Predictors of Postoperative Seizure Outcome in Low Grade Glioma: From Volumetric Analysis to Molecular Stratification

Congress of Neurological Surgeons systematic review and evidence-based guidelines for the role of surgery in the management of patients with diffuse low grade glioma: update

Target populationAdults with imaging suggestive of a WHO grade II diffuse gliomas (oligodendrogliomas or astrocytomas)QuestionIn adults with imaging suggestive of a WHO grade II diffuse gliomas (oligodendrogliomas or astrocytomas), does surgical resection improve overall survival compared to observation or biopsy?Updated Recommendation from the Prior Version of These Guidelines:Level III: In adults with imaging suggestive of a WHO grade II diffuse gliomas (oligodendrogliomas or astrocytomas), surgical resection is suggested over observation or biopsy to improve overall survival.Question Q2In adults with imaging suggestive of a WHO grade II diffuse gliomas (oligodendrogliomas or astrocytomas), does maximal surgical resection improve progression free survival (PFS) and overall survival (OS) compared to subtotal resection/biopsy?Unchanged Recommendations from the Prior Version of These GuidelinesLevel II It is recommended that GTR or STR be accomplished instead of biopsy alone when safe and feasible so as to decrease the frequency of tumor progression recognizing that the rate of progression after GTR is fairly high.Level III Greater extent of resection can improve OS in WHO grade II diffuse gliomas patients. New RecommendationsLevel III: It is suggested that extent of resection be maximized as is safely possible for IDH mutant and IDHwt WHO grade II diffuse gliomas. to improve PFS and OS. Level III: There is insufficient evidence that greater extent of resection of 1p19q codeleted oligodendrogliomas (WHO grade II diffuse gliomas) improves OS Question Q3In adults with imaging suggestive of a WHO grade II diffuse gliomas (oligodendrogliomas or astrocytomas), does the addition of intraoperative MRI and/or intraoperative ultrasound during surgery improve extent of resection?Unchanged Recommendation from the Prior Version of These GuidelinesLevel III: The use of intraoperative MRI is suggested to increase the extent of resection for adults with WHO grade II diffuse glioma.New RecommendationLevel III: The use of intraoperative ultrasound is suggested to increase the extent of resection compared to conventional surgery for adults with WHO grade II diffuse glioma.Question 4In adults with imaging suggestive of a WHO grade II diffuse glioma (oligodendrogliomas or astrocytomas) with seizures, does maximal surgical resection improve seizure control compared to observation or subtotal resection/biopsy?Updated Recommendation from the Prior Version of These GuidelinesLevel III: In adults with imaging consistent with a WHO Grade II diffuse glioma who present with seizure activity, surgical resection of greater than 90% of the lesion, when it can be accomplished safely, is suggested over observation or lesser extent of resection/biopsy to improve seizure control.New Questions and RecommendationsQuestion 5In adults with imaging suggestive of a WHO grade II diffuse glioma (oligodendrogliomas or astrocytomas), does use of intraoperative fluorescent guided surgery improve extent of resection?RecommendationLevel III: Intraoperative fluorescent guided surgery with 5-ALA is not suggested to improve the extent of resection for WHO grade II gliomas.Question 6In adults with imaging suggestive of a WHO grade II diffuse glioma (oligodendrogliomas or astrocytomas) in eloquent brain cortex, does awake craniotomy or other methods of intraoperative mapping increase extent of resection compared to conventional surgery without these techniques?RecommendationLevel III: It is suggested that awake craniotomy and other methods of intraoperative mapping can be used to increase the extent of resection for adults with WHO grade II diffuse glioma.Question 7In adults with imaging suggestive of a WHO grade II diffuse glioma (oligodendrogliomas or astrocytomas) in eloquent brain cortex, does use of advanced preoperative imaging modalities in the form of fMRI and/or DTI decrease surgical morbidity?RecommendationLevel III: The use of functional MRI and DTI related modalities are suggested to decrease surgical morbidity in adults with WHO grade II diffuse glioma.

Epilepsy as primary tumor manifestation correlates with patient status, age, and tumor volume but not with survival in elderly glioblastoma patients: a retrospective bicentric analysis

Assessment of the potential impact of epilepsy as primary tumor manifestation on survival in elderly glioblastoma multiforme (GBM) patients. Two academic neurosurgical centers retrospectively analyzed all GBM patients aged 65 years and older with de-novo tumors, who underwent surgery between 2006 and 2021. Epidemiological, histopathological, imaging and survival data were obtained from patients' electronic charts, and screened for the presence of epilepsy preoperatively and during follow-up. Patient status was assessed by the Karnofsky Performance Scale (KPS), epilepsy was evaluated using the Engel classification. Patients were categorized in an epilepsy cohort (i.e. patients with epilepsy as primary GBM manifestation, and a reference cohort (i.e. patients with no initial epilepsy). This study analyzed 451 GBM patients (55% males); median age at tumor diagnosis was 73 years. The epilepsy cohort was younger (71.0 vs. 74.0 year; p = 0.001), had better KPS (80 vs. 70; p = 0.039), and had smaller tumors (127 vs. 221 cm3; p = 0.001) compared to the reference cohort. There were no differences with regard to neurosurgical treatment (i.e. resection vs. biopsy), tumor biomarkers, surgery-associated complications, and performed adjuvant treatment (all p > 0.05). We did not detect a significant difference in median survival between the epilepsy and reference cohorts (8 vs. 6 months; p = 0.21). New epilepsy during follow-up often coincided with tumor recurrence/progression, but also did not significantly affect survival. The majority of patients (98%) achieved seizure freedom by a combination of tumor-specific treatments and antiseizure medication. Epilepsy as primary tumor manifestation does not correlate with survival in elderly GBM patients.

Preoperative Diffusion Tensor Imaging and Neurite Dispersion and Density Imaging in Isocitrate Dehydrogenase-Mutant Grade 2 and 3 Gliomas: Definition of Tumor-Related Epilepsy and Predictive Factors of Seizure Outcomes Based on a Single-Center Retrospective Case Series

BACKGROUND AND OBJECTIVES

Understanding and managing seizure activity is crucial in neuro-oncology, especially for highly epileptogenic lesions like isocitrate dehydrogenase (IDH)-mutant gliomas. Advanced MRI techniques such as diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) have been used to describe microstructural changes associated with epilepsy. However, their role in tumor-related epilepsy (TRE) remains unclear. This study aims to investigate the role of DTI and NODDI tumor-derived metrics in defining TRE and predicting postoperative seizure outcomes in patients undergoing surgical resection for IDH-mutant grade 2 and 3 gliomas.

METHODS

This was a single-center retrospective study. Preoperative DTI parameters included fractional anisotropy and mean diffusivity. NODDI parameters included neurite density index (NDI), orientation dispersion index, and free-water fraction (FWF). These metrics were calculated within three volumes of interest (fluid-attenuated inversion recovery [FLAIR] tumor volume, FLAIR peripheral zone, and FLAIR central zone [Fcz]) and correlated with seizure presentation, type, and postoperative control, which was reported according to the Engel classification system.

