The neural basis of deficient response inhibition in children with neurofibromatosis type 1: Evidence from a functional MRI study

Systematic Review and Meta-Analysis: Attention-Deficit/Hyperactivity Disorder Symptoms in Children With Neurofibromatosis Type 1

OBJECTIVE

This meta-analysis aimed to robustly estimate differences in attention-deficit/hyperactivity disorder (ADHD) symptoms between children and adolescents with and without neurofibromatosis type 1 (NF1).

METHOD

Systematic literature searches were conducted in Scopus, PsycINFO, Web of Science, PubMed, and ProQuest in September 2022, with a supplemental search conducted in Google Scholar in February 2023. The searches identified 2,153 unique articles. Screening identified 114 academic journal articles that assessed parent/caregiver- or teacher-reported ADHD symptoms for children/adolescents with NF1. Two researchers independently screened articles and extracted data. The primary outcome was group differences in ADHD symptoms between children/adolescents with and without NF1 (Hedges g). Data were analyzed using robust variance estimation and random-effects models.

RESULTS

The meta-analysis included 70 studies (138 effect sizes), involving 3,653 children/adolescents with NF1 (46% female; mean age = 9.69 years, SD = 2.60 years) and 4,895 children/adolescents without NF1 (48% female; mean age = 10.03 years, SD = 3.10 years). According to parent/caregiver reports, children/adolescents with NF1 exhibited more severe inattentive symptoms (g = 1.20; 95% CI = 1.06-1.35), hyperactive/impulsive symptoms (g = 0.85; 95% CI = 0. 68-1.03), and combined ADHD symptoms (g = 1.02; 95% CI = 0.87-1.17) than unaffected controls. Inattentive ADHD symptoms were more elevated than hyperactivity/impulsivity for children/adolescents with NF1. Larger effect sizes for inattention and hyperactivity/impulsivity were associated with older age, lower intelligence quotient (IQ), and parent/caregiver vs teacher reports.

CONCLUSION

NF1 is a monogenic condition that has strong associations with elevated ADHD symptoms. Findings highlight the importance of early intervention and targeted support for ADHD-related problems in children with NF1.

PLAIN LANGUAGE SUMMARY

Increasing evidence has suggested a higher risk for attention-deficit/hyperactivity disorder (ADHD) in individuals with neurofibromatosis type 1 (NF1). In this study of ADHD symptom severity in youth with NF1, the authors analyzed data from 70 articles. The authors found much more severe ADHD symptoms in children and adolescents with NF1 compared to youth without NF1. Inattentive symptoms were more pronounced in children with NIF who were older or had a lower IQ.

STUDY PREREGISTRATION INFORMATION

Compare the ADHD problems between NF1 and control groups; https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=462063.

Social Communication in Ras Pathway Disorders: A Comprehensive Review From Genetics to Behavior in Neurofibromatosis Type 1 and Noonan Syndrome

Neurofibromatosis type 1 (NF1) and Noonan syndrome (NS) are neurogenetic syndromes caused by pathogenetic variants encoding components of the Ras-ERK-MAPK (Ras/extracellular signal-regulated kinase/mitogen-activated protein kinase) signaling pathway (Ras pathway). NF1 and NS are associated with differences in social communication and related neuropsychiatric risks. During the last decade, there has been growing interest in Ras-linked syndromes as models to understand social communication deficits and autism spectrum disorder. We systematically review the literature between 2010 and 2023 focusing on the social communication construct of the Research Domain Criteria framework. We provide an integrative summary of the research on facial and nonfacial social communication processes in NF1 and NS across molecular, cellular, neural circuitry, and behavioral domains. At the molecular and cellular levels, dysregulation in the Ras pathway is intricately tied to variations in social communication through changes in GABAergic (gamma-aminobutyric acidergic), glutamatergic, and serotonergic transmission, as well as inhibitory/excitatory imbalance. Neural circuitry typically associated with learning, attention, and memory in NF1 and NS (e.g., corticostriatal connectivity) is also implicated in social communication. We highlight less-researched potential mechanisms for social communication, such as white matter connectivity and the default mode network. Finally, key gaps in NF1 and NS literature are identified, and a roadmap for future research is provided. By leveraging genetic syndrome research, we can understand the mechanisms associated with behaviors and psychiatric disorders.

