NOTE! This site uses cookies and similar technologies.

If you not change browser settings, you agree to it. Learn more

I understand

In order to make our website more comfortable and intuitive, we use cookies: they are small files of information needed to understand how users navigate in our website and make your browsing experience more enjoyable and more efficient in the future. Cookies do not store any personal information, and will not be stored any identifiable data. If you want to disable the use of cookies you have to customize the settings of your internet browser by removing all existing cookies and disabling their storage. To proceed without modifying the application of the cookies just continue the surfing.

Please visit AboutCookies.org for more information about cookies and how they affect your browsing experience.

Types of cookies used:

Technical cookie 
These cookies are essential for the website navigation; without some of these, technical issues could not work.

Performance cookie
These cookies collect informations about how visitors use the website: for example, which pages are most popular, and which pages have reported warnings or error messages. These cookies do not collect any personal information about the visitor, and they are used only to improve the website operation. By using our website, you agree that these cookies may be installed on your device.

Functionality Cookie
Cookies allow the website to remember the choices made by the user (for example, to remember the language choice) and provide custom functionality. These cookies can also be used to remember changes to the text size and other features of web pages that you can customize. They can also be used to provide services such as watching a video or sharing on social networks. The information gathered from these types of cookies can be anonymous and can't track your browsing activity on other websites. By using our website, you agree that these cookies may be installed on your device.

Google Analytics
This website uses Google Analytics, a web analytics service provided by Google Inc.
The information generated by the cookie about your use of the website (including your anonymous IP address) will be transmitted and stored in Google's servers in the United States. Google will use this information with the purpose of evaluating your use of the website, compiling reports on website activity for the operators and providing other services relating to website activity and internet usage. Google may also transfer this information to third parties, unless required by law, or where such third parties process the information on Google's behalf. Google will not associate your IP address with any other data held by Google. By using this website, you allow Google to process the data about you in the manner and purposes set out above.

Facebook 
This website uses plugins from the social network facebook.com, which is operated by Facebook Inc., 1601 S. California Ave, Palo Alto, CA 94304, USA (subsequently called "Facebook"). When opening a website that contains such a plugin, your browser will establish a direct connection to the Facebook servers. Facebook will transfer the content of the plugin directly to your browser, the latter of which will embed it in the website. This website hence does not have any influence on the amount of data that Facebook collects through this plugin and informs you according to its best knowledge. Through embedding the plugins Facebook receives the information that you have opened the respective website. If you are logged in to Facebook, Facebook can link this information to your Facebook account. If you interact with the plugins, for example by clicking the Like-button or commenting, your browser will submit this information directly to Facebook, which will save it. If you are not a member of Facebook, Facebook nonetheless might identify and save your IP address. Purpose and scope of the data collection as well as its distribution and usage of the data by Facebook as well as respective rights and preferences regarding privacy can be found in Facebook's privacy policy http://www.facebook.com/policy.php. If you are a member of Facebook and do not want Facebook to collect data through this website and connect it to your Facebook profile, you have to log out from Facebook prior to visiting this site.

 Definition

The term “vestibular schwannoma” or “neurinoma” refers to an histologically benign tumor of the vestibular branch (the inferior one) of the eighth cranial nerve. It arises in the internal auditory canal, but can often extend to the cerebellopontine angle (CPA).

 

Anatomy of the eighth cranial nerve

The eighth nerve is formed by the cochlear and vestibular rami. They arise between pons and medulla from the retro-olivary sulcus, anteriorly to the floccolus and choroid plexus. They move toward laterally through the subarachnoid cisterns, entering into the internal acoustic meatus, where they split.
The cochlear nerve has a role in the auditory perception. The fibers innervate the spiral organ of the cochlea.
The vestibular nerve carries information about the state of equilibrium and it is divided in a superior and inferior branches.
The superior one receives fibers from the anterior and lateral semicircular canals and utricle, the inferior one receives fibers from the saccule.

 

Epidemiology

Vestibular schwannoma accounts for 1-2/100,000/year. Usually it becomes symptomatic after age 30. The 95% of the cases are sporadic and unilateral tumors due to a somatic mutation; the bilateral one are associated to an hereditary disorder called neurofibromatosis type II (NF2)

Neurofibromatosis

It is a neurocutaneous genetic disorder of the nervous system. The most common types are:

  • Neurofibromatosis type 1 (NF1)
  • Neurofibromatosis type 2 (NF2)

 

NF1

Also known as Von Recklinghausen’s disease. It is an autosomal dominant disease (prevalence 1-5/10,000) which causes the alteration of gene on the chromosome 17q11.2. It has a childhood onset. The main diagnostic criteria are cutaneous café-au-lait spots, multiple neurofibromas, Lisch's nodules, axillary and inguinal freckling (hyperpigmentation), osseous abnormalities, optic glioma and astrocytoma.

