Repeated operations for infiltrative low-grade gliomas without intervening therapy

Second-look surgery in postoperative pediatric low-grade glioma

OBJECTIVE

To review the literature on second-look surgery in pediatric low-grade gliomas (LGG) with a view to presenting both sides of the picture of re-exploration.

METHODS

Collection of material from recent literature on pediatric LGG. This was a retrospective review of these publications.

RESULTS

There are a number of publications recommending second-look surgery in selected cases, provided morbidity of the second surgery is minimum, and indeed some in which there is improvement in the neurodeficit after the second resection.

CONCLUSION

There seems a fair balance of articles recommending and dissuading the practice of second-look surgery, but in our limited experience we have found it useful in selected patients.

Brain Plasticity Profiling as a Key Support to Therapeutic Decision-Making in Low-Grade Glioma Oncological Strategies

The ability of neural circuits to compensate for damage to the central nervous system is called postlesional plasticity. In diffuse low-grade gliomas (LGGs), a crosstalk between the brain and the tumor activates modulations of plasticity, as well as tumor proliferation and migration, by means of paracrine and electrical intercommunications. Such adaptative mechanisms have a major impact on the benefits and risks of oncological treatments but are still disregarded by current neuro-oncological guidelines. In this review, the authors first aimed to highlight clinical, radiological, and oncological markers that robustly reflect the plasticity potentials and limitations in LGG patients, including the location of the tumor and the degree of critical white matter tract infiltration, the velocity of tumor expansion, and the reactional changes of neuropsychological performances over time. Second, the interactions between the potential/limitations of cerebral plasticity and the efficacy/tolerance of treatment options (i.e., surgery, chemotherapy, and radiotherapy) are reviewed. Finally, a longitudinal and multimodal treatment approach accounting for the evolutive profiles of brain plasticity is proposed. Such an approach integrates personalized predictive models of plasticity potentials with a step-by-step therapeutic decision making and supports onco-functional balanced strategies in patients with LGG, with the ultimate aim of optimizing overall survival and quality of life.

Tumor volume and calcifications as indicators for preoperative differentiation of grade II/III diffuse gliomas

PURPOSE

To retrospectively evaluate preoperative clinical factors for their ability to preoperatively differentiate malignancy grades in patients with incipient supratentorial grade II/III diffuse gliomas.

METHODS

This retrospective study included 206 adult patients with incipient supratentorial grade II/III diffuse gliomas according to the 2016 World Health Organization classification of tumors of the central nervous system. The cohort included 136 men and 70 women, with a median age of 41 years. Preoperative factors included age, sex, presence of calcifications on computed tomography scans, and preoperative tumor volume measured using preoperative magnetic resonance imaging.

RESULTS

In patients with oligodendrogliomas (IDH-mutant and 1p/19q-codeleted), calcifications were significantly more frequent (p = 0.0034) and tumor volume was significantly larger (p < 0.001) in patients with grade III tumors than in those with grade II tumors. Moreover, in patients with IDH-mutant astrocytomas, preoperative tumor volume was significantly larger (p = 0.0042) in patients with grade III tumors than in those with grade II tumors. In contrast, none of the evaluated preoperative clinical factors were significantly different between the patients with grade II and III IDH-wildtype astrocytomas.

CONCLUSION

In adult patients with suspicison incipient supratentorial grade II/III diffuse gliomas, presence of calcifications and larger preoperative tumor volume might be used as preoperative indices to differentiate between malignancy grades II and III in oligodendrogliomas (IDH-mutant and 1p/19q-codeleted) and larger preoperative tumor volume might have similar utility in IDH-mutant astrocytomas.

Repeated Awake Surgical Resection(s) for Recurrent Diffuse Low-Grade Gliomas: Why, When, and How to Reoperate?

Early maximal surgical resection is the first treatment in diffuse low-grade glioma (DLGG), because the reduction of tumor volume delays malignant transformation and extends survival. Awake surgery with intraoperative mapping and behavioral monitoring enables to preserve quality of life (QoL). However, because of the infiltrative nature of DLGG, relapse is unavoidable, even after (supra)total resection. Therefore, besides chemotherapy and radiotherapy, the question of reoperation(s) is increasingly raised, especially because patients with DLGG usually enjoy a normal life with long-lasting projects. Here, the purpose is to review the literature in the emerging field of iterative surgeries in DLGG. First, long-term follow-up results showed that patients with DLGG who underwent multiple surgeries had an increased survival (above 17 years) with preservation of QoL. Second, the criteria guiding the decision to reoperate and defining the optimal timing are discussed, mainly based on the dynamic intercommunication between the glioma relapse (including its kinetics and pattern of regrowth) and the reactional cerebral reorganization—i.e., mechanisms underpinning reconfiguration within and across neural networks to enable functional compensation. Third, how to adapt medico-surgical strategy to this individual spatiotemporal brain tumor interplay is detailed, by considering the perpetual changes in connectome. These data support early reoperation in recurrent DLGG, before the onset of symptoms and before malignant transformation. Repeat awake resection(s) should be integrated in a global management including (neo)adjuvant medical treatments, to enhance long-lasting functional and oncological outcomes. The prediction of potential and limitation of neuroplasticity at each step of the disease must be improved to anticipate personalized multistage therapeutic attitudes.

Recurrent Low-Grade Gliomas: Does Reoperation Affect Neurocognitive Functioning?

BACKGROUND

Reoperations in patients with recurrent low-grade gliomas (RLGG) were proposed to control tumor residual and delay the risk of malignant transformation over time.

OBJECTIVE

To investigate neurocognitive outcomes in patients with RLGG who underwent a second surgery with awake monitoring.

METHODS

In this retrospective study, patients who underwent a second awake surgery for RLGG were included. Patients had presurgical and 3-mo postsurgical neuropsychological assessments. Data were converted into Z-scores and combined by the cognitive domain. Number of patients with cognitive deficits (Z-score <-1.65), variations of Z-scores, and extent of resection (EOR) were analyzed.

