Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 16 peer-reviewed journal articles Updated
Otolaryngology

Staging, Subtypes, and NF2

At a Glance

Vestibular schwannomas are graded using the Koos classification system, which measures tumor size and pressure on the brainstem. Most tumors are sporadic and affect one ear, while bilateral tumors are usually caused by a genetic condition called Neurofibromatosis Type 2 (NF2).

When you receive an MRI report or a pathology summary for a vestibular schwannoma, you will likely encounter several classification systems. These systems help your care team describe the size, location, and impact of the tumor, which in turn guides your treatment decisions.

Understanding Location: Intracanalicular vs. Extracanalicular

The location of your tumor is often described in relation to the internal auditory canal (IAC), a narrow bony tunnel that houses the hearing, balance, and facial nerves.

  • Intracanalicular: This means the tumor is confined entirely within the bony canal [1][2]. These are typically small tumors caught early.
  • Extracanalicular: This means the tumor has grown out of the canal and into the cerebellopontine angle (CPA), the fluid-filled space between the ear and the brainstem [2][3].

The Koos Classification System

The Koos system is the most widely used scale for grading the size and “mass effect” (the pressure a tumor puts on surrounding structures) of a vestibular schwannoma [4][5].

Grade Description Typical Size & Impact
Grade I Small, intracanalicular tumor [1]. Confined to the internal auditory canal [2].
Grade II Small, extracanalicular tumor. Usually up to 2 cm; it has emerged into the CPA but does not touch the brainstem [1][2].
Grade III Medium-sized tumor. Up to 3 cm; the tumor reaches the brainstem but does not yet displace or compress it [1][4].
Grade IV Large tumor. Larger than 3 cm; it causes significant displacement or compression of the brainstem and surrounding nerves [4][2].

Grading Your Hearing

Doctors use standardized scales to track your hearing health. These scales help determine if you have “serviceable hearing,” which means the ear is still useful for communication.

  • AAO-HNS Scale: This system uses four classes (A, B, C, D). Classes A and B are considered serviceable hearing [6][7].
    • Class A: Excellent hearing (Pure Tone Average ≤ 30 dB and Speech Discrimination Score ≥ 70%) [8].
    • Class B: Good hearing (Pure Tone Average ≤ 50 dB and Speech Discrimination Score ≥ 50%) [6].
  • Gardner-Robertson (GR) Scale: A 5-point scale where Grade 1 is “good,” Grade 2 is “serviceable,” and Grades 3-5 represent non-serviceable hearing or total deafness [9][10].

Sporadic VS vs. NF2

Most vestibular schwannomas are sporadic, but a small percentage are related to a genetic condition called Neurofibromatosis Type 2 (NF2).

  • Sporadic (Non-genetic): These account for about 95% of cases. They typically involve a single tumor on one side and usually develop in adults between ages 30 and 60 [11]. While the tumor itself has mutations in the NF2 gene, these mutations are somatic (restricted to the tumor cells) and not passed down to children [12][13].
  • NF2-Related: This is a hereditary condition caused by a germline mutation (present in all cells). The hallmark of NF2 is bilateral vestibular schwannomas—tumors on both the left and right sides [11][14]. NF2-related tumors often appear at a younger age and can be more aggressive or difficult to treat than sporadic tumors [15][16].

If you have tumors on both sides or a strong family history of such growths, your doctor will likely recommend genetic counseling and testing for NF2 [11][12].

Common questions in this guide

What does the Koos classification mean for my vestibular schwannoma?
The Koos system grades the size of your tumor and how much pressure it puts on surrounding brain structures. Grade I tumors are small and confined to the ear canal, while Grade IV tumors are large and compress the brainstem.
What is the difference between an intracanalicular and extracanalicular tumor?
An intracanalicular tumor is located entirely within the bony tunnel of the inner ear. An extracanalicular tumor has grown outside this canal and into the fluid-filled space between the ear and the brainstem.
How do doctors measure if I still have serviceable hearing?
Doctors use scales like the AAO-HNS or Gardner-Robertson systems to track your hearing. These tests measure how loud sounds need to be for you to hear them and how well you can understand spoken words to determine if your ear is still useful for communication.
Is my vestibular schwannoma hereditary?
About 95% of vestibular schwannomas are sporadic, meaning they happen by chance and are not passed down to children. However, tumors on both sides of the head are a hallmark of Neurofibromatosis Type 2 (NF2), a genetic condition that runs in families.
When should I be tested for Neurofibromatosis Type 2 (NF2)?
You should consider genetic counseling and testing for NF2 if you have vestibular schwannomas on both your left and right sides, if tumors appeared at an unusually young age, or if you have a strong family history of brain or spine tumors.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.What is my Koos classification, and how does it affect my treatment options?
  2. 2.Am I currently in the 'serviceable hearing' category on the Gardner-Robertson or AAO-HNS scale?
  3. 3.Does the tumor show any signs of extending out of the internal auditory canal (extracanalicular)?
  4. 4.Is there any evidence of brainstem compression or displacement on my MRI?
  5. 5.Since I have a tumor on one side, is there any reason to suspect NF2, or is this likely a sporadic case?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (16)
  1. 1

    The prevalence of vestibular schwannoma among patients treated as sudden sensorineural hearing loss.

