MerTK is a mediator of alpha-synuclein fibril uptake by human microglia.

Mer tyrosine kinase (MerTK) is a receptor tyrosine kinase that mediates non-inflammatory, homeostatic phagocytosis of diverse types of cellular debris. Highly expressed on the surface of microglial cells, MerTK is of importance in brain development, homeostasis, plasticity and disease. Yet, involvement of this receptor in the clearance of protein aggregates that accumulate with ageing and in neurodegenerative diseases has yet to be defined. The current study explored the function of MerTK in the microglial uptake of alpha-synuclein fibrils which play a causative role in the pathobiology of synucleinopathies. Using human primary and induced pluripotent stem cell-derived microglia, the MerTK-dependence of alpha-synuclein fibril internalization was investigated in vitro. Relevance of this pathway in synucleinopathies was assessed through burden analysis of MERTK variants and analysis of MerTK expression in patient-derived cells and tissues. Pharmacological inhibition of MerTK and siRNA-mediated MERTK knockdown both caused a decreased rate of alpha-synuclein fibril internalization by human microglia. Consistent with the non-inflammatory nature of MerTK-mediated phagocytosis, alpha-synuclein fibril internalization was not observed to induce secretion of pro-inflammatory cytokines such as IL-6 or TNF, and downmodulated IL-1ß secretion from microglia. Burden analysis in two independent patient cohorts revealed a significant association between rare functionally deleterious MERTK variants and Parkinson's disease in one of the cohorts (P = 0.002). Despite a small upregulation in MERTK mRNA expression in nigral microglia from Parkinson's disease/Lewy body dementia patients compared to those from non-neurological control donors in a single-nuclei RNA-sequencing dataset (P = 5.08 × 10-21), no significant upregulation in MerTK protein expression was observed in human cortex and substantia nigra lysates from Lewy body dementia patients compared to controls. Taken together, our findings define a novel role for MerTK in mediating the uptake of alpha-synuclein fibrils by human microglia, with possible involvement in limiting alpha-synuclein spread in synucleinopathies such as Parkinson's disease. Upregulation of this pathway in synucleinopathies could have therapeutic values in enhancing alpha-synuclein fibril clearance in the brain.

Delayed recovery from severe refractory intracranial hypertension due to expansion of skin and pericranium stretch after decompressive craniectomy.

PURPOSE: Decompressive craniectomy immediately reduces intracranial pressure by increasing space to accommodate brain volumes. Any delay in reduction of pressure and signs of severe intracranial hypertension requires explanation. CLINICAL FEATURES: We present the case of a 13-yr-old boy presenting with a ruptured arteriovenous malformation resulting in a massive occipito-parietal hematoma and increased intracranial pressure (ICP) refractory to medical management. This patient ultimately underwent a decompressive craniectomy (DC) for alleviation of increased ICP, despite which the patient's hemorrhage continued to worsen to the point of brainstem areflexia suggestive of possible progression to brain death. Within hours of the decompressive craniectomy, the patient displayed a relatively sudden, marked improvement in clinical status, most notably a return in pupillary reactivity and significant decrease in measured ICP. A review of postoperative images after the decompressive craniectomy suggested increases in brain volume that continued beyond the initial postoperative period. CONCLUSION: We urge caution to be taken in the interpretation of the neurologic examination and measured ICP in the context of a decompressive craniectomy. In the patient described in this Case Report, we propose that ongoing expansion of brain volume following a decompressive craniectomy beyond the initial postoperative period, possibly secondary to the stretch of skin or pericranium (used as a dural substitute for expansile duraplasty), can explain further clinical improvements beyond the initial postoperative period. We call for routine serial analyses of brain volumes after decompressive craniectomy to confirm these findings.

