Skip to main content


Log in

Iatrogenic inner ear dehiscence associated with lateral skull base surgery: a systematic analysis of drilling injuries and their causal factors

  • Original Article
  • Published:
Acta Neurochirurgica Aims and scope Submit manuscript



Drilling injuries of the inner ear are an underreported complication of lateral skull base (LSB) surgery. Inner ear breaches can cause hearing loss, vestibular dysfunction, and third window phenomenon. This study aims to elucidate primary factors causing iatrogenic inner ear dehiscences (IED) in 9 patients who presented to a tertiary care center with postoperative symptoms of IED following LSB surgery for vestibular schwannoma, endolymphatic sac tumor, Meniere’s disease, paraganglioma jugulare, and vagal schwannoma.


Utilizing 3D Slicer image processing software, geometric and volumetric analysis was applied to both preoperative and postoperative imaging to identify causal factors iatrogenic inner ear breaches. Segmentation analyses, craniotomy analyses, and drilling trajectory analyses were performed. Cases of retrosigmoid approaches for vestibular schwannoma resection were compared to matched controls.


Excessive lateral drilling and breach of a single inner ear structure occurred in 3 cases undergoing transjugular (n=2) and transmastoid (n=1) approaches. Inadequate drilling trajectory breaching ≥1 inner ear structure occurred in 6 cases undergoing retrosigmoid (n=4), transmastoid (n=1), and middle cranial fossa approaches (n=1). In retrosigmoid approaches the 2-cm visualization window and craniotomy limits did not provide drilling angles to the entire tumor without causing IED in comparison to matched controls.


Inappropriate drill depth, errant lateral drilling, inadequate drill trajectory, or a combination of these led to iatrogenic IED. Image-based segmentation, individualized 3D anatomical model generation, and geometric and volumetric analyses can optimize operative plans and possibly reduce inner ear breaches from lateral skull base surgery.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2
Fig. 3

Similar content being viewed by others



Three dimensional


Computed tomography


Cerebellopontine angle


Endolymphatic sac


Health Insurance Portability and Accountability Act


Internal auditory canal


Iatrogenic inner ear dehiscence


Lateral skull base


Lateral semicircular canal


Magnetic resonance imaging


Posterior semicircular canal


Superior semicircular canal


Sigmoid sinus


Target registration error


Vestibular schwannoma


  1. Ansari SF, Terry C, Cohen-Gadol AA (2012) Surgery for vestibular schwannomas: a systematic review of complications by approach. Neurosurg Focus 33:E14

    Article  PubMed  Google Scholar 

  2. Bartholomew RA, Poe D, Dunn IF, Smith TR, Corrales CE (2019) Iatrogenic inner ear dehiscence after lateral skull base surgery: therapeutic dilemma and treatment options. Otol Neurotol 40:e399–e404

    Article  PubMed  Google Scholar 

  3. Blevins NH, Jackler RK (1994) Exposure of the lateral extremity of the internal auditory canal through the retrosigmoid approach: a radioanatomic study. Otolaryngol–Head Neck Surg 111:81–90

    Article  CAS  PubMed  Google Scholar 

  4. Bloch DC, Oghalai JS, Jackler RK, Osofsky M, Pitts LH (2004) The fate of the tumor remnant after less-than-complete acoustic neuroma resection. Otolaryngol--Head Neck Surg 130:104–112

    Article  PubMed  Google Scholar 

  5. Carlson ML, Van Abel KM, Schmitt WR, Driscoll CL, Neff BA, Lane JI, Link MJ (2011) Nodular enhancement within the internal auditory canal following retrosigmoid vestibular schwannoma resection: a unique radiological pattern. J Neurosurg 115:835–841

    Article  PubMed  Google Scholar 

  6. Cho B, Oka M, Matsumoto N, Ouchida R, Hong J, Hashizume M (2013) Warning navigation system using real-time safe region monitoring for otologic surgery. Int J Comput Assist Radiol Surg 8:395–405

    Article  PubMed  Google Scholar 

  7. Colletti V, Fiorino FG, Sacchetto L (1996) Iatrogenic impairment of hearing during surgery for acoustic neuroma. Skull Base Surg 6:153–161

