Search

According to the WHO grading system, myxopapillary ependymomas are assigned to WHO Grade I. However, the clinico-pathological spectrum might be very heterogenous. Herein, we report 4 cases exhibiting lumbar tumor masses, 1 causing muscular atrophy over a 30-year period, 3 displaying clinical history of persisting lumbar pain for only several weeks. All tumors were crooked with dura and spinal roots resulting in incomplete resection in three cases. On histological examination, two tumors were almost acellular and showed polycyclic hyaline and fibrotic extracellular matrix leading to differential diagnoses of chordoma, meningioma, fibrolipoma and ependymoma. Finally, together with the immunohistochemical investigations, electron microscopy led to the diagnosis of myxopapillary ependymoma, WHO Grade I, with massive degenerative changes. The other 2 cases presented with the typical neuropathology of myxopapillary ependymomas but showed local recurrence within 1 and 13 years throughout the whole neuraxis, and in 1 case additional metastases of the 3rd ventricle. Although the morphological feature of these myxopapillary ependymomas was benign, the presented cases showed that the biological behavior of myxopapillary tumors might differ greatly and that these tumors present a serious operative and diagnostic challenge. Myxopapillary ependymomas occur most often in the lumbosacral region. Due to the anatomic complexity of the cauda equina, a complete resection can be technically challenging in this region. However, a gross total resection at the primary surgery is the most predictive factor for the outcome.

Inflammatory myofibroblastic tumors with involvement of cranial and peripheral nerves are exceedingly rare. The authors present the case of a 67-year-old man with an inflammatory myofibroblastic tumor of the left ulnar nerve, which was identified intraoperatively and mimicked a malignant neoplastic lesion. Histopathological examination revealed loosely structured fibrous tissue and collagen deposits intermingled with patchy infiltrates of lymphocytes, plasma cells, and histiocytes penetrating the endo- and epineurium of the affected nerve fascicles. There was strong expression of vimentin and actin in spindle cells throughout the lesion. The histiocytes were CD68- and major histocompatibility complex class II-positive, but lacked CD1a expression. A review of the literature revealed nine histopathologically confirmed cases of inflammatory myofibroblastic tumors involving peripheral or cranial nerves in which slight differences in histopathological features and surgical management were found, which are discussed here.

Introduction: Lesions involving the posterior and middle fossa may be reached by several surgical approaches depending mostly on tumors' location and characteristics. The retrosigmoid intradural suprameatal approach has been used to remove tumors of the posterior fossa extending into Meckel's cave and the middle fossa. With large tumors, this approach may allow exposure of the oculomotor and optic nerves, the supraclinoid internal carotid and communicating posterior arteries., Methods: Three formaldehyde-fixed specimens have been prepared on both sides using the conventional retrosigmoidal-suprameatal approach. The entire endoscopic preparations have been documented via a digital recording system, using a 5mm endoscope with a 25 degrees perspective. The authors describe the anatomical corridor and technique of the endoscope-assisted retrosigmoid intradural suprameatal approach to lesions that are located predominantly within the posterior fossa and supratentorial extension into Meckel's cave, sellar and parasellar region., Conclusions: The endoscope-assisted suprameatal approach provides exposure of the antero-medial middle fossa even in cases of skull base lesions that have not caused significant displacement of neurovascular structures.

