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At least 127 records · Page 7Linked to original sources
PubMed2003

Neuronavigated repetitive transcranial magnetic stimulation in patients with tinnitus: a short case series.

BACKGROUND: Clinical as well as neurophysiological and neuroimaging data suggest that chronic tinnitus resembles neuropsychiatric syndromes characterized by focal brain activation. Low-frequency repetitive transcranial magnetic stimulation (rTMS) has been proposed as an efficient method in treating brain hyperexcitability disorders by reducing cortical excitability. METHODS: In three patients suffering from chronic tinnitus, the effect of magnetic resonance imaging and positron emission tomography guided neuronavigated 1 Hz rTMS on auditory cortex activity was evaluated, using a sham controlled double-blind crossover design. RESULTS: Two of three patients revealed clearly increased metabolic activity in circumscript areas of the primary auditory cortex (PAC), allowing a selective stimulation of these cortical areas with low-frequency rTMS. Considerable improvement in tinnitus was achieved in these patients. CONCLUSIONS: Neuronavigated rTMS of increased PAC activity may help to better understand the neuronal basis of chronic tinnitus and might offer a new option for treating auditory phantom perceptions like chronic tinnitus.

Auditory Cortex↗
PubMed2001

In vivo 3D visualization of normal pyramidal tracts in human subjects using diffusion weighted magnetic resonance imaging and a neuronavigation system.

We describe the potential of anisotropic diffusion weighted imaging to visualize the course of large cerebral fiber tracts. Five healthy volunteers were investigated at a field strength of 1.5 Tesla, employing a spin-echo diffusion weighted sequence with gradient sensitivity in six non-collinear directions to visualize the course of the pyramidal tracts. The pyramidal tracts were segmented and reconstructed for three-dimensional visualization. Reconstruction results together with a fusioned high resolution 3D T1 weighted image data set were available in a customized neuronavigation system. Origination in the primary motor cortex, convergence in the centrum semiovale, the posterior limb of the internal capsule, the cerebral peduncles, the splitting at the level of the pons, and the pyramidal decussation were identified in all subjects. Fiber tract maps might have the prospect of guiding neurosurgical interventions, especially when being linked to a neuronavigation system. Other potential applications include the demonstration of the anatomical substrate of functional connectivity in the human brain.

Adult↗
PubMed1997

Technical accuracy of a neuronavigation system measured with a high-precision mechanical micromanipulator.

OBJECTIVE: This study was designed to determine and evaluate the different system-inherent sources of erroneous target localization of a light-emitting diode (LED)-based neuronavigation system (StealthStation, Stealth Technologies, Boulder, CO). METHODS: The localization accuracy was estimated by applying a high-precision mechanical micromanipulator to move and exactly locate (+/- 0.1 micron) the pointer at multiple positions in the physical three-dimensional space. The localization error was evaluated by calculating the spatial distance between the (known) LED positions and the LED coordinates measured by the neuronavigator. The results are based on a study of approximately 280,000 independent coordinate measurements. RESULTS: The maximum localization error detected was 0.55 +/- 0.29 mm, with the z direction (distance to the camera array) being the most erroneous coordinate. Minimum localization error was found at a distance of 1400 mm from the central camera (optimal measurement position). Additional error due to 1) mechanical vibrations of the camera tripod (+/- 0.15 mm) and the reference frame (+/- 0.08 mm) and 2) extrapolation of the pointer tip position from the LED coordinates of at least +/- 0.12 mm were detected, leading to a total technical error of 0.55 +/- 0.64 mm. CONCLUSIONS: Based on this technical accuracy analysis, a set of handling recommendations is proposed, leading to an improved localization accuracy. The localization error could be reduced by 0.3 +/- 0.15 mm by correct camera positioning (1400 mm distance) plus 0.15 mm by vibration-eliminating fixation of the camera. Correct handling of the probe during the operation may improve the accuracy by up to 0.1 mm.

Evaluation Studies as Topic↗
PubMed2002

Use of neuronavigation and electrophysiology in surgery of subcortically located lesions in the sensorimotor strip.

