Single-nucleus and spatial landscape of the sub-ventricular zone in human glioblastoma

The sub-ventricular zone (SVZ) is the most well-characterized neurogenic area in the mammalian brain. We previously showed that in 65% of patients with glioblastoma (GBM), the SVZ is a reservoir of cancer stem-like cells that contribute to treatment resistance and emergence of recurrence. Here, we built a single-nucleus RNA-sequencing-based microenvironment landscape of the tumor mass (T_Mass) and the SVZ (T_SVZ) of 15 GBM patients and 2 histologically normal SVZ (N_SVZ) samples as controls. We identified a mesenchymal signature in the T_SVZ of GBM patients: tumor cells from the T_SVZ relied on the ZEB1 regulatory network, whereas tumor cells in the T_Mass relied on the TEAD1 regulatory network. Moreover, the T_SVZ microenvironment was predominantly characterized by tumor-supportive microglia, which spatially co-exist and establish heterotypic interactions with tumor cells. Lastly, differential gene expression analyses, predictions of ligand-receptor and incoming/outgoing interactions, and functional assays revealed that the IL-1β/IL-1RAcP and Wnt-5a/Frizzled-3 pathways are therapeutic targets in the T_SVZ microenvironment. Our data provide insights into the biology of the SVZ in GBM patients and identify specific targets of this microenvironment.

Forebrain EAAT3 Overexpression Increases Susceptibility to Amphetamine-Induced Repetitive Behaviors

Obsessive-compulsive disorder (OCD) is a debilitating psychiatric disorder characterized by intrusive obsessive thoughts and compulsive behaviors. Multiple studies have shown the association of polymorphisms in the SLC1A1 gene with OCD. The most common of these OCD-associated polymorphisms increases the expression of the encoded protein, excitatory amino acid transporter 3 (EAAT3), a neuronal glutamate transporter. Previous work has shown that increased EAAT3 expression results in OCD-relevant behavioral phenotypes in rodent models. In this study, we created a novel mouse model with targeted, reversible overexpression of Slc1a1 in forebrain neurons. The mice do not have a baseline difference in repetitive behavior but show increased hyperlocomotion following a low dose of amphetamine (3 mg/kg) and increased stereotypy following a high dose of amphetamine (8 mg/kg). We next characterized the effect of amphetamine on striatal cFos response and found that amphetamine increased cFos throughout the striatum in both control and Slc1a1-overexpressing (OE) mice, but Slc1a1-OE mice had increased cFos expression in the ventral striatum relative to controls. We used an unbiased machine classifier to robustly characterize the behavioral response to different doses of amphetamine and found a unique response to amphetamine in Slc1a1-OE mice, relative to controls. Lastly, we found that the differences in striatal cFos expression in Slc1a1-OE mice were driven by cFos expression specifically in D1 neurons, as Slc1a1-OE mice had increased cFos in D1 ventral medial striatal neurons, implicating this region in the exaggerated behavioral response to amphetamine in Slc1a1-OE mice.

Repeated chemogenetic activation of dopaminergic neurons induces reversible changes in baseline and amphetamine-induced behaviors

RATIONALE

Repeated chemogenetic stimulation is often employed to study circuit function and behavior. Chronic or repeated agonist administration can result in homeostatic changes, but this has not been extensively studied with designer receptors exclusively activated by designer drugs (DREADDs).

OBJECTIVES

We sought to evaluate the impact of repeated DREADD activation of dopaminergic (DA) neurons on basal behavior, amphetamine response, and spike firing. We hypothesized that repeated DREADD activation would mimic compensatory effects that we observed with genetic manipulations of DA neurons.

METHODS

Excitatory hM3D(Gq) DREADDs were virally expressed in adult TH-Cre and WT mice. In a longitudinal design, clozapine N-oxide (CNO, 1.0 mg/kg) was administered repeatedly. We evaluated basal and CNO- or amphetamine (AMPH)-induced locomotion and stereotypy. DA neuronal activity was assessed using in vivo single-unit recordings.

RESULTS

Acute CNO administration increased locomotion, but basal locomotion decreased after repeated CNO exposure in TH-CrehM3Dq mice relative to littermate controls. Further, after repeated CNO administration, AMPH-induced hyperlocomotion and stereotypy were diminished in TH-CrehM3Dq mice relative to controls. Repeated CNO administration reduced DA neuronal firing in TH-CrehM3Dq mice relative to controls. A two-month CNO washout period rescued the decreases in basal locomotion and AMPH response.

