Low-grade hemispheric gliomas in adults: a critical review of extent of resection as a factor influencing outcome

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.

Imaging gliomas with positron emission tomography and single-photon emission computed tomography

Over the last two decades the large volume of research involving various brain tracers has shed invaluable light on the pathophysiology of cerebral neoplasms. Yet the question remains as to how best to incorporate this newly acquired insight into the clinical context. Thallium is the most studied radiotracer with the longest track record. Many, but not all studies, show a relationship between (201)Tl uptake and tumor grade. Due to the overlap between tumor uptake and histologic grades, (201)Tl cannot be used as the sole noninvasive diagnostic or prognostic tool in brain tumor patients. However, it may help differentiating a high-grade tumor recurrence from radiation necrosis. MIBI is theoretically a better imaging agent than (201)Tl but it has not convincingly been shown to differentiate tumors according to grade. MDR-1 gene expression as demonstrated by MIBI does not correlate with chemoresistance in high grade gliomas. Currently, MIBI's clinical role in brain tumor imaging has yet to be defined. IMT, a radio-labeled amino acid analog, may be useful for identifying postoperative tumor recurrence and, in this application, appears to be a cheaper, more widely available tool than positron emission tomography (PET). However, its ability to accurately identify tumor grade is limited. 18 F-2-Fluoro-2-deoxy-d-glucose (FDG) PET predicts tumor grade, and the metabolic activity of brain tumors has a prognostic significance. Whether FDG uptake has an independent prognostic value above that of histology remains debated. FDG-PET is effective in differentiating recurrent tumor from radiation necrosis for high-grade tumors, but has limited value in defining the extent of tumor involvement and recurrence of low-grade lesions. Amino-acid tracers, such as MET, perform better for this purpose and thus play a complementary role to FDG. Given the poor prognosis of patients with gliomas, particularly with high-grade lesions, the overall clinical utility of single photon emission computed tomography (SPECT) and PET in characterizing recurrent lesions remains dependent on the availability of effective treatments. These tools are thus mostly suited to the evaluation of treatment response in experimental protocols designed to improve the patients' outcome.

Incidence and clinical evolution of postoperative deficits after volumetric stereotactic resection of glial neoplasms involving the supplementary motor area

OBJECTIVE

We report the incidence and clinical evolution of postoperative deficits and supplementary motor area (SMA) syndrome after volumetric stereotactic resection of glial neoplasms involving the posterior one-third of the superior frontal convolution. We investigated variables that may be associated with the occurrence of SMA syndrome.

METHODS

The postoperative clinical status of 27 consecutive patients who underwent resection of SMA gliomas was retrospectively reviewed. Neurological examination results were recorded 1 day, 1 week, 1 month, and 6 months postoperatively. The extent of tumor resection, the percentage of SMA resection, violation of the cingulate gyrus, and operative complications were tabulated.

RESULTS

The overall incidence of SMA-related deficits was 26% (7 of 27 patients), with 3 patients having complete SMA syndrome and 4 patients having partial SMA syndrome. Two additional patients (7.5%) had other postoperative deficits, including one with mild facial weakness and one with transient aphasia. The resection of low-grade gliomas was associated with a higher incidence of SMA syndrome, an outcome that likely reflects more complete removal of functional SMA cortex in this subset of patients. Intraoperative monitoring localized the precentral sulcus within the preoperatively defined tumor volume in 6 (22%) of 27 patients, thereby precluding gross total resection. All 27 patients had excellent outcomes at the 6-month follow-up examination.

CONCLUSION

When the resection of SMA gliomas is limited to the radiographic tumor boundaries, the incidence and severity of SMA syndrome may be minimized. With the use of these resection parameters, patients with high-grade SMA gliomas are unlikely to experience SMA syndrome. These findings are helpful in the preoperative counseling of patients who are to undergo cytoreductive resection of SMA gliomas.

On the issue of early and aggressive treatment in grade 2 gliomas

PURPOSE

To study the effects of surgery and timing of radiotherapy on patient survival in grade 2 gliomas.

METHODS

One hundred and eighty-nine patients with diffuse astrocytomas, oligoastrocytomas, and oligodendrogliomas, World Health Organization grade 2, treated between 1982 and 2000 were identified. The impact of treatment given and clinical parameters were studied in univariate- and multivariate survival analyses.

RESULTS

Median survival for the whole patient sample was 6.4 years and the 5-year survival rate was 60%. Macroscopic total resection was beneficial in the univariate analysis (P=0.03) but not when adjusting for confounders. Early subtotal resection did not prolong survival. Early radiotherapy was associated with a shorter survival time compared to delayed or no irradiation (P=0.004). However, this difference was mainly due to an unequal distribution of prognostic factors and was not significant in the multivariate analysis. The most important predictors for long survival time were young age ( P<0.001), oligodendroglioma histology ( P<0.001), and small tumour size ( P=0.02).