Objective: Resection of large intraosseous sphenoid wing meningiomas is traditionally associated with significant morbidity. Rapid prototyping techniques have become widely used for treatment planning. Yet, the transfer of a treatment plan into the intraoperative situs strongly depends on the experience of the individual surgeon., Clinical Presentation: Extensive resection with orbital decompression was planned and performed on the basis of rapid prototyping and surgical navigation techniques in a 44-year-old woman presenting with a large sphenoid wing meningioma on the right infiltrating the orbit., Results: Tumor resection was simulated on a stereolithography model of the patient's head. The stereolithography model was scanned using computed tomography (CT) and the defect geometry was used to create a custom-made titanium implant. The implant consisted of a solid titanium core and a spot-welded titanium mesh surrounding the core, allowing for minor intraoperative adjustments of the implant size by reducing the mesh size. The stereolithography model with the incorporated implant was CT scanned again and the CT data were fused with the patient's original CT data. The implant borders indicating the resection borders were marked within the patient's CT data set. This treatment plan was transferred to an optical navigation system. Intraoperatively, tumor resection was performed using surgical navigation., Conclusion: In the presented case report, the combination of computer-assisted planning using rapid prototyping techniques and image-guided surgery allowed for an extensive tumor resection precisely according to a preoperative treatment plan in a patient presenting with a large intraosseous sphenoid wing meningioma. A larger clinical series with a long-term follow-up period will be needed to determine the reproducibility.

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.)

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.

Objective: The importance of preserving the superior petrosal vein has received increasing attention in the surgical treatment of pathologies involving the petrous apex. Recent reports have associated postoperative auditory nerve dysfunction with petrosal vein sacrifice. However, there is no systematic clinical study available thus far focusing on the postoperative auditory function after petrosal vein obliteration., Methods: In 55 patients with meningiomas involving the petrous apex, pre- and intraoperative findings including petrosal vein sectioning were analyzed retrospectively concerning their impact on postoperative auditory function., Results: The petrosal vein was preserved in 26 (47%) cases. In 27 (49%) cases, this vein was not preserved. Hearing loss occurred in 11% of all cases. In the preserved-vein group, postoperative hearing loss occurred in 3 of 26 (11%) cases and in the sacrificed-vein group in 3 of 27 (11%) cases., Conclusion: Sacrifice of the petrosal vein during surgery of petrous apex meningiomas seems not to have an impact on postoperative auditory function.

Object: Surgical manipulation of the fifth cranial nerve during its intra- or extracranial course may lead to bradycardia or even asystole as well as arterial hypotension, a phenomenon described as the trigeminocardiac reflex (TCR). The authors studied the impact of this reflex on postoperative auditory function in patients undergoing vestibular schwannoma (VS) surgery., Methods: One hundred patients scheduled for VS surgery were studied prospectively for parameters influencing the postoperative auditory function. The evaluation included sex, age, pre- and postoperative auditory function, preoperative mean arterial blood pressure, preoperative medical diseases or medication (for example, antiarrhythmia drugs), tumor size and localization, and the intraoperative occurrence of the TCR. The TCR, which occurred in 11% of the patients, influenced the postoperative hearing function in the patients with Hannover Class T3 and T4 VSs. With an overall hearing preservation of 47%, 11.1% of the patients in the TCR group and 51.4% of those in the non-TCR group experienced preserved hearing function postoperatively. In cases involving larger tumors (Hannover Class T3 and T4), an intraoperative TCR was associated with a significantly worse postoperative hearing function during VS surgery (p = 0.005)., Conclusions: The hypotension following TCR is a negative prognostic factor for hearing preservation in patients undergoing VS surgery. Patients' knowledge of this can be increased pre- and postoperatively. Further study of this phenomenon will advance the understanding of the underlying mechanisms and may help to improve hearing preservation by controlling the occurrence of the TCR.

