Acoustic Neuroma (Vestibular Schwannoma)

Acoustic neuroma — the older name for vestibular schwannoma — is a non-malignant tumor of the eighth cranial nerve (the vestibulocochlear nerve). The 2020 European Association of Neuro-Oncology (EANO) guideline describes it as the third most common non-malignant intracranial tumor after meningiomas and pituitary adenomas, and as making up over 80% of tumors in the cerebellopontine angle (PubMed PMID: 31504802).

Table of Contents

  1. What Is Acoustic Neuroma?
  2. Epidemiology and Types
  3. Symptoms and Clinical Presentation
  4. Diagnosis and Imaging
  5. Grading and Size Classification
  6. Management Options
  7. Microsurgery: Approaches and Outcomes
  8. Stereotactic Radiosurgery
  9. Observation and Active Monitoring
  10. Complications and Long-Term Effects
  11. NF2-Related Bilateral Disease
  12. Key Research Papers
  13. Featured Videos

What Is Acoustic Neuroma?

The EANO guideline notes that these tumors were once thought to arise from Schwann cells at one transition zone of the vestibulocochlear nerve, but in fact arise anywhere along the eighth cranial nerve: in about 80% of cases in its vestibular portion and in about 20% in its cochlear portion (PubMed PMID: 31504802). The name "acoustic neuroma" is therefore doubly inexact — the tumor is a schwannoma, and it usually starts on the balance (vestibular) part of the nerve rather than the hearing part.

In most people the tumor is on one side only; tumors on both sides are a hallmark of neurofibromatosis type 2 (NF2) (PubMed PMID: 31504802). Large tumors can cause trigeminal and facial nerve problems as well as brainstem compression and hydrocephalus (PubMed PMID: 31504802).

The facial nerve runs alongside the tumor inside the internal auditory canal (IAC); the EANO guideline notes its anterosuperior course through the canal as one reason some approaches involve more handling of the facial nerve (PubMed PMID: 31504802).

Epidemiology and Types

Reported incidence depends strongly on the population and period studied. The EANO guideline cites a United States registry rate of 1.09 per 100,000 per year for 2004–2010, rising with age to 2.93 per 100,000 per year at ages 65–74 (PubMed PMID: 31504802). A 2022 systematic review of population-based studies from Denmark, the Netherlands, Taiwan and the United States found more recent all-age rates of 3.0 to 5.2 per 100,000 person-years, peaking at 20.6 per 100,000 person-years at age 70 and over, and concluded that the often-quoted "1 per 100,000" figure is too low by up to 5-fold (PubMed PMID: 34464224).

Danish national data covering 1976–2015 show the rise in diagnosis over time: the incidence rate increased from 3 to 34 per million per year, which the authors attribute mainly to easier access to better diagnostics and to more tumors being found in older people; over the same period the median age at diagnosis rose from 49 to 60 years and tumors were smaller at diagnosis (PubMed PMID: 31807080).

Sporadic (Unilateral)

Most vestibular schwannomas are solitary tumors not linked to NF2 (PubMed PMID: 31504802). Inactivation of the NF2 tumor suppressor gene is considered a major event in how they form: one whole-exome sequencing study found evidence of NF2 inactivation, through loss of chromosome 22q or an NF2 mutation, in 77% of tumors, and the tumor cells consistently lack the NF2 gene product, merlin (PubMed PMID: 31504802).

The EANO guideline states that risk factors for vestibular schwannoma have scarcely been investigated; it cites a UK–Nordic case-control study that found a higher risk in women who had given birth than in women who had not, and a lower risk in current (but not former) smokers, with the reasons unclear (PubMed PMID: 31504802). The INTERPHONE case-control study (1,105 patients, 2,145 controls, 13 countries) found no increase in risk with ever having been a regular mobile phone user (odds ratio 0.85) or with 10 or more years since first regular use; it found elevated odds ratios only in the highest decile of cumulative call time, which the authors said could be due to chance, reporting bias or a causal effect, and they noted that the interval since mobile phones were introduced might be too short to detect an effect of a slowly growing tumor (PubMed PMID: 21862434).

