Intrinsic and secondary epileptogenicity in focal cortical dysplasia type II.

OBJECTIVE: Favorable seizure outcome is reported following resection of bottom-of-sulcus dysplasia (BOSD). We assessed the distribution of epileptogenicity and dysplasia in and around BOSD to better understand this clinical outcome and the optimal surgical approach. METHODS: We studied 27 children and adolescents with magnetic resonance imaging (MRI)-positive BOSD who underwent epilepsy surgery; 85% became seizure-free postresection (median = 5.0 years follow-up). All patients had resection of the dysplastic sulcus, and 11 had additional resection of the gyral crown (GC) or adjacent gyri (AG). Markers of epileptogenicity were relative cortical hypometabolism on preoperative 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET), and spiking, ripples, fast ripples, spike-high-frequency oscillation cross-rate, and phase amplitude coupling (PAC) on preresection and postresection electrocorticography (ECoG), all analyzed at the bottom-of-sulcus (BOS), top-of-sulcus (TOS), GC, and AG. Markers of dysplasia were increased cortical thickness on preoperative MRI, and dysmorphic neuron density and variant allele frequency of somatic MTOR mutations in resected tissue, analyzed at similar locations. RESULTS: Relative cortical metabolism was significantly reduced and ECoG markers were significantly increased at the BOS compared to other regions. Apart from spiking and PAC, which were greater at the TOS compared to the GC, there were no significant differences in PET and other ECoG markers between the TOS, GC, and AG, suggesting a cutoff of epileptogenicity at the TOS rather than a tapering gradient on the cortical surface. MRI and tissue markers of dysplasia were all maximal in the BOS, reduced in the TOS, and mostly absent in the GC. Spiking and PAC reduced significantly over the GC after resection of the dysplastic sulcus. SIGNIFICANCE: These findings support the concept that dysplasia and intrinsic epileptogenicity are mostly limited to the dysplastic sulcus in BOSD and support resection or ablation confined to the MRI-visible lesion as a first-line surgical approach. 18 F-FDG PET and ECoG abnormalities in surrounding cortex seem to be secondary phenomena.

Diagnostic and Management Considerations in Pediatric Dermatofibrosarcoma Protuberans.

BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is a rare fibrohistiocytic tumor of dermal origin. Six percent of all cases present in children, with a childhood incidence of 1 per million. METHODS: This is a retrospective review of all cases of pediatric DFSP managed at a single institution over a 23-year period. RESULTS: Seventeen patients (10 male; mean age, 9.9 years) were managed during the study period. The median follow-up was 29 months. All patients had surgical excision. Three patients required further excision to achieve uninvolved final margins. There were no recurrences observed. CONCLUSIONS: Pediatric DFSP should be managed by a soft tissue tumor multidisciplinary team, with experienced pathologists and reconstructive surgeons. Where R0 resections are obtained, patients can experience recurrence-free survival.

Emergent decision-making behaviour and rhythm generation in a computational model of the ventromedial nucleus of the hypothalamus.

The ventromedial nucleus of the hypothalamus (VMN) has an important role in diverse behaviours. The common involvement in these of sex steroids, nutritionally-related signals, and emotional inputs from other brain areas, suggests that, at any given time, its output is in one of a discrete number of possible states corresponding to discrete motivational drives. Here we explored how networks of VMN neurons might generate such a decision-making architecture. We began with minimalist assumptions about the intrinsic properties of VMN neurons inferred from electrophysiological recordings of these neurons in rats in vivo, using an integrate-and-fire based model modified to simulate activity-dependent post-spike changes in neuronal excitability. We used a genetic algorithm based method to fit model parameters to the statistical features of spike patterning in each cell. The spike patterns in both recorded cells and model cells were assessed by analysis of interspike interval distributions and of the index of dispersion of firing rate over different binwidths. Simpler patterned cells could be closely matched by single neuron models incorporating a hyperpolarising afterpotential and either a slow afterhyperpolarisation or a depolarising afterpotential, but many others could not. We then constructed network models with the challenge of explaining the more complex patterns. We assumed that neurons of a given type (with heterogeneity introduced by independently random patterns of external input) were mutually interconnected at random by excitatory synaptic connections (with a variable delay and a random chance of failure). Simple network models of one or two cell types were able to explain the more complex patterns. We then explored the information processing features of such networks that might be relevant for a decision-making network. We concluded that rhythm generation (in the slow theta range) and bistability arise as emergent properties of networks of heterogeneous VMN neurons.

The spiking and secretory activity of oxytocin neurones in response to osmotic stimulation: a computational model.

