gms | German Medical Science

59th Annual Meeting of the German Society of Neurosurgery (DGNC)
3rd Joint Meeting with the Italian Neurosurgical Society (SINch)

German Society of Neurosurgery (DGNC)

1 - 4 June 2008, Würzburg

Approaches to the inferior colliculus for auditory midbrain implant: an anatomical study

Zugänge zum Coilliculus inferior für das auditorische Mittelhirnimplant: eine anatomische Studie

Meeting Abstract

  • corresponding author C. Herbold - Neurochirurgische Klinik und Poliklinik, Universitätsklinikum Würzburg
  • J. Coburger - Neurochirurgische Klinik und Poliklinik, Universitätsklinikum Würzburg
  • G. Vince - Neurochirurgische Klinik und Poliklinik, Universitätsklinikum Würzburg
  • D. Drenckhahn - Institut für Anatomie und Zellbiologie, Universitätsklinikum Würzburg
  • K. Roosen - Neurochirurgische Klinik und Poliklinik, Universitätsklinikum Würzburg
  • C. Matthies - Neurochirurgische Klinik und Poliklinik, Universitätsklinikum Würzburg

Deutsche Gesellschaft für Neurochirurgie. Società Italiana di Neurochirurgia. 59. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e.V. (DGNC), 3. Joint Meeting mit der Italienischen Gesellschaft für Neurochirurgie (SINch). Würzburg, 01.-04.06.2008. Düsseldorf: German Medical Science GMS Publishing House; 2008. DocP 103

The electronic version of this article is the complete one and can be found online at:

Published: May 30, 2008

© 2008 Herbold et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: The inferior colliculus (IC) of the midbrain is currently discussed to be the more useful target for an auditory prosthesis than the cochlear nucleus. Furthermore, in case of cochlear nucleus degeneration, an auditory midbrain implant (AMI) may constitute the only option to regain some hearing in bilateral retrocochlear deafness An anatomical study was designed on the advantages and pitfalls of a lateral versus a midline approach to the IC.

Methods: On 5 formalin-fixed cadaver specimens surgical exposure was performed using either the lateral suboccipital (SO) approach or the midline (ML) approach. Computed tomography scan and magnetic resonance imaging were used for neuronavigation. Parameters of evaluation were anatomical structures endangered by either approach, feasibility of sufficient exposure and depth to the surgical target as well as its vascular supply.

Results: Regarding the approaches, the transverse sinus was on average exposed by 5.8mm in order to achieve a good viewing angle along the cerebellar surface. There was a lower number of bridging veins to be ligated via the ML (1 vein) versus SO approach (2 to 3 veins); especially at the latter the necessary ligation of petrosal veins appeared more critical. The ML approach necessitated more dissection of arachnoid from midline arterial vessels. The lateral suboccipital craniotomy enabled sufficient exposure of the CPA and of the ipslateral IC; also the midline and a part of the contralateral IC were accessible. The ML approach provided a wider survey and access to both IC. At either approach adequate and safe identification of the trochlear nerve was possible; exposure was performed at a length of 30mm from the IC along the tentorium. The depth from the transverse sinus to the IC was identical by either approach (54mm). Mobilization of small vessels of the IC for placing an AMI was necessary in all cases and identical in either approach.

Conclusions: Depending on the individual patient conditions both approaches (SO; ML) are suitable for surface AMI implantation. Combined tumor and implant surgery may be attempted at a uniform SO approach. If severe scarring must be anticipated due to previous surgery or radiation, a midline approach might be advantageous. Furthermore, in marked sinus asymmetry with suspected dominance of petrosal veins and sigmoid sinus on one side, a ML or contralateral approach should be considered. Regarding the length of the electrode cable, different to expectations, distances to the IC were identical by both approaches.