OBJECTIVES: Subcortical lesions in the sensorimotor strip are often considered to be inoperable. The purpose of this study was to evaluate the usefulness of a combined approach for surgery in this region, aided by a robotic neuronavigation system under electrophysiological control. METHODS: In a prospective study on 10 patients, space occupying lesions in the sensorimotor central area were removed using the Surgiscope robotic navigation system and the Nicolet Viking IV electrophysiological system. RESULTS: Precise tumour localisation with the neuronavigation system and the information on the patient's cortical motor distribution obtained by bipolar cortical stimulation led to postoperative improvement in motor function in all but one patient. Seven of the patients had focal, defined pathology (four metastases; two cavernoma; one aspergilloma). CONCLUSION: Due to the implementation of two recent technologies, surgery of lesions in the subcortical sensorimotor region can be performed with greater confidence.

Adult↗
PubMed1999

Experiences with cranial neuronavigation in pediatric neurosurgery.

Frameless, infrared-based neuronavigation (Surgical Microscope Navigator and Surgical Tool Navigator) was applied to intracranial neurosurgery in 22 children and infants (age range 7 months to 16 years). Predominant diagnoses were tumor and hydrocephalus (including multiloculated forms); the surgical procedures were open microneurosurgery in 10 cases and neuroendoscopy in 12 patients. There were no principal technical problems even in very young infants. Surgical and clinical results were satisfying in all cases. Neuronavigation proved to be particularly helpful in targeting deep-seated processes and in guiding neuroendoscopy in cases of multiloculated hydrocephalus or small ventricles.

Adolescent↗
PubMed1997

Can neuronavigation contribute to standardization of selective amygdalohippocampectomy?

Tailored selective amygdalohippocampal resections seem to be an interesting application for neuronavigation. The accuracy of freehand frameless neuronavigation was assessed in 28 patients for its ability to determine the hippocampal resection length, as compared to postoperative MRI. Brain collapse due to CSF displacement caused an expected error of navigation at the brain surface, but almost no error at the tentorial notch. Yet, the hippocampal resection length was overestimated by navigation to an extent of 3 +/- 2 mm. The discrepancy is explained by an anterior-posterior component of brain collapse in a tilted head. Horizontal positioning of the head or navigational marking prior to the occurrence of brain collapse may overcome the problem.

Adult↗
PubMed1998

Postimaging brain distortion: magnitude, correlates, and impact on neuronavigation.

OBJECT: This prospective study was conducted to quantify brain shifts during open cranial surgery, to determine correlations between these shifts and image characteristics, and to assess the impact of postimaging brain distortion on neuronavigation. METHODS: During 48 operations, movements of the cortex on opening, the deep tumor margin, and the cortex at completion were measured relative to the preoperative image position with the aid of an image-guidance system. Bone surface offset was used to assess system accuracy and correct for registration errors. Preoperative images were examined for the presence of edema and to determine tumor volume, midline shift, and depth of the lesion below the skin surface. Results were analyzed for all cases together and separately for four tumor groups: 13 meningiomas, 18 gliomas, 11 nonglial intraaxial lesions, and six skull base lesions. For all 48 cases the mean shift of the cortex after dural opening was 4.6 mm, shift of the deep tumor margin was 5.1 mm, and shift of the cortex at completion was 6.7 mm. Each tumor group displayed unique patterns of shift, with significantly greater shift at depth in meningiomas than gliomas (p = 0.007) and significantly less shift in skull base cases than other groups (p = 0.003). Whereas the preoperative image characteristics correlating with shift of the cortex on opening were the presence of edema and depth of the tumor below skin surface, predictors of shift at depth were the presence of edema, the lesion volume, midline shift, and magnitude of shift of the cortex on opening. CONCLUSIONS: This study quantified intraoperative brain distortion, determined the different behavior of tumors in four pathological groups, and identified preoperative predictors of shift with which the reliability of neuronavigation may be estimated.

Adolescent↗
PubMed2002

Integration of sulcal and functional information for multimodal neuronavigation.