NF2-Related (Bilateral)

About 4–6% of vestibular schwannomas are associated with NF2, an autosomal dominant condition caused by pathogenic variants in the NF2 gene on chromosome 22q, with a birth incidence of about 1 in 25,000–33,000 (PubMed PMID: 31504802). A clinical genetics review reports an average age of onset of 18 to 24 years, with almost all affected people developing tumors on both sides by age 30; people with NF2 may also develop schwannomas of other nerves, meningiomas and ependymomas (PubMed PMID: 20301380).

Symptoms and Clinical Presentation

The EANO guideline reports that most patients present with hearing loss on one side (94%) and tinnitus (83%), while vertigo and unsteadiness are reported in a widely varying 17–75% and are likely underreported (PubMed PMID: 31504802). In a surgical series of 1,000 tumors, the most frequent symptoms involved the hearing nerve (95%), the balance nerve (61%), the trigeminal nerve (9%) and the facial nerve (6%) (PubMed PMID: 8971818).

Unilateral Sensorineural Hearing Loss

Hearing loss on the side of the tumor is the most common symptom (PubMed PMID: 31504802). In the 1,000-tumor series, the reported symptom duration for hearing loss was 3.7 years, and among patients who were already deaf before surgery, 23% had become deaf gradually and 3% suddenly (PubMed PMID: 8971818).

Sudden sensorineural hearing loss (SSNHL) is linked to the tumor in both directions. In Korean national health-insurance data, 25.8% of 5,751 people with vestibular schwannoma had an earlier record of SSNHL, significantly more than matched controls, and a history of SSNHL was a significant risk factor for the tumor (hazard ratio 7.1) (PubMed PMID: 38088318). Looking from the other side, a 10-year series of 1,249 patients treated for SSNHL in southern China found a vestibular schwannoma on MRI in 14 (1.12%) (PubMed PMID: 32234257). The 2019 American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS) sudden hearing loss guideline update recommends that clinicians evaluate patients with SSNHL for retrocochlear pathology, such as this tumor, by obtaining MRI or auditory brainstem response (ABR) testing; it names MRI, CT if MRI cannot be done, and secondarily ABR, excludes audiometric follow-up alone as a reasonable workup, and does not specify a time frame (PubMed PMID: 31369359).

Tinnitus

Tinnitus is reported by 83% of patients at presentation according to the EANO guideline (PubMed PMID: 31504802). In the 1,000-tumor series, tinnitus was more common in patients who could still hear than in deaf patients, but it persisted in 46% of patients who were already deaf before surgery (PubMed PMID: 8971818).

Imbalance and Vestibular Dysfunction

In the 1,000-tumor series, vestibular disturbances most often took the form of unsteadiness while walking or vertigo, and the symptoms frequently fluctuated rather than being constant (PubMed PMID: 8971818). Vertigo and unsteadiness are reported in 17–75% of patients across studies (PubMed PMID: 31504802).

Facial Numbness

Trigeminal (facial sensation) disturbances were present in 9% of the 1,000-tumor series and were a key symptom leading to diagnosis in large tumors with brainstem compression (PubMed PMID: 8971818).

Facial Weakness

Facial nerve disturbance was present in 6% of the 1,000-tumor series at presentation (PubMed PMID: 8971818). Facial function is graded on the House-Brackmann scale; the EANO guideline states that the risk of lasting facial palsy after surgery depends on tumor size and on whether a paresis appears immediately after the operation (PubMed PMID: 31504802).

Brainstem and Cerebellar Compression

Large tumors may compress the brainstem and cause hydrocephalus (PubMed PMID: 31504802). For large tumors the EANO guideline states that surgical decompression is mandatory, potentially followed by fractionated radiotherapy or radiosurgery (PubMed PMID: 31504802).

Diagnosis and Imaging

Contrast-Enhanced MRI

The EANO guideline describes MRI as the method of choice for identifying a suspected vestibular schwannoma, with gadolinium contrast-enhanced T1-weighted scans considered the gold standard; its recommended protocol also includes standard T1- and T2-weighted sequences, diffusion-weighted imaging and FLAIR sequences (PubMed PMID: 31504802). Histological confirmation is not always required (PubMed PMID: 31504802).