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  8. Day JD, Kellogg JX, Fukushima T, Giannotta SL (1994) Microsurgical anatomy of the inner surface of the petrous bone: neuroradiological and morphometric analysis as an adjunct to the retrosigmoid transmeatal approach. Neurosurgery 34:1003–1008

    CAS  PubMed  Google Scholar 

  9. Deep NL, Kay-Rivest E, Roland JTJ (2021) Iatrogenic third window after retrosigmoid approach to a vestibular schwannoma managed with cochlear implantation. Otol Neurotol 42:1355–1359

    Article  PubMed  Google Scholar 

  10. El-Kashlan HK, Zeitoun H, Arts HA, Hoff JT, Telian SA (2000) Recurrence of acoustic neuroma after incomplete resection. Otol Neurotol 21:389–392

    CAS  Google Scholar 

  11. Fedorov A, Beichel R, Kalpathy-Cramer J, Finet J, Fillion-Robin J-C, Pujol S, Bauer C, Jennings D, Fennessy F, Sonka M (2012) 3D Slicer as an image computing platform for the Quantitative Imaging Network. Magn Reson Imaging 30:1323–1341

    Article  PubMed  PubMed Central  Google Scholar 

  12. Iversen MM, Rabbitt RD (2020) Biomechanics of third window syndrome. Front Neurol 11:891

    Article  PubMed  PubMed Central  Google Scholar 

  13. Kiumehr S, Mahboubi H, Djalilian HR (2012) Posterior semicircular canal dehiscence following endolymphatic sac surgery. Laryngoscope 122:2079–2081

    Article  PubMed  PubMed Central  Google Scholar 

  14. Krajewski R, Kukwa A (1999) Infratentorial approach to internal acoustic meatus. Skull Base Surg 9:81–85

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  15. Laine T, Johnsson L, Palva T (1990) Surgical anatomy of the internal auditory canal: a temporal bone dissection study. Acta oto-Laryngol 110:78–84

    Article  CAS  Google Scholar 

  16. Low D, Lee CK, Dip LLT, Ng WH, Ang BT, Ng I (2010) Augmented reality neurosurgical planning and navigation for surgical excision of parasagittal, falcine and convexity meningiomas. Br J Neurosurg 24:69–74

    Article  PubMed  Google Scholar 

  17. McJunkin JL, Jiramongkolchai P, Chung W, Southworth M, Durakovic N, Buchman CA, Silva JR (2018) Development of a mixed reality platform for lateral skull base anatomy. Otology & Neurotology: Official Publication of the American Otological Society, American Neurotology Society [and] European Academy of. Otol Neurotol 39:e1137

    Article  PubMed  PubMed Central  Google Scholar 

  18. McKennan KX (1993) Endoscopy of the internal auditory canal during hearing conservation acoustic tumor surgery. Otol Neurotol 14:259–262

    CAS  Google Scholar 

  19. Minor LB, Solomon D, Zinreich JS, Zee DS (1998) Sound-and/or pressure-induced vertigo due to bone dehiscence of the superior semicircular canal. Arch Otolaryngol–Head Neck Surg 124:249–258

    Article  CAS  PubMed  Google Scholar 

  20. Nuño M, Ugiliweneza B, Boakye M, Monfared A (2019) Morbidity of vestibular schwannomas as documented by treating providers. Otol Neurotol 40:e142–e149

    Article  PubMed  Google Scholar 

  21. Pillai P, Sammet S, Ammirati M (2009) Image-guided, endoscopic-assisted drilling and exposure of the whole length of the internal auditory canal and its fundus with preservation of the integrity of the labyrinth using a retrosigmoid approach: a laboratory investigation. Operative. Neurosurgery 65:ons53–ons59

    Google Scholar 

  22. Pluim JP, Maintz JA, Viergever MA (2003) Mutual-information-based registration of medical images: a survey. IEEE Trans Med Imaging 22:986–1004

    Article  PubMed  Google Scholar 

  23. Rhoton AL Jr (2000) The cerebellopontine angle and posterior fossa cranial nerves by the retrosigmoid approach. Neurosurgery 47:S93–S129

    Article  PubMed  Google Scholar 

  24. Tatagiba M, Samii M, Matthies C, El Azm M, Schonmayr R (1992) The significance for postoperative hearing of preserving the labyrinth in acoustic neurinoma surgery. J Neurosurg 77:677–684