RESULTS

Sixty-two patients were included (mean age: 41.2 ± 10.0 yr). None had permanent neurological deficits postoperatively. Eight patients (12.9%) had a cognitive deficit preoperatively. Four additional patients (6.5%) had a cognitive deficit 3 mo after reoperation. Among other patients, 13 (21.0%) had a mild decline without cognitive deficits while 29 (46.8%) had no change of their performances and 8 (12.9%) improved. Overall, 94.2% of the patients returned to work. There were no correlations between EOR and Z-scores. Total/subtotal resections were achieved in 91.9% of the patients (mean residual: 3.1 cm3). Fifty-eight patients (93.5%) were still alive after an overall follow-up of 8.3 yr.

CONCLUSION

Reoperation with awake monitoring in patients with RLGG was compatible with an early recovery of neuropsychological abilities. Four patients (6.5%) presented a new cognitive deficit at 3 mo postoperatively. Total/subtotal resections were achieved in most patients. Based on these favorable outcomes, reoperation should be considered in a more systematic way.

Extending the multistage surgical strategy for recurrent initially low-grade gliomas: functional and oncological outcomes in 31 consecutive patients who underwent a third resection under awake mapping

OBJECTIVE

Maximal safe resection is the first treatment in diffuse low-grade glioma (DLGG). Due to frequent tumor recurrence, a second surgery has already been reported, with favorable results. This study assesses the feasibility and functional and oncological outcomes of a third surgery in recurrent DLGG.

METHODS

Patients with DLGG who underwent a third functional-based resection using awake mapping were consecutively selected. They were classified into group 1 in cases of slow tumor regrowth or group 2 if a radiological enhancement occurred during follow-up. All data regarding clinicoradiological features, histomolecular results, oncological treatment, and survival were collected.

RESULTS

Thirty-one patients were included, with a median age of 32 years. There were 20 astrocytomas and 11 oligodendrogliomas in these patients. Twenty-one patients had medical oncological treatment before the third surgery, consisting of chemotherapy in 19 cases and radiotherapy in 8 cases. No neurological deficit persisted after the third resection except mild missing words in 1 patient, with 84.6% of the patients returning to work. The median follow-up duration was 13.1 ± 3.4 years since diagnosis, and 3.1 ± 2.9 years since the third surgery. The survival rates at 7 and 10 years were 100% and 89.7%, respectively, with an estimated median overall survival of 17.8 years since diagnosis. A comparison between the groups showed that the Karnofsky Performance Scale score dropped below 80 earlier in group 2 (14.3 vs 17.1 years, p = 0.01). Median residual tumor volume at the third surgery was smaller (2.8 vs 14.4 cm3, p = 0.003) with a greater extent of resection (89% vs 70%, p = 0.003) in group 1.

CONCLUSIONS

This is the first consecutive series showing evidence that, in select patients with progressive DLGG, a third functional-based surgery can be achieved using awake mapping with low neurological risk and a high rate of total resection, especially when reoperation is performed before malignant transformation.

Subtraction Maps Derived from Longitudinal Magnetic Resonance Imaging in Patients with Glioma Facilitate Early Detection of Tumor Progression

Progression of glioma is frequently characterized by increases or enhanced spread of a hyperintensity in fluid attenuated inversion recovery (FLAIR) sequences. However, changes in FLAIR signal over time can be subtle, and conventional (CONV) visual reading is time-consuming. The purpose of this monocentric, retrospective study was to compare CONV reading to reading of subtraction maps (SMs) for serial FLAIR imaging. FLAIR datasets of cranial 3-Tesla magnetic resonance imaging (MRI), acquired at two different time points (mean inter-scan interval: 5.4 ± 1.9 months), were considered per patient in a consecutive series of 100 patients (mean age: 49.0 ± 13.7 years) diagnosed with glioma (19 glioma World Health Organization [WHO] grade I and II, 81 glioma WHO grade III and IV). Two readers (R1 and R2) performed CONV and SM reading by assessing overall image quality and artifacts, alterations in tumor-associated FLAIR signal over time (stable/unchanged or progressive) including diagnostic confidence (1-very high to 5-very low diagnostic confidence), and time needed for reading. Gold-standard (GS) reading, including all available clinical and imaging information, was performed by a senior reader, revealing progressive FLAIR signal in 61 patients (tumor progression or recurrence in 38 patients, pseudoprogression in 10 patients, and unclear in the remaining 13 patients). SM reading used an officially certified and commercially available algorithm performing semi-automatic coregistration, intensity normalization, and color-coding to generate individual SMs. The approach of SM reading revealed FLAIR signal increases in a larger proportion of patients according to evaluations of both readers (R1: 61 patients/R2: 60 patients identified with FLAIR signal increase vs. R1: 45 patients/R2: 44 patients for CONV reading) with significantly higher diagnostic confidence (R1: 1.29 ± 0.48, R2: 1.26 ± 0.44 vs. R1: 1.73 ± 0.80, R2: 1.82 ± 0.85; p < 0.0001). This resulted in increased sensitivity (99.9% vs. 73.3%) with maintained high specificity (98.1% vs. 98.8%) for SM reading when compared to CONV reading. Furthermore, the time needed for SM reading was significantly lower compared to CONV assessments (p < 0.0001). In conclusion, SM reading may improve diagnostic accuracy and sensitivity while reducing reading time, thus potentially enabling earlier detection of disease progression.

The effect of operations in patients with recurrent diffuse low-grade glioma: A qualitative systematic review

The role of operation for patients with recurrent diffuse low-grade glioma (DLGG) is controversial. A few studies compared the effectiveness between surgery and other treatments for those patients. We did a systematic review for the effects of reoperation for recurrent DLGG. We searched the following databases from 1990 to 2018: Medline, Cochrane Library, Scopus and Opengrey, including researches about reoperation for recurrent DLGG, regardless of comparison and study design. The Newcastle-Ottawa scale (NOS) was used for quality assessment. Ten studies with 358 participants met the criteria. Due to lack of survival data about non-operated group, we failed to analyze the effect of reoperation. The risk bias of included studies was acceptable except the comparability. However, we found 48.4 % (155/320) of patients underwent gross resection and the safety was acceptable. About 1/3 received adjuvant therapy and 41.9 % (125/298) got histologically progressed. In a word, few studies reported the survival data of recurrent DLGG patients received reoperation. Most were young adults and half of them experienced a histological progress. But there are still a lot of shortages of the existing studies and more researches on the reoperation efficacy in recurrent DLGG are needed.

