Advances in Intraoperative Glioma Tissue Sampling and Infiltration Assessment.

Gliomas are infiltrative brain tumors that often involve functional tissue. While maximal safe resection is critical for maximizing survival, this is challenged by the difficult intraoperative discrimination between tumor-infiltrated and normal structures. Surgical expertise is essential for identifying safe margins, and while the intraoperative pathological review of frozen tissue is possible, this is a time-consuming task. Advances in intraoperative stimulation mapping have aided surgeons in identifying functional structures and, as such, has become the gold standard for this purpose. However, intraoperative margin assessment lacks a similar consensus. Nonetheless, recent advances in intraoperative imaging techniques and tissue examination methods have demonstrated promise for the accurate and efficient assessment of tumor infiltration and margin delineation within the operating room, respectively. In this review, we describe these innovative technologies that neurosurgeons should be aware of.

Technical Aspects of Motor and Language Mapping in Glioma Patients.

Gliomas are infiltrative primary brain tumors that often invade functional cortical and subcortical regions, and they mandate individualized brain mapping strategies to avoid postoperative neurological deficits. It is well known that maximal safe resection significantly improves survival, while postoperative deficits minimize the benefits associated with aggressive resections and diminish patients' quality of life. Although non-invasive imaging tools serve as useful adjuncts, intraoperative stimulation mapping (ISM) is the gold standard for identifying functional cortical and subcortical regions and minimizing morbidity during these challenging resections. Current mapping methods rely on the use of low-frequency and high-frequency stimulation, delivered with monopolar or bipolar probes either directly to the cortical surface or to the subcortical white matter structures. Stimulation effects can be monitored through patient responses during awake mapping procedures and/or with motor-evoked and somatosensory-evoked potentials in patients who are asleep. Depending on the patient's preoperative status and tumor location and size, neurosurgeons may choose to employ these mapping methods during awake or asleep craniotomies, both of which have their own benefits and challenges. Regardless of which method is used, the goal of intraoperative stimulation is to identify areas of non-functional tissue that can be safely removed to facilitate an approach trajectory to the equator, or center, of the tumor. Recent technological advances have improved ISM's utility in identifying subcortical structures and minimized the seizure risk associated with cortical stimulation. In this review, we summarize the salient technical aspects of which neurosurgeons should be aware in order to implement intraoperative stimulation mapping effectively and safely during glioma surgery.

Recognizing the psychological impact of a glioma diagnosis on mental and behavioral health: a systematic review of what neurosurgeons need to know.

A cancer diagnosis is life altering and frequently associated with both acute and long-lasting psychosocial and behavioral distress for patients. The impact of a diffuse glioma diagnosis on mental health is an important aspect of the patient experience with their disease. This needs to be understood by neurosurgeons so these concerns can be appropriately addressed in a timely fashion and integrated into the multidisciplinary care of neuro-oncology patients. The relatively grave prognosis associated with diffuse gliomas, the morbidity associated with treatment, and the constant threat of developing a new neurological deficit all can negatively affect a patient's mental ability to cope and ultimately manifest in mental health disorders such as anxiety and depression. The objective of this systematic review was to describe the variety of behavioral health disorders patients may experience following a glioma diagnosis and discuss possible treatment options. The PubMed, Web of Science, Embase, and PsycINFO databases were searched through July 1, 2022, using broad search terms, which resulted in 5028 studies that were uploaded to Covidence systematic review software. Duplicates, non-English-language studies, and studies with irrelevant outcomes or incorrect design were removed (n = 3167). A total of 92 articles reporting behavioral health outcomes in brain tumor patients were categorized and extracted for associations with overall mental health, anxiety, depression, distress, stress, pharmacology, interventions, and mental health in caregivers. The authors identified numerous studies reporting the prevalence of mental health disorders and their negative influence in this population. However, there is a paucity of literature on therapeutic options for patients. Given the strong correlation between patient quality of life and mental well-being, there is a considerable need for early recognition and treatment of these behavioral health disorders to optimize everyday functioning for patients.

LRP1 is a master regulator of tau uptake and spread.

The spread of protein aggregates during disease progression is a common theme underlying many neurodegenerative diseases. The microtubule-associated protein tau has a central role in the pathogenesis of several forms of dementia known as tauopathies-including Alzheimer's disease, frontotemporal dementia and chronic traumatic encephalopathy1. Progression of these diseases is characterized by the sequential spread and deposition of protein aggregates in a predictable pattern that correlates with clinical severity2. This observation and complementary experimental studies3,4 have suggested that tau can spread in a prion-like manner, by passing to naive cells in which it templates misfolding and aggregation. However, although the propagation of tau has been extensively studied, the underlying cellular mechanisms remain poorly understood. Here we show that the low-density lipoprotein receptor-related protein 1 (LRP1) controls the endocytosis of tau and its subsequent spread. Knockdown of LRP1 significantly reduced tau uptake in H4 neuroglioma cells and in induced pluripotent stem cell-derived neurons. The interaction between tau and LRP1 is mediated by lysine residues in the microtubule-binding repeat region of tau. Furthermore, downregulation of LRP1 in an in vivo mouse model of tau spread was found to effectively reduce the propagation of tau between neurons. Our results identify LRP1 as a key regulator of tau spread in the brain, and therefore a potential target for the treatment of diseases that involve tau spread and aggregation.

A farnesyltransferase inhibitor activates lysosomes and reduces tau pathology in mice with tauopathy.

Tau inclusions are a shared feature of many neurodegenerative diseases, among them frontotemporal dementia caused by tau mutations. Treatment approaches for these conditions include targeting posttranslational modifications of tau proteins, maintaining a steady-state amount of tau, and preventing its tendency to aggregate. We discovered a new regulatory pathway for tau degradation that operates through the farnesylated protein, Rhes, a GTPase in the Ras family. Here, we show that treatment with the farnesyltransferase inhibitor lonafarnib reduced Rhes and decreased brain atrophy, tau inclusions, tau sumoylation, and tau ubiquitination in the rTg4510 mouse model of tauopathy. In addition, lonafarnib treatment attenuated behavioral abnormalities in rTg4510 mice and reduced microgliosis in mouse brain. Direct reduction of Rhes in the rTg4510 mouse by siRNA reproduced the results observed with lonafarnib treatment. The mechanism of lonafarnib action mediated by Rhes to reduce tau pathology was shown to operate through activation of lysosomes. We finally showed in mouse brain and in human induced pluripotent stem cell-derived neurons a normal developmental increase in Rhes that was initially suppressed by tau mutations. The known safety of lonafarnib revealed in human clinical trials for cancer suggests that this drug could be repurposed for treating tauopathies.