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Acoustic Neuroma

- Gamma knife single-dose stereotactic radiosurgery - Performed on an outpatient basis - For smaller tumors (<3 cm) or contraindications to microsurgery - Shown to have better tumor control rates than observation in some studies - Lower dose radiation has fewer complications.

- Fractionated stereotactic radiosurgery - Delivers a higher dose of radiation and less damage to healthy tissue - Requires multiple treatments and total radiation dose is higher than single-dose radiation - Suitable for all sizes of tumor

- Surgery is the recommended definitive treatment. - Lowest rate of recurrence, with up to 97.5% complete tumor removal - Retromastoid/retrosigmoid: can be used for all acoustic tumors - Middle cranial fossa: for small tumors with aim of preserving hearing - Translabyrinthine: for all but large tumors - Transpetrous approaches are safe for acoustic neuroma removal, and the postoperative complication rate is low. - The retrolabyrinthine approach seems to be a good hearing preservative approach, regardless of tumor volume.

para>Patients with NF2-associated vestibular schwannomas tend to have higher rates of surgical complications, treatment costs, and hospital stays compared to sporadic cases (3)[B].

Pediatric Considerations

Acoustic neuromas in children typically grow at slower rates compared to adults; this affects treatment outcomes (4)[B].

MEDICATION

A greater understanding of molecular tumorigenesis has yielded novel therapies. Suggested therapies

  • Bevacizumab may induce regression of progressive schwannomas by >40% and improves hearing.
  • An inhibitor of vascular endothelial growth factor (VEGF) synthesis, PTC299, is currently in phase II trials as a potential agent to treat vestibular schwannoma.
  • In vitro studies have shown that trastuzumab (an ErbB2 inhibitor) reduces vestibular schwannoma cell proliferation.

ISSUES FOR REFERRAL

If an asymptomatic tumor becomes symptomatic, intervention is usually indicated.

ADDITIONAL THERAPIES

Geriatric Considerations

Observation is suitable for elderly patients with contraindications to surgery and radiotherapy:

Observation is more likely to preserve hearing than radiotherapy or surgery, unless the patient has dizziness related to the tumor.

  • Gamma knife single-dose stereotactic radiosurgeryPerformed on an outpatient basisFor smaller tumors (<3 cm) or contraindications to microsurgeryShown to have better tumor control rates than observation in some studiesLower dose radiation has fewer complications.
  • Fractionated stereotactic radiosurgeryDelivers a higher dose of radiation and less damage to healthy tissueRequires multiple treatments and total radiation dose is higher than single-dose radiationSuitable for all sizes of tumor

SURGERY/OTHER PROCEDURES

  • Surgery is the recommended definitive treatment.
  • Lowest rate of recurrence, with up to 97.5% complete tumor removalRetromastoid/retrosigmoid: can be used for all acoustic tumorsMiddle cranial fossa: for small tumors with aim of preserving hearingTranslabyrinthine: for all but large tumorsTranspetrous approaches are safe for acoustic neuroma removal, and the postoperative complication rate is low.The retrolabyrinthine approach seems to be a good hearing preservative approach, regardless of tumor volume.
  • In one study, 79.1% of surgeries involved a translabyrinthine approach, with the remaining combined retrosigmoid and transtemporal (10.4%), middle fossa (6.0%), and stereotactic radiosurgery (4.5%). The highest complication rate was seen in the combined retrosigmoid and transtemporal approach cohort (5)[B].

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

  • Yearly MRI follow-up for slow-growing tumors is advised.
  • MRI and audiometry
  • In one study, composite quality of life (cQOL) score 0 to 5 years out of surgery was significantly highest among patients receiving stereotactic radiosurgery compared to microsurgery and observation. However, after 5 years, these differences were not seen (6)[B].
  • One study revealed that imbalance or disequilibrium may be indicative of tumor growth (7)[B].
  • Patients starting with serviceable hearing, average time to unserviceable hearing was 6.3 years (7)[B].