Cognitive Functions in Repeated Glioma Surgery

Low-grade gliomas (LGG) are slow-growing brain tumors infiltrating the central nervous system which tend to recur, often with malignant degeneration after primary treatment. Re-operations are not always recommended due to an assumed higher risk of neurological and cognitive deficits. However, this assumption is relatively ungrounded due to a lack of extensive neuropsychological testing. We retrospectively examined a series of 40 patients with recurrent glioma in eloquent areas of the left hemisphere, who all completed comprehensive pre- (T3) and post-surgical (T4) neuropsychological assessments after a second surgery (4-month follow up). The lesions were most frequent in the left insular cortex and the inferior frontal gyrus. Among this series, in 17 patients the cognitive outcomes were compared before the first surgery (T1), 4 months after the first surgery (T2), and at T3 and T4. There was no significant difference either in the number of patients scoring within the normal range between T3 and T4, or in their level of performance. Further addressing the T1-T4 evolution, there was no significant difference in the number of patients scoring within the normal range. As to their level of performance, the only significant change was in phonological fluency. This longitudinal follow-up study showed that repeated glioma surgery is possible without major damage to cognitive functions in the short-term period (4 months) after surgery.

Application of an Artificial Intelligence Algorithm to Prognostically Stratify Grade II Gliomas

(1) Background: Recently, it has been shown that the extent of resection (EOR) and molecular classification of low-grade gliomas (LGGs) are endowed with prognostic significance. However, a prognostic stratification of patients able to give specific weight to the single parameters able to predict prognosis is still missing. Here, we adopt classic statistics and an artificial intelligence algorithm to define a multiparametric prognostic stratification of grade II glioma patients. (2) Methods: 241 adults who underwent surgery for a supratentorial LGG were included. Clinical, neuroradiological, surgical, histopathological and molecular data were assessed for their ability to predict overall survival (OS), progression-free survival (PFS), and malignant progression-free survival (MPFS). Finally, a decision-tree algorithm was employed to stratify patients. (3) Results: Classic statistics confirmed EOR, pre-operative- and post-operative tumor volumes, Ki67, and the molecular classification as independent predictors of OS, PFS, and MPFS. The decision tree approach provided an algorithm capable of identifying prognostic factors and defining both the cut-off levels and the hierarchy to be used in order to delineate specific prognostic classes with high positive predictive value. Key results were the superior role of EOR on that of molecular class, the importance of second surgery, and the role of different prognostic factors within the three molecular classes. (4) Conclusions: This study proposes a stratification of LGG patients based on the different combinations of clinical, molecular, and imaging data, adopting a supervised non-parametric learning method. If validated in independent case studies, the clinical utility of this innovative stratification approach might be proved.

Observation after surgery for low grade glioma: long-term outcome in the light of the 2016 WHO classification

PURPOSE

To provide detailed long-term data after initial observation for patients after histological confirmation of low grade (WHO II) gliomas according to molecular stratification.

METHODS

A series of 110 patients with watchful waiting strategy after initial surgery for LGG and re-surgery at tumor progression were analyzed. Progression-free survival, time to malignant transformation, post-recurrence survival, and overall survival were estimated with the Kaplan-Meier method. Prognostic factors were identified by the Log Rank test and Cox multivariate proportional hazards model.

RESULTS

The cohort comprised 18 IDH wild type (IDH^wt) and 53 IDH mutated (IDH^mut) astrocytomas, and 39 IDH mutated and 1p 19q co-deleted (IDH^mut/codel) patients. The median follow-up was 126 (95% CI 109-143) months. Surgery was gross total resection in 58, subtotal resection in 28, and biopsy in 24 patients. Progression-free survival rates at 5, 10 and 15 years was 38% 18% and 1%. The corresponding malignant transformation rates were 17%, 39% and 71%. The initial extent of resection influenced progression-free survival, time to malignant transformation and overall survival. Molecular subtype IDH^mut/codel was the strongest prognostic factor for overall survival and for time to malignant transformation.

CONCLUSION

The strongest determinant of the patients' course after initial watchful waiting was the molecular tumor status. Extensive resection may increase time to progression and malignant transformation. Observation may be justified in selected patients.

Management of supratentorial recurrent low-grade glioma: A multidisciplinary experience in 35 adult patients

The management of recurrent diffuse low-grade gliomas (LGGs) is controversial. In the present study, the multidisciplinary management of 35 patients with recurrent LGGs was retrospectively analyzed. Tumor progression or recurrence was defined by clinical, radiological and/or metabolic pejorative evolution. All patients were regularly followed up by a multidisciplinary neuro-oncological group at Hôpital Erasme. Patients with histologically confirmed supratentorial LGGs (7 astrocytoma, 22 oligodendrogliomas and 6 oligoastrocytomas) who had undergone surgery between August 2004 and November 2010 were included. A total of 3 patients exhibited no tumor progression (median follow-up (FU), 81 months; range, 68-108 months). Tumor recurrence occurred in the 32 remaining patients [progression-free survival (PFS), 26 months; range, 2-104 months]. In addition, 25/29 (86%) patients who received surgery alone underwent reoperation at the time of tumor recurrence, and high-grade transformation occurred in 6 of these patients (24%). Furthermore, 4/29 (14%) patients were treated with adjuvant therapy alone (3 chemotherapy and 1 radiotherapy). In the 19 patients with no high-grade transformation at reintervention, 3 received adjuvant therapy and 16 were regularly followed up through multimodal imaging. The PFS time of the patients who underwent reoperation with close FU (n=16) and for the patients receiving adjuvant therapy with or without surgery (n=7) at first recurrence was 10 and 24 months (P=0.005), respectively. However, no significant difference was observed for overall survival (P=0.403). At the time of this study, 22 of the 35 patients included were alive following a median FU time of 109 months (range, 55-136). The results of the present study could change the multidisciplinary approach used into a more aggressive approach with adjuvant therapy, with or without surgery, for the treatment of a select subpopulation of patients with LGGs at the first instance of tumor recurrence.