RESULTS

Fifty-seven patients were included in this study. Increased NODDI-derived FWF-Fcz (P = .031) and NDI-Fcz (P = .046) values correlated with preoperative generalized seizure presentation, although only the FWF-Fcz confirmed its statistical significance (P = .047) in the multivariate analysis. Lower mean diffusivity-FLAIR tumor volume correlated with poor postoperative seizure control both in the univariate (P = .015, P = .026) and multivariate analyses (P = .024, P = .036), while a trend toward significance was found between higher NDI-FLAIR peripheral zone and worse seizure control (P = .055).

CONCLUSION

DTI and NODDI tumor-derived quantitative parameters may define TRE and predict postoperative seizure outcomes in patients with IDH-mutant gliomas. Notably, DTI metrics were found to be independent predictors of postoperative seizure outcomes, while preoperative NODDI parameters correlated with seizure presentation. Further research is warranted to validate our findings and to better understand the underlying mechanisms driving TRE.

Prospects for the use of perampanel in the treatment of epilepsy in patients with malignant gliomas of the brain

Epilepsy occurs in 35–95% of patients with low-grade malignant cerebral gliomas and in 29–71% of patients with high-grade gliomas. Seizures can be the first manifestation of a malignant cerebral glioma or may develop in the postoperative period and during chemoradiation therapy. This necessitates the use of antiepileptic drugs that can control seizures, ensure seizure prevention, and provide secondary seizure prophylaxis without reducing the effectiveness of anticancer therapy or the patient’s quality of life. The processes of epileptogenesis and oncogenesis are closely interrelated through common developmental mechanisms, with glutamate playing a key role. Increased glutamate secretion is accompanied by elevated expression and activation of its receptors, which raises seizure susceptibility. This is associated with increased levels of brain-derived neurotrophic factor, the number of synapses between peritumoral neurons and glioma cells, and the expression of various growth factors, all of which contribute to tumor progression. In this context, special attention is given to perampanel, a glutamate receptor antagonist and third-generation antiepileptic drug, in the treatment of epilepsy in patients with malignant cerebral gliomas. It has been shown that perampanel not only effectively controls seizures in patients with malignant cerebral gliomas but also suppresses tumor progression. Perampanel can dose-dependently enhance apoptosis and disrupt cell migration in malignant glioma cell lines. A synergistic effect of perampanel in combination with temozolamide has been identified. During chemoradiation therapy, perampanel exerts a protective effect on healthy peritumoral tissues. Adverse drug reactions associated with perampanel use are infrequent and mild. Further research is needed to investigate the anticonvulsant and antitumor efficacy of perampanel for the treatment of epilepsy in patients with malignant brain tumors.

The course of tumor-related epilepsy in glioblastoma patients: A retrospective analysis

PURPOSE

Many patients with glioblastoma suffer from tumor-related seizures. However, there is limited data on the characteristics of tumor-related epilepsy achieving seizure freedom. The aim of this study was to characterize the course of epilepsy in patients with glioblastoma and the factors that influence it.

METHODS

We retrospectively analyzed the medical records of glioblastoma patients treated at the University Hospital Erlangen between 01/2006 and 01/2020.

RESULTS

In the final cohort of patients with glioblastoma (n = 520), 292 patients (56.2 %) suffered from tumor-related epilepsy (persons with epilepsy, PWE). Levetiracetam was the most commonly used first-line antiseizure medication (n = 245, 83.9 % of PWE). The onset of epilepsy was preoperative in 154/292 patients (52.7 %). 136 PWE (46.6 %) experienced only one single seizure while 27/292 PWE (9.2 %) developed drug-resistant epilepsy. Status epilepticus occurred in 48/292 patients (16.4 %). Early postoperative onset (within 30 days of surgery) of epilepsy and total gross resection (compared with debulking) were independently associated with a lower risk of further seizures. We did not detect dose-dependent pro- or antiseizure effects of radiochemotherapy.

CONCLUSION

Tumor-related epilepsy occurred in more than 50% of our cohort, but drug-resistant epilepsy developed in less than 10% of cases. Epilepsy usually started before tumor surgery.

Patient-Centered Management of Brain Tumor-Related Epilepsy

PURPOSE OF REVIEW

Brain tumor-related epilepsy is a heterogenous syndrome involving variability in incidence, timing, pathophysiology, and clinical risk factors for seizures across different brain tumor pathologies. Seizure risk and disability are dynamic over the course of disease and influenced by tumor-directed treatments, necessitating individualized patient-centered management strategies to optimize quality of life.

RECENT FINDINGS

Recent translational findings in diffuse gliomas indicate a dynamic bidirectional relationship between glioma growth and hyperexcitability. Certain non-invasive measures of hyperexcitability are correlated with survival outcomes, however it remains uncertain how to define and measure clinically relevant hyperexcitability serially over time. The extent of resection, timing of pre-operative and/or post-operative seizures, and the likelihood of tumor progression are critical factors impacting the risk of seizure recurrence. Newer anti-seizure medications are generally well-tolerated with similar efficacy in this population, and several rapid-onset seizure rescue agents are in development and available. Seizures in patients with brain tumors are strongly influenced by the underlying tumor biology and treatment. An improved understanding of the interactions between tumor cells and the spectrum of hyperexcitability will facilitate targeted therapies. Multidisciplinary management of seizures should occur with consideration of tumor-directed therapy and prognosis, and anti-seizure medication decision-making tailored to the individual priorities and quality of life of the patient.

Exosomal TNF-α mediates voltage-gated Na+ channel 1.6 overexpression and contributes to brain tumor-induced neuronal hyperexcitability

Patients affected by glioma frequently experience epileptic discharges; however, the causes of brain tumor-related epilepsy (BTRE) are still not completely understood. We investigated the mechanisms underlying BTRE by analyzing the effects of exosomes released by U87 glioma cells and by patient-derived glioma cells. Rat hippocampal neurons incubated for 24 hours with these exosomes exhibited increased spontaneous firing, while their resting membrane potential shifted positively by 10-15 mV. Voltage clamp recordings demonstrated that the activation of the Na+ current shifted toward more hyperpolarized voltages by 10-15 mV. To understand the factors inducing hyperexcitability, we focused on exosomal cytokines. Western blot and ELISAs showed that TNF-α was present inside glioma-derived exosomes. Remarkably, incubation with TNF-α fully mimicked the phenotype induced by exosomes, with neurons firing continuously, while their resting membrane potential shifted positively. Real-time PCR revealed that both exosomes and TNF-α induced overexpression of the voltage-gated Na+ channel Nav1.6, a low-threshold Na+ channel responsible for hyperexcitability. When neurons were preincubated with infliximab, a specific TNF-α inhibitor, the hyperexcitability induced by exosomes and TNF-α was drastically reduced. We propose that infliximab, an FDA-approved drug to treat rheumatoid arthritis, could ameliorate the conditions of glioma patients with BTRE.

