Epilepsy surgery with intraoperative MRI at 1.5 T

Intraoperative magnetic resonance imaging in epilepsy surgery: A systematic review and meta-analysis

This systematic review investigated the added value of intraoperative magnetic resonance imaging (iMRI)-guidance in epilepsy surgery, compared to conventional non-iMRI surgery, with respect to the rate of gross total resection (GTR), postoperative seizure freedom, neurological deficits, non-neurological complications and reoperations. A comprehensive literature search was conducted using Medline, Embase, PubMed, and Cochrane Reviews databases. Randomized control trials, case control or cohort studies, and surgical case series published from January 1993 to February 2021 that reported on iMRI-guided epilepsy surgery outcomes for either adults or children were eligible for inclusion. Studies comparing iMRI-guided epilepsy surgery to non-iMRI surgery controls were selected for meta-analysis using random-effects models. Forty-two studies matched the selection criteria and were used for qualitative synthesis and ten of these were suitable for meta-analysis. Overall, studies included various 0.2-3.0 Tesla iMRI systems, contained small numbers with heterogenous clinical characteristics, utilized subjective GTR reporting, and had variable follow-up durations. Meta-analysis demonstrated that the use of iMRI-guidance led to statistically significant higher rates of GTR (RR = 1.31 [95% CI = 1.10-1.57]) and seizure freedom (RR = 1.44 [95% CI = 1.12-1.84]), but this was undermined by moderate to significant statistical heterogeneity between studies (I² = 55% and I² = 71% respectively). Currently, there is only level III-2 evidence supporting the use of iMRI-guidance over conventional non-iMRI epilepsy surgery, with respect to the studied outcomes.

3-T intraoperative MRI (iMRI) for pediatric epilepsy surgery

PURPOSE

Three-tesla intraoperative MRI (iMRI) is a promising tool that could help confirm complete resections and disconnections in pediatric epilepsy surgery, leading to improved outcomes. However, a large proportion of epileptogenic pathologies in children are poorly defined on imaging, which brings into question the utility of iMRI for these cases. Our aim was to compare postoperative seizure outcomes between iMRI- and non-iMRI-based epilepsy surgeries.

METHODS

We performed a comparative retrospective analysis of non-iMRI- versus iMRI-based epilepsy surgeries with 2-year follow-up. Patients were stratified into well-defined cases (WDCs), poorly defined cases (PDCs), and diffuse hemispheric cases (DHCs). Primary outcomes were rates of complete seizure freedom and surgical complications. Secondary outcomes included good (Engel class I/II) seizure outcome, extent of resection/disconnection, and operative duration. Regression models were used to adjust for confounding.

RESULTS

Thirty-nine iMRI-based and 39 non-iMRI-based surgeries were included. The distributions of age, sex, and lesion class in each era were similar, but the distributions of individual pathologies varied. Seizure freedom and complication rates at 2-year follow-up were not different between the groups, but Engel class I/II outcome was more common in the iMRI group. Extent of resection/disconnection and length of surgery were similar in both groups. PDCs had the worst outcomes, which were unchanged by the use of iMRI.

CONCLUSION

Three-tesla iMRI-based epilepsy surgery may have the potential to improve patient outcomes. However, we conclude that iMRI, in its current state of use at our institute, does not improve outcomes for children undergoing epilepsy surgery. Given that its use appears safe, further research on this technology is warranted, particularly for the most challenging PDCs.

Resection of cerebral gangliogliomas causing drug-resistant epilepsy: short- and long-term outcomes using intraoperative MRI and neuronavigation

OBJECT Cerebral gangliogliomas (GGs) are highly associated with intractable epilepsy. Incomplete resection due to proximity to eloquent brain regions or misinterpretation of the resection amount is a strong negative predictor for local tumor recurrence and persisting seizures. A potential method for dealing with this obstacle could be the application of intraoperative high-field MRI (iopMRI) combined with neuronavigation. METHODS Sixty-nine patients (31 female, 38 male; median age 28.5 ± 15.4 years) suffering from cerebral GGs were included in this retrospective study. Five patients received surgery twice in the observation period. In 48 of the 69 patients, 1.5-T iopMRI combined with neuronavigational guidance was used. Lesions close to eloquent brain areas were resected with the implementation of preoperative diffusion tensor imaging tractography and blood oxygenation level-dependent functional MRI (15 patients). RESULTS Overall, complete resection was accomplished in 60 of 69 surgical procedures (87%). Two patients underwent biopsy only, and in 7 patients, subtotal resection was accomplished because of proximity to critical brain areas. Excluding the 2 biopsies, complete resection using neuronavigation/iopMRI was documented in 33 of 46 cases (72%) by intraoperative imaging. Remnant tumor mass was identified intraoperatively in 13 of 46 patients (28%). After intraoperative second-look surgery, the authors improved the total resection rate by 9 patients (up to 91% [42 of 46]). Of 21 patients undergoing conventional surgery, 14 (67%) had complete resection without the use of iopMRI. Regarding epilepsy outcome, 42 of 60 patients with seizures (70%) became completely seizure free (Engel Class IA) after a median follow-up time of 55.5 ± 36.2 months. Neurological deficits were found temporarily in 1 (1.4%) patient and permanently in 4 (5.8%) patients. CONCLUSIONS Using iopMRI combined with neuronavigation in cerebral GG surgery, the authors raised the rate of complete resection in this series by 19%. Given the fact that total resection is a strong predictor of long-term seizure control, this technique may contribute to improved seizure outcome and reduced neurological morbidity.