Identifying clinical risk in low grade gliomas and appropriate treatment strategies, with special emphasis on the role of surgery

INTRODUCTION

Diffuse low-grade glioma (DLGG) is a chronic tumoral disease that ineluctably grows, migrates along white matter pathways, and progresses to a higher grade of malignancy. Areas covered: To determine the best individualized treatment attitude for each DLGG patient, and to redefine it over the years, i.e. to optimize the 'onco-functional balance' of serial and multimodal therapies, the understanding of the natural history of this chronic disease is crucial but not sufficient. A paradigmatic shift is to tailor the individual management according to the dynamic relationships between DLGG course and neural remodeling. In this spirit, a better knowledge of brain plasticity in a connectomal account of cerebral processing has enabled a dramatic improvement of both oncological and functional outcomes in DLGG patients, by increasing overall survival while preserving (or even improving) the quality of life. Expert commentary: Here, we propose an individualized and recursive therapeutic strategy in DLGG, leading to the concept of a 'personalized functional neuro-oncology', by emphasizing the role of early and maximal safe surgical resection(s) reliably achieved using intraoperative mapping of cortico-subcortical networks in awake patients.

Management of patients with recurrence of diffuse low grade glioma: A systematic review and evidence-based clinical practice guideline

TARGET POPULATION

These recommendations apply to adult patients with recurrent low-grade glioma (LGG) with initial pathologic diagnosis of a WHO grade II infiltrative glioma (oligodendroglioma, astrocytoma, or oligo-astrocytoma).

PATHOLOGY AT RECURRENCE

QUESTION

Do pathologic and molecular characteristics predict outcome/malignant transformation at recurrence?

RECOMMENDATIONS

IDH STATUS AND RECURRENCE: (Level III) IDH mutation status should be determined as LGGs with IDH mutations have a shortened time to recurrence. It is unclear whether knowledge of IDH mutation status provides benefit in predicting time to progression or overall survival. TP53 STATUS AND RECURRENCE: (Level III) TP53 mutations occur early in LGG pathogenesis, remain stable, and are not recommended as a marker of predisposition to malignant transformation at recurrence or other measures of prognosis. MGMT STATUS AND RECURRENCE: (Level III) Assessment of MGMT status is recommended as an adjunct to assessing prognosis as LGGs with MGMT promoter methylation are associated with shorter PFS (in the absence of TMZ) and longer post-recurrence survival (in the presence of TMZ), ultimately producing similar overall survival to LGGs without MGMT methylation. The available retrospective reports are conflicting and comparisons between reports are limited CDK2NA STATUS AND RECURRENCE: (Level III) Assessment of CDK2NA status is recommended when possible as the loss of expression of the CDK2NA via either methylation or loss of chromosome 9p is associated with malignant progression of LGGs. PROLIFERATIVE INDEX AND RECURRENCE: (Level III) It is recommended that proliferative indices (MIB-1 or BUdR) be measured in LGGs as higher proliferation indices are associated with increased likelihood of recurrence and shorter progression free and overall survival. 1P/19Q STATUS AND RECURRENCE: There is insufficient evidence to make any recommendations.

CHEMOTHERAPY AT RECURRENCE

QUESTION

What role does chemotherapy have in LGG recurrence?

RECOMMENDATIONS

TEMOZOLOMIDE AND RECURRENCE: (Level III) Temozolomide is recommended in the therapy of recurrent LGG as it may improve clinical symptoms. Oligodendrogliomas and tumors with 1p/19q co-deletion may derive the most benefit. PCV AND RECURRENCE: (Level III) PCV is recommended in the therapy of LGG at recurrence as it may improve clinical symptoms with the strongest evidence being for oligodendrogliomas. CARBOPLATIN AND RECURRENCE : (Level III) Carboplatin is not recommended as there is no significant benefit from carboplatin as single agent therapy for recurrent LGGs. OTHER TREATMENTS (NITROSUREAS, HYDROXYUREA/IMANITIB, IRINOTECAN, PACLITAXEL) AND RECURRENCE: There is insufficient evidence to make any recommendations. It is recommended that individuals with recurrent LGGs be enrolled in a properly designed clinical trial to assess these chemotherapeutic agents.

RADIATION AT RECURRENCE

QUESTION

What role does radiation have in LGG recurrence?

RECOMMENDATIONS

RADIATION AT RECURRENCE WITH NO PREVIOUS IRRADIATION: (Level III) Radiation is recommended at recurrence if there was no previous radiation treatment. RE-IRRADIATION AT RECURRENCE: (Level III) It is recommended that re-irradiation be considered in the setting of LGG recurrence as it may provide benefit in disease control.

SURGERY AT RECURRENCE

There is insufficient evidence to make any specific recommendations. It is recommended that individuals with recurrent LGGs be enrolled in a properly designed clinical trial to assess the role of surgery at recurrence.

Second Surgery in Insular Low-Grade Gliomas

Background. Given the technical difficulties, a limited number of works have been published on insular gliomas surgery and risk factors for tumor recurrence (TR) are poorly documented. Objective. The aim of the study was to determine TR in adult patients with initial diagnosis of insular Low-Grade Gliomas (LGGs) that subsequently underwent second surgery. Methods. A consecutive series of 53 patients with insular LGGs was retrospectively reviewed; 23 patients had two operations for TR. Results. At the time of second surgery, almost half of the patients had experienced progression into high-grade gliomas (HGGs). Univariate analysis showed that TR is influenced by the following: extent of resection (EOR) (P < 0.002), ΔVT2T1 value (P < 0.001), histological diagnosis of oligodendroglioma (P = 0.017), and mutation of IDH1 (P = 0.022). The multivariate analysis showed that EOR at first surgery was the independent predictor for TR (P < 0.001). Conclusions. In patients with insular LGG the EOR at first surgery represents the major predictive factor for TR. At time of TR, more than 50% of cases had progressed in HGG, raising the question of the oncological management after the first surgery.

