Implementation of a mobile 0.15-T intraoperative MR system in pediatric neuro-oncological surgery: feasibility and correlation with early postoperative high-field strength MRI

INTRODUCTION: We analyze our preliminary experience using the PoleStar N20 mobile intraoperative MR (iMR) system as an adjunct for pediatric brain tumor resection. METHODS: We analyzed 11 resections in nine children between 1 month and 17 years old. After resection, we acquired iMR scans to detect residual tumor and update neuronavigation. We compared final iMR interpretation by the neurosurgeon with early postoperative MR interpretation by a neuroradiologist. RESULTS: Patient positioning was straightforward, and image quality (T1 7-min 4-mm sequences) sufficient in all cases. In five cases, contrast enhancement suspect for residual tumor was noted on initial postresection iMR images. In one case, a slight discrepancy with postoperative imaging after 3 months was no longer visible after 1 year. No serious perioperative adverse events related to the PoleStar N20 were encountered, except for transient shoulder pain in two. CONCLUSIONS: Using the PoleStar N20 iMR system is technically feasible and safe for both supra- and infratentorial tumor resections in children of all ages. Their small head and shoulders favor positioning in the magnet bore and allow the field of view to cover more than the area of primary interest, e.g., the ventricles in an infratentorial case. Standard surgical equipment may be used without significant limitations. In this series, the use of iMR leads to an increased extent of tumor resection in 45 % of cases. Correlation between iMR and early postoperative MR is excellent, provided image quality is optimal and interpretation is carefully done by someone sufficiently familiar with the system

Lumbar ganglion cyst: Nosology, surgical management and proposal of a new classification based on 34 personal cases and literature review

AIM To analyze different terms used in literature to identify lumbar extradural cysts and propose a common scientific terminology; to elaborate a new morphological classification of this pathology, useful for clinical and surgical purposes; and to describe the best surgical approach to remove these cysts, in order to avoid iatrogenic instability or treat the pre-existing one. METHODS We retrospectively reviewed 34 patients with symptomatic lumbar ganglion cysts treated with spinal canal decompression with or without spinal fixation. Microsurgical approach was the main procedure and spinal instrumentation was required only in case of evident preoperative segmental instability. RESULTS The complete cystectomy with histological examination was performed in all cases. All patients presented an improvement of clinical conditions, evaluated by Visual Analogic Scale and Japanese Orthopaedic Association scoring. CONCLUSION Spinal ganglion cysts are generally found in the lumbar spine. The treatment of choice is the microsurgical cystectomy, which generally does not require stabilization. The need for fusion must be carefully evaluated: Preoperative spondylolisthesis or a wide joint resection, during the operation, are the main indications for spinal instrumentation. We propose the terms "ganglion cyst" to finally identify this spinal pathology and for the first time its morphological classification, clinically useful for all specialists

Long-term experience with intraoperative microrecording during DBS neurosurgery in STN and GPi

Intraoperative microelectrode recording (MER) for targeting during deep brain stimulation (DBS) procedures has been evaluated over a period of 4 years, in 57 consecutive patients with Parkinson's disease, who received DBS in the subthalamic nucleus (STN-DBS), and 28 consecutive patients with either dystonia (23) or Parkinson's disease (five), in whom the internal segment of the globus pallidus (GPi-DBS) was targeted. The procedure for DBS was a one-stage bilateral stereotactic approach using a combined electrode for both MER and macrostimulation. Up to five micro/macro-electrodes were used in an array with a central, lateral, medial, anterior, and posterior position. Final target location was based on intraoperative test stimulation. For the STN, the central trajectory was chosen for implantation in 50% of the cases and for the globus pallidus internus (GPi) in 57% of the cases. Furthermore, in 64% of the cases, the channel selected for the permanent electrode corresponded with the trajectory having the longest segment of STN MER activity. For the GPi, this was the case in 61%. The mean and standard deviation of the deepest contact point with respect to the magnetic resonance imaging (MRI)-based target for the STN was 2.1 +/- 1.5 mm and for the GPi was -0.5 +/- 1.2 mm. MER facilitates the selection of the final electrode location in STN-DBS and GPi-DBS, and based on the observed MER activity, a pre-selection could be made as to which channel would be the best candidate for macro-test stimulation and at which depth should be stimulated. The choice of the final location is based on intraoperative test stimulation, and it is demonstrated that regularly it is not the central channel that is chosen for implantation. On average, the target as defined by MER activity intensity was in accordance with the MRI-based targets both for the STN and GPi. However, the position of the best MER activity did not necessarily correlate with the locus that produced the most beneficial clinical response on macroelectrode testing intraoperativel

Development and evaluation of image-guided neuroendoscopy, with investigation of post-imaging brain distortion and accuracy of frameless stereotaxy

Neuroendoscopy enables a surgeon to operate deep within the brain whilst limiting morbidity through a minimally invasive approach. Technical advances in illumination, instrumentation and camera design, along with evidence for improved clinical outcome, have increased the indications for this technique and have ensured widespread popularity. However, broader application of neuroendoscopy is restricted by the necessity for direct vision of targets and by spatial disorientation. The aim of this investigation was to overcome these limitations by combining neuronavigation with neuroendoscopy to develop Image-Guided Neuroendoscopy (IGN). The strategy adopted for this was firstly to select, assess and validate a neuronavigation system, secondly to develop methods of endoscope tracking and frameless stereotactic implantation. Thirdly, to assess the impact of post-imaging brain distortion upon neuronavigation, fourthly to correct distortion of the endoscope image and finally to assess the use of graphics overlay in IGN. Laboratory phantom accuracy assessments revealed a mean point localisation error for the navigation system pointers of0.8mm (SD 0.4mm) with CT imaging, for the tracked endoscope of 1.5mm (SD 0.8mm) and for frameless stereotaxy of 1.3mm (SD 0.6mm). An in vivo study revealed a mean Euclidean error of 4.8mm (SD 2.0mm) for frame less stereotactic biopsy. The navigation system was evaluated through a clinical series of 100 cases, the frameless stereotactic technique was employed in 21 brain biopsy procedures and IGN evaluated in 5 procedures. The magnitude of post-imaging brain distortion was determined and correlations discovered with pre-operative image characteristics. The conclusions of this thesis are that IGN can be accomplished with acceptable accuracy, including frameless stereotactic implantation, and that the impact of postimaging brain distortion will not negate the value of IGN in most cases. Thus, the method developed for IGN has overcome both major constraints of neuroendoscopy, enabling endoscopic surgery to pass through and beyond the ventricular wall, to be undertaken safely in cases with distorted anatomy and opening the potential for wider application of these minimally invasive techniques

An Experimental and Numerical Study on Tactile Neuroimaging: A Novel Minimally Invasive Technique for Intraoperative Brain Imaging

This is the peer reviewed version of the following article: Moslem Sadeghi-Goughari, Yanjun Qian, Soo Jeon, Sohrab Sadeghi and Hyock-Ju Kwon, “An Experimental and Numerical Study on Tactile Neuroimaging: A Novel Minimally Invasive Technique for Intraoperative Brain Imaging,” accepted to The International Journal of Medical Robotics and Computer Assisted Surgery which has been published in final form at: https://doi.org/10.1002/rcs.1893. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Background The success of tumor neurosurgery is highly dependent on the ability to accurately localize the operative target, which may be shifted during the operation. Performing an intraoperative brain imaging is crucial in minimally invasive neurosurgery to detect the effect of brain shift on the tumor’s location, and to maximize the efficiency of tumor resection. Method The major objective of this research is to introduce the tactile neuroimaging as a novel minimally invasive technique for intraoperative brain imaging. To investigate the feasibility of the proposed method, an experimental and numerical study was first performed on silicone phantoms mimicking the brain tissue with a tumor. Then the study was extended to a clinical model with the meningioma tumor. Results The stress distribution on the brain surface has high potential to intraoperatively localize the tumor. Conclusion Results suggest that tactile neuroimaging can be used to provide a non-invasive, and real-time intraoperative data on tumor’s features.Natural Sciences and Engineering Research Council || RGPIN/2015-05273, RGPIN/2015-04118, RGPAS/354703-201

Augmented Reality-Assisted Craniotomy for Parasagittal and Convexity En Plaque Meningiomas and Custom-Made Cranio-Plasty: A Preliminary Laboratory Report

Background: This report discusses the utility of a wearable augmented reality platform in neurosurgery for parasagittal and convexity en plaque meningiomas with bone flap removal and custom-made cranioplasty. Methods: A real patient with en plaque cranial vault meningioma with diffuse and extensive dural involvement, extracranial extension into the calvarium, and homogeneous contrast enhancement on gadolinium-enhanced T1-weighted MRI, was selected for this case study. A patient-specific manikin was designed starting with the segmentation of the patient’s preoperative MRI images to simulate a craniotomy procedure. Surgical planning was performed according to the segmented anatomy, and customized bone flaps were designed accordingly. During the surgical simulation stage, the VOSTARS head-mounted display was used to accurately display the planned craniotomy trajectory over the manikin skull. The precision of the craniotomy was assessed based on the evaluation of previously prepared custom-made bone flaps. Results: A bone flap with a radius 0.5 mm smaller than the radius of an ideal craniotomy fitted perfectly over the performed craniotomy, demonstrating an error of less than ±1 mm in the task execution. The results of this laboratory-based experiment suggest that the proposed augmented reality platform helps in simulating convexity en plaque meningioma resection and custom-made cranioplasty, as carefully planned in the preoperative phase. Conclusions: Augmented reality head-mounted displays have the potential to be a useful adjunct in tumor surgical resection, cranial vault lesion craniotomy and also skull base surgery, but more study with large series is needed