Showing papers on "Neuronavigation published in 2010"

Comparison of “standard” and “navigated” procedures of TMS coil positioning over motor, premotor and prefrontal targets in patients with chronic pain and depression

Abstract: Since about 15 years, transcranial magnetic stimulation (TMS) is used as a technique to investigate the function of specific cortical regions. Single pulse TMS studies have targeted the dorsolateral premotor cortex (dlPMC) to characterize premotor-motor interactions in movement disorders. Repetitive TMS (rTMS) trials have targeted the dorsolateral prefrontal cortex (dlPFC) to treat depression. In almost all previous studies, these targets have been defined according to a "standard" scalp distance to the site of stimulation evoking motor responses of maximal amplitude in the contralateral hand ("hand motor hotspot" corresponding to the primary motor cortex, M1). The "standard" procedure of coil positioning locates the dlPMC and dlPFC as 2-3 and 5cm, respectively, anterior to the "hand motor hotspot". The aim of our study was to compare the locations of M1, dlPMC and dlPFC targets provided by the "standard" procedure of coil positioning and those provided by using a neuronavigation system integrating individual brain magnetic resonance imaging (MRI). Twenty-two patients were enrolled, all being treated for depressive symptoms in the context of chronic pain syndrome. The centers of the dlPMC and dlPFC regions were accurately targeted by the "standard" procedure in 14 and eight patients (64 and 36% of the series), respectively. In the other patients, the "standard" procedure located the dlPMC target on the M1/dlPMC border and the dlPFC target on the dlPMC/dlPFC border. On average, the MRI-guided location of M1, dlPMC, and dlPFC was, respectively, 6.1mm posterior, 31.7mm anterior and 69.0mm anterior to the "hand motor hotspot". The "standard" procedure failed to accurately locate the dlPMC and dlPFC targets by about 1 and 2cm, respectively. A statistical analysis of the MRI coordinates (x, y, z) of the targets revealed that the M1 target was more posterior, the dlPMC target more superficial and the dlPFC target more anterior, lateral, and deeper, using neuronavigation compared to the "standard" procedure. This study confirms that the "standard" procedure of coil positioning is not accurate to target a desired cortical region. Target location can be improved by the use of a navigation system taking individual brain anatomy into account. The present results incline to be cautious on the pathophysiological interpretations of previous results reported in TMS studies based on "standard" targeting, e.g. regarding premotor-motor interactions. Similarly, the inaccuracy of the "standard" procedure of coil positioning could partly explain the between-study variability of the therapeutic effects produced by rTMS in patients with depression. Our results strongly support a more anterior and lateral placement of the TMS coil for dlPFC stimulation in the treatment of depression.

Optimal transcranial magnetic stimulation coil placement for targeting the dorsolateral prefrontal cortex using novel magnetic resonance image-guided neuronavigation

Abstract: The dorsolateral prefrontal cortex (DLPFC) has been implicated in the pathophysiology of several psychiatric illnesses including major depressive disorder and schizophrenia. In this regard, the DLPFC has been targeted in repetitive transcranial magnetic stimulation (rTMS) studies as a form of treatment to those patients who are resistant to medications. The '5-cm method' and the '10-20 method' for positioning the transcranial magnetic stimulation (TMS) coil over DLPFC have been scrutinised due to poor targeting accuracies attributed to inter-subject variability. We evaluated the accuracy of such methods to localise the DLPFC on the scalp in 15 healthy subjects and compared them with our novel neuronavigational method, which first estimates the DLPFC position in the cortex based on a standard template and then determines the most appropriate position on the scalp in which to place the TMS coil. Our neuronavigational method yielded a scalp position for the left DLPFC between electrodes F3 and F5 in standard space and was closest to electrode F5 in individual space. Further, we found that there was significantly less inter-subject variability using our neuronavigational method for localising the DLPFC on the scalp compared with the '5-cm method' and the '10-20 method'. Our findings also suggest that the '10-20 method' is superior to the '5-cm method' in reducing inter-subject variability and that electrode F5 should be the stimulation location of choice when MRI co-registration is not available.

Endoscopic endonasal skull base surgery: past, present and future

Abstract: Endoscopic techniques have undergone tremendous advancement in the past years. From the management of phlogistic pathologies, we have learned to manage skull base lesions and even selected intracranial diseases. Current anatomical knowledge plus computer-aided surgery has enabled surgeons to remove large lesions in the paranasal sinuses extending beyond the boundaries of the sinuses themselves. In this sense, management of benign diseases via endoscopic routes is nowadays well accepted whilst the role of endoscopic techniques in sinonasal malignancies is still under investigation. Nowadays, it is possible to tackle different pathologies placed not only in the ventral skull base, but also extended laterally (infratemporal fossa and petrous apex) and even, in really selected cases, within the orbit. The ability to resect and reconstruct has improved significantly. At the moment, the improvement in surgical techniques, like the four-handed technique, has rendered endoscopic procedures capable of managing complex pathologies, according the same surgical principles of the open approaches. From now onwards, frameless neuronavigation, modular approaches, intraoperative imaging systems and robotic surgery are and will be an increasingly important part of endonasal surgery, and they will be overtaken by further evolution.

Functional magnetic resonance imaging and diffusion tensor tractography incorporated into an intraoperative 3-dimensional ultrasound-based neuronavigation system: impact on therapeutic strategies, extent of resection, and clinical outcome.

Abstract: High-grade gliomas are the most common primary brain tumour. Glioblastomas (World Health Organization Grade IV) and anaplastic astrocytomas (World Health Organization Grade III) account for 70-85% of high-grade gliomas. High-grade gliomas are associated with high morbidity and mortality. Virtually all patients with high-grade glioma will experience recurrence and will eventually die from progressing disease. Despite surgery, radiotherapy, and chemotherapy, median survival in patients with glioblastoma still does not exceed 12 months. The median survival for patients with anaplastic astrocytoma (AA) has been reported to be between 2 and 3 years. According to current guidelines, surgery is warranted to establish a histopathologic diagnosis and to achieve safe, maximal, and feasible resection. However, these aggressive tumours cannot be cured and overly aggressive resection is not recommended due to the risk of new neurological deficits. High-grade glioma surgery is a delicate balance between achieving maximal tumour resection and inducing new deficits.In our department a neuronavigation system based on preoperative 3D magnetic resonance imaging (MRI) and intraoperative 3D ultrasound is utilised when resecting high-grade gliomas. Blood-oxygenation-level-dependent functional magnetic resonance imaging (BOLD fMRI) and diffusion tensor tractography (DTT) are specialized MRI techniques for imaging eloquent cortices and neural tracts in grey and white matter, respectively. The neuronavigation system allows the integration of BOLD fMRI and DTT data if the tumours are located in eloquent regions.In the two first studies of this thesis we sought to investigate the use of BOLD fMRI and DTT for preoperative assessments and determine whether using these data together with 3D intraoperative ultrasound enabled safe resection of high-grade gliomas situated in eloquent regions. In the third study we wanted to explore the impact of surgical morbidity on functional outcome and survival in GBM patients. Further, we sought to determine extent of tumour resection achieved in a consecutive sample of primary GBM from our own department. In the fourth study we wanted to determine if changes in health related quality of life early after surgery could be a predictor for survival in patients with glioblastoma. The aims of the fifth study were to explore survival and the treatment provided to elderly patients (≥66 years) diagnosed with glioblastoma during a 20-year time period in a population-based cohort using the Norwegian Cancer Registry.This thesis investigated the role of surgical resection in the treatment of high-grade gliomas and the following conclusions can be drawn:- The combination of BOLD fMRI, DTT, and 3D intraoperative ultrasound may facilitate resection of high-grade gliomas harboured in eloquent areas while preserving motor and language function.- Functional neuronavigation combined with intraoperative 3D ultrasound can, in most patients, enable resection of brain lesions with general anaesthesia without jeopardizing neurological function.- Patients with perioperative complications and surgically acquired deficits were less likely to receive adjuvant therapy.- Early deterioration in HRQL after surgery was independently and markedly associated with impaired survival in patients with glioblastoma.- Advancing age remains a very strong and independent negative prognostic factor in glioblastoma. Although there has been an increase in the aggressiveness of treatment provided to elderly with glioblastoma, the gain for the oldest age group seems at best very modest. The prognosis of the oldest age group remains very poor, despite multimodal treatment.

Evaluation of Intraoperative Brain Shift Using an Ultrasound-Linked Navigation System for Brain Tumor Surgery

Abstract: Image-guided neurosurgery using navigation systems is an essential tool to increase accuracy in brain tumor surgery. However, brain shift during surgery has remained problematic. The present study evaluated the utility of a new ultrasound (US)-linked navigation system for brain tumor surgery in 64 patients with intracranial tumors. The navigation system consisted of a StealthStation navigation system, a SonoNav system, and a standard US scanner. This system determines the orientation of the US images and reformats the images from preoperative computed tomography (CT) or magnetic resonance (MR) imaging to match the US images. The system was used intraoperatively to measure brain shift several times, using the results to guide tumor resection. US-linked navigation provided information regarding brain shift, and extent of tumor resection during surgery. Evaluation of brain shift was easily achieved in all patients, without using intraoperative CT or MR imaging. Accurate information regarding the true anatomical configuration of the patient could be obtained in all phases of the operation. Magnitude of brain shift increased progressively from pre- to post-resection and depended on the type of cranial structure. Integration of the US scanner with the navigation system allowed comparisons between the intraoperative US and preoperative images, thus improving interpretation of US images. The system also improved the rate of tumor resection by facilitating the detection of remnant tumor tissue. This US-linked navigation system provides information on brain shift, and improves the accuracy and utility of image-guided surgery.

Image-guided frameless stereotactic biopsy without intraoperative neuropathological examination.

Abstract: Object Stereotactic biopsy is a safe and effective technique for the diagnosis of brain tumors. The use of intraoperative neuropathological examination has been routinely advocated to increase diagnostic yield, but the procedure lengthens surgical time, may produce false-negative and -positive results, and current biopsy techniques have a very low nondiagnostic rate. Therefore, the authors questioned the need for intraoperative histological evaluation. Methods The authors prospectively studied all patients undergoing image-guided biopsy under the care of a single surgeon (P.L.G.) between July 2005 and October 2007. A Stryker neuronavigation system with a trajectory guide was used to plan a single trajectory, and, using a side-cutting biopsy cannula, multiple biopsy samples were taken from between 1 and 4 sites within the tumor. Tissue was inspected macroscopically by the surgeon and was only submitted for neuropathological assessment postoperatively. Results One hundred thirty-four biopsies were performed...

Iso-C/3-dimensional neuronavigation versus conventional fluoroscopy for minimally invasive pedicle screw placement in lumbar fusion.

Abstract: BACKGROUND: Minimally invasive spinal surgery (MISS) has evolved over the past years due to the combination of microsurgery, minimal access strategies and neuronavigation. Percutaneous or mini-open pedicle screw placement is a challenge, especially for surgeons not experienced in the use of biplanar fluoroscopy or stereotactic imaging techniques. The aim of the study was to compare the precision of pedicle screw fixation for lumbar fusion procedures using Iso-C/stereotactic 3D neuronavigation (3D NAV) vs. standard AP/lateral fluoroscopy (2D NAV). METHODS: Our first 42 patients undergoing MISS for one- or 2-level lumbar or lumbosacral fusion procedures for degenerative lumbar pathology were included in this study. Either 3D NAV (n=29) or standard fluoroscopy (n=13) was used to aid screw placement. Demographics, operative time, blood loss, and screw placement accuracy were evaluated. Screw placement was evaluated postoperatively using lumbar CT scanning. Accuracy of 3D NAV was evaluated by comparing intraoperative planning screenshots to postoperative CT placement of screws. RESULTS: There were no significant differences between groups for mean age, gender or intraoperative blood loss. 90.9% of 3D NAV screws and 73.7% of fluoroscopy screws had no pedicle perforation (p=0.04). Intraoperative navigation screenshots accurately predicted pedicle screw placement in 90.9% of cases. There was a positive correlation between 3D NAV accuracy and better screw grade (rs 0.45, p=0.036). CONCLUSIONS: Utilization of 3D NAV for percutaneous or mini-open lumbar screw placement during the early learning curve for MISS was associated with higher screw accuracy. This study demonstrates that the use of 3D navigation can facilitate the learning curve for MISS.

Integrating magnetic resonance imaging postprocessing results into neuronavigation for electrode implantation and resection of subtle focal cortical dysplasia in previously cryptogenic epilepsy.

Abstract: Objective Focal cortical dysplasias (FCDs) are highly epileptogenic lesions. Surgical removal is frequently the best treatment option for pharmacoresistant epilepsy. However, subtle FCDs may remain undetected even after high-resolution magnetic resonance imaging (MRI). Morphometric MRI analysis, which compares the individual brain with a normal database, can facilitate the detection of FCDs. We describe how the results of normal database-based MRI postprocessing can be used to guide stereotactic electrode implantation and subsequent resection of lesions that are suspected to be FCDs. Methods A presurgical evaluation was conducted on a 19-year-old woman with pharmacoresistant hypermotor seizures. Conventional high-resolution MRI was classified as negative for epileptogenic lesions. However, morphometric analysis of the spatially normalized MRI revealed abnormal gyration and blurring of the gray-white matter junction, which was suggestive of a small and deeply seated FCD in the left frontal lobe. Results The brain region highlighted by morphometric analysis was marked as a region of interest, transferred back to the original dimension of the individual MRI, and imported into a neuronavigation system. This allowed the region of interest-targeted stereotactic implantation of 2 depth electrodes, by which seizure onset was confirmed in the lesion. The electrodes also guided the final resection, which rendered the patient seizure-free. The lesion was histologically classified as FCD Palmini and Luders IIB. Conclusion Transferring normal database-based MRI postprocessing results into a neuronavigation system is a new and worthwhile extension of multimodal neuronavigation. The combination of resulting regions of interest with functional and anatomic data may facilitate planning of electrode implantation for invasive electroencephalographic recordings and the final resection of small or deeply seated FCDs.

Lateral transpeduncular approach to intrinsic lesions of the rostral pons.

Abstract: OBJECTIVE We describe the lateral transpeduncular approach to access lesions in the rostral pons. The surgical indications and technique are discussed in the context of an illustrative case and pertinent anatomic considerations. METHODS A 38-year-old man with acute right hemiparesis and bulbar symptoms had a left pontine hemorrhage with an associated cavernous malformation and venous anomaly. There was no pial or ependymal representation of the lesion. To avoid disruption of eloquent structures, the pia was entered in the posterolateral aspect of the middle cerebellar peduncle. Subsequent dissection was guided by stereotactic neuronavigation in a ventromedial trajectory along the course of the pontocerebellar fibers. RESULTS The cavernous malformation was resected completely without procedure-related morbidity. The patient's preoperative deficits slowly improved to a functionally independent state. CONCLUSION The lateral transpeduncular approach may be used to access intrinsic lesions of the rostral pons with relatively low morbidity. Stereotactic neuronavigation and intraoperative electrophysiological monitoring are important surgical adjuncts to guide dissection and lesion extirpation. Candidate selection, microsurgical technique, and pragmatic treatment goals remain fundamental to optimal patient outcomes.

Intraoperative magnetic resonance imaging in the surgical treatment of cerebral metastases

Abstract: Background and Objectives To report on the value of intraoperative magnetic resonance imaging (iMRI) in the neurosurgical treatment of cerebral metastases (CM). Methods We performed a total of 204 surgical procedures with the use of a mobile ultra-low-field iMRI-unit. Of these, there were 12 craniotomies and 2 minimal-invasive procedures for CM, and 63 craniotomies for glioblastoma (GBM). Results On intraoperative imaging, all tumors could be localized and targeted with the help of the integrated neuronavigation system. Intraoperative imaging resulted in continued tumor resection due to unexpected residual tumor tissue in 13 patients harboring GBM (20.6%), but no patient with a CM (0%). In two patients with cystic CM, iMRI helped to achieve complete collapse of cysts by means of stereotactic aspiration, relieving mass effect and allowing for adjuvant radiotherapy. All patients subsequently received adjuvant treatment according to clinical protocols. Conclusion Surgical resection represents one of several treatment modalities in metastatic brain disease. iMRI is useful for neuronavigation and resection control and as an adjunct in minimal-invasive procedures in patients with CM; however, its exact value is yet to be determined by prospective randomized trials. J. Surg. Oncol. 2010; 101:436–441. © 2010 Wiley-Liss, Inc.

Image guidance and neuromonitoring in neurosurgery

Abstract: The localization of tumors and epileptogenic foci within the somatosensory or language cortex of the brain of a child poses unique neurosurgical challenges. In the past, lesions in these regions were not treated aggressively for fear of inducing neurological deficits. As a result, while function may have been preserved, the underlying disease may not have been optimally treated, and repeat neurosurgical procedures were frequently required. Today, with the advent of preoperative brain mapping, image guidance or neuronavigation, and intraoperative monitoring, peri-Rolandic and language cortex lesions can be approached directly and definitively with a high degree of confidence that neurosurgical function will be maintained. The preoperative brain maps can now be achieved with magnetic resonance imaging (MRI), functional MRI, magnetoencephalography, and diffusion tensor imaging. Image guidance systems have improved significantly and include the use of the intraoperative MRI. Somatosensory, motor, and brainstem auditory-evoked potentials are used as standard neuromonitoring techniques in many centers around the world. Added to this now is the use of continuous train-of-five monitoring of the integrity of the corticospinal tract while operating in the peri-Rolandic region. We are in an era where continued advancements can be expected in mapping additional pathways such as visual, memory, and hearing pathways. With these new advances, neurosurgeons can expect to significantly improve their surgical outcomes further.

Pinless frameless electromagnetic image-guided neuroendoscopy in children

Abstract: Frameless imaged-guided neuronavigation is a useful adjunct to neuroendoscopy in paediatric patients, especially those with abnormal or complex ventricular or cyst anatomy. The development of electromagnetic neuronavigation has allowed the use of image-guided navigation in the very young patient in whom rigid fixation in cranial pins is contraindicated. The technique and the authors’ experience of its use in a series of paediatric patients are described. Nineteen paediatric patients were treated with endoscopic surgery at two paediatric neurosurgery centres over a period of 18 months. A total of 29 endoscopic procedures were performed. The cases were reviewed and surgical outcomes assessed. In all of the cases, the goal of surgery was realised successfully at the time of surgery, as confirmed by post-operative imaging. No technical failures were encountered. None of the patients suffered worsened neurological function as a result of their procedures. Pinless, frameless electromagnetic neuronavigation was found to be a safe technique that can supplement endoscopic surgery in the very young patient. It allows the use of direct navigation of the endoscope in patients that are unable safely to undergo rigid cranial fixation in pins due to young age or thin skull vaults. This has proven to be a useful adjunct to neuroendoscopy in the subset of infants who have complicated or distorted ventricular anatomy and can improve the safety and accuracy of this type of surgery. It is also an alternative to optical neuronavigation in conjunction with neuroendoscopy in patients of any age.

Lateral Transpeduncular Approach to Intrinsic Lesions of the Rostral Pons. Commentary

Abstract: OBJECTIVE: We describe the lateral transpeduncular approach to access lesions in the rostral pons.The surgical indications and technique are discussed in the context of an illustrative case and pertinent anatomic considerations. METHODS: A 38-year-old man with acute right hemiparesis and bulbar symptoms had a left pontine hemorrhage with an associated cavernous malformation and venous anomaly. There was no pial or ependymal representation of the lesion. To avoid disruption of eloquent structures, the pia was entered in the posterolateral aspect of the middle cerebellar peduncle. Subsequent dissection was guided by stereo t actic neuronavigation in a ventromedial trajectory along the course of the pontocerebellar fibers. RESULTS: The cavernous malformation was resected completely without procedure-related morbidity. The patient's preoperative deficits slowly improved to a functionally independent state. CONCLUSION: The lateral transpeduncular approach may be used to access intrinsic lesions of the rostral pons with relatively low morbidity. Stereotactic neuronavigation and intraoperative electrophysiological monitoring are important surgical adjuncts to guide dissection and lesion extirpation. Candidate selection, microsurgical technique, and pragmatic treatment goals remain fundamental to optimal patient outcomes.

Surgical treatment for glioma: extent of resection applying functional neurosurgery.

Abstract: Current treatments for gliomas, including surgery, chemotherapy, and radiation therapy, frequently result in unsuccessful outcomes. Studies on glioma resection were reviewed to assess better treatment outcomes applying the newest neurosurgical multimodalities. We reviewed reports of surgical removal of gliomas utilizing functional brain mapping, monitoring, and other functional neurosurgery techniques such as neuronavigation and awake surgery. Attempts to maximize the extent of glioma resection improved survival. A close proximity of the resection to the eloquent areas increased the risk of perioperative neurological deficits. However, those deficits often improved during the postoperative rehabilitation and recovery period when the essential or the compensative eloquent areas remained intact. Pre- and intraoperative application of the latest brain function analysis methods promoted safe elimination of gliomas. These methods are expected to help explore the long-term prognosis of glioma treatment and the mechanism for recovery from functional disabilities.

Image-guided resection of small lesions in the cavernous sinus and Meckel's cave

Abstract: Objective The microsurgical resection of tumors or vascular lesions in the cavernous sinus and the neighbouring Meckel's cave has been considered as hazardous because of often associated cranial nerve morbidity Despite increasing consent that many of such tumors should not undergo surgical therapy, the cavernous sinus and Meckel's cave may harbour small lesions of various origin, which are amenable for surgical resection Surgery in this anatomical area needs a well directed approach In this setting, neuronavigational guidance may provide a useful tool We report on a series of patients operated on and guided by neuronavigation Methods Five patients underwent a pterional approach for microsurgical resection The procedures were planned and assisted by a pointer based neuronavigation system (Medtronic Stealth Station) Pathological entities included schwannoma, epidermoid, cavernoma and capillary hemangioma Three lesions were located in the Meckel's cave and two lesions in the cavernous sinus Results Intraoperative guidance by neuronavigation appeared to be particularly instrumental in identification of the appropriate site of dural incision over the target region for microsurgical resection Except of a mild increase of facial hypesthesia in one patient, there were no new cranial nerve deficits In three patients, preoperative symptoms improved immediately after surgery Conclusion The surgical resection of small tumors or vascular lesions within the Meckel's cave or cavernous sinus is facilitated by neuronavigational guidance with sufficient intraoperative reliability and safety In consideration of well known anatomical landmarks, targeted entry into the cavernous sinus or Meckel's cave directed by neuronavigation enables a tailored approach for microsurgical resection

Transnasal transsphenoid approach: a minimally invasive approach for removal of cavernous haemangiomas located at inferomedial part of orbital apex

Abstract: Ten patients complaining of visual impairment, proptosis or ocular pain, were selected for transnasal transsphenoid microsurgical approach to address cavernous haemangiomas located at inferomedial part of orbital apex. Via this approach, the contents of orbital apex were clearly illuminated and exposed as large as the surgical removal required. All tumours were identified under frameless image-guided neuronavigation and removed completely without any complications and recurrence in a mean of 12.2 months follow-up. It is concluded that a transnasal transsphenoid microsurgical approach is a minimally invasive surgery for cavernous haemangiomas located at inferomedial part of orbital apex.

Carotid artery visualization during anterior skull base surgery: a novel protocol for neuronavigation

Abstract: Detailed knowledge of the vascular anatomy of the anterior skull base is critical to successful surgery in this area. Whereas conventional neuronavigational approaches combine MRI (± contrast) for tumor visualization and CT (± C) for bony and vascular anatomy, we describe the Canadian and Austrian experiences using a novel protocol integrating MR angiography (MRA) into surgical neuronavigation to provide superior visualization of the carotid arteries. The pre-operative imaging protocol employs a T1-weighted, 3D fast spoiled gradient echo MRI (± C) for soft tissue anatomy, a plain CT for bony anatomy, and a 3D time-of-flight MR angiography for carotid anatomy. The series are imported into the Medtronic StealthStation® TREON® Treatment Guidance System; during intra-operative neuronavigation, each series (MRI, CT, MRA) can be viewed individually, or layered and viewed as a composite image. Our protocol has important advantages. First, it provides detailed tissue, tumor, vascular and bony anatomy. Second, a contrast CT is not necessary; this is important, as numerous reports have highlighted the nephrotoxic nature of radiographic contrast material. Third, visualization of the carotid system is superior than can be obtained from CT angiography. We use this unique imaging protocol routinely for our endoscopic transsphenoidal surgeries to provide superior visualization of the carotid arteries during anterior skull base surgery.

Integration of multimodality imaging and surgical navigation in the management of patients with refractory epilepsy. A pilot study using a new minimally invasive reference and head-fixation system

Abstract: To review the experience with a new system (VBH system) for minimally invasive frameless stereotactic guidance, acting as a common platform to provide multimodal image integration and surgical navigation in a consecutive series of 25 patients who underwent surgery for drug-resistant seizures. The usefulness of the VBH system for integrating all images to produce one dataset and for intraoperative instrument guidance and navigation was judged semiquantitatively in a three-tiered scale (+, ++, +++). Seizure outcome was classified according to Engel. The presurgical evaluation extended over 21.2 months (mean). A total of 141 registrations of images were performed (mean 5.6 per patient, range: 2 to 16). In 19 (76%) of 25 patients structural data fused with functional data were used for the presurgical workup. Six patients proceeded directly to navigated resection. Nineteen patients (76%) underwent invasive recording, of whom 13 underwent resective surgery. In seven patients (28%) the combination of multimodal image fusion and intra-operative stereotactic guidance was judged “essential” (+++) to remove the epileptogenic zone. Integration of all images to form one dataset was “essential” (+++) for decision making in 15 and “helpful” (++) in 4 patients (overall 76% of patients). Intraoperative use of frameless neuronavigation was “essential” (+++) in ten and “helpful” (++) in all remaining patients. Eighty percent of the patients achieved satisfactory seizure outcome after 1 year. The VBH system is a safe and effective non-invasive tool for repetitive imaging, multimodal image fusion and frameless stereotactic surgical navigation in candidates for epilepsy surgery.

Magnetically guided 3-dimensional virtual neuronavigation for neuroendoscopic surgery: technique and clinical experience.

Abstract: Objective The authors have developed a novel intraoperative neuronavigation with 3-dimensional (3D) virtual images, a 3D virtual navigation system, for neuroendoscopic surgery. The present study describes this technique and clinical experience with the system. Methods Preoperative imaging data sets were transferred to a personal computer to construct virtual endoscopic views with image segmentation software. An electromagnetic tracker was used to acquire the position and orientation of the tip of the neuroendo-scope. Virtual endoscopic images were interlinked to an electromagnetic tracking system and demonstrated on the navigation display in real time. Accuracy and efficacy of the 3D virtual navigation system were evaluated in a phantom test and on 5 consecutive patients undergoing neuroendoscopic surgery. Results Virtual navigation views were consistent with actual endoscopic views and trajectory in both phantom testing and clinical neuroendoscopic surgery. Anatomic structures that can affect surgical approaches were adequately predicted with the virtual navigation system. The virtual semitransparent view contributed to a clear understanding of spatial relationships between surgical targets and surrounding structures. Surgical procedures in all patients were performed while confirming with virtual navigation. In neurosurgery with a flexible neuroscope, virtual navigation also demonstrated anatomic structures in real time. Conclusion The interactive method of intraoperative visualization influenced the decision-making process during surgery and provided useful assistance in identifying safe approaches for neuroendoscopic surgery. The magnetically guided navigation system enabled navigation of surgical targets in both rigid and flexible endoscopic surgeries.

Midline Filum of the Sellar Dura: A Useful Landmark During Endoscopic Transsphenoidal Pituitary Surgery

Abstract: BACKGROUND: During endoscopic transsphenoidal pituitary surgery, identification and constant awareness of the midline is imperative to prevent injury to critical lateral structures, such as the internal carotid arteries. OBJECTIVE: To describe the relevance of a midline filum of the sellar dura which, when present, can serve as a useful intraoperative anatomic marker. METHODS: Intraoperative video recordings of twenty patients undergoing endoscopic transsphenoidal surgery were retrospectively reviewed to assess for the presence and location of a midline dural filum or apparent central dural vascular structure. Prospective intraoperative data were gathered on an additional 16 patients. RESULTS: A midline dural filum was identified in 18 of 36 patients (50%) undergoing endoscopic transsphenoidal surgery. This structure was identified on the midline in all cases, as confirmed by intraoperative neuronavigation and comparison with the vomer. The midline dural filum was identified as a strand-like dural extension (13 patients) or as a small vascular dural structure usually exhibiting low pressure venous bleeding (5 patients). Samples of the midline dural filum were obtained from 2 patients for histopathological analysis, which demonstrated dense collagenous connective tissue without evidence of vessel wall or ductal epithelium. CONCLUSION: In addition to anatomic structures such as the vomer and midline sphenoid sinus septations, a midline dural filum serves as a useful marker during the sellar phase of endoscopic transsphenoidal surgery. Along with intraoperative neuronavigation and Doppler ultrasonography of the cavernous carotid arteries, identification of this structure may further aid in safeguarding against injury to critical paramedian structures.

Intraoperative Magnetic Resonance Imaging

Abstract: Neurosurgeons have become reliant on image-guidance to perform safe and successful surgery both time-efficiently and cost-effectively. Neuronavigation typically involves either rigid (frame-based) or skull-mounted (frameless) stereotactic guidance derived from computed tomography (CT) or magnetic resonance imaging (MRI) that is obtained days or immediately before the planned surgical procedure. These systems do not accommodate for brain shift that is unavoidable once the cranium is opened and cerebrospinal fluid is lost. Intraoperative MRI (ioMRI) systems ranging in strength from 0.12 to 3Tesla (T) have been developed in part because they afford neurosurgeons the opportunity to accommodate for brain shift during surgery. Other distinct advantages of ioMRI include the excellent soft tissue discrimination, the ability to view the surgical site in three dimensions, and the ability to “see” tumor beyond the surface visualization of the surgeon’s eye, either with or without a surgical microscope. The enhanced ability to view the tumor being biopsied or resected allows the surgeon to choose a safe surgical corridor that avoids critical structures, maximizes the extent of the tumor resection, and confirms that an intraoperative hemorrhage has not resulted from surgery. Although all ioMRI systems allow for basic T1- and T2-weighted imaging, only high-field (>1.5T) MRI systems are capable of MR spectroscopy (MRS), MR angiography (MRA), MR venography (MRV), diffusion-weighted imaging (DWI), and brain activation studies. By identifying vascular structures with MRA and MRV, it may be possible to prevent their inadvertent injury during surgery. Biopsying those areas of elevated phosphocholine on MRS may improve the diagnostic yield for brain biopsy. Mapping out eloquent brain function may influence the surgical path to a tumor being resected or biopsied. The optimal field strength for an ioMRI-guided surgical system and the best configuration for that system are as yet undecided.

Neuronavigation in cranioorbital neurosurgery - do we really need it?

Abstract: Aim The value of neuronavigation in cranioorbital neurosurgery is controversial and relatively unstudied. The aim of this study was to evaluate the application, the usefulness and the reliability of neuronavigation in the neurosurgical treatment of orbital tumours. Material and methods A frameless armless infrared-based neuronavigation system was applied in the microsurgical removal of 7 orbital tumors. Image guidance was CT-based in 3 cases, MRI-based in another 3 cases and based on image fusion between CT and MRI image sets in one patient. The extradural fronto-orbital approach was performed in 3 cases, lateral orbitotomy in 2 cases, trans-supraciliar approach in 1 case and inferomedial orbitotomy in 1 case. Results The surgical procedures were successful in all cases. The procedure-related morbidity and mortality rate in the series was zero. The registration accuracy of the neuronavigation ranged between 1.0 and 1.7 mm, with an average of 1.3 mm. Neuronavigated image guidance was evaluated as useful in all patients. Total tumour removal was achieved in 5 patients and partial tumour excision in 1 case. One patient was only biopsied. Conclusion Neuronavigation is not a substitute for surgical knowledge and experience, but it is a valuable complement with significant intraoperative potential in cranioorbital surgery.

An integrated model-based neurosurgical guidance system

Abstract: Maximal tumor resection without damaging healthy tissue in open cranial surgeries is critical to the prognosis for patients with brain cancers. Preoperative images (e.g., preoperative magnetic resonance images (pMR)) are typically used for surgical planning as well as for intraoperative image-guidance. However, brain shift even at the start of surgery significantly compromises the accuracy of neuronavigation, if the deformation is not compensated for. Compensating for brain shift during surgical operation is, therefore, critical for improving the accuracy of image-guidance and ultimately, the accuracy of surgery. To this end, we have developed an integrated neurosurgical guidance system that incorporates intraoperative three-dimensional (3D) tracking, acquisition of volumetric true 3D ultrasound (iUS), stereovision (iSV) and computational modeling to efficiently generate model-updated MR image volumes for neurosurgical guidance. The system is implemented with real-time Labview to provide high efficiency in data acquisition as well as with Matlab to offer computational convenience in data processing and development of graphical user interfaces related to computational modeling. In a typical patient case, the patient in the operating room (OR) is first registered to pMR image volume. Sparse displacement data extracted from coregistered intraoperative US and/or stereovision images are employed to guide a computational model that is based on consolidation theory. Computed whole-brain deformation is then used to generate a model-updated MR image volume for subsequent surgical guidance. In this paper, we present the key modular components of our integrated, model-based neurosurgical guidance system.

Small ventricular access prior to rigid neuroendoscopy

Abstract: The authors describe a new technique that may be used in conjunction with neuronavigation or freehand techniques for obtaining small ventricular access. Using this modification, the introducer sheath and trocar can be guided down a ventriculostomy tract with endoscopic visual control. With increasing focus on endoscopic therapies in patients without hydrocephalus, this adjunct, based on the authors' experience, may provide an additional technique for safely treating patients.

Mobile computed tomography : early experience in Korea.

Abstract: OBJECTIVE With improved technology, the values of intraoperative computed tomography (iCT) have been reevaluated. We describe our early clinical experience with a mobile CT (mCT) system for iCT and discuss its clinical applications, advantages and limitations. METHODS Compared with intraoperative magnetic resonance imaging, this mCT system has no need for major reconstruction of a preexisting operating room for shielding, or for specialized instruments or equipment. Patients are placed on a radiolucent head clamp that fits within the gantry. Because it consists simply of a scanner and a workstation, it can be moved between locations such as an operating room, an intensive care unit (ICU) or an emergency room without difficulty. Furthermore, it can achieve nearly all types of CT scanning procedures such as enhancement, temporal bone imaging, angiography and three-dimensional reconstruction. RESULTS For intracranial surgery, mCT can be used for intraoperative real-time neuronavigation by interacting with preoperative images. It can also be used for intraoperative confirmation of the extent of resection of intracranial lesions and for immediate checks for preventing intraoperative unexpected accidents. Therefore, the goals of maximal resection or optimal treatment can be achieved without any guesswork. Furthermore, mCT can achieve improved patient care with safety and faster diagnosis for patients in an ICU who might be subjected to a ventilator and/or various monitoring devices. CONCLUSION Our initial experience demonstrates that mCT with high-quality imaging offers very useful information in various clinical situations.

Endoscopic Endonasal Transsphenoidal Skull Base Surgery

Abstract: Endoscopic skull base surgery has significantly developed than the past years because of the improved understanding of endonasal endoscopic skull base anatomy, developed endoscopic techniques and the changes of endoscopic technologies. From the management of inflammatory pathologies, we have learned to manage skull base lesions. Current anatomical knowledge with computer aided surgery has enabled surgeons to remove large lesions in the paranasal sinuses extending beyond the boundaries of the sinuses themselves. And so, the management of benign diseases with endoscope is nowadays well accepted whilst the role of endoscopic techniques in sinonasal malignancies is still under investigation. Nowadays, it is possible to tackle different pathologies placed not only in the ventral skull base, but also extended laterally (infratemporal fossa and petrous apex) and even, in really selected cases, within the orbit. At the moment, the improvement in surgical techniques has rendered endoscopic procedures capable of managing complex pathologies, according the same surgical principles of the open approaches. From now on, frameless neuronavigation, modular approaches, intraoperative imaging systems and robotic surgery are and will be an increasingly important part of endonasal surgery, and they will be overtaken by further evolution. Korean J Otorhinolaryngol-Head Neck Surg 2010;53:135-42 Key WordsZZEndoscopic·Endonasal·Transsphenoidal·Skull base surgery.