Stereotactic Navigation Research Articles

Pedicled nasoseptal flap reconstruction for craniopharyngiomas in pediatric patients.

Though the use of the pedicled nasoseptal flap (NSF), a reconstructive technique used after endoscopic endonasal approaches (EEA) for resection of craniopharyngiomas, has been shown to reduce the occurrence of post-operative cerebrospinal fluid (CSF) leaks in adults, less is known about its use in pediatric populations, specifically in children under the age of 7. The goal of this retrospective cohort study is to determine the viability of the pedicled NSF for pediatric patients. Retrospective review of 12 pediatric patients (ages 2-16) undergoing 13 NSF reconstructions after resection of craniopharyngiomas. Radioanatomic analysis of computed tomography (CT) scans was utilized to classify the pneumatization of the sphenoid sinus depending on the thickness of the sphenoid bone margin. Intercarotid distances were measured from magnetic resonance imaging (MRI) scans to assess the feasibility of this reconstruction technique in pediatric patients. At the time of surgery, all patients were noted to have adequate NSF length and width. No post-operative high-flow CSF leaks were found within the group. Lack of pneumatization of the sphenoid sinus and narrow intercarotid distances in the youngest of patients did not lead to negative clinical outcomes. Based on our results and experience, the pedicled nasoseptal flap is a viable reconstructive option after EEA in the pediatric population, including even the youngest of patients. In these patients, a narrowed window between the intercarotid arteries and the lack of pneumatization of the sphenoid sinus present a challenge that can be overcome by using stereotactic navigation and advanced endoscopic techniques.

Evaluation of Surgical-Navigation System in Management of Orbital Disorders

AbstractBackground: Surgical navigation guidance is primarily designed to assist with surgery on bony tissues and closed spaces, it is widely used in neurosurgery and sinus surgery. And since the limited mobility of the soft tissues of the orbit, as they are tightly contained within its bony walls, stereotactic navigation may be a useful tool in orbial surgeries such as tumor excisions, biopsies, orbital wall fractures, and orbital decopmression.Aim of Study: To evaluate whether the use of Frameless surgical navigation is useful and time efficient in removing orbital masses and repairing orbital wall fracture as known to be a helpful tool in Neurosurgery and sinus surgery.Patients and Methods: Prospective interventional non-controlled non-randomized case series study was coducted in Cairo Univeristy Hospitals from June 2013 to December 2014 on 15 patients with primary or recurrent post-septal orbital pathology using the Electromagnetic “FusionTM ENT Naviga-tion System” during the surgery. Primary outcomes were assessing time efficiency through operative times (Total Time, Operating Time and Maintenance Time), extent of mass excision and fracture repair. Secondary outcomes were im-provement in Hertel's readings and detecting complication related to the navigation system.Results: The mean of maintenance time percentage com-pared to the total operating time was 46.7% with SD ±6.1 that lead to relatively longer total operating time, but as more cases were performed, it decreased gradually. Complete excision was achieved in 70% of cases. The p-value for improved Hertel's reading was 0.016 and only one case had significant complications.Conclusion: Although promising results were seen in orbital wall fracture and well circumscribed orbital masses. The Surgical Navigation System cannot yet be considered the standard of care for patients with different orbital pathologies as it prolongs the total operating time. However, it is helpful and promising in complicated cases of recurrent and infiltrative masses and massive trauma, where the normal anatomical landmarks are compromised specially with the evolving updates in improving this technology.

MIS approaches in the cervical spine.

