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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.



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)


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

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



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.


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. 



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.




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.

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

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





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