KEY POINTS: A quantitative model of oxytocin neurones that combines a spiking model, a model of stimulus-secretion coupling and a model of plasma clearance of oxytocin was tested. To test the model, a variety of sources of published data were used that relate either the electrical activity of oxytocin cells or the secretion of oxytocin to experimentally induced changes in plasma osmotic pressure. To use these data to test the model, the experimental challenges involved were computationally simulated. The model predictions closely matched the reported outcomes of the different experiments. ABSTRACT: Magnocellular vasopressin and oxytocin neurones in the rat hypothalamus project to the posterior pituitary, where they secrete their products into the bloodstream. In rodents, both vasopressin and oxytocin magnocellular neurones are osmoresponsive, and their increased spiking activity is mainly a consequence of an increased synaptic input from osmoresponsive neurons in regions adjacent to the anterior wall of the third ventricle. Osmotically stimulated vasopressin secretion promotes antidiuresis while oxytocin secretion promotes natriuresis. In this work we tested a previously published computational model of the spiking and secretion activity of oxytocin cells against published evidence of changes in spiking activity and plasma oxytocin concentration in response to different osmotic challenges. We show that integrating this oxytocin model with a simple model of the osmoresponsive inputs to oxytocin cells achieves a strikingly close match to diverse sources of data. Comparing model predictions with published data using bicuculline to block inhibitory GABA inputs supports the conclusion that inhibitory inputs and excitatory inputs are co-activated by osmotic stimuli. Finally, we studied how the gain of osmotically stimulated oxytocin release changes in the presence of a hypovolaemic stimulus, showing that this is best explained by an inhibition of an osmotically regulated inhibitory drive to the magnocellular neurones.

Isolated proteinuria due to CUBN homozygous mutation - challenging the investigative paradigm.

BACKGROUND: Proteinuria is a common clinical presentation, the diagnostic workup for which involves many non-invasive and invasive investigations. We report on two siblings that highlight the clinically relevant functional role of cubulin for albumin resorption in the proximal tubule and supports the use of genomic sequencing early in the diagnostic work up of patients who present with proteinuria. CASE PRESENTATION: An 8-year-old boy was referred with an incidental finding of proteinuria. All preliminary investigations were unremarkable. Further assessment revealed consanguineous family history and a brother with isolated proteinuria. Renal biopsy demonstrated normal light microscopy and global glomerular basement membrane thinning on electron microscopy. Chromosomal microarray revealed long continuous stretches of homozygosity (LCSH) representing ~ 4.5% of the genome. Shared regions of LCSH between the brothers were identified and their further research genomic analysis implicated a homozygous stop-gain variant in CUBN (10p12.31). CONCLUSIONS: CUBN mutations have been implicated as a hereditary cause of megaloblastic anaemia and variable proteinuria. This is the second reported family with isolated proteinuria due to biallelic CUBN variants in the absence of megaloblastic anaemia, demonstrating the ability of genomic testing to identify genetic causes of nephropathy within expanding associated phenotypic spectra. Genomic sequencing, undertaken earlier in the diagnostic trajectory, may reduce the need for invasive investigations and the time to definitive diagnosis for patients and families.

Familial cortical dysplasia caused by mutation in the mammalian target of rapamycin regulator NPRL3.

We describe first cousin sibling pairs with focal epilepsy, one of each pair having focal cortical dysplasia (FCD) IIa. Linkage analysis and whole-exome sequencing identified a heterozygous germline frameshift mutation in the gene encoding nitrogen permease regulator-like 3 (NPRL3). NPRL3 is a component of GAP Activity Towards Rags 1, a negative regulator of the mammalian target of rapamycin complex 1 signaling pathway. Immunostaining of resected brain tissue demonstrated mammalian target of rapamycin activation. Screening of 52 unrelated individuals with FCD identified 2 additional patients with FCDIIa and germline NPRL3 mutations. Similar to DEPDC5, NPRL3 mutations may be considered as causal variants in patients with FCD or magnetic resonance imaging-negative focal epilepsy.

Germline and somatic FGFR1 abnormalities in dysembryoplastic neuroepithelial tumors.