Auditory Brainstem Response (ABR)

A 2013 meta-analysis of 43 studies (3,314 patients) found a pooled ABR sensitivity of 93.4% for vestibular schwannoma, falling to 85.8% for tumors under 1 cm and reaching 95.6% for tumors over 1 cm; pooled specificity was 82.0% (PubMed PMID: 23332407). The authors still described MRI as the gold standard (PubMed PMID: 23332407). In the southern Chinese SSNHL series, 2 of the 14 patients with a tumor had a normal ABR, and the authors judged MRI more suitable than ABR in their setting (PubMed PMID: 32234257).

Audiometry

Hearing tests (audiometry) are part of the workup and of follow-up; the EANO guideline lists MRI, audiometry and outpatient consultation as the components of monitoring (PubMed PMID: 31504802). In the southern Chinese series, the audiogram pattern, pure-tone hearing level and hearing recovery did not reliably predict which SSNHL patients had a tumor (PubMed PMID: 32234257).

Grading and Size Classification

Grading systems describe how far the tumor extends from the internal auditory canal toward the brainstem.

Koos Classification

As summarized in the EANO guideline (PubMed PMID: 31504802):

In the 1998 Koos surgical series, Grade II tumors were subdivided by size into IIA (under 1 cm) and IIB (1–1.8 cm) (PubMed PMID: 9488305).

Management Options

The EANO guideline lists observation, surgical resection, fractionated radiotherapy and radiosurgery as the current options, and states that the choice depends on clinical presentation, tumor size and the expertise of the treating center (PubMed PMID: 31504802). For small tumors it states that observation has to be weighed against radiosurgery; for large tumors, surgical decompression is mandatory; and, except for bevacizumab in NF2, it finds no role for drug treatment (PubMed PMID: 31504802). It also notes that the overall level of evidence for vestibular schwannoma treatment is low compared with other intracranial tumors (PubMed PMID: 31504802).

The guideline's authors write that the surgical team's experience is an important factor in outcome, suggesting treatment in high-volume centers (a good-practice point based on low-level evidence) (PubMed PMID: 31504802).

Microsurgery: Approaches and Outcomes

Microsurgical resection removes the tumor. The EANO guideline reports surgery-related mortality of 0.5% in large series, and concludes that there are not sufficient data to show any one surgical approach is superior for complete removal and nerve preservation (PubMed PMID: 31504802).

Retrosigmoid (Suboccipital) Approach

According to the EANO guideline, this approach is favored by neurosurgeons, is particularly used for tumors lying mainly in the cerebellopontine cistern or with significant mass effect, allows removal of tumors of various sizes and offers the possibility of hearing preservation; it gives excellent views of the brainstem, cranial nerves and blood vessels but needs some cerebellar retraction and gives only limited access to the far (fundal) end of the IAC (PubMed PMID: 31504802).

Translabyrinthine Approach

The EANO guideline describes this approach, usually performed by ENT surgeons, as usable for tumors of all sizes; removing the labyrinth causes complete loss of inner-ear function, so it is not suited to patients seeking hearing preservation. It gives excellent tumor access without retraction of the occipital or temporal lobe and a view of the whole facial nerve from the brainstem into its bony canal (PubMed PMID: 31504802).

Middle Fossa Approach

The EANO guideline states that this approach may be considered for patients with small tumors who wish to preserve residual hearing; it uses a temporal craniotomy above the zygoma and requires careful patient selection (PubMed PMID: 31504802). A 2025 meta-analysis of 32 observational studies (6,889 patients) found no significant difference in hearing preservation between the retrosigmoid and middle fossa approaches, and no significant difference in late facial nerve preservation between approaches, with fewer hydrocephalus and CSF-leak complications after the retrosigmoid approach (PubMed PMID: 39930308).

Facial Nerve and Hearing Outcomes

In a series of 1,000 resections, the facial nerve was kept anatomically intact in 93% of cases (PubMed PMID: 9092841). In the Koos series of small (Grade I and II) tumors removed by the retrosigmoid approach, full facial nerve function was kept in 88% of patients whose nerve was anatomically preserved, and the rest kept partial function; hearing was preserved in all 14 Grade I patients and in 87% of Grade II patients overall (PubMed PMID: 9488305). In a Norwegian comparison of tumors 30 mm or smaller, 79.8% of microsurgery patients had good facial function (House-Brackmann grade 1–2) (PubMed PMID: 15854240). The EANO guideline gives a risk of lasting facial palsy of 3% to 46%, depending on tumor size and immediate postoperative paresis, and reports hearing preservation in patients with normal hearing of over 50–75% immediately after surgery and at 2 and 5 years, and over 25–50% at 10 years (PubMed PMID: 31504802).

