[Optimization of microsurgical operation technique to insert auditory brainstem implants, taking into account the results of a morphometric study].
BACKGROUND
The surgical placement of auditory brainstem implants to stimulate the cochlear nuclear region in patients with acquired bilateral retrocochlear deafness allows limited restitution of hearing. However, there have been few studies on the topographical relations in the target region, particularly the floor of the IVth ventricle.


OBJECTIVE
Is it possible to obtain more precise anatomical data in order to improve the surgical approaches and techniques for the placement of auditory brainstem implants? AIMS. To obtain a more precise topo- anatomical orientation in the target region for microsurgical lateral and midline approaches or a stereotactic operative strategy.


RESULTS
Landmarks for the placement of an auditory brainstem implant via the IVth ventricle were examined and measured in a series of formalin-fixed human brainstems ( n=28). These data, and knowledge of their variability, allow a more precise surgical lateral approach. It is essential to precisely localise the target region, as it can only be partly discerned under the microscope during an operation. For this reason, to date its precise localisation has been determined only electrophysiologically.


CONCLUSIONS
Exact target localisation improves safety. From an anatomical point of view the midline approach gives the chance to enlarge the indication spectrum for an implant. The anatomical data obtained here could also be integrated into a stereotactic surgical strategy.
Zentrum für Neurochirurgie, Klinikum der Universität zu Köln, Seminar für Psychiatrie der Heilpädagogischen Fakultät, Universität zu Köln. ralf.quester@uni-koeln.de
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D000328:Adult; D000368:Aged; D001933:Brain Stem / Q000473:pathology / Q000601:surgery*; D002138:Calibration / Q000592:standards; D002508:Cephalometry / Q000706:statistics & numerical data*; D019929:Cochlear Implantation / Q000379:methods*; D017626:Cochlear Nucleus / Q000473:pathology / Q000601:surgery*; D003638:Deafness / Q000534:rehabilitation; D004567:Electrodes, Implanted; D005260:Female; D006801:Humans; D008297:Male; D008866:Microsurgery / Q000706:statistics & numerical data; D008875:Middle Aged; D009929:Organ Size / Q000502:physiology; D012016:Reference Values; D013238:Stereotaxic Techniques / Q000706:statistics & numerical data*