Dysembryoplastic neuroepithelial tumor (DNET) is a benign brain tumor associated with intractable drug-resistant epilepsy. In order to identify underlying genetic alterations and molecular mechanisms, we examined three family members affected by multinodular DNETs as well as 100 sporadic tumors from 96 patients, which had been referred to us as DNETs. We performed whole-exome sequencing on 46 tumors and targeted sequencing for hotspot FGFR1 mutations and BRAF p.V600E was used on the remaining samples. FISH, copy number variation assays and Sanger sequencing were used to validate the findings. By whole-exome sequencing of the familial cases, we identified a novel germline FGFR1 mutation, p.R661P. Somatic activating FGFR1 mutations (p.N546K or p.K656E) were observed in the tumor samples and further evidence for functional relevance was obtained by in silico modeling. The FGFR1 p.K656E mutation was confirmed to be in cis with the germline p.R661P variant. In 43 sporadic cases, in which the diagnosis of DNET could be confirmed on central blinded neuropathology review, FGFR1 alterations were also frequent and mainly comprised intragenic tyrosine kinase FGFR1 duplication and multiple mutants in cis (25/43; 58.1 %) while BRAF p.V600E alterations were absent (0/43). In contrast, in 53 cases, in which the diagnosis of DNET was not confirmed, FGFR1 alterations were less common (10/53; 19 %; p < 0.0001) and hotspot BRAF p.V600E (12/53; 22.6 %) (p < 0.001) prevailed. We observed overexpression of phospho-ERK in FGFR1 p.R661P and p.N546K mutant expressing HEK293 cells as well as FGFR1 mutated tumor samples, supporting enhanced MAP kinase pathway activation under these conditions. In conclusion, constitutional and somatic FGFR1 alterations and MAP kinase pathway activation are key events in the pathogenesis of DNET. These findings point the way towards existing targeted therapies.

Disseminated glioneuronal tumors occurring in childhood: treatment outcomes and BRAF alterations including V600E mutation.

Disseminated glioneuronal tumors of childhood are rare. We present a retrospective IRB-approved review of the clinical course and frequency of BRAF mutations in disseminated glioneuronal tumors at two institutions. Defining features of our cohort include diffuse leptomeningeal-spread, often with a discrete spinal cord nodule and oligodendroglioma-like histologic features. Patients were identified through a pathology database search of all cases with disseminated low-grade neoplasms with an oligodendroglioma-like component. De-identified clinical information was collected by chart review and all imaging was reviewed. We retrieved the results of targeted genomic analyses for alterations in BRAF. Ten patients (aged 2-14 years) were identified from the Dana-Farber/Boston Children's Hospital and the Royal Children's Hospital, Melbourne pathology databases. Nine patients received chemotherapy. Eight patients are alive, although three have had episodes of progressive disease. We identified genomic alterations affecting the MAPK pathway in six patients. One patient had a germline RAF1 mutation and a clinical diagnosis of cardio-facio-cutaneous syndrome. BRAF duplications were identified in four and BRAF V600E mutation was identified in one. These data support the presence of targetable genomic alterations in this disease.

Pediatric Pleomorphic Xanthoastrocytoma Treated With Surgical Resection Alone: Clinicopathologic Features.

Pleomorphic xanthoastrocytoma (PXA) is a rare brain tumor that usually occurs in children and young adults. It has characteristic histologic features and is regarded as a WHO grade II lesion. Overall survival is reported to be >60%, but published series usually consist of a range of ages and treatment modalities. Gross total resection is associated with superior survival but recurrence rates after gross total resection are not well described, particularly in a pediatric population. We describe 16 cases over 20 years at our institution of pediatric PXA treated with surgical resection alone with a 5-year relapse-free survival of 40% (95% confidence interval, 20%-82%) and overall survival of 76% (95% confidence interval, 55%-100%). Gross total resection was associated with superior relapse-free survival (P<0.05). Some cases have a very long period between symptom onset or radiologic detection and resection, but neither length of symptoms nor radiologic signs of slow growth were associated with survival. PXA is a rare and unusual entity with unpredictable behavior. Complete surgical resection is optimal but does not guarantee relapse-free survival. We propose separation of PXA from other low-grade gliomas in childhood given differing biology and behavior.

Evidence of broad-based family support for the use of archival childhood tumour samples in future research.

OBJECTIVES: This study aimed to determine the ability to successfully contact past paediatric patients and their families to request participation in research, to assess familial views on the use of previously collected archival clinical samples for research purposes, and to highlight the ethical and practical issues in obtaining this type of retrospective consent. METHODS: To assess familial views on the use of such samples for research, we contacted a cohort of families with children previously diagnosed with a brain tumour to ask for consent to an epigenetic/genetic study. Examining participants' responses allowed us to gauge their opinions on the use of such tissue for research, and whether they would like to receive genetic information uncovered during research. RESULTS: We were able to successfully contact 107 out of 178 families and found a significant positive correlation between year of diagnosis and ability to make contact. Of those families contactable that returned a consent form (75/107), 74 agreed to the use of their/their child's archival tissue in future research, and 70 of 74 requested notification should a gene change of potential clinical relevance be found. There were no differences in opinion between parents of living or deceased children or the patients themselves. CONCLUSIONS: This study highlights the importance of time since diagnosis on the ability to make contact with previous patients and their families. When contactable, our data highlight the altruistic views of families towards the use of archival clinical samples for research purposes, irrespective of the outcome of their child's illness.

