Three-dimensional reconstructed computed tomography-magnetic resonance fusion image-based preoperative planning for surgical procedures for spinal lipoma or tethered spinal cord after myelomeningocele repair

Preoperative interactive virtual simulation applying three-dimensional multifusion images using a haptic device for lumbosacral lipoma

PURPOSE

Untethering surgery for lumbosacral lipoma is a preventive procedure, and avoidance of complications and good long-term outcomes are required. We introduced presurgical interactive virtual simulation (IVS) applying three-dimensional multifusion images using a haptic device aimed at improving operative outcomes.

METHODS

Fourteen patients with newly diagnosed lumbosacral lipoma were recruited and underwent preoperative IVS. The median age at surgery was 8 months. A three-dimensional image analysis system was used to extract and fuse structures necessary for surgery, such as the lipoma, spinal cord and skin, from CT and MRI, and create three-dimensional multifusion images. The created images were individually converted to standard triangulated language format and loaded onto a workstation (Geomagic freeform™) that could be freely transformed, and the laminectomy range and lipoma extraction procedure were examined. Presurgical IVS was performed, and the actual surgery was performed.

RESULTS

The disease types were dorsal, caudal, lipomyelomeningocele, transitional, and filum in 5, 5, 2, 1, and 1 patients, respectively. The surgical procedure and extent of the laminectomy were as planned for all patients. Resection of the lipomas tended to be less than expected preoperatively because of positive reactions on intraoperative monitoring. No postoperative complications were observed. The median postoperative follow-up period was 29 months, and there were no reoperations during the observation period.

CONCLUSIONS

Although there are various types of lumbosacral lipoma, surgery can be safely performed by performing presurgical IVS. The short-term course is good; however, long-term follow-up is necessary for the appearance of neurological symptoms associated with growth and re-tethering.

The Use of Fusion Images as a Diagnostic and Neurosurgical Planning Tool in Microvascular Decompression

Preoperative assessment of surgery using high-quality images can help surgeons to achieve best result of treatment. With the advances in computer technology, interactive multimodality fusion images have been developed. The use of fusion images as a preoperative planning tool is described with its examples in illustrative cases of trigeminal neuralgia and hemifacial spasm microvascular decompression (MVD). Interactive computer graphics such as multimodality fusion method is a useful tool to preoperatively predict the need of bone exposure and configuration of blood vessels with its correlation to cranial nerves in MVD.

Elastic Image Fusion Software to Coregister Preoperatively Planned Pedicle Screws With Intraoperative Computed Tomography Data for Image-Guided Spinal Surgery

BACKGROUND

For complex spinal cases, especially when robotic guidance is used, preoperative planning of pedicle screws can be helpful. Transfer of these preoperatively planned pedicle screws to intraoperative 3-dimensional imaging is challenging because of changes in anatomic alignment between preoperative supine and intraoperative prone imaging, especially when multiple levels are involved. In the spine, where each individual vertebra is subject to independent movement from adjacent level, rigid image fusion is confined to a single vertebra and can display fusion inaccuracies on adjacent levels. A novel elastic fusion algorithm is introduced to overcome these disadvantages. This study aimed to investigate image registration accuracy of preoperatively planned pedicle screws with an elastic fusion algorithm vs. rigid fusion for intraoperative placement with image-guided surgery.

METHODS

A total of 12 patients, were selected depending on the availability of a preoperative spinal computed tomography (CT) and an intraoperative AIRO CT scan (BrainLAB AG, Munich, Germany) of the same spinal region. To verify accuracy differences between rigid fusion and elastic fusion 76 bilateral screw trajectories were virtually defined in the preoperative CT image, and they were transferred via either rigid fusion or elastic fusion to the intraoperative CT scan. Accuracy of the transferred screws in the rigid and elastic fusion group was determined by measuring pedicle breaches on the intraoperative CT.

RESULTS

In the rigid fusion group 1.3% of screws showed a breach of less than 2 mm, 9.2% showed breaches between 2 and 4 mm, and 18.4% of the screws showed an error above 4 mm. The elastic fusion group showed no breaches and provided high accuracy between preoperative and intraoperative screw placement.