Feasibility of anaesthetic provision for paediatric patients undergoing off-site intraoperative MRI-guided neurosurgery: the Singapore experience from 2009 to 2012

The benefits of using intraoperative magnetic resonance imaging (iMRI) for neurosurgery have been recognised. However, iMRI facilities are not available in all hospitals. For example, in Singapore iMRI is currently available only at the Singapore General Hospital, an adult hospital without facilities for intensive care management of patients less than 12 years of age. KK Women's and Children's Hospital is a dedicated children's hospital situated 6.3 km away from this facility. In order to obtain iMRI services for our paediatric patients, transport to Singapore General Hospital is required, with return to our hospital for postoperative management. Since July 2009 we have managed nine paediatric patients in this manner: three children with arteriovenous malformations and six children with brain tumours. There was no morbidity or mortality that could be attributed to the transport of patients either to or from Singapore General Hospital. Our experience suggests that with adequate planning and preparation, providing anaesthetic care and transporting children for off-site iMRI-guided neurosurgery is feasible and safe for selected children.

Integration of functional neuronavigation and intraoperative MRI in surgery for drug-resistant extratemporal epilepsy close to eloquent brain areas

Object

The authors performed a retrospective study to assess the impact of functional neuronavigation and intraoperative MRI (iMRI) on surgery of extratemporal epileptogenic lesions on postsurgical morbidity and seizure control.

Methods

Twenty-five patients (14 females and 11 males) underwent extratemporal resections for drug-resistant epilepsy close to speech/motor brain areas or adjacent to white matter tracts. The mean age at surgery was 34 years (range 12–67 years). The preoperative mean disease duration was 13.2 years. To avoid awake craniotomy, cortical motor-sensory representation was mapped during preoperative evaluation in 14 patients and speech representation was mapped in 15 patients using functional MRI. In addition, visualization of the pyramidal tract was performed in 11 patients, of the arcuate fascicle in 7 patients, and of the visual tract in 6 patients using diffusion tensor imaging. The mean minimum distance of tailored resection between the eloquent brain areas was 5.6 mm. During surgery, blood oxygen level–dependent imaging and diffusion tensor imaging data were integrated into neuronavigation and displayed through the operating microscope. The postoperative mean follow-up was 44.2 months.

Results

In 20% of these patients, further intraoperative resection was performed because of intraoperatively documented residual lesions according to iMRI findings. At the end of resection, the final iMRI scans confirmed achievement of total resection of the putative epileptogenic lesion in all patients. Postoperatively, transient complications and permanent complications were observed in 20% and 12% of patients, respectively. Favorable postoperative seizure control (Engel Classes I and II) was achieved in 84% and seizure freedom in 72% of these consecutive surgical patients.

Conclusions

By using functional neuronavigation and iMRI for treatment of epileptogenic brain lesions, the authors achieved a maximum extent of resection despite the lesions' proximity to eloquent brain cortex and fiber tracts in all cases. The authors' results underline possible benefits of this technique leading to a favorable seizure outcome with acceptable neurological deficit rates in difficult-to-treat extratemporal epilepsy.

Endoscopic endonasal resection of medial orbital lesions with intraoperative MRI

BACKGROUND

Various approaches have been described and used for operating on lesions in the orbit. The approach selection is based on the pathology in the orbit and its exact location. This study was performed to evaluate the endoscopic endonasal approach (EEA) for orbital lesions and application of intraoperative MRI (iMRI).

METHODS

Since 2006, the present authors have performed 614 endoscopic endonasal procedures. iMRI was used in 409 of these cases. Three orbital lesions approached via the endonasal route with a minimum follow-up of 1 year were analysed.

RESULTS

EEA was used in one case of intraconal cavernoma, one extraconal cavernoma and one solitary fibrous tumour in the orbit. The lesion was located medially to the optic nerve in all cases. Radical resection was achieved and the patient's vision was improved in two cases with a preoperative visual field deficit. iMRI was useful in two cases. In one case intraoperative MRI helped to find an intraconal lesion; in the other case iMRI led to evacuation of haemostatic material and blood, which was causing compression in the orbit.