Minimally invasive surgical approaches for the treatment of spinal pathologies have accelerated over the past three decades and resulted in superior functional outcomes with less complications. Yet cervical pathologies have been slower to gain traction for multiple anatomical factors and its "high-risk" profile. Various minimally invasive techniques for cervical disease have now been described and validated in long-term studies with comparable outcomes to traditional open approaches and concomitant reduction in morbidity and socioeconomic costs. Transnasal operations can be used to treat ventral upper cervical disease, circumventing traditional and morbid transoral approaches. Posterior-based focused treatments for radiculopathy and myelopathy such as tubular-guided foraminotomies and unilateral laminotomies for bilateral cord decompression have also been described and becoming increasingly less invasive. Cervical fusions can now be performed percutaneously through modified, stand-alone facet joint cages that can be packed with allogeneic bone graft. These advances have been facilitated by the development of intraoperative imaging technologies (intraoperative CT) and 3-dimensional stereotactic navigation software. While this review focuses on these procedures and evidence-based outcomes data, the future for MIS applications in cervical spine surgery will continue to evolve over the coming years with wider indications and technological adjuncts.

In Reply to the Letter to the Editor Regarding “Gelatin Paste as an Alternative Cost-Effective Hemostatic Agent in Cranial Surgery: Doing More with Less”

Perioperative cerebral infarction is a potential complication of glioma resection, of which insular tumors are at higher risk because of the proximity of middle cerebral artery branches, including the lateral lenticulostriates and long insular arteries. In this study, 3 patients received three-dimensional rotational angiography, which was fused with magnetic resonance imaging (MRI) for frameless stereotactic navigation during dominant-hemisphere insular glioma resection.All patients obtained a preoperative catheter angiogram with a three-dimensional rotational acquisition of the ipsilateral internal carotid artery. The pixel-based axial three-dimensional angiography data, thin-cut structural MRI, tractography from diffusion tensor imaging, and expressive language activation from functional MRI were uploaded into the iPlan software (Brainlab, Heimstetten, Germany) and fused. The target tumor, regional blood vessels, adjacent functional areas, and their associated fiber tracts were segmented and overlaid on the appropriate MRI sequence. This image fusion was used preoperatively to visualize the relationship of the mass with the adjacent vasculature and intraoperatively for frameless stereotactic navigation to optimize preservation of arterial structures.Three patients aged 27–60 years with excellent baseline functional status presented with seizures and were found to have a large dominant-hemisphere T2 hyperintense nonenhancing insular mass. Surgical resection was performed using multimodality neuronavigation. None sustained a postoperative arterial infarction or a perioperative neurologic deficit.Neuronavigation using a fusion of three-dimensional rotational angiography with MRI is a technique that can be used for preoperative planning and during resection of insular gliomas to optimize preservation of adjacent arteries.

Frameless Stereotactic Navigation during Insular Glioma Resection using Fusion of Three-Dimensional Rotational Angiography and Magnetic Resonance Imaging

Perioperative cerebral infarction is a potential complication of glioma resection, of which insular tumors are at higher risk because of the proximity of middle cerebral artery branches, including the lateral lenticulostriates and long insular arteries. In this study, 3 patients received three-dimensional rotational angiography, which was fused with magnetic resonance imaging (MRI) for frameless stereotactic navigation during dominant-hemisphere insular glioma resection. All patients obtained a preoperative catheter angiogram with a three-dimensional rotational acquisition of the ipsilateral internal carotid artery. The pixel-based axial three-dimensional angiography data, thin-cut structural MRI, tractography from diffusion tensor imaging, and expressive language activation from functional MRI were uploaded into the iPlan software (Brainlab, Heimstetten, Germany) and fused. The target tumor, regional blood vessels, adjacent functional areas, and their associated fiber tracts were segmented and overlaid on the appropriate MRI sequence. This image fusion was used preoperatively to visualize the relationship of the mass with the adjacent vasculature and intraoperatively for frameless stereotactic navigation to optimize preservation of arterial structures. Three patients aged 27-60 years with excellent baseline functional status presented with seizures and were found to have a large dominant-hemisphere T2 hyperintense nonenhancing insular mass. Surgical resection was performed using multimodality neuronavigation. None sustained a postoperative arterial infarction or a perioperative neurologic deficit. Neuronavigation using a fusion of three-dimensional rotational angiography with MRI is a technique that can be used for preoperative planning and during resection of insular gliomas to optimize preservation of adjacent arteries.

Stereotactic Vertebroplasty for Spinal Metastases with Multilevel Bilateral Pedicle Fractures: A Technical Note.