NF2

Also known as Central neurofibromatosis or Bilateral acoustic neurofibromatosis. It is an autosomal dominant pathology (prevalence 1-9/100,000). The gene NF2, located on chromosome 22q12, encodes for the protein Merlin (acronym for moesin-ezrin-radixin-like protein), which connects the cytoskeleton to the plasmatic membranes. The main diagnostic criteria are bilateral vestibular schwannomas with hearing loss, cutaneous schwannomas, meningiomas, cataracts and ependymomas. 

 

Etiology 

Largely unknown. Only in the cases of Type II Neurofibromatosis can be attributed a genetic cause.
The incomplete tumor resection may determine recurrences.

 

Symptoms and Signs

The symptoms are correlated to the size, the growth rate of the neurinoma and the anatomical structures which are involved. It is possible recognized a clinical triad:

  • Ipsilateral Sensorineural hearing loss (SNHL) in 85%
  • Tinnitus
  • Dysequilibrium (36%-50%)/ Vertigo (27%)

Other simptoms

  • Facial numbness and weakness
  • Diplopia
  • Nistagmus
  • Hydrocephalus
  • Change of taste
  • Neurological disorders (Babinski sign)
  • Sudden deafness 


Microscopical description

This encapsulated tumour arises from the glia (Schwann cells) of the peripheral nervous system. It wraps the axons, forming the myelin sheath.
The lesion is usually a solid mass, but it can present areas of cystic alterations and xanthomatosis; the histological examination shows two different patterns: Antoni A and Antoni B.

Antoni type A

It presents hypercellular areas, characterized by elongated cells with rod-shaped nuclei, and a decreased stromal matrix. The fascicular arragement of the fusiform and eosinophil cells is known as Verocay body.

Antoni type B

It presents hypocellular areas with polymorphic and stellate cells, characterized by smaller oval nuclei. The stromal matrix is microcystic and mixoid. The typical palisade arrangement is absence. The histological diagnosis is based on the positivity to the immunoreattivity of S-100.

 

Neuroradiological diagnosis

  • Magnetic Resonance Imaging (MRI) with and without contrast medium detects lesions < 2mm diameter;
  • Computerized Tomography (CT) is good in anatomical detailed or in the cases where MRI is contraindicated. It recognizes lesions > 15mm.

Differential diagnosis of Cerebellopontine angle lesions: Meningioma, Epidermoids, Other cranial nerve schwannomas (trigeminal schwannomas), Cholesteatoma, Aracnoid cyst, Lipoma, Haemangioma and Metastatic Tumors.

One of the most used classification based on neuroradiological criteria is the Koos Classification. It takes into consideration the maximum diameter of the tumor and the degree of compression/distortion of the brain stem.

Koos Classification

  • Grade I - Intracanalicular lesion < 1 cm
  • Grade II - Small tumor protruding into the APC, away from the cerebral trunk, up to 2cm
  • Grade III - Tumor in the CPA, deforms the cerebral trunk but not the 4th ventricles, up to 3cm
  • Grade IV - Tumor with displacement of the trunk, cranial nerves and 4th ventricles, > 3cm

Another used classification is the Hannover classification mainly based on the position of the mass and the degree of the compression/distortion of the brainstem.

Hannover Classification

  • T1 - Intrameatal tumor
  • T2 - Intrameatal and extrameatal tumor
  • T3a - Tumor filling the CPA cistern
  • T3b - Tumor reaching the brainstem
  • T4a - Tumor compressing the brainstem
  • T4b - Tumor severely displacing the brainstem and compressing the fourth ventricle

 

Neurootological diagnosis

Audiometric and audiologic studies

  • Pure tone audiogram (PTA)

  • Impedance test
  • Speech discrimination evaluation


  • Definition of serviceable hearing (modified Gardener-Robertson system and the AAO-HNS hearing classification system

Modified Gardener-Robertson System Class

Class Pure Tone/Speech Reception Threshold (dB HL) Speech Discrimination Score (%)
1 0–30  70–100
2  31–50  50–69
3  51–90  5–49
4  >90  1–4

the AAO-HNS Hearing Classification System

Class Pure tone average (0.5, 1, 2, 3 kHz measured in dB HL) Speech discrimination score (%)
A 0–30 70–100
B 31–50 50–100
C >50 50–100
D Any <50

 

Therapeutic management

The best choice depends on factors such as location, tumor size, symptoms, hearing function, age and general condition of the patient. Different strategies can be used:

  • Microsurgery (suboccipital also called retrosigmoid, translabyrinthine, transcochlear, subtemporal, presigmoid and middle cranial fossa approaches),
  • Radiotherapy (Gamma knife or Stereotaxic radiotherapy).
  • Serial radiologic observation.
  • Pharmacological treatment, dedicated to patients with NF2 (inhibitors of AKT, MAP kinase, EGRF tyrosine kinase, ErbB2, HER2, VEGF Receptor ): Bevacizumab, Trastuzumab, Erlotinib, Lapatinib, Honokiol.