OBJECT: The authors present the use of cortical sulci, segmented from magnetic resonance (MR) imaging, and functional data from functional (f)MR imaging and magnetoencephalography (MEG) in the image-guided surgical management of lesions adjacent to the sensorimotor cortex. METHODS: In an initial set of 11 patients, sulci near lesions were automatically segmented from MR imaging data sets, then MEG and fMR imaging examinations were performed. Relevant functional information was preoperatively interpreted and selected from MEG and fMR imaging and subsequently transferred to the navigation system for selected sulci. A neuronavigation system consisting of a surgical microscope with enhanced reality overlay display was used. Data were displayed as contours on the cut-plane images of a stereotactic workstation and as contours on the overlay screen of the head-up display within the optical path of the right eyepiece of the surgical microscope. CONCLUSIONS: This method, in which both sulcal and functional mapping are used for surgery planning and neuronavigation, provides helpful information. It is a promising procedure for the treatment of patients who harbor lesions in areas around the eloquent cortex.

Adult↗
PubMed2000

[Treatment of central and neuropathic facial pain by chronic stimulation of the motor cortex: value of neuronavigation guidance systems for the localization of the motor cortex].

Thirty two patients with refractory central and neuropathic pain of peripheral origin were treated by chronic stimulation of the motor cortex between May 1993 and January 1997. The mean follow-up was 27. 3 months. The first 24 patients were operated according to the technique described by Tsubokawa. The last 13 cases (8 new patients and 5 reinterventions) were operated by a technique including localization by superficial CT reconstruction of the central region and neuronavigator guidance. The position of the central sulcus was confirmed by the use of intraoperative somatosensory evoked potentials. The somatotopic organisation of the motor cortex was established peroperatively by studying the motor responses at stimulation of the motor cortex through the dura. Ten of the 13 patients with central pain (77%) and nine of the 12 patients with neuropathic facial pain had experienced substantial pain relief (75%). One of the 3 patients with post-paraplegia pain was clearly improved. A satisfactory result was obtained in one patient with pain related to plexus avulsion and in one patient with pain related to intercostal herpes zoster. None of the patients developed epileptic seizures. The position of the stimulating poles effective on pain corresponded to the somatotopic representation of the motor cortex. The neuronavigator localization and guidance technique proved to be most useful identifying the appropriate portion of the motor gyrus. It also allowed the establishment of reliable correlations between electrophysiological-clinical and anatomical data which may be used to improve the clinical results and possibly to extend the indications of this technique.

Adult↗
PubMed2001

A comparative statistical analysis of neuronavigation systems in a clinical setting.

The use of neuronavigation (NN) in neurosurgery has become ubiquitous. A growing number of neurosurgeons are utilizing NN for a wide variety of purposes, including optimizing the surgical approach (macrosurgery) and locating small areas of interest (microsurgery). The goal of our team is to apply rapid advances in hardware and software technology to the field of NN, challenging and ultimately updating current NN assumptions. To identify possible areas in which new technology may improve the surgical applications of NN, we have assessed the accuracy of neuronavigational measurements in the Radionics and BrainLab systems. Using a phantom skull, we measured how accurate the visualization of a navigational probe's tip was in these systems, taking a total of 2180 measurements. We found that, despite current NN tenets, error is maximal at the six marker count and minimal in the spreaded marker setting; that is, placing less markers around the area of interest maximizes accuracy and active tracking does not necessarily increase accuracy. Comparing the two systems, we also found that accuracy of NN machines differs both overall and in different axes. As researchers continue to apply technological advances to the NN field, an increasing number of currently held tenets will be revised, making NN an even more useful tool in neurosurgery.

Factor Analysis, Statistical↗
PubMed2003

Intraoperative imaging in a comprehensive neuronavigation environment for minimally invasive brain tumour surgery.