New concepts in the management of diffuse low-grade glioma: Proposal of a multistage and individualized therapeutic approach

Diffuse low-grade glioma grows, migrates along white matter tracts, and progresses to high-grade glioma. Rather than a "wait and see" policy, an aggressive attitude is now recommended, with early surgery as the first therapy. Intraoperative mapping, with maximal resection according to functional boundaries, is associated with a longer overall survival (OS) while minimizing morbidity. However, most studies have investigated the role of only one specific treatment (surgery, radiotherapy, chemotherapy) without taking a global view of managing the cumulative time while preserving quality of life (QoL) versus time to anaplastic transformation. Our aim is to switch towards a more holistic concept based upon the anticipation of a personalized and long-term multistage therapeutic approach, with online adaptation of the strategy over the years using feedback from clinical, radiological, and histomolecular monitoring. This dynamic strategy challenges the traditional approach by proposing earlier therapy, by repeating treatments, and by reversing the classical order of therapies (eg, neoadjuvant chemotherapy when maximal resection is impossible, no early radiotherapy) to improve OS and QoL. New individualized management strategies should deal with the interactions between the course of this chronic disease, reaction brain remapping, and oncofunctional modulation elicited by serial treatments. This philosophy supports a personalized, functional, and preventive neuro-oncology.

Intraoperative monitoring of an aspect of executive functions: administration of the Stroop test in 9 adult patients during awake surgery for resection of frontal glioma

BACKGROUND

Awake brain surgery allows extensive intraoperative monitoring of not only motor and sensory functions and language but also executive functions.

OBJECTIVE

To administer the Stroop test intraoperatively to avoid dramatic side effects such as akinetic mutism and to monitor executive functions in an attempt to optimize the benefit/risk balance of surgery.

METHODS

A series of 9 adult patients with frontal glioma were operated on for gross tumor resection under local anesthesia. All procedures involved the anterior cingulate cortex (ACC).

RESULTS

Three types of response to the Stroop test were observed: 3 patients had a Stroop effect only for stimulation of the contralateral ACC; 3 patients had a Stroop effect for stimulation of the ipsilateral ACC; and 3 patients had no Stroop effect. Preoperative and postoperative neuropsychological and surgical results are presented and discussed. Stimulation sites eliciting a Stroop effect are compared with published image-based data, and insight provided by these surgical data regarding ACC function and plasticity is discussed. No operative complication related to intraoperative administration of the Stroop test was observed.

CONCLUSION

Administration of the Stroop test during resection of gliomas involving the ACC in adult patients is an option for intraoperative monitoring of executive functions during awake surgery. Globally, these results suggest functional compensation, mediated by plasticity mechanisms, by contralateral homologous regions of the ACC in adult patients with frontal glioma.

Reoperations of patients with low-grade gliomas in eloquent or near eloquent brain areas

BACKGROUND AND PURPOSE

Reoperations of patients with recurrent low-grade gliomas (LGG) are not always recommended due to a higher risk of neurological deficits when compared to initial surgery. The purpose of the present study was to evaluate surgical outcomes of patients operated on for recurrent LGG.

MATERIAL AND METHODS

Sixteen patients who had surgery for recurrent LGG out of 68 LGG patients who underwent surgery at the Department of Neurosurgery in Sosnowiec, Poland between 2005 and 2011 were enrolled in the study.

RESULTS

A large tumour volume prior to the initial surgery was the most significant parameter influencing LGG progression (96.6 cm³ vs. 47.9 cm3, p = 0.01). Increased incidence of epileptic seizures and decreased mental ability according to Karnofsky score were the most common symptoms associated with tumour recurrence. In the group of patients with malignant transformation, the relative cerebral blood volume (rCBV) was considerably increased (1.21 vs. 2.41, p < 0.01). No statistically significant difference was found in terms of the extent of resection between initial surgery and reoperation. Similarly, no significant difference was found in the number of patients with a permanent neurological deficit after initial surgery and reoperation.

CONCLUSIONS

Reoperations of the patients with recurrent LGG are not burdened with a higher risk of neurological sequelae when compared to initial surgery. The extent of resection during the surgery for LGG recurrence is comparable to initial surgery. The increase of rCBV seems to be a significant biomarker that indicates malignant transformation.

Malignant transformation in pediatric spinal intramedullary tumors: case-based update

BACKGROUND

In children, intramedullary spinal cord neoplasms are rare. These are typically low-grade neuroepithelial tumors, most commonly astrocytomas, ependymomas, and gangliogliomas. Malignant transformation, while common in recurrent adult low-grade gliomas, is an unusual event in pediatric low-grade neoplasms, specifically in intramedullary spinal cord tumors.

ILLUSTRATIVE CASES

We report two cases of malignant transformation in low-grade neuroepithelial tumors of the pediatric intramedullary spinal cord. Two children with intramedullary tumors, one with a WHO grade I ganglioglioma and one with a low-grade astrocytoma, were treated surgically, diagnosed histologically, and followed through the course of their disease. Both patients' tumors transformed to higher grades without prior irradiation or chemotherapy, and without a genetic predisposition to tumorigenesis.

DISCUSSION

Malignant transformation can occur in low-grade intramedullary neoplasms in children. This is a novel documented event for pediatric intramedullary spinal cord tumors and a rare event for all pediatric low-grade neuroepithelial tumors without induction by irradiation. A survey of the relevant literature reveals an underwhelming number of studies focusing on malignant transformation in children's CNS tumors relative to adults. Further investigation into molecular mechanisms of pediatric low-grade neoplasms may reveal more aggressive tumor sub-variants predisposed to malignant degeneration.

Awake Mapping Optimizes the Extent of Resection for Low-Grade Gliomas in Eloquent Areas

BACKGROUND

Awake craniotomy with intraoperative electrical mapping is a reliable method to minimize the risk of permanent deficit during surgery for low-grade glioma located within eloquent areas classically considered inoperable. However, it could be argued that preservation of functional sites might lead to a lesser degree of tumor removal. To the best of our knowledge, the extent of resection has never been directly compared between traditional and awake procedures.

OBJECTIVE

We report for the first time a series of patients who underwent 2 consecutive surgeries without and with awake mapping.

METHODS

Nine patients underwent surgery for a low-grade glioma in functional sites under general anesthesia in other institutions. The resection was subtotal in 3 cases and partial in 6 cases. There was a postoperative worsening in 3 cases. We performed a second surgery in the awake condition with intraoperative electrostimulation. The resection was performed according to functional boundaries at both the cortical and subcortical levels.

RESULTS

Postoperative magnetic resonance imaging showed that the resection was complete in 5 cases and subtotal in 4 cases (no partial removal) and that it was improved in all cases compared with the first surgery (P = .04). There was no permanent neurological worsening. Three patients improved compared with the presurgical status. All patients returned to normal professional and social lives.

