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Table of Contents    
Year : 2013  |  Volume : 61  |  Issue : 6  |  Page : 683-686

Hearing improvement following gamma knife radiosurgery for an intra-canalicular vestibular schwannoma

1 Department of Neurosurgery and Gamma Knife, All India Institute of Medical Sciences, New Delhi, India
2 Department of Neurosurgery, Mayo Clinic School of Medicine, Mayo Clinic Health System, Mankato, Minnesota - 56001, USA

Date of Submission02-Sep-2013
Date of Decision09-Sep-2013
Date of Acceptance03-Dec-2013
Date of Web Publication20-Jan-2014

Correspondence Address:
Shashank S Kale
Department of Neurosurgery and Gamma Knife, All India Institute of Medical Sciences, New Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.125382

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How to cite this article:
Raheja A, Sharma MS, Singh M, Aggarwal D, Kale SS, Sharma BS. Hearing improvement following gamma knife radiosurgery for an intra-canalicular vestibular schwannoma. Neurol India 2013;61:683-6

How to cite this URL:
Raheja A, Sharma MS, Singh M, Aggarwal D, Kale SS, Sharma BS. Hearing improvement following gamma knife radiosurgery for an intra-canalicular vestibular schwannoma. Neurol India [serial online] 2013 [cited 2023 Jun 6];61:683-6. Available from:


Though considerable controversy exists regarding the natural history of sporadic vestibular schwannoma (VS), it is generally considered that they tend to progress both in terms of size and hearing impairment. [1],[2] Gamma knife radiosurgery (GKRS) is now accepted as a safe and effective modality for the treatment of small and moderate sized VS as the long-term data indicates growth arrest and stable neurological function over time. Whereas initial reports were concerned mainly with stable tumor growth, sometimes at the expense of hearing, more recent literature documents hearing preservation in select cases. [3],[4],[5],[6] Thus, it may be argued that GKRS may be the only non-invasive modality for preserving hearing, especially in smaller tumors when hearing is relatively intact. [7],[8]

A 37-year-old male patient presented with acute onset gradually progressive hearing loss on the left side and retro-auricular pain of 5 months duration. He also developed gradually worsening ipsilateral facial weakness for the last 6 weeks prior to this presentation. A short course of oral steroids failed to prevent decline in the symptoms. Examination revealed sensorineural hearing deficit in the left ear and a House-Brackmann grade III lower motor neuron type of left facial paresis. Pure tone audiometry revealed a moderate sensorineural hearing loss (50 dB) in the left ear [Figure 1]a. Contrast magnetic resonance imaging (MRI) of the brain revealed a small left intracanalicular VS [Figure 2]a. After appropriate counseling, primary GKRS was performed using a Leksell gamma knife unit B model. A tumor volume of 216.6 mm 3 was treated with a marginal dose of 12 Gy (50% isodose line) to achieve 92% coverage using 6 isocenters. Image fusion was performed using stereotactic MR and computer tomography images for better accuracy [Figure 3]. The brainstem, cochlea and the VII-VII th cranial nerve complex did not receive radiation doses in excess of 1.5, 9.6 and 9.8 Gy respectively. The cochlea received a mean dose of 3.5 Gy. Subsequent follow-up involved serial clinical, radiological and audiometric assessments. The hearing loss improved to 27 dB at 6 months follow-up [Figure 1]b. At this point in time, there was no facial weakness. Hearing improvement and normal facial nerve function was sustained at 21 months follow-up [Figure 1]c, [Figure 4]. Serial MRIs revealed stable tumor dimensions over time [Figure 2]b.
Figure 1: Pure tone audiograms (a) Pre gamma knife, (b) 6 months post gamma knife, and (c) 21 months post gamma knife showing a gradual and sustained improvement in hearing

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Figure 2: Axial and coronal contrast enhanced magnetic resonance images (a) Pre gamma Knife and (b) 21 months post gamma knife revealing a stable intracanalicular vestibular schwannoma (arrow)

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Figure 3: Leksell gamma plan using axial stereotactic (a) computed tomography and (b) magnetic resonance images. The intracanalicular vestibular schwannoma has been segmented in red, the basal turn of the cochlea in green, the brainstem in magenta, and the VII - VIIIth complex in peach. 12 Gy was delivered to the 50% isodose line (yellow) using 6 isocenters

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Figure 4: Follow - up clinical photographs at 21 months post gamma knife showing intact facial nerve function

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The place of GKRS in preserving hearing in patients with sporadic, non-familial, VS is still being defined [Table 1]. [3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13] The role of GKRS in the treatment of patients with type 2 neurofibromatosis remains controversial but may help arrest the inevitable progression of hearing loss. [14] Level one evidence concludes that the functional outcome and quality of life is better after GKRS when compared to microsurgery. [13] In light of the fact that most studies indicate that the natural history of disease reveals a trend toward hearing loss, [1],[2] GKRS may remain the single best option of preserving hearing in a select group of patients with smaller tumors and relatively intact hearing. [4],[7],[8],[9] This case illustrates the point.
Table 1: Serviceable hearing preservation after gamma knife radiosurgery from various studies

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Various factors have been implicated in hearing preservation in GKRS for VS, which include grade 1 pre-operative Gardner-Robertson hearing, speech discrimination score ≥80%, age <60 years, intracanalicular tumor location, low intracanalicular dose, tumor volume <0.75 cc, ventral cochlear nucleus dose ranging from ≤9 Gy to ≤10 Gy, lesser tumor coverage, normal auditory brainstem response and early resection of intracanalicular VS when acutely symptomatic. [3],[4],[5],[6],[11],[12],[14],[15] The radiation tolerance limit for the cochlea remains controversial and has been variously reported in literature to range from 3 to 5.3 Gy. [3],[9],[11],[14],[16],[17]