Association of Clinical, Tumor, and Treatment Characteristics With Seizure Control in Patients With IDH1/2-Mutant Lower-Grade Glioma

BACKGROUND AND OBJECTIVES

Patients with IDH1/2-mutant lower-grade glioma have a high frequency of seizures. We aimed to investigate the correlations between seizures and tumor/patient characteristics and the impact of surgery and adjuvant treatments (AT) on seizure control along the disease trajectory.

METHODS

We retrospectively included patients with IDH1/2-mutant lower-grade glioma who underwent surgery at the neurosurgery divisions of the University of Turin and Milan and were treated at the Division of Neuro-Oncology of Turin. Inclusion criteria were a diagnosis according to the 2021 WHO Classification and presentation with seizures; exclusion criteria were presence of CDKN2A/B homozygous deletion, intense/ring contrast enhancement on MRI at presentation, and small tissue biopsy. We evaluated seizure freedom for 2 months after surgery, 6 months from starting observation or AT, at recurrence, and for 6 months after treatments of recurrence.

RESULTS

We included 150 patients. There were 77 (51%) and 31 (21%) patients with IDH-mutant/1p19q-codeleted grade 2 and 3 oligodendroglioma and 30 (20%) and 12 (8%) with IDH-mutant grade 2 and 3 astrocytoma, respectively. Total resection was accomplished in 68 (45%). Seventy-five patients (50%) received AT while the remaining 75 were observed with MRI. After 6 months after AT, 28 of 29 patients (96.5%) displayed seizure reduction, 5 of 28 (18%) being seizure-free. 66 of 124 patients (53%) had seizures at recurrence. After 6 months after second-line treatments, 60 of 66 patients (91%) had seizure reduction, 11 (17%) being seizure-free. In multivariable analyses, grade 3 histology positively correlated with seizure freedom at 2 months after surgery (OR 3.5, 1.4-8.9, p = 0.008), 6 months after AT (OR 9.0, 1.5-54.9, p = 0.017), and 6 months after treatment of recurrence (OR 4.9, 1.5-16.5, p = 0.009). Adjuvant radiotherapy reduced seizures at recurrence in a univariate analysis (OR 0.14, 0.03-0.7, p = 0.020). Patients with seizure freedom after surgery and AT displayed longer progression-free survival (PFS) (65, 24.5-105, vs 48 months, 32-63.5, p = 0.037).

DISCUSSION

This study analyzed seizure control in patients with IDH1/2-mutant lower-grade glioma across multiple time points. Grade 3 correlated with better seizure control throughout the entire disease trajectory, and seizure freedom after surgery and AT correlated with a longer PFS regardless of tumor grade. These results could serve as an external control arm in clinical trials evaluating the efficacy on seizures of antitumor agents in patients with IDH-mutant lower-grade glioma.

Pre-operative predictors of post-operative seizure control in low-grade glioma: a systematic review and meta-analysis

As many as 80% of low-grade gliomas (LGGs) present with seizures, negatively impacting quality of life. While seizures are associated with gliomas regardless of grade, the importance of minimizing impact of seizures for patients with low grade tumors cannot be understated given the prolonged survival period in this population. The objective of this systematic review and meta-analysis was to summarize existing literature and identify factors associated with post-operative seizure control (defined as Engel I classification) in patients with LGGs, with a focus on pre-operative factors. Patient data extracted include tumor location and histology, pre-operative anti-seizure medication use, extent of resection (EOR), adjuvant treatment, pre-operative seizure type, duration, and frequency, and post-operative Engel classification. A random-effects model was used to calculate the effects of EOR, pre-operative seizure duration, adjuvant radiation, and adjuvant chemotherapy on post-operative seizure control. The effect of tumor location and histology on post-operative Engel I classification was determined using contingency analyses. Thirteen studies including 1628 patients with seizures were included in the systematic review. On meta-analyses, Engel I classification was associated with pre-operative seizure type (OR = 0.79 (0.63-0.99), p = 0.0385, focal versus generalized), frontal lobe LGGs (OR = 1.5 (1.1-2.0), p = 0.0195), and EOR (OR (95% CI) = 4.5 (2.3-6.7), p < 0.0001 gross-total versus subtotal). Pre-operative seizure duration less than one year, adjuvant radiation, adjuvant chemotherapy, and tumor histology were not associated with achieving Engel I classification. In addition to the known effects of EOR, Engel I classification is less likely to be achieved in patients with focal pre-operative seizures and more likely to be achieved in patients with frontal lobe LGGs.

Glioma genetic profiles associated with electrophysiologic hyperexcitability

BACKGROUND

Distinct genetic alterations determine glioma aggressiveness, however, the diversity of somatic mutations contributing to peritumoral hyperexcitability and seizures over the course of the disease is uncertain. This study aimed to identify tumor somatic mutation profiles associated with clinically significant hyperexcitability.

METHODS

A single center cohort of adults with WHO grades 1-4 glioma and targeted exome sequencing (n = 1716) was analyzed and cross-referenced with a validated EEG database to identify the subset of individuals who underwent continuous EEG monitoring (n = 206). Hyperexcitability was defined by the presence of lateralized periodic discharges and/or electrographic seizures. Cross-validated discriminant analysis models trained exclusively on recurrent somatic mutations were used to identify variants associated with hyperexcitability.

RESULTS

The distribution of WHO grades and tumor mutational burdens were similar between patients with and without hyperexcitability. Discriminant analysis models classified the presence or absence of EEG hyperexcitability with an overall accuracy of 70.9%, regardless of IDH1 R132H inclusion. Predictive variants included nonsense mutations in ATRX and TP53, indel mutations in RBBP8 and CREBBP, and nonsynonymous missense mutations with predicted damaging consequences in EGFR, KRAS, PIK3CA, TP53, and USP28. This profile improved estimates of hyperexcitability in a multivariate analysis controlling for age, sex, tumor location, integrated pathologic diagnosis, recurrence status, and preoperative epilepsy. Predicted somatic mutation variants were over-represented in patients with hyperexcitability compared to individuals without hyperexcitability and those who did not undergo continuous EEG.

CONCLUSION

These findings implicate diverse glioma somatic mutations in cancer genes associated with peritumoral hyperexcitability. Tumor genetic profiling may facilitate glioma-related epilepsy prognostication and management.

Glioma-related epilepsy following low-grade glioma surgery

Background

Epileptic seizures commonly burden low-grade glioma (LGG) patients and negatively impact quality of life, neurocognition, and general patient health. Anti-seizure medications (ASMs) are used to manage seizures but can result in undesired side effects. Our aim was to report our experience in epilepsy in one of the largest case series of LGG patients (reclassified in accordance with the WHO 2021 classification). Furthermore, we evaluate our postoperative seizure frequency difference between LGG patients who use preoperative ASMs and ones with no ASMs.

Methods

Data were retrospectively collected from Salford Royal Hospital electronic records and Neuro-Oncology database from 2006 to 2022. Descriptive statistics were performed for demographic analysis, while multivariable analysis was used to determine postoperative seizure-free outcomes.

