Intracranial Pressure-Guided Shunt Valve Adjustments with the Miethke Sensor Reservoir.

BACKGROUND: Telemetric intracranial pressure (ICP) monitoring seems to be a promising therapy-supporting option in shunt-treated patients. Benefits become obvious when headaches are unspecific and clinical symptoms cannot be related to possible overdrainage or underdrainage. In this study, we evaluated a new telemetric device to individually adjust shunt valves according to ICP measurements. METHODS: Between December 2015 and November 2016, 25 patients with suspected suboptimal shunt valve settings underwent insertion of a telemetric ICP sensor (Sensor Reservoir; Christoph Miethke, Potsdam, Germany). Over a 1-year period, a total of 183 telemetric ICP measurements and 85 shunt valve adjustments were carried out. Retrospective statistic analyses focused on valve adjustments, ICP values, and clinical outcomes. RESULTS: ICP-guided valve adjustments positively changed the clinical state in 18 out of 25 patients. Clinical improvement over time was associated with significant changes of the valve settings and ICP values. Interestingly, a therapeutically normalized ICP profile was not automatically associated with clinical improvement. CONCLUSIONS: The Sensor Reservoir is an important and valuable tool for shunt-treated patients suffering from drainage-related problems. The possibility to simultaneously recognize and solve shunt problems represents the decisive advantage. Nevertheless, measurements with the Sensor Reservoir did not allow for the determination of default valve settings or universal target ICP values.

Endoscopic Assisted Supraorbital Keyhole Approach or Endoscopic Endonasal Approach in Cases of Tuberculum Sellae Meningioma: Which Surgical Route Should Be Favored?

OBJECTIVE: Keyhole approaches are under investigation for skull base tumor surgery. They are expected to have a low complication rate with the same successful resection rate compared with endoscopic endonasal procedures. In this study, we compare our current series of tuberculum sellae meningiomas resected via an endoscopic endonasal or microsurgical supraorbital keyhole approach. METHODS: Between 2011 and 2016, 16 patients were treated using the supraorbital keyhole procedure and 6 patients received an endoscopic endonasal procedure. Both surgical techniques were analyzed and compared concerning complications, surgical radicality, endocrinologic, and ophthalmologic outcome and recurrences in patients' follow-up. RESULTS: The 2 different approaches yielded similar rates of gross total resection (endonasal 83% [5 of 6] vs. supraorbital 87% [14 of 16]), near total resection (17% [1 of 6] vs. 13% [2 of 16]), and visual recovery (endonasal 66% [2 of 3] vs. supraorbital 60% [3 of 5]). An extension lateral to the internal carotid artery was noted in 81% (13 of 16) of the supraorbital cases and in none of the endonasal cases. Tumor volume was 14.9 cm3 (±8.2 cm3) for supraorbital tumors versus 2.1 cm3 (±0.8 cm3) for the endonasal approach. CONCLUSIONS: Both approaches provide minimally invasive surgical routes accessing meningiomas of the sellar region. The ideal approach should be tailored to the individual patient considering the tumor anatomy, lateral extension, and the experience of the surgeon with both surgical approaches. We suggest using the supraorbital approach for larger meningiomas of sellar region with far lateral extension or broad vascular encasement.

Intracranial multiple myeloma may imitate subdural hemorrhage: How to overcome diagnostic limitations and avoid errors in treatment.

BACKGROUND: Although the diagnosis of subdural hematoma is usually straightforward, occasionally it may be erroneous, leading to mistakes in the treatment. For example, leptomeningeal malignancies, even in the absence of bleeding, may clinically and radiologically mimic subdural hemorrhage. OBJECTIVE: To stress the importance of not only intuitive thinking but also in analytic thinking in appropriate and accurate treatment strategies. METHODS AND ILLUSTRATIVE CASE: In this report, the clinical and radiological pitfalls in differentiating malignant leptomeningeal infiltration and subdural hematomas are discussed. A sample case of an intracranial extra-osseous manifestation of a multiple myeloma that is atypical with regard to its location and clinical presentation is presented for illustration. CONCLUSIONS: The variability of intracranial presentation and the wide spectrum of leptomeningeal malignancies necessitate careful preoperative evaluation of the patient's individual history as well as radiological images to avoid misdiagnosis. A clinician who has become familiar with the pitfalls in the differential diagnosis between leptomeningeal infiltrations and subdural hematoma will act more analytically to solve the patient's problems properly and avoid potential complications for the patient.