Complicated Henoch-Schönlein purpura.

We present a case of Henoch Schonlein pupura in a 6-year-old boy demonstrating some of the diagnostic pitfalls, complications and management challenges of this common paediatric condition.

Spike triggered hormone secretion in vasopressin cells; a model investigation of mechanism and heterogeneous population function.

Vasopressin neurons generate distinctive phasic patterned spike activity in response to elevated extracellular osmotic pressure. These spikes are generated in the cell body and are conducted down the axon to the axonal terminals where they trigger Ca²âº entry and subsequent exocytosis of hormone-containing vesicles and secretion of vasopressin. This mechanism is highly non-linear, subject to both frequency facilitation and fatigue, such that the rate of secretion depends on both the rate and patterning of the spike activity. Here we used computational modelling to investigate this relationship and how it shapes the overall response of the neuronal population. We generated a concise single compartment model of the secretion mechanism, fitted to experimentally observed profiles of facilitation and fatigue, and based on representations of the hypothesised underlying mechanisms. These mechanisms include spike broadening, Ca²âº channel inactivation, a Ca²âº sensitive K⁺ current, and releasable and reserve pools of vesicles. We coupled the secretion model to an existing integrate-and-fire based spiking model in order to study the secretion response to increasing synaptic input, and compared phasic and non-phasic spiking models to assess the functional value of the phasic spiking pattern. The secretory response of individual phasic cells is very non-linear, but the response of a heterogeneous population of phasic cells shows a much more linear response to increasing input, matching the linear response we observe experimentally, though in this respect, phasic cells have no apparent advantage over non-phasic cells. Another challenge for the cells is maintaining this linear response during chronic stimulation, and we show that the activity-dependent fatigue mechanism has a potentially useful function in helping to maintain secretion despite depletion of stores. Without this mechanism, secretion in response to a steady stimulus declines as the stored content declines.

TEN-like eruption in setting of EBV positive T-cell lymphoproliferative disease with HLH, in a child.

Haemophagocytic lymphohistiocytosis complicating Epstein-Barr virus positive T-cell lymphoproliferative disease of childhood is a rare and life-threatening entity. We report a child with this condition presenting with a toxic epidermal necrolysis-like eruption.

Phasic firing in vasopressin cells: understanding its functional significance through computational models.

Vasopressin neurons, responding to input generated by osmotic pressure, use an intrinsic mechanism to shift from slow irregular firing to a distinct phasic pattern, consisting of long bursts and silences lasting tens of seconds. With increased input, bursts lengthen, eventually shifting to continuous firing. The phasic activity remains asynchronous across the cells and is not reflected in the population output signal. Here we have used a computational vasopressin neuron model to investigate the functional significance of the phasic firing pattern. We generated a concise model of the synaptic input driven spike firing mechanism that gives a close quantitative match to vasopressin neuron spike activity recorded in vivo, tested against endogenous activity and experimental interventions. The integrate-and-fire based model provides a simple physiological explanation of the phasic firing mechanism involving an activity-dependent slow depolarising afterpotential (DAP) generated by a calcium-inactivated potassium leak current. This is modulated by the slower, opposing, action of activity-dependent dendritic dynorphin release, which inactivates the DAP, the opposing effects generating successive periods of bursting and silence. Model cells are not spontaneously active, but fire when perturbed by random perturbations mimicking synaptic input. We constructed one population of such phasic neurons, and another population of similar cells but which lacked the ability to fire phasically. We then studied how these two populations differed in the way that they encoded changes in afferent inputs. By comparison with the non-phasic population, the phasic population responds linearly to increases in tonic synaptic input. Non-phasic cells respond to transient elevations in synaptic input in a way that strongly depends on background activity levels, phasic cells in a way that is independent of background levels, and show a similar strong linearization of the response. These findings show large differences in information coding between the populations, and apparent functional advantages of asynchronous phasic firing.

Measuring oxytocin release in response to gavage: Computational modelling and assay validation.