CONCLUSIONS

The EEA should be considered whenever a lesion in the orbit is located medially to the optic nerve. Excellent results were achieved. iMRI proved useful in selected cases.

Intraoperative MR imaging in a case of a cervical spinal cord lesion

The aim of this article is to describe the feasibility of performing intraoperative MR imaging in patients with spinal cord lesions and the potential value of this technique. The authors report a case involving a 28-year-old man who presented with chronic cervical pain and pain along the ulnar side of the forearms during neck flexion. Findings on clinical examination were normal, but MR imaging revealed a multicystic cervical spinal cord lesion. Surgery was undertaken to open the cysts, evacuate old blood, and search for pathological tissue. Intraoperative MR imaging showed that the caudal cyst was not opened, and surgery was therefore continued. The caudal cyst was fenestrated and a suspected small cavernous malformation was removed. Electrophysiological monitoring was performed both before and after the intraoperative MR imaging. The use of intraoperative MR imaging changed the strategy of the procedure and helped the surgeon to safely enter all the cysts in the cervical cord.

Implementation and preliminary clinical experience with the use of ceiling mounted mobile high field intraoperative magnetic resonance imaging between two operating rooms

OBJECTIVE

Intraoperative magnetic resonance imaging (ioMRI) provides immediate feedback and quality assurance enabling the neurosurgeon to improve the quality of a range of neurosurgical procedures. Implementation of ioMRI is a complex and costly process. We describe our preliminary 16 months experience with the integration of an IMRIS movable ceiling mounted high field (1.5 T) ioMRI setup with two operating rooms.

METHODS

Aspects of implementation of our ioMRI and our initial 16 months of clinical experience in 180 consecutive patients were reviewed.

RESULTS

The installation of a ceiling mounted movable ioMRI between two operating rooms was completed in April 2008 at Barnes-Jewish Hospital in St. Louis. Experience with 180 neurosurgical cases (M:F-100:80, age range 1-79 years, 71 gliomas, 57 pituitary adenomas, 9 metastases, 11 other tumor cases, 4 Chiari decompressions, 6 epilepsy resections and 22 other miscellaneous procedures) demonstrated that this device effectively provided high quality real-time intraoperative imaging. In 74 of all 180 cases (41%) and in 54% of glioma resections, the surgeon modified the procedure based upon the ioMRI. Ninety-three percent of ioMRI glioma cases achieved gross/near total resection compared to 65% of non ioMRI glioma cases in this time frame.

CONCLUSION

A movable high field strength ioMRI can be safely integrated between two neurosurgical operating rooms. This strategy leads to modification of the surgical procedure in a significant number of cases, particularly for glioma surgery. Long-term follow up is needed to evaluate the clinical and financial impact of this technology in the field of neurosurgery.

Multifunctional surgical suite (MFSS) with 3.0 T iMRI: 17 months of experience

The 3T ioMRI in Prague is composed of two independent suites: the operating theatre and the 3T MR suite, both of which can and do work independently. They are connected by a double door and a special transportation system. The whole operating table is moved on rails to and from the MR gantry. Anaesthesiological equipment is built from paramagnetic material, which is also moved to and from the MR suite. The integral parts of the multifunctional surgical suite (MFSS) are the neuronavigation system, electrophysiological monitoring, surgical microscope with availability of indocyanin green angiography and fluorescence-guided glioma resection technique and endoscopy equipment. The operating theatre is equipped in a normal fashion with the exception of a head holder that is paramagnetic. MR radiologist and MR assistants are alerted approximately 30 min before the requested intraoperative and out-patient service is interrupted to clean the MR suite. The ioMRI takes 15-20 min and immediately after the door closes the out patient activity is resumed. Intraoperative MR was performed in 332 surgeries in the first 17 months of operation. The most frequent indications were pituitary adenomas, followed by gliomas. Other indications were less frequent and included meningiomas, cavernomas, aneurysms, epilepsy surgery, intramedullary lesions, non-pituitary sellar lesions, metastases and various other surgeries. In 332 cases no technical or medical complication connected with ioMRI was encountered.

Image guidance and neuromonitoring in neurosurgery

INTRODUCTION

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.

METHODS AND RESULTS

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.

CONCLUSION

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.

Application of intraoperative high-field magnetic resonance imaging in pediatric neurosurgery

OBJECT

Over the past decade, the use of intraoperative MR (iMR) imaging in the pediatric neurosurgical population has become increasingly accepted as an innovative and important neurosurgical tool. The authors summarize their experience using a mobile 1.5-T iMR imaging unit with integrated neuronavigation with the goal of identifying procedures and/or pathologies in which the application of this technology changed the course of surgery or modified the operative strategy.