Aneurysm Surgery with Preoperative Three-Dimensional Planning in a Virtual Reality Environment: Technique and Outcome Analysis.

OBJECTIVE: Aneurysm surgery demands precise spatial understanding of the vascular anatomy and its surroundings. We report on a decade of experience planning clipping procedures preoperatively in a virtual reality (VR) workstation and present outcomes with respect to mortality, morbidity, and aneurysm occlusion rate. METHODS: Between 2006 and 2015, the clipping of 115 intracranial aneurysms in 105 patients was preoperatively planned with the Dextroscope, a stereoscopic, patient-specific VR environment. The outcome data for all cases, planned and performed in 3 institutions, were analyzed based on clinical charts and radiologic reports. RESULTS: Eighty-five incidental, unruptured aneurysms in 77 patients were electively planned and treated surgically. Mortality was 0% and morbidity (modified Rankin Scale score >2) was 2.6%. The rate of complete aneurysm obliteration on postoperative imaging was 91.8%. In addition, 30 aneurysms were treated in 28 patients with previous subarachnoid hemorrhage. Mortality in these cases was 3.6%, morbidity (modified Rankin Scale score >2) 7.1%, and the rate of complete aneurysm clipping was 90%. CONCLUSIONS: Meticulous three-dimensional surgical planning in a VR environment enhances the surgeon's spatial understanding of the individual vascular anatomy and allows clip preselection and positioning as well as anticipation of potential difficulties and complications. VR planning was associated, in this multi-institutional series, with excellent clinical outcomes and rates of complete aneurysm closure equivalent to benchmark cohorts.

Stereoscopic neuroanatomy lectures using a three-dimensional virtual reality environment.

INTRODUCTION: Three-dimensional (3D) computer graphics are increasingly used to supplement the teaching of anatomy. While most systems consist of a program which produces 3D renderings on a workstation with a standard screen, the Dextrobeam virtual reality VR environment allows the presentation of spatial neuroanatomical models to larger groups of students through a stereoscopic projection system. MATERIALS AND METHODS: Second-year medical students (n=169) were randomly allocated to receive a standardised pre-recorded audio lecture detailing the anatomy of the third ventricle accompanied by either a two-dimensional (2D) PowerPoint presentation (n=80) or a 3D animated tour of the third ventricle with the DextroBeam. Students completed a 10-question multiple-choice exam based on the content learned and a subjective evaluation of the teaching method immediately after the lecture. RESULTS: Students in the 2D group achieved a mean score of 5.19 (±2.12) compared to 5.45 (±2.16) in the 3D group, with the results in the 3D group statistically non-inferior to those of the 2D group (p<0.0001). The students rated the 3D method superior to 2D teaching in four domains (spatial understanding, application in future anatomy classes, effectiveness, enjoyableness) (p<0.01). CONCLUSION: Stereoscopically enhanced 3D lectures are valid methods of imparting neuroanatomical knowledge and are well received by students. More research is required to define and develop the role of large-group VR systems in modern neuroanatomy curricula.

The supraorbital endoscopic approach for aneurysms.

OBJECTIVE: To review our surgical experience in minimally invasive transcranial endoscope-assisted microsurgical treatment of intracranial aneurysms, using the supraorbital keyhole craniotomy. METHODS: The supraorbital keyhole approach was performed through an eyebrow skin incision in 793 cases for treatment of 989 intracranial aneurysms. Of patients, 474 were operated on after subarachnoid hemorrhage, and 319 were operated on under elective conditions. After lateral frontobasal burr hole trephination, a limited subfrontal craniotomy was created. To achieve adequate intraoperative exposure through the limited approach, endoscopes were used routinely. Surgical outcome was assessed using the modified Rankin scale. RESULTS: The transcranial endoscope-assisted microneurosurgery technique was used routinely via a supraorbital approach. In 152 operations (19.1%), the endoscope provided important visual information in the vicinity of the aneurysm, revealing subsequent clip repositioning. The results of incidental aneurysms were excellent with a modified Rankin scale score ≤2 in 96.52%. The overall outcome of ruptured aneurysms was good with a modified Rankin scale score ≤2 in 72.2% of patients. There were no approach-related intraoperative or postoperative complications. CONCLUSIONS: The minimally invasive supraorbital keyhole approach allowed safe surgical treatment of intracranial aneurysms, including after subarachnoid hemorrhage. The markedly improved endoscopic visualization increased the assessment of clip placement with ideal control of surrounding vessels including perforators for identification of incorrect clip position.

