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vestibular schwannoma (acoustic neuroma)

schwannoma or neurilemmoma of 8th nerve; acoustic neuroma is misnomer. Etiology: - idiopathic sporadic unilateral 95% - cancer susceptibility syndromes - neurofibromatosis type 2 - schwannomatosis Epidemiology: - 8% of all intracranial neoplasms - lifetime prevalence of 1 in 500 persons - increasing incidence due to enhanced detection - most common in 6th or 7th decade in life - 20 cases per 100,000 person years [8] Pathology: 1) arise from myelinating Schwann cells of vestibular division of cranial nerve VIII [8] 2) compressive growth with the internal auditory canal/meatus results in unilateral tinnitus & hearing loss 3) compromise of cranial nerves VII & VIII, the brain stem & the cerebellum may occur Clinical manifestations: 1) sensorineural hearing loss a) tinnitus &/or vertigo may be presenting symptoms b) hearing loss is usually unilateral (90%) [3,8] c) Weber test lateralizes to the unaffected ear 2) symptoms are generally progressive rather than episodic 3) symptoms are often unilateral 4) vestibular symptoms (unsteadiness, balance issues) 5) acoustic & vestibular symptoms are not reliable indicators of tumor growth [8] 6) cranial nerves 5, 7, 9, 10, 11 may be affected with tumor progression [2] 7) even large schwannomas generally do not affect facial-nerve, trigeminal motor, or lower cranial-nerve dysfunction [8] 8) abnormal finger to nose test suggests compression of cerebellum Special laboratory: - audiometry 6 months after diagnostic MRI, then annually - confirmatory biopsy rarely needed [8] Radiology: - magnetic resonance imaging (MRI) of the posterior fossa & internal auditory canal with gadolinium contrast - yield of MRI for vestibular schwannoma diagnosis < 3% [7] - once diagnosed, serial imaging should be obtained at annually, regardless of symptoms [8] Differential diagnosis: - facial-nerve schwannoma - meningioma - malignant peripheral-nerve sheath tumors - metastases from primary tumors at other sites - otosclerosis: associated with conductive hearing loss* - cholesteoma: associated with conductive hearing loss* * Weber test lateralizes to affected ear Complications: - compression of cochlear nerve or labyrinthine artery - impaired circulation of CSF - inflammation mediated by schwannoma - as the tumor enlarges, it compresses cranial nerves & the cerebellum [3] Management: - referral to otorhinolaryngologist - stereotactic radiosurgery - gamma-knife radiosurgery - maximal neoplasm diameter < 3.0 cm in the cerebellopontine angle - complications include: brain-stem edema, trigeminal neuralgia, hydrocephalus [8] - upfront radiosurgery for small & medium size tumors results in greater tumor reduction at 4 years than treatment with tumor growth [10] - microsurgical resection - treatment of choice for large neoplasm associated with: - symptomatic brain-stem compression, hydrocephalus, trigeminal neuralgia [8] - general anesthesia, operating microscope, intraoperative neural monitoring - sensorineural hearing loss & vestibular dysfunction are not reversed with treatment [8] - conservative management - prioritizing preservation of neurologic function vs cure - potential for overtreatment resulting in unnecessary complications & health care expenses - untreated vestibular schwannoma in patients >= 70 years not associated with shorter lifespan [11] - investigational drug treatment includes aspirin & monoclonal antibodies - no strong evidence any treatment is superior to others - some patients may require rehabilitation

General

benign cranial nerve neoplasm neuroma schwannoma (neurilemoma, neurinoma)

References

  1. UCLA Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 12-15, 2001
  2. UpToDate 14.1 http://www.utdol.com
  3. Geriatric Review Syllabus, 7th edition Parada JT et al (eds) American Geriatrics Society, 2010 - Geriatric Review Syllabus, 11th edition (GRS11) Harper GM, Lyons WL, Potter JF (eds) American Geriatrics Society, 2022
  4. McDonald R Acoustic neuroma: what the evidence says about evaluation and treatment. J Fam Pract. 2011 Jun;60(6):E1-4. PMID: 21647465
  5. deprecated reference
  6. Acoustic Neuroma. NIH Consensus Statement Online 1991 Dec 11-13;9(4):1-24 http://consensus.nih.gov/cons/087/087_statement.htm
  7. Dunn IF, Bi WL, Mukundan S et al. Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines on the Role of Imaging in the Diagnosis and Management of Patients With Vestibular Schwannomas. Neurosurgery. 2018 Feb 1;82(2)E32-34. PMID: 29309686 https://academic.oup.com/neurosurgery/article/82/2/E32/4764045 - Sweeney AD, Carlson ML, Shepard, NT. Congress of Neurological Surgeons Systematic Review and Evidence-Based Guideline on Otologic and Audiologic Screening for Patients With Vestibular Schwannomas. Congress of Neurological Surgeons. 2017. Neurosurgery. 2018 Feb 1;82(2):E29-E31. PMID: 29309699 https://www.cns.org/guidelines/guidelines-management-patients-vestibular-schwannoma/chapter_2
  8. Carlson ML, Link MJ Vestibular Schwannomas. N Engl J Med 2021; 384:1335-1348. April 8. PMID: 33826821 https://www.nejm.org/doi/full/10.1056/NEJMra2020394
  9. Gupta VK, Thakker A, Gupta KK. Vestibular schwannoma: what we know and where we are heading. Head Neck Pathol. 2020;14(4):1058-1066 PMID: 32232723 PMCID: PMC7669921 Free PMC article https://link.springer.com/article/10.1007/s12105-020-01155-x
  10. Dhayalan D, Tveiten OV, Finnkirk M et al Upfront Radiosurgery vs a Wait-and-Scan Approach for Small- or Medium-Sized Vestibular Schwannoma. The V-REX Randomized Clinical Trial. JAMA. 2023;330(5):421-431. PMID: 37526718 PMCID: PMC10394573 Free PMC article https://jamanetwork.com/journals/jama/fullarticle/2807745
  11. Mistarz N, Reznitsky M, Hostmark K et al Life Expectancy After Diagnosis of a Vestibular Schwannoma in Patients 70 Years and Older. JAMA Otolaryngol Head Neck Surg. 2023 Oct 26. PMID: 37883070 https://jamanetwork.com/journals/jamaotolaryngology/fullarticle/2811314
  12. Vestibular Schwannoma (Acoustic Neuroma) and Neurofibromatosis [NIDCD Health Information] http://www.nidcd.nih.gov/health/hearing/acoustic_neuroma.asp