METHODS

A database has been prospectively maintained for this patient population. The authors reviewed the hospital charts and imaging results for all patients in the database. This review revealed 105 neurosurgical procedures performed in 98 children (49 male and 49 female) between March 1998 and April 2008. Intradissection (ID) and/or quality assurance images were obtained at the discretion of the surgeon.

RESULTS

The median age at surgery was 12 years (4 months-18 years). One hundred intracranial and 5 spinal procedures were performed; 22 of these procedures were performed for recurrent pathology. Surgical planning scans were obtained for 102 procedures, and neuronavigation was used in 93 patients. The greatest impact of iMR imaging was apparent in the 55 procedures to resect neoplastic lesions; ID scans were obtained in 49 of these procedures. Further surgery was performed in 49% of the procedures during which ID scans had been obtained. A smaller proportion of ID scans in the different cranial pathology groups (5 of 21 epilepsy cases, 4 of 9 vascular cases) resulted in further resections to meet the surgical goal of the surgeon. Two ID scans obtained during 5 procedures for the treatment of spinal disease did not lead to any change in surgery. Postoperative scans did not reveal any acute adverse events. There was 1 intraoperative adverse event in which a Greenberg retractor was inadvertently left on during ID scanning but was removed after the scout scans.

CONCLUSIONS

The application of iMR imaging in the pediatric neurosurgical population allows, at minimum, the opportunity to perform less invasive surgical exposures. Its potential is greatest when its high-quality imaging ability is coupled with its superior neuronavigation capabilities, which permits tracking of the extent of resection of intracranial tumors and, to a lesser extent, other lesions during the surgical procedure.

Selective amygdalohippocampectomy: the trans-middle temporal gyrus approach

The most common surgical procedure for the mesial temporal lobe is the standard anterior temporal resection or what is commonly called the anterior temporal lobectomy. There are, however, a number of other more selective procedures for removal of the mesial temporal lobe structures (amygdala, hippocampus, and parahippocampal gyrus) that spare much of the lateral temporal neocortex. Included in these procedures collectively referred to as selective amygdalohippocampectomy are the transsylvian, subtemporal, and transcortical (trans-middle temporal gyrus) selective amygdalohippocampectomy. In this manuscript the author reviews some of the surgical details of the trans-middle temporal gyrus approach to the mesial temporal structures.

Surgical treatment of intractable epilepsy associated with focal cortical dysplasia

Focal cortical dysplasias (FCDs) are congenital malformations of cortical development that are a frequent cause of refractory epilepsy in both children and adults. With advances in structural and functional neuroimaging, these lesions are increasingly being identified as a cause of intractable epilepsy in patients undergoing surgical management for intractable epilepsy. Comprehensive histological classification of FCDs with the establishment of uniform terminology and reproducible pathological features has aided in our understanding of FCDs as an epilepsy substrate. Complete resection of FCDs and the associated epileptogenic zone can result in a good surgical outcome in the majority of patients.

[Interventional MR imaging: state of the art and technological advances]

Due to its excellent soft tissue contrast and lack of ionizing radiation, MR imaging is well suited for interventional procedures. MRI is being increasingly used for guidance during percutaneous procedures or surgery. Technical advances in interventional MR imaging are reviewed in this paper. Ergonomical factors with improved access to patients as well as advances in informatics, electronics and robotics largely explain this increasing role. Different elements are discussed from improved access to patients in the scanners to improved acquisition pulse sequences. Selected clinical applications and recent publications will be presented to illustrate the current status of this technique.

Image-guidance for surgical procedures

Contemporary imaging modalities can now provide the surgeon with high quality three- and four-dimensional images depicting not only normal anatomy and pathology, but also vascularity and function. A key component of image-guided surgery (IGS) is the ability to register multi-modal pre-operative images to each other and to the patient. The other important component of IGS is the ability to track instruments in real time during the procedure and to display them as part of a realistic model of the operative volume. Stereoscopic, virtual- and augmented-reality techniques have been implemented to enhance the visualization and guidance process. For the most part, IGS relies on the assumption that the pre-operatively acquired images used to guide the surgery accurately represent the morphology of the tissue during the procedure. This assumption may not necessarily be valid, and so intra-operative real-time imaging using interventional MRI, ultrasound, video and electrophysiological recordings are often employed to ameliorate this situation. Although IGS is now in extensive routine clinical use in neurosurgery and is gaining ground in other surgical disciplines, there remain many drawbacks that must be overcome before it can be employed in more general minimally-invasive procedures. This review overviews the roots of IGS in neurosurgery, provides examples of its use outside the brain, discusses the infrastructure required for successful implementation of IGS approaches and outlines the challenges that must be overcome for IGS to advance further.