Results

In total, 257 operations were performed on 206 patients. Postoperatively, 114 patients suffered from seizures, and approximately 45.2% of patients developed seizures at 3-12 months postsurgery, with the odds higher in patients on preoperative ASMs. There was no evidence to suggest a higher postoperative seizure rate in patients undergoing awake craniotomy versus general anesthetic. The extent of resection (EOR) was inversely related to seizure failure, with gross-total resection showing a statistically significant reduction in seizures in comparison to all other surgical resections.

Conclusions

In our experience, there is no evidence to suggest a reduced postoperative seizure outcome when prescribing preoperative ASMs. EOR is an independent prognosticator for postoperative seizure failure with all other variables demonstrating nonsignificance. Overall, a larger study can investigate the role of ASMs in LGG in greater detail.

What neurologists can do for neuro-oncology patients

Neuro-oncology is a branch of medical science concerned with managing central nervous system tumours and neurological complications of cancer. Patients with brain tumours need a multidisciplinary approach to their care and neurologists can play a key part within that team. This review shows how neurologists can contribute to the care of patients with neuro-oncological disease at various points during the illness, including at initial diagnosis, during symptom management and at end of life assisting with palliative seizure management. The review focuses on brain tumour-related epilepsy, the complications of brain tumour treatments and the neurological complications of systemic cancer treatments including immunotherapies.

Survival, Functional, and Seizure Control Outcomes After Resection of Perirolandic World Health Organization Grade II and III Gliomas: A Single-Center Retrospective Review

OBJECTIVE

We aimed to assess, in patients with perirolandic gliomas and gliomas originating from other regions, survival, functional outcomes, and seizure control and, in addition, to identify any clinical characteristics predictive of progression-free survival, overall survival, and seizure control.

METHODS

We retrospectively analyzed 87 patients who underwent resection of World Health Organization grade II or III gliomas at a single institution between 2009 and 2021. Tumors were classified by topographic involvement. One-year postoperative functional status was quantified with Karnofsky Performance Status. One-year seizure control was defined by Engel seizure classification. Dichotomous and categorical variables were reported as counts and percentages and compared using Fisher exact test. A Cox regression model was used to identify covariates that affect progression-free survival and overall survival.

RESULTS

Patients with perirolandic gliomas had similar survival and functional outcomes to patients with gliomas from other regions and a low rate of lasting neurologic deficits. Patients with perirolandic gliomas had comparatively worse long-term seizure outcomes (approached statistical significance). Perirolandic involvement (hazard ratio [HR], 0.10; 95% confidence interval [CI], 0.02-0.46; P = 0.005) and preoperative seizures (HR, 0.14; 95% CI, 0.02-0.62; P = 0.017) conferred a lower likelihood of durable seizure control, whereas increased extent of resection (HR, 1.07; 95% CI, 1.03-1.12; P = 0.003) enhanced the likelihood of seizure freedom.

CONCLUSIONS

Despite proximity to or presence in eloquent structures, perirolandic gliomas can largely be resected without incurring worse functional outcomes. Patients with perirolandic gliomas should be considered for maximal safe resection to optimize survival outcomes and improve seizure control.

Insula in epilepsy - "untying the gordian knot": A systematic review

PURPOSE

Despite significant advances in epileptology, there are still many uncertainties about the role of the insula in epilepsy. Until recently, most insular onset seizures were wrongly attributed to the temporal lobe. Further, there are no standardised approaches to the diagnosis and treatment of insular onset seizures. This systematic review gathers the available information about insular epilepsy and synthesizes current knowledge as a basis for future research.

METHOD

Adhering to the PRISMA guidelines, studies were meticulously extracted from the PubMed database. The empirical data pertaining to the semiology of insular seizures, insular networks in epilepsy, techniques of mapping the insula, and the surgical intricacies of non-lesional insular epilepsy were reviewed from published studies. The corpus of information available was then subjected to a process of concise summarization and astute synthesis.

RESULTS

Out of 235 studies identified for full-text review, 86 studies were included in the systematic review. The insula emerges as a brain region with a number of functional subdivisions. The semiology of insular seizures is diverse and depends on the involvement of particular subdivisions. The semiological heterogeneity of insular seizures is explained by the extensive connectivity of the insula and its subdivisions with all four lobes of the brain, deep grey matter structures, and remote brainstem areas. The mainstay of the diagnosis of seizure onset in the insula is stereoelectroencephalography (SEEG). The surgical resection of the insular epileptogenic zone (when possible) is the most effective treatment. Open surgery on the insula is challenging but magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) also holds promise.

CONCLUSION

The physiological and functional roles of the insula in epilepsy have remained obfuscated. The dearth of precisely defined diagnostic and therapeutic protocols acts as an impediment to scientific advancement. This review could potentially facilitate forthcoming research endeavours by establishing a foundational framework for uniform data collection protocols, thereby enhancing the feasibility of comparing findings across future studies and promoting progress in this domain.

Low-grade epilepsy-associated neuroepithelial tumors: Tumor spectrum and diagnosis based on genetic alterations

Brain tumors can always result in seizures when involving the cortical neurons or their circuits, and they were found to be one of the most common etiologies of intractable focal seizures. The low-grade epilepsy-associated neuroepithelial tumors (LEAT), as a special group of brain tumors associated with seizures, share common clinicopathological features, such as seizure onsets at a young age, a predilection for involving the temporal lobe, and an almost benign course, including a rather slow growth pattern and thus a long-term history of seizures. Ganglioglioma (GG) and dysembryoplastic neuroepithelial tumor (DNET) are the typical representatives of LEATs. Surgical treatments with complete resection of tumors and related epileptogenic zones are deemed the optimal way to achieve postoperative seizure control and lifetime recurrence-free survival in patients with LEATs. Although the term LEAT was originally introduced in 2003, debates on the tumor spectrum and the diagnosis or classification of LEAT entities are still confusing among epileptologists and neuropathologists. In this review, we would further discuss these questions, especially based on the updated classification of central nervous system tumors in the WHO fifth edition and the latest molecular genetic findings of tumor entities in LEAT entities.

Risk Factors for Intraoperative Seizures in Glioma Surgery: Electrocorticography Matters

PURPOSE

Few and contradictory data are available regarding intraoperative seizures during surgery for low-grade gliomas. Aim of this study was to evaluate possible risk factors for the occurrence of IOS.

METHODS

The authors performed a retrospective analysis of 155 patients affected by low-grade gliomas and tumor-related epilepsy, who underwent surgery in our Department, between 2007 and 2018. A statistical analysis was performed by means of univariate and multivariate regression to evaluate any possible correlation between seizure occurrence and several demographic, clinical, neurophysiological, and histopathological features.

RESULTS

Intraoperative seizure occurred in 39 patients (25.16%) with a total of 62 seizure events recorded. Focal seizures were the prevalent seizure type: among them, 39 seizures did not show motor signs, being those with only electrographic and/or with cognitive features the most represented subtypes. Twenty-six seizures occurring during surgery were not spontaneous: direct cortical stimulation with Penfield paradigm was the most prevalent evoking factor. The univariate analysis showed that the following prognostic factors were statistically associated with the occurrence of intraoperative seizure: the awake technique ( P = 0.01) and the interictal epileptiform discharges detected on the baseline electrocorticography (ECoG) ( P < 0.001). After controlling for confounding factors with multivariate analysis, the awake surgery and the epileptic ECoG pattern kept statistical significance.