Objective: Nausea and dizziness are very discomforting for patients after vestibular schwannoma surgery and they impair recovery., Methods: To identify preoperative symptoms and conditions that increase the risk of development of nausea after vestibular schwannoma surgery, a multivariate analysis was performed. One hundred fifteen patients with vestibular schwannoma had a microsurgical tumor removal in a standardized procedure in 2001 and 2002. Eighteen patients were excluded from the study because of previous surgery (recurrent tumors, 7 patients) or bilateral tumor occurrence (neurofibromatosis, 11 patients). Analysis was performed regarding postoperative amount of antiemetic medication, vomiting, and subjective feeling of the patient. Tumor grading, body mass index, sex, previous complaints, examination at admission, and side of the tumor were taken in consideration., Results: Women had significant longer postoperative complaints (mean, 3.0 d; standard error, 0.47) and needed longer antiemetic therapy (mean, 3.3 d; standard error, 0.49) than men (mean, 1.72 d; standard error, 0.21). Patients developing no significant postoperative complaints were all in the higher tumor grading group, Grades 3a, 4a, and 4b. There was a significant difference in the duration of antiemetic therapy between tumors graded 1 and tumors graded 3 or 4. Patients with a positive stepping test preoperatively had a tendency to demand less antiemetic medication. Women with small tumors are most likely to develop significant complaints after vestibular schwannoma surgery., Conclusion: It is possible to identify patients with a higher risk of postoperative nausea and dizziness after vestibular schwannoma surgery. This allows one to inform these patients preoperatively and to initiate an early postoperative drug therapy to ease their symptoms.

The FE-modeling of complex anatomical structures is not solved satisfyingly so far. Voxel-based as opposed to contour-based algorithms allow an automated mesh generation based on the image data. Nonetheless their geometric precision is limited. We developed an automated mesh-generator that combines the advantages of voxel-based generation with improved representation of the geometry by displacement of nodes on the object-surface. Models of an artificial 3D-pipe-section and a skullbase were generated with different mesh-densities using the newly developed geometric, unsmoothed and smoothed voxel generators. Compared to the analytic calculation of the 3D-pipe-section model the normalized RMS error of the surface stress was 0.173-0.647 for the unsmoothed voxel models, 0.111-0.616 for the smoothed voxel models with small volume error and 0.126-0.273 for the geometric models. The highest element-energy error as a criterion for the mesh quality was 2.61x10(-2) N mm, 2.46x10(-2) N mm and 1.81x10(-2) N mm for unsmoothed, smoothed and geometric voxel models, respectively. The geometric model of the 3D-skullbase resulted in the lowest element-energy error and volume error. This algorithm also allowed the best representation of anatomical details. The presented geometric mesh-generator is universally applicable and allows an automated and accurate modeling by combining the advantages of the voxel-technique and of improved surface-modeling.

Introduction: 3-Tesla (T) magnetic resonance imaging (MRI) offers high resolution imaging with improved signal quality. It also allows for improved functional investigations, most prominently with respect to fiber tracts and their relation to pathological lesions. Up to now, patients with adjustable shunt systems were not eligible for high field power magnetic resonance imaging. We have evaluated the effects of this technique upon a newly developed adjustable shunt valve., Method: Ten adjustable shunt devices were examined during routine and functional 3-T high field MRI examinations. Pressure settings were checked after 17 examinations each for all valves. There were no changes in pressure setting at all possible levels in any of the tested devices. No problems with the adjusting mechanism were observed during 340 examinations., Conclusion: This new shunt device offers the diagnostic benefit of high field magnetic resonance imaging in shunt-dependent patients who need an adjustable valve. The valve is not affected by higher magnetic field power and does not require readjustment of the pressure settings after MRI examination.

Post-processing of CT-data allows non-invasive 3D-Visualisation of the middle ear for diagnosis and surgical planning. In this study different post-processing techniques and the clinical application of a 3D-postprocessing algorithm in a large number of patients are presented. 20 normal patients, 6 dissected temporal bones and 213 patients with suspected middle ear pathology were examined using a low-dosage Multi-Slice CT protocol. Virtual endoscopic views of the middle ear and 3D-images of the ossicles were generated using a standardised algorithm. Evaluation of the image quality was performed. The virtual views of the dissected temporal bones were compared to real views. In 32 patients high-quality 3D-models of the individual anatomical structures were generated and displayed using different visualisation techniques. The standardised and evaluated method enabled visualisation of the normal middle ear anatomy. Assessment of different pathologies, especially malformation, trauma, implants and postoperative alterations, was facilitated. The high-quality 3D-models allowed precise imaging of the anatomical structures. 3D-Visualisation of the middle ear using CT-data is beneficial for radiological diagnosis and surgical planning in cases of complex middle ear pathology as a complementary examination technique.

