Neurosurgical considerations in supratentorial low-grade gliomas: experience with 175 patients

Awake craniotomy in glioma surgery: is it necessary?

INTRODUCTION

The awake craniotomy has evolved from its humble beginnings in ancient cultures to become one of the most eloquent modern neurosurgical procedures. The development of intraoperative mapping techniques like direct electrostimulation of the cortex and subcortical white matter have further argued for its place in the neurosurgeon's armamentarium. Yet the suitability of the awake craniotomy with intraoperative functional mapping (ACWM) to optimize oncofunctional balance after peri-eloquent glioma resection continues to be a topic of active investigation as new methods of intraoperative monitoring and some unfavorable outcome data question its necessity.

EVIDENCE ACQUISITION

The neurosurgery and anesthesiology literatures were scoured for English-language studies that analyzed or reviewed the ACWM or its components as applied to glioma surgery via the PubMed, ClinicalKey, and OvidMEDLINE® databases or via direct online searches of journal archives.

EVIDENCE SYNTHESIS

Information on background, conceptualization, standard techniques, and outcomes of the ACWM were provided and compared. We parceled the procedure into its components and qualitatively described positive and negative outcome data for each. Findings were presented in the context of each study without attempt at quantitative analysis or reconciliation of heterogeneity between studies. Certain illustrative studies were highlighted throughout the review. Overarching conclusions were drawn based on level of evidence, expert opinion, and predominate concordance of data across studies in the literature.

CONCLUSIONS

Most investigators and studies agree that the ACWM is the best currently available approach to optimize oncofunctional balance in this difficult-to-treat patient population. This qualitative review synthesizes the most currently available data on the topic to provide contemporaneous insight into how and why the ACWM has become a favorite operation of neurosurgeons worldwide for the resection of gliomas from eloquent brain.

Spontaneous and therapeutic prognostic factors in adult hemispheric World Health Organization Grade II gliomas: a series of 1097 cases

Object

The spontaneous prognostic factors and optimal therapeutic strategy for WHO Grade II gliomas (GIIGs) have yet to be unanimously defined. Specifically, the role of resection is still debated, most notably because the actual amount of resection has seldom been assessed.

Methods

Cases of GIIGs treated before December 2007 were extracted from a multicenter database retrospectively collected since January 1985 and prospectively collected since 1996. Inclusion criteria were a patient age ≥ 18 years at diagnosis, histological diagnosis of WHO GIIG, and MRI evaluation of tumor volume at diagnosis and after initial surgery. One thousand ninety-seven lesions were included in the analysis. The mean follow-up was 7.4 years since radiological diagnosis. Factors significant in a univariate analysis (with a p value ≤ 0.1) were included in the multivariate Cox proportional hazard regression model analysis.

Results

At the time of radiological diagnosis, independent spontaneous factors of a poor prognosis were an age ≥ 55 years, an impaired functional status, a tumor location in a nonfrontal area, and, most of all, a larger tumor size. When the study starting point was set at the time of first treatment, independent favorable prognostic factors were limited to a smaller tumor size, an epileptic symptomatology, and a greater extent of resection.

Conclusions

This large series with its volumetric assessment refines the prognostic value of previously stressed clinical and radiological parameters and highlights the importance of tumor size and location. The results support additional arguments in favor of the predominant role of resection, in accordance with recently reported experiences.

Intraoperative mapping for tumor resection

This article describes the rationale, indications, and modality for intraoperative brain mapping for safe and effective surgical removal of tumors located within functional brain areas.

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.

Intraoperative mapping and monitoring of brain functions for the resection of low-grade gliomas: technical considerations

Low-grade gliomas ([LGGs] WHO Grade II) are slow-growing intrinsic cerebral lesions that diffusely infiltrate the brain parenchyma along white matter tracts and almost invariably show a progression toward malignancy. The treatment of these tumors forces the neurosurgeon to face uncommon difficulties and is still a subject of debate. At the authors' institution, resection is the first option in the treatment of LGGs. It requires the combined efforts of a multidisciplinary team of neurosurgeons, neuroradiologists, neuropsychologists, and neurophysiologists, who together contribute to the definition of the location, extension, and extent of functional involvement that a specific lesion has caused in a particular patient. In fact, each tumor induces specific modifications of the brain functional network, with high interindividual variability. This requires that each treatment plan is tailored to the characteristics of the tumor and of the patient. Consequently, surgery is performed according to functional and anatomical boundaries to achieve the maximal resection with maximal functional preservation. The identification of eloquent cerebral areas, which are involved in motor, language, memory, and visuospatial functions and have to be preserved during surgery, is performed through the intraoperative use of brain mapping techniques. The use of these techniques extends surgical indications and improves the extent of resection, while minimizing the postoperative morbidity and safeguarding the patient's quality of life. In this paper the authors present their paradigm for the surgical treatment of LGGs, focusing on the intraoperative neurophysiological monitoring protocol as well as on the brain mapping technique. They briefly discuss the results that have been obtained at their institution since 2005 as well as the main critical points they have encountered when using this approach.