CONCLUSION

Our results demonstrate that awake surgery, known to preserve the quality of life in patients with low-grade glioma, is also able to significantly improve the extent of resection for lesions located in functional regions.

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.

Re-operation is a safe and effective therapeutic strategy in recurrent WHO grade II gliomas within eloquent areas

BACKGROUND

To analyze the functional and oncological results after re-operation for recurrent WHO grade II Glioma located in eloquent regions.

METHOD

We reviewed a consecutive series of 19 patients with GIIG within functional areas who underwent two operations separated by at least 1 year. Intraoperative electrical stimulation mapping was used in all operations for recurrence and in 14 of the initial procedures. A specific rehabilitation was provided.

FINDINGS

At the first operation, we performed 14 subtotal and 5 partial resections. Eighteen patients returned to a normal socio-professional life. Nine patients received adjuvant treatment. At the second operation, we performed 1 total, 13 subtotal and 5 partial resections. Three patients with a preoperative neurological deficit improved, 13 remained unchanged, and 3 slight new deficits appeared. In 14 of the 17 patients with preoperative chronic epilepsy, the seizures were reduced or disappeared. Sixteen patients returned to a normal socio-professional life. Pathohistological examination showed that 11 tumours had progressed to high-grade glioma. The median time between the two operations was 4.1 years (range 1 to 7.8 years) and the median follow-up from initial diagnosis was 6.6 years (range 2.3 to 14.3 years). No deaths occurred during the follow-up period.

CONCLUSIONS

Repeat operations guided by intra-operative electrical stimulation is an efficacious treatment for recurrent grade II glioma in an eloquent area.

Tumor recurrence and malignant progression of gangliogliomas

BACKGROUND

Most gangliogliomas (GGs) are benign tumors, but tumor recurrence and malignant progression are observed in some patients.

METHODS

The authors analyzed their experience with 4 recurrent/progressive GGs (World Health Organization [WHO] grade I), 21 tumors with atypical features (WHO grade II), and 5 tumors with anaplastic histologic features (WHO grade III). Histopathologic findings (23 patients) were reviewed. The mean follow-up was 5.9 years (median, 4.5 years; range, 0.5-14.7 years).

RESULTS

The 5-year survival rates were only 79% for patients who had tumors with atypical features and 53% for patients who had WHO grade III tumors. Secondary glioblastomas were diagnosed in 5 of 11 patients (45%) who underwent surgery for tumor recurrence. Age at surgery <40 years (P = .007) was associated significantly with better overall survival (OS), but it was not associated with better progression-free survival (PFS). Clinical presentation (drug-resistant epilepsy vs all other patients with seizures vs no seizures) was associated significantly with better OS (P = .005) and PFS (P < .001). Patients who had extratemporal tumors had a significantly shorter PFS (P = .01) but not OS. A complete resection was correlated strongly with both OS (P = .002) and PFS (P = .001). Neuropathologic examination revealed the presence of a gemistocytic cell component (PFS, P = .025), a lack of protein droplets (OS, P = .04; PFS, P = .05), and focal tumor cell-associated CD34 immunolabeling (OS, P = .03) as significant predictors of an adverse clinical course.

CONCLUSIONS

The current data supported a 3-tiered GG histopathologic grading system that included an intermediate diagnostic category (atypical GG, WHO grade II). Careful attention to histopathologic findings and clinical parameters usually will identify patients who are at risk for an adverse clinical course.

Surgical management of intracranial gliomas

Surgery is indicated in almost all glioma patients at some point during the course of their disease. The surgical intervention aims at obtaining a tissue diagnosis, providing symptom relief, improving patient survival by reducing the tumor burden, and in rare cases even effecting a cure.A resection will reduce symptoms related to the mass effect of the tumor, and offers a good chance for seizure control. An increasing body of data suggests that glioma patients will benefit from a maximal safe surgical cytoreduction. However, the size of the effect may vary for the different glioma entities. Modern adjuvant neuro-oncological treatment strategies rely heavily on the histological diagnosis. A (stereotactic) biopsy should therefore be offered to patients with nonresectable gliomas to allow for histology-guided adjuvant therapy. Some gliomas can be managed successfully with stereotactic interstitial radiosurgery (brachytherapy). Intra- and extraoperative electrophysiological mapping and/or monitoring, functional MRI, intraoperative imaging, and neuronavigation are increasingly used in many neurosurgical centers in order to reduce surgical morbidity. A definite effect on long-term outcome needs yet to be proven.Advances in computers, imaging, and other technologies will continue to play a large role in the evolution of neurosurgical treatment for gliomas. This may well lead to further centralization of care. There will be an increasing pressure on neurosurgeons to justify the costs involved by showing that patients will actually benefit from complex treatments in highly specialized centers.

Evolutionary game theory elucidates the role of glycolysis in glioma progression and invasion

OBJECTIVES

Tumour progression has been described as a sequence of traits or phenotypes that cells have to acquire if the neoplasm is to become an invasive and malignant cancer. Although genetic mutations that lead to these phenotypes are random, the process by which some of these mutations become successful and cells spread is influenced by tumour microenvironment and the presence of other cell phenotypes. It is thus likely that some phenotypes that are essential in tumour progression will emerge in the tumour population only with prior presence of other different phenotypes.

MATERIALS AND METHODS

In this study, we use evolutionary game theory to analyse the interactions between three different tumour cell phenotypes defined by autonomous growth, anaerobic glycolysis, and cancer cell invasion. The model allows us to understand certain specific aspects of glioma progression such as the emergence of diffuse tumour cell invasion in low-grade tumours.

RESULTS

We have found that the invasive phenotype is more likely to evolve after appearance of the glycolytic phenotype which would explain the ubiquitous presence of invasive growth in malignant tumours.

CONCLUSIONS

The result suggests that therapies, which increase the fitness cost of switching to anaerobic glycolysis, might decrease probability of the emergence of more invasive phenotypes.

Recurrence following neurosurgeon-determined gross-total resection of adult supratentorial low-grade glioma: results of a prospective clinical trial

OBJECT

In 1998, the Radiation Therapy Oncology Group initiated a Phase II study of observation for adults < 40 years old with cerebral low-grade glioma who underwent a neurosurgeon-determined gross-total resection (GTR).