CONCLUSIONS

We found that repeated DREADD activation of DA neurons evokes homeostatic changes that should be factored into the interpretation of chronic DREADD applications and their impact on circuit function and behavior. These effects are likely to also be seen in other neuronal systems and underscore the importance of studying neuroadaptive changes with chronic or repeated DREADD activation.

A non-canonical striatopallidal Go pathway that supports motor control

In the classical model of the basal ganglia, direct pathway striatal projection neurons (dSPNs) send projections to the substantia nigra (SNr) and entopeduncular nucleus to regulate motor function. Recent studies have re-established that dSPNs also possess axon collaterals within the globus pallidus (GPe) (bridging collaterals), yet the significance of these collaterals for behavior is unknown. Here we use in vivo optical and chemogenetic tools combined with deep learning approaches in mice to dissect the roles of dSPN GPe collaterals in motor function. We find that dSPNs projecting to the SNr send synchronous motor-related information to the GPe via axon collaterals. Inhibition of native activity in dSPN GPe terminals impairs motor activity and function via regulation of Npas1 neurons. We propose a model by which dSPN GPe axon collaterals (striatopallidal Go pathway) act in concert with the canonical terminals in the SNr to support motor control by inhibiting Npas1 neurons.

Dissecting Intra-tumor Heterogeneity in the Glioblastoma Microenvironment Using Fluorescence-Guided Multiple Sampling

The treatment of the most aggressive primary brain tumor in adults, glioblastoma (GBM), is challenging due to its heterogeneous nature, invasive potential, and poor response to chemo- and radiotherapy. As a result, GBM inevitably recurs and only a few patients survive 5 years post-diagnosis. GBM is characterized by extensive phenotypic and genetic heterogeneity, creating a diversified genetic landscape and a network of biological interactions between subclones, ultimately promoting tumor growth and therapeutic resistance. This includes spatial and temporal changes in the tumor microenvironment, which influence cellular and molecular programs in GBM and therapeutic responses. However, dissecting phenotypic and genetic heterogeneity at spatial and temporal levels is extremely challenging, and the dynamics of the GBM microenvironment cannot be captured by analysis of a single tumor sample. In this review, we discuss the current research on GBM heterogeneity, in particular, the utility and potential applications of fluorescence-guided multiple sampling to dissect phenotypic and genetic intra-tumor heterogeneity in the GBM microenvironment, identify tumor and non-tumor cell interactions and novel therapeutic targets in areas that are key for tumor growth and recurrence, and improve the molecular classification of GBM.

A non-canonical striatopallidal "Go" pathway that supports motor control

In the classical model of the basal ganglia, direct pathway striatal projection neurons (dSPNs) send projections to the substantia nigra (SNr) and entopeduncular nucleus to regulate motor function. Recent studies have re-established that dSPNs also possess "bridging" collaterals within the globus pallidus (GPe), yet the significance of these collaterals for behavior is unknown. Here we use in vivo optical and chemogenetic tools combined with deep learning approaches to dissect the roles of bridging collaterals in motor function. We find that dSPNs projecting to the SNr send synchronous motor-related information to the GPe via axon collaterals. Inhibition of native activity in dSPN GPe terminals impairs motor activity and function via regulation of pallidostriatal Npas1 neurons. We propose a model by which dSPN GPe collaterals ("striatopallidal Go pathway") act in concert with the canonical terminals in the SNr to support motor control by inhibiting Npas1 signals going back to the striatum.

Intact amphetamine-induced behavioral sensitization in mice with increased or decreased neuronal glutamate transporter SLC1A1/EAAT3

Repeated amphetamine treatment results in locomotor sensitization, a phenomenon that may relate to the development of psychosis and addiction. Evidence suggests that interactions between dopaminergic and glutamatergic systems are involved in amphetamine sensitization. We previously demonstrated that the neuronal excitatory amino acid transporter (Slc1a1/EAAT3) produces bidirectional, expression-dependent effects on the response to acute amphetamine. Here, using mice with decreased or increased expression of EAAT3, we found that chronic alterations in EAAT3 expression do not significantly impact amphetamine-induced locomotor sensitization. Compensation by other glutamate transporters cannot be ruled out in this important neuroadaptive phenomenon.

