Dirk Winkler

Intraoperative MRI to guide the resection of primary supratentorial glioblastoma multiforme—a quantitative radiological analysis

Patients with supratentorial high-grade glioma underwent surgery within a vertically open 0.5-T magnetic resonance (MR) system to evaluate the efficacy of intraoperative MR guidance in achieving gross-total resection. For 31 patients, preoperative clinical data and MR findings were consistent with the putative diagnosis of a high-grade glioma, in 23 cases in eloquent regions. Tumor resections were carried out within a 0.5-T MR SIGNA SP/i (GE Medical Systems, USA). The resection of the lesion was carried out using fully MR compatible neurosurgical equipment and was stopped at the point when the operation was considered complete by the surgeon viewing the operation field with the microscope. We repeated imaging to determine the residual tumor volume only visible with MRI. Areas of tissue that were abnormal on these images were localized in the bed of resection by using interactive MR guidance. The procedure of resection, imaging control and interactive image guidance was repeated where necessary. Almost all tissue with abnormal characteristics was resected, with the exception of tissue localized in eloquent brain areas. The diagnosis of glioblastoma was confirmed in all 31 cases. When comparing the tumor volume before resection and at the point where the neurosurgeon would otherwise have terminated surgery (“first control”), residual tumor tissue was detectable in 29/31 patients; the mean residual tumor volume was 30.7±24%. After repeated resections under interactive image guidance the mean residual tumor volume was 15.1%. At this step we found tumor remnants only in 20/31 patients. The perioperative morbidity (12.9%) was low. Twenty-seven patients underwent sufficient postoperative radiotherapy. We found a significant difference (logrankp=0.0037) in the mean survival times of the two groups with complete resection (n=10, median survival time 537 days) and incomplete resection (n=17, median survival time 237 days). The resection of primary glioblastoma multiforme under intraoperative MR guidance as demonstrated is a possibility to achieve a more complete removal of the tumor than with conventional techniques. In our small but homogeneous patient group we found an increase in the median survival time in patients with MRI for complete tumor resection, and the overall surgical morbidity was low.

Correlation of continuously monitored regional cerebral blood flow and brain tissue oxygen

SummaryBackground. The purpose of this study was to investigate the relationship between continuously monitored regional cerebral blood flow (CBF) and brain tissue oxygen (PtiO2).Methods. Continuous advanced multimodal neuromonitoring including monitoring of PtiO2 (Licox, GMS) and CBF (QFlow, Hemedex) was performed in eight patients after severe subarachnoid haemorrhage (n=5) and traumatic brain injury (n=3) for an average of 9.6 days. Parameters were measured using a flexible polarographic PtiO2-probe and a thermal diffusion CBF-microprobe.Findings. Regarding the whole monitoring period in all patients, the data indicated a significant correlation between CBF and PtiO2 (r=0.36). In 72% of 400 analysed intervals of 30 minutes duration with PtiO2 changes larger than 5 mmHg, a strong correlation between CBF and PtiO2 existed (r > 0.6). In 19% of intervals a still statistically significant correlation was observed (0.3 < r < 0.6). During the remaining 9% no correlation was found (r < 0.3). Regarding the clinical stability of the monitoring devices, the CBF monitoring system allowed monitoring of CBF in 64% of the time when PtiO2 monitoring was possible only. Phases of non-monitoring were mostly due to fever of the patient, when the system does not allow monitoring to avoid overheating of the cerebral tissue.Conclusions. This study suggests a correlation between CBF and PtiO2. The level of PtiO2 seems to be predominately determined by regional CBF, since changes in PtiO2 were correlated in 90% of episodes to simultaneous changes of CBF.

The first evaluation of brain shift during functional neurosurgery by deformation field analysis

Stereotactic surgery is based on a high degree of accuracy in defining and localising intracranial targets and placing surgical tools. Brain shift can influence its accuracy significantly. Deep brain stimulation of the subthalamic nucleus can markedly change the quality of life of patients with advanced Parkinson’s disease, but the outcome depends on the quality of electrode placement. A patient is reported in whom the placement of the second electrode was not successful. Deformation field analysis of pre- and postoperative three dimensional magnetic resonance images showed an intraoperative brain movement of 2 mm in the region of the subthalamic nucleus (the target point). Electrode repositioning resulted in efficient stimulation effects. This case report shows the need to reduce risk factors for intraoperative brain movement and demonstrates the ability of deformation field analysis to quantify this complication.