Academic Achievement of Children With Neurofibromatosis Type 1

BACKGROUND AND OBJECTIVES

Learning difficulties are frequently reported in children with neurofibromatosis type 1 (NF1), yet little is known about the extent and predictors of their academic functions across ages. We aimed to examine the developmental patterns of academic achievement in these children from childhood to adolescence and how these patterns differ across demographic and NF1-related disease factors.

METHODS

This cross-sectional study integrated data of 1512 children with NF1 (mean age, 11.2 years, SD, 3.62, range, 3-18, 46.5% female patients) from 8 institutions. Academic functioning was assessed with Woodcock-Johnson Tests of Achievement or the Wechsler Individual Achievement Test. Data were analyzed primarily using time-varying effect modeling.

RESULTS

Participants' academic achievement was significantly lower than the normative means across ages, and the gap widened from middle childhood to midadolescence. Academic age trends varied across academic domains and demographic and disease factors. Male patients demonstrated larger deviations in math at midchildhood and in reading and writing between midchildhood and midadolescence. Children with lower parental education demonstrated larger deviations in math, reading, and writing between midchildhood and midadolescence. Children with familial NF1 demonstrated larger deviations in math at midchildhood and mid-to-late-adolescence, and in reading and writing between midchildhood and midadolescence.

CONCLUSIONS

Academic difficulties in children with NF1 emerge early and worsen with age. The findings also highlight the variability within this population across demographic and disease factors. The age-specific estimates of academic functions can serve as the first NF1-specific academic norms, providing useful insights for future research and practice.

Neuropsychological factors associated with performance on the rey-osterrieth complex figure test in children with neurofibromatosis type 1

Children with neurofibromatosis type 1 (NF1) are at considerable risk for cognitive difficulties, including visuospatial deficits and executive dysfunction. This study aimed to (1) assess the overall performance of children with NF1 on the Rey-Osterrieth Complex Figure Test (RCFT) compared to unaffected siblings and (2) examine neuropsychological predictors of RCFT performance in children with NF1. A retrospective clinical audit was performed on neuropsychological records from a multidisciplinary NF1 Clinic in Australia. We searched for children that had completed an assessment between 2000 and 2015 which included the RCFT and other neuropsychological outcomes in this study. These included the Wechsler Intelligence Scale for Children, Judgment of Line Orientation (JLO), Tower of London test, Conners ADHD Scales, and the Behavioral Rating Inventory of Executive Function (BRIEF). The study population consisted of 191 children with NF1 aged 6-16 years, and 55 unaffected siblings recruited from a separate study. Results revealed that 62% of children with NF1 performed at or below the first percentile on the RCFT copy, which was significantly worse than their unaffected siblings. Visuospatial skills, parent-rated executive abilities, ADHD symptoms, and intellectual skills all predicted poorer performance on the RCFT copy, however the best fitting multiple regression model only contained the JLO, BRIEF Metacognition Index, and chronological age. The JLO emerged as the strongest predictor of RCFT performance. This study provides evidence that visuospatial deficits are a key driver of reduced RCFT performance in NF1 and that executive skills as well as a younger age are also independent predictors of RCFT performance.