Developmental impact of glutamate transporter overexpression on dopaminergic neuron activity and stereotypic behavior

Obsessive-compulsive disorder (OCD) is a disabling condition that often begins in childhood. Genetic studies in OCD have pointed to SLC1A1, which encodes the neuronal glutamate transporter EAAT3, with evidence suggesting that increased expression contributes to risk. In mice, midbrain Slc1a1 expression supports repetitive behavior in response to dopaminergic agonists, aligning with neuroimaging and pharmacologic challenge studies that have implicated the dopaminergic system in OCD. These findings suggest that Slc1a1 may contribute to compulsive behavior through altered dopaminergic transmission; however, this theory has not been mechanistically tested. To examine the developmental impact of Slc1a1 overexpression on compulsive-like behaviors, we, therefore, generated a novel mouse model to perform targeted, reversible overexpression of Slc1a1 in dopaminergic neurons. Mice with life-long overexpression of Slc1a1 showed a significant increase in amphetamine (AMPH)-induced stereotypy and hyperlocomotion. Single-unit recordings demonstrated that Slc1a1 overexpression was associated with increased firing of dopaminergic neurons. Furthermore, dLight1.1 fiber photometry showed that these behavioral abnormalities were associated with increased dorsal striatum dopamine release. In contrast, no impact of overexpression was observed on anxiety-like behaviors or SKF-38393-induced grooming. Importantly, overexpression solely in adulthood failed to recapitulate these behavioral phenotypes, suggesting that overexpression during development is necessary to generate AMPH-induced phenotypes. However, doxycycline-induced reversal of Slc1a1/EAAT3 overexpression in adulthood normalized both the increased dopaminergic firing and AMPH-induced responses. These data indicate that the pathologic effects of Slc1a1/EAAT3 overexpression on dopaminergic neurotransmission and AMPH-induced stereotyped behavior are developmentally mediated, and support normalization of EAAT3 activity as a potential treatment target for basal ganglia-mediated repetitive behaviors.

Negative Pressure Wound Therapy in Facilitating Wound Healing after Surgical Decompression for Metastatic Spine Disease

BACKGROUND

The risk of wound related complications, including surgical site infections (SSIs), in patients undergoing surgery for metastatic spine disease (MSD) is high. Consequently, patients requiring wound revision surgery face delay in resuming oncological care and incur additional hospitalization. Recent reports suggest that negative pressure wound therapy (NPWT) applied on a closed wound at the time of surgery, significantly reduces post-operative wound complications in degenerative spine disease and trauma setting. Here, we report a single institution experience with incisional NPWT in patients undergoing surgery for MSD.

METHODS

We compared rates of wound complications requiring surgical revision in a surgical cohort of patients with or without NPWT from 2015 to 2020. Adult patients with radiographic evidence of MSD with mechanical instability and/or accelerated neurological decline were included in the study. NPWT was applied on a closed wound in the operating room and continued for 5 days or until discharge, whichever occurred first.

RESULTS

A total of 42 patients were included: 28 with NPWT and 14 without. Patient demographics including underlying comorbidities were largely similar. NPWT patients had higher rates of prior radiation to the surgical site (36% vs. 0%, p = 0.017) and longer fusion constructs (6.7 vs. 3.9 levels, p < 0.001). Three patients (21%) from control group and none from NPWT group contracted SSI requiring wound washout (p = 0.032).

CONCLUSIONS

Our data suggests that SSI and wound dehiscence are significantly reduced with the addition of incisional NPWT in in this vulnerable population.

5-Aminolevulinic acid for enhanced surgical visualization of high-grade gliomas: a prospective, multicenter study

OBJECTIVE

Greater extent of resection (EOR) is associated with longer overall survival in patients with high-grade gliomas (HGGs). 5-Aminolevulinic acid (5-ALA) can increase EOR by improving intraoperative visualization of contrast-enhancing tumor during fluorescence-guided surgery (FGS). When administered orally, 5-ALA is converted by glioma cells into protoporphyrin IX (PPIX), which fluoresces under blue 400-nm light. 5-ALA has been available for use in Europe since 2010, but only recently gained FDA approval as an intraoperative imaging agent for HGG tissue. In this first-ever, to the authors' knowledge, multicenter 5-ALA FGS study conducted in the United States, the primary objectives were the following: 1) assess the diagnostic accuracy of 5-ALA-induced PPIX fluorescence for HGG histopathology across diverse centers and surgeons; and 2) assess the safety profile of 5-ALA FGS, with particular attention to neurological morbidity.

METHODS

This single-arm, multicenter, prospective study included adults aged 18-80 years with Karnofsky Performance Status (KPS) score > 60 and an MRI diagnosis of suspected new or recurrent resectable HGG. Intraoperatively, 3-5 samples per tumor were taken and their fluorescence status was recorded by the surgeon. Specimens were submitted for histopathological analysis. Patients were followed for 6 weeks postoperatively for adverse events, changes in the neurological exam, and KPS score. Multivariate analyses were performed of the outcomes of KPS decline, EOR, and residual enhancing tumor volume to identify predictive patient and intraoperative variables.