Investigation of time-dependency of intracranial brain shift and its relation to the extent of tumor removal using intra-operative MRI

Abstract The object of the paper is to investigate intra-operative brainshift and its relation to the extent of tumor removal. Repeated T1w 3D datasets were acquired at different time points intra-operatively (T0; T1; T2... Tx) using a vertical open 0.5T MR scanner in six patients with intracranial tumor. An offline analysis with initial linear registration, intensity adjustment and finally nonlinear registration of the first versus subsequent time points (T0/T1; T0/T2... T0/Tx) was performed, yielding a 3D displacement vector field that describes the brainshift. Brainshift was analysed qualitatively and quantitatively. A semi-automatic segmentation technique was used for calculation of the tumor size and the size of tumor remnants. Semi-automatic segmentation was reliable in all but two cases. Segmentation was difficult and unreliable in astrocytomas grade II. The shift basically followed gravity. The major shift reached levels up to 25 mm. Significant shift was observed at the first time point (T0). Intra-operative brainshift can be analysed qualitatively and also captured quantitatively. Neuronavigation that is based on pre-operatively acquired datasets is associated with a significant risk of surgical morbidity at a very early time point. Parallelisation on a workstation cluster may reduce computation time so that information about the displacement can facilitate updated navigation.

Spinal markers: A new method for increasing accuracy in spinal navigation

Spinal navigation opens up a completely new dimension in the planning and realization of neurosurgical and orthopedic procedures, and offers the possibility of simulating the operation preoperatively. There is currently only limited experience with spinal navigation, and despite the development of advanced software, intraoperative difficulties include identification of characteristic and reproducible anatomical landmarks, localization of these points in the surgical field, referencing, and intraoperative control. We report the use of a new kind of implantable fiducial marker in a case of a 58-year-old female patient with spondylolisthesis. Percutaneously applied spinal markers were used as prominent anatomical landmarks and permitted much easier intraoperative handling. In our opinion, in the hands of an experienced neurosurgeon or orthopedist, the additional preoperative time required for placement of such spinal markers is negligible.

Fusion von MRT-, fMRT- und intraoperativen MRT-Daten Methode und klinische Bedeutung am Beispiel neurochirurgischer Interventionen

ZusammenfassungZiel dieser Arbeit waren die Realisierung und klinische Bewertung einer Bildfusion präoperativer MRT- und fMRT-Bilder mit intraoperativen Datensätzen eines interventionellen MRT-Systems am Beispiel neurochirurgischer Eingriffe.Ein vertikal offenes 0,5-T-MRT-System wurde mit einem erweiterten Navigationssystem ausgestattet, welches eine Integration zusätzlicher Bildinformationen (Hochfeld-MRT, fMRT, CT) in die intraoperativ akquirierten Datensätze erlaubt. Diese fusionierten Bilddaten wurden zur Interventionsplanung und multimodalen Navigation verwendet.Bisher wurde das System bei insgesamt 70 neurochirurgischen Eingriffen eingesetzt, davon 13 mit Bilddatenfusion (rund 15-minütiger Zusatzaufwand). Das erweiterte Navigationssystem zeichnet sich im Vergleich zur systemeigenen Navigation auf der Basis kontinuierlich akquirierbarer Real-time-Bilder durch eine schnellere Bildwiederholung und eine höhere Bildqualität aus. Der Vergleich beider Navigationsbilder erlaubt das frühzeitige Erkennen von Patienten- bzw. Gewebeverlagerungen.Die multimodale Bildfusion erlaubte eine differenziertere Navigationsplanung, insbesondere bei der Resektion tief liegender Hirntumoren oder bei Läsionen in enger Nachbarschaft zu eloquenten Arealen. Die erweiterte intraoperative Orientierung bzw. Instrumentenführung erhöht die Sicherheit und Genauigkeit neurochirurgischer Interventionen.AbstractThe aim of this work was to realize and clinically evaluate an image fusion platform for the integration of preoperative MRI and fMRI data into the intraoperative images of an interventional MRI system with a focus on neurosurgical procedures.A vertically open 0.5 T MRI scanner was equipped with a dedicated navigation system enabling the registration of additional imaging modalities (MRI, fMRI, CT) with the intraoperatively acquired data sets. These merged image data served as the basis for interventional planning and multimodal navigation.So far, the system has been used in 70 neurosurgical interventions (13 of which involved image data fusion – requiring 15 minutes extra time). The augmented navigation system is characterized by a higher frame rate and a higher image quality as compared to the system-integrated navigation based on continuously acquired (near) real time images. Patient movement and tissue shifts can be immediately detected by monitoring the morphological differences between both navigation scenes.The multimodal image fusion allowed a refined navigation planning especially for the resection of deeply seated brain lesions or pathologies close to eloquent areas. Augmented intraoperative orientation and instrument guidance improve the safety and accuracy of neurosurgical interventions.

