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

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

Acoustic Neuroma or Vestibular Schwannoma

• They are not technically neuromas

• Arise from the vestibular components of the nerve

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

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

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• 1917-1931 Developed bilateral suboccipital craniectomy for subtotal resection• Described CPA syndrome• Reduced mortality to 4%• Critical of translabyrinthine approach

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

Cushing 1917

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 temporal bone• Superior Border: middle cerebellar peduncle• Inferior Border: arachnoid of lower cranial nerves• Anterior Border: Clivus• Posterior Border: cerebellar tonsil

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)

Tumor Biology

• Arise from vestibular division of 8th 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

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

Antoni A Antoni B

Histology

Natural History

• Intracanalicular Phase• Hearing loss tinnitus, vertigo

• Cisternal Phase• Hearing loss, disequilibrium

• Compressive Phase• Trigeminal symptoms, Headaches

• Hydrocephalic Phase• 4th ventricle obstruction• Clinical deterioration• Facial weakness, vision loss• Respiratory Failure and death

Common Findings Less Frequent 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

• 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%

Symptoms

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

Workup

• Audiologic Testing• Pure Tone and Speech Audiometry• Auditory Brainstem Responses

• Vestibular Testing• Imaging

Audiometry

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

Classification Systems

Hearing Loss Scheme SDS PTA

WRS

I 70-100

II 50-69

III 1-49

IV 0

AAO-HNS

A 70-100 0-30

B 50-69 31-50

C >50 50+

D <50 50+

Gardner-Robertson

I 70-100 0-30

II 50-69 31-50

III 5-49 51-90

IV 1-4 91+

V 0

• 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

Acoustic Reflexes

Hearing Loss

• Acoustic Reflex Decay• Thresholds increased or absent if

retrocochlear

Auditory Brainstem Responses

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%

Electronystagmography

Vestibular Testing

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

Imaging

• CT• Non-contrast: Poor Sensitivity• Contrasted: Ok for intracanalicular

tumors• 90% of tumors enhance• Can miss tumors <2cm

• MRI• Gold standard

MRI Findings

Imaging

• 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

MRI Findings

Imaging

• 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

When to get an MRI?

Imaging

• MRI Triggers• 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)

Reflexive MRI vs Serial Audiograms

Imaging

• 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

Meningioma Vestibular Schwannoma

• “Dural tail”• Extend along petrous ridge• Iso/hypointense on T1• Hypo to hyperintense on T2• Sessile appearance

• Ice cream cone appearance in IAC• Bony erosion in IAC• Globular appearance• Can have cystic degeneration.

Imaging

Meningioma Vestibular Schwannoma

Imaging

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

Management Options

• Observation with Serial Imaging• Stereotactic Radiation• Microsurgery

Observation

Management

• Set Expectations• 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

Stereotactic Radiosurgery

Management

• Introduced by Leskell in 1969• Damages vascular endothelium• 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

Stereotactic Radiosurgery Outcomes

Management

• 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

Surgery

Management

• Translabyrinthine Approach•Middle Cranial Fossa Approach• Retrosigmoid-Suboccipital Approach

Advantages Disadvantages

• Least cerebellar retraction• Wide exposure of posterior fossa• No size limitations for resection• Easy identification of facial nerve• Low recurrence rates• Less headaches

• Sacrifices residual hearing• Fat graft donor site morbidity

Management: Translabyrinthine

Translabyrinthine

Management

• Postauricular incision

Translabyrinthine

Management

• Postauricular incision• Mastoidectomy• Dural Exposure

Translabyrinthine

Management

• Postauricular incision• Mastoidectomy• Dural Exposure• Facial Nerve Identification• Labyrinthectomy• IAC Exposure

Translabyrinthine

Management

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

Translabyrinthine

Management

• 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

Advantages Disadvantages

• Best hearing preservation• Adequate exposure of lateral IAC,

CPA , and clivus• Extradural drilling

• Limited to smaller tumors <2cm• Temporal lobe retraction• Limited posterior fossa exposure• Facial nerve dissection

Management: Middle Cranial Fossa

Middle Cranial Fossa

Management

• Temporal skin incision• Temporal craniotomy

Middle Cranial Fossa

Management

• 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

Advantages Disadvantages

• Wide exposure of brainstem and lower cranial nerves

• Can preserve hearing• Can resect large tumors• Posterior approach to facial nerve

• Cerebellar retraction• Tumor must have <2cm IAC

extension

Management: Retrosigmoid

Retrosigmoid

Management

• Post auricular Incision• Suboccipital craniotomy• Tumor debulking and dissection• Dural and craniotomy closure

Management Considerations

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

Complications

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

Vascular Injury

Complications

• 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

Facial Nerve Injury

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

CSF Leak

Complications

• 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

Headache

Complications

• 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

Other Complications

Complications

• Bacterial Meningitis• Staph aureus most common organism• Standard presentation and treatment

• Balance Issues• 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%

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

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

Questions?