Vertebral compression fractures (VCFs) represent a significant cause of disability and primarily result from either underlying vertebral body neoplasms or osteoporosis. Vertebroplasty (VP) is a procedure commonly utilized to repair pathologic VCFs in order to manage pain and reinstate vertebral body height. However, there is a paucity of literature on how to manage painful multilevel VCFs with concomitant bilateral pedicle fractures. We describe a patient with a primary prostatic carcinoma and VCFs of the third and fourth lumbar vertebrae (L3 and L4, respectively) with concomitant bilateral pedicle fractures secondary to metastatic disease. Due to the degree of damage to the L3 and L4 vertebral bodies and pedicles, a VP performed via a percutaneous approach was deemed to be too high risk. VP for L3 and L4 was instead performed by utilizing stereotactic spine navigation and an intraoperative O-arm (Medtronic Corporation, Minneapolis, Minnesota). Our result indicates a potential role for stereotactic spine navigation in vertebroplasty for complex pathologic VCFs.

Improved Surgical Safety via Intraoperative Navigation for Transnasal Transsphenoidal Resection of Pituitary Adenomas.

Objectives Intraoperative navigation during neurosurgery can aid in the detection of critical structures and target lesions. The safety and efficacy of intraoperative, stereotactic computed tomography (CT) in the transnasal transsphenoidal resection of pituitary adenomas were explored. Design Retrospective chart review Setting Tertiary care hospital Participants Patients who underwent transsphenoidal resection of pituitary adenomas from February 2002 to May 2017. Intraoperative stereotactic CT navigation was used for all patients after mid-October 2013. Main Outcome Measures Operative time, estimated blood loss, gross total resection rate. Results Of 634 patients included, 175 underwent surgery with intraoperative navigation and 444 had no intraoperative navigation during surgery. There was no difference in mean age, sex, tumor type, or tumor size between the two groups. Operative time, endoscope use, cerebrospinal fluid diversion, and estimated blood loss were also similar. Two patients showed intraoperative, iatrogenic misdirection in the absence of stereotactic CT navigation ( p = 0.99) but similar numbers of patients having navigated and non-navigated surgery returned to the operating room, underwent gross total resection, and showed endocrinological normalization. Conclusions These results suggest that intraoperative navigation can reduce injury without resulting in increased operative time, estimated blood loss, or reduction in gross total resection.

A Combined Extradural–Intradural Technique for an En Bloc Anterior Petrosectomy: A Cadaveric Feasibility Study

The anterior petrosectomy approach is among the most popular for exposure of the petroclival region. However, the complexity of the anatomy, drilling time required, and risk of injury to neurovascular structures have made this procedure especially challenging. We have proposed a novel combined extradural-intradural technique for en bloc anterior petrosectomy-or one-piece Kawase-and have charted the landmarks that define its surgical boundaries. The approach was performed on 14 embalmed specimens. The one-piece Kawase approach consists of 3 extradural drilling steps, followed by incision of the dura and skeletonization of the superior petrosal sinus. The procedure culminates with 2 intradural drilling steps. The bone piece was then removed en bloc, and the maximum anteroposterior, superoinferior, and mediolateral lengths were recorded. The linear distances between the main neurovascular landmarks were also measured using a stereotactic navigation system. The mean measurements were 17.6 ± 2.6 mm for the anteroposterior distance, 10.5 ± 2.3 mm for the superoinferior distance, and 9.5 ± 2.6 mm for the mediolateral distance. The medial linear distance from the mandibular nerve/greater superficial petrosal nerve to the internal carotid artery was 6.8 ± 1.3 mm, to the facial hiatus was 11.6 ± 2.2 mm, and to the lateral internal acoustic canal was 17.9 ± 1.8 mm. The average distance from the porus trigeminus to the medial internal acoustic canal was 19.4 mm. The advantages of this technique include the wide exposure of the petroclival region, extensive visualization of critical structures via extradural and intradural corridors, and minimization of bone drilling, which could reduce heat damage. Clinical application of the illustrated technique is required to test its reliability in different pathological subsets.