RESULTS

Sixty-nine patients underwent 5-ALA FGS, providing 275 tumor samples for analysis. PPIX fluorescence had a sensitivity of 96.5%, specificity of 29.4%, positive predictive value (PPV) for HGG histopathology of 95.4%, and diagnostic accuracy of 92.4%. Drug-related adverse events occurred at a rate of 22%. Serious adverse events due to intraoperative neurological injury, which may have resulted from FGS, occurred at a rate of 4.3%. There were 2 deaths unrelated to FGS. Compared to preoperative KPS scores, postoperative KPS scores were significantly lower at 48 hours and 2 weeks but were not different at 6 weeks postoperatively. Complete resection of enhancing tumor occurred in 51.9% of patients. Smaller preoperative tumor volume and use of intraoperative MRI predicted lower residual tumor volume.

CONCLUSIONS

PPIX fluorescence, as judged by the surgeon, has a high sensitivity and PPV for HGG. 5-ALA was well tolerated in terms of drug-related adverse events, and its application by trained surgeons in FGS for HGGs was not associated with any excess neurological morbidity.

Subcortical contributions to higher cognitive function in tumour patients undergoing awake craniotomy

Primary brain tumours often occur near eloquent regions, affecting language, motor and memory capacity, with awake mapping and tailored resection designed to preserve higher cognitive functioning. The effects of such tumours on subcortical structures, including the thalamus and basal ganglia, have been largely unexplored, in spite of the known importance of such structures to higher cognitive functioning. We sought to explore the effects of volume changes of subcortical structures on cognition, in 62 consecutive patients diagnosed with primary brain tumour and cavernous malformations, referred to our neurosurgical practice. We found right caudate to be highly predictive of intelligence, left pallidum of total neuropsychological function and right hippocampus of mood. Our study is the largest of its kind in exploring subcortical substrates of higher cognition in consecutive patients with brain tumours. This research supports prior literature, showing subcortical structures to be related to higher cognitive functioning, particularly measures of memory and executive functioning implicated in fronto-subcortical circuits. Furthermore, involvement of right mesial temporal structures in mood, further strengthens the central role of Papez circuit in emotional quality of cognition. Attention to subcortical integrity is likely to be important in discussing postsurgical cognitive outcome with patients and their families.

Resting state functional connectivity underlying musical creativity

While the behavior of "being musically creative"- improvising, composing, songwriting, etc.-is undoubtedly a complex and highly variable one, recent neuroscientific investigation has offered significant insight into the neural underpinnings of many of the creative processes contributing to such behavior. A previous study from our research group (Bashwiner et al., 2016), which examined two aspects of brain structure as a function of creative musical experience, found significantly increased cortical surface area or subcortical volume in regions of the default-mode network, a motor planning network, and a "limbic" network. The present study sought to determine how these regions coordinate with one another and with other regions of the brain in a large number of participants (n ​= ​218) during a task-neutral period, i.e., during the "resting state." Deriving from the previous study's results a set of eleven regions of interest (ROIs), the present study analyzed the resting-state functional connectivity (RSFC) from each of these seed regions as a function of creative musical experience (assessed via our Musical Creativity Questionnaire). Of the eleven ROIs investigated, nine showed significant correlations with a total of 22 clusters throughout the brain, the most significant being located in bilateral cerebellum, right inferior frontal gyrus, midline thalamus (particularly the mediodorsal nucleus), and medial premotor regions. These results support prior reports (by ourselves and others) implicating regions of the default-mode, executive, and motor-planning networks in musical creativity, while additionally-and somewhat unanticipatedly-including a potentially much larger role for the salience network than has been previously reported in studies of musical creativity.

Deconstructing Neurogenesis, Transplantation and Genome-Editing as Neural Repair Strategies in Brain Disease

Neural repair in injury and disease presents a pressing unmet need in regenerative medicine. Due to the intrinsically reduced ability of the brain to replace lost and damaged neurons, reversing long-term cognitive and functional impairments poses a unique problem. Over the years, advancements in cellular and molecular understanding of neurogenesis mechanisms coupled with sophistication of biotechnology tools have transformed neural repair into a cross-disciplinary field that integrates discoveries from developmental neurobiology, transplantation and tissue engineering to design disease- and patient-specific remedies aimed at boosting either native rehabilitation or delivering exogenous hypoimmunogenic interventions. Advances in deciphering the blueprint of neural ontogenesis and annotation of the human genome has led to the development of targeted therapeutic opportunities that have the potential of treating the most vulnerable patient populations and whose findings from benchside suggest looming clinical translation. This review discusses how findings from studies of adult neurogenesis have informed development of interventions that target endogenous neural regenerative machineries and how advances in biotechnology, including the use of new gene-editing tools, have made possible the development of promising, complex neural transplant-based strategies. Adopting a multi-pronged strategy that is tailored to underlying neural pathology and that encompasses facilitation of endogenous regeneration, correction of patient’s genomic mutations and delivery of transformed neural precursors and mature disease-relevant neuronal populations to replace injured or lost neural tissue remains no longer a fantasy.

