Biomedical subjects

O Ganslandt

Publications and source records attributed to O Ganslandt.

At least 19 recordsLinked to original sources

PubMed2003

Glioma surgery evaluated by intraoperative low-field magnetic resonance imaging.

OBJECTIVE: To give an overview on intraoperative magnetic resonance (MR) imaging in glioma surgery. MATERIAL AND METHODS: MR imaging was performed using a 0.2T scanner, located in a radiofrequency-shielded operating theatre. Two setups were used: surgery either in a neighbouring operating theatre, or directly at the 5G line. Additionally, in gliomas adjacent to eloquent brain areas microscope- or pointer-based neuronavigation with integrated functional data was applied. 106 gliomas were among the 330 patients investigated in the last 5 years. RESULTS: We did not observe complications attributable to intraoperative MR imaging. Image quality was sufficient to evaluate the extent of the tumour resection in the majority of cases. Intraoperative imaging revealed remaining tumour in 63%. In a total of 26% patients further tumour could be removed due to the results of intraoperative imaging, increasing the rate of complete tumour removal especially in the low-grade tumours. The additional use of functional neuronavigation prevented an increased morbidity. CONCLUSION: Intraoperative MR imaging offers the possibility of further tumour removal during the same surgical procedure in case of tumour remnants, increasing the rate of complete tumour removal. The effects of brain shift can be compensated for using intraoperative image data for updating.

Adolescent↗

PubMed2003

Simple invasive fixation device for fractionated stereotactic LINAC based radiotherapy.

BACKGROUND: The aim of this study was to develop a relocatable fixation device for linear accelerator (LINAC) based fractionated stereotactic radiotherapy. METHOD: The device consists of a CT- and MRI-compatible stereotactic frame, monocortical titan bone screws, four frame-posts with a lock for the fixation pins and a modified head clamp with additional arms that allows the exact and rigid placement of the frame in the desired final position prior to the final placement of the bone screws. By simply disconnecting the lock from the posts, the frame can be dismounted after treatment planning and after each treatment session. The accuracy of reposition was assessed prospectively, using phantom studies and also by comparison of isocenter movements during fractionated radiotherapy in 10 patients with an intracranial lesion. FINDINGS: No adverse events were seen after the surgical procedure and the screws were well tolerated throughout the course of treatment. The mean isocenter shifts observed during phantom reposition studies were x=0.05 mm, y=-0.32 mm, z=0.18 mm and the mean isocenter shifts during fractionated treatment were x=0.67 mm, y=0.65 mm, z=0.44 mm. INTERPRETATION: This new fixation device provides excellent accuracy of reposition during stereotactic radiotherapy. It appears superior to non-invasive, mask fixation techniques. Safety margins as small as 1-1.5 mm may therefore be sufficient for this method of stereotactic radiotherapy.

Adult↗

PubMed2003

Image-guided removal of supratentorial cavernomas in critical brain areas: application of neuronavigation and intraoperative magnetic resonance imaging.

In a retrospective study the postoperative results of 26 patients operated on for supratentorial cavernous hemangiomas either deep-seated or near eloquent brain areas are summarized. An exact surgical approach to these lesions is essential to prevent neurological deterioration. Three different navigation systems were used and compared according to their clinical applicability. Complete removal of the lesion was obtained in all patients of this series. In six cases (23 %) functional data from magnetoencephalography or functional magnetic resonance imaging were integrated into the navigational setup. In 14 cases (54 %) intraoperative magnetic resonance imaging was performed. The follow-up time was 3 - 26 months (mean: 10 months). In the postoperative course one patient (3.8 %) developed a hemiparesis, another one developed quadrantopia. Nineteen patients presented with preoperative seizure history, 16 of these (84 %) had no further or rare seizures after surgery. The better results in seizure control were achieved in those patients with shorter duration of seizure history before surgery. The study indicates that the application of neuronavigation allows surgery on supratentorial cavernous hemangiomas in critical brain areas with low morbidity. The intraoperative visualization of eloquent cortex areas by integration of functional data allows a fast identification and exemption of eloquent brain areas, preventing neurological deterioration. Furthermore, the intraoperative MR resection control ensures a complete resection and illustrates the minimal invasive approach.