METHODS

Patient eligibility criteria included the presence of a World Health Organization Grade II astrocytoma, oligodendroglioma, or mixed oligoastrocytoma confirmed histologically; age 18-39 years; Karnofsky Performance Scale score > or = 60; Neurologic Function Scale score < or = 3; supratentorial tumor location; neurosurgeon-determined GTR; and pre- and postoperative MR imaging with contrast enhancement available for central review by the principal investigator. Patients were observed following GTR and underwent MR imaging every 6 months. Prognostic factors analyzed for their contribution to patient overall survival, progression-free survival (PFS), and tumor recurrence included age, sex, Karnofsky Performance Scale score, Neurologic Function Scale score, histological type, contrast enhancement on preoperative MR imaging, preoperative tumor diameter, residual disease based on postoperative MR imaging, and baseline Mini-Mental State Examination score.

RESULTS

Between 1998 and 2002, 111 eligible patients were entered into the study. In these 111 patients, the overall survival rates at 2 and 5 years were 99 and 93%, respectively. The PFS rates in these 111 patients at 2 and 5 years were 82 and 48%, respectively. Three prognostic factors predicted significantly poorer PFS in univariate and multivariate analyses: 1) preoperative tumor diameter > or = 4 cm; 2) astrocytoma/oligoastrocytoma histological type; and 3) residual tumor > or = 1 cm according to MR imaging. Review of the postoperative MR imaging results revealed that 59% of patients had < 1 cm residual disease (with a subsequent 26% recurrence rate), 32% had 1-2 cm residual disease (with a subsequent 68% recurrence rate), and 9% had > 2 cm residual disease (with a subsequent 89% recurrence rate).

CONCLUSIONS

These data suggest that young adult patients with low-grade glioma who undergo a neurosurgeon-determined GTR have a > 50% risk of tumor progression 5-years postoperatively, warranting close follow-up and consideration for adjuvant treatment.

Long-term brain plasticity allowing a multistage surgical approach to World Health Organization Grade II gliomas in eloquent areas

Although the goal of surgery for World Health Organization Grade II gliomas is maximal extent of resection, complete tumor removal is not always possible when the glioma involves eloquent areas. The authors propose a multistage surgical approach to highly crucial areas that are classically considered inoperable, enabling optimization of the extent of resection while avoiding permanent cognitive deficits due to induced functional reshaping in the interim between the 2 consecutive operations. To demonstrate such plasticity, the authors used a combination of sequential functional MR imaging and intraoperative electrical stimulation mapping before and during surgeries spaced by several years in 2 patients who each underwent 2 separate resections of Grade II gliomas located in the left dominant premotor area. During several years of follow-up after the first procedure, both patients had unremarkable examination results and normal socioprofessional lives. There was no malignant transformation. Based on their experience with these cases, the authors suggest that in cases of incomplete glioma removal, a second operation before anaplasia should be considered, made possible by brain reorganization after the first operation.

Resection of World Health Organization Grade II gliomas involving Broca's area: methodological and functional considerations

OBJECTIVE

Advances in functional mapping have enabled us to extend the indications of surgery for low-grade gliomas (LGGs) within eloquent regions. However, to our knowledge, no study has been specifically dedicated to the resection of LGGs within Broca's area. We report the first surgical series of LGGs involving this area by focusing on methodological and functional considerations.

METHODS

Seven patients harboring an LGG in Broca's area (revealed by partial seizures) had a language functional magnetic resonance imaging scan and then underwent operation while awake using intrasurgical electrical mapping.

RESULTS

The neurological examination was normal in all patients despite mild language disturbances shown using the Boston Diagnosis Aphasia Examination. Both pre- and intraoperative cortical mapping found language reorganization with recruitment of the ventral and dorsal premotor cortices, orbitofrontal cortex, and insula, whereas no or few language sites were detected within Broca's area. Subcortically, electrostimulation allowed the identification and preservation of four structures still functional, including the arcuate fasciculus, fronto-occipital fasciculus, fibers from the ventral premotor cortex, and head of the caudate. Postoperatively, after transient language worsening, all patients recovered and returned to a normal socioprofessional life. The resection was total in three cases, subtotal in three, and partial in one patient (operated twice).

CONCLUSION

Our results indicate that, in patients with no aphasia despite LGGs within Broca's area, thanks to brain plasticity, the tumor can be removed while involving this "unresectable" structure without inducing sequelae and even improving the quality of life when intractable epilepsy is relieved on the condition that subcortical language connectivity is preserved.

Factors related to surgical complications and their impact on the functional status in 236 open surgeries for malignant tumors in a Latino-American hospital

BACKGROUND

There are not many studies that address the selection of patients harboring malignant brain tumors for open surgery. It is necessary, especially in developing countries, to establish the standards because of their impact not only on the efficacy but also on the cost-effectiveness of surgery. With the concern to add information that may help in future studies about the decision making, we proposed to analyze factors associated with surgical complications and evaluate their influence on the functional status at 30 days after surgery.

METHODS

A consecutive series of 236 surgeries performed between June 1999 and June 2005 were retrospectively analyzed (168 gliomas, 65 metastases, 3 others). Variables evaluated were age, sex, pre- and postoperative KPS, ASA status, anatomic localization, extent of tumor resection, tumor histology, and number of surgeries.

RESULTS

The incidence of complicated craniotomies was 15.68% and mortality was 2.97%. Postoperatively, 92% of the patients improved or maintained the functional status, whereas 8% worsened. In multivariate analysis, only preoperative KPS (P = .009), ASA status (P = .02), and histology type (P = .03) showed significant association with postoperative complications.

CONCLUSIONS

We found that the neurologic and clinical preoperative condition and grade III gliomas were factors related to postoperative complications, whereas age, extent of resection, and number of surgeries were not risk factors. We believe that these conclusions provide an additional benchmark for future multicentric studies that focus on the selection criteria for resection of malignant brain tumors.