New structural formations of the cerebellar dentate nucleus and their use in stereotactic navigation in neurosurgical practice

New structural formations of the cerebellar dentate nucleus and their use in stereotactic navigation in neurosurgical practice

Locating primary somatosensory cortex in human brain stimulation studies: systematic review and meta-analytic evidence.

Transcranial magnetic stimulation (TMS) over human primary somatosensory cortex (S1), unlike over primary motor cortex (M1), does not produce an immediate, objective output. Researchers must therefore rely on one or more indirect methods to position the TMS coil over S1. The "gold standard" method of TMS coil positioning is to use individual functional and structural magnetic resonance imaging (f/sMRI) alongside a stereotactic navigation system. In the absence of these facilities, however, one common method used to locate S1 is to find the scalp location that produces twitches in a hand muscle (e.g., the first dorsal interosseus, M1-FDI) and then move the coil posteriorly to target S1. There has been no systematic assessment of whether this commonly reported method of finding the hand area of S1 is optimal. To do this, we systematically reviewed 124 TMS studies targeting the S1 hand area and 95 fMRI studies involving passive finger and hand stimulation. Ninety-six TMS studies reported the scalp location assumed to correspond to S1-hand, which was on average 1.5-2 cm posterior to the functionally defined M1-hand area. Using our own scalp measurements combined with similar data from MRI and TMS studies of M1-hand, we provide the estimated scalp locations targeted in these TMS studies of the S1-hand. We also provide a summary of reported S1 coordinates for passive finger and hand stimulation in fMRI studies. We conclude that S1-hand is more lateral to M1-hand than assumed by the majority of TMS studies.

Minimally Invasive, Stereotactic, Wireless, Percutaneous Pedicle Screw Placement in the Lumbar Spine: Accuracy Rates With 182 Consecutive Screws.

Standard fluoroscopic navigation and stereotactic computed tomography-guided lumbar pedicle screw instrumentation traditionally relied on the placement of Kirshner wires (K-wires) to ensure accurate screw placement. The use of K-wires, however, is associated with a risk of morbidity due to potential ventral displacement into the retroperitoneum. We report our experience using a computer image-guided, wireless method for pedicle screw placement. We hypothesize that minimally invasive, wireless pedicle screw placement is as accurate and safe as the traditional technique using K-wires while decreasing operative time and avoiding potential complications associated with K-wires. We conducted a retrospective review of 42 consecutive patients who underwent a stereotactic-guided, wireless lumbar pedicle screw placement. All screws were placed to provide fixation to a variety of interbody fusion constructs including anterior lumbar interbody fusion, lateral interbody fusion, and transforaminal lumbar interbody fusion. The procedures were performed using the O-arm intraoperative imaging system with StealthStation navigation (Medtronic, Memphis, TN) and Medtronic navigated instrumentation. After placing a percutaneous navigation frame into the posterior superior iliac spine or onto an adjacent spinous process, an intraoperative O-arm image was obtained to allow subsequent StealthStation navigation. Para-median incisions were selected to allow precise percutaneous access to the target pedicles. The pedicles were cannulated using either a stereotactic drill or a novel awl-tipped tap along with a low-speed/high-torque power driver. The initial trajectory into the pedicle was recorded on the Medtronic StealthStation prior to removal of the drill or awl-tap, creating a "virtual" K-wire rather than inserting an actual K-wire to allow subsequent tapping and screw insertion. Accurate screw placement is achieved by following the virtual path as an exact computer-aided design model of the screw traversing the pedicle is projected onto the display and by using audible and tactile feedback. A second O-arm scan was obtained to confirm accuracy of screw placement. A total of 20 women and 22 men (average age = 56 years) underwent a total of 182 pedicle screw placements using the stereotactic, wireless technique. The total breach rate was 9.9%, with a clinically significant breach rate of 0% (defined as >2 mm medial breach or >4 mm lateral breach) and a clinical complication rate of 0%. Wireless, percutaneous placement of lumbar pedicle screws using computed tomography-guided stereotactic navigation is a safe, reproducible technique with very high accuracy rates.