Adolescent↗

PubMed2002

Fractionated stereotactically guided radiotherapy of pharmacoresistant temporal lobe epilepsy.

PURPOSE: This prospective study evaluated the efficacy of fractionated stereotactically guided radiotherapy (SRT) as a treatment of pharmacoresistant temporal lobe epilepsy. PATIENTS AND METHODS: Inclusion criteria were patients aged between 17 and 65 years with unilateral temporal focus, without sufficient epilepsy control by antiepileptic drugs or neurosurgery. Two groups of 6 patients each were treated with 21 Gy (7 times 3 Gy) and 30 Gy (15 times 2 Gy). Study end points were change in seizure frequency, intensity, seizure length and neuropsychological parameters. RESULTS: All patients experienced a marked reduction in seizure frequency. The mean reduction of seizures was 37% (range 9-77%, i.e. seizures reduced from a monthly mean number of 11.75 to 7.52) at 18 months following radiation treatment and 46% (23-94%, i.e. 0.2-23 seizures per month) during the whole follow-up time. Seizure length was reduced in 5 out of 11 patients and intensity of seizures in 7 out of 11 patients. CONCLUSION: Radiotherapy was identified as a safe and effective treatment for pharmacoresistant epilepsy since a good reduction of seizure frequency during longer follow-up was observed. SRT means an appropriate alternative for patients with contraindication against neurosurgery or insufficient seizure reduction after neurosurgery.

Adolescent↗

PubMed2002

[Use of magnetoencephalography and functional neuronavigation in planning and surgery of brain tumors].

The role of magnetoencephalography (MEG) in neurology has been established for basic research, epilepsy, and functional brain mapping. The presurgical localization of functionally important brain areas has evolved as an important application of MEG. Both neurologists and neurosurgeons can use this method for decision-making and planning of nonsurgical or surgical treatment in brain tumors. The integration of functional brain mapping data into neuronavigation systems may help to minimize postoperative morbidity. This is especially important in low-grade gliomas, in which a potential benefit of surgery is only achieved when the tumor has been resected completely, whereas neurological deterioration means a substantial loss of quality of life during the survival time. This report addresses the utility of MEG combined with neuronavigation in the treatment of brain tumors adjacent to eloquent brain areas.

Adolescent↗

PubMed2002

Localisation of the sensorimotor cortex during surgery for brain tumours: feasibility and waveform patterns of somatosensory evoked potentials.

OBJECTIVE: Intraoperative localisation of the sensorimotor cortex using the phase reversal of somatosensory evoked potentials (SEPs) is an essential tool for surgery in and around the perirolandic gyri, but unsuccessful and perplexing results have been reported. This study examines the effect of tumour masses on the waveform characteristics and feasibility of SEP compared with functional neuronavigation and electrical motor cortex mapping. METHODS: In 230 patients with tumours of the sensorimotor region the SEP phase reversal of N20-P20 was recorded from the exposed cortex using a subdural grid or strip electrode. In one subgroup of 80 patients functional neuronavigation was performed with motor and sensory magnetic source imaging and in one subgroup of 40 patients the motor cortex hand area was localised by electrical stimulation mapping. RESULTS: The intraoperative SEP method was successful in 92% of all patients, it could be shown that the success rate rather depended on the location of the lesion than on preoperative neurological deficits. In 13% of the patients with postcentral tumours no N20-P20 phase reversal was recorded but characteristic polyphasic and high amplitude waves at 25 ms and later made the identification of the postcentral gyrus possible nevertheless. Electrical mapping of the motor cortex took up to 30 minutes until a clear result was obtained. It was successful in 37 patients, but failed in three patients with precentral and central lesions. Functional neuronavigation indicating the tumour margins and the motor and sensory evoked fields was possible in all patients. CONCLUSION: The SEP phase reversal of N20-P20 is a simple and reliable technique, but the success rate is much lower in large central and postcentral tumours. With the use of polyphasic late waveforms the sensorimotor cortex may be localised. By contrast with motor electrical mapping it is less time consuming. Functional neuronavigation is a desirable tool for both preoperative surgical planning and intraoperative use during surgery on perirolandic tumours, but compensation for brain shift, accuracy, and cost effectiveness are still a matter for discussion.

