Stereo-electroencephalography evidence of an eccentrically located seizure-onset zone around a polymorphous low-grade neuroepithelial tumor of the young: illustrative case

Systematic review and cumulative analysis of clinical properties of BRAF V600E mutations in PLNTY histological samples

PURPOSE

Polymorphous low-grade neuroepithelial tumors of the young (PLNTY) represent a rare pediatric-type tumor that most commonly presents as medically refractory epilepsy. PLNTY has only recently been recognized as a distinct clinical entity, having been first described in 2016 and added to the World Health Organization classification of CNS tumors in 2021. Molecular studies have determined that PLNTY is uniformly driven by aberrant MAPK pathway activation, with most tumors carrying either a BRAF V600E mutation or activating FGFR2 or FGFR3 fusion protein. Although it is known that these driver mutations are mutually exclusive, little is known about differences in clinical presentation or treatment outcomes between PLNTY cases driven by these distinct mutations.

METHODS

We performed a systematic review and cumulative analysis of PLNTY cases to assess whether or not PLNTY tumors carrying the BRAF V600E mutation exhibit different clinical behaviors. By searching the literature for all cases of PLNTY wherein BRAF V600E status was characterized, we compiled a dataset of 62 unique patient instances. Using a logistic regression-based approach, we assessed a primary outcome of what factors of a clinical presentation were associated with BRAF V600E mutations and a secondary outcome of what factors predicted total seizure freedom post-surgical resection.

RESULTS

PLNTY cases carrying BRAF V600E mutations in the literature were strongly positively associated with adult patients (p = 0.0055, OR = 6.556; 95% Conf. Int. = 1.737-24.742). BRAF V600E status was also positively associated with tumor involvement of the temporal lobe (p = 0.0046, OR = 11.036; 95% Conf. Int. = 2.100-58.006). Male sex was also positively associated with BRAF V600E status, but the result did not quite achieve statistical significance (p = 0.0731). BRAF V600E status was not found to be associated with post-operative seizure freedom.

CONCLUSIONS

These findings indicate that BRAF V600E-positive PLNTY exhibit characteristic clinical presentations but are not necessarily different in treatment responsiveness. Non-BRAF V600E tumors are more commonly associated with young patients.

Clinical characteristics and surgical outcomes of low-grade epilepsy-associated brain tumors

Background

Low-grade epilepsy-associated brain tumors (LEATs) are found to be the second most common lesion-related epilepsy. Malignant potential of LEATs is very low and the overall survival is good, so the focus of treatment is focused more on seizure outcome rather than oncological prognosis.

Objectives

This study was conducted to evaluate the risk factors of seizure outcomes after resection in patients with LEATs.

Design

A retrospective study.

Methods

A retrospective analysis of patients with LEATs who underwent resective surgery in our three epilepsy centers between October 2010 and April 2023 with a minimum follow-up of 1 year. Demography, clinical characters, neurophysiology, and molecular neuropathology were assessed for association with postoperative seizure outcomes at 1-, 2-, and 5-year follow-up. Synthetic minority oversampling technique (SMOTE) algorithm model was performed to handle the imbalance of data distribution. Gaussian Naïve Bayes (GNB) algorithms were created as a basis for classifying outcomes according to observation indicators.

Results

A total of 111 patients were enrolled in the cohort. The most common pathology was ganglioglioma (n = 37, 33.3%). The percentage of patients with seizure freedom was 91.0% (101/111) at 1-year follow-up, 87.5% (77/88) at 2-year follow-up, and 79.1% (53/67) at 5-year follow-up. Partial resection had a significantly poor seizure outcome compared to total resection and supratotal resection (p < 0.05). The epileptiform discharge on post-resective intraoperative electrocorticography (ECoG) or postoperative scalp electroencephalography (EEG) were negative factors on postoperative seizure freedom at 1-, 2-, or 5-year follow-ups (p < 0.05). The area under the receiver-operating characteristic curve value of the GNB-SMOTE model was 0.95 (95% CI, 0.876-1.000), 0.892 (95% CI, 0.656-0.934), and 0.786 (95% CI, 0.491-0.937) at 1-, 2-, and 5-year follow-up, respectively.

Conclusion

The partial resection, post-resective intraoperative ECoG, and postoperative scalp EEG were valuable indicators of poor seizure outcomes. The utilization of post-resective intraoperative ECoG is beneficial to improve seizure outcomes. Based on the data diversity and completeness of three medical centers, a multivariate correlation analysis model was established based on GNB algorithm.

Clinical significance of molecular subgroups of polymorphous low-grade neuroepithelial tumor of the young (PLNTY): A small single institutional case series and integrated analysis

INTRODUCTION

Polymorphous low-grade neuroepithelial tumor of the young (PLNTY) is a recently described entity. The clinicopathological features and prognosis of the molecular subgroups of these rare tumors is poorly understood. In this study, we presented a small case series of three new cases and integrated the data with published cases in the literature to characterize the similarities and differences of molecular subgroups of PLNTY.

METHODS

We searched our institutional archive for PLNTY cases and searched PubMed and Web of Science for relevant data. Demographic, clinical, radiologic, histopathological, molecular, and follow-up data of our four cases with published cases were integrated for final analyses.

RESULTS

We identified three institutional cases of PLNTY. The median age of our patients was 17 years (range: 13-42). All patients had a prior history of chronic seizures and all had tumors affecting the temporal lobes. Histopathologically, all cases showed oligodendroglial-like morphology with intratumoral calcifications and at least partially infiltrative growth patterns. Tumor cells were immunoreactive with CD34 and GFAP. Genetically, all cases harbored BRAF V600E mutations. Integrated analyses, including a total of 67 cases, demonstrated that PLNTYs with FGFR2 mutation were significantly younger (median age 11.0 years) than those with BRAF V600E or FGFR3 fusions (median age 41.0 and 16.0 years, respectively). All BRAF V600E-positive PLNTYs were free of tumor recurrence, while four of PLNTYs in other molecular subgroups developed tumor recurrence by imaging.

CONCLUSION

Our study suggests that PLNTYs have distinct clinicopathological features and are driven by genetic alterations in the MAPK pathway. The molecular subgroups of PLNTYs share similar findings, but also demonstrate distinct patient demographics.

Large-scale brain networks and intra-axial tumor surgery: a narrative review of functional mapping techniques, critical needs, and scientific opportunities

In recent years, a paradigm shift in neuroscience has been occurring from "localizationism," or the idea that the brain is organized into separately functioning modules, toward "connectomics," or the idea that interconnected nodes form networks as the underlying substrates of behavior and thought. Accordingly, our understanding of mechanisms of neurological function, dysfunction, and recovery has evolved to include connections, disconnections, and reconnections. Brain tumors provide a unique opportunity to probe large-scale neural networks with focal and sometimes reversible lesions, allowing neuroscientists the unique opportunity to directly test newly formed hypotheses about underlying brain structural-functional relationships and network properties. Moreover, if a more complete model of neurological dysfunction is to be defined as a "disconnectome," potential avenues for recovery might be mapped through a "reconnectome." Such insight may open the door to novel therapeutic approaches where previous attempts have failed. In this review, we briefly delve into the most clinically relevant neural networks and brain mapping techniques, and we examine how they are being applied to modern neurosurgical brain tumor practices. We then explore how brain tumors might teach us more about mechanisms of global brain dysfunction and recovery through pre- and postoperative longitudinal connectomic and behavioral analyses.