Patients' cosmetic satisfaction, pain, and functional outcomes after supraorbital craniotomy through an eyebrow incision.

OBJECT: The supraorbital approach through an eyebrow incision offers the opportunity to access a wide variety of lesions of the anterior, middle, and even the posterior fossa. The minimally invasive keyhole craniotomy limits brain exploration and retraction and offers the potential for improved surgical outcomes and reduced approach-related complications. Patient satisfaction, however, has not yet been reported in the literature. METHODS: From January 2002 through December 2011, the lead author (R.R.) used a supraorbital approach through an eyebrow incision for 418 patients with cerebral aneurysms, brain tumors or cystic lesions, and other miscellaneous pathological conditions. For 408 of these patients, a detailed retrospective case note review was conducted to extract data on surgical outcomes and complications, and 375 patients completed a follow-up patient satisfaction questionnaire. RESULTS: During the early perioperative period, 8 patients died (overall mortality rate 2.0%). Among patients surveyed, the overall level of satisfaction was high. Patients rated pain from the scar and headache on a scale from 1 to 5 (1 = no pain, 5 = severe pain) as follows: pain was a score of 1 for 289 patients (77.0%), 2 for 46 (12.3%), 3 for 22 (5.9%), 4 for 12 (3.2%), and 5 for 6 (1.6%). Patients also rated cosmetic outcome on a scale from 1 to 5 (1 = very pleasant, 5 = very unpleasant) as follows: outcome was a score of 1 for 315 patients (84.0%), 2 for 33 (8.8%), 3 for 14 (3.7%), 4 for 10 (2.7%), and 5 for 3 (0.8%). Postoperative chewing difficulty was reported for 8 patients (8 [2.1%] temporary, 0 permanent); palsy of the frontal muscle for 21 patients (5.6%; 13 [3.5%] temporary, 8 [2.1%] permanent); frontal hypesthesia for 31 patients (8.3%; 18 [4.8%] temporary, 13 [3.4%] permanent); and hyposmia for 11 patients (2.9%; 3 [0.8%] temporary, 8 [2.1%] permanent). CONCLUSIONS: The supraorbital approach to the anterior, middle, and posterior fossae through an eyebrow incision offers a favorable rate of approach-associated surgical complications and high patient satisfaction with cosmetic outcome.

The keyhole concept in neurosurgery.

OBJECTIVE: Improvements in preoperative diagnostic imaging as well as in microsurgical techniques significantly advanced the development of transcranial neurosurgery, allowing the treatment of complicated diseases through smaller and more specific approaches. METHODS: In this article, authors overviewed their experience in transcranial endoscope-assisted microsurgery, using limited-sized keyhole craniotomies. Over a 10-year period, authors treated more than 3000 patients according to the transcranial endoscope-assisted microsurgery concept, advanced by the pioneer of minimally invasive neurosurgery, Axel Perneczky. RESULTS AND CONCLUSION: In all cases, meticulous preoperative planning was done for determining the site, size, and optimal placement of the craniotomy as well as the trajectory toward the surgical target. Most importantly, the surgical approach was performed either completely or at least under permanent presence of the responsible senior surgeon from the moment of patient positioning until wound closure. The minimally invasive keyhole approaches allowed safe intraoperative control and adequate dealing with intracranial lesions. Essential preconditions for keyhole surgery were 1) careful selection of cases, 2) accurate preoperative planning, 3) placement of the craniotomy tailored to the individual case, and 4) intraoperative use of transcranial endoscope-assisted microsurgery techniques. Advantages of intraoperative endoscopic visualization were increased light intensity, extended viewing angle, and clear depiction of details even in hidden parts of the surgical field.

Mono-stereo-autostereo: the evolution of 3-dimensional neurosurgical planning.