CONCLUSIONS

Early conventional treatment with surgery and radiotherapy had no positive effect on patient survival. This opens up the possibility of trying and evaluating other first-line treatment regimens in this disease.

Primary brain tumours in adults

The most frequent primary brain tumours in adults are gliomas and primary CNS lymphomas. In gliomas, molecular genetic analysis plays an increasing part in classification and treatment planning, a feature well illustrated by the chemosensitive oligodendrogliomas. Unfortunately, management of glioblastoma is still mainly palliative. Incidence of primary CNS lymphoma has increased strikingly in the past 20 years; substantial progress has been achieved in patients who are immunocompetent with the addition of methotrexate-based chemotherapy to radiotherapy, but the potential neurotoxic effects of this combination in elderly patients is worrisome.

Awake craniotomy in glioma surgery

Awake craniotomy is the cheapest and most reliable method to ensure neurological integrity in cerebral gliomas that infiltrate or come close to the eloquent areas of the brain, allowing (a) the localization of eloquent cortical areas by electrical stimulation and epileptic foci by cortical recording, and (b) the monitoring of the functional integrity of awake patients while aiming at subtotal removal of the gliomatous tissue. In addition, awake craniotomy opens a brief but unique window to the living brain for (a) basic neuroscience, including verification of preoperative functional imaging data and recording of electrophysiological correlates of mental processes, and for (b) applied research, including development of innovative instrumentation for brain recording and monitoring as well as screening for potential areas to be modulated in movement disorders and chronic pain.

Treatment of low-grade diffuse astrocytomas by surgery and human fibroblast interferon without radiation therapy

Low-grade diffuse astrocytomas are slowly growing tumors with a relatively long overall survival. However, a substantial proportion undergoes dedifferentiation to a more malignant phenotype. Considerable controversy exists as to the best therapeutic management for patients with such tumors. Over the past decade, we have applied human fibroblast interferon (HFIF) therapy without radiation therapy to low-grade astrocytomas. We investigated 28 patients with WHO grade II astrocytomas of the cerebral hemispheres treated by surgery plus HFIF therapy. The overall response rate to the HFIF therapy was 36%. All side-effects of HFIF were transient, tolerable and manageable. The 5-year progression free survival and overall survival probabilities were 65% and 96%, respectively. Although our data from small cohort of patients may have modest value, our results suggest that HFIF may be useful in treating low-grade diffuse astrocytomas.

Estimulación cortical intraoperatoria en el tratamiento quirúrgico de los gliomas de bajo grado situados en áreas elocuentes

INTRODUCTION

Surgical selection of patients harboring low-grade gliomas based on radiological criteria may be insufficient due to individual variability in eloquent areas location and to the fact that function can be preserved within infiltrated brain tissue. Brain stimulation mapping safety for patients with low-grade gliomas is evaluated, analyzing whether this technique modifies the extent of resection and minimizes postoperative deficits.

MATERIAL AND METHODS

Twenty-five patients with lowgrade gliomas (II/IV WHO) located in eloquent areas underwent tumor resection with the aid of intraoperative mapping. Patients underwent surgery under local or general anesthesia depending on the neurological function to be explored. All procedures were performed from an oncological point of view, trying to achieve a radical tumor resection but stopping removal whenever functional tissue was found within or near the lesion.

RESULTS

Total or subtotal resection was achieved in 16 patients (64%); in five cases (20%) resection was partial, and in the remaining (16%) only a biopsy was obtained. Tumors located in the supplementary motor area (SMA) or in the operculum were those which could be more often totally resected. Thirteen patients (52%) experienced neurological worsening immediately after surgery but eight of them had almost completely recovered six months after the procedure.

CONCLUSIONS

Intraoperative functional mapping can optimize extent of resection minimizing permanent morbidity. Functional tissue can be found within the infiltrated brain and this must be considered in the presurgical planning. SMA and opercular tumors allow radical resection with low morbidity whereas insular tumors remain a challenge even with the aid of this technique.

Preoperative magnetic source imaging for brain tumor surgery: a quantitative comparison with intraoperative sensory and motor mapping

OBJECT

The aim of this study was to compare quantitatively the methods of preoperative magnetic source (MS) imaging and intraoperative electrophysiological cortical mapping (ECM) in the localization of sensorimotor cortex in patients with intraaxial brain tumors.