Adolescent↗

PubMed2002

Neuronavigation: concept, techniques and applications.

Neuronavigation provides intraoperative orientation to the surgeon, helps in planning a precise surgical approach to the targetted lesion and defines the surrounding neurovascular structures. Incorporation of the functional data provided by functional MRI and magnetoencephalography (MEG) with neuronavigation helps to avoid the eloquent areas of the brain during surgery. An intraoperative MRI enables radical resection of the lesions, the possibility of immediate control for tumor remnants and updates of neuronavigation with intraoperative images to compensate for brain shift. In this study, the experience of 432 patients undergoing neuronavigation assisted neurosurgical interventions using either the pointer-based or microscope-based navigational systems at the University of Erlangen-Nuremberg, Germany is presented. The procedures included stereotactic biopsy (n=53), stereotactic cyst puncture/ventricular drainage (n=15), eloquent cortex/tumor localization to facilitate tumor resection, assessment of neurovascular structures in the vicinity of tumors of the sellar-suprasellar regions, skull base, posterior fossa and ventricular region (n=252), and, surgery for epilepsy (n=9). Functional brain mapping using fMRI and MEG and their integration with neuronavigation was carried out in 24 and 128 patients respectively. The simultaneous use of intraoperative MRI to look for the remaining tumor was done in 159 patients and the update of navigational data was carried out in 17 patients. The mean system accuracy obtained by using both the fiducial registration as well as anatomical landmark-surface fitting computer algorithm was 1.81 mm. This study reviews the relative merits and demerits of the pointer and microscope based navigational systems and also highlights the role of functional brain mapping and intraoperative MRI, when integrated with neuronavigation, in the surgical decision-making to offer the chances of more radical resections with minimal morbidity.

Adolescent↗

PubMed2001

A combined study of tumor-related brain lesions using MEG and proton MR spectroscopic imaging.

The purpose of this study is to localize, in cases of brain tumors, pathological magnetic brain activities and to analyze metabolic alterations in functionally abnormal lesions using magnetoencephalography (MEG) and proton magnetic resonance spectroscopic imaging (1H MRSI). The study focused on 10 healthy volunteers and seven patients with common brain tumors, namely astrocytic tumor and meningioma. In spontaneous MEG, the pathological brain activities (slow, fast waves and spikes) were localized using a single equivalent dipole model. After the results of MEG and 1H MRSI were superimposed onto the corresponding MR images, the signal intensities of spectroscopically visible metabolites were analyzed in the regions where the dipoles of the pathological activities were concentrated. Increased slow wave activity was observed in four cases and fast wave or spike activity was significantly increased in one case. These pathological activities were localized in surrounding regions of the bulk of tumors, where mild reduction of N-acetyl aspartate (NAA) and slight accumulation of lactate (Lac) consistently existed. Preserved cortical areas, which are indicated by residual NAA, might be able to generate pathological magnetic activities under lactic acidosis. Such areas could be understood as a border zone between normal and seriously damaged brain tissue by tumors or associated brain edema. This combined technique with the different modalities gives insight into functional as well as metabolic aspects of pathological brain conditions.

Adult↗

PubMed2001

New approach to localize speech relevant brain areas and hemispheric dominance using spatially filtered magnetoencephalography.

We used a current localization by spatial filtering-technique to determine primary language areas with magnetoencephalography (MEG) using a silent reading and a silent naming task. In all cases we could localize the sensory speech area (Wernicke) in the posterior part of the left superior temporal gyrus (Brodmann area 22) and the motor speech area (Broca) in the left inferior frontal gyrus (Brodmann area 44). Left hemispheric speech dominance was determined in all cases by a laterality index comparing the current source strength of the activated left side speech areas to their right side homologous. In 12 cases we found early Wernicke and later Broca activation corresponding to the Wernicke-Geschwind model. In three cases, however, we also found early Broca activation indicating that speech-related brain areas need not necessarily be activated sequentially but can also be activated simultaneously. Magnetoencephalography can be a potent tool for functional mapping of speech-related brain areas in individuals, investigating the time-course of brain activation, and identifying the speech dominant hemisphere. This may have implications for presurgical planning in epilepsy and brain tumor patients.