RéSUMé: OBJECTIF: La craniectomie décompressive réduit instantanément la pression intracrânienne en augmentant l'espace pour accueillir le volume du cerveau. Tout retard dans la réduction de la pression et tout signe d'hypertension intracrânienne sévère nécessitent une explication. CARACTéRISTIQUES CLINIQUES: Nous décrivons le cas d'un garçon de 13 ans présentant une malformation artérioveineuse rompue entraînant un hématome occipito-pariétal massif et une augmentation de la pression intracrânienne (PIC) réfractaire à une prise en charge médicale. Ce patient a finalement subi une craniectomie décompressive (CD) pour soulager l'augmentation de la PIC, malgré laquelle l'hémorragie du patient a continué à s'aggraver au point d'entraîner une aréflexie du tronc cérébral, suggérant une progression possible vers la mort cérébrale. Quelques heures après la craniectomie décompressive, le patient a présenté une amélioration relativement soudaine et marquée de son état clinique, notamment un retour de la réactivité pupillaire et une diminution significative de la PIC mesurée. Un examen des images postopératoires après la craniectomie décompressive a suggéré une augmentation du volume cérébral qui s'est poursuivie au-delà de la période postopératoire initiale. CONCLUSION: Nous recommandons de faire preuve de prudence dans l'interprétation de l'examen neurologique et de la PIC mesurée dans le contexte d'une craniectomie décompressive. Chez le patient décrit dans cette présentation de cas, nous proposons que l'expansion continue du volume cérébral suite à une craniectomie décompressive au-delà de la période postopératoire initiale, éventuellement secondaire à l'étirement de la peau ou du péricrâne (utilisé comme substitut dural à la duroplastie d'explansion), peut expliquer d'autres améliorations cliniques au-delà de la période postopératoire initiale. Nous recommandons des analyses de routine en série du volume cérébral après une craniectomie décompressive pour confirmer ces résultats.

Comparison of the real-world effectiveness of vertical versus lateral functional hemispherotomy techniques for pediatric drug-resistant epilepsy: A post hoc analysis of the HOPS study.

OBJECTIVE: This study was undertaken to determine whether the vertical parasagittal approach or the lateral peri-insular/peri-Sylvian approach to hemispheric surgery is the superior technique in achieving long-term seizure freedom. METHODS: We conducted a post hoc subgroup analysis of the HOPS (Hemispheric Surgery Outcome Prediction Scale) study, an international, multicenter, retrospective cohort study that identified predictors of seizure freedom through logistic regression modeling. Only patients undergoing vertical parasagittal, lateral peri-insular/peri-Sylvian, or lateral trans-Sylvian hemispherotomy were included in this post hoc analysis. Differences in seizure freedom rates were assessed using a time-to-event method and calculated using the Kaplan-Meier survival method. RESULTS: Data for 672 participants across 23 centers were collected on the specific hemispherotomy approach. Of these, 72 (10.7%) underwent vertical parasagittal hemispherotomy and 600 (89.3%) underwent lateral peri-insular/peri-Sylvian or trans-Sylvian hemispherotomy. Seizure freedom was obtained in 62.4% (95% confidence interval [CI] = 53.5%-70.2%) of the entire cohort at 10-year follow-up. Seizure freedom was 88.8% (95% CI = 78.9%-94.3%) at 1-year follow-up and persisted at 85.5% (95% CI = 74.7%-92.0%) across 5- and 10-year follow-up in the vertical subgroup. In contrast, seizure freedom decreased from 89.2% (95% CI = 86.3%-91.5%) at 1-year to 72.1% (95% CI = 66.9%-76.7%) at 5-year to 57.2% (95% CI = 46.6%-66.4%) at 10-year follow-up for the lateral subgroup. Log-rank test found that vertical hemispherotomy was associated with durable seizure-free progression compared to the lateral approach (p = .01). Patients undergoing the lateral hemispherotomy technique had a shorter time-to-seizure recurrence (hazard ratio = 2.56, 95% CI = 1.08-6.04, p = .03) and increased seizure recurrence odds (odds ratio = 3.67, 95% CI = 1.05-12.86, p = .04) compared to those undergoing the vertical hemispherotomy technique. SIGNIFICANCE: This pilot study demonstrated more durable seizure freedom of the vertical technique compared to lateral hemispherotomy techniques. Further studies, such as prospective expertise-based observational studies or a randomized clinical trial, are required to determine whether a vertical approach to hemispheric surgery provides superior long-term seizure outcomes.

Bilateral Parietal Skull Fractures in Infants Attributable to Accidental Falls.

