Neurofibromatosis Type 1 and Type 2 Associated Tumours: Current trends in Diagnosis and Management with a focus on Novel Medical Therapies

Neurofibromatosis type 1 (NF1) and Neurofibromatosis type 2 (NF2) are distinct single gene disorders, which share a predisposition to formation of benign nervous system tumours due to loss of tumour suppressor function. Since identification of the genes encoding NF1 and NF2 in the early 1990s, significant progress has been made in understanding the biological processes and molecular pathways underlying tumour formation. As a result, identifying safe and effective medical approaches to treating NF1 and NF2-associated tumours has become a focus of clinical research and patient care in recent years. This thesis presents a comprehensive discussion of the complications of NF1 and NF2 and approaches to treatment, with a focus on key tumours in each condition. The significant functional impact of these disorders in children and young adults is illustrated, demonstrating the need for coordinated care from experienced multidisciplinary teams. Response of the first Australian patients offered novel medications under careful prospective monitoring for safety and efficacy, is described. The approach to treatment trials including principles of patient selection, rationale for candidate medication choices, and identification of appropriate outcome measures are outlined. Treatment response is assessed utilizing multiple criteria including radiologic response, functional status and patient reported outcomes. Tumours considered include plexiform neurofibromas in NF1, treated with the protein tyrosine kinase inhibitor imatinib, with limited benefit. In NF2, vestibular schwannomas were treated using the vascular endothelial growth factor inhibitor bevacizumab, showing definite benefit in a proportion of patients. Refinements in the clinical approach to NF-associated tumours are discussed, considering results from this early experience. Optimizing tumour surveillance prior to intervention, identifying the most potent yet tolerable agents for use, determining when medical therapy should be utilized in concert with surgical and other approaches, and establishing ways of stratifying individual risk of disease complications and likelihood of treatment benefit, remain important questions for the future

Functional correlates of clinical phenotype and severity in recurrent SCN2A variants

In SCN2A-related disorders, there is an urgent demand to establish efficient methods for determining the gain- (GoF) or loss-of-function (LoF) character of variants, to identify suitable candidates for precision therapies. Here we classify clinical phenotypes of 179 individuals with 38 recurrent SCN2A variants as early-infantile or later-onset epilepsy, or intellectual disability/autism spectrum disorder (ID/ASD) and assess the functional impact of 13 variants using dynamic action potential clamp (DAPC) and voltage clamp. Results show that 36/38 variants are associated with only one phenotypic group (30 early-infantile, 5 later-onset, 1 ID/ASD). Unexpectedly, we revealed major differences in outcome severity between individuals with the same variant for 40% of early-infantile variants studied. DAPC was superior to voltage clamp in predicting the impact of mutations on neuronal excitability and confirmed GoF produces early-infantile phenotypes and LoF later-onset phenotypes. For one early-infantile variant, the co-expression of the alpha(1) and beta(2) subunits of the Na(v)1.2 channel was needed to unveil functional impact, confirming the prediction of 3D molecular modeling. Neither DAPC nor voltage clamp reliably predicted phenotypic severity of early-infantile variants. Genotype, phenotypic group and DAPC are accurate predictors of the biophysical impact of SCN2A variants, but other approaches are needed to predict severity. A comprehensive biophysical analysis of disease-associated mutations in the voltage-gated sodium channel gene, SCN2A, suggests that dynamic action potential clamp may be a better predictor than voltage clamp of how these mutations alter neuronal excitability, though other approaches are needed to predict severity

Systemic therapy in neurofibromatosis type 2

The systemic treatment of patients with neurofibromatosis type 2 associated tumours is challenging, as these patients often have prolonged survival but with the inevitable propensity for their disease to cause symptoms, and no effective therapies other than local treatments such as surgery. Understanding the molecular mechanisms driving NF-2 pathogenesis holds promise for the potential use of targeted therapy. Initial studies of agents such as bevacizumab (angiogenesis inhibitor) and lapatinib (epidermal growth factor and ErbB2 inhibitor) have indicated benefit for selected patients. As the biology of NF-2 is dependent on multiple interlinked downstream signalling pathways, targeting multiple pathways may be more effective than single agents. Phase zero trials, adaptive phase II or small multi-arm trials, are likely the way forward in this rare disease. Ideally, well-tolerated targeted therapy would appear to be the most promising approach for patients with NF-2, given the natural history of this disease