METHODS

Preoperative magnetoencephalography (MEG) was performed while patients received painless tactile somatosensory stimulation of the lip, hand, and foot. The early somatosensory evoked field was modeled using a single equivalent current dipole approach to estimate the spatial source of the response. Three-dimensional magnetic resonance image volume data sets with fiducials were coregistered with the MEG recordings to form the MS image. These individualized functional brain maps were integrated into a neuronavigation system. Intraoperative mapping of somatosensory and/or motor cortex was performed and sites were compared. In two subgroups of patients we compared intraoperative somatosensory and motor stimulation sites with MS imaging-based somatosensory localizations. Mediolateral projection of the MS imaging source localizations to the cortical surface reduced systematic intermodality discrepancies. The distance between two corresponding points determined using MS imaging and ECM was 12.5 +/- 1.3 mm for somatosensory-somatosensory and 19 +/- 1.3 mm for somatosensory-motor comparisons. The observed 6.5 mm increase in site separation was systematically demonstrated in the anteroposterior direction, as expected from actual anatomy. In fact, intraoperative sites at which stimulation evoked the same patient response exhibited a spatial variation of 10.7 +/- 0.7 mm.

CONCLUSIONS

Preoperative MS imaging and intraoperative ECM show a favorable degree of quantitative correlation. Thus, MS imaging can be considered a valuable and accurate planning adjunct in the treatment of patients with intraaxial brain tumors.

Intraoperative magnetic resonance imaging and magnetic resonance imaging-guided therapy for brain tumors

Since their introduction into surgical practice in the mid 1990s, intraoperative MRI systems have evolved into essential, routinely used tools for the surgical treatment of brain tumors in many centers. Clear delineation of the lesion, "under-the-surface" vision, and the possibility of obtaining real-time feedback on the extent of resection and the position of residual tumor tissue (which may change during surgery due to "brain-shift") are the main strengths of this method. High-performance computing has further extended the capabilities of intraoperative MRI systems, opening the way for using multimodal information and 3D anatomical reconstructions, which can be updated in "near real time." MRI sensitivity to thermal changes has also opened the way for innovative, minimally invasive (LASER ablations) as well as noninvasive therapeutic approaches for brain tumors (focused ultrasound). Although we have not used intraoperative MRI in clinical applications sufficiently long to assess long-term outcomes, this method clearly enhances the ability of the neurosurgeon to navigate the surgical field with greater accuracy, to avoid critical anatomic structures with greater efficacy, and to reduce the overall invasiveness of the surgery itself.

Intracranial navigation by using low-field intraoperative magnetic resonance imaging: preliminary experience

OBJECT

Intracranial navigation by using intraoperative magnetic resonance (iMR) imaging allows the surgeon to reassess anatomical relationships in near-real time during brain tumor surgery. The authors report their initial experience with a novel neuronavigation system coupled to a low-field iMR imaging system.

METHODS

Between October 2000 and December 2001, 70 neurosurgical procedures were performed using the mobile 0.12-tesla PoleStar N-10 iMR imaging system. The cases included 38 craniotomies, 15 brain biopsies, nine transsphenoidal approaches, and one drainage of a subdural hematoma. Tumor resection was performed using the awake method in seven of 38 cases. Of the craniotomies, image-confirmed complete or radical tumor resection was achieved in 28 cases, subtotal resection in eight cases, and open biopsies in two cases. Tumor resection was controlled with the use of image guidance until the final intraoperative images demonstrated that there was no residual tumor or that no critical brain tissue was at risk of compromise. In each stereotactic biopsy the location of the biopsy needle could be verified by intraoperative imaging and diagnostic tissue was obtained. Complications included a case of aseptic meningitis after a biopsy and one case of temporary intraoperative failure of the anesthesia machine. Awake craniotomies were performed successfully with no permanent neurological complications.

CONCLUSIONS

Intraoperative MR image-based neuronavigation is feasible when using the Odin PoleStar N-10 system for tumor resections that require multiple other surgical adjuncts including awake procedures, cortical mapping, monitoring of somatosensory evoked potentials, or electrocorticography. Use of the system for brain biopsies offers the opportunity of immediate verification of the needle tip location. Standard neurosurgical drills, microscopes, and other equipment can be used safely in conjunction with this iMR imaging system.

Chemotherapeutic dose intensification for treatment of malignant brain tumors: recent developments and future directions

Despite a large amount of research on malignant brain tumors over the past 70 years, the prognosis for most tumor types is poor. One current focus of research is increasing dose intensity of chemotherapeutic agents. Various ways to increase dose intensity include high-dose chemotherapy followed by stem cell rescue (eg, bone marrow transplant), blood-brain barrier disruption or use of RMP7 to increase transvascular drug delivery, local delivery of chemotherapeutic agents (convection enhancement or clysis, antibody conjugates, and biodegradable polymers), chemoprotective agents, and tumor sensitizers. Improved identification of patients likely to respond to a given regimen may also increase the effectiveness of chemotherapy. We also discuss approaches to improve the design of nonrandomized trials by identifying and controlling potential confounding variables. This will improve the quality of individual studies and perhaps the comparability across studies.