Surgical treatment of low-grade gliomas in the intraoperative magnetic resonance imager

A Novel Portable, Mobile MRI: Comparison with an Established Low-Field Intraoperative MRI System

Background  MRI (magnetic resonance imaging) using low-magnet field strength has unique advantages for intraoperative use. We compared a novel, compact, portable MR imaging system to an established intraoperative 0.15 T system to assess potential utility in intracranial neurosurgery. Methods  Brain images were acquired with a 0.15 T intraoperative MRI (iMRI) system and a 0.064 T portable MR system. Five healthy volunteers were scanned. Individual sequences were rated on a 5-point (1 to 5) scale for six categories: contrast, resolution, coverage, noise, artifacts, and geometry. Results  Overall, the 0.064 T images (M = 3.4, SD = 0.1) had statistically higher ratings than the 0.15 T images (M = 2.4, SD = 0.2) ( p  < 0.01). All comparable sequences (T1, T2, T2 FLAIR and SSFP) were rated significantly higher on the 0.064 T and were rated 1.2 points (SD = 0.3) higher than 0.15 T scanner, with the T2 fluid-attenuated inversion recovery (FLAIR) sequences showing the largest increment on the 0.064 T with an average rating difference of 1.5 points (SD = 0.2). Scanning time for the 0.064 T system obtained images more quickly and encompassed a larger field of view than the 0.15 T system. Conclusions  A novel, portable 0.064 T self-shielding MRI system under ideal conditions provided images of comparable quality or better and faster acquisition times than those provided by the already well-established 0.15 T iMR system. These results suggest that the 0.064 T MRI has the potential to be adapted for intraoperative use for intracranial neurosurgery.

Combined use of intraoperative MRI and awake tailored microsurgical resection to respect functional neural networks: preliminary experience

INTRODUCTION

The combined use of intraoperative MRI and awake surgery is a tailored microsurgical resection to respect functional neural networks (mainly the language and motor ones). Intraoperative MRI has been classically considered to increase the extent of resection for gliomas, thereby reducing neurological deficits. Herein, we evaluated the combined technique of awake microsurgical resection and intraoperative MRI for primary brain tumours (gliomas, metastasis) and epilepsy (cortical dysplasia, non-lesional, cavernomas).

PATIENTS AND METHODS

Eighteen patients were treated with the commonly used "asleep awake asleep" (AAA) approach at Lille University Hospital, France, from November 2016 until May 2020. The exact anatomical location was insular with various extensions, frontal, temporal or fronto-temporal in 8 (44.4%), parietal in 3 (16.7%), fronto-opercular in 4 (22.2%), Rolandic in two (11.1%), and the supplementary motor area (SMA) in one (5.6%).

RESULTS

The patients had a mean age of 38.4 years (median 37.1, range 20.8-66.9). The mean surgical duration was 4.1 hours (median 4.2, range 2.6-6.4) with a mean duration of intraoperative MRI of 28.8 minutes (median 25, range 13-55). Overall, 61% (11/18) of patients underwent further resection, while 39% had no additional resection after intraoperative MRI. The mean preoperative and postoperative tumour volumes of the primary brain tumours were 34.7 cc (median 10.7, range 0.534-130.25) and 3.5 cc (median 0.5, range 0-17.4), respectively. Moreover, the proportion of the initially resected tumour volume at the time of intraoperative MRI (expressed as 100% from preoperative volume) and the final resected tumour volume were statistically significant (p= 0.01, Mann-Whitney test). The tumour remnants were commonly found posterior (5/9) or anterior (2/9) insular and in proximity with the motor strip (1/9) or language areas (e.g. Broca, 1/9). Further resection was not required in seven patients because there were no remnants (3/7), cortical stimulation approaching eloquent areas (3/7) and non-lesional epilepsy (1/7). The mean overall follow-up period was 15.8 months (median 12, range 3-36).