Citations• Acoustic neuroma treatment: Microsurgery. (2016). Retrieved from http://www.anaa.org.au/acoustic-neuroma-treatment/• Armato, E., & Ferri, E. (2008). Cerebellopontine meningioma revealed by intratumoral microhemorrhage following whiplash injury. The Internet Journal of Otorhinolaryngology, 8(2)• Arriaga, M. A., Chen, D. A., & Fukushima, T. (1997). Individualizing hearing preservation in acoustic neuroma surgery. The Laryngoscope, 107(8), 1043-1047. doi:10.1097/00005537-199708000-00007• Backous, D. D., & Pham, H. T. (2008). Guiding patients through the choices for treating vestibular schwannomas: Balancing options and ensuring informed consent. Neurosurgery Clinics of North America,19(2), 379-392.• Boari, N., Bailo, M., Gagliardi, F., Franzin, A., Gemma, M., Vecchio, A. d., . . . Mortini, P. (2014). Gamma knife radiosurgery for vestibular schwannoma: Clinical results at long-term follow-up in a series of 379 patients:

Clinical article. Journal of Neurosurgery, 121(Suppl 2), 123-142.• Campbell, K., & Mullin, G. (2016). Impedance audiometry. Medscape,• Case courtesy of A.prof frank gaillard, radiopaedia.org, rID: 2574.• Case courtesy of dr sandeep bhuta , radiopaedia.org, rID: 6839• Clinical correlations related to the auditory system. (2004). Retrieved from http://www.neuroanatomy.wisc.edu/c oursebook/audclinical04.pdf• Cueva, R. A. (2010). Clinical thresholds for when to test for retrocochlear lesions: Pro. Archives of otolaryngology–head & Neck Surgery, 136(7), 725-727.• Diaz Day, J. (2012). The middle fossa approach and extended middle fossa approach: Technique and operative nuances. Neurosurgery, 70(2 Suppl Operative), 192-201. doi:10.1227/NEU.0b013e31823583a1 [doi]• Emanuel, D. (2009). Acoustic reflex threshold (ART) patterns: An interpretation guide for students and supervisors. Retrieved from http://www.audiologyonline.c om/articles/acoustic- reflex- threshol d-art-pa tterns-875• Hain, T. (2016). Acoustic neuroma. Retrieved from http://www.dizziness-and-balance.com/di sorders/tum ors/acoustic_neuroma.htm• Harsha, W. J., & Backous, D. D. (2005). Counseling patients on surgical options for treating acoustic neuroma. Otolaryngologic Clinics of North America, 38(4), 643-652.• Jackler, R. K., Brackmann, D. E., & ScienceDirect (Online service). (1994). Neurotology Mosby.• Jayaraman, M. (2015). Imaging in cranial nerve schwannoma. Retrieved from http://emedicine.medscape.com/article/336141-overview#showall• Kang, O., & Gaillard, F.Acoustic schwannoma. Retrieved from http://radiopaedia.org/articles/acoustic-sc hwannoma• Kartush, J.Acoustic neuroma. Retrieved from http://www.michiganear.com/ea r-disorders-acoustic-neuroma.html• Kesser, B. W. (2010). Clinical thresholds for when to test for retrocochlear lesions: Con. Archives of Otolaryngology–Head & Neck Surgery, 136(7), 727-729.• Kutz, J., Roland, P., & Isaacson, B. (2016). Acoustic neuroma. Medscape, , June 1.• Machinis, T., Fountas, K., Dimopoulos, V., & Robinson, J. (2005). History of acoustic neurinoma surgery. Medscape, (Neurosurgical Focus)• Minimally invasive endoscopic and endoscopy-assisted microsurgery of vestibular schwannoma - scientific figure on ResearchGate. available from: Https://www.resea rchgate.net/221920401_fig2_Fig-2-surgical-steps-of -the-

minimally-invasive-retrosigmoid-approach-fo r-vestibula r [accessed 12 jul, 2016].• Nickele, C. M., Akture, E., Gubbels, S. P., & Baskaya, M. K. (2012). A stepwise illustration of the translabyrinthine approach to a large cystic vestibular schwannoma. Neurosurgical Focus, 33(3), E11.

doi:10.3171/2012.7.FOCUS12208 [doi]• Patel, J., Vasan, R., van Loveren, H., Downes, K., & Agazzi, S. (2014). The changing face of acoustic neuroma management in the USA: Analysis of the 1998 and 2008 patient surveys from the acoustic neuroma

association. British Journal of Neurosurgery, 28(1), 20-24. doi:10.3109/02688697.2013.815323• Patkar, D. P., Yanamandala, R., Pardhi, M., Gaikwad, S. A. P., & Pawar, S. V. (2011). MRI of lateral skull base lesions. Otorhinolaryngology Clinics: An International Journal, 3(1), 43-55.• Retrieved from https://meded.ucsd.edu/clinicalmed/eye_c orneal_reflex .jpg• Retrieved from http://img.medscape.com/fullsize/migrated/489/074/nf489074.fig1.gif• Rosenberg, S. I. (2000). Natural history of acoustic neuromas. The Laryngoscope, 110(4), 497-508. doi:10.1097/00005537-200004000-00002 [doi]• Rosenberg, S. I. (2000). Mosher award honorable mention. The Laryngoscope, 110(4), 497-508. doi:10.1097/00005537-200004000-00002• Seizinger, B. R., Martuza, R. L., & Gusella, J. F. (1986). Loss of genes on chromosome 22 in tumorigenesis of human acoustic neuroma.• Shoup, A., & Townsley, A. (2016). Electronystagmography. Medscape,• Unilateral hearing loss. (2014). Retrieved from https://www.cns.org/education/browse- type/ca se-m onth/oct2014#!prettyPhoto• Vogel, R.Overview of ABR. Retrieved from http://neurologiclabs.com/neurom onito ring/abr/• Wippold, F. J.,2nd, Lubner, M., Perrin, R. J., Lammle, M., & Perry, A. (2007). Neuropathology for the neuroradiologist: Antoni A and antoni B tissue patterns. AJNR.American Journal of Neuroradiology, 28(9), 1633-1638.

doi:ajnr.A0682 [pii]• Woodson, E. A., Dempewolf, R. D., Gubbels, S. P., Porter, A. T., Oleson, J. J., Hansen, M. R., & Gantz, B. J. (2010). Long-term hearing preservation after microsurgical excision of vestibular schwannoma.Otology &

Neurotology : Official Publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology, 31(7), 1144-1152. doi:10.1097/MAO.0b013e3181edb8b2 [doi]