INTRODUCTION: Multiple skull fractures, including bilateral parietal skull fractures (BPSFs) in infants are considered to be suspicious for abusive head trauma (AHT). The aim of this report is to describe a series of BPSF cases in infants which occurred due to accidental falls. METHODS: We searched our neuroradiology database for BPSF in infants (<1 year old) diagnosed between 2006 and 2019; we reviewed initial presentation, mechanisms of injury, clinical course, head imaging, skeletal survey X-rays, ophthalmology, social work and child abuse physicians (CAP) assessments, and long-term follow-up. "Confirmed accidental BPSF" were strictly defined as having negative skeletal survey and ophthalmology evaluation and a CAP conclusion of accidental injury. RESULTS: Twelve cases of BPSF were found; 3 were confirmed to be accidental, with a mean age at presentation of 3 months. Two infants had single-impact falls, and 1 had a compression injury; all 3 had small intracranial hemorrhages. None had bruises or other injuries, and all remained clinically well. A literature search found 10 similar cases and further biomechanical evidence that these fractures can occur from accidental falls. CONCLUSION: While AHT should be kept in the differential diagnosis whenever BPSFs are seen, these injuries can occur as a result of accidental falls.

MNI SISCOM: an Open-Source Tool for Computing Subtraction Ictal Single-Photon Emission CT Coregistered to MRI.

Subtraction ictal single-photon emission computed tomography (SPECT) coregistered to MRI (SISCOM) is a well-established technique for quantitative analysis of ictal vs interictal SPECT images that can contribute to the identification of the seizure onset zone in patients with drug-resistant epilepsy. However, there is presently a lack of user-friendly free and open-source software to compute SISCOM results from raw SPECT and MRI images. We aimed to develop a simple graphical desktop application for computing SISCOM. MNI SISCOM is a new free and open-source software application for computing SISCOM and producing practical MRI/SPECT/SISCOM image panels for review and reporting. The graphical interface allows any user to quickly and easily obtain SISCOM images with minimal user interaction. Additionally, MNI SISCOM provides command line and Python interfaces for users who would like to integrate these features into their own scripts and pipelines. MNI SISCOM is freely available for download from: https://github.com/jeremymoreau/mnisiscom .

Eight-Year Experience With 3-T Intraoperative MRI Integration in Focal Pediatric Epilepsy Surgery: Impact on Extent of Resection, Residual Volumes, and Seizure Outcomes.

OBJECTIVE. The purpose of this study was to investigate the influence of 3-T intraoperative MRI (ioMRI) on the extent of resection of pediatric focal epileptogenic lesions, residual lesion volumes, and postoperative seizure outcomes. MATERIALS AND METHODS. All surgical procedures for focal epilepsy from 2003 to 2017 were retrospectively reviewed. Patients were divided into two groups: those who underwent ioMRI and those who did not. Each group was subdivided into two subcategories according to preoperative MRI visualization of the lesion: those with well-defined and those with poorly defined lesions. The volumes of preoperative lesions and postoperative residual lesions were delineated. Outcome data and patient characteristics were reviewed. The results were compared between the two groups and the two subcategories. RESULTS. Eighty patients were included: 45 in the ioMRI group (24 with well-defined lesions, 21 with poorly defined lesions) and 35 in the non-ioMRI group (18 with well-defined lesions, 17 with poorly defined lesions). The well-defined lesions included tumors and vascular lesions. The poorly defined lesions included malformations of cortical development, hippocampal sclerosis, and tuberous sclerosis. The mean follow-up duration was 5.1 ± 3.3 years. The rate of gross total resection was not significantly different between the ioMRI and non-ioMRI groups (p = 0.46). However, ioMRI findings facilitated further resection during surgery, increasing gross total resection by an additional 11.1%. The ioMRI group had a significant reduction in percentage of residual volume (p < 0.001). Outcome data suggested that ioMRI is protective against poor Engel score (p = 0.048). Although ioMRI prolonged the mean operative time by 1.2 hours (p = 0.002), the additional time was not associated with additional complications. CONCLUSION. Integration of ioMRI into focal epilepsy surgery was associated with smaller residual lesions and was protective against poor Engel score. It prolonged the operative time but without increasing the number of complications.