CONCLUSIONS

The awake surgery procedure and the epileptic ECoG pattern are risk factors for intraoperative seizure. ECoG is mandatory to detect electrographic seizures or seizures without motor signs.

Resective surgery for patients with frontal lobe diffuse low-grade glioma-related epilepsy: predictors of seizure outcomes

Background

Diffuse low-grade gliomas (DLGGs) are prone to invade the frontal lobes, with seizures being the most common symptom. However, limited attention has been paid to surgical outcomes and their predictors in patients with frontal DLGG-related epilepsy.

Objective

This study aimed to analyze predictors of postoperative seizure outcomes in patients with frontal DLGG-related epilepsy.

Design

This is a single-center retrospective study.

Methods

This study retrospectively collected data of 115 patients with frontal DLGG-related epilepsy who underwent resective surgery between January 2014 and January 2021. Patients were categorized into favorable and unfavorable seizure outcome groups based on the International League Against Epilepsy (ILAE) classification. Univariate and multivariate analyses were used to identify potential predictors of seizure outcomes.

Results

The mean follow-up was 4.11 ± 2.06 years, and 77.4% (89 of 115) of patients were seizure-free. Permanent neurological deficits were observed in 7.0% (8 of 115) of patients. Univariate and multivariate analyses revealed that total tumor removal [odds ratio (OR), 0.31; 95% confidence interval (CI), 0.12-0.82; p = 0.018] and older age at seizure onset (OR, 0.96; 95% CI, 0.93-0.99; p = 0.042) were independent predictors of favorable seizure outcomes.

Conclusion

Surgical resection is an effective treatment for frontal DLGG-related epilepsy. Favorable seizure outcomes are more likely to be achieved in patients with complete tumor removal and those with older age at seizure onset.

Predictors of seizure outcomes in patients with diffuse low-grade glioma-related epilepsy after complete glioma removal

AIMS

We aimed to identify predictors of postoperative seizures in patients with diffuse low-grade glioma (DLGG)-related epilepsy after complete tumor resection in this study.

METHODS

We retrospectively collected data from individuals with DLGG-related epilepsy whose tumors were completely resected at Xiangya Hospital, Central South University between January 2014 and January 2020. The predictors of seizure outcomes were assessed by employing univariate analysis and a multivariate logistic regression model in a backward binary logistic regression model.

RESULTS

Among the 118 cases that met the inclusion criteria, 83.05% were seizure-free following an average follow-up of 4.27 ± 1.65 years, all of whom were classified as International League Against Epilepsy class I outcome. Univariate and multivariate analyses indicated that seizure duration of >6 years (odds ratio [OR], 6.62; 95% confidence interval [CI], 1.76-24.98; p = 0.005) and first clinical symptoms other than seizures (OR, 4.51; 95% CI, 1.43-14.23; p = 1.010) were both independent predictors of unfavorable seizure outcomes.

CONCLUSION

Our results imply that satisfactory seizure outcomes can be achieved in most patients with DLGG-related epilepsy after complete tumor resection. Patients with seizure duration of >6 years or first clinical symptoms other than seizures were more likely to experience postoperative seizure recurrence.

Changes in clinical management of diffuse IDH-mutated lower-grade gliomas: patterns of care in a 15-year period

BACKGROUND

Isocitrate dehydrogenase (IDH) mutated diffuse lower-grade gliomas (dLGG) are infiltrating brain tumors and increasing evidence is in favor of early multimodal treatment. In a Scandinavian population-based setting, we wanted to study treatment patterns over the last 15 years, focusing on the short-term postoperative course to better understand the potential negative consequences of treatment.

METHODS

Patients ≥ 18 years with primary IDH-mutated dLGG grade 2 and 3, operated between January 2007-June 2021 were identified. Patients were divided into subgroups (2007-2011, 2012-2016, and 2017-2021) and comparisons regarding tumor- and disease characteristics, treatment, and postoperative outcome were performed.

RESULTS

We identified 202 patients (n = 61, 2007-2011; n = 72, 2012-2016; n = 69, 2017-2021), where of 193 underwent resection without change in proportion of resections over time. More patients underwent complete resections in recent times (6.1%; 15.7%; 26.1%, respectively; p = 0.016). Forty-two patients had any neurological deficit postoperatively (14.8%; 23.6%; 23.2%; p = 0.379), mostly minor and transient. Differences in oncological therapy were seen between the investigated subgroups. Early radiotherapy alone (32.8%; 7%; 2.9%; p < 0.001), concomitant chemoradiotherapy (23%; 37.5%; 17.4%; p = 0.022), sequential chemoradiotherapy (0%; 18%; 49.3%; p < 0.001), and no adjuvant treatment (42.6%; 23.6%; 18.8%; p = 0.009) shifted during the studied period. Increasingly more patients received proton radiotherapy compared to photon radiotherapy during the later time periods (p < 0.001).

CONCLUSION

Complete resections were performed more often in later time periods without an apparent increase in surgical morbidity. Early adjuvant oncological treatment shifted towards providing chemotherapy and combined chemoradiotherapy more often in later time periods. Protons replaced photons as the radiation modality of choice.

Impact of intraoperative direct cortical stimulation dynamics on perioperative seizures and afterdischarge frequency in patients undergoing awake craniotomy

OBJECTIVE

Intraoperative stimulation is used as a crucial adjunct in neurosurgical oncology, allowing for greater extent of resection while minimizing morbidity. However, limited data exist regarding the impact of cortical stimulation on the frequency of perioperative seizures in these patients.

METHODS

A retrospective chart review of patients undergoing awake craniotomy with electrocorticography data by a single surgeon at the authors' institution between 2013 and 2020 was conducted. Eighty-three patients were identified, and electrocorticography, stimulation, and afterdischarge (AD)/seizure data were collected and analyzed. Stimulation characteristics (number, amplitude, density [stimulations per minute], composite score [amplitude × density], total and average stimulation duration, and number of positive stimulation sites) were analyzed for association with intraoperative seizures (ISs), ADs, and postoperative clinical seizures.

RESULTS

Total stimulation duration (p = 0.005), average stimulation duration (p = 0.010), and number of stimulations (p = 0.020) were found to significantly impact AD incidence. A total stimulation duration of more than 145 seconds (p = 0.04) and more than 60 total stimulations (p = 0.03) resulted in significantly higher rates of ADs. The total number of positive stimulation sites was associated with increased IS (p = 0.048). Lesions located within the insula (p = 0.027) were associated with increased incidence of ADs. Patients undergoing repeat awake craniotomy were more likely to experience IS (p = 0.013). Preoperative antiepileptic drug use, seizure history, and number of prior resections of any type showed no impact on the outcomes considered. The charge transferred to the cortex per second during mapping was significantly higher in the 10 seconds leading to AD than at any other time point examined in patients experiencing ADs, and was significantly higher than any time point in patients not experiencing ADs or ISs. Although the rate of transfer for patients experiencing ISs was highest in the 10 seconds prior to the seizure, it was not significantly different from those who did not experience an AD or IS.