Effects of subthalamic nucleus stimulation on striatal dopaminergic transmission in patients with Parkinson’s disease within one-year follow-up

The mechanisms by which deep brain stimulation (DBS) of the subthalamic nucleus (STN) leads to clinical benefit in Parkinson’s disease (PD), especially with regard to dopaminergic transmission, remain unclear. Therefore, the objective of our study was to evaluate alterations of synaptic dopaminergic signaling following bilateral STN-DBS in advanced PD within a one-year follow-up. We used [123I]FP-CIT single-photon emission computed tomography (SPECT) to measure dopamine transporter (DAT) availability and [123I]IBZM SPECT to assess dopamine D2 receptor (D2R) availability (stimulator ON condition).Patients (n = 18) showed a tendency towards a better suppression of symptoms after STN-DBS (Unified Parkinson’s Disease Rating Scale motor score with medication decreased from 24. 1 ± 16. 1 to 15. 4 ± 7. 45; p = 0. 002) while medication was strongly reduced (61 % reduction of levodopa equivalent units; p < 0. 0001). No changes of striatal [123I]FP-CIT binding and an increase of [123I]IBZM binding up to 16 % (p < 0. 05) between pre-surgery and follow-up investigations were noticed. These data show that clinical improvement and reduction of dopaminergic drugs in patients with advanced PD undergoing bilateral STN-DBS are paralleled by stable DAT and recovery of striatal D2R availability 12 months after surgery.

Clinical Results in MR-Guided Therapy for Malignant Gliomas

The prognostic impact of the extent of tumour resection in surgery of malignant glioma patients remains controversial. We report the results of cumulative survival of malignant glioma patients operated with MR-guidance. Patients with complete tumour removal were compared with a population of patients with incomplete tumour removal. A 0.5 T scanner was used to criticize the extent of resection during surgery. In total no significant difference could be found, however there is a tendency that complete tumour removal seems to be associated with a slightly increased median survival time.

Cerebrospinal fluid leak after microsurgical surgery in vestibular schwannomas via retrosigmoidal craniotomy

Abstract Objective: Cerebrospinal fluid (CSF) leak is still a common complication in surgery of vestibular schwannoma, increasing morbidity and prolonging hospital stay. Our single center study was performed to determine the incidences of CSF leaks after microsurgical removal of vestibular schwannoma via a retrosigmoidal approach with two different surgical closure techniques. Methods: Between January 2003 and December 2009 in 81 patients, microsurgical tumor resection using a suboccipital, retrosigmoidal approach was performed with an interdisciplinary ENT and neurosurgical management was performed. In 41 cases, the dural closure was done using a sandwich technique: subdural closure with TissuFleece® respectively Spongostan®, and after that dural suture and epidural Tachosil® were fixed on. In 40 cases, the dura was sealed epidurally with Tachosil after suture. In 65 cases, the posterior wall of the petrous bone was drilled. The closure was performed using muscle and FibrinGlue®. All patients had a minimal follow-up of 1 year. Results: Seven patients (8·6%) developed a CSF fistula. Three patients (3·7%) underwent surgical procedure because of persisting CSF fistula while in four cases (4·9%) spontaneous closure under lumbar drain was observed. Comparing the different techniques of dural sealing, we found in 41 patients with sandwich technique three CSF leaks (7·3%) while there were four CSF leaks (10%) in 40 patients with a single epidurally sealed dural closure (P=0·69). No rhinorrhea or otorhinorrhea was observed. No intracranial infection or meningitis in case of CSF leak occurred. Conclusion: Suture and occlusion of the dura is an important step to prevent CSF leak and postoperative infection. By comparing sandwich technique and single-layer dural sealing, no significant difference could be shown.

Human Vagus Nerve Branching in the Cervical Region

Background Vagus nerve stimulation is increasingly applied to treat epilepsy, psychiatric conditions and potentially chronic heart failure. After implanting vagus nerve electrodes to the cervical vagus nerve, side effects such as voice alterations and dyspnea or missing therapeutic effects are observed at different frequencies. Cervical vagus nerve branching might partly be responsible for these effects. However, vagus nerve branching has not yet been described in the context of vagus nerve stimulation. Materials and Methods Branching of the cervical vagus nerve was investigated macroscopically in 35 body donors (66 cervical sides) in the carotid sheath. After X-ray imaging for determining the vertebral levels of cervical vagus nerve branching, samples were removed to confirm histologically the nerve and to calculate cervical vagus nerve diameters and cross-sections. Results Cervical vagus nerve branching was observed in 29% of all cases (26% unilaterally, 3% bilaterally) and proven histologically in all cases. Right-sided branching (22%) was more common than left-sided branching (12%) and occurred on the level of the fourth and fifth vertebra on the left and on the level of the second to fifth vertebra on the right side. Vagus nerves without branching were significantly larger than vagus nerves with branches, concerning their diameters (4.79 mm vs. 3.78 mm) and cross-sections (7.24 mm2 vs. 5.28 mm2). Discussion Cervical vagus nerve branching is considerably more frequent than described previously. The side-dependent differences of vagus nerve branching may be linked to the asymmetric effects of the vagus nerve. Cervical vagus nerve branching should be taken into account when identifying main trunk of the vagus nerve for implanting electrodes to minimize potential side effects or lacking therapeutic benefits of vagus nerve stimulation.