In the present experiments, we tested the conclusion from previous electrophysiological experiments that gavage of sweet food and systemically applied insulin both stimulate oxytocin secretion. To do so, we measured oxytocin secretion from urethane-anaesthetised male rats, and demonstrated a significant increase in secretion in response to gavage of sweetened condensed milk but not isocaloric cream, and a significant increase in response to intravenous injection of insulin. We compared the measurements made in response to sweetened condensed milk with the predictions from a computational model, which we used to predict plasma concentrations of oxytocin from the published electrophysiological responses of oxytocin cells. The prediction from the computational model was very closely aligned to the levels of oxytocin measured in rats in response to gavage.

Basal ganglia dysplasia and mTORopathy: A potential cause of postoperative seizures in focal cortical dysplasia.

Pathogenic somatic MTOR variants in the cerebral cortex are a frequent cause of focal cortical dysplasia (FCD). We describe a child with drug and surgery-resistant focal epilepsy due to FCD type II who developed progressive enlargement and T2 signal hyperintensity in the ipsilateral caudate and lentiform nuclei. Histopathology of caudate nucleus biopsies showed dysmorphic neurons, similar to those in resected cortex. Genetic analysis of frontal and temporal cortex and caudate nucleus identified a pathogenic somatic MTOR variant [NM_004958.4:c.4375G > C (p.Ala1459Pro)] that was not present in blood-derived gDNA. The mean variant allele frequency ranged from 0.4% to 3.2% in cerebral cortex and up to 5.4% in the caudate nucleus. The basal ganglia abnormalities suggest more widespread, potentially hemispheric dysplasia in this patient, consistent with the pathogenic variant occurring in early cerebral development. This finding provides a potential explanation for persistent seizures in some patients with seemingly complete resection of FCD or disconnection of a dysplastic hemisphere.

Sweet's syndrome with postinflammatory elastolysis and Takayasu arteritis in a child: a case report and literature review.

Sweet's syndrome (SS) is an uncommon condition characterized by recurrent painful cutaneous inflammatory eruptions. It is rare in childhood and has a broad range of extracutaneous manifestations. We describe a child presenting with SS and postinflammatory elastolysis who subsequently developed aortitis complicated by aortic dilatation requiring surgical intervention. Histologic features of the aorta were consistent with Takayasu arteritis (TA). Our case and previously reported cases of pediatric SS complicated by aortitis all demonstrate striking clinical similarities in that all have been associated with postinflammatory elastolysis of involved skin and aneurysmal dilation of the thoracic aorta. We propose that TA should be considered one of the disease associations of SS when complicated by postinflammatory elastolysis and that early referral for cardiovascular screening be considered in this group of patients.

Perforin-mediated suppression of B-cell lymphoma.

In the present study, we have examined the effect of perforin (pfp) deficiency in 4 models of mouse B-cell lymphomagenesis. We have examined pfp loss on the background of either Mlh1 tumor suppressor allele loss or oncogene expression [Ig heavy chain (Emu)-v-Abl, Emu-myc, and vav-bcl2]. Pfp was shown to act as a suppressor of B-cell malignancies characteristically driven by v-Abl or bcl-2, whereas Mlh loss cooperated in accelerating spontaneous B-cell lymphomas characteristic of pfp loss. No protective role for pfp was observed in the more aggressive Emu-myc model of B-cell lymphoma. These transgenic models have allowed us to distinguish the role of pfp in surveillance of B-cell lymphomagenesis, as opposed to its loss simply driving the onset of a spontaneous lymphoma characteristic of pfp deficiency.

Mathematical modelling of the oxytocin and vasopressin secretory system.

Magnocellular oxytocin and vasopressin neurons of the hypothalamus project to the posterior pituitary where they secrete their peptide hormone signals directly into the bloodstream. Their large anatomically distinct secretory mechanisms provide a uniquely accessible system in which to unite experimental and modelling approaches in the investigation of how input signals and electrophysiological properties of neurons relate to physiological function. We describe how the mechanisms have been translated and assembled into a mathematical model representation that can explain and simulate the complex and highly non-linear stimulus-secretion coupling of these neurons, and how this model has been applied to further understand these systems.

Not just a chalazion-focal eyelid and orbital infection with Saksaenea vasiformis in an immunocompetent child.

We present the case of a 2-year-old immunocompetent boy who presented with subacute right-sided orbital cellulitis due to Saksaenea vasiformis infection. Initial differential diagnoses included chalazion and localized soft tissue malignancy. There was no history of trauma. Immunological review and investigations were unremarkable. He was treated with a total of 3 months of antifungal therapy. Following resolution, he had two episodes of spontaneously resolving localized eyelid erythema at 2 and 8 months.