Pediatric versus adult meningioma: comparison of epidemiology, treatments, and outcomes using the Surveillance, Epidemiology, and End Results database.

Pediatric meningiomas, which account for < 1% of all meningiomas, are thought to have unique features, including being more aggressive than their adult counterparts. The goal of this investigation was to compare pediatric and adult meningiomas in a large head-to-head comparison. We used the Surveillance, Epidemiology, and End Result (SEER) datasets to compare meningioma demographics, first treatments, and outcomes among children/adolescents (0-21 years), young adults (22-45 years), and older adults (> 45 years). During 2004-2012, SEER contained 59148 patients age 0-107 years diagnosed with meningioma, with children/adolescents accounting for 381 (0.64%) patients. Unlike older and young adults, children/adolescents with meningioma did not demonstrate female predominance, and had an equal 1:1 male-to-female ratio. Children/adolescents also had almost three-times as many spinal tumors (13.1%) than young adults (4.2%) and older adults (4.4%). Both children/adolescents and young adults had undergone more gross total resections (both 43%) versus older adults (25%), and were treated more with radiation (14.6%, and 12.0% respectively) than their older counterparts (8.5%). In addition, both children/adolescents and young adults had significantly lower all-cause mortality (4.5% in both) than older adults (24.6%), during median 35-month follow-up. Inherent limitations of the SEER datasets restrict our ability to answer important questions regarding comparisons of tumor grading, histological diagnosis, cause-specific mortality, and neurofibromatosis status. Pediatric meningiomas appear distinct from their adult counterparts as they do not display the typical female predominance and include more clinically relevant spinal tumors. More extensive surgeries, greater use of radiation therapy, and lower all-cause mortality were seen in both children/adolescents and young adults, which raises questions regarding the perceived uniquely aggressive nature of pediatric meningiomas. However, due to the significant limitations of the SEER datasets, our results must be interpreted cautiously and stand only to foster novel questions, which would be better answered in well-designed, prospective studies.

The Emergence of Zoonotic Onchocerca lupi Infection in the United States--A Case-Series.

This case-series describes the 6 human infections with Onchocerca lupi, a parasite known to infect cats and dogs, that have been identified in the United States since 2013. Unlike cases reported outside the country, the American patients have not had subconjunctival nodules but have manifested more invasive disease (eg, spinal, orbital, and subdermal nodules). Diagnosis remains challenging in the absence of a serologic test. Treatment should be guided by what is done for Onchocerca volvulus as there are no data for O. lupi. Available evidence suggests that there may be transmission in southwestern United States, but the risk of transmission to humans is not known. Research is needed to better define the burden of disease in the United States and develop appropriately-targeted prevention strategies.

3-T intraoperative MRI (iMRI) for pediatric epilepsy surgery.

PURPOSE: Three-tesla intraoperative MRI (iMRI) is a promising tool that could help confirm complete resections and disconnections in pediatric epilepsy surgery, leading to improved outcomes. However, a large proportion of epileptogenic pathologies in children are poorly defined on imaging, which brings into question the utility of iMRI for these cases. Our aim was to compare postoperative seizure outcomes between iMRI- and non-iMRI-based epilepsy surgeries. METHODS: We performed a comparative retrospective analysis of non-iMRI- versus iMRI-based epilepsy surgeries with 2-year follow-up. Patients were stratified into well-defined cases (WDCs), poorly defined cases (PDCs), and diffuse hemispheric cases (DHCs). Primary outcomes were rates of complete seizure freedom and surgical complications. Secondary outcomes included good (Engel class I/II) seizure outcome, extent of resection/disconnection, and operative duration. Regression models were used to adjust for confounding. RESULTS: Thirty-nine iMRI-based and 39 non-iMRI-based surgeries were included. The distributions of age, sex, and lesion class in each era were similar, but the distributions of individual pathologies varied. Seizure freedom and complication rates at 2-year follow-up were not different between the groups, but Engel class I/II outcome was more common in the iMRI group. Extent of resection/disconnection and length of surgery were similar in both groups. PDCs had the worst outcomes, which were unchanged by the use of iMRI. CONCLUSION: Three-tesla iMRI-based epilepsy surgery may have the potential to improve patient outcomes. However, we conclude that iMRI, in its current state of use at our institute, does not improve outcomes for children undergoing epilepsy surgery. Given that its use appears safe, further research on this technology is warranted, particularly for the most challenging PDCs.