Emerging Pharmacologic Targets in Cerebral Cavernous Malformation and Potential Strategies to Alter the Natural History of a Difficult Disease: A Review

Importance

Cerebral cavernous malformations (CCMs) are vascular lesions of the brain that may lead to hemorrhage, seizures, and neurologic deficits. Most are linked to loss-of-function mutations in 1 of 3 genes, namely CCM1 (originally called KRIT1), CCM2 (MGC4607), or CCM3 (PDCD10), that can either occur as sporadic events or are inherited in an autosomal dominant pattern with incomplete penetrance. Familial forms originate from germline mutations, often have multiple intracranial lesions that grow in size and number over time, and cause an earlier and more severe presentation. Despite active preclinical research on a few pharmacologic agents, clinical translation has been slow. Open surgery and, in some cases, stereotactic radiosurgery remain the only effective treatments, but these options are limited by lesion accessibility and are associated with nonnegligible rates of morbidity and mortality.

Observations

We discuss the limits of CCM management and introduce findings from in vitro and in vivo studies that provide insight into CCM pathogenesis and indicate molecular mechanisms as potential therapeutic targets. These studies report dysregulated cellular pathways shared between CCM, cardiovascular diseases, and cancer. They also suggest the potential effectiveness of proper drug repurposing in association with, or as an alternative to, targeted interventions.

Conclusions and Relevance

We propose methods to exploit specific molecular pathways to design patient-tailored therapeutic approaches in CCM, with the aim to alter its natural progression. In this scenario, the lack of effective pharmacologic options remains a critical barrier that poses an unfulfilled and urgent medical need.

Neuroanatomy of creative achievement

Very few studies have investigated neuroanatomical correlates of "everyday" creative achievement in cohorts of normal subjects. In previous research, we first showed that scores on the Creative Achievement Questionnaire (CAQ) were associated with lower cortical thickness within the left lateral orbitofrontal gyrus (LOFG), and increased thickness of the right angular gyrus (AG) (Jung et al., 2010). Newer studies found the CAQ to be associated with decreased volume of the rostral anterior cingulate cortex (ACC), and that artistic and scientific creativity was associated with increased and decreased volumes within the executive control network and salience network (Shi et al., 2017). We desired to replicate and extend our previous study in a larger cohort (N ​= ​248), comprised of subjects studying and working in science, technology, engineering, and math (STEM). Subjects were young (Range ​= ​16-32; Mean age ​= ​21.8; s.d. ​= ​3.5) all of whom were administered the CAQ, from which we derived artistic and scientific creativity factors. All subjects underwent structural MRI on a 3 ​T scanner from which cortical thickness, area, and volume measures were obtained using FreeSurfer. Our results showed mostly cortical thinning in relation to total, scientific, and artistic creative achievement encompassing many regions involved in the cognitive control network (CCN) and default mode network (DMN).

Real-time presurgical resting-state fMRI in patients with brain tumors: Quality control and comparison with task-fMRI and intraoperative mapping

Resting-state functional magnetic resonance imaging (rsfMRI) is a promising task-free functional imaging approach, which may complement or replace task-based fMRI (tfMRI) in patients who have difficulties performing required tasks. However, rsfMRI is highly sensitive to head movement and physiological noise, and validation relative to tfMRI and intraoperative electrocortical mapping is still necessary. In this study, we investigate (a) the feasibility of real-time rsfMRI for presurgical mapping of eloquent networks with monitoring of data quality in patients with brain tumors and (b) rsfMRI localization of eloquent cortex compared with tfMRI and intraoperative electrocortical stimulation (ECS) in retrospective analysis. Five brain tumor patients were studied with rsfMRI and tfMRI on a clinical 3T scanner using MultiBand(8)-echo planar imaging (EPI) with repetition time: 400 ms. Moving-averaged sliding-window correlation analysis with regression of motion parameters and signals from white matter and cerebrospinal fluid was used to map sensorimotor and language resting-state networks. Data quality monitoring enabled rapid optimization of scan protocols, early identification of task noncompliance, and head movement-related false-positive connectivity to determine scan continuation or repetition. Sensorimotor and language resting-state networks were identifiable within 1 min of scan time. The Euclidean distance between ECS and rsfMRI connectivity and task-activation in motor cortex, Broca's, and Wernicke's areas was 5-10 mm, with the exception of discordant rsfMRI and ECS localization of Wernicke's area in one patient due to possible cortical reorganization and/or altered neurovascular coupling. This study demonstrates the potential of real-time high-speed rsfMRI for presurgical mapping of eloquent cortex with real-time data quality control, and clinically acceptable concordance of rsfMRI with tfMRI and ECS localization.