CONCLUSIONS

The data suggest that intraoperative cortical stimulation is a safe and effective technique in maximizing extent of resection while minimizing neurological morbidity in patients undergoing awake craniotomies, and that surgeons may avoid ADs and ISs by minimizing duration and total number of stimulations and by decreasing the overall charge transferred to the cortex during mapping procedures.

Epilepsy treatment in neuro-oncology: A rationale for drug choice in common clinical scenarios

Epilepsy represents a challenge in the management of patients with brain tumors. Epileptic seizures are one of the most frequent comorbidities in neuro-oncology and may be the debut symptom of a brain tumor or a complication during its evolution. Epileptogenic mechanisms of brain tumors are not yet fully elucidated, although new factors related to the underlying pathophysiological process with possible treatment implications have been described. In recent years, the development of new anti-seizure medications (ASM), with better pharmacokinetic profiles and fewer side effects, has become a paradigm shift in many clinical scenarios in neuro-oncology, being able, for instance, to adapt epilepsy treatment to specific features of each patient. This is crucial in several situations, such as patients with cognitive/psychiatric comorbidity, pregnancy, or advanced age, among others. In this narrative review, we provide a rationale for decision-making in ASM choice for neuro-oncologic patients, highlighting the strengths and weaknesses of each drug. In addition, according to current literature evidence, we try to answer some of the most frequent questions that arise in daily clinical practice in patients with epilepsy related to brain tumors, such as, which patients are the best candidates for ASM and when to start it, what is the best treatment option for each patient, and what are the major pitfalls to be aware of during follow-up.

The dual action of glioma-derived exosomes on neuronal activity: synchronization and disruption of synchrony

Seizures represent a frequent symptom in gliomas and significantly impact patient morbidity and quality of life. Although the pathogenesis of tumor-related seizures is not fully understood, accumulating evidence indicates a key role of the peritumoral microenvironment. Brain cancer cells interact with neurons by forming synapses with them and by releasing exosomes, cytokines, and other small molecules. Strong interactions among neurons often lead to the synchronization of their activity. In this paper, we used an in vitro model to investigate the role of exosomes released by glioma cell lines and by patient-derived glioma stem cells (GSCs). The addition of exosomes released by U87 glioma cells to neuronal cultures at day in vitro (DIV) 4, when neurons are not yet synchronous, induces synchronization. At DIV 7-12 neurons become highly synchronous, and the addition of the same exosomes disrupts synchrony. By combining Ca²⁺ imaging, electrical recordings from single neurons with patch-clamp electrodes, substrate-integrated microelectrode arrays, and immunohistochemistry, we show that synchronization and de-synchronization are caused by the combined effect of (i) the formation of new neuronal branches, associated with a higher expression of Arp3, (ii) the modification of synaptic efficiency, and (iii) a direct action of exosomes on the electrical properties of neurons, more evident at DIV 7-12 when the threshold for spike initiation is significantly reduced. At DIV 7-12 exosomes also selectively boost glutamatergic signaling by increasing the number of excitatory synapses. Remarkably, de-synchronization was also observed with exosomes released by glioma-associated stem cells (GASCs) from patients with low-grade glioma but not from patients with high-grade glioma, where a more variable outcome was observed. These results show that exosomes released from glioma modify the electrical properties of neuronal networks and that de-synchronization caused by exosomes from low-grade glioma can contribute to the neurological pathologies of patients with brain cancers.

Pre- and Post-surgical Poor Seizure Control as Hallmark of Malignant Progression in Patients With Glioma?

Background

Regarding brain tumor-related epilepsy (BTRE), there is an increasing number of evidence about a relationship between epileptogenesis and oncogenesis. A recent study suggests a role of post-surgery seizure outcome on the survival of patients with low-grade glioma (LGG), underlying the need for a targeted and aggressive epilepsy treatment.

Objective

This study aims at investigating the possible correlation between pre- and post-surgical seizure control and tumor progression in patients who underwent surgery for LGG.

Methods

We performed a retrospective analysis of patients affected by LGGs and BTRE, in a single high-volume neurosurgical center. Seizure control was assessed before surgery and at 3 years of follow-up. Patients with histological progression in high-grade glioma (HGG) have been evaluated. Clinical features, pre-surgical electroencephalograms (EEGs), and electrocorticography (ECoG) have been analyzed.

Results

Among 154 subjects, we collected 32 patients who presented a tumor progression in HGG during the follow-up period. The majority had poor seizure control both pre- and post-surgery, never being in Engel class Ia throughout the whole history of their disease. Almost all patients with poor seizure control had pathological ECoG recording. Clinical features of seizures did not correlate with seizure outcome. On the univariate analysis, the age, the post-operative Engel class, and the extent of resection (EOR) were the prognostic factors significantly associated with oncological outcome; nevertheless, on multivariate analysis, Engel class significance was not confirmed, and the only predicting factor were age and EOR.

Conclusions

Although not confirmed on multivariate analysis, post-surgical seizure control could be a relevant factor to consider during follow-up of BRTE, in particular, when gross total resection is not achieved. Pathological findings on the ECoG may suggest a “hidden” propensity to malignant progression, strictly related to the persistent neuronal hyper-excitability. Further studies with longer follow-up period are needed to confirm our observations.

Seizures in patients with IDH-mutated lower grade gliomas

PURPOSE

Most patients with Lower Grade Gliomas (LGG) present with epileptic seizures. Since the advent of molecular diagnostics, more homogenous sub-entities have emerged, including the isocitrate dehydrogenase-mutated (IDH-mutated) astrocytomas and 1p19q-codeleted oligodendrogliomas. We aimed to describe the occurrence of seizures in patients with molecularly defined LGG pre- and postoperatively and to analyze factors affecting seizure status postoperatively.

METHODS

A population-based cohort of 130 adult patients with IDH-mutated WHO grade 2 or 3 astrocytomas and oligodendrogliomas was assessed pertaining to seizure burden before and after surgery.

RESULTS

Fifty-four (79.4%) patients with astrocytoma and 45 (72.6%) patients with oligodendroglioma had a history of seizures before surgery. At 12 months postoperatively, 51/67 (76.1%) patients with astrocytoma and 47/62 (75.8%) patients with oligodendrogliomas were seizure free. In a multivariable logistic regression analysis, lower extent of resection (EOR) (OR 0.98; 95% CI 0.97-1.00, p = 0.01) and insular tumor location (OR 5.02; 95% CI 1.01-24.87, p = 0.048) were associated with presence of seizures within 1 year postoperatively in the entire LGG cohort. In sub-entities, EOR was in a similar manner associated with seizures postoperatively in astrocytomas (OR 0.98; 95% CI 0.96-0.99, p < 0.01) but not in oligodendrogliomas (p = 0.34).