Pediatric choroid plexus tumors: epidemiology, treatments, and outcome analysis on 202 children from the SEER database.

Choroid plexus papillomas (CPPs) and carcinomas (CPCs) are rare neoplasms that affect mostly children. Due to their rarity, their epidemiology and outcomes are incompletely understood. The National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program is a well-established population-based group of registries that collects and publishes cancer incidence and survival data representing approximately 28 % of the US population. SEER-STAT v8.1.2 was used to identify patients with ICD-O-3 codes for choroid plexus tumors in patients aged 0-19. Demographics, initial treatment, and follow-up data were collected. Statistical methods including Kaplan-Meier curves, log rank tests, and Cox proportional hazards regression were used to estimate associations between independent variables and survival. The SEER registries contained 107 CPPs (2004-2010) and 95 CPCs (1978-2010). Median follow-up was 38 and 40 months, respectively. More than 75 % of CPCs were diagnosed before the age of 5 years, versus 48 % for CPPs. Sixty-five percent of CPCs and 57 % of CPPs occurred in males. In both groups at least 90 % of children underwent surgical resection. Gross total resection (GTR) was achieved in 67.0 % of CPCs and 63.6 % of CPPs. Almost 17 % of CPCs were treated with radiation versus only 0.9 % of CPPs. More than 98 % of patients with CPP were alive at the last follow-up, versus 62 % of CPC patients. For CPC, surgery was significantly associated with increased overall survival, but contrary to previous reports, extent of surgical resection was not associated with survival. Age, sex, race, and radiation treatment also had no effect on survival. This report, using the SEER datasets, corroborates many findings of previous smaller studies on CPTs. CPC occurs in younger children, with a male predominance, and a much worse prognosis than CPP. As such, these tumors have been treated aggressively with high rates of GTR and radiation treatment. Despite these treatments, overall survival for CPC remains poor.

Utility of genetic testing in the pre-surgical evaluation of children with drug-resistant epilepsy.

We evaluated the utility of genetic testing in the pre-surgical evaluation of pediatric patients with drug-resistant focal epilepsy. This single-center retrospective study reviewed the charts of all pediatric patients referred for epilepsy surgery evaluation over a 5-year period. We extracted and analyzed results of genetic testing as well as clinical, EEG, and neuroimaging data. Of 125 patients referred for epilepsy surgical evaluation, 86 (69%) had some form of genetic testing. Of these, 18 (21%) had a pathogenic or likely pathogenic variant identified. Genes affected included NPRL3 (3 patients, all related), TSC2 (3 patients), KCNH1, CHRNA4, SPTAN1, DEPDC5, SCN2A, ARX, SCN1A, DLG4, and ST5. One patient had ring chromosome 20, one a 7.17p12 duplication, and one a 15q13 deletion. In six patients, suspected epileptogenic lesions were identified on brain MRI that were thought to be unrelated to the genetic finding. A specific medical therapy choice was allowed due to genetic diagnosis in three patients who did not undergo surgery. Obtaining a molecular diagnosis may dramatically alter management in pediatric patients with drug-resistant focal epilepsy. Genetic testing should be incorporated as part of standard investigations in the pre-surgical work-up of pediatric patients with drug-resistant focal epilepsy.

Regulation of stress granule formation in human oligodendrocytes.

Oligodendrocyte (OL) injury and subsequent loss is a pathologic hallmark of multiple sclerosis (MS). Stress granules (SGs) are membrane-less organelles containing mRNAs stalled in translation and considered as participants of the cellular response to stress. Here we show SGs in OLs in active and inactive areas of MS lesions as well as in normal-appearing white matter. In cultures of primary human adult brain derived OLs, metabolic stress conditions induce transient SG formation in these cells. Combining pro-inflammatory cytokines, which alone do not induce SG formation, with metabolic stress results in persistence of SGs. Unlike sodium arsenite, metabolic stress induced SG formation is not blocked by the integrated stress response inhibitor. Glycolytic inhibition also induces persistent SGs indicating the dependence of SG formation and disassembly on the energetic glycolytic properties of human OLs. We conclude that SG persistence in OLs in MS reflects their response to a combination of metabolic stress and pro-inflammatory conditions.