Adult↗

PubMed2001

Correlation of sensorimotor activation with functional magnetic resonance imaging and magnetoencephalography in presurgical functional imaging: a spatial analysis.

In this study we investigated the spatial heterotopy of MEG and fMRI localizations after sensory and motor stimulation tasks. Both methods are frequently used to study the topology of the primary and secondary motor cortex, as well as a tool for presurgical brain mapping. fMRI was performed with a 1.5T MR system, using echo-planar imaging with a motor and a sensory task. Somatosensory and motor evoked fields were recorded with a biomagnetometer. fMRI activation was determined with a cross-correlation analysis. MEG source localization was performed with a single equivalent current dipole model and a current density localization approach. Distances between MEG and fMRI activation sites were measured within the same anatomical 3-D-MR image set. The central region could be identified by MEG and fMRI in 33 of 34 cases. However, MEG and fMRI localization results showed significantly different activation sites for the motor and sensory task with a distance of 10 and 15 mm, respectively. This reflects the different neurophysiological mechanisms: direct neuronal current flow (MEG) and secondary changes in cerebral blood flow and oxygenation level of activated versus non activated brain structures (fMRI). The result of our study has clinical implications when MEG and fMRI localizations are used for pre- and intraoperative brain mapping. Although both modalities are useful for the estimation of the motor cortex, a single modality may err in the exact topographical labeling of the motor cortex. In some unclear cases a combination of both methods should be used in order to avoid neurological deficits.

Adolescent↗

PubMed2001

Intraoperative compensation for brain shift.

BACKGROUND: Tumor removal, brain swelling, the use of brain retractors, and cerebrospinal-fluid drainage all result in an intraoperative brain deformation that is known as brain shift. Thus, neuronavigation systems relying on preoperative image data have a decreasing accuracy during the surgical procedure. Intraoperative image data represent the correct anatomic situation, so their use may compensate for the effects of brain shift. METHODS: In a series of 16 brain tumor patients, we used intraoperative magnetic resonance (MR) imaging to obtain 3-D data, which were then transferred to the microscope-based neuronavigation system. With the help of bone fiducial markers these images were registered intraoperatively, updating the neuronavigation system. RESULTS: In all patients the updating of the neuronavigation system with the intraoperative MR data was successful. It led to reliable neuronavigation with high accuracy; the mean registration error of the update procedure in all patients was 1.1 mm. The updating procedure added about 15 minutes to the operation time. In all patients the area suggestive of remaining tumor was reached and the additional tumor could be resected, resulting in a complete tumor removal in 14 patients. In the remaining patients extension of the tumor into eloquent brain areas prevented a complete excision. CONCLUSIONS: The update of a neuronavigation system with intraoperative MR images reliably compensates for the effects of brain shift. This method allows completion of tumor removal in some difficult brain tumors.

Adolescent↗

PubMed2001

Intraoperative magnetic resonance imaging combined with neuronavigation: a new concept.

OBJECTIVE: Intraoperative image data may be used not only to evaluate the extent of a tumor resection but also to update neuronavigation, compensating for brain shift. To date, however, intraoperative magnetic resonance imaging (MRI) can be combined only with navigation microscopes that are separated from the magnetic field, thus requiring time-consuming intraoperative patient transport. To help solve this problem, we investigated whether a new navigation microscope can be used within the fringe field of the MRI scanner. METHODS: The navigation microscope was placed at the 5-G line of a 0.2 MRI device. Patients were positioned lying down directly on the table of the scanner, with their heads placed approximately 1.5 m from the center of the magnet, fixed in an MRI-compatible ceramic head holder. Standard operating instruments were used. For intraoperative imaging, we slid the table into the center of the magnet in less than 30 seconds. RESULTS: By use of this setup, we operated on 22 patients. In all patients, anatomic neuronavigation could be used in combination with intraoperative MRI. In addition, in 12 patients, functional data from magnetoencephalographic or functional MRI studies were integrated, resulting in functional neuronavigation. We did not encounter adverse effects of the low magnetic field during navigation. Moreover, intraoperative imaging was not disturbed by the navigation microscope and vice versa. CONCLUSION: Functional neuronavigation and intraoperative MRI can be used essentially simultaneously without the need for lengthy intraoperative patient transport. The combination of intraoperative imaging with functional neuronavigation offers the opportunity for more radical resections and fewer complications.