BACKGROUND: In the past decade, surgery planning has changed significantly. The main reason is the improvements in computer graphical rendering power and display technology, which turned the plain graphics of the mid-1990s into interactive stereoscopic objects. OBJECTIVE: To report our experiences with 2 virtual reality systems used for planning neurosurgical operations. METHODS: A series of 208 operations were planned with the Dextroscope (Bracco AMT, Singapore) requiring the use of liquid crystal display shutter glasses. The participating neurosurgeons answered a questionnaire after the planning procedure and postoperatively. In a second prospective series of 33 patients, we used an autostereoscopic monitor system (MD20-3-D; Setred SA, Sweden) to plan intracranial operations. A questionnaire regarding the value of surgery planning was answered preoperatively and postoperatively. RESULTS: The Dextroscope could be integrated into daily surgical routine. Surgeons regarded their understanding of the pathoanatomical situation as improved, leading to enhanced intraoperative orientation and confidence compared with conventional planning. The autostereoscopic Setred system was regarded as helpful in establishing the surgical strategy and analyzing the pathoanatomical situation compared with conventional planning. Both systems were perceived as a backup in case of failure of the standard navigation system. CONCLUSION: Improvement of display and interaction techniques adds to the realism of the planning process and enables precise structural understanding preoperatively. This minimizes intraoperative guesswork and exploratory dissection. Autostereoscopic display techniques will further increase the value and acceptance of 3-dimensional planning and intraoperative navigation.

Image-guided neurosurgery with 3-dimensional multimodal imaging data on a stereoscopic monitor.

BACKGROUND: In the past 2 decades, intraoperative navigation technology has changed preoperative and intraoperative strategies and methodology tremendously. OBJECTIVE: To report our first experiences with a stereoscopic navigation system based on multimodality-derived, patient-specific 3-dimensional (3-D) information displayed on a stereoscopic monitor and controlled by a virtual user interface. METHODS: For the planning of each case, a 3-D multimodality model was created on the Dextroscope. The 3-D model was transferred to a console in the operating room that was running Dextroscope-compatible software and included a stereoscopic LCD (liquid crystal display) monitor (DexVue). Surgery was carried out with a standard frameless navigation system (VectorVision, BrainLAB) that was linked to DexVue. Making use of the navigational space coordinates provided by the VectorVision system during surgery, we coregistered the patient's 3-D model with the actual patient in the operating room. The 3-D model could then be displayed as seen along the axis of a handheld probe or the microscope view. The DexVue data were viewed with polarizing glasses and operated via a 3-D interface controlled by a cordless mouse containing inertial sensors. The navigational value of DexVue was evaluated postoperatively with a questionnaire. A total of 39 evaluations of 21 procedures were available. RESULTS: In all 21 cases, the connection of VectorVision with DexVue worked reliably, and consistent spatial concordance of the navigational information was displayed on both systems. The questionnaires showed that in all cases the stereoscopic 3-D data were preferred for navigation. In 38 of 39 evaluations, the spatial orientation provided by the DexVue system was regarded as an improvement. In no case was there worsened spatial orientation. CONCLUSION: We consider navigating primarily with stereoscopic, 3-D multimodality data an improvement over navigating with image planes, and we believe that this technology enables a more intuitive intraoperative interpretation of the displayed navigational information and hence an easier surgical implementation of the preoperative plan.

An aneurysm clipping training module for the neurosurgical training simulator NeuroSim.

Having introduced NeuroSim, the prototype of a neurosurgical training simulator at MMVR18, we present our first medical training module. NeuroSim is based on virtual reality and uses real-time algorithms for simulating tissue. It provides a native interface by using a real surgical microscope and original instruments. Having implemented some abstract tasks to train basic skills like hand-eye coordination or the handling of the microscope last year, we now present a medical module where an aneurysm has to be clipped. NeuroSim has been developed in cooperation with the neurosurgical clinic of the University of Heidelberg and VRmagic GmbH in Mannheim.

Measurement of cortical microcirculation during intracranial aneurysm surgery by combined laser-Doppler flowmetry and photospectrometry.