Predictors of Treatment Response and Survival Outcomes in Meningioma Recurrence with Atypical or Anaplastic Histology

BACKGROUND

Recurrence rates for atypical and anaplastic meningiomas range between 9% and 50% after gross total resection and between 36% and 83% after subtotal resection. Optimal treatment of recurrent meningiomas exhibiting atypical/anaplastic histology is complicated because they are often refractory to both surgery and radiation.

OBJECTIVE

To evaluate clinical determinants of recurrence and treatment-specific outcomes in patients with recurrent meningiomas exhibiting atypical/anaplastic histology at our institution.

METHODS

A cohort study was conducted using clinical data of all patients treated for meningiomas with atypical/anaplastic histology at first recurrence between January 1985 and July 2014 at a tertiary cancer center. Predictors of second recurrence were analyzed using competing risks regression models.

RESULTS

Nine hundred eighteen patients with meningioma were screened, of whom 60 (55% female) had recurrent disease with atypical/anaplastic histology at a median age of 58.1 yr at diagnosis. The median follow-up from the time of first recurrence was 36.7 mo, with 32 (53%) patients alive at last follow-up. There was no effect of extent of resection at first recurrence on time to a subsequent recurrence. Inclusion of radiation as primary or adjuvant therapy at first recurrence reduced the risk of progression or subsequent recurrence compared to surgery alone (P = .07).

CONCLUSION

Treatment of recurrent meningiomas with atypical/anaplastic histology remains challenging. Our data, from one of the largest cohorts, suggest better tumor control with the addition of radiation and challenges the importance of extent of resection at first recurrence. A multicenter effort is needed to confirm these findings and propose treatment guidelines.

Accumbens dopamine D2 receptors increase motivation by decreasing inhibitory transmission to the ventral pallidum

Dopamine D2 receptors (D2Rs) in the nucleus accumbens (NAc) regulate motivated behavior, but the underlying neurobiological mechanisms remain unresolved. Here, we show that selective upregulation of D2Rs in the indirect pathway of the adult NAc enhances the willingness to work for food. Mechanistic studies in brain slices reveal that D2R upregulation attenuates inhibitory transmission at two main output projections of the indirect pathway, the classical long-range projections to the ventral pallidum (VP), as well as local collaterals to direct pathway medium spiny neurons. In vivo physiology confirms the reduction in indirect pathway inhibitory transmission to the VP, and inhibition of indirect pathway terminals to VP is sufficient to enhance motivation. In contrast, D2R upregulation in the indirect pathway does not disinhibit neuronal activity of the direct pathway in vivo. These data suggest that D2Rs in ventral striatal projection neurons promote motivation by weakening the canonical output to the ventral pallidum.

Prior malignancies in patients harboring glioblastoma: an institutional case-study of 2164 patients

More patients are surviving long-term following a cancer diagnosis and as such are at risk for second malignancies. As the most common primary brain tumor, glioblastoma (GBM) will not infrequently occur in this population. No study has examined the incidence of prior cancer (PC) in patients harboring GBM. Here we evaluate the epidemiological features, as well as the molecular and clinical characteristics of GBM as a second cancer. Utilizing a web-based cancer data management system at our institution, we identified 2164 patients harboring GBM from 2007 to 2014. We collected baseline demographic, molecular, and clinical data. Univariate analysis was performed to compare the cohort of GBM patients with and without PC diagnosis. Survival differences were analyzed with Kaplan-Meier and log-rank testing. A Cox-proportional hazards model was fit for multivariable analysis. 170 patients (7.9%) harboring GBM had a PC diagnosis. The median interval between diagnoses was 79 months. The most common pathologies were breast (18.8%) and prostate (18.8%) cancer. Patients with a PC were older at the time of GBM diagnosis than those without PC (66 vs. 59 years, p < 0.001) and were more likely to be white (88.2 vs. 72.8%, p < 0.001). Patients with PC were more likely to harbor an EGFR (20 vs. 12.3%, p < 0.001) or MGMT mutation (17.6 vs. 11.6%, p < 0.001). Median survival was 13 months in the PC cohort and 15 months in the cohort without PC (p = NS). Age, KPS, and diagnosis year were the only factors which influenced outcome in multivariable analysis. Patients who develop GBM following a prior malignancy constitute ~8% of patients with GBM. Despite significant molecular differences these two cohorts appear to have a similar overall prognosis and clinical course. Thus, whether or not a patient harbors a malignancy prior to diagnosis of GBM should not exclude him or her from aggressive treatment or for consideration of novel investigational therapies.