New concepts in surgery of WHO grade II gliomas: functional brain mapping, connectionism and plasticity – a review

Despite a recent literature supporting the impact of surgery on the natural history of low-grade glioma (LGG), the indications of resection still remain a matter of debate, especially because of the frequent location of these tumors within eloquent brain areas - thus with a risk to induce a permanent postoperative deficit. Therefore, since the antagonist nature of this surgery is to perform the most extensive glioma removal possible, while preserving the function and the quality of life, new concepts were recently applied to LGG resection in order to optimize the benefit/risk ratio of the surgery.First, due to the development of functional mapping methods, namely perioperative neurofunctional imaging and intrasurgical direct electrical stimulation, the study of cortical functional organization is currently possible for each patient - in addition to an extensive neuropsychological assessment. Such knowledge is essential because of the inter-individual anatomo-functional variability, increased in tumors due to cerebral plasticity phenomena. Thus, brain mapping enables to envision and perform a resection according to individual functional boundaries.Second, since LGG invades not only cortical but also subcortical structures, and shows an infiltrative progression along the white matter tracts, new techniques of anatomical tracking and functional mapping of the subcortical white matter pathways were also used with the goal to study the individual effective connectivity - which needs imperatively to be preserved during the resection.Third, the better understanding of brain plasticity mechanisms, induced both by the slow-growing LGG and by the surgery itself, were equally studied in each patient and applied to the surgical strategy by incorporating individual dynamic potential of reorganization into the operative planning. The integration of these new concepts of individual functional mapping, connectivity and plastic potential to the surgery of LGG has allowed an extent of surgical indications, an optimization of the quality of resection (neuro-oncological benefit), and a minimization of the risk of sequelae (benefit on the quality of life). In addition, such a strategy has also fundamental applications, since it represents a new door to the connectionism and cerebral plasticity.

Diffusely infiltrative low-grade gliomas in adults

Diffusely infiltrating low-grade gliomas (LGGs) include astrocytomas, oligodendrogliomas, and mixed oligoastrocytomas (WHO grade 2). Due to the routine use of magnetic resonance imaging, there is an increasing need to formulate treatment guidelines for patients with LGGs. However, there is little consensus about the optimal treatment strategy for diffusely infiltrative LGGs, and the clinical management of LGGs is one of the most controversial areas in neurooncology. Although the standard of care has not been established, several randomized trials are beginning to provide some answers. Furthermore, laboratory correlative studies are defining subsets of LGG that may identify patients with better prognoses and increased chance of responding to therapy. This article reviews the most recent data regarding the treatment of LGG, emphasizing evidenced based approaches from current clinical trials.

Contribution of intraoperative electrical stimulations in surgery of low grade gliomas: a comparative study between two series without (1985-96) and with (1996-2003) functional mapping in the same institution

OBJECTIVES

Despite the growing use of intraoperative functional mapping in supratentorial low grade glioma (LGG) surgery, few studies have compared series of patients operated on without and with direct electrical stimulation (DES) by the same team. The present study compared the rate of LGG surgery performed in eloquent areas, the rate of postoperative sequelae, and the quality of resection during two consecutive periods in the same department-the first without and the second with the use of intraoperative electrophysiology.

METHODS

Between 1985 and 1996, 100 patients harbouring a supratentorial LGG underwent surgery with no functional mapping (S1). Between 1996 and 2003, 122 patients were operated on in the same department for a supratentorial LGG using intraoperative cortico-subcortical DES (S2).

RESULTS

Comparison between the two series showed that 35% of LGGs were operated on in eloquent areas in S1 versus 62% in S2 (p<0.0001), with 17% severe permanent deficits in S1 versus 6.5% in S2 (p<0.019). On postoperative MRI, 37% of resections were subtotal and 6% total in S1 versus 50.8% and 25.4%, respectively, in S2 (p<0.001). In both groups, survival was significantly related to the quality of resection.

CONCLUSIONS

The results of the present study allow, for the first time, quantification of the contribution of intraoperative DES in LGG resection. Indeed, the use of this method leads to the extension of indications of LGG surgery within eloquent areas; to a decrease in the risk of sequelae; and to improvement of the quality of tumour resection, with an impact on survival.

Low-grade glioma: supratentorial astrocytoma, oligodendroglioma, and oligoastrocytoma in adults

Low-grade glioma is not a single diagnosis but a category of biologically diverse neoplasms. They are indolent, progressive, and, following anaplastic transformation, invariably fatal. Neuro-oncologists have not established a treatment standard for these tumors. However, it is clear that "low-grade" is not synonymous with "benign," and treatment is required sometime in the course of the disease. Previously, achieving a consensus had been limited by a lack of class I evidence. Physicians treated patients based on retrospective series and personal experience. Currently, results from prospective clinical trials are becoming available. These studies have provided data that may serve as treatment guidelines. Additional results regarding the identification of prognostic variables have raised more questions to be answered. Attention is now directed to the importance of translational research to better define these neoplasms. In the future, it will be necessary to distinguish among low-grade gliomas and identify therapies that may differ between them.

Surgical removal of corpus callosum infiltrated by low-grade glioma: functional outcome and oncological considerations

Object. Although still controversial, many authors currently advocate extensive resection in the treatment of low-grade gliomas (LGGs). Because these tumors usually migrate along white matter pathways, the corpus callosum is often invaded. Nevertheless, there is evidently no specific study featuring resection of the corpus callosum infiltrated by glioma, despite abundant literature concerning callosotomy in epilepsy surgery or transcallosal ventricular approaches. The aim of this paper was to analyze functional outcome following removal of corpus callosum invaded by LGG and to analyze the impact of this callosectomy on the quality of resection.

Methods. Between 1996 and 2002, a total of 32 patients harboring an LGG involving part of the corpus callosum and having no or only a mild preoperative deficit underwent surgery aided by intraoperative electrical mapping to preserve eloquent structures identified on stimulation and to perform the most extensive resection possible.

Preoperatively, no clinical response was elicited on stimulation of the corpus callosum; thus, the part of this structure that was invaded by LGG was removed. Despite immediate postoperative neurological worsening, all patients but one recovered within 3 months and returned to a normal socioprofessional life. The additional callosectomy allowed for nine total resections, 18 subtotal resections, and five partial resections. Furthermore, only two cases of contralateral hemispherical migration occurred during a median follow up of 3 years.

Conclusions. Resection of the corpus callosum infiltrated by glioma improves the quality of tumor removal without increasing the risk of sequelae.