BACKGROUND: Accidental vessel occlusion is one major risk of intracranial aneurysm surgery potentially causing cerebral ischemia. The intraoperative assessment of cerebral ischemia remains a technological challenge. OBJECTIVE: As a novel approach, cortical tissue integrity was monitored using simultaneous measurements of regional capillary-venous cerebral blood flow (rvCBF), oxygen saturation (Srvo2), and hemoglobin amount (rvHb) during aneurysm surgery. METHODS: Fifteen patients scheduled for aneurysm surgery of the anterior and posterior circulation were included. A fiber optic probe was placed on the cortex associated with the distal branch of the aneurysmatic vessel. Blinded measurements by combined laser-Doppler flowmetry (rvCBF) and photospectrometry (Srvo2, rvHb) were performed before and after surgical clipping or trapping of the aneurysm. Data were correlated with postoperative imaging and neurological outcome. RESULTS: Cortical measurements could be successfully performed in all patients. Significant increase (>25% change from baseline) or decrease (<25% change from baseline) of rvCBF, Srvo2, and rvHb was detectable in 33 to 46% of patients after surgical intervention. Severe decrease (>50% change from baseline) of all parameters or solitary of rvCBF was correlated to reduced cerebral perfusion and neurological deficits in 2 patients. CONCLUSION: Combined laser-Doppler flowmetry and photospectrometry provides real-time information on cortical microcirculation. Intraoperative alterations of parameters (rvCBF, Srvo2, rvHb) might reflect changes of cerebral tissue integrity during intracranial aneurysm surgery.

The keyhole concept in aneurysm surgery: results of the past 20 years.

BACKGROUND: Improvements in preoperative imaging and intraoperative visualization have led to a refinement in surgical techniques. OBJECTIVE: Report of a 20-year experience with application of the keyhole technique as a contribution to the ongoing debate on the impact of limited craniotomies in aneurysm surgery. METHODS: Over a 20-year period, 1000 consecutive patients with 1297 aneurysms were surgically treated in 1062 operations: 651 in the acute stage after SAH and 411 with unruptured aneurysms. The outcome was assessed with the modified Rankin scale and approach-related complications. RESULTS: The majority of the cases were treated by 4 different keyhole approaches: The supraorbital approach was used in 793 patients for 989 aneurysms, the subtemporal in 48 patients for 50 aneurysms, the interhemispheric in 46 patients for 51 aneurysms, and the retromastoidal in 55 patients for 55 aneurysms. In 120 patients, the classic pterional approach was applied to treat 152 aneurysms. The results of unruptured aneurysms were good (modified Rankin scale ≤ 2) in 96.52%. The complication rates of the keyhole approaches were less than in the pterional group, although the difference did not reach statistical significance. CONCLUSION: The overall outcome, rate of retreatment, and approach-related complications with keyhole approaches for the management of ruptured and unruptured aneurysms are comparable to recently published conventional surgical aneurysm series. In addition to the common benefits of limited-exposure approaches, this series demonstrates appropriate safety and applicability of the keyhole technique in aneurysm surgery.

Neurosurgical craniotomy localization using a virtual reality planning system versus intraoperative image-guided navigation.

PURPOSE: Accurate craniotomy placement is essential for frameless neuronavigation in minimally invasive neurosurgery. A craniotomy using virtual reality (VR) can be as accurate as neuronavigation. METHODS: We prospectively enrolled 48 patients that underwent minimally invasive cranial procedures planned using VR, followed by neuronavigation. First, craniotomies were planned using VR derived measurements. Second, frameless neuronavigation was applied to define the craniotomy. The locations of these paired craniotomies were compared. A correctly placed craniotomy was defined as one that enabled the surgeon to totally remove the pathology without need to enlarge the craniotomy intraoperatively. RESULTS: Using VR, the size and the position of the craniotomy were measured correctly in 47 of 48 cases (98%). In 44 of 48 cases (92%), neuronavigation identified the craniotomy site correctly. In cases where neuronavigation failed, minimally invasive surgery was successfully completed using preoperative VR surgery planning. No statistically significant difference was found between craniotomy localization using VR surgery planning or standard frameless neuronavigation (p = 0.36). CONCLUSION: The craniotomy for minimally invasive neurosurgical procedures can be identified accurately using VR surgery planning or neuronavigation. In cases of neuronavigation failure, VR surgery planning serves as an effective backup system to perform a minimally invasive operation.

Near-infrared indocyanine green videoangiography versus microvascular Doppler sonography in aneurysm surgery.