Stereotactic Radiosurgery

Stereotactic radiosurgery (SRS) delivers a high, tightly shaped dose of radiation in a single session and is commonly used for small to medium-sized tumors (PubMed PMID: 31504802). It does not remove the tumor; its aim is long-term prevention of growth while keeping nerve function (PubMed PMID: 9811917).

Single-Session Radiosurgery

The EANO guideline reports doses of 11 to 14 Gy and recommends a margin dose of 11–14 Gy, or 11–12 Gy when the risk of hearing loss is a critical issue (PubMed PMID: 31504802). It reports that contemporary series using margin doses of 12–14 Gy achieved 5-year tumor control of 90–99%, hearing preservation of 41–79% and facial nerve preservation of 95–100% (PubMed PMID: 31504802). In a Japanese series of 317 patients followed for a median of 7.8 years, actuarial progression-free survival was 93% at 5 years and 92% at 10 years; at margin doses of 13 Gy or less, hearing was preserved in 68%, transient facial palsy occurred in 1% and facial numbness in 2% (PubMed PMID: 16094154). An earlier US series of 162 patients treated at a higher average margin dose (16 Gy) reported 98% tumor control, normal facial function preserved in 79% at five years and unchanged hearing in 51% (PubMed PMID: 9811917).

Hearing tends to decline over the years after SRS. The EANO guideline cites a review in which the probability of keeping hearing was over 75–100% at 2 years, over 50–75% at 5 years and over 25–50% at 10 years, similar to selected microsurgery cases at 5 and 10 years (PubMed PMID: 31504802).

Fractionated Stereotactic Radiotherapy

For larger tumors, the EANO guideline states that fractionation is mandatory, and that fractionated or hypofractionated stereotactic radiotherapy using up to 10 fractions is increasingly used (PubMed PMID: 31504802). Six non-randomized studies cited by the guideline found similar hearing preservation, but a seemingly higher rate of facial palsy and trigeminal nerve dysfunction, with fractionated treatment than with single-session SRS (PubMed PMID: 31504802).

SRS vs. Surgery

In a prospective cohort of 82 patients with tumors under 3 cm, normal facial movement and serviceable hearing were more frequent after radiosurgery than after resection at 3 months, 1 year and last follow-up, quality-of-life scores declined only in the surgery group, and tumor control did not differ (100% vs 96%) (PubMed PMID: 16823303). In the Norwegian retrospective comparison, good facial function was reported in 94.8% after radiosurgery vs 79.8% after microsurgery, and treatment efficacy (no need for further treatment) was similar (PubMed PMID: 15854240).

Temporary enlargement of the tumor within 3 years after radiosurgery, termed pseudoprogression, is reported in up to 30% of patients; the EANO guideline states it is not a predictor of failure and recommends clinical and radiological observation with annual MRI during that period (PubMed PMID: 31504802).

Observation and Active Monitoring

Observation with repeated MRI ("wait and scan") is one of the standard options, and for small tumors the EANO guideline states it has to be weighed against radiosurgery (PubMed PMID: 31504802).

How many tumors grow varies by study and by definition of growth. The EANO guideline gives reported ranges of 30–70% and states that about 50% of tumors may be expected to grow over 5 years, with a mean growth in maximum diameter of 2.9 mm per year in series with quantitative long-term measurements (PubMed PMID: 31504802). A 2005 meta-analysis of 21 studies (1,345 patients, average follow-up 3.2 years) found growth in 43% and no growth or shrinkage in 57%, with an average growth rate of 1.9 mm per year; 20.0% of patients in 15 studies eventually left observation for treatment (PubMed PMID: 15744156). In the Danish national cohort (2,312 observed patients), 21% of tumors confined to the canal and 37% of tumors extending outside it had grown by 5 years, rising to 25% and 42% by 10 years, with growth occurring mainly within the first 5 years (PubMed PMID: 33068429).

Hearing can decline even without treatment. In a pooled analysis of 982 observed patients with tumors under 25 mm, hearing was preserved in 75% of those whose tumors grew 2.5 mm per year or less, compared with 32% of those with faster growth (PubMed PMID: 19538047). The 2005 meta-analysis reported hearing loss in 51% of 347 observed patients (PubMed PMID: 15744156).

