Martin Glaser

Decreased Dopamine D2/D3‐Receptor Binding in Temporal Lobe Epilepsy: An [18F]Fallypride PET Study

Summary:  Purpose: Although animal data are suggestive, evidence for an alteration of the extrastriatal dopaminergic system in human focal epilepsy is missing.

Differentiation of fibroblastic meningiomas from other benign subtypes using diffusion tensor imaging.

To differentiate fibroblastic meningiomas, usually considered to be of a hard consistency, from other benign subtypes using diffusion tensor imaging (DTI).

Intraoperative monitoring of cerebral microcirculation and oxygenation--a feasibility study using a novel photo-spectrometric laser-Doppler flowmetry.

Background The present study assesses the utility of a novel invasive device (O2C-, oxygen-to-see-device) for intraoperative measurement of the cerebral microcirculation. CO2 vasoreactivity during 2 different propofol concentrations was used to investigate changes of capillary venous cerebral blood flow (rvCBF), oxygen saturation (srvO2), and hemoglobin concentration (rvHb) during craniotomy. Methods Thirty-four patients were randomly assigned to a low propofol (4 mg/kg/h) versus a high propofol (6 mg/kg/h) group. A fiberoptic probe was applied on the cortex next to the surgical site. Measurements were performed during lower (35 mm Hg) and higher (45 mm Hg) levels of partial pressure of carbon dioxide (paCO2). Arterio-venous difference in oxygen concentration (avDO2) and approximated cerebral metabolic rate of oxygen (aCMRO2) were calculated for each paCO2 state. Linear models were fitted to test changes of end points in response to paCO2 and propofol concentration. Results In comparison to the lower levels of paCO2, higher levels of paCO2 increased rvCBF (P<0.001), and srvO2 (P=0.002). RvHb remained unchanged during measurements (P=0.325). Calculated avDO2 decreased with increasing paCO2 (P<0.001), whereas aCMRO2 did not change during the study (P=0.999). Propofol concentration had no effect on measured or calculated end points. Conclusions Increase of rvCBF by paCO2 indicates a preserved CO2 reactivity independent of propofol anesthesia. The consecutive rise in srvO2 implies enhanced oxygen availability due to vasodilatation. Unchanged rvHb represents constant venous hemoglobin concentration. As expected, calculated avDO2 decreases with increased paCO2, whereas aCMRO2 remains unchanged. Despite the promising technical approach, the technology needs validation and further investigation for usage during neurosurgery.

The effects of arterial carbon dioxide partial pressure and sevoflurane on capillary venous cerebral blood flow and oxygen saturation during craniotomy

BACKGROUND: Intraoperative routine monitoring of cerebral blood flow and oxygenation remains a technological challenge. Using the physiological principle of carbon dioxide reactivity of cerebral vasculature, we investigated a recently developed neuromonitoring device (oxygen-to-see, O2C™ device) for simultaneous measurements of regional cerebral blood flow (rvCBF), blood flow velocity (rvVelo), oxygen saturation (srvO2), and hemoglobin amount (rvHb) at the capillary venous level in patients subjected to craniotomy. METHODS: Twenty-six neurosurgical patients were randomly assigned to anesthesia with 1.4% or 2.0% sevoflurane end-tidal concentration. After craniotomy, a fiberoptic probe was applied on a macroscopically healthy surface of cerebral tissue next to the site of surgery. Simultaneous measurements in 2 and 8 mm cerebral depth were performed in each patient during lower (35 mm Hg) and higher (45 mm Hg) levels (random order) of arterial carbon dioxide partial pressure (Paco2). The principle of these measurements relies on the combination of laser-Doppler flowmetry (rvCBF, rvVelo) and photo-spectrometry (srvO2, rvHb). Linear models were fitted to test changes of end points (rvCBF, rvVelo, srvO2, rvHb) in response to lower and higher levels of Paco2, 1.4% and 2.0% sevoflurane end-tidal concentration, and 2 and 8 mm cerebral depth. RESULTS: RvCBF and rvVelo were elevated by Paco2 independent of sevoflurane concentration in 2 and 8 mm depth of cerebral tissue (P < 0.001). Higher Paco2 induced an increase in mean srvO2 from 50% to 68% (P < 0.001). RvVelo (P < 0.001) and srvO2 (P = 0.007) were higher in 8 compared with 2 mm cerebral depth. RvHb was not influenced by alterations in Paco2 but positively correlated to sevoflurane concentration (P = 0.005). CONCLUSIONS: Increases in rvCBF and rvVelo by Paco2 suggest preserved hypercapnic vasodilation under anesthesia with sevoflurane 1.4% and 2.0% end-tidal concentration. A consecutive increase in srvO2 implies that cerebral arteriovenous difference in oxygen was decreased by elevated Paco2. Unchanged levels of rvHb signify that there was no blood loss during measurements. Data suggest that the device allows detection of local changes in blood flow and oxygen saturation in response to different Paco2 levels in predominant venous cerebral microvessels.