The mediating role of ADHD symptoms between executive function and social skills in children with neurofibromatosis type 1

Children with neurofibromatosis type 1 (NF1) often experience executive dysfunction, attention deficit/hyperactivity disorder (ADHD) symptoms and poor social skills, however, the nature of the relationships between these domains in children with NF1 is unclear. This study investigated these relationships using primary caregiver ratings of executive functions, ADHD symptoms and social skills in children with NF1. Participants were 136 children with NF1 and 93 typically developing (TD) controls aged 3-15 years recruited from 3 multidisciplinary neurofibromatosis clinics in Melbourne and Sydney, Australia, and Washington DC, USA. Mediation analysis was performed on primary outcome variables: parent ratings of executive functions (Behavior Rating Inventory of Executive Function, Metacognition Index), ADHD symptoms (Conners-3/Conners ADHD Diagnostic and Statistical Manual for Mental Disorders Scales) and social skills (Social Skills Improvement System-Rating Scale), adjusting for potential confounders (full scale IQ, sex, and social risk). Results revealed significantly poorer executive functions, elevated ADHD symptoms and reduced social skills in children with NF1 compared to controls. Poorer executive functions significantly predicted elevated ADHD symptoms and poorer social skills. Elevated ADHD symptoms significantly mediated the relationship between executive functions and social skills problems although did not fully account for social dysfunction. This study provides evidence for the importance of targeting ADHD symptoms as part of future interventions aimed at promoting prosocial behaviors in children with NF1.

Cognitive functioning, patient health communication, and worry mediate pain predictive effects on health-related quality of life in youth with sickle cell disease

OBJECTIVES

The objective was to investigate the serial mediating effects of perceived cognitive functioning, patient health communication, and disease-specific worry in the relationship between pain and overall generic health-related quality of life (HRQOL) in youth with sickle cell disease (SCD) from the patient perspective.

METHODS

The pain, cognitive functioning, communication and worry scales from the Pediatric Quality of Life Inventory (PedsQL) Sickle Cell Disease Module and the PedsQL Multidimensional Fatigue Scale, and the PedsQL 4.0 Generic Core Scales were completed in a multisite national study by 233 youth with SCD of ages 5-18. Hierarchical multiple regression and serial multiple mediator model analyses were conducted to test the mediating effects of perceived cognitive functioning, health communication, and disease-specific worry as intervening variables in the association between the pain predictor variable and overall generic HRQOL.

RESULTS

Pain predictive effects on overall generic HRQOL were serially mediated by cognitive functioning, health communication, and disease-specific worry. In predictive analytics models utilizing hierarchical multiple regression analyses with age and gender demographic covariates, pain, cognitive functioning, health communication, and worry accounted for 65% of the variance in patient-reported overall generic HRQOL (P < .001), representing a large effect size.

CONCLUSIONS

Perceived cognitive functioning, patient health communication, and disease-specific worry explain in part the mechanism of pain predictive effects on overall generic HRQOL in youth with SCD. Identifying SCD-specific pain, perceived cognitive functioning, health communication, and disease-specific worry as predictor variables of overall generic HRQOL from the patient perspective may inform clinical interventions and future patient-centered clinical research.

An executive functioning perspective in neurofibromatosis type 1: from ADHD and autism spectrum disorder to research domains

PURPOSE

Neurofibromatosis type 1 (NF1) is a rare monogenic disorder associated with executive function (EF) deficits and heightened risk for attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). The goal of this paper is to understand how EFs provide a common foundation to understand vulnerabilities for ADHD and ASD within NF1.

METHODS

A literature review and synthesis was conducted.

RESULTS

EF difficulties in working memory, inhibitory control, cognitive flexibility, and planning are evident in NF1, ADHD, and ASD. However, relatively little is known about the heterogeneity of EFs and ADHD and ASD outcomes in NF1. Assessment of ADHD and ASD in NF1 is based on behavioral symptoms without understanding neurobiological contributions. Recent efforts are promoting the use of dimensional and multidisciplinary methods to better understand normal and abnormal behavior, including integrating information from genetics to self-report measures.