CONCLUSION

The intraoperative MRI and awake microsurgical resection approach is feasible with extensive planning and multidisciplinary collaboration, as these methods are complementary and synergic rather than competitive to improve patient oncological outcomes and quality of life.

Strategy of De Novo Design toward First-In-Class Imaging Agents for Simultaneously Differentiating Glioma Boundary and Grades

The extent of resection and tumor grade are two predominant prognostic factors for glioma. Fluorescent imaging is promising to facilitate accurate resection and simultaneous tumor grading. However, no probe fulfilling this task has been reported. Herein, we proposed a strategy of de novo design toward first-in-class fluorescent probes for simultaneously differentiating glioma boundary and grades. By bioinformatics analysis in combination with experimental validation, platelet-derived growth factor receptor β (PDGFRβ) was revealed as a promising biomarker for glioma imaging and grading. Then, fluorogenic probe PDGFP 1 was designed, guided by the structure-activity relationship study. Finally, the probe was demonstrated to stain glioma cells and tissues in the mice orthotopic glioma model with high selectivity over normal brain cells or tissues. Meanwhile, ex vivo experiments using patient-derived samples indicated that the fluorescence was significantly positively correlated with the tumor grades. This result highlighted the feasibility of the three-step de novo probe design strategy and suggested PDGFP 1 as a promising probe for simultaneously differentiating glioma boundary and grades, showing prospects of clinical translation.

5-ALA in Suspected Low-Grade Gliomas: Current Role, Limitations, and New Approaches

Radiologically suspected low-grade gliomas (LGG) represent a special challenge for the neurosurgeon during surgery due to their histopathological heterogeneity and indefinite tumor margin. Therefore, new techniques are required to overcome these current surgical drawbacks. Intraoperative visualization of brain tumors with assistance of 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX (PpIX) fluorescence is one of the major advancements in the neurosurgical field in the last decades. Initially, this technique was exclusively applied for fluorescence-guided surgery of high-grade glioma (HGG). In the last years, the use of 5-ALA was also extended to other indications such as radiologically suspected LGG. Here, we discuss the current role of 5-ALA for intraoperative visualization of focal malignant transformation within suspected LGG. Furthermore, we discuss the current limitations of the 5-ALA technology in pure LGG which usually cannot be visualized by visible fluorescence. Finally, we introduce new approaches based on fluorescence technology for improved detection of pure LGG tissue such as spectroscopic PpIX quantification fluorescence lifetime imaging of PpIX and confocal microscopy to optimize surgery.

Impact of combined use of intraoperative MRI and awake microsurgical resection on patients with gliomas: a systematic review and meta-analysis

Microsurgical resection of primary brain tumors located within or near eloquent areas is challenging. Primary aim is to preserve neurological function, while maximizing the extent of resection (EOR), to optimize long-term neurooncological outcomes and quality of life. Here, we review the combined integration of awake craniotomy and intraoperative MRI (IoMRI) for primary brain tumors, due to their multiple challenges. A systematic review of the literature was performed, in accordance with the Prisma guidelines. Were included 13 series and a total number of 527 patients, who underwent 541 surgeries. We paid particular attention to operative time, rate of intraoperative seizures, rate of initial complete resection at the time of first IoMRI, the final complete gross total resection (GTR, complete radiological resection rates), and the immediate and definitive postoperative neurological complications. The mean duration of surgery was 6.3 h (median 7.05, range 3.8-7.9). The intraoperative seizure rate was 3.7% (range 1.4-6; I^2 = 0%, P heterogeneity = 0.569, standard error = 0.012, p = 0.002). The intraoperative complete resection rate at the time of first IoMRI was 35.2% (range 25.7-44.7; I^2 = 66.73%, P heterogeneity = 0.004, standard error = 0.048, p < 0.001). The rate of patients who underwent supplementary resection after one or several IoMRI was 46% (range 39.8-52.2; I^2 = 8.49%, P heterogeneity = 0.364, standard error = 0.032, p < 0.001). The GTR rate at discharge was 56.3% (range 47.5-65.1; I^2 = 60.19%, P heterogeneity = 0.01, standard error = 0.045, p < 0.001). The rate of immediate postoperative complications was 27.4% (range 15.2-39.6; I^2 = 92.62%, P heterogeneity < 0.001, standard error = 0.062, p < 0.001). The rate of permanent postoperative complications was 4.1% (range 1.3-6.9; I^2 = 38.52%, P heterogeneity = 0.123, standard error = 0.014, p = 0.004). Combined use of awake craniotomy and IoMRI can help in maximizing brain tumor resection in selected patients. The technical obstacles to doing so are not severe and can be managed by experienced neurosurgery and anesthesiology teams. The benefits of bringing these technologies to bear on patients with brain tumors in or near language areas are obvious. The lack of equipoise on this topic by experienced practitioners will make it difficult to do a prospective, randomized, clinical trial. In the opinion of the authors, such a trial would be unnecessary and would deprive some patients of the benefits of the best available methods for their tumor resections.