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.

An alternative projection for fluoroscopic-guided needle insertion in the foramen ovale: technical note

PurposePuncture of the ganglion Gasseri through the foramen ovale and subsequent thermocoagulation, balloon compression, or glycerin injection is a well-established technique to treat trigeminal neuralgia. However, direct puncture of the foramen is sometimes difficult. Here, the authors present a simple technique of improved biplane fluoroscopic control for insertion of the needle into the foramen ovale.MethodsThe authors evaluated an alternative oblique X-ray trajectory for the correct placement of a needle into the foramen ovale on cadaveric skull models. After determination of the ideal X-ray trajectory, 13 subsequent patients suffering from trigeminal neuralgia were subjected to intraforaminal needle placement with application of the alternative X-ray trajectory.ResultsAn oblique projection with the X-ray tube (mean rotation 20.9° and angulations 28°) aligned coaxially to the inserted needle is proposed. On cadaver skull models, this oblique trajectory appeared to be ideal for visualization of the correct needle position. In the 13 patients, an immediate needle insertion into the foramen ovale was achieved under this direct oblique fluoroscopic control. No complications were observed.ConclusionsExperimentally and clinically, the new projection demonstrated three distinct advantages over the standard submental projection: Firstly, the foramen ovale can be better visualized independent of the patients position. Secondly, needle correction or insertion can be performed much easier because of the direct fluoroscopic control. Thirdly, the correct needle position in the foramen ovale is more reliably determined than with the submental projection due to projection geometry. Further studies are needed to give evidence that the needle insertion into the foramen ovale is easier achieved with the coaxial projection than with the standard technique.

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 surgeons 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.

Postoperative rehabilitation after deep brain stimulation surgery for movement disorders

Deep brain stimulation (DBS) is a highly efficient, evidence-based therapy for a set of neurological and psychiatric conditions and especially movement disorders such as Parkinsons disease, essential tremor and dystonia. Recent developments have improved the DBS technology. However, no unequivocal algorithms for an optimized postoperative care exist so far. The aim of this review is to provide a synopsis of the current clinical practice and to propose guidelines for postoperative and rehabilitative care of patients who undergo DBS. A standardized work-up in the DBS centers adapted to each patients clinical state and needs is important, including a meticulous evaluation of clinical improvement and residual symptoms with a definition of goals for neurorehabilitation. Efficient and complete information transfer to subsequent caregivers is essential. A coordinated therapy within a multidisciplinary team (trained in movement disorders and DBS) is needed to achieve the long-range maximal efficiency. An optimized postoperative framework might ultimately lead to more effective results of DBS.

Intraoperative Neuronavigation von Hirntumoren unter Einschluss des Tractus corticospinalis mit Hilfe von Diffusion Tensor Imaging und Fiber Tracking

ZusammenfassungZiel:Durch Integration des Fiber Tracking in die intraoperative Neuronavigation sollten die Lage der kortikospinalen Bahnen bei der Operation von Hirntumoren dargestellt und gleichzeitig die Lokalisation der Trajektorien mit einer unabhängigen Methode auf Ortsgenauigkeit überprüft werden.Patienten und Methodik:Dazu wurden bei 21 Patienten MR-Untersuchungen mit Diffusion Tensor Imaging (DTI) durchgeführt, die Tensorenfelder berechnet und die Bahnenverläufe mittels eines modifizierten „Line-Propagation“-Algorithmus bestimmt. Der Algorithmus kann die Richtung der Haupteigenvektoren auch über Faserkreuzungen hinweg verfolgen. Das „Tracking“ im peritumoralen Ödem ist durch die dort herabgesetzte fraktionale Anisotropie (FA) erschwert, so dass in diesen Fällen eine Modifizierung der Stopp-Kriterien des Algorithmus erforderlich war. Nach Koregistrierung der berechneten Trajektorien mit hochaufgelösten dreidimensionalen (3-D) Datensätzen und Umwandlung in das DICOM-Format wurden die Daten in ein neurochirurgisches Navigationssystem eingespeist.Ergebnisse:In allen 21 Fällen konnten die kortikospinalen Bahnen dargestellt werden. Dies wurde von den Neurochirurgen als sehr hilfreich empfunden, um eine Schädigung der Bahnen zu vermeiden. Während der Tumorentfernung wurde die Position der Bahnen bei 13 Patienten mittels elektrophysiologischer kortikaler und in 10 Fällen mit subkortikaler Stimulation überprüft und mit der Position der Trajektorien im Navigationssystem verglichen. In allen 13 Fällen war die kortikale Stimulation erfolgreich und bestätigte die Position des Gyrus praecentralis, aus dem die Trajektorien entsprangen. Eine positive Antwort auf die subkortikale Stimulation in der Wand der Tumorhöhle wurde dagegen nur in fünf von zehn Fällen erreicht, bei denen der Abstand zwischen Stimulationsort und Position der virtuellen Bahnen ≤ 1 cm war. In allen Fällen mit negativem Ergebnis war der Abstand größer.Schlussfolgerung:Wenn sich die Zuverlässigkeit des beschriebenen Fiber Tracking bei weiteren Untersuchungen bestätigt, sollte die Methode als wichtige Komponente in die Neuronavigationssysteme aufgenommen werden.AbstractPurpose:To include information about the position of the corticospinal tract into intraoperative neuronavigation of brain tumor surgery, and to check the topographic correctness of fiber tracking by an independent method.Patients and Methods:The authors performed diffusion tensor imaging (DTI) in 21 patients, computed diffusion tensor fields, and carried out fiber tracking by means of a modified line-propagation algorithm. The algorithm is able to follow the direction of the mean eigenvectors across voxels in areas of fiber crossings. Tracking in peritumoral edema with reduced fractional anisotropy (FA) was facilitated by alteration of the stopping criteria of the algorithm. After coregistration of the trajectories with high-resolution three-dimensional (3-D) data sets and conversion to DICOM format, the data were transferred to a neurosurgical navigation system. During removal of the tumor, the position of the tracts was checked by electrophysiological stimulation of the precentral cortex in 13 patients and by subcortical stimulation of the walls of the resulting cavity in ten and compared to the position of the trajectories as shown by the navigation system.Results:The corticospinal tracts could be demonstrated in all cases including those with severe edema. Their inclusion into the navigation system was regarded to be helpful during surgery to avoid damage to these tracts. The position of the precentral gyrus from which the trajectories originated could be confirmed by cortical stimulation in all cases. Positive responses to subcortical stimulation, however, were achieved in five cases only in which the stimulation was performed in close vicinity to the virtual tracts. In the other five patients, the distance between the stimulation position and the trajectories was > 1 cm.Conclusion:If the reliability of the fiber tracking technique can be confirmed by further intraoperative electrophysiological verification of the tract position, this method should be included into neuronavigation systems.

Frontal Lobe Connectivity and Network Community Characteristics are Associated with the Outcome of Subthalamic Nucleus Deep Brain Stimulation in Patients with Parkinson’s Disease

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is nowadays an evidence-based state of the art therapy option for motor and non-motor symptoms in patients with Parkinson’s disease (PD). However, the exact anatomical regions of the cerebral network that are targeted by STN–DBS have not been precisely described and no definitive pre-intervention predictors of the clinical response exist. In this study, we test the hypothesis that the clinical effectiveness of STN–DBS depends on the connectivity profile of the targeted brain networks. Therefore, we used diffusion-weighted imaging (DWI) and probabilistic tractography to reconstruct the anatomical networks and the graph theoretical framework to quantify the connectivity profile. DWI was obtained pre-operatively from 15 PD patients who underwent DBS (mean age = 67.87 ± 7.88, 11 males, H&Y score = 3.5 ± 0.8) using a 3T MRI scanner (Philips Achieva). The pre-operative connectivity properties of a network encompassing frontal, prefrontal cortex and cingulate gyrus were directly linked to the postoperative clinical outcome. Eccentricity as a topological-characteristic of the network defining how cerebral regions are embedded in relation to distant sites correlated inversely with the applied voltage at the active electrode for optimal clinical response. We found that network topology and pre-operative connectivity patterns have direct influence on the clinical response to DBS and may serve as important and independent predictors of the postoperative clinical outcome.