Indications for the therapeutic management

  • For tumors of the internal acoustic meatus or in general measuring <1 cm, with modest clinical symptoms, “wait and see” can be a good option. This strategy can be useful to evaluate the growth rate of the tumor;
  • Symptomatic tumors or those compressing/deforming the brainstem, should be treated with both microsurgery or radiosurgery based on different factors;
  • Tumors with severe symptoms of brainstem compression or hydrocephalus or tumors with very large diameter (>3cm), should be addressed for surgical resection;
  • Radiosurgery has shown excellent results in treating tumors up to 25mm even though the maximum diameter is not the only parameter to be considered in indicating such treatment. It is also indicated in those patients with poor general condition unsuitable for surgical resection.

Risk of neurosurgical option

Hearing loss, facial paralysis, tinnitus, dysequilibrium, ocular complications, change of taste, intracranial haemorrage, brain injury, cerebrospinal fluid (CSF) leak, meningitis and mortality.

Endoscopic approaches to the intracanalicular acoustic schwannomas

The introduction of the transcanal/ transpromontorial endoscopic approach can improve the post-operative management of the patient for intracanalicular acoustic schwannomas.

 

 

References

Mark S. Greenberg, Handbook of Neurosurgery, Thieme.

Tumor Biology of Vestibular Schwannoma: A Review of Experimental Data on the Determinants of Tumor Genesis and Growth Characteristics, †Maurits de Vries, †Andel G. L. van der Mey, and *Pancras C. W. Hogendoorn

The Fully Endoscopic Acoustic Neuroma Surgery, Daniele Marchioni, MDa, Marco Carner, MDa, Alessia Rubini, MDa,*, João Flávio Nogueira, MDb, Barbara Masotto, MDc,
Matteo Alicandri-Ciufelli, MD, FEBORL-HNSd,e, Livio Presutti, MDd

Neuropathology for the Neuroradiologist: Antoni A and Antoni B Tissue Patterns F.J. Wippold, M. Lubner, R.J. Perrin, M. Lämmle and A. Perry, American Journal of Neuroradiology October 2007,  28 (9) 1633-1638;

Youmans Neurological Surgery, 4-Volume Set: Expert Consult 

Pathologic Basis of Disease, Robbins & Cotran, 9th Edition

The Inhibitory Effect of Honokiol, a Natural Plant Product, on Vestibular Schwannoma Cells, Lee JD, Lee YJ, Baek BJ, Lee BD, Koh JW, Lee WS, Lee YJ, Kwon BM, Laryngoscope, 122:162–166, 2012.

The changing clinical presentation of acoustic tumors in the MRI era. Selesnick SH, Jackler RK, Pitts LW. Laryngoscope 1993;103:431–436.

Management of Patients with Acoustic Neuromas: A Markov Decision Analysis, The Laryngoscope VC 2010 The American Laryngological, Rhinological and Otological Society, Inc.,

Guiding Patients Through the Choices for Treating Vestibular Schwannomas: Balancing Options and Ensuring Informed Consent, Huong T.PhamMDb, Douglas D. Backous, MD

www.orpha.net

ErbB Expression, Activation, and Inhibition with Lapatinib and Tyrphostin (AG825) in Human Vestibular Schwannomas Zana K. Ahmad, B.S.,1 Carrie M. Brown, M.D.,1 Roberto A. Cueva, M.D.,2 Allen F. Ryan, Ph.D.,1,3,4 and  Joni K. Doherty, M.D., Ph.D.1,4,5

Treatment of Vestibular Schwannoma Cells With ErbB Inhibitors, Bush ML, Burns SS, Oblinger J, Davletova S, Chang LS, Welling DB, Jacob A Otology & Neurotology 33:244Y257 2012.

Asymmetric sensorineural hearing loss caused by vestibular schwannoma: characteristic imaging features before and after treatment with stereotactic radiosurgery, Nicholas Krauses, md, Kathleen Tozer Fink, MD, James R.Fink, MD.

Management of 1000 Vestibular Schwannomas (Acoustic Neuromas): The Facial Nerve-Preservation and Restitution of Function. Samii M, Matthies C. Neurosurgery. 1997 Apr 1;40(4):684-695

 

 

Authors

 

Giannantonio Spena, MD

Neurosurgeon Consultant
University of Brescia
"Spedali Civili" Hospital Brescia (Italy)
Scientific Team - UpSurgeOn

 

Simona Serioli, MS

Medical Student
University of Brescia (Italy)
Scientific Team - UpSurgeOn


SUBSCRIBE TO JOIN THE COMMUNITY
Receive news, Theory modules and updates from neurosurgical community!