For follow-up, the EANO guideline recommends annual MRI and audiometry for 5 years in conservatively treated, irradiated or incompletely removed tumors, with the intervals doubled thereafter if size is stable (a good-practice point) (PubMed PMID: 31504802). It notes that 7.2% of tumors in one large cohort grew after being stable for 5 years (PubMed PMID: 31504802).

Complications and Long-Term Effects

Long-term effects reported in the research include:

NF2-Related Bilateral Disease

In NF2, tumors on both sides threaten hearing in both ears. A 2017 systematic review of hearing outcomes in NF2 concluded that conservative management offers the best chance of keeping hearing in stable tumors, and noted that management decisions depend on many factors besides hearing (PubMed PMID: 28371358). The EANO guideline adds that NF2 tumors are often multifocal along the nerve, which makes surgery and radiation more difficult with higher recurrence rates, and that radiation is used with caution in young NF2 patients because of the risk of malignant transformation and new tumors (PubMed PMID: 31504802).

Key Research Papers

  1. Goldbrunner R, Weller M, Regis J, et al. EANO guideline on the diagnosis and treatment of vestibular schwannoma. Neuro Oncol. 2020;22(1):31–45. — PubMed PMID: 31504802
  2. Chandrasekhar SS, Tsai Do BS, Schwartz SR, et al. Clinical Practice Guideline: Sudden Hearing Loss (Update). Otolaryngol Head Neck Surg. 2019;161(1_suppl):S1–S45. — PubMed PMID: 31369359
  3. Jeong J, Lee YH, Kim S, Kim SH, Chang KH. Sudden sensorineural hearing loss and facial palsy in patients with vestibular schwannoma based on the population data of Korea. J Int Adv Otol. 2023;19(6):468–471. — PubMed PMID: 38088318
  4. Yang W, Mei X, Li X, et al. The prevalence and clinical characteristics of vestibular schwannoma among patients treated as sudden sensorineural hearing loss: a 10-year retrospective study in southern China. Am J Otolaryngol. 2020;41(4):102452. — PubMed PMID: 32234257
  5. Marinelli JP, Beeler CJ, Carlson ML, et al. Global incidence of sporadic vestibular schwannoma: a systematic review. Otolaryngol Head Neck Surg. 2022;167(2):209–214. — PubMed PMID: 34464224
  6. Reznitsky M, Petersen MMBS, West N, Stangerup SE, Cayé-Thomasen P. Epidemiology of vestibular schwannomas — prospective 40-year data from an unselected national cohort. Clin Epidemiol. 2019;11:981–986. — PubMed PMID: 31807080
  7. Reznitsky M, Petersen MMBS, West N, Stangerup SE, Cayé-Thomasen P. The natural history of vestibular schwannoma growth — prospective 40-year data from an unselected national cohort. Neuro Oncol. 2021;23(5):827–836. — PubMed PMID: 33068429
  8. INTERPHONE Study Group. Acoustic neuroma risk in relation to mobile telephone use: results of the INTERPHONE international case-control study. Cancer Epidemiol. 2011;35(5):453–464. — PubMed PMID: 21862434
  9. Evans DG. NF2-Related Schwannomatosis. GeneReviews. Seattle (WA): University of Washington; 1998, updated 2023. — PubMed PMID: 20301380
  10. Matthies C, Samii M. Management of 1000 vestibular schwannomas (acoustic neuromas): clinical presentation. Neurosurgery. 1997;40(1):1–9. — PubMed PMID: 8971818
  11. Samii M, Matthies C. Management of 1000 vestibular schwannomas (acoustic neuromas): the facial nerve — preservation and restitution of function. Neurosurgery. 1997;40(4):684–694. — PubMed PMID: 9092841
  12. Koors PD, Thacker LR, Coelho DH. ABR in the diagnosis of vestibular schwannomas: a meta-analysis. Am J Otolaryngol. 2013;34(3):195–204. — PubMed PMID: 23332407
  13. Koos WT, Day JD, Matula C, Levy DI. Neurotopographic considerations in the microsurgical treatment of small acoustic neurinomas. J Neurosurg. 1998;88(3):506–512. — PubMed PMID: 9488305