    Fujita T, Saito K, Kashiwagi N, et al.

    Auris, nasus, larynx 2019; (46(1)):78-82 doi:10.1016/j.anl.2018.06.008.

    PMID: 30042019
  2. 2

    Diagnostics and therapy of vestibular schwannomas - an interdisciplinary challenge.

    Rosahl S, Bohr C, Lell M, et al.

    GMS current topics in otorhinolaryngology, head and neck surgery 2017; (16()):Doc03 doi:10.3205/cto000142.

    PMID: 29279723
  3. 3

    Natural History of Growing Sporadic Vestibular Schwannomas During Observation: An International Multi-Institutional Study.

    Marinelli JP, Carlson ML, Hunter JB, et al.

    Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology 2021; (42(8)):e1118-e1124 doi:10.1097/MAO.0000000000003224.

    PMID: 34121081
  4. 4

    Koos Classification of Vestibular Schwannomas: A Reliability Study.

    Erickson NJ, Schmalz PGR, Agee BS, et al.

    Neurosurgery 2019; (85(3)):409-414 doi:10.1093/neuros/nyy409.

    PMID: 30169695
  5. 5

    Automated Koos Classification of Vestibular Schwannoma.

    Kujawa A, Dorent R, Connor S, et al.

    Frontiers in radiology 2022; (2()):837191 doi:10.3389/fradi.2022.837191.

    PMID: 37492670
  6. 6

    Time-based Assessment of Hearing Preservation Rates After Microsurgical Resection of Vestibular Schwannomas: A Systematic Review.

    Hunt AA, Cass ND, Coughlin A, Gubbels SP

    Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology 2020; (41(5)):679-685 doi:10.1097/MAO.0000000000002598.

    PMID: 32150025
  7. 7

    [Hearing results after middle fossa removal of small (T1/T2) vestibular schwannomas].

    Scheich M, Ehrmann-Müller D, Shehata-Dieler W, Hagen R

    HNO 2017; (65(9)):751-757 doi:10.1007/s00106-016-0228-5.

    PMID: 27590491
  8. 8

    Factors Affecting Speech Discrimination After Vestibular Schwannoma Resection.

    Kalmanson O, Olson M, Ovard O, et al.

    Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology 2024; (45(8)):e595-e601 doi:10.1097/MAO.0000000000004252.

    PMID: 39010263
  9. 9

    [Hearing classification in patients with vestibular schwannoma using German-language test procedures].

    Rahne T, Plontke SK, Vordermark D, et al.

    HNO 2021; (69(9)):750-758 doi:10.1007/s00106-020-00948-4.

    PMID: 32975608
  10. 10

    Age, preoperative tumor volume and widening of the internal acoustic meatus are independent factors associated with poor preoperative hearing in vestibular schwannoma patients - results of a single-center retrospective analysis.

    Dörner L, Suhm EM, Ries V, et al.

    Neurosurgical review 2024; (47(1)):262 doi:10.1007/s10143-024-02419-8.

    PMID: 38850456
  11. 11

    [Update on diagnostics and microsurgical treatment of vestibular schwannoma].

    Ebner FH, Tatagiba M

    Der Nervenarzt 2019; (90(6)):578-586 doi:10.1007/s00115-019-0721-7.

    PMID: 31076802
  12. 12

    Characterization of a newly established schwannoma cell line from a sporadic vestibular schwannoma patient.

    Xue L, He W, Wang Z, et al.

    American journal of translational research 2021; (13(8)):8787-8803.

    PMID: 34539995
  13. 13

    Genetic landscape of sporadic vestibular schwannoma.

    Håvik AL, Bruland O, Myrseth E, et al.

    Journal of neurosurgery 2018; (128(3)):911-922.

    PMID: 28409725
  14. 14

    Genome-wide association analysis identifies a susceptibility locus for sporadic vestibular schwannoma at 9p21.

    Sadler KV, Bowes J, Rowlands CF, et al.

    Brain : a journal of neurology 2023; (146(7)):2861-2868 doi:10.1093/brain/awac478.

    PMID: 36546557
  15. 15

    Vestibular schwannoma associated with neurofibromatosis type 2: Clinical course following stereotactic radiosurgery.

    Kim J, Byeon Y, Song SW, et al.

    Frontiers in oncology 2022; (12()):996186 doi:10.3389/fonc.2022.996186.

    PMID: 36185258
  16. 16

    The tumour immune microenvironment is enriched but suppressed in vestibular schwannoma compared to meningioma: therapeutic implications for NF2-related schwannomatosis.

    Gregory GE, Haley MJ, Jones AP, et al.

    Acta neuropathologica communications 2025; (13(1)):256 doi:10.1186/s40478-025-02176-9.

    PMID: 41437121

This page explains vestibular schwannoma staging and NF2 classification for educational purposes only. Always consult your neurologist or ENT specialist to interpret your specific MRI and hearing results.

Get notified when new evidence is published on Vestibular schwannoma.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.