Pathway-Specific Dopamine Abnormalities in Schizophrenia

In light of the clinical evidence implicating dopamine in schizophrenia and the prominent hypotheses put forth regarding alterations in dopaminergic transmission in this disease, molecular imaging has been used to examine multiple aspects of the dopaminergic system. We review the imaging methods used and compare the findings across the different molecular targets. Findings have converged to suggest early dysregulation in the striatum, especially in the rostral caudate, manifesting as excess synthesis and release. Recent data showed deficit extending to most cortical regions and even to other extrastriatal subcortical regions not previously considered to be "hypodopaminergic" in schizophrenia. These findings yield a new topography for the dopaminergic dysregulation in schizophrenia. We discuss the dopaminergic innervation within the individual projection fields to provide a topographical map of this dual dysregulation and explore potential cellular and circuit-based mechanisms for brain region-dependent alterations in dopaminergic parameters. This refined knowledge is essential to better guide translational studies and efforts in early drug development.

Intracranial meningioma with vertebral or intraspinal metastasis: report of 2 cases and review of the literature

Extracranial meningioma metastases (EMM) occur in 0.1% of intracranial meningioma patients and are more commonly seen in those with atypical and anaplastic histologies. While the lungs and pleura are the most common site of EMM, intraspinal and vertebral EMM also occur and are not well described in the literature. Although the presence of EMM can worsen prognosis, no standard of care has been established for EMM management.

All patients treated for recurrent atypical/anaplastic meningiomas between January 1985 and July 2014 at Memorial Sloan Kettering Cancer Center were screened for intraspinal and vertebral EMM. Of these patients, 2 were identified as having recurrent meningioma complicated by vertebral or intraspinal EMM. A review of the literature was also conducted. The PubMed database was screened for intraspinal and vertebral EMM cases reported in the literature from 1985 to 2015. Nineteen articles were identified from the literature and included 24 individual cases with a total of 34 vertebral or intraspinal EMM. Forty-two percent (10/24) of patients with vertebral or intraspinal EMM had WHO Grade I tumors. Furthermore, 25% (6/24) of vertebral and intraspinal EMM occurred after the primary tumor but prior to any recurrence.

This paper highlights that vertebral and intraspinal EMM can occur in patients with WHO Grade I meningiomas and can occur before tumor recurrence. This challenges the notion that EMM are seen primarily in high-grade atypical and anaplastic meningiomas.

Interneuron Progenitor Transplantation to Treat CNS Dysfunction

Due to the inadequacy of endogenous repair mechanisms diseases of the nervous system remain a major challenge to scientists and clinicians. Stem cell based therapy is an exciting and viable strategy that has been shown to ameliorate or even reverse symptoms of CNS dysfunction in preclinical animal models. Of particular importance has been the use of GABAergic interneuron progenitors as a therapeutic strategy. Born in the neurogenic niches of the ventral telencephalon, interneuron progenitors retain their unique capacity to disperse, integrate and induce plasticity in adult host circuitries following transplantation. Here we discuss the potential of interneuron based transplantation strategies as it relates to CNS disease therapeutics. We also discuss mechanisms underlying their therapeutic efficacy and some of the challenges that face the field.

Primary melanocytic tumors of the central nervous system: Report of two cases and review of literature

Background:

Primary melanocytic tumors of the central nervous system (CNS) represent only 1% of all melanomas. We report two rare cases of primary diffuse leptomeningeal melanomatosis (PDLM; case 1) and primary melanoma of the thoraco-lumbar spine (case 2).

Case Description:

In case 1, multiple cerebrospinal fluid (CSF) studies and a brain biopsy were non-diagnostic, with a biopsy of the cauda equina eventually demonstrating malignant melanomatosis. Diagnosis of primary spinal cord melanoma was more straightforward in case 2 with imaging and biopsy.

Conclusion:

PDLM and primary intramedullary spinal melanoma are rare variants of primary CNS melanoma. This report contrasts the diagnostic challenges between the two entities and alerts the neurosurgeon into considering the diagnosis with appropriate clinical presentation.