CONCLUSION

NF1 is a monogenic disease with well-developed molecular and phenotypic research as well as complementary animal models. NF1 presents an excellent opportunity to advance our understanding of the neurobiological impact of known pathogenic variation in normal and abnormal neural pathways implicated in human psychopathology. EFs are core features of NF1, ADHD, and ASD, and these neurodevelopmental outcomes are highly prevalent in NF1. We propose a multilevel approach for understanding EFs in patients with NF1.This is essential to advance targeted interventions for NF1 patients and to advance the exciting field of research in this condition.

Cognitive functioning and pain interference mediate pain predictive effects on health-related quality of life in pediatric patients with Neurofibromatosis Type 1

OBJECTIVES

The objective was to investigate the serial mediating effects of perceived cognitive functioning and pain interference in daily living in the relationship between perceived pain and overall generic health-related quality of life (HRQOL) in children, adolescents, and young adults with Neurofibromatosis Type 1 (NF1).

METHODS

The Pain, Cognitive Functioning, and Pain Impact Scales from the PedsQL Neurofibromatosis Type 1 Module and the PedsQL 4.0 Generic Core Scales were completed in a multi-site national study by 323 patients ages 5-25 and 335 parents. A serial multiple mediator model analysis was conducted to test the hypothesized sequential mediating effects of cognitive functioning and pain interference as intervening variables in the association between pain as a predictor variable and overall generic HRQOL.

RESULTS

Pain predictive effects on overall generic HRQOL were serially mediated by cognitive functioning and pain interference. In predictive analytics models utilizing hierarchical multiple regression analyses with age and gender demographic covariates, pain, cognitive functioning and pain interference accounted for 66% of the variance in patient-reported generic HRQOL and 57% of the variance in parent proxy-reported generic HRQOL (P < 0.001), reflecting large effect sizes.

CONCLUSIONS

Cognitive functioning and pain interference explain in part the mechanism of pain predictive effects on overall generic HRQOL in pediatric patients with NF1. Identifying NF1-specific pain, cognitive functioning, and pain interference as salient predictors of overall generic HRQOL from the patient and parent perspective facilitates a family-centered orientation to the comprehensive care of children, adolescents, and young adults with NF1.

Guanfacine treatment improves ADHD phenotypes of impulsivity and hyperactivity in a neurofibromatosis type 1 mouse model

Background

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a mutation in one copy of the neurofibromin gene (NF1^+/−). Even though approximately 40–60% of children with NF1 meet the criteria for attention deficit hyperactivity disorder (ADHD), very few preclinical studies, if any, have investigated alterations in impulsivity and risk-taking behavior. Mice with deletion of a single NF1 gene (Nf1^+/−) recapitulate many of the phenotypes of NF1 patients.

Methods

We compared wild-type (WT) and Nf1^+/− mouse strains to investigate differences in impulsivity and hyperactivity using the delay discounting task (DDT), cliff avoidance reaction (CAR) test, and open field. We also investigated whether treatment with the clinically effective alpha-2A adrenergic receptor agonist, guanfacine (0.3 mg/kg, i.p.), would reverse deficits observed in behavioral inhibition.

Results

Nf1^+/− mice chose a higher percentage of smaller rewards when both 10- and 20-s delays were administered compared to WT mice, suggesting Nf1^+/− mice are more impulsive. When treated with guanfacine (0.3 mg/kg, i.p.), Nf1^+/− mice exhibited decreased impulsive choice by waiting for the larger, delayed reward. Nf1^+/− mice also exhibited deficits in behavioral inhibition compared to WT mice in the CAR test by repetitively entering the outer edge of the platform where they risk falling. Treatment with guanfacine ameliorated these deficits. In addition, Nf1^+/− mice exhibited hyperactivity as increased distance was traveled compared to WT controls in the open field. This hyperactivity in Nf1^+/− mice was reduced with guanfacine pre-treatment.

Conclusions

Overall, our study confirms that Nf1^+/− mice exhibit deficits in behavioral inhibition in multiple contexts, a key feature of ADHD, and can be used as a model system to identify alterations in neural circuitry associated with symptoms of ADHD in children with NF1.