An adapted protocol to derive microglia from stem cells and its application in the study of CSF1R-related disorders.

BACKGROUND: Induced pluripotent stem cell-derived microglia (iMGL) represent an excellent tool in studying microglial function in health and disease. Yet, since differentiation and survival of iMGL are highly reliant on colony-stimulating factor 1 receptor (CSF1R) signaling, it is difficult to use iMGL to study microglial dysfunction associated with pathogenic defects in CSF1R. METHODS: Serial modifications to an existing iMGL protocol were made, including but not limited to changes in growth factor combination to drive microglial differentiation, until successful derivation of microglia-like cells from an adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP) patient carrying a c.2350G > A (p.V784M) CSF1R variant. Using healthy control lines, the quality of the new iMGL protocol was validated through cell yield assessment, measurement of microglia marker expression, transcriptomic comparison to primary microglia, and evaluation of inflammatory and phagocytic activities. Similarly, molecular and functional characterization of the ALSP patient-derived iMGL was carried out in comparison to healthy control iMGL. RESULTS: The newly devised protocol allowed the generation of iMGL with enhanced transcriptomic similarity to cultured primary human microglia and with higher scavenging and inflammatory competence at ~ threefold greater yield compared to the original protocol. Using this protocol, decreased CSF1R autophosphorylation and cell surface expression was observed in iMGL derived from the ALSP patient compared to those derived from healthy controls. Additionally, ALSP patient-derived iMGL presented a migratory defect accompanying a temporal reduction in purinergic receptor P2Y12 (P2RY12) expression, a heightened capacity to internalize myelin, as well as heightened inflammatory response to Pam3CSK4. Poor P2RY12 expression was confirmed to be a consequence of CSF1R haploinsufficiency, as this feature was also observed following CSF1R knockdown or inhibition in mature control iMGL, and in CSF1RWT/KO and CSF1RWT/E633K iMGL compared to their respective isogenic controls. CONCLUSIONS: We optimized a pre-existing iMGL protocol, generating a powerful tool to study microglial involvement in human neurological diseases. Using the optimized protocol, we have generated for the first time iMGL from an ALSP patient carrying a pathogenic CSF1R variant, with preliminary characterization pointing toward functional alterations in migratory, phagocytic and inflammatory activities.

Subtle magnetic resonance imaging differences in tegmental pilocytic astrocytomas as a caution against attempting gross-total resection: illustrative cases.

BACKGROUND: Although surgery within the tegmentum of the midbrain is challenging, resection of tegmental pilocytic astrocytomas (PAs) is a standard treatment because this has been shown to outperform chemotherapy and radiotherapy in terms of long-term tumor control. Gross total resection (GTR) assisted by intraoperative neuroelectrophysiological monitoring can be achieved with a reasonable risk-to-benefit ratio, especially for well-circumscribed tumors, but careful scrutiny of magnetic resonance imaging (MRI) is critical to surgical decision making. The authors present two cases of tegmental PAs, which appeared grossly similar on MRI and were operated on via the same surgical approach using the same intraoperative adjuncts. OBSERVATIONS: The tumors had identical histopathological and molecular diagnoses but drastically different functional outcomes for the patients, with significant long-term complications for one of the children, which the authors believe was due to a slightly more invasive nature of this tumor. The authors demonstrate subtle preoperative MRI findings that might be potential clues to a more infiltrative nature of one PA versus another and present pathological findings supporting this argument. LESSONS: This report serves as a reminder that not all tegmental PAs can be managed by the same surgical approach. Subtle signs of infiltration may indicate that GTR should not be attempted.

Vasospasm following brain tumor resection in children: institutional experience and systematic review.

OBJECTIVE: Delayed cerebral ischemia (DCI) associated with vasospasm is well described in the setting of aneurysmal subarachnoid hemorrhage (SAH). In addition, DCI is very infrequently encountered in patients who have undergone resection of a brain tumor with unclear pathophysiology. The occurrence of DCI in the pediatric population is exceedingly rare, and outcomes in this population have, to the authors' knowledge, never been systematically reviewed. Therefore, the authors present what is to their knowledge the largest series of pediatric patients with this complication and systematically reviewed the literature for individual participant data. METHODS: The authors conducted a retrospective review of 172 sellar and suprasellar tumors in pediatric patients who underwent surgery at the Montreal Children's Hospital between 1999 and 2017 to identify cases of vasospasm occurring after tumor resection. Descriptive statistics, including patient characteristics, intraoperative and postoperative findings, and outcome status, were collected. A systematic review was also conducted using three databases (PubMed, Web of Science, Embase) to identify reported cases available in the literature of vasospasm after tumor resection in children and collect individual participant data on these patients for further analysis. RESULTS: Six patients treated at Montreal Children's Hospital were identified, with an average age of 9.5 years (range 6-15 years). The prevalence of vasospasm after tumor resection was 3.5% (6/172). Vasospasm in all 6 patients occurred after craniotomy was performed to treat a suprasellar tumor. The average interval from surgery to symptoms was 3.25 days (range 12 hours-10 days). The most common tumor etiology was craniopharyngioma, seen in 4 cases. Extensive tumor encasement of blood vessels requiring significant operative manipulation was described in all 6 patients. A rapid decrease in serum sodium (exceeding 12 mEq/L/24 hrs or below 135 mEq/L) was seen in 4 patients. On final follow-up, 3 patients were left with significant disability, and all patients had persistent deficits. A systematic review of the literature revealed a total of 10 other patients whose characteristics and treatment were compared with those of the 6 patients treated at Montreal Children's Hospital. CONCLUSIONS: Vasospasm after tumor resection in children and youth is likely a rare entity, with a prevalence of 3.5% in this case series. Suprasellar tumor location (particularly craniopharyngioma tumor etiology), significant encasement of blood vessels by the tumor, and postoperative hyponatremia may be predictive factors. Outcome is poor, with most patients having significant persistent neurological deficits.

Association of novel mutation in TRPV4 with familial nonsyndromic craniosynostosis with complete penetrance and variable expressivity.

OBJECTIVE: The aim of this study was to characterize a novel pathogenic variant in the transient receptor potential vanilloid 4 (TRPV4) gene, causing familial nonsyndromic craniosynostosis (CS) with complete penetrance and variable expressivity. METHODS: Whole-exome sequencing was performed on germline DNA of a family with nonsyndromic CS to a mean depth coverage of 300× per sample, with greater than 98% of the targeted region covered at least 25×. In this study, the authors detected a novel variant, c.496C>A in TRPV4, exclusively in the four affected family members. The variant was modeled using the structure of the TRPV4 protein from Xenopus tropicalis. In vitro assays in HEK293 cells overexpressing wild-type TRPV4 or TRPV4 p.Leu166Met were used to assess the effect of the mutation on channel activity and downstream MAPK signaling. RESULTS: The authors identified a novel, highly penetrant heterozygous variant in TRPV4 (NM_021625.4:c.496C>A) causing nonsyndromic CS in a mother and all three of her children. This variant results in an amino acid change (p.Leu166Met) in the intracellular ankyrin repeat domain distant from the Ca2+-dependent membrane channel domain. In contrast to other TRPV4 mutations in channelopathies, this variant does not interfere with channel activity as identified by in silico modeling and in vitro overexpression assays in HEK293 cells. CONCLUSIONS: Based on these findings, the authors hypothesized that this novel variant causes CS by modulating the binding of allosteric regulatory factors to TRPV4 rather than directly modifying its channel activity. Overall, this study expands the genetic and functional spectrum of TRPV4 channelopathies and is particularly relevant for the genetic counseling of CS patients.

Surgically Remediable Secondary Network Epileptic Encephalopathies With Continuous Spike Wave in Sleep: Lesions May Not Be Visible on Brain Magnetic Resonance Imaging (MRI).

BACKGROUND: Continuous spike wave in sleep (CSWS) is an electroencephalogram (EEG) pattern associated with developmental and epileptic encephalopathy with spike-and-wave activation in sleep (DEE-SWAS). This etiologically heterogeneous syndrome may occur because of genetic factors and congenital or acquired brain lesions. We studied the pattern of clinical presentation and underlying etiologies in patients with DEE-SWAS that respond to resective surgery. METHODS: We reviewed our clinical and research databases for patients who had resolution of CSWS following surgical resection of a focal lesion. RESULTS: We identified 5 patients meeting inclusion criteria. In 3 of 5, an epileptogenic structural abnormality was not apparent on brain magnetic resonance imaging (MRI). In all 3 patients, focal cortical dysplasia was identified through intracranial EEG monitoring. SIGNIFICANCE: DEE-SWAS may be a secondary bilateral network epilepsy syndrome, which can be treated with resection of the inciting focal lesion. In patients with drug-resistant CSWS, clinicians should consider a complete epilepsy presurgical workup, including intracranial EEG monitoring.

"Generalized-to-focal" epilepsy: stereotactic EEG and high-frequency oscillation patterns

Objective: We aimed to clarify the pathophysiology of epilepsy involving seizures with apparently generalized onset, progressing to focal ictal rhythm through stereotactic EEG (SEEG) implantation, recording, stimulation and high-frequency oscillation (HFO) analysis. Methods: We identified two patients with seizures with bilateral electrographic onset evolving to focal ictal rhythm, who underwent SEEG implantation. Patients had pre-surgical epilepsy work-up, including prolonged video scalp EEG, brain MRI, PET, ictal/interictal SPECT, MEG, and EEG-fMRI prior to SEEG implantation. Results: Both patients had childhood-onset seizures involving behavioural arrest and left versive head and eye deviation, evolving to bilateral tonic-clonic convulsions. Seizures were electrographically preceded by diffuse, bilateral 3-Hz activity resembling absence seizures. Both had suspected focal lesions based on neuroimaging, including 3T MRI and voxel-based post-processing in one patient. Electrode stimulation did not elicit any habitual electroclinical seizures. HFO analysis showed bilateral focal regions with high fast-ripple rates. Significance: "Generalized-to-focal" seizures may occur due to a diffuse, bilateral epileptic network, however, both patients showed ictal evolution from a generalized pattern to a single dominant focus which may explain why the focal aspect of their seizures had a consistent clinical semiology. Patients such as these may have a unique form of generalized epilepsy, but focal/multifocal cerebral abnormalities are also a possibility.

Medulloblastoma and Cowden syndrome: Further evidence of an association.

Cowden syndrome (CS) is an autosomal dominant hamartoma and tumor predisposition syndrome caused by heterozygous pathogenic germline variants in PTEN in most affected individuals. Major features include macrocrania, multiple facial tricholemmomas, acral and oral keratoses and papillomas, as well as mammary, non-medullary thyroid, renal, and endometrial carcinomas. Lhermitte-Duclos disease (LDD), or dysplastic gangliocytoma of the cerebellum, is the typical brain tumor associated with CS; the lifetime risk for LDD in CS patients has been estimated to be as high as 30%. In contrast, medulloblastoma is much rarer in CS, with only 4 reported cases in the literature. We report a 5th such patient. All 5 patients were diagnosed between 1 and 2 years of age and not all showed the pathognomonic clinical stigmata of CS at the time of their medulloblastoma diagnosis. Where detailed information was available, the medulloblastoma was of the SHH-subtype, in keeping with the observation that in sporadic medulloblastomas, PTEN-alterations are usually encountered in the SHH-subtype. Medulloblastomas can be associated with several tumor-predisposition syndromes and of the 4 medulloblastoma subtypes, SHH-medulloblastomas in children have the highest prevalence of predisposing germline variants (approx. 40%). CS should be added to the list of SHH-medulloblastoma-associated syndromes. Germline analysis of PTEN should be performed in infants with SHH-medulloblastomas, regardless of their clinical phenotype, especially if they do not carry pathogenic germline variants in PTEN or PTEN, the most commonly altered predisposing genes in this age-group. In addition, these cases show that CS has a biphasic brain tumor distribution, both in regards to the age of onset and the tumor type: a small number of CS patients develop a medulloblastoma in infancy while many more develop LDD in adulthood.