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Background: Catheterization of narrow ventricles may prove difficult resulting in misplacement or inefficient trials with potential damage to brain tissue., Material and Methods: The application of a new module for navigated ventricular catheterization using flexible electromagnetic navigation and a dynamic reference frame is presented., Results: Navigated catheter placement was successful and accurate in a pilot study. Electromagnetic interferences had to be taken into consideration., Conclusion: Flexible electromagnetic navigation with a dynamic reference frame is a useful tool for catheter placement as it reduces the risk of misplacement or repeated catheterization trials., (Copyright (c) 2007 S. Karger AG, Basel.)

Hypothesis: The lateral suboccipital approach is a well-established route for safe removal of vestibular schwannomas in neurofibromatosis Type 2 (NF2) patients. The goal of this study was to assess if this approach can be extended to a lateral supracerebellar infratentorial approach to enable insertion of an auditory midbrain implant (AMI) penetrating array along the tonotopic gradient of the inferior colliculus central nucleus (ICC)., Background: The AMI is a new auditory prosthesis designed for penetrating stimulation of the ICC in patients with neural deafness. The initial candidates are NF2 patients who, because of the growth and/or surgical removal of bilateral acoustic neuromas, develop neural deafness and are unable to benefit from cochlear implants. The ideal surgical approach in NF2 patients must first enable safe removal of vestibular schwannomas and then provide sufficient exposure of the midbrain for AMI implantation., Methods: This study was performed on formalin-fixed and fresh cadaver specimens. Computed tomography scan and magnetic resonance imaging were used to study the heads of the specimens and for surgical navigation., Results: The lateral suboccipital craniotomy enabled sufficient exposure of the cerebellopontine angle and internal auditory canal for tumor removal. It could then be extended to a lateral supracerebellar infratentorial approach that provided good exposure of the dorsolateral aspect of the tentorial hiatus and mesencephalon for implantation of the AMI along the tonotopic gradient of the ICC. This approach did not endanger the trochlear nerve or any major midline venous structures in the quadrigeminal cistern., Conclusion: This modified lateral suboccipital approach ensures safe removal of large vestibular schwannomas and provides sufficient exposure of the inferior colliculus for ideal AMI implantation.

Objectives: Three-dimensional computed tomography (3D-CT) of facial fractures has been reported as beneficial using surface (SR) and volume rendering (VR). There are controversial statements concerning the preferable algorithm. The purpose of this study was to evaluate and compare SR and VR for clinical 3D-CT in facial fractures on an experimental basis., Methods: Multislice CT was obtained in 22 patients with facial fractures using two data acquisition protocols. Five SR and VR post-processing protocols were applied. Five assessors independently evaluated the quality of visualization of the fracture gap and dislocated fragments as well as the overall image quality using a five-point rating scale. The potential benefit of the 3D-images for radiological diagnosis and presentation was evaluated. The influence of the data acquisition protocol was analysed., Results: SR in general achieved better evaluation scores than VR at corresponding thresholds. Variation of evaluation scores for all criteria was found for SR and VR depending on the segmentation threshold. Apart from the overall image quality no significant influence of the data acquisition technique was found for the evaluated criteria., Conclusions: SR provided sufficient and time efficient means for 3D-visualization of facial fractures in this study. No diagnostic benefit of VR over SR was found.

A 37-year-old female presented for surgery with central perforation of the eardrum with granulation. Mastoidectomy had been performed 18 years ago following chronic mastoiditis. As the clinical picture now suggested a suspected cholesteatoma, radiological imaging was performed. The CT scan revealed specification of the mastoid and the tympanic cavity. In addition, MRI scan showed signal enhancement in the same areas. However, the suspected cholesteatoma could not be confirmed intraoperatively. Pathohistology revealed a ceruminal gland adenoma. They are a rare phenomenon and should be distinguished from middle ear adenomas, pleomorph ceruminal gland adenomas, ceruminal gland adenocarcinomas and cylindromas of the ceruminal glands. Owing to a high recurrence rate, complete surgical removal is necessary. Despite its rare occurrence, a ceruminal gland adenoma must be taken into consideration in the differential diagnosis of individual cholesteatoma cases.

Few of the pioneering manufacturers who attempted to develop navigation systems have been able to establish themselves within the market long-term. The same applies to the technological basis of these systems which aid intraoperative anatomical orientation. The first few systems registered the mechanical displacement of the navigational instrument's axes. Optoelectronic and electromagnetic methods are now prevalent. In contrast to electromagnetic systems, the "line of sight" between the camera system, the reference markers placed on the patient's head and the navigation instruments must remain unobstructed during the navigation process when using electrooptical navigation systems. Whereas, in the past, only preoperative CT scans were used for navigation, the integration of MRI and sonography--whose images can now be fused with each other and with those provided by other intraoperative imaging techniques such as fluoroscopy and endosonography--has become increasingly popular. Navigation systems require input of information about spatial conditions. This is carried out via procedures of registration and referencing, by means of which the relative position of reference markers at the head of the patient is correlated with the image data. The equipment is calibrated in the same way. Headsets, headbands and bone-anchored adapters are available for the fixation of the markers in the patient's head. Whereas the use of a headband or headset requires considerably less time, bone-anchored referencing increases the precision of the navigation system. The surgeon must be able to manage the different methods. In order to reduce the time required for preoperative preparation and to enhance the handling of the navigation processor for the surgeon, it is essential to have a clear menu. The surgeon is able to plan the steps involved in the surgery using the processor, define the access to the surgical site and control the surgery intraoperatively. Preoperative segmentation of functionally and clinically relevant structures enables minimally invasive surgery to be carried out, such as procedures with the aim of acquiring biopsy tissue and the search for foreign bodies. Following the technical development of the systems, the manufacturers are endeavouring to simplify their handling in close coordination with the users. The next step has to be the clinical evaluation of the navigation systems in accordance with the EBM standard, in order to establish this assistive method as routine clinical practice while applying meaningful medical criteria.