Niranjan et al. [18] in their study observed overall hearing improvement in 21/487 (4.3%) patients with VS undergoing GKRS over a 10 year interval. In a separate study conducted by the same authors in 29 patients with unilateral intracanalicular VS, the overall hearing preservation rate was 73% out of which 5 (17.2%) patients had hearing improvement. [8] They concluded that GKRS (using conformal dose planning, small-beam geometry, and ≤14 Gy to the margin) prevents tumor growth and achieves excellent hearing preservation rates. [8]

Yet, GKRS also runs a risk of causing hearing deterioration in patients with preserved auditory function. The risks of hearing loss have been reported to be between 22% and 68% respectively. [9]

Conventional wisdom has dictated that the trigger to perform GKRS in patients with small, stable VS is progressive hearing loss. However, it may be ethically, professionally and medico-legally prudent to discuss direct upfront GKRS in the management of these patients when the cochlear reserve is optimum. [14]

 » References Top

1.Sughrue ME, Kane AJ, Kaur R, Barry JJ, Rutkowski MJ, Pitts LH, et al. A prospective study of hearing preservation in untreated vestibular schwannomas. J Neurosurg 2011;114:381-5.  Back to cited text no. 1
2.Sughrue ME, Yang I, Aranda D, Lobo K, Pitts LH, Cheung SW, et al. The natural history of untreated sporadic vestibular schwannomas: A comprehensive review of hearing outcomes. J Neurosurg 2010;112:163-7.  Back to cited text no. 2
3.Brown M, Ruckenstein M, Bigelow D, Judy K, Wilson V, Alonso-Basanta M, et al. Predictors of hearing loss after gamma knife radiosurgery for vestibular schwannomas: Age, cochlear dose, and tumor coverage. Neurosurgery 2011;69:605-13.  Back to cited text no. 3
4.Hasegawa T, Kida Y, Kato T, Iizuka H, Yamamoto T. Factors associated with hearing preservation after Gamma Knife surgery for vestibular schwannomas in patients who retain serviceable hearing. J Neurosurg 2011;115:1078-86.  Back to cited text no. 4
5.Kano H, Kondziolka D, Khan A, Flickinger JC, Lunsford LD. Predictors of hearing preservation after stereotactic radiosurgery for acoustic neuroma. J Neurosurg 2009;111:863-73.  Back to cited text no. 5
6.Kim CH, Chung KW, Kong DS, Nam DH, Park K, Kim JH, et al. Prognostic factors of hearing preservation after gamma knife radiosurgery for vestibular schwannoma. J Clin Neurosci 2010;17:214-8.  Back to cited text no. 6
7.Iwai Y, Yamanaka K, Kubo T, Aiba T. Gamma knife radiosurgery for intracanalicular acoustic neuromas. J Clin Neurosci 2008;15:993-7.  Back to cited text no. 7
8.Niranjan A, Lunsford LD, Flickinger JC, Maitz A, Kondziolka D. Dose reduction improves hearing preservation rates after intracanalicular acoustic tumor radiosurgery. Neurosurgery 1999;45:753-62.  Back to cited text no. 8
9.Baschnagel AM, Chen PY, Bojrab D, Pieper D, Kartush J, Didyuk O, et al. Hearing preservation in patients with vestibular schwannoma treated with Gamma Knife surgery. J Neurosurg 2013;118:571-8.  Back to cited text no. 9
10.Kondziolka D, Lunsford LD, McLaughlin MR, Flickinger JC. Long-term outcomes after radiosurgery for acoustic neuromas. N Engl J Med 1998;339:1426-33.  Back to cited text no. 10
11.Massager N, Nissim O, Delbrouck C, Delpierre I, Devriendt D, Desmedt F, et al. Irradiation of cochlear structures during vestibular schwannoma radiosurgery and associated hearing outcome. J Neurosurg 2007;107:733-9.  Back to cited text no. 11
12.Paek SH, Chung HT, Jeong SS, Park CK, Kim CY, Kim JE, et al. Hearing preservation after gamma knife stereotactic radiosurgery of vestibular schwannoma. Cancer 2005;104:580-90.  Back to cited text no. 12
13.Pollock BE, Driscoll CL, Foote RL, Link MJ, Gorman DA, Bauch CD, et al. Patient outcomes after vestibular schwannoma management: A prospective comparison of microsurgical resection and stereotactic radiosurgery. Neurosurgery 2006;59:77-85.  Back to cited text no. 13
14.Sharma MS, Singh R, Kale SS, Agrawal D, Sharma BS, Mahapatra AK. Tumor control and hearing preservation after Gamma Knife radiosurgery for vestibular schwannomas in neurofibromatosis type 2. J Neurooncol 2010;98:265-70.  Back to cited text no. 14
15.Meiteles LZ, Liu JK, Couldwell WT. Hearing restoration after resection of an intracanalicular vestibular schwannoma: A role for emergency surgery? Case report and review of the literature. J Neurosurg 2002;96:796-800.  Back to cited text no. 15
16.Linskey ME. Hearing preservation in vestibular schwannoma stereotactic radiosurgery: What really matters? J Neurosurg 2008;109 Suppl: 129-36.  Back to cited text no. 16
17.Yang I, Aranda D, Han SJ, Chennupati S, Sughrue ME, Cheung SW, et al. Hearing preservation after stereotactic radiosurgery for vestibular schwannoma: A systematic review. J Clin Neurosci 2009;16:742-7.  Back to cited text no. 17
18.Niranjan A, Lunsford LD, Flickinger JC, Maitz A, Kondziolka D. Can hearing improve after acoustic tumor radiosurgery? Neurosurg Clin N Am 1999;10:305-15.  Back to cited text no. 18


  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

  [Table 1]

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