy IAC Exposure

40 Management Translabyrinthine Postauricular incision Mastoidectomy Dural Exposure Facial Nerve Identification Labyrinthectomy IAC Exposure Dura Incised Identify CN VIII components

41 Management Translabyrinthine Postauricular incision Mastoidectomy Dural Exposure Facial Nerve Identification Labyrinthectomy IAC Exposure Dura Incised Identify CN VIII components Tumor Debulking Tumor Dissected from Facial Nerve Fat graft, dural repair, and closure

42 Management: Middle Cranial Fossa Advantages Best hearing preservation Adequate exposure of lateral IAC, CPA, and clivus Extradural drilling Disadvantages Limited to smaller tumors <2cm Temporal lobe retraction Limited posterior fossa exposure Facial nerve dissection

43 Management Middle Cranial Fossa Temporal skin incision Temporal craniotomy

44 Management Middle Cranial Fossa Temporal skin incision Temporal craniotomy Temporal lobe retraction Dural elevation Geniculate identified and exposed Labyrinthine portion followed to IAC IAC exposed Tumor debulking and dissection IAC packed Craniotomy repaired Wound closure

45 Management: Retrosigmoid Advantages Wide exposure of brainstem and lower cranial nerves Can preserve hearing Can resect large tumors Posterior approach to facial nerve Disadvantages Cerebellar retraction Tumor must have <2cm IAC extension

46 Management Retrosigmoid Post auricular Incision Suboccipital craniotomy Tumor debulking and dissection Dural and craniotomy closure

47 Management Considerations Factors Serviceable Hearing Tumor Size Tumor Position Anatomic Considerations Surgeon Preference Patient Preference Debulking vs Total Resection

48 Complications Vascular Injury Facial Nerve Paralysis CSF Leak Headache Meningitis Tinnitus Balance Dysfunction Seizure, Hydrocephalus, and Stroke Mortality

49 Complications Vascular Injury Arterial: AICA, labyrinthine artery, branches to facial nerve Venous: sigmoid sinus, petrosal vein of Dandy, vein of Labbé Can produce cerebral edema Posterior Fossa Hemorrhage Brainstem compression Rapid neurologic deterioration Potentially fatal

50 Complications Preservation Rates (HB 1-2) Retrosigmoid: 91% Middle Cranial Fossa: 88% Translabyrinthine: 77% Delayed Onset (>72hrs post op) Occurs in 5% of cases 79% regain function after 1 year Facial Nerve Injury

51 Complications CSF Leak Can occur early (POD 2-3) or late (POD 10-14) Highest in retrosig approach: 11% Translab has 8% rate Middle cranial fossa has 6% Treatment Conservative: bed rest, stool softeners, diuresis May require lumbar drain, shunting, or operative repair

52 Complications Headache Post op headache of >3 months duration occurs in roughly 10% of all cases Retrosig: 21% Middle Cranial Fossa: 8% Translab: 3% Possible etiology Bone dust contamination producing aseptic meningitis Cranioplasty Dural scarring Migraines

53 Complications Bacterial Meningitis Staph aureus most common organism Standard presentation and treatment Balance Issues Other Complications Transient typically resolves in 6-9 months Tinnitus 50% of patients with preop tinnitus have cessation of symptoms Seizure/Hydrocephalus/Stroke: rare <2% of cases Mortality: roughly 1%

54 Outcomes Recurrence Rates Overall < 5% Most occur after retrosig approach Suspect with headaches, facial numbness, lower cranial neuropathies Hearing Results Hearing preservation ranges from 30-80% depending on approach and patient selection Better pre op hearing predicts better post op hearing Larger tumors associated with lower rates of serviceable hearing Gamma Knife and surgical treatment have similar hearing preservation rates

55 Conclusion Vestibular Schwannomas are the most common CPA tumor Unilateral SNHL or tinnitus requires further evaluation MRI is the confirmatory study of choice Some patients with few symptoms and small tumors can be observed Radiosurgery is appropriate for tumors <3cm in size In the setting of unserviceable hearing translab approach is best For hearing preservation use middle cranial fossa or retrosigmoid approach

56 Questions?

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Antonio De la Cruz, MD 27th Alexandria International Combined ORL Congress Alexandria, Egypt April 8, 2009

Antonio De la Cruz, MD 27th Alexandria International Combined ORL Congress Alexandria, Egypt April 8, 2009 ACOUSTIC NEUROMA TREATMENT OPTIONS 2009 27 th Alexandria International Combined ORL Congress Alexandria, Egypt April 10, 2009 AntonioDelaCruz Cruz, MD House Ear Institute Los Angeles, California Antonio