Interneuron precursor transplants in adult hippocampus reverse psychosis-relevant features in a mouse model of hippocampal disinhibition

GABAergic interneuron hypofunction is hypothesized to underlie hippocampal dysfunction in schizophrenia. Here, we use the cyclin D2 knockout (Ccnd2(-/-)) mouse model to test potential links between hippocampal interneuron deficits and psychosis-relevant neurobehavioral phenotypes. Ccnd2(-/-) mice show cortical PV(+) interneuron reductions, prominently in hippocampus, associated with deficits in synaptic inhibition, increased in vivo spike activity of projection neurons, and increased in vivo basal metabolic activity (assessed with fMRI) in hippocampus. Ccnd2(-/-) mice show several neurophysiological and behavioral phenotypes that would be predicted to be produced by hippocampal disinhibition, including increased ventral tegmental area dopamine neuron population activity, behavioral hyperresponsiveness to amphetamine, and impairments in hippocampus-dependent cognition. Remarkably, transplantation of cells from the embryonic medial ganglionic eminence (the major origin of cerebral cortical interneurons) into the adult Ccnd2(-/-) caudoventral hippocampus reverses these psychosis-relevant phenotypes. Surviving neurons from these transplants are 97% GABAergic and widely distributed within the hippocampus. Up to 6 mo after the transplants, in vivo hippocampal metabolic activity is lowered, context-dependent learning and memory is improved, and dopamine neuron activity and the behavioral response to amphetamine are normalized. These findings establish functional links between hippocampal GABA interneuron deficits and psychosis-relevant dopaminergic and cognitive phenotypes, and support a rationale for targeting limbic cortical interneuron function in the prevention and treatment of schizophrenia.

Dopamine D2 receptors regulate the anatomical and functional balance of basal ganglia circuitry

Structural plasticity in the adult brain is essential for adaptive behavior. We have found a remarkable anatomical plasticity in the basal ganglia of adult mice that is regulated by dopamine D2 receptors (D2Rs). By modulating neuronal excitability, striatal D2Rs bidirectionally control the density of direct pathway collaterals in the globus pallidus that bridge the direct pathway with the functionally opposing indirect pathway. An increase in bridging collaterals is associated with enhanced inhibition of pallidal neurons in vivo and disrupted locomotor activation after optogenetic stimulation of the direct pathway. Chronic blockade with haloperidol, an antipsychotic medication used to treat schizophrenia, decreases the extent of bridging collaterals and rescues the locomotor imbalance. These findings identify a role for bridging collaterals in regulating the concerted balance of striatal output and may have important implications for understanding schizophrenia, a disease involving excessive activation of striatal D2Rs that is treated with D2R blockers.

Diagnosis of ventriculoperitoneal shunt infection using [F-18]-FDG PET: a case report

Infection of cerebrospinal fluid (CSF) shunts is a common occurrence and can often be difficult to diagnose using standard analysis of shunt fluid. This article presents the first case report on the diagnosis of a CSF shunt infection on FDG PET scan. A 26-year-old female underwent ventriculoperitoneal shunt placement after developing a pseudomeningocele subsequent to a suboccipital craniectomy for Chiari malformation. Two months later, the patient presented with abdominal pain and non-specific symptoms and was found to have a perisplenic abscess for which she was adequately treated. Failure of her symptoms to solve and an initial negative shunt CSF analysis prompted the search for other sources of infection. An FDG PET scan performed a week later found evidence of increase tracer uptake around the distal tip of the catheter and a repeat shunt CSF analysis showed evidence of CSF infection. FDG PET may be useful in diagnosing shunt related infections in case of high clinical suspicion when standard diagnostic modalities fail to diagnose hardware infection.

Hyperphosphorylation-induced self assembly of murine tau: a comparison with human tau

Alzheimer's disease-like neurofibrillary pathology is neither seen in rodents nor in transgenic animals expressing the disease causing mutant human APP or mutant human presenilins. Whether the absence of this pathology is due to inability of the murine tau to self assemble into filaments or due to some other factors is not understood. In this study, we compared recombinant murine and human taus in their ability to form filaments by AD-like hyperphosphorylation in vitro. Human and murine taus, 0N4R, were generated as recombinant proteins and phosphorylated with rat brain extract as a source of protein kinases. We found that murine tau could be hyperphosphorylated to similar stoichiometry and manner as human tau. Upon hyperphosphorylation, murine tau was able to self polymerize into bundles of paired helical filament- and straight filament-like morphology. The filaments obtained from self assembly of murine tau closely resembled those formed from identically treated human tau. Moreover, like human tau, 60-70% of murine tau aggregated on hyperphosphorylation.