Adolescent↗

PubMed2001

Intraoperative magnetic resonance imaging during transsphenoidal surgery.

OBJECT: The aim of this study was to evaluate whether intraoperative magnetic resonance (MR) imaging can increase the efficacy of transsphenoidal microsurgery, primarily in non-hormone-secreting intra- and suprasellar pituitary macroadenomas. METHODS: Intraoperative imaging was performed using a 0.2-tesla MR imager, which was located in a specially designed operating room. The patient was placed supine on the sliding table of the MR imager, with the head placed near the 5-gauss line. A standard flexible coil was placed around the patient's forehead. Microsurgery was performed using MR-compatible instruments. Image acquisition was started after the sliding table had been moved into the center of the magnet. Coronal and sagittal T1-weighted images each required over 8 minutes to acquire, and T2-weighted images were obtained optionally. To assess the reliability of intraoperative evaluation of tumor resection, the intraoperative findings were compared with those on conventional postoperative 1.5-tesla MR images, which were obtained 2 to 3 months after surgery. Among 44 patients with large intra- and suprasellar pituitary adenomas that were mainly hormonally inactive, intraoperative MR imaging allowed an ultra-early evaluation of tumor resection in 73% of cases; such an evaluation is normally only possible 2 to 3 months after surgery. A second intraoperative examination of 24 patients for suspected tumor remnants led to additional resection in 15 patients (34%). CONCLUSIONS: Intraoperative MR imaging undoubtedly offers the option of a second look within the same surgical procedure, if incomplete tumor resection is suspected. Thus, the rate of procedures during which complete tumor removal is achieved can be improved. Furthermore, additional treatments for those patients in whom tumor removal was incomplete can be planned at an early stage, namely just after surgery.

Adenoma↗

PubMed2000

Intraoperative magnetic resonance imaging in epilepsy surgery.

The aim of this study was to investigate how intraoperative magnetic resonance imaging (MRI) can help in epilepsy surgery to asses immediately whether a resection or disconnection procedure is tailored to the individual needs of a patient, thus ideally meeting the treatment plan and enhancing the efficiency of the procedure. The recently proposed concept of an individually tailored procedure with as limited tissue removal as possible would support a more conservative resection than initially advocated by many centers; such limited removal would preserve as much brain as possible that is not necessarily epileptogenic or involved in propagation of seizures. For intraoperative imaging we used a Magnetom Open 0.2-T scanner located in our "twin-OR" in 61 patients with pharmacoresistant epilepsy. A three-dimensional sequence was used, allowing free slice reformatting. In the nonlesional cases (n = 32) the extent of the tailored temporal resection (n = 28) or callosotomy (n = 4) could be documented exactly. In the 29 lesional cases the complete resection was primarily proved in 23 patients. In three glioma patients a lesion that extended into eloquent areas did not allow for complete removal. A second look (n = 3) could increase the rate of total resection in the lesional cases from 79% to 90%. Intraoperative MRI allowed a reliable evaluation of the extent of resection or disconnection in epilepsy surgery within the operative procedure. It also provided the possibility of a second look in cases of incomplete resection, especially in the lesional cases. Increased knowledge of structure-function relationships as partially defined by intraoperative imaging may reduce the adverse neuropsychological sequelae of epilepsy surgery in the future.

Adult↗

PubMed2000

Supratentorial low-grade glioma: results and prognostic factors following postoperative radiotherapy.