Minimally Invasive Sacroiliac Joint Fusion with Cylindrical Threaded Implants Using Intraoperative Stereotactic Navigation

Significant progress in hardware and surgical techniques for sacroiliac joint (SIJ) fusion surgeries has facilitated safer and more efficacious procedures for patients. Triangular-shaped implants for SIJ fusions are the most-studied devices and have demonstrated good short-term and long-term clinical outcomes. Reports on cylindrical threaded implants are very limited. Owing to biomechanical differences in the implants and the surgical techniques required for their placement, previously reported results may not be applicable to cylindrical threaded implants. The aim of this study was to report preliminary clinical experience with minimally invasive SIJ fusion using intraoperative stereotactic navigation and the Rialto SI Fusion System. We retrospectively reviewed 24 patients who underwent SIJ fusions between May 2015 and October 2017 performed by a single surgeon. Mean total satisfaction score was 89.0% ± 27.6%. A statistically significant reduction (P= 0.0028) in low back pain scores was noted from an average baseline score of 6.6 ± 2.4 to 3.7 ± 3.3 postoperatively. Leg pain scores decreased from 4.8 ± 3.8 to 1.5 ± 2.9 (P= 0.0034). Mean surgical time was 53.0 ± 13.9 minutes. It took significantly longer (P= 0.0089) to perform the initial 13 cases (59.9 ± 15.2 minutes) compared with subsequent cases (45.4 ± 7.3 minutes). Estimated blood loss was minimal (10.4 ± 5.2 mL). Minimally invasive SI joint fusion using cylindrical threaded implants can be safely performed with minimal morbidity and good clinical outcomes.

Placement of Ommaya Reservoirs Using Electromagnetic Neuronavigation and Neuroendoscopy: A Retrospective Study with Cost-Benefit Analysis

Placement of intraventricular catheters in oncology patients is associated with high complication rates. Placing Ommaya reservoirs with the zero-error precision protocol (ZEPP), a combination of neuronavigation (AxiEM stereotactic navigation) and direct verification of catheter tip placement with a flexible neuroendoscope, is associated with decreased complication rates as a result of increased catheter placement accuracy. However, the ZEPP costs more than traditional methods of catheter placement, and the question of whether this increased accuracy with the ZEPP is cost-effective is unknown. We performed a single-center retrospective chart review of 50 consecutive ommaya reservoir patient placements between 2010 and 2017. Twenty-five ventricular catheters were placed using the ZEPP protocol, and 25 ventricular catheters were placed using only AxiEM stealth navigation. Postoperative catheter accuracy and complication rates were assessed. A cost-benefit analysis was then conducted to determine if the overall cost for placing Ommaya reservoirs with the ZEPP was effective compared with the alternative method of using neuronavigation alone. In the non-ZEPP cohort, 10 of 25 catheters were placed within the optimal location compared with 25 of 25 catheters placed in the ZEPP cohort. Three complications occurred in the non-ZEPP cohort: 2 malpositioned catheters required surgical revision and 1 catheter-related hemorrhage resulted in a prolonged stay in the intensive care unit. No complications occurred in the ZEPP cohort. A cost-benefit analysis showed $4784 savings per patient with ZEPP utilization because of the high complication-associated costs. Implementation of the ZEPP for verifying ventricular catheter placement in Ommaya reservoirs improved catheter tip accuracy, resulted in lower complication rates, and was more cost-effective when compared with the non-ZEPP cohort, which used only neuronavigation. The ZEPP can be used for ventricular shunt catheter placement to decrease complications and verify catheter tip accuracy in Ommaya or standard ventriculoperitoneal shunts.