State-of-the-art imaging for glioma surgery

Diffuse gliomas are infiltrative primary brain tumors with a poor prognosis despite multimodal treatment. Maximum safe resection is recommended whenever feasible. The extent of resection (EOR) is positively correlated with survival. Identification of glioma tissue during surgery is difficult due to its diffuse nature. Therefore, glioma resection is imaging-guided, making the choice for imaging technique an important aspect of glioma surgery. The current standard for resection guidance in non-enhancing gliomas is T2 weighted or T2w-fluid attenuation inversion recovery magnetic resonance imaging (MRI), and in enhancing gliomas T1-weighted MRI with a gadolinium-based contrast agent. Other MRI sequences, like magnetic resonance spectroscopy, imaging modalities, such as positron emission tomography, as well as intraoperative imaging techniques, including the use of fluorescence, are also available for the guidance of glioma resection. The neurosurgeon’s goal is to find the balance between maximizing the EOR and preserving brain functions since surgery-induced neurological deficits result in lower quality of life and shortened survival. This requires localization of important brain functions and white matter tracts to aid the pre-operative planning and surgical decision-making. Visualization of brain functions and white matter tracts is possible with functional MRI, diffusion tensor imaging, magnetoencephalography, and navigated transcranial magnetic stimulation. In this review, we discuss the current available imaging techniques for the guidance of glioma resection and the localization of brain functions and white matter tracts.

The value of visible 5-ALA fluorescence and quantitative protoporphyrin IX analysis for improved surgery of suspected low-grade gliomas

OBJECTIVE

In patients with suspected diffusely infiltrating low-grade gliomas (LGG), the prognosis is dependent especially on extent of resection and precision of tissue sampling. Unfortunately, visible 5-aminolevulinic acid (5-ALA) fluorescence is usually only present in high-grade gliomas (HGGs), and most LGGs cannot be visualized. Recently, spectroscopic probes were introduced allowing in vivo quantitative analysis of intratumoral 5-ALA-induced protoporphyrin IX (PpIX) accumulation. The aim of this study was to intraoperatively investigate the value of visible 5-ALA fluorescence and quantitative PpIX analysis in suspected diffusely infiltrating LGG.

METHODS

Patients with radiologically suspected diffusely infiltrating LGG were prospectively recruited, and 5-ALA was preoperatively administered. During resection, visual fluorescence and absolute tissue PpIX concentration (CPpIX) measured by a spectroscopic handheld probe were determined in different intratumoral areas. Subsequently, corresponding tissue samples were safely collected for histopathological analysis. Tumor diagnosis was established according to the World Health Organization 2016 criteria. Additionally, the tumor grade and percentage of tumor cells were investigated in each sample.

RESULTS

All together, 69 samples were collected from 22 patients with histopathologically confirmed diffusely infiltrating glioma. Visible fluorescence was detected in focal areas in most HGGs (79%), but in none of the 8 LGGs. The mean CPpIX was significantly higher in fluorescing samples than in nonfluorescing samples (0.693 μg/ml and 0.008 μg/ml, respectively; p < 0.001). A significantly higher mean percentage of tumor cells was found in samples with visible fluorescence compared to samples with no fluorescence (62% and 34%, respectively; p = 0.005), and significant correlation of CPpIX and percentage of tumor cells was found (r = 0.362, p = 0.002). Moreover, high-grade histology was significantly more common in fluorescing samples than in nonfluorescing samples (p = 0.001), whereas no statistically significant difference in mean CPpIX was noted between HGG and LGG samples. Correlation between maximum CPpIX and overall tumor grade was highly significant (p = 0.005). Finally, 14 (40%) of 35 tumor samples with no visible fluorescence and 16 (50%) of 32 LGG samples showed significantly increased CPpIX (cutoff value: 0.005 μg/ml).

CONCLUSIONS

Visible 5-ALA fluorescence is able to detect focal intratumoral areas of malignant transformation, and additional quantitative PpIX analysis is especially useful to visualize mainly LGG tissue that usually remains undetected by conventional fluorescence. Thus, both techniques will support the neurosurgeon in achieving maximal safe resection and increased precision of tissue sampling during surgery for suspected LGG.Clinical trial registration no.: NCT01116661 (clinicaltrials.gov).

Intraoperative high-field magnetic resonance imaging, multimodal neuronavigation, and intraoperative electrophysiological monitoring-guided surgery for treating supratentorial cavernomas

Objective

To determine the beneficial effects of intraoperative high-field magnetic resonance imaging (MRI), multimodal neuronavigation, and intraoperative electrophysiological monitoring-guided surgery for treating supratentorial cavernomas.

Methods

Twelve patients with 13 supratentorial cavernomas were prospectively enrolled and operated while using a 1.5 T intraoperative MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring. All cavernomas were deeply located in subcortical areas or involved critical areas. Intraoperative high-field MRIs were obtained for the intraoperative “visualization” of surrounding eloquent structures, “brain shift” corrections, and navigational plan updates.

Results

All cavernomas were successfully resected with guidance from intraoperative MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring. In 5 cases with supratentorial cavernomas, intraoperative “brain shift” severely deterred locating of the lesions; however, intraoperative MRI facilitated precise locating of these lesions. During long-term (>3 months) follow-up, some or all presenting signs and symptoms improved or resolved in 4 cases, but were unchanged in 7 patients.

Conclusions

Intraoperative high-field MRI, multimodal neuronavigation, and intraoperative electrophysiological monitoring are helpful in surgeries for the treatment of small deeply seated subcortical cavernomas.

Intraoperative magnetic resonance imaging in pediatric neurosurgery: safety and utility

OBJECTIVE The use of high-field intraoperative MRI has been largely studied for the treatment of intracranial tumors in adult patients. In this study, the authors investigated the safety, advantages, and limitations of high-field iMRI for cranial neurosurgical procedures in pediatric patients, with particular attention to craniopharyngiomas and gliomas. METHODS The authors performed 82 surgical procedures in patients under 16 years of age (range 0.8-15 years) over an 8-year period (2007-2014) using iMRI. The population was divided into 3 groups based on the condition treated: sellar region tumors (Group 1), gliomas (Group 2), and other pathological entities (Group 3). The patients' pre- and postoperative neurological status, the presence of residual tumor, the number of intraoperative scans, and complications were evaluated. RESULTS In Group 1, gross-total resection (GTR) was performed in 22 (88%) of the procedures and subtotal resection (STR) in 3 (12%). In Group 2, GTR, STR, and partial resection (PR) were performed, respectively, in 15 (56%), 7 (26%), and 5 (18%) of the procedures. In Group 3, GTR was performed in 28 (93%) and STR in 2 (7%) of the procedures. In cases of craniopharyngioma (Group 1) and glioma (Group 2) in which a complete removal was planned, iMRI allowed localization of residual lesions and attainment of the surgical goal through further resection, respectively, in 18% and 27% of the procedures. Moreover, in gliomas the resection could be extended from partial to subtotal in 50% of the cases. In 17% of the patients in Group 3, iMRI enabled the identification and further removal of tumor remnants. There was no intra- or postoperative complication related to the use of iMRI despite special technical difficulties in smaller children. CONCLUSIONS In this study, the use of iMRI in children proved to be safe. It was most effective in increasing the extent of tumor resection, especially in patients with low-grade gliomas and craniopharyngiomas. The most prominent disadvantage of high-field iMRI was the limitation with respect to operative positioning due to the configuration of the surgical table.

Management of low-grade gliomas: a review of patient-perceived quality of life and neurocognitive outcome

Low-grade glioma (LGG) comprises nearly 20% of all central nervous system glial tumors, with approximately 2000-3000 patients diagnosed annually in the United States. Because of their infiltrative ability and aggressive nature, the average 10-year survival is 30% when <90% of the tumor is resected. Since the 1970s, prognosis for LGGs has improved significantly. This improvement is primarily attributable to earlier diagnoses via magnetic resonance imaging scanning, increased awareness of the more favorable oligo component, technical advances in intraoperative neurosurgery, and stratification for young age. Using a number of prognostic factors, LGGs have been classified into low-risk and high-risk subgroups. Optimal therapy for patients with low-risk, supratentorial grade II glioma remains a highly controversial issue in the neuro-oncology community. The concerns regarding the toxicity of therapy often outweigh the benefits of delaying tumor progression. The recommendation for observation is made without full prospective understanding of the impact of radiologic tumor progression on the quality of life (QOL), neurocognitive function (NCF), seizure control, and functional status of these patients. We present a review of the current knowledge of the management of LGG with emphasis upon patient-reported outcomes of QOL, NCF, and seizure control. We also discuss current clinical trials with proposals to evaluate QOL, NCF, and seizure control in patients undergoing observation alone after newly diagnosed low-risk LGG or treatment options for those patients in the high-risk group.

Intraoperative magnetic resonance spectroscopy for identification of residual tumor during low-grade glioma surgery: clinical article

OBJECT

The authors had previously shown that 3-T intraoperative MRI (ioMRI) detects residual tumor tissue during low-grade glioma and that it helps to increase the extent of resection. In a proportion of their cases, however, the ioMRI disclosed T2-hyperintense areas at the tumor resection border after the initial resection attempt and prompted a differential diagnosis between residual tumor and nontumoral changes. To guide this differential diagnosis the authors used intraoperative long-TE single-voxel proton MR spectroscopy (ioMRS) and tested the correlation of these findings with findings from pathological examination of resected tissue.

METHODS

Patients who were undergoing surgery for hemispheric or insular WHO Grade II gliomas and were found to have T2 changes around the resection cavity at the initial ioMRI were prospectively examined with ioMRS and biopsies were taken from corresponding localizations. In 14 consecutive patients, the ioMRS diagnosis in 20 voxels of interest was tested against the histopathological diagnosis. Intraoperative diffusion-weighted imaging (ioDWI) was also performed, as a part of the routine imaging, to rule out surgically induced changes, which could also appear as T2 hyperintensity.

RESULTS

Presence of tumor was documented in 14 (70%) of the 20 T2-hyperintense areas by histopathological examination. The sensitivity of ioMRS for identifying residual tumor was 85.7%, the specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 75%. The specificity of ioDWI for surgically induced changes was high (100%), but the sensitivity was only 60%.

CONCLUSIONS

This is the first clinical series to indicate that ioMRS can be used to differentiate residual tumor from nontumoral changes around the resection cavity, with high sensitivity and specificity.

Optimizing costs of intraoperative magnetic resonance imaging. A series of 29 glioma cases

PURPOSE

The goal of this study was to develop a method to reduce the costs of intraoperative high-field magnet resonance imaging (iMRI). The results of a series of 29 gliomas removed with this technique are presented.

METHODS

A series of 29 patients with brain gliomas were operated on using a low-cost method of high-field intraoperative MRI (Signa 1.5 T. MR Excite, GE Inc.). The patients were transported during surgery to the neuroradiological department through a specially located lift in order to perform the intraoperative examinations ("outside iMRI"). The time required for the procedure as well as the possible related complications, such as infection, were analyzed.

RESULTS

After studying the intraoperative images, additional tumor resection was needed in 12 of the 29 patients. The median time required to perform the iMRI was 25 min. There was no infection or other complications related to the procedure in this series.

CONCLUSIONS

This method offers all clinical advantages of high-field iMRI inside of the operating room, with very low costs and additional advantage of integrating the neurosurgical/ neuroradiological teams. This strategy will give an alternative to several neurosurgical departments in the world to perform high-quality iMRI at very low cost.

Present day's standards in microsurgery of low-grade gliomas

Low-grade gliomas are slow growing intrinsic lesions that induces a progressive functional reshaping of the brain. Surgical removal of these lesions requires the combined efforts of a multidiscipinary team of neurosurgeon, neuroradiologist, neuropsychologist, neurophysiologist, and neurooncologists that all together contribute in the definition of the location, extension, and extent of functional involvement that a specific lesion has induced in a particular patient. Each tumor has induced particular and specific changes of the functional network, that varies among patients. This requires that each treatment plan should be tailored to the tumor and to the patient. When this is reached, surgery should be accomplished according to functional and anatomical boundaries, and has to aim to the maximal resection with the maximal patient functional preservation. This can be reached at the time of the initial surgery, depending on the functional organization of the brain, or may require additional surgeries, eventually intermingled with adjuvant treatments. The use of so called brain mapping techniques extend surgical indications, improve extent of resection with greater oncological impact, minimization of morbidity and increase in quality of life. To achieve the goal of a satisfactory tumor resection associated with the full preservation of the patients abilities, a series of neuropsychological, neurophysiological, neuroradiological and intraoperative investigations have to be performed. In this chapter, we will describe the rationale, the indications and the modality for performing a safe and rewarding surgical removal of low-grade gliomas by using these techniques, as well as the functional and oncological results.

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.

Functional magnetic resonance imaging-guided brain tumor resection

OBJECTIVES

We evaluated the safety and efficacy of using functional magnetic resonance imaging (fMRI) brain activation data obtained at both 1.5 and 3 T to guide brain tumor resections using 1.5-T intraoperative MRI (ioMRI) guidance.

MATERIALS AND METHODS

From January 1997 to March 2006, fMRI was performed on 29 patients before attempted brain tumor resection. Functional MRI was used to identify and coregister areas of brain activation for motor (n = 18), speech (n = 6), motor and speech (n = 4), and short-term memory and speech (n = 1) with respect to the tumor using a 1.5-T and two 3-T MRI scanners. Surgical resection was accomplished using 2 different 1.5-T ioMRI systems. The appropriate MRI scan sequences were obtained during surgery to determine and maximize the extent of the surgical resection depending on the tumor type.

RESULTS

Of 29 patients, 20 (69%) had radiographically complete fMRI-guided tumor resections and 2 (7%) had successful MRI-guided brain biopsy because of the proximity of their astrocytomas to the eloquent cortex. The tumors were oligodendrogliomas (n = 16), astrocytomas (n = 4), meningiomas (n = 3), glioblastomas multiforme (n = 2), a pleomorphic astrocytoma (n = 1), and a dysembryoplastic neuroepithelial tumor (n = 1). The preoperative fMRI data were accurate in all cases. After tumor resection, 7 patients (26%) had transient neurologic deficits that resolved completely within 1 month of the surgical procedure in all cases. No adverse events associated with ferromagnetic instrumentation occurred.

CONCLUSIONS

Functional MRI was accurate for localizing areas of eloquent neurologic function before ioMRI-guided brain tumor resection.

Functional magnetic resonance imaging-guided resection of low-grade gliomas

BACKGROUND

We sought to determine the safety and efficacy of using functional magnetic resonance imaging (fMRI) to guide the resection of low-grade gliomas (LGG).

METHODS

From September 1997 to February 2003, fMRI was performed in 16 patients (age, 15-43 years) before an attempted surgical resection of LGG. Functional imaging was used to identify and coregister eloquent cortices pertinent to motor (10), speech (3), motor and speech (2), and short-term memory and speech (1) activation with respect to the tumor using a 1.5-T interventional MRI system. Intraoperatively acquired T(2)-weighted and turbo-fluid attenuated inversion recovery images were used to assess the completeness of surgical resection.

RESULTS

Tumors included 10 oligodendrogliomas, 4 astrocytomas, 1 dysembryoplastic neuroepithelial tumor, and 1 pleomorphic xanthoastrocytoma. In every case, the preoperative brain activation study accurately determined the location of neurologic function. After surgery, one patient had a transient hemiparesis and another had a temporary apraxia. Ten patients had radiographically complete resections and 5 with oligodendrogliomas had incomplete resections because of the proximity of their tumors to functional areas. Only one patient with an astrocytoma in the motor strip received postoperative radiation therapy. To date, radiographic tumor progression has not been seen in any patient with either a partial or a complete resection with a median follow-up of 25 months (range, 12-87 months).

CONCLUSIONS

Functional MRI was accurate for identifying areas of neurologic function before surgical resection of LGG. Patients with complete radiographic resections or with incompletely resected oligodendrogliomas can be safely followed radiographically after surgery. Radiation therapy was reserved for infiltrating astrocytomas that were not completely resectable.

Craniotomy under local anesthesia and monitored conscious sedation for the resection of tumors involving eloquent cortex

OBJECTIVE

Resection or even biopsy of an intra-axial mass lesion in close relationship to eloquent cortex carries a major risk of neurological deficit. We have assessed the safety and effectiveness of craniotomy under local anesthesia and monitored conscious sedation for the resection of tumors involving eloquent cortex.

METHODS

We have performed a retrospective review of a consecutive series of 157 adult patients who underwent craniotomy under local anesthesia by one surgeon (P.M.B.) at Brigham and Women's Hospital in Boston. All patients had tumors in close proximity to eloquent cortex, including speech, motor, primary sensory, or visual cortex. In most cases the lesion was considered inoperable by the referring surgeon. All resection was verified by post-operative imaging approximately one month after surgery and all cases were reviewed by an independent neurosurgeon (A.D.).

RESULTS

In 122 cases, brain mapping was performed to identify eloquent cortex and in the remainder neurological monitoring was maintained during the procedure. Radiological gross total resection was achieved in 57% of patients and greater than 80% resection was achieved in 23%. Thus 4 out of 5 of patients had major resection despite the close relationship of tumor to eloquent cortex. In 13%, less than 80% of tumor was removed because of danger of neurological deficit. In 7% of patients, only a biopsy could be done because of infiltration into eloquent cortex that could only be assessed at surgery. In 76 patients with pre-operative neurological deficits, there was complete resolution of these deficits in 33%, improvement in 32%, no change in 28%, and long-term worsening in 8%. Among 81 patients with no pre-operative neurological deficit, 1 patient suffered a major permanent neurological deficit, and 2 developed minor deficits. There was a transient post-operative deficit in one-third of cases, but this had resolved at one month in all but three patients. Monitored conscious sedation was performed without anesthetic complications using midazolam, sufentanyl and fentanyl with or without propofol. Only one case needed to be converted to general anesthesia. Patient satisfaction with the procedure has been good. Operating time and hospital stay were lower than the mean for brain tumor craniotomy at this hospital.

CONCLUSIONS

Tumor surgery with conscious sedation is a safe technique that allows maximal resection of lesions in close anatomical relationship to eloquent cortex, with a low risk of new neurological deficit. Only 7% of intrinsic cortical tumors were ineligible for partial or complete resection with this technique.