For imaging purposes of the spine, segmented image data provides the basis for a variety of modern clinical applications. However, the anatomical complex structure of the spine as well as the extensive degenerative bony deformations apparent in the clinical situation, generally complicate the application of a fully automated segmentation. To serve the special needs for image segmentation of the spine anatomy a newly developed software system is presented, that implements specially adapted interactive tools, taking its 'axis'-skeletal structure into account. A standardized protocol combines the newly developed interactive tools (rotation transformation, warped dissection plane) with standard segmentation tools to provide both a fast and accurate segmentation procedure. The introduced software environment has been valuable for the segmentation of cervical, thoracic and lumbar spines segments based on clinical routine and research images.

Fusion of medical images is a technique that permits the correlation of homologous anatomical structures in different imaging modalities on the basis of a spatial transformation of the data sets. CT and MRI of the spine provide complementary information of possible relevance for diagnostic and therapeutic decisions. Methods enabling a multisegmental CT-MRI fusion of the spine were developed. These solve the problem of altered spatial relationships of the individual anatomical structures due to differing patient positioning in successive data acquisitions. Routine clinical CT and MRI data of a thoracic section of the spine were obtained and transferred to a PC-workstation. Following segmentation of the CT-data, landmarks for each individual vertebra were defined in the CT and MRI data. For each individual vertebra the algorithm we developed then carried out a rigid registration of the CT information to the MR data. The fused data sets were presented as colour-coded images or on the basis of dynamic variation of transparency. To assess registration precision, fiducial registration errors (FRE) and target registration errors (TRE) were calculated. The algorithm permitted multi-segmental image fusion of the spine. The average time required for defining the landmarks was 22 seconds per landmark for CT, and 34 seconds per landmark for MR. The average FRE was 1.53 mm. The TRE for the vertebrae was less than 2 mm. The colour-coded images were particularly suitable for assessing the contours of the anatomical structures, whereas dynamic variation of the transparency of overlapping CT images enabled a better overall assessment of the spatial relationship of the anatomical structures. The algorithm permits precise multi-segmental fusion of CT and MR of the spine, which was not possible using current fusion-algorithms due to variations in the spatial orientation of the anatomical structures caused by different positioning of the axial skeleton in successive examinations.

Digital images generated by medical imaging form the basis for radiological diagnosis and surgical planning. Despite the advent of the DICOM 3.0 standard for medical image communication, widespread application of the existing information is often limited by incompatibility of the data formatting used by different equipment generations, and the manufacturer-specific standards employed. An exchange interface based on magneto optical discs has been developed to retrieve and present medical image data regardless of the technological hardware and the specific formats used. Specially adapted routines to retrieve the data first had to be developed. A modular program structure was used to allow flexibility in the implementation of further routines and other exchange media. Over 20,000 CT and MRI images including header information obtained from different General Electric and Siemens scanners were extracted successfully from MO discs. The image data were used for follow up and surgical planning and were transferred to a PAC-server. The interface proved reliable and easy to use. Support for further proprietary formats is currently being developed. The present exchange interface permits reliable retrieval of digital images for diagnostic and surgical planning purposes, regardless of the hardware generation and manufacturer-specific formats.

Segmented 3-D data of the spine form the basis for various modern clinical applications. Among these, multisegmental image fusion, image registration and finite element modeling for biomechanical analysis are promising innovative tools capable of facilitating treatment decisions and optimization of individual therapy in the future. However, the complex anatomy of the spine and the often extensive degenerative deformation presenting in clinical practice, generally limit the application of fully automated segmentation. A newly developed software system is presented that meets the complex requirements for image segmentation of the spine through the use of specially adapted interactive tools that take account of its axial skeletal structure. Furthermore, a standardized protocol is introduced that combines the newly developed interactive tools (rotation transformation, warped dissection plane) and standard segmentation tools to permit rapid and accurate segmentation. To date, the software environment presented herein has been applied with success to the segmentation of cervical, thoracic and lumbar spine.