Positioning accuracy of the implants placed by the stereotactic navigation or the freehand techniques

Positioning accuracy of the implants placed by the stereotactic navigation or the freehand techniques

Navigated liver surgery : Current state and importance in the future

The preoperative computer-assisted resection planning is the basis for every navigation. Thanks to modern algorithms, the prerequisites have been created to carry out avirtual resection planning and arisk analysis. Thus, individual segment resections can be precisely planned in any conceivable combination. The transfer of planning information and resection suggestions to the operating theater is still problematic. The so-called stereotactic liver navigation supports the exact intraoperative implementation of the planned resection strategy and provides the surgeon with real-time three-dimensional information on resection margins and critical structures during the resection. This is made possible by asurgical navigation system that measures the position of surgical instruments and then presents them together with the preoperative surgical planning data. Although surgical navigation systems have been indispensable in neurosurgery and spinal surgery for many years, these procedures have not yet become established as standard in liver surgery. This is mainly due to the technical challenge of navigating amoving organ. As the liver is constantly moving and deforming during surgery due to respiration and surgical manipulation, the surgical navigation system must be able to measure these alterations in order to adapt the preoperative navigation data to the current situation. Despite these advances, further developments are required until navigated liver resection enters clinical routine; however, it is already clear that laparoscopic liver surgery and robotic surgery will benefit most from navigation technology.

Implantation of Depth Electrodes in Children Using VarioGuide® Frameless Navigation System: Technical Note.

Electrode placement in epilepsy surgery seeks to locate the sites of ictal onset and early propagation. An invasive diagnostic procedure, stereoelectroencephalography (SEEG) is usually implemented with frame-based methods that can be especially problematic in young children. To evaluate the feasibility and accuracy of a new technique for frameless SEEG in children using the VarioGuide® system (Brainlab AG, München, Germany). A frameless stereotactic navigation system was used to implant depth electrodes with percutaneous drilling and bolt insertion in pediatric patients with medically refractory epilepsy. Data on general demographic information of electrode implantation, duration, number, and complications were retrospectively collected. To determine the placement accuracy of the VarioGuide® frameless system, the mean Euclidean distances were calculated by comparing the preoperatively planned trajectories with the final electrode position observed on postoperative computed tomography scans. From May 2011 to December 2015, 15 patients (8 males, 7 females; mean age: 8 yr, range: 3-16 yr) underwent SEEG depth electrode implantation of a total of 111 electrodes. The mean error measured by the Euclidean distance from the center of the entry point to the intended entry point was 3.64 ± 1.78 mm (range: 0.58-7.59 mm) and the tip of the electrode to the intended target was 2.96 ± 1.49 mm (range: 0.58-7.82 mm). There were no significant complications. Depth electrodes can be placed safely and accurately in children using the VarioGuide® frameless stereotactic navigation system.

Contralateral Transfalcine Versus Ipsilateral Anterior Interhemispheric Approach for Midline Arteriovenous Malformations: Surgical and Anatomical Assessment

The contralateral anterior interhemispheric approach (CAIA) is considered to provide surgical advantages to access deep midline lesions: wider working angle, gravity enhanced dissection and retraction, more efficient lighting, and ergonomics. Our team has previously published on the merits of using a contralateral trajectory for medial frontoparietal arteriovenous malformations (AVMs) compared with the conventional anterior interhemispheric approach (IAIA). In this article, we compare the IAIA and CAIA for the resection of medial frontoparietal AVMs using quantitative surgical and anatomical analysis. Two models were designed mimicking the most common features of midline AVMs. The CAIA and IAIA were performed bilaterally in 10 specimens. Variables to compare technical feasibility (surgical window [SW] and surgical freedom [SF], target exposure, and angle of attack) were independently assessed using stereotactic navigation. The average SW, SF, and angle of attack were compared with the Student t test. Significance threshold was set at 0.05. The CITA and IAIA were similar in terms of SW, target exposure, and SF in the superior aspect of the AVM. In the depth of the interhemispheric fissure, the CAIA was significantly superior to IAIA in both AVM models: 77% wider AA for the inferior aspect of the AVM (P < 0.01) and greater SF for the draining vein (54%, P= 0.01), ipsilateral (98%, P= 0.02), and contralateral ACA (117%, P < 0.01). This study suggests technical superiority of the CAIA for the resection of deep midline AVMs. No objective difference was noted in the superficial areas of our models, denoting that IAIA is a safer choice for superficial AVMs. Our results set the foundation for further clinical analysis comparing both approaches.