BACKGROUND AND PURPOSE: To assess treatment outcome and prognostic factors following postoperative external radiotherapy in 77 patients with low-grade glioma. PATIENTS AND METHODS: Between 1977 and 1996, 45 patients with astrocytoma, 14 with oligodendroglioma and 18 with mixed glioma received postoperative radiotherapy with a median total dose of 52 Gy (range, 45 to 61 Gy). Sixty-seven patients were treated immediately following surgery, 10 patients with tumor progression. The influence of various factors including histology, gender, age, seizures, duration of symptoms (< or = 6 weeks vs > 6 weeks), CT pattern (enhancement vs no enhancement), type of surgery, total radiotherapy dose and timing of radiotherapy on relapse-free survival and overall survival was investigated. RESULTS: The median overall survival time was 81 months, the 5- and 10-year survival rates were 54% and 31%, respectively. The median time to progression was 56 months, while the 5- and 10-year progression-free survival rates were 45% and 24%. Univariate analyses identified the total radiotherapy dose (p = 0.01), duration of symptoms (p = 0.05), the presence of seizures (p = 0.04), and the CT pattern following intravenous contrast (p = 0.005) as significant prognostic factors for overall survival. Progression-free survival rates were influenced by the total dose (p = 0.04), the duration of symptoms (p = 0.01) and CT pattern (p = 0.006). On multivariate analysis, only the CT pattern (enhancement vs no enhancement) remained as independent prognostic factors for both progression-free survival and overall survival. CONCLUSIONS: A minimum total dose of 52 Gy is recommended for the postoperative radiotherapy in low-grade glioma. Tumors with CT enhancement seem to need further intensification of treatment.

Adult↗

PubMed2000

[Intraoperative magnetic resonance tomography. Experiences with its use in neurosurgery].

Intraoperative magnetic resonance imaging using a 0.2 Tesla, open-configured scanner was applied in a total of 243 patients. The aim of this study was to evaluate the feasibility, clinical application, and indications of this method. No adverse effects of the intraoperative imaging could be observed. The extent of tumor resection could be evaluated in the majority of cases. Resection control in glioma, ventricular tumor, pituitary tumor, and epilepsy surgery were the main indications for the intraoperative application. Especially when combined with functional neuronavigation, intraoperative magnetic resonance imaging allowed more radical resectioning with lower morbidity. Second looks to complete tumor removal during the same surgical procedure were possible to determine tumor remnants. Brain shift, which reduces the accuracy of neuronavigational systems, could be compensated for by intraoperative updates.

Adolescent↗

PubMed2000

Intraoperative imaging with open magnetic resonance imaging and neuronavigation.

The Erlangen-concept of image-guided-surgery is based on the installation of an open magnetic resonance (MR) scanner (Magnetom Open, 0.2 T, Siemens AG) in a twin operating room in combination with two neuronavigation systems (Stealth NeuroStation, Sofamor Danek, MKM Zeiss). Since March 1996 this method has been used for a total of 402 patients, among them 44 children. In 214 patients, mainly with gliomas or pituitary adenomas or who needed surgery for epilepsy, we performed intraoperative MR imaging to monitor the extent of resection, allowing a second look for possible tumor remnants and also compensating for brain shift by an intraoperative update of neuronavigation. Functional neuronavigation, i.e. the combination of anatomical neuronavigation with functional imaging [e.g. magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI)] was used in patients with lesions in brain areas such as the motor and speech areas. For MEG we used a MAGNES II biomagnetometer (Biomagnetic Technologies, San Diego, Calif.) and for fMRI a 1.5 T Siemens Symphony MR scanner. So far we have treated 89 patients with functional neuronavigation. Our preliminary experience indicates that intraoperative MR imaging, especially in combination with functional neuronavigation, allows more radical resections with lower morbidity.

Adenoma↗

PubMed2000

Primary spinal germinoma in a patient with concomitant Klinefelter's syndrome.

It is known that patients with Klinefelter's syndrome are inclined to develop concomitant malignant tumours, as well as extragonadal germ cell tumours. The association of a primary spinal germinoma in a patient with Klinefelter's syndrome is reported for the first time, and the coincidence of elevated gonadotropin levels and oncogenesis is discussed.

Adult↗