INTRODUCTION: The quality of surgical treatment of intracranial aneurysms is determined by complete aneurysm occlusion and restoration of flow in the parent, branching and perforating vessels. In postoperative digital subtraction angiography (DSA), unexpected aneurysm residuals and vessel occlusions are frequently detected. Here, the value of two nearly noninvasive and cost-effective techniques for intraoperative flow evaluation (near-infrared indocyanine green video angiography (ICG-VA) and microvascular Doppler sonography (mDs)) is investigated in a prospective study. PATIENTS AND METHODS: Over a period of 10 months, the authors surgically clipped 50 aneurysms under intraoperative pre- and post-clipping evaluation of flow in the parent, branching and perforating vessels and the aneurysm sack by the two techniques. Intraoperative applicability of each technique was compared to each other and to postoperative digital subtraction angiography as standard evaluation technique. RESULTS: Forty-five aneurysms were totally occluded without vessel compromise (90%). Intraoperatively, ICG-VA was considered useful in 43 cases (86%) and mDs in 44 cases (88%), respectively. Both techniques could compensate each other's weak points to a certain degree; but two branch occlusions (4%) and three neck remnants (6%) were revealed by postoperative DSA. CONCLUSION: Both techniques have specific drawbacks that could be compensated by each other, to a certain extent. Intraoperatively, ICG-VA and mDs should not be considered competitive, but complementary. This study implicates that the combination of both applications on a routine basis assures the quality of aneurysm surgery by nearly noninvasive and cost-effective techniques. However, DSA remains the gold standard for evaluation of aneurysm occlusion.

Simple endoscopic decompression of cubital tunnel syndrome with the Agee system: anatomic study and first clinical results.

BACKGROUND: Simple decompression in ulnar nerve compression syndromes offers options for endoscopic applications. OBJECTIVE: The authors present their initial experience with the Agee device. PATIENTS AND METHODS: The monoportal endoscopic technique (Agee system) was evaluated on 10 cadaveric arms. Subsequently, 32 arms of 29 patients were operated on between January 2006 and March 2009. All patients presented with typical clinical signs and neurophysiologic studies. Long-term follow-up examinations were obtained in 27 of 32 arms. RESULTS: In the cadaver study, the ulnar nerve was always correctly identified. No nerve damage occurred, and sufficient decompression of the ulnar nerve was always achieved. In the clinical series, no intraoperative complications were observed. A change to open technique was not required, and no worsening of the cubital tunnel syndrome occurred. Two wound infections required surgical wound cleaning. Wound hematomas treated conservatively were found in 5 cases. On long-term follow-up, an improvement in the McGowan- Classification was achieved in 22 of 27 cases. One patient was operated on by open surgery after endoscopic surgery. CONCLUSION: The endoscopic technique for ulnar nerve entrapment syndrome using an Agee device appears to be safe and efficient. The results are comparable to those achieved with simple open decompression. A randomized prospective study should be performed to further evaluate the value of new technique in ulnar nerve entrapment syndrome.

Minimally invasive superficial temporal artery to middle cerebral artery bypass through a minicraniotomy: benefit of three-dimensional virtual reality planning using magnetic resonance angiography.

OBJECT: The aim of the authors in this study was to introduce a minimally invasive superficial temporal artery to middle cerebral artery (STA-MCA) bypass surgery by the preselection of appropriate donor and recipient branches in a 3D virtual reality setting based on 3-T MR angiography data. METHODS: An STA-MCA anastomosis was performed in each of 5 patients. Before surgery, 3-T MR imaging was performed with 3D magnetization-prepared rapid acquisition gradient echo sequences, and a high-resolution CT 3D dataset was obtained. Image fusion and the construction of a 3D virtual reality model of each patient were completed. RESULTS: In the 3D virtual reality setting, the skin surface, skull surface, and extra- and intracranial arteries as well as the cortical brain surface could be displayed in detail. The surgical approach was successfully visualized in virtual reality. The anatomical relationship of structures of interest could be evaluated based on different values of translucency in all cases. The closest point of the appropriate donor branch of the STA and the most suitable recipient M(3) or M(4) segment could be calculated with high accuracy preoperatively and determined as the center point of the following minicraniotomy. Localization of the craniotomy and the skin incision on top of the STA branch was calculated with the system, and these data were transferred onto the patient's skin before surgery. In all cases the preselected arteries could be found intraoperatively in exact agreement with the preoperative planning data. Successful extracranial-intracranial bypass surgery was achieved without stereotactic neuronavigation via a preselected minimally invasive approach in all cases. Subsequent enlargement of the craniotomy was not necessary. Perioperative complications were not observed. All bypasses remained patent on follow-up. CONCLUSIONS: With the application of a 3D virtual reality planning system, the extent of skin incision and tissue trauma as well as the size of the bone flap was minimal. The closest point of the appropriate donor branch of the STA and the most suitable recipient M(3) or M(4) segment could be preoperatively determined with high accuracy so that the STA-MCA bypass could be safely and effectively performed through an optimally located minicraniotomy with a mean diameter of 22 mm without the need for stereotactic guidance.