Can the Cognitive Phenotype in Neurofibromatosis Type 1 (NF1) Be Explained by Neuroimaging? A Review

Neurofibromatosis type 1 (NF1) is one of the most frequent monogenetic disorders. It can be associated with cognitive dysfunctions in several domains such as executive functioning, language, visual perception, motor skills, social skills, memory and/or attention. Neuroimaging is becoming more and more important for a clearer understanding of the neural basis of these deficits. In recent years, several studies have used different imaging techniques to examine structural, morphological and functional alterations in NF1 disease. They have shown that NF1 patients have specific brain characteristics such as Unidentified Bright Objects (UBOs), macrocephaly, a higher volume of subcortical structures, microstructure integrity alterations, or connectivity alterations. In this review, which focuses on the studies published after the last 2 reviews of this topic (in 2010 and 2011), we report on recent structural, morphological and functional neuroimaging studies in NF1 subjects, with special focus on those that examine the neural basis of the NF1 cognitive phenotype. Although UBOs are one of the most obvious and visible elements in brain imaging, correlation studies have failed to establish a robust and reproducible link between major cognitive deficits in NF1 and their presence, number or localization. In the same vein, the results among structural studies are not consistent. Functional magnetic resonance imaging (fMRI) studies appear to be more sensitive, especially for understanding the executive function deficit that seems to be associated with a dysfunction in the right inferior frontal areas and the middle frontal areas. Similarly, fMRI studies have found that visuospatial deficits could be associated with a dysfunction in the visual cortex and especially in the magnocellular pathway involved in the processing of low spatial frequency and high temporal frequency. Connectivity studies have shown a reduction in anterior-posterior “long-range” connectivity and a deficit in deactivation in default mode network (DMN) during cognitive tasks. In conclusion, despite the contribution of new imaging techniques and despite relative advancement, the cognitive phenotype of NF1 patients is not totally understood.

Reproducibility of cognitive endpoints in clinical trials: lessons from neurofibromatosis type 1

Objective

Rapid developments in understanding the molecular mechanisms underlying cognitive deficits in neurodevelopmental disorders have increased expectations for targeted, mechanism‐based treatments. However, translation from preclinical models to human clinical trials has proven challenging. Poor reproducibility of cognitive endpoints may provide one explanation for this finding. We examined the suitability of cognitive outcomes for clinical trials in children with neurofibromatosis type 1 (NF1) by examining test‐retest reliability of the measures and the application of data reduction techniques to improve reproducibility.

Methods

Data were analyzed from the STARS clinical trial (n = 146), a multi‐center double‐blind placebo‐controlled phase II trial of lovastatin, conducted by the NF Clinical Trials Consortium. Intra‐class correlation coefficients were generated between pre‐ and post‐performances (16‐week interval) on neuropsychological endpoints in the placebo group to determine test‐retest reliabilities. Confirmatory factor analysis was used to reduce data into cognitive domains and account for measurement error.

Results

Test‐retest reliabilities were highly variable, with most endpoints demonstrating unacceptably low reproducibility. Data reduction confirmed four distinct neuropsychological domains: executive functioning/attention, visuospatial ability, memory, and behavior. Test‐retest reliabilities of latent factors improved to acceptable levels for clinical trials. Applicability and utility of our model was demonstrated by homogeneous effect sizes in the reanalyzed efficacy data.

Interpretation

These data demonstrate that single observed endpoints are not appropriate to determine efficacy, partly accounting for the poor test‐retest reliability of cognitive outcomes in clinical trials in neurodevelopmental disorders. Recommendations to improve reproducibility are outlined to guide future trial design.