BACKGROUND: Development of an image-guided operation theatre offering multimodal information for mini-invasive neurosurgical brain tumour operations. METHODS: A multi-purpose resistive low-field MR scanner with on-off capability, was installed in a radio frequency-shielded operating room with in-room control panel and display. Intraoperative ultrasound imaging with Doppler mode as needed is used to provide check-up image data between intraoperative MR-imaging sessions. Cortical stimulation and registration are performed during awake craniotomies. The neuronavigation systems are customised arm-based and passive optical. The navigation systems show the positions of the ultrasound probe, cortical stimulation electrode, biopsy needles, endoscope and other instruments on the intraoperative MR-images. FINDINGS: Since 1999, 70 patients (mean age 47, range 3-88 years) have been operated with intraoperative MR-guidance (including 10 tumour biopsies, 56 resections). Twenty-one patients (mean age 46, range 16-67 years) underwent awake craniotomy and tumour resection secured with cortical stimulation and usually preoperative fMR-imaging. The present operating environment offered useful multimodal information for surgery of brain tumours in critical locations. Surgical mortality was 0%, morbidity included 3 (4.3%) infections and 2 (2.9%) permanent hemiparesis. Further removal of tumour was continued in 17 cases (57%) out of the 30 cases where intraoperative MR imaging was used for controlling completeness of the resection.

Adolescent↗
PubMed2004

Successful resection of a left insular cavernous angioma using neuronavigation and intraoperative language mapping.

Despite recent literature advocating the surgical removal of symptomatic Cavernous Angiomas (CA), even in critical brain areas, very few observations of insular CA surgery have been described, particularly in the left hemisphere. We report the case of a successful resection of a CA located in the dominant insula, using both neuronavigation and intra-operative functional mapping. This 33-year-old right-handed man harbored a left insular CA, revealed by generalized seizures following a bleed confirmed on MRI. The preoperative examination was normal. A stereotactic-guided surgery was performed under local anesthesia, with intra-operative functional mapping using direct cortico-subcortical electrical stimulation in the awake patient--allowing the surgeon to achieve total resection of both CA and pericavernomatous gliosis, as shown on repeated postoperative MRIs. There was no postsurgical deficit, nor any seizure without treatment (follow-up: 4.5 years). The diagnosis of CA was confirmed by histological examination. Taking account of the risk of morbidity due to the natural history of CA, particularly in eloquent brain regions, we suggest to routinely consider the possibility of a surgical treatment in cases of symptomatic (left dominant) insular CA, using combined intra-operative anatomical and physiological localization methods.

Adult↗
PubMed2005

Fiber-tracking does not accurately estimate size of fiber bundle in pathological condition: initial neurosurgical experience using neuronavigation and subcortical white matter stimulation.

The fiber-tracking method enables in vivo visualization of the white matter tracts of the brain using a diffusion tensor MR imaging technique. While this method represents a promising tool in the field of neurosurgery, especially when confronted with brain tumors in eloquent areas, its reliability remains unknown. We present here our preliminary validation of tractography in human subjects harboring brain tumors by comparing the results produced by neuronavigation and electrical white matter stimulation in two patients with gliomas in the eloquent area. Although we were able to visualize the pyramidal tract with the fiber-tracking technique, the images failed to present the actual size of the fiber bundles. Here we discuss the advantages and limitations of fiber-tracking in the field of neurosurgery.

Aged↗
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↗
PubMed2003

Updating of neuronavigation based on images intraoperatively acquired with a mobile computerized tomographic scanner: technical note.

Image-guided surgery based on preoperatively obtained image data is susceptible to inaccuracy resulting from intraoperative brain shift and distortion. We report a technique of updating neuronavigational data with the aid of a mobile computerized tomographic (CT) scanner. A mobile CT which is readily available in an ordinary operating room was used to acquire intraoperative images. A total of 6 - 7 titanium screws placed on the skull were used as new reference points for updating navigation. Intraoperative CT scanning was performed with a 2 mm slice thickness. After the obtained image data were transferred as Dicom files to the computer workstation of the navigation system through an Ethernet connection, navigational data were updated to registering the new reference points. Under the guidance of the updated navigation, residual lesions were explored, and further resected. Our preliminary experience in 8 patients indicates that interactive image-guidance can stably be updated based on images intraoperatively acquired with a mobile CT scanner. Comparing to intraoperative magnetic resonance imaging, this technique can simply be done in an ordinary operating room without requiring special surgical instruments, thus making it possible to update interactive image guidance on demand during an operation.

Adult↗
PubMed2003

Neuronavigation based on CT angiography for surgery of intracranial aneurysms: primary experience with unruptured aneurysms.