    Article  CAS  PubMed  Google Scholar 

  25. Voormolen EH, Woerdeman PA, van Stralen M, Noordmans HJ, Viergever MA, Regli L, van der Sprenkel JWB (2012) Validation of exposure visualization and audible distance emission for navigated temporal bone drilling in phantoms. PLoS One 7:e41262

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  26. Yokoyama T, Uemura K, Ryu H, Hinokuma K, Nishizawa S, Yamamoto S, Endo M, Sugiyama K (1996) Surgical approach to the internal auditory meatus in acoustic neuroma surgery: significance of preoperative high-resolution computed tomography. Neurosurgery 39:965–970

    CAS  PubMed  Google Scholar 

Download references


This work was supported in part by the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health through Grant Numbers R01EB025964 and P41EB015898 (JJ). This work was also supported in part by the National Institutes of Health Institutional National Research Award, T32 #5T32DC000040 (NB).

Author information

Authors and Affiliations



All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by NBS. The first draft of the manuscript was written NBS, and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Carleton Eduardo Corrales.

Ethics declarations

Ethics approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the Brigham and Women’s Hospital Institutional Review Board (No. 2017P002162).

Competing interests

Unrelated to this publication, Jagadeesan Jayender owns equity in Navigation Sciences, Inc. He is a co-inventor of a navigation device to assist surgeons in tumor excision that is licensed to Navigation Sciences. Dr. Jagadeesan’s interests were reviewed and are managed by BWH and Partners HealthCare in accordance with their conflict of interest policies.

Additional information


The concept of anatomic variability and tailoring surgical approach based upon what is the situation in the individual patient merits emphasis.(1) Our group in 1994 demonstrated this concept for the retrosigmoid approach by utilizing CT measurements and determination of certain available angles of approach. Our method has stood the test of time. The major difference in applying this concept today lies with our increasing sophistication in imaging and the computing power to manipulate those images. The method demonstrated in this paper for determining the ability to obtain exposure of the fundus via transmeatal bone removal through the retrosigmoid approach represents a useful update. I think it worth stressing the importance of meticulous and thoughtful preoperative planning to optimize outcomes.

John Day

Arkansas, USA

1. Day JD, Kellogg JX, Fukushima T, Giannotta SL (1994) Microsurgical anatomy of the inner surface of the petrous bone: neuroradiological and morphometric analysis as an adjunct to the retrosigmoid transmeatal approach. Neurosurgery 34:1003-1008

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Series of axial images from postoperative CT scrolling from superior to inferior in 3D slicer software. Inner ear structures were segmented from preoperative CT and registered to postoperative CT (TRE=0.649mm) and tumor (light green) was segmented from preoperative MRI and registered to postoperative CT (TRE=0.862mm). The drilling path can be seen as a straight line to the internal auditory canal, and the absence of the bony otic capsule exposes a dehiscent superior semicircular canal (yellow), posterior semicircular canal (pink), and vestibule (blue). Additional structures shown include the lateral semicircular canal (brown) and cochlea (dark green). (MP4 8363 kb)

3D model of the postoperative scene from the surgeon’s perspective. Peering through the restrosigmoid craniotomy, one can see the vestibular schwannoma (green) and the drilling path to the internal auditory canal. Visualization of the posterior semicircular canal (pink) and superior semicircular canal (yellow) is made possible due to the absence of overlying bony otic capsule, which occurred as a result of drilling in order to reach the internal auditory canal. The malleus (magenta) and the incus (blue) can be visualized through the external auditory canal. Inner ear and middle ear structures were segmented from preoperative CT and registered to postoperative CT (TRE=0.649mm) and tumor was segmented from preoperative MRI and registered to postoperative CT (TRE=0.862mm). (MP4 5221 kb)



Standards for Reporting Qualitative Research (SRQR) checklist:

figure a

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Ben-Shlomo, N., Jayender, J., Guenette, J.P. et al. Iatrogenic inner ear dehiscence associated with lateral skull base surgery: a systematic analysis of drilling injuries and their causal factors. Acta Neurochir 165, 2969–2977 (2023).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: