Irradiation of cochlear structures during vestibular schwannoma radiosurgery and associated hearing outcome

Restricted access

Object

The purpose of this study was to measure the dose of radiation delivered to the cochlea during a Gamma knife surgery (GKS) procedure for treatment of patients with vestibular schwannomas (VSs), and to analyze the relationship between cochlear irradiation and the hearing outcome of these patients.

Methods

Eighty-two patients with VSs were treated with GKS using a marginal dose of 12 Gy. No patient had neurofibromatosis Type 2 disease, and all had a Gardner–Robertson hearing class of I to IV before treatment, and a radiological and audiological follow-up of at least 1-year after GKS. The dosimetric data of the volume of the cochlea were retrospectively analyzed and were correlated with the auditory outcome of patients.

Results

The mean radiation dose delivered to the cochlear volume ranged from 1.30 to 10.00 Gy (median 4.15 Gy). The cochlea received significantly higher radiation doses in patients with worsening of hearing after GKS. A highly significant association between the cochlear and the intracanalicular dose of radiation delivered during GKS was found.

Conclusions

During GKS for VSs, relatively high doses of radiation can be delivered to the cochlea. Worsening of hearing after GKS can be the consequence of either radiation injury to the cochlea or the irradiation dose delivered into the auditory canal, or both.

Abbreviations used in this paper:CT = computed tomography; GKS = Gamma knife surgery; IAC = internal auditory canal; MR = magnetic resonance; VS = vestibular schwannoma.

Article Information

Address correspondence to: Nicolas Massager, M.D., Gamma Knife Center, University Hospital Erasme, Route de Lennik 808, B-1070 Brussels, Belgium. email: nmassage@ulb.ac.be.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Axial CT scans (left), T1-weighted MR images after Gd (gad) administration (center), and T2-weighted MR images (right), showing the volume of the cochlea (Cochl; red line) drawn on the treatment plan. The blue line indicates tumor volume; yellow lines represent the 12-Gy isodose line; and the green lines indicate 8-, 5-, and 3-Gy isodose lines covering the cochlear volume.

  • View in gallery

    Dose–volume histograms of the cochlea for patients with hearing preservation and worsening of hearing after GKS. The cochlear volume of patients with audiological worsening after radiosurgery received a higher radiation dose than the dose received by the equivalent volume of the cochlea for patients with no hearing worsening.

  • View in gallery

    Scatterplot showing the statistical correlation between the mean radiation dose received by the cochlear volume and the integrated radiation dose to the intracanalicular part of the tumor.

  • View in gallery

    Graph showing the correlation between the percentage of filling of the VS into the IAC, the hearing outcome, and the mean radiation dose to the cochlea.

References

  • 1

    Delbrouck CHassid SMassager NChoufani GDavid PDevriendt D: Preservation of hearing in vestibular schwannomas treated by radiosurgery using Leksell Gamma Knife: preliminary report of a prospective Belgian clinical study. Acta Otorhinolaryngol Belg 57:1972042003

    • Search Google Scholar
    • Export Citation
  • 2

    Ewald JR: Die wirkung des radiums und das labyrinth. Zentralblatt Physiol 19:2972981905

  • 3

    Gabert KRégis JDelsanti CRoche PHFacon FTamura M: [Preserving hearing function after Gamma Knife radiosurgery for unilateral vestibular schwannoma.]. Neurochirurgie 50:3503572004. (Fr)

    • Search Google Scholar
    • Export Citation
  • 4

    Gardner GRobertson JH: Hearing preservation in unilateral acoustic neuroma surgery. Ann Otol Rhinol Laryngol 97:55661988

  • 5

    Levivier MLorenzoni JMassager NRuiz SDevriendt DBrotchi J: Use of the Leksell gamma knife C with automatic positioning system for the treatment of meningioma and vestibular schwannoma. Neurosurg Focus 14:5E82003

    • Search Google Scholar
    • Export Citation
  • 6

    Linksey MEJohnstone PA: Radiation tolerance of normal temporal bone structures: implications for gamma knife stereotactic radiosurgery. Int J Radiat Oncol Biol Phys 57:1962002003

    • Search Google Scholar
    • Export Citation
  • 7

    Linksey MEJohnstone PAO'Leary MGoetsch S: Radiation exposure of normal temporal bone structures during stereotactically guided gamma knife surgery for vestibular schwannomas. J Neurosurg 98:8008062003

    • Search Google Scholar
    • Export Citation
  • 8

    Massager NNissim ODelbrouck CDevriendt DDavid PDesmedt F: Role of intracanalicular volumetric and dosimetric parameters on hearing preservation after vestibular schwannoma radiosurgery. Int J Radiat Oncol Biol Phys 64:133113402006

    • Search Google Scholar
    • Export Citation
  • 9

    Paek SHChung HTJeong SSPark CKKim CYKim JE: Hearing preservation after Gamma Knife stereotactic radiosurgery of vestibular schwannoma. Cancer 104:5805902005

    • Search Google Scholar
    • Export Citation
  • 10

    Régis JLevivier MWikler DPorcheron D: [Dosimetric planning for radiosurgical treatment of vestibular schwannomas.]. Neurochirurgie 50:2893002004. (Fr)

    • Search Google Scholar
    • Export Citation
  • 11

    Snell JWSheehan JStroila MSteiner L: Assessment of imaging studies used with radiosurgery: a volumetric algorithm and an estimation of its error. Technical Note. J Neurosurg 104:1571622006

    • Search Google Scholar
    • Export Citation

TrendMD

Cited By

Metrics

Metrics

All Time Past Year Past 30 Days
Abstract Views 263 263 16
Full Text Views 119 119 4
PDF Downloads 42 42 1
EPUB Downloads 0 0 0

PubMed

Google Scholar