Background: Although prejudice may not be verbal in nature, the lack of response from professional and non-professional medical personnel regarding the obese patients' needs (medical equipment, comfortable surroundings, properly fitting attire, etc.), leads one to assume that obese patients continue to be a target of unfavorable opinion., Methods: 200 patients from four busy east coast bariatric practices received detailed surveys requesting information regarding experiences incurred during the entire peri-operative period. The responses were blinded as to patient or site of surgery. Patients were questioned about attitudes of primary care and consulting physicians and staff, all hospital and outpatient departments, and patient care areas within the hospital. The appropriateness of equipment was also questioned., Results: There were 40 respondents aged 44.7 years (range 21-61 years); 34 were women. Average preoperative weight was 145 kg (range 101.8-231.8 kg). Average weight loss at time of survey was 42.8 kg; average time after surgery was 9.5 months. Responses concerning physician attitudes were similar through all patient groups. There was no difference in degree of discrimination felt by the lightest or the heaviest of the morbidly obese. 7 patients (17%) changed primary care physicians due to a perceived indifference, lack of concern, or negative attitude toward bariatric surgery. The procedure-oriented physicians (orthopedic surgeons and gastroenterologists) were most supportive, while social workers and psychologists scored lowest. Most hospital departments treated patients well, except those with equipment that may be affected by increased patient weight (e.g. treadmills and x-ray tables)., Conclusion: Patients undergoing bariatric surgery continue to feel misunderstood and mistreated by medical and non-medical personnel involved in the treatment of their obesity. Like other forms of prejudice, this most likely is due to a lack of understanding of the disease of morbid obesity, the root causes and the medical consequences if untreated. Despite laws designed to prevent discrimination based on appearance, unfavorable attitudes and practices persist. A plan for continued education of the medical and non-medical communities is essential to breakdown the barriers in place due to ignorance and indifference. Patient support groups continue to play an important role in the ongoing battle to correct the negative effect of these attitudes on the morbidly obese patient.

Objective: We investigated the usefulness of a microscope-based navigational system (Multi Koordinaten Manipulator; Zeiss, Oberkochen, Germany) for removal of the posterior wall of the internal auditory canal (IAC) via the retrosigmoid route., Methods: A cadaveric study was performed to assess the navigational localization error for the retrosigmoid approach to the IAC. Computed tomographic findings for 47 acoustic neuroma cases were divided into three groups, on the basis of the relationship between the labyrinth and the sigmoid-fundus line (medial, on the line, or lateral). Furthermore, the shortest distances between the most medial labyrinthine extension and the resection line were measured. In 20 acoustic neuroma operations, the different features and the practicality of the microscope-based navigational system for opening of the IAC were evaluated., Results: The mean anatomic localization errors were 0.67 +/- 0.2 mm (95th percentile, 1.32 mm) for navigation to the IAC and 0.71 +/- 0.37 mm (95th percentile, 1.68 mm) for navigation to the posterior semicircular canal. The average distances between the most medial labyrinthine extension and the resection line were 3.65, 3.36, and 2.0 mm for the lateral, on-the-line, and medial groups, respectively. Direct contouring of structures at risk does not take into account the localization error, nor does it provide reliable navigational information. A novel indirect contouring concept that takes into account the localization error (the safety corridor method) was therefore introduced., Conclusion: The value of navigational assistance for opening of the IAC is promising but still limited. Further development is required before the clinical effects of this navigational approach can be evaluated.