COMPLICATIONS

  • Mass effects: cranial nerve compression, hydrocephalus, brain stem compression, cerebellar tonsil herniation
  • Surgical complications: hearing loss, CSF leakage, facial nerve injury, headaches, meningitis
  • In one study, 22.4% of patients experienced postoperative complications; most commonly are facial weakness (13.4%), CSF leak (6.0%), and infection (3.0%) (5)[B].
  • In a larger study, 28.2% of patients experienced complications; most commonly are nervous system complications not elsewhere specified (15.2%) and facial paralysis (8.7%). Other complications included hydrocephalus, CSF leak, dysphagia, among others (8)[A].
  • CSF leak has been linked to increased patient BMI and translabyrinthine surgical approach (9)[B].
  • Another major complication is dizziness. There is a strong association between headaches and dizziness (10)[B].

REFERENCES

11 Kagoya R, Shinogami M, Kohno M, et al. Distortion-product otoacoustic emission tests evaluate cochlear function and differentiate cochlear and vestibular schwannoma. Otolaryngol Head Neck Surg. 2013;148(2):267-271.22 Elliot A, Hebb AL, Walling S, et al. Hearing preservation in vestibular schwannoma management. Am J Otolaryngol. 2015;36(4):526-534.33 Mahboubi H, Maducdoc MM, Yau AY, et al. Vestibular schwannoma excision in sporadic versus neurofibromatosis type 2 populations. Otolaryngol Head Neck Surg. 2015;153(5):822-831.44 Choi JW, Lee JY, Phi JH, et al. Clinical course of vestibular schwannoma in pediatric neurofibromatosis type 2. J Neurosurg Pediatr. 2014;13(6):650-657.55 Olshan M, Srinivasan VM, Landrum T, et al. Acoustic neuroma: an investigation of associations between tumor size and diagnostic delays, facial weakness, and surgical complications. Ear Nose Throat J. 2014;93(8):304-316.66 Robinett ZN, Walz PC, Miles-Markley B, et al. Comparison of long-term quality-of-life outcomes in vestibular schwannoma patients. Otolaryngol Head Neck Surg. 2014;150(6):1024-1032.77 Jethanamest D, Rivera AM, Ji H, et al. Conservative management of vestibular schwannoma: predictors of growth and hearing. Laryngoscope. 2015;125(9):2163-2168.88 Mahboubi H, Ahmed OH, Yau AY, et al. Complications of surgery for sporadic vestibular schwannoma. Otolaryngol Head Neck Surg. 2014;150(2):275-281.99 Copeland WR, Mallory GW, Neff BA, et al. Are there modifiable risk factors to prevent a cerebrospinal fluid leak following vestibular schwannoma surgery. J Neurosurg. 2015;122(2):312-316.1010 Carlson ML, Tveiten ˜V, Driscoll CL, et al. Long-term dizziness handicap in patients with vestibular schwannoma: a multicenter cross-sectional study. Otolaryngol Head Neck Surg. 2014;151(6):1028-1037.

ADDITIONAL READING

  • Arthurs BJ, Fairbanks RK, Demakas JJ, et al. A review of treatment modalities for vestibular schwannoma. Neurosurg Rev. 2011;34(3):265-279.
  • Fong B, Barkhoudarian G, Pezeshkian P, et al. The molecular biology and novel treatments of vestibular schwannomas. J Neurosurg. 2011;115(5):906-914.
  • Maniakas A, Saliba I. Conservative management versus stereotactic radiation for vestibular schwannomas: a meta-analysis of patients with more than 5 years' follow-up. Otol Neurotol. 2012;33(2):230-238.
  • Palmisano S, Schwartzbaum J, Prochazka M, et al. Role of tobacco use in the etiology of acoustic neuroma. Am J Epidemiol. 2012;175(12):1243-1251.
  • Repacholi MH, Lerchl A, R ¶ ¶sli M, et al. Systematic review of wireless phone use and brain cancer and other head tumors. Bioelectromagnetics. 2012;33(3):187-206.
  • Stangerup SE, Thomsen J, Tos M, et al. Long-term hearing preservation in vestibular schwannoma. Otol Neurotol. 2010;31(2):271-275.

CODES

ICD10

D33.3 Benign neoplasm of cranial nerves

ICD9

225.1 Benign neoplasm of cranial nerves

SNOMED

acoustic neuroma (disorder)

CLINICAL PEARLS

  • The most common presenting signs and symptoms are unilateral sensorineural hearing loss, poor speech discrimination, and tinnitus
  • May present as sudden deafness
  • MRI with gadolinium is the diagnostic gold standard.
  • The commonly used treatment options include observation, stereotactic radiosurgery, fractionated radiotherapy, and microsurgery.