Hearing and facial function outcomes for neurofibromatosis 2 clinical trials

Objectives: Vestibular schwannomas are the hallmark of neurofibromatosis 2 (NF2), occurring in >95% of patients. These tumors develop on the vestibulocochlear nerve and are associated with significant morbidity due to hearing loss, tinnitus, imbalance, facial weakness, and risk of early mortality from brainstem compression. Although hearing loss and facial weakness have been identified as important functional outcomes for patients with NF2, there is a lack of consensus regarding appropriate endpoints in clinical trials. Methods: The functional outcomes group reviewed existing endpoints for hearing and facial function and developed consensus recommendations for response evaluation in NF2 clinical trials. Results: For hearing endpoints, the functional group endorsed the use of maximum word recognition score as a primary endpoint, with the 95% critical difference as primary hearing outcomes. The group recommended use of the scaled measurement of improvement in lip excursion (SMILE) system for studies of facial function. Conclusions: These recommendations are intended to provide researchers with a common set of endpoints for use in clinical trials of patients with NF2. The use of common endpoints should improve the quality of clinical trials and foster comparison among studies for hearing loss and facial weakness

Severe hemorrhagic meningoencephalitis due to angiostrongylus cantonensis among young children in Sydney, Australia

Angiostrongylus cantonensis is the most common cause of eosinophilic meningitis worldwide. We describe 2 cases among young children from Sydney, Australia, where locally acquired infection of children has not been reported previously. Both cases manifested as severe hemorrhagic meningoencephalitis, one resulting in death. Angiostrongyliasis must be considered in acute neurological presentations occurring among individuals who live in endemic areas. © 2013 The Author 2013. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: [email protected]

Recessive Inactivating Mutations in TBCK, Encoding a Rab GTPase-Activating Protein, Cause Severe Infantile Syndromic Encephalopathy

Infantile encephalopathies are a group of clinically and biologically heterogeneous disorders for which the genetic basis remains largely unknown. Here, we report a syndromic neonatal encephalopathy characterized by profound developmental disability, severe hypotonia, seizures, diminished respiratory drive requiring mechanical ventilation, brain atrophy, dysgenesis of the corpus callosum, cerebellar vermis hypoplasia, and facial dysmorphism. Biallelic inactivating mutations in TBCK (TBC1-domain-containing kinase) were independently identified by whole-exome sequencing as the cause of this condition in four unrelated families. Matching these families was facilitated by the sharing of phenotypic profiles and WES data in a recently released web-based tool (Geno2MP) that links phenotypic information to rare variants in families with Mendelian traits. TBCK is a putative GTPase-activating protein (GAP) for small GTPases of the Rab family and has been shown to control cell growth and proliferation, actin-cytoskeleton dynamics, and mTOR signaling. Two of the three mutations (c.376C>T [p.Arg126(∗)] and c.1363A>T [p.Lys455(∗)]) are predicted to truncate the protein, and loss of the major TBCK isoform was confirmed in primary fibroblasts from one affected individual. The third mutation, c.1532G>A (p.Arg511His), alters a conserved residue within the TBC1 domain. Structural analysis implicated Arg511 as a required residue for Rab-GAP function, and in silico homology modeling predicted impaired GAP function in the corresponding mutant. These results suggest that loss of Rab-GAP activity is the underlying mechanism of disease. In contrast to other disorders caused by dysregulated mTOR signaling associated with focal or global brain overgrowth, impaired TBCK function results in progressive loss of brain volume

Visual outcomes in children with neurofibromatosis type 1-associated optic pathway glioma following chemotherapy: a multicenter retrospective analysis

Optic pathway gliomas (OPGs) occur in 15%–20% of children with neurofibromatosis type 1 (NF1); up to half become symptomatic. There is little information regarding ophthalmologic outcomes after chemotherapy. A retrospective multicenter study was undertaken to evaluate visual outcomes following chemotherapy for NF1-associated OPG, to identify risks for visual loss, and to ascertain indications for treatment. Subjects included children undergoing initial treatment for OPGs with chemotherapy between January 1997 and December 2007. Of 115 subjects, visual acuity (VA) decline and tumor progression were the primary reasons to initiate treatment, although there were significant differences in the pattern of indications cited among the institutions. Eighty-eight subjects and 168 eyes were evaluable for VA outcome. At completion of chemotherapy, VA improved (32% of subjects), remained stable (40%), or declined (28%). Tumor location was the most consistent prognostic factor for poor VA outcome. There was poor correlation between radiographic and VA outcomes. Although visual outcomes for NF1-associated OPG are not optimal, approximately one-third of children regain some vision with treatment. Since radiographic outcomes do not predict visual outcomes, their use as the primary measure of treatment success is in question. The lack of consensus regarding the indications for treatment underlines the need for better standardization of care. Future clinical trials for OPG require standardized visual assessment methods and clear definitions of visual outcomes