CONCLUSION

Our results are well in line with data published for non-molecularly defined LGG with a large proportion of patients being seizure free at 1 year postoperative. Better seizure outcome was observed with increased EOR in astrocytomas, but this association was absent in oligodendrogliomas.

The persistence of seizures after tumor resection negatively affects survival in low-grade glioma patients: a clinical retrospective study

INTRODUCTION

Seizures are the most common clinical manifestation of low-grade glioma (LGG). Many papers hypothesized an influence of epilepsy on glioma progression. To our knowledge, no clinical study demonstrated a direct relationship between persistence of epileptic seizures after surgery and overall survival (OS) in LGG patients. The present study aims at investigating the correlation between post-operative seizure outcome and survival in tumor-related epilepsy (TRE) patients.

METHODS

We performed a retrospective analysis of adult patients affected by TRE who underwent surgery for resection of LGG in a single high-volume neurosurgical center. Seizure outcome was assessed 1 year after surgery and categorized according to Engel classification. Clinical, molecular and radiological features were evaluated in univariate and multivariate analyses to investigate the correlation with OS.

RESULTS

A total of 146 patients met the inclusion criteria. Histopathological diagnosis was Diffuse Astrocytoma isocitrate dehydrogenase (IDH) wild type in 16 patients (11%), Diffuse astrocytoma IDH mutated in 89 patients (61%) and oligodendroglioma IDH mutated, 1p 19q codeleted in 41 patients (28%). 1 year after surgery, 103 (70.6%) patients were in Engel class 1. Median duration of follow-up period was 69.5 months. Median OS was 79.3 (72.2-86.4) months in the whole population, while it was 86.8 (78.4-95.2), 63.9 (45.7-82), 63.7 (45.2-82.2) and 47.5 (18.3-76.6) months for patients in Engel class 1, 2, 3 and 4, respectively. In a univariate analysis, Engel class evaluated 1 year after surgery significantly influenced OS (p < 0.01). Multivariate analysis showed that OS was independently associated with extent of resection (p = 0.02), molecular class (p < 0.01) and Engel class (p = 0.04).

CONCLUSIONS

Seizure control 1 year after surgery significantly predicted survival of patients affected by LGG-related epilepsy in a large monocentric retrospective series. Future studies are needed to confirm these results and to assess if an epilepsy-surgical therapeutic approach may improve OS.

Efficacy of antiepileptic drugs in glioma patients with epilepsy: a systematic review

Background

Comprehensive data on the efficacy and tolerability of antiepileptic drugs (AED) treatment in glioma patients with epilepsy are currently lacking. In this systematic review, we specifically assessed the efficacy of AEDs in patients with a grade II-IV glioma.

Methods

Electronic databases PubMed/MEDLINE, EMBASE, Web of Science, and Cochrane Library were searched up to June 2020. Three different outcomes for both mono- and polytherapy were extracted from all eligible articles: (i) seizure freedom; (ii) ≥50% reduction in seizure frequency; and (iii) treatment failure. Weighted averages (WA) were calculated for outcomes at 6 and 12 months.

Results

A total of 66 studies were included. Regarding the individual outcomes on the efficacy of monotherapy, the highest seizure freedom rate at 6 months was with phenytoin (WA = 72%) while at 12-month pregabalin (WA = 75%) and levetiracetam (WA = 74%) showed highest efficacy. Concerning ≥50% seizure reduction rates, levetiracetam showed highest efficacy at 6 and 12 months (WAs of 82% and 97%, respectively). However, treatment failure rates at 12 months were highest for phenytoin (WA = 34%) and pregabalin (41%). When comparing the described polytherapy combinations with follow-up of ≥6 months, levetiracetam combined with phenytoin was most effective followed by levetiracetam combined with valproic acid.

Conclusion

Given the heterogeneous patient populations and the low scientific quality across the different studies, seizure rates need to be interpreted with caution. Based on the current limited evidence, with the ranking of AEDs being confined to the AEDs studied, levetiracetam, phenytoin, and pregabalin seem to be most effective as AED monotherapy in glioma patients with epilepsy, with levetiracetam showing the lowest treatment failure rate, compared to the other AEDs studied.

Glioma-related epilepsy in patients with diffuse high-grade glioma after the 2016 WHO update: seizure characteristics, risk factors, and clinical outcomes

OBJECTIVE

The aim of this study was to investigate the epidemiological characteristics, associated risk factors, and prognostic value of glioma-related epilepsy in patients with diffuse high-grade gliomas (DHGGs) that were diagnosed after the 2016 updated WHO classification was released.

METHODS

Data from 449 patients with DHGGs were retrospectively collected. Definitive diagnosis was reaffirmed according to the 2016 WHO classification. Seizure outcome was assessed using the Engel classification at 12 months after surgery. Univariate and multivariate analyses were performed to identify risk factors associated with preoperative and postoperative glioma-related epilepsy. Lastly, the prognostic value of glioma-related epilepsy was evaluated by Kaplan-Meier and Cox analysis.

RESULTS

The incidence of glioma-related epilepsy decreased gradually as the malignancy of the tumor increased. Age < 45 years (OR 2.601, p < 0.001), normal neurological function (OR 3.024, p < 0.001), and lower WHO grade (OR 2.028, p = 0.010) were independently associated with preoperative glioma-related epilepsy, while preoperative glioma-related epilepsy (OR 7.554, p < 0.001), temporal lobe involvement (OR 1.954, p = 0.033), non-gross-total resection (OR 2.286, p = 0.012), and lower WHO grade (OR 2.130, p = 0.021) were identified as independent predictors of poor seizure outcome. Furthermore, postoperative glioma-related epilepsy, rather than preoperative glioma-related epilepsy, was demonstrated as an independent prognostic factor for overall survival (OR 0.610, p = 0.010).

CONCLUSIONS

The updated WHO classification seems conducive to reveal the distribution of glioma-related epilepsy in DHGG patients. For DHGG patients with high-risk predictors of poor seizure control, timely antiepileptic interventions could be beneficial. Moreover, glioma-related epilepsy (especially postoperative glioma-related epilepsy) is associated with favorable overall survival.

Molecular Classification of Gliomas is Associated with Seizure Control: A Retrospective Analysis

Classically, histologic grading of gliomas has been used to predict seizure association, with low-grade gliomas associated with an increased incidence of seizures compared to high-grade gliomas. In 2016, WHO reclassified gliomas based on histology and molecular characteristics. We sought to determine whether molecular classification of gliomas is associated with preoperative seizure presentation and/or post-operative seizure control across multiple glioma subtypes. All gliomas operated at our institution from 2007 to 2017 were identified based on ICD 9 and 10 billing codes and were retrospectively assessed for molecular classification of the IDH1 mutation, and 1p/19q codeletion. Logistic regression models were performed to assess associations of seizures at presentation as well as post-operative seizures with IDH status and the new WHO integrated classification. Our study included 376 patients: 82 IDH mutant and 294 IDH wildtype. The presence of IDH mutation was associated with seizures at presentation [OR 3.135 (1.818-5.404), p < 0.001]. IDH-mutant glioblastomas presented with seizures less often than other IDH-mutant glioma subtypes grade II and III [OR 0.104 (0.032-0.340), p < 0.001]. IDH-mutant tumors were associated with worse post-operative seizure outcomes, demonstrated by Engel Class [OR 2.666 (1.592-4.464), p < 0.001]. IDH mutation in gliomas is associated with an increased risk of seizure development and worse post-operative seizure control, in all grades except for GBM.