INFLUENCE OF PRE-STIMULATION RHYTHMS ON PHOSPHENE PERCEPTION IN THE CONTEXT OF VISUAL HALLUCINATIONS

Background Complex visual hallucinations are a common symptom in Parkinson’s disease dementia (PDD). Cortical alpha rhythm is a measure of attention and visual perception in healthy controls, and is reported to dysfunction in PDD. Additionally, previous research has related the likelihood to experience visual hallucinations with levels of neuronal excitability in alpha band rhythms from the visual cortex. Methods A group of controls participants (n=17) and recently diagnosed PDD patients (n=26) where recruited for the study. Concurrent transcranial magnetic stimulation and electroencephalogram (TMS-EEG) was delivered to all participants and brain signals recorded. Using stereotactic navigation, the cortical region for optimal phosphene experience was determined within the visual cortex in an incremental power stimulation design, where TMS power was increased up to 75% of stimulator output. Only 11 PDD (mean age = 75.47 ± 5.4) and 9 control participants (mean age 73.82 ± 5.4) experienced phosphenes on 50% of trials (240 trials). Mixed effect analysis was implemented to investigate the effects of scalp region (anterior, posterior), pre-stimulus EEG power (within theta, low-alpha and high alpha bands), and participant group on phosphene experience. Results In the anterior region, there was a significant effect of phosphene or no-phosphene condition on the low-alpha relative power (F(1,18)=4.72, p=0.043, η2=0.208). Both groups showed decreased low-alpha power before phosphene experience and low-alpha power was lower in PDD participants when compared to controls. When separating the PDD hallucinators from the non-hallucinators, a significant effect of phosphene condition was found in high-alpha band (F(1,17)=7.79, p=0.013, η2=0.314). The posterior high-alpha band power was lower in the PDD hallucinator subgroup at both phosphene/no-phosphene conditions, but higher in the non-hallucinator subgroup when phosphenes were not experienced. Conclusions Decreased neural excitability at low-alpha band within the visual cortex is a driver of phosphene experience in both control and PDD patients. However, our data suggests that patients that normally experience complex visual hallucinations are in constant state of decreased alpha power that may elicit this symptom.

Investigation of Titanium Material Deformation for Positioning Stereotactic Navigation System by von Mises Stress Criteria and Finite Element in Engineering

Investigation of Titanium Material Deformation for Positioning Stereotactic Navigation System by von Mises Stress Criteria and Finite Element in Engineering

Integration of resting state functional MRI into clinical practice - A large single institution experience.

Functional magnetic resonance imaging (fMRI) is an important tool for pre-surgical evaluation of eloquent cortex. Classic task-based paradigms require patient participation and individual imaging sequence acquisitions for each functional domain that is being assessed. Resting state fMRI (rs-fMRI), however, enables functional localization without patient participation and can evaluate numerous functional domains with a single imaging session. To date, post-processing of this resting state data has been resource intensive, which limits its widespread application for routine clinical use. Through a novel automated algorithm and advanced imaging IT structure, we report the clinical application and the large-scale integration of rs-fMRI into routine neurosurgical practice. One hundred and ninety one consecutive patients underwent a 3T rs-fMRI, 83 of whom also underwent both motor and language task-based fMRI. Data were processed using a novel, automated, multi-layer perceptron algorithm and integrated into stereotactic navigation using a streamlined IT imaging pipeline. One hundred eighty-five studies were performed for intracranial neoplasm, 14 for refractory epilepsy and 33 for vascular malformations or other neurological disorders. Failure rate of rs-fMRI of 13% was significantly better than that for task-based fMRI (38.5%,) (p <0.001). In conclusion, at Washington University in St. Louis, rs-fMRI has become an integral part of standard imaging for neurosurgical planning. Resting state fMRI can be used in all patients, and due to its lower failure rate than task-based fMRI, it is useful for patients who are unable to cooperate with task-based studies.