Infectious and autoantibody-associated encephalitis : clinical features and long-term outcome

Background and objectives: Pediatric encephalitis has a wide range of etiologies, clinical presentations, and outcomes. This study seeks to classify and characterize infectious, immune-mediated/autoantibody-associated and unknown forms of encephalitis, including relative frequencies, clinical and radiologic phenotypes, and long-term outcome. Methods: By using consensus definitions and a retrospective single-center cohort of 164 Australian children, we performed clinical and radiologic phenotyping blinded to etiology and outcomes, and we tested archived acute sera for autoantibodies to N-methyl-D-aspartate receptor, voltage-gated potassium channel complex, and other neuronal antigens. Through telephone interviews, we defined outcomes by using the Liverpool Outcome Score (for encephalitis). Results: An infectious encephalitis occurred in 30%, infection-associated encephalopathy in 8%, immune-mediated/autoantibody-associated encephalitis in 34%, and unknown encephalitis in 28%. In descending order of frequency, the larger subgroups were acute disseminated encephalomyelitis (21%), enterovirus (12%), Mycoplasma pneumoniae (7%), N-methyl-D-aspartate receptor antibody (6%), herpes simplex virus (5%), and voltage-gated potassium channel complex antibody (4%). Movement disorders, psychiatric symptoms, agitation, speech dysfunction, cerebrospinal fluid oligoclonal bands, MRI limbic encephalitis, and clinical relapse were more common in patients with autoantibodies. An abnormal outcome occurred in 49% of patients after a median follow-up of 5.8 years. Herpes simplex virus and unknown forms had the worst outcomes. According to our multivariate analysis, an abnormal outcome was more common in patients with status epilepticus, magnetic resonance diffusion restriction, and ICU admission. Conclusions: We have defined clinical and radiologic phenotypes of infectious and immune-mediated/autoantibody-associated encephalitis. In this resource-rich cohort, immune-mediated/autoantibody-associated etiologies are common, and the recognition and treatment of these entities should be a clinical priority.11 page(s

CSF neopterin, quinolinic acid and kynurenine/tryptophan ratio are biomarkers of active neuroinflammationResearch in context

Summary: Background: Defining the presence of acute and chronic brain inflammation remains a challenge to clinicians due to the heterogeneity of clinical presentations and aetiologies. However, defining the presence of neuroinflammation, and monitoring the effects of therapy is important given its reversible and potentially damaging nature. We investigated the utility of CSF metabolites in the diagnosis of primary neuroinflammatory disorders such as encephalitis and explored the potential pathogenic role of inflammation in epilepsy. Methods: Cerebrospinal fluid (CSF) collected from 341 paediatric patients (169 males, median age 5.8 years, range 0.1–17.1) were examined. The patients were separated into a primary inflammatory disorder group (n = 90) and epilepsy group (n = 80), who were compared with three control groups including neurogenetic and structural (n = 76), neurodevelopmental disorders, psychiatric and functional neurological disorders (n = 63), and headache (n = 32). Findings: There were statistically significant increases of CSF neopterin, kynurenine, quinolinic acid and kynurenine/tryptophan ratio (KYN/TRP) in the inflammation group compared to all control groups (all p < 0.0003). As biomarkers, at thresholds with 95% specificity, CSF neopterin had the best sensitivity for defining neuroinflammation (82%, CI 73–89), then quinolinic acid (57%, CI 47–67), KYN/TRP ratio (47%, CI 36–56) and kynurenine (37%, CI 28–48). CSF pleocytosis had sensitivity of 53%, CI 42–64). The area under the receiver operating characteristic curve (ROC AUC) of CSF neopterin (94.4% CI 91.0–97.7%) was superior to that of CSF pleocytosis (84.9% CI 79.5–90.4%) (p = 0.005). CSF kynurenic acid/kynurenine ratio (KYNA/KYN) was statistically decreased in the epilepsy group compared to all control groups (all p ≤ 0.0003), which was evident in most epilepsy subgroups. Interpretation: Here we show that CSF neopterin, kynurenine, quinolinic acid and KYN/TRP are useful diagnostic and monitoring biomarkers of neuroinflammation. These findings provide biological insights into the role of inflammatory metabolism in neurological disorders and provide diagnostic and therapeutic opportunities for improved management of neurological diseases. Funding: Financial support for the study was granted by Dale NHMRC Investigator grant APP1193648, University of Sydney, Petre Foundation, Cerebral Palsy Alliance and Department of Biochemistry at the Children’s Hospital at Westmead. Prof Guillemin is funded by NHMRC Investigator grant APP 1176660 and Macquarie University