  14. Smouha EE, Yoo M, Mohr K, Davis RP. Conservative management of acoustic neuroma: a meta-analysis and proposed treatment algorithm. Laryngoscope. 2005;115(3):450–454. — PubMed PMID: 15744156
  15. Sughrue ME, Yang I, Aranda D, et al. The natural history of untreated sporadic vestibular schwannomas: a comprehensive review of hearing outcomes. J Neurosurg. 2010;112(1):163–167. — PubMed PMID: 19538047
  16. Stangerup SE, Caye-Thomasen P, Tos M, Thomsen J. The natural history of vestibular schwannoma. Otol Neurotol. 2006;27(4):547–552. — PubMed PMID: 16791048
  17. Kondziolka D, Lunsford LD, McLaughlin MR, Flickinger JC. Long-term outcomes after radiosurgery for acoustic neuromas. N Engl J Med. 1998;339(20):1426–1433. — PubMed PMID: 9811917
  18. Hasegawa T, Fujitani S, Katsumata S, et al. Stereotactic radiosurgery for vestibular schwannomas: analysis of 317 patients followed more than 5 years. Neurosurgery. 2005;57(2):257–265. — PubMed PMID: 16094154
  19. Myrseth E, Møller P, Pedersen PH, et al. Vestibular schwannomas: clinical results and quality of life after microsurgery or gamma knife radiosurgery. Neurosurgery. 2005;56(5):927–935. — PubMed PMID: 15854240
  20. Pollock BE, Driscoll CL, Foote RL, et al. Patient outcomes after vestibular schwannoma management: a prospective comparison of microsurgical resection and stereotactic radiosurgery. Neurosurgery. 2006;59(1):77–85. — PubMed PMID: 16823303
  21. Garcia-Torrico F, Mendieta CD, De Nigris Vasconcellos F, et al. Evaluating the effectiveness and complications of the retrosigmoid, translabyrinthine and middle fossa approaches in vestibular schwannoma surgical management: a comprehensive systematic review and meta-analysis of 6,889 patients. Neurosurg Rev. 2025;48(1):229. — PubMed PMID: 39930308
  22. Selesnick SH, Liu JC, Jen A, Newman J. The incidence of cerebrospinal fluid leak after vestibular schwannoma surgery. Otol Neurotol. 2004;25(3):387–393. — PubMed PMID: 15129122
  23. Govindaraj R, Chambers C, Kha M, et al. Tinnitus after treatment of vestibular schwannoma: a systematic review and comparative analysis of microsurgery and stereotactic radiosurgery. J Neurooncol. 2025;172(2):347–359. — PubMed PMID: 39969785
  24. Baguley DM, Moffat DA, Hardy DG. What is the effect of translabyrinthine acoustic schwannoma removal upon tinnitus? J Laryngol Otol. 1992;106(4):329–331. — PubMed PMID: 1613345
  25. Plotkin SR, Merker VL, Halpin C, et al. Bevacizumab for progressive vestibular schwannoma in neurofibromatosis type 2: a retrospective review of 31 patients. Otol Neurotol. 2012;33(6):1046–1052. — PubMed PMID: 22805104
  26. Lloyd SKW, King AT, Rutherford SA, et al. Hearing optimisation in neurofibromatosis type 2: a systematic review. Clin Otolaryngol. 2017;42(6):1329–1337. — PubMed PMID: 28371358
  27. Neff BA, Welling DB. Current concepts in the evaluation and treatment of neurofibromatosis type II. Otolaryngol Clin North Am. 2005;38(4):671–684. — PubMed PMID: 16005725

PubMed Topic Searches

The following PubMed topic searches retrieve current peer-reviewed literature on Acoustic Neuroma / Vestibular Schwannoma.

  1. PubMed: Vestibular schwannoma treatment outcomes
  2. PubMed: Acoustic neuroma radiosurgery
  3. PubMed: Vestibular schwannoma hearing preservation surgery
  4. PubMed: Acoustic neuroma natural history observation
  5. PubMed: NF2 bilateral vestibular schwannoma
  6. PubMed: Retrosigmoid translabyrinthine middle fossa approach
  7. PubMed: Acoustic neuroma facial nerve outcomes
  8. PubMed: Vestibular schwannoma MRI internal auditory canal

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