Discriminating between neurofibromatosis-1 and typically developing children by means of multimodal MRI and multivariate analyses

Neurofibromatosis Type 1 leads to brain anomalies involving both gray and white matter. The extent and granularity of these anomalies, together with their possible impact on brain activity, is still unknown. In this multicentric cross-sectional study we submitted a sample of 42 typically developing and 38 neurofibromatosis-1 children to a multimodal MRI assessment including T1, diffusion weighted and resting state functional sequences. We used a pipeline involving several features selection steps coupled with multivariate statistical analysis (supporting vector machine) to discriminate between the two groups while having interpretable models. We used MRI indexes measuring macro (gray matter volume) and microstructural (fractional anisotropy, mean diffusivity) characteristics of the brain, as well as indexes of brain activity (fractional amplitude of low frequency fluctuations) and connectivity (local and global correlation) at rest. We found that structural indexes could discriminate between the two groups, with the mean diffusivity leading to performance as high as the combination of all structural indexes combined (accuracy = 0.86), while functional indexes had worse performances. The MRI signature of NF1 brain pathology is a combination of gray and white matter abnormalities, as measured with gray matter volume, fractional anisotropy, and mean diffusivity.

From process to progress-2017 International Conference on Neurofibromatosis 1, Neurofibromatosis 2 and Schwannomatosis

The neurofibromatoses are inherited, tumor suppressor disorders that are characterized by multiple, benign peripheral nerve sheath tumors and other nervous system tumors. Each disease is associated with a distinct genetic mutation and with a different pathogenesis and clinical course. Neurofibromatosis 1 (NF1) is common and epitomized by multiple neurofibromas with widespread complications. NF2 and schwannomatosis are rare diseases that are typified by multiple schwannomas that are particularly painful in people with schwannomatosis. Since 1985, the Children's Tumor Foundation (formerly the National Neurofibromatosis Foundation) has hosted an international Neurofibromatosis Conference, bringing together international participants who are focused on NF research and clinical care. The 2017 Conference, held in Washington, DC, was among the largest gatherings of NF researchers to date and included presentations from clinicians and basic scientists, highlighting new data regarding the molecular and cellular mechanisms underlying each of these diseases as well as results from clinical studies and clinical trials. This article summarizes the findings presented at the meeting and represents the current state-of-the art for NF research.

Effects of methylphenidate on cognition and behaviour in children with neurofibromatosis type 1: a study protocol for a randomised placebo-controlled crossover trial

INTRODUCTION

Dopamine dysregulation has been identified as a key modulator of behavioural impairment in neurofibromatosis type 1 (NF1) and a potential therapeutic target. Preclinical research demonstrates reduced dopamine in the brains of genetically engineered NF1 mouse strains is associated with reduced spatial-learning and attentional dysfunction. Methylphenidate, a stimulant medication that increases dopaminergic and noradrenergic neurotransmission, rescued the behavioural and dopamine abnormalities. Although preliminary clinical trials have demonstrated that methylphenidate is effective in treating attention deficit hyperactivity disorder (ADHD) symptoms in children with NF1, its therapeutic effect on cognitive performance is unclear. The primary aim of this clinical trial is to assess the efficacy of methylphenidate for reducing attention deficits, spatial working memory impairments and ADHD symptoms in children with NF1.

METHODS AND ANALYSIS

A randomised, double-blind, placebo-controlled trial of methylphenidate with a two period crossover design. Thirty-six participants with NF1 aged 7-16 years will be randomised to one of two treatment sequences: 6 weeks of methylphenidate followed by 6 weeks of placebo or; 6 weeks of placebo followed by 6 weeks of methylphenidate. Neurocognitive and behavioural outcomes as well as neuroimaging measures will be completed at baseline and repeated at the end of each treatment condition (week 6, week 12). Primary outcome measures are omission errors on the Conners Continuous Performance Test-II (attention), between-search errors on the Spatial Working Memory task from the Cambridge Neuropsychological Test Automated Battery (spatial working memory) and the Inattentive and Hyperactivity/Impulsivity Symptom Scales on the Conners 3-Parent. Secondary outcomes will examine the effect of methylphenidate on executive functions, attention, visuospatial skills, behaviour, fine-