CONCLUSION

Elastic fusion provides high registration accuracy and represents a considerable step towards efficiency and safety in CT-based image-guided surgery.

LEVEL OF EVIDENCE

3.

Tethered Cord Syndrome After Myelomeningocele Repair: A Literature Update

Tethered cord syndrome (TCS) after myelomeningocele (MMC) repair (or secondary TCS) is a challenging condition characterized by neurological, orthopedic, and urological symptoms, which are combined with a low-lying position of the conus medullaris and damage to the stretched spinal cord owing to metabolic and vascular derangements. It has been reported that this syndrome affects, on average, 30% of children with MMC. In this review, we revisit the historical aspects of secondary TCS and highlight the most important concepts of diagnosis, treatment, and outcomes for secondary TCS as well as the current research regarding the impact of fetal MMC repair in the incidence and management of TCS. In the future, the development of synthetic models of TCS could shorten the learning curve of pediatric neurosurgeons, and research into the cellular proapoptotic features and increased inflammation biomarkers associated with TCS will also improve the treatment of this condition and minimize retethering of the spinal cord.

CT-MRI Image Fusion-Based Computer-Assisted Navigation Management of Communicative Tumors Involved the Infratemporal-Middle Cranial Fossa

Objective  Computed tomography (CT) and magnetic resonance imaging (MRI) are crucial for preoperative assessment of the three-dimensional (3D) spatial position relationships of tumor, vital vessels, brain tissue, and craniomaxillofacial bones precisely. The value of CT-MRI-based image fusion was explored for the preoperative assessment, virtual planning, and navigation surgery application during the treatment of communicative tumors involved the infratemporal fossa (ITF) and middle cranial fossa. Methods  Eight patients with infratemporal-middle cranial fossa communicative tumors (ICFCTs) were enrolled in this retrospective study. Plain CT, contrast CT, and MRI image data were imported into a workstation for image fusion, which were used for 3D image reconstruction, virtual surgical planning, and intraoperative navigation sequentially. Therapeutic effect was evaluated through the clinical data analysis of ICFCT patients after CT-MRI image fusion-based navigation-guided biopsy or surgery. Results  High-quality CT-MRI image fusion and 3D reconstruction were obtained in all eight cases. Image fusion combined with 3D image reconstruction enhanced the preoperative assessment of ICFCT, and improved the surgical performance via virtual planning. Definite pathological diagnosis was obtained in all four navigation-guided core needle biopsies. Complete removal of the tumor was achieved with one exception among the seven navigation-guided operations. Postoperative cerebrospinal fluid leakage occurred in one patient with recurrent meningioma. Conclusion  CT-MRI image fusion combined with computer-assisted navigation management, optimized the accuracy, safety, and surgical results for core needle biopsy and surgery of ICFCTs.

Evaluation of a novel elastic registration algorithm for spinal imaging data: A pilot clinical study

BACKGROUND

Rigid image coregistration is an established technique that allows spatial aligning. However, rigid fusion is prone to deformation of the imaged anatomies. In this work, a novel fully automated elastic image registration method is evaluated.

METHODS

Cervical CT and MRI data of 10 patients were evaluated. The MRI was acquired with the patient in neutral, flexed, and rotated head position. Vertebrawise rigid fusions were performed to transfer bony landmarks for each vertebra from the CT to the MRI space serving as a reference.

RESULTS

Elastic fusion of 3D MRI data showed the highest image registration accuracy (target registration error of 3.26 mm with 95% confidence). Further, an elastic fusion of 2D axial MRI data (<4.75 mm with 95% c.) was more reliable than for 2D sagittal sequences (<6.02 mm with 95% c.).

CONCLUSIONS

The novel method enables elastic MRI-to-CT image coregistration for cervical indications with changes of the head position.