Low-Grade Glioma Case Series: Lessons Learned from an Evolving 10-Year Single-Institution Multidisciplinary Team Practice

BACKGROUND

Low-grade gliomas are a heterogeneous group with significant changes in their management during the last decade.

OBJECTIVE

To assess how our multidisciplinary team approach to the management of low-grade glioma has evolved over the past 10 years and its implications for outcomes.

METHODS

Retrospective single-center cohort study of adult patients with a pathologically confirmed diagnosis of World Health Organization grade II glioma between 2009 and 2018. Demographic, clinical, and pathologic data were collected.

RESULTS

Ninety-five patients were included. There was a statistically significant difference in the surgical approach, with more patients having gross total resection (45.7% vs. 18.4%) and fewer patients having a biopsy (21.8% vs. 49.0%) (P = 0.002) after 2014. There was a significantly better overall survival after 2014 (<2014, 16.3%; ≥2014, 0 deaths; P = 0.010) measured at the mean time of follow-up. The use of adjuvant chemotherapy (P = 0.045) and radiotherapy (P = 0.001) significantly decreased after 2014. A subgroup analysis showed that the impact of extent of surgical resection was the greatest for survival in the 1p19q noncodeleted tumors (P = 0.029) and for seizure outcomes in the 1p19q codeleted group (P = 0.018). There was no statistically significant increase in neurologic disability with more radical surgery, incorporating intraoperative neuromonitoring, as measured by modified Rankin Scale score (P > 0.05).

CONCLUSIONS

More radical surgery was associated with increased survival, less need for postoperative adjuvant therapy and better seizure control, without significant morbidity. Molecular markers are useful tools for stratification of benefits after such surgery.

Scale-Free Analysis of Intraoperative ECoG During Awake Craniotomy for Glioma

BACKGROUND

Electrocorticography (ECoG) has been utilized in many epilepsy cases however, the use of this technique for evaluating electrophysiological changes within tumoral zones is spare. Nonetheless, epileptic activities seem to arise from the neocortex surrounding the gliomas suggesting a link between epileptogenesis and glioma cell infiltration in the peritumoral area. The purpose of this study was to implement novel scale-free measures to assess how cortical physiology is altered by the presence of an invasive brain tumor.

METHODS

Twelve patients undergoing an awake craniotomy for resection of a supratentorial glioma were included. ECoG data over the main tumor and the exposed surroundings was acquired intra-operatively just prior to tumor resection. Six of the patients presented with seizures and had data acquired both in the awake and anesthetic state. The corresponding anatomical location of each electrode in relation to the macroscopically-detectable tumor was recorded using the neuronavigation system based on structural anatomical images obtained pre-operatively. The electrodes were classified into tumoral, healthy or peritumoral based on the macroscopically detectable tumoral tissue from the pre-operative structural MRI.

RESULTS

The electrodes overlying the tumoral tissue revealed higher power law exponent (PLE) values across tumoral area compared to the surrounding tissues. The difference between the awake and anesthetic states was significant in the tumoral and healthy tissue (p < 0.05) but not in the peritumoral tissue. The absence of a significant PLE reduction in the peritumoral tissue from the anesthetic to the awake state could be considered as an index of the presence or absence of infiltration of tumor cells into the peritumoral tissue.

CONCLUSIONS

The current study portrays for the first time distinct power law exponent features in the tumoral tissue, which could provide a potential novel electrophysiological marker in the future. The distinct features seen in the peritumoral tissue of gliomas seem to indicate the area where both the onset of epileptiform activity and the tumor infiltration take place.

Risk Assessment by Pre-surgical Tractography in Left Hemisphere Low-Grade Gliomas

Background: Tracking the white matter principal tracts is routinely typically included during the pre-surgery planning examinations and has revealed to limit functional resection of low-grade gliomas (LGGs) in eloquent areas.

Objective: We examined the integrity of the Superior Longitudinal Fasciculus (SLF) and Inferior Fronto-Occipital Fasciculus (IFOF), both known to be part of the language-related network in patients with LGGs involving the temporo-insular cortex. In a comparative approach, we contrasted the main quantitative fiber tracking values in the tumoral (T) and healthy (H) hemispheres to test whether or not this ratio could discriminate amongst patients with different post-operative outcomes.

Methods: Twenty-six patients with LGGs were included. We obtained quantitative fiber tracking values in the tumoral and healthy hemispheres and calculated the ratio (H_IFOF–T_IFOF)/H_IFOF and the ratio (H_SLF–T_SLF)/H_SLF on the number of streamlines. We analyzed how these values varied between patients with and without post-operative neurological outcomes and between patients with different post-operative Engel classes.

Results: The ratio for both IFOF and SLF significantly differed between patient with and without post-operative neurological language deficits. No associations were found between white matter structural changes and post-operative seizure outcomes.

Conclusions: Calculating the ratio on the number of streamlines and fractional anisotropy between the tumoral and the healthy hemispheres resulted to be a useful approach, which can prove to be useful during the pre-operative planning examination, as it gives a glimpse on the potential clinical outcomes in patients with LGGs involving the left temporo-insular cortex.

Predictors of early, recurrent, and intractable seizures in low-grade glioma

Background

Seizures are common among patients with low-grade glioma (LGG) and can significantly affect morbidity. We sought to determine the association between the clinical and molecular factors with seizure incidence and refractoriness in LGG patients.

Methods

We conducted a retrospective review at the University of Virginia in patients with LGG (World Health Organization, WHO Grade II) evaluated between 2002 and 2015. Descriptive statistics were calculated for variables of interest, and the Kaplan-Meier method was used to estimate survival curves, which were compared with the log-rank test.

Results

A total of 291 patients were included; 254 had molecular testing performed for presence of an isocitrate dehydrogenase (IDH) mutation and/or 1p/19q codeletion. Sixty-eight percent of patients developed seizures prior to LGG diagnosis; 41% of all patients had intractable seizures. Using WHO 2016 integrated classification, there was no significant difference in seizure frequency during preoperative and postoperative periods or in developing intractable seizures, though a trend toward increased preoperative seizure incidence among patients with the IDH mutation was identified (P = .09). Male sex was significantly associated with higher seizure incidence during preoperative (P < .001) and postoperative periods (P < .001); men were also more likely to develop intractable seizures (P = .01).

Conclusions

Seizures are common among patients with LGG. Differences in preoperative or postoperative and intractable seizure rates by WHO 2016 classification were not detected. Our data showed a trend toward higher seizure incidence preoperatively in patients with IDH-mutant LGG. We describe a unique association between male sex and seizure incidence and intractability that warrants further study.