Virtual reality system for planning minimally invasive neurosurgery. Technical note.

OBJECT: The authors report on their experience with a 3D virtual reality system for planning minimally invasive neurosurgical procedures. METHODS: Between October 2002 and April 2006, the authors used the Dextroscope (Volume Interactions, Ltd.) to plan neurosurgical procedures in 106 patients, including 100 with intracranial and 6 with spinal lesions. The planning was performed 1 to 3 days preoperatively, and in 12 cases, 3D prints of the planning procedure were taken into the operating room. A questionnaire was completed by the neurosurgeon after the planning procedure. RESULTS: After a short period of acclimatization, the system proved easy to operate and is currently used routinely for preoperative planning of difficult cases at the authors' institution. It was felt that working with a virtual reality multimodal model of the patient significantly improved surgical planning. The pathoanatomy in individual patients could easily be understood in great detail, enabling the authors to determine the surgical trajectory precisely and in the most minimally invasive way. CONCLUSIONS: The authors found the preoperative 3D model to be in high concordance with intraoperative conditions; the resulting intraoperative "déjà-vu" feeling enhanced surgical confidence. In all procedures planned with the Dextroscope, the chosen surgical strategy proved to be the correct choice. Three-dimensional virtual reality models of a patient allow quick and easy understanding of complex intracranial lesions.

White matter fiber tracking computation based on diffusion tensor imaging for clinical applications.

Fiber tracking allows the in vivo reconstruction of human brain white matter fiber trajectories based on magnetic resonance diffusion tensor imaging (MR-DTI), but its application in the clinical routine is still in its infancy. In this study, we present a new software for fiber tracking, developed on top of a general-purpose DICOM (digital imaging and communications in medicine) framework, which can be easily integrated into existing picture archiving and communication system (PACS) of radiological institutions. Images combining anatomical information and the localization of different fiber tract trajectories can be encoded and exported in DICOM and Analyze formats, which are valuable resources in the clinical applications of this method. Fiber tracking was implemented based on existing line propagation algorithms, but it includes a heuristic for fiber crossings in the case of disk-shaped diffusion tensors. We successfully performed fiber tracking on MR-DTI data sets from 26 patients with different types of brain lesions affecting the corticospinal tracts. In all cases, the trajectories of the central spinal tract (pyramidal tract) were reconstructed and could be applied at the planning phase of the surgery as well as in intraoperative neuronavigation.

A collaborative virtual reality environment for neurosurgical planning and training.

OBJECTIVE: We have developed a highly interactive virtual environment that enables collaborative examination of stereoscopic three-dimensional (3-D) medical imaging data for planning, discussing, or teaching neurosurgical approaches and strategies. MATERIALS AND METHODS: The system consists of an interactive console with which the user manipulates 3-D data using hand-held and tracked devices within a 3-D virtual workspace and a stereoscopic projection system. The projection system displays the 3-D data on a large screen while the user is working with it. This setup allows users to interact intuitively with complex 3-D data while sharing this information with a larger audience. RESULTS: We have been using this system on a routine clinical basis and during neurosurgical training courses to collaboratively plan and discuss neurosurgical procedures with 3-D reconstructions of patient-specific magnetic resonance and computed tomographic imaging data or with a virtual model of the temporal bone. Working collaboratively with the 3-D information of a large, interactive, stereoscopic projection provides an unambiguous way to analyze and understand the anatomic spatial relationships of different surgical corridors. In our experience, the system creates a unique forum for open and precise discussion of neurosurgical approaches. CONCLUSION: We believe the system provides a highly effective way to work with 3-D data in a group, and it significantly enhances teaching of neurosurgical anatomy and operative strategies.