Several reports have demonstrated the use of three-dimensional (3D) computed tomographic angiography (CTA) for preoperative planning in patients with intracranial aneurysms. Until now, there are no reports on the potential role of navigation systems in combination with CTA in aneurysm surgery. In the present study we report our experience with neuronavigation based on CTA in 16 patients with unruptured anterior circulation aneurysms for 1) planning craniotomy; 2) guided approach to the aneurysm; and 3) 3D presentation of the aneurysm and adjacent arteries in correct orientation. The reconstructed CTA images were analyzed preoperatively with regard to diameter of aneurysm neck and dome as well as projection and possible daughter aneurysms, and these parameters were compared with the intraoperative findings. In addition the accuracy of the navigator to locate the aneurysm neck was measured intraoperatively. Navigated approach planning resulted in variable keyhole craniotomies for the 7 middle cerebral artery aneurysms, but did not result in deviation from small standard craniotomies for the internal carotid and anterior communicating artery aneurysms. Precision of the indication of the navigator with regard to the aneurysm neck ranged from < 1 mm to 4 mm. Intraoperative assessment confirmed the CTA data with regard to aneurysm size and projection in all, and definition of daughter aneurysms and adjacent arteries in most cases. The computer assisted approach allowed a smaller, exactly placed craniotomy primarily in MCA aneurysms. 3D presentation of the aneurysms and the adjacent arteries in correct orientation facilitated identification and dissection the aneurysms. Current navigation systems are not precise enough to allow "blind" aneurysm clipping by placing a real clip on the virtual aneurysm neck.

Adult↗
PubMed2005

Integrated neuronavigation system with intraoperative image updating.

OBJECTIVE: Recently, MRI has entered the field of image-guided surgery as a new intraoperative imaging modality. In spite of its obvious benefits, this type of iMRI scanner has some drawbacks that have limited its utilization. The goal of the work presented here was to overcome some of these disadvantages. METHODS: A system that allows intraoperative images to be acquired during surgery and have the ability to conduct surgery outside the constraints of the narrow gap of the open magnet was implemented. Ability to conduct tasks inside the scanner with real-time image guidance was also maintained. The system allowed navigation with neuronavigation tools both inside the gap of an open magnet and outside the magnet, utilizing two different optical camera-sets and a dynamic reference frame. Automatic patient registration was implemented. RESULTS: The average difference between tracking position measured outside and inside the magnet was 0.8 +/- 0.1 mm. CONCLUSION: In the work presented in this note we have introduced a dynamic reference frame to compensate for transport of the patient to a location outside the scanner employing a second camera set. The integrated system showed adequate accuracy.

Equipment Design↗
PubMed2003

Experimental third ventriculostomy performed using endovascular surgical techniques and their adaptation to percutaneous intradural neuronavigation: proof of concept cadaver study.

OBJECTIVE: Endoscopic third ventriculostomy has developed into a therapeutic alternative to shunting for the management of carefully selected patients with primarily noncommunicating hydrocephalus. This procedure, however, requires a general anesthetic and necessitates violation of the brain parenchyma and manipulation near vital neural structures to access the floor of the third ventricle. Using two cadavers and off-the-shelf angiographic catheters, we sought to determine whether it was possible to navigate a catheter, angioplasty balloon, and stent percutaneously through the subarachnoid space from the thecal sac into the third ventricle so as to perform a third ventriculostomy from below. METHODS: Using biplane angiography and off-the-shelf angiographic catheters along with angioplasty balloons and stents, we were able to pass a stent coaxially from the thecal sac to and across the floor of the third ventricle so as to achieve a third ventriculostomy from below. RESULTS: Coaxial catheter techniques allowed for the percutaneous insertion of a stent across the floor of the third ventricle. Ventriculostomy was confirmed by injecting contrast medium into the lateral ventricle and seeing it pass through the stent and into the chiasmatic cistern. CONCLUSION: We describe the performance of third ventriculostomies in two cadavers by use of the new concept of percutaneous intradural neuronavigation. This procedure may obviate the need for general anesthetic and minimize the potential for brain and vascular injury, especially if ultimately combined with magnetic resonance fluoroscopy.

Adult↗