Neurosurgical Virtual Reality Simulation for Brain Tumor Using High-definition Computer Graphics: A Review of the Literature

Simulation and planning of surgery using a virtual reality model is becoming common with advances in computer technology. In this study, we conducted a literature search to find trends in virtual simulation of surgery for brain tumors. A MEDLINE search for “neurosurgery AND (simulation OR virtual reality)” retrieved a total of 1,298 articles published in the past 10 years. After eliminating studies designed solely for education and training purposes, 28 articles about the clinical application remained. The finding that the vast majority of the articles were about education and training rather than clinical applications suggests that several issues need be addressed for clinical application of surgical simulation. In addition, 10 of the 28 articles were from Japanese groups. In general, the 28 articles demonstrated clinical benefits of virtual surgical simulation. Simulation was particularly useful in better understanding complicated spatial relations of anatomical landmarks and in examining surgical approaches. In some studies, Virtual reality models were used on either surgical navigation system or augmented reality technology, which projects virtual reality images onto the operating field. Reported problems were difficulties in standardized, objective evaluation of surgical simulation systems; inability to respond to tissue deformation caused by surgical maneuvers; absence of the system functionality to reflect features of tissue (e.g., hardness and adhesion); and many problems with image processing. The amount of description about image processing tended to be insufficient, indicating that the level of evidence, risk of bias, precision, and reproducibility need to be addressed for further advances and ultimately for full clinical application.

Assessment of the Accuracy and Errors of Head-Up Display by an Optical Neuronavigation System in Brain Tumor Surgery

BACKGROUND: A head-up display (HUD) in which navigational information is projected into the microscope view may enable surgeons to perform operations more efficiently. Projecting depictions of both tumor and important intracranial structures on the HUD may facilitate safe surgery.

OBJECTIVE: To investigate accuracy and errors regarding important intracranial structures, errors due to brain shifts, and preservation rates for important intracranial structures.

METHODS: A total of 184 surgeries in 172 patients were performed using this operation system. Postoperatively, we determined accuracy and errors for actual structures and virtual reality on the HUD and performed statistical analyses.

RESULTS: Preresection accuracy for important intracranial structures was highest for the internal carotid artery (ICA; 90.4%) and lowest for the posterior inferior cerebellar artery (53.6%). Differences between pre- and postresection accuracy were greatest, in descending order, for the cortical vein (P &lt; .0001), V4 segment of vertebral artery (P &lt; .0001), and anterior inferior cerebellar artery (P = .00780), whereas differences between pre- and postresection errors were smallest for the cranial nerve V (P = .500), middle cerebral artery (P = .0313), and ICA (P = .0313). Cases of poor preresection accuracy and large differences in pre- to postresection accuracy were seen in the prone position.

CONCLUSION: A reliable surgical resection rate was achieved using the HUD, and reliable preservation of important intracranial structures was also possible. Accuracy was concluded to be within an acceptable range.

Recurrent tethered cord: radiological investigation and management

INTRODUCTION

Recurrent tethered cord (RTC) is almost the rule after the repair of myelomeningocele and quite frequent after the repair of lipomyelomeningocele, resulting from the adhesions of the placode within a too narrow spinal canal. About one-third of patients with myelomeningocele and 10 % of those with spinal lipoma develop symptomatic RTC, mainly caused by the ischemic-metabolic injuries due to the cord stretching. The goal of this review is to provide information about the pathophysiology, the radiological picture, and the management of RTV according to the pertinent literature and the authors' experience.

RADIOLOGICAL INVESTIGATION

The magnetic resonance imaging (MRI) picture is characterized by a low position of the conus and by tethering of the spinal cord to the subcutaneous scar or to the inner surface of the spinal canal. The radiological work-up always includes brain MRI, to rule out other possible causes of late neurological deterioration (as shunt malfunction), and MRI of the whole spinal cord, to detect possible associated lesions (syringomyelia, dermoids, etc.). X-rays and/or computed tomography scan of the spine is required for the assessment of scoliosis or other bony malformations.

MANAGEMENT

The surgical treatment is planned after a multidisciplinary neurological, urological, orthopedic, physiatric, and radiological evaluation. The surgical detethering is carried out cautiously, possibly with electrophysiological intraoperative monitoring. Surgery ensures improvement or stability of the clinical picture in 70-80 % of cases, the remaining 20-30 % of patients needing multiple operations for their recovery. Complications may affect up to one-third of operated patients, being mainly represented by CSF leak, pseudomeningocele, and shunt malfunction.