Digital images are the ever-growing basis of modern medical imaging and treatment. Despite the advent of the DICOM 3.0 standard for medical image communication it still requires cumbersome efforts to export images from imaging modalities to other computer systems. This is true especially for smaller institutions, which often have limited resources for standardized image transfer. To gain access even to these data we developed an exchange interface on the basis of magneto-optical discs (MO-discs), as they are usually available in most of the imaging modalities in use today. Unfortunately images on MO-discs are usually stored in formats specific for each manufacturer. Therefore special routines to access the data on MO-discs had to be developed for each company or even each scanner. Over 10,000 CT and MRI images including their header information from different General Electric and Siemens scanners were extracted successfully from MO-discs. The interface proved to be reliable and easy to handle by technicians. Support of additional manufacturers and of the DICOM 3.0 standard are work in progress.

The purpose of this study was to investigate experimentally, factors determining the navigation accuracy of the MKM navigation system by Zeiss. The MKM consists of an operating microscope mounted to a six-axis motor-driven robot arm and an alpha-workstation. The image-guided surgery device provides navigation information based on calculation of the cartesian coordinates of the robot arm, and coordinates of the focus point assessed by laser assisted measurement. Navigation information (current position, direction and distance to a previously selected target) is optically projected into the microscopic field. Following factors were examined in an experimental setting for their impact on accuracy of the MKM: optical system, mechanical precision of the robot arm, and registration procedure. The robot arm and the optical system of the microscope allow high precision measurements of any focus point (error < 2 mm if the following aspects are considered: the use of auto-focus function instead of manual focusing, positioning of the registration points as a square or a triangle focus point should be selected on a surface that is perpendicular to the optical axis.

Introduction: A cadaveric study was undertaken to investigate the usefulness and reliability of a microscope based navigation system (NS) for skull base surgery., Material and Methods: CT-scans (1 mm slices) were performed in 10 fixed cadaver heads after implantation of fiducials. There upon, various skull base dissections were undertaken: transethmoidal-transsphenoidal approach to sella and clivus, retrosigmoidal approach to the internal auditory canal (IAC) and to the posterior semicircular canal (PSCC). The navigated dissections were performed with the MKM, a microscope based navigation system of Carl Zeiss (Oberkochen, Germany)., Results: The registration assessment by the NS yielded a mean deviation of 0.23 mm +/- 0.03 mm (mean +/- SD, n = 7, range 0.19 to 0.27 mm). The real anatomical deviation during dissection was 0.67 mm +/- 0.2 mm for navigation to the IAC and 0.71 mm +/- 0.37 mm to the PSCC. This accuracy was achieved with three fiducials (4 x 1 mm titanium screws) arranged as a triangle (side length 4-6 cm) nearby the surgical field. Navigation data on current position, direction and distance to a target structure were helpful in the transethmoidal-transsphenoidal approach to the clivus, as well as for accessing deep seated structures (C1-C2 junction, petrous bone tip). The contouring feature was beneficial for identifying structures embedded in the bone. However, due to inaccurate 3-D modelling this feature has a restricted reliability., Discussion: Our cadaveric skull base study has shown that the MKM is a reliable tool with high anatomical accuracy and usefulness of most navigation features. However, in order to effectively and reliably use any NS the surgeon must be familiar with its potential features and limitations as is demonstrated in this study.

The extremely irregular geometry of bones makes it very difficult to develop and preprocess three-dimensional finite element models (FEM). In the field of biomechanics, the finite element simulation method is a research tool of increasing importance for the prediction of stresses and the stress-compatibility testing of endoprostheses. With this in mind, a FEM preprocessor was developed with the aim of creating three dimensional models of human femurs. On the basis of postprocessed computed tomography data, this preprocessor makes possible rapid, flexible and regular cross-linking. "Brick" elements are used, which are of advantage in terms of computing time, accuracy and computer storage requirements. The software simplifies the generation of models and facilitates the investigation of individual variations, thus providing the basis for utilizing the method in the clinical setting.