Intérêt de la stimulation électrique directe dans la chirurgie des gliomes en zones fonctionnelles

Glioma surgery in functional areas has undergone a dramatic development these last few years, thanks to improvements in both intraoperative functional imaging and direct electrical stimulation of cortical areas or association pathways. The goal of these techniques to achieve complete as possible surgical removal of tumors located in eloquent areas (sensitive, motor and language areas) with minimal risk of permanent sequelae. To be reliable, a rigorous methodology is required. Current cortical mapping is very easy to achieve, whereas mapping of association pathways will require much more experience. In case of tumors located in somatosensorial or language areas, the difficulties related to accurate sub cortical localization are combined with these of local anesthesia and the best task choice to evaluate the integrity of cognitive functions. These functional techniques allow total or sub total removal in 52% to 76.2% of patients. Transient worsening is observed in 13% to 80% of the patients; the rate of permanent sequelae averages 4%.

Usefulness of intraoperative electrical subcortical mapping during surgery for low-grade gliomas located within eloquent brain regions: functional results in a consecutive series of 103 patients

OBJECT

Although a growing number of authors currently advocate surgery to treat low-grade gliomas, controversy still persists, especially because of the risk of inducing neurological sequelae when the tumor is located within eloquent brain areas. Many researchers performing preoperative neurofunctional imaging and intraoperative electrophysiological methods have recently reported on the usefulness of cortical functional mapping. Despite the frequent involvement of subcortical structures by these gliomas, very few investigators have specifically raised the subject of fiber tracking. The authors in this report describe the importance of mapping cortical and subcortical functional regions by using intraoperative real-time direct electrical stimulations during resection of low-grade gliomas.

METHODS

Between 1996 and 2001, 103 patients harboring a corticosubcortical low-grade glioma in an eloquent area, with no or only mild deficit, had undergone surgery during which intraoperative electrical mapping of functional cortical sites and subcortical pathways was performed throughout the procedure. Both eloquent cortical areas and corresponding white fibers were systematically detected and preserved, thus defining the resection boundaries. Despite an 80% rate of immediate postoperative neurological worsening, 94% of patients recovered their preoperative status within 3 months--10% even improved--and then returned to a normal socioprofessional life. Eighty percent of resections were classified as total or subtotal based on control magnetic resonance images.

CONCLUSIONS

The use of functional mapping of the white matter together with cortical mapping allowed the authors to optimize the benefit/risk ratio of surgery of low-grade glioma invading eloquent regions. Given that preoperative fiber tracking with the aid of neuroimaging is not yet validated, we used intraoperative real-time cortical and subcortical stimulations as a valuable adjunct to the other mapping methods.

Surgical treatment of patients with low-grade astrocytomas and medically intractable seizures

OBJECTIVE

Low-grade astrocytomas can present with seizures that respond poorly to antiseizure medications, with a consequent reduction in the quality of life, because of both seizures and the medication's side-effects. We report our experience with operative treatment of such patients.

SUBJECTS AND METHODS

Five patients (two children and three adults) with supratentorial low-grade astrocytomas associated with severe seizures were operated on. We followed the effects of the operation on post-operative neurological deficit, seizure frequency and the quality of life.

RESULTS

No serious neurological complications followed the operations. The patients were followed for a median period of 12 months (6-46). Post-operatively, three of the patients became seizure-free, one experiences only auras, and one had a great reduction in seizure frequency and severity. All patients reported great improvement in their quality of life.

CONCLUSION

Resections of low-grade astrocytomas in patients with medically intractable seizures are safe procedures that effectively control seizures in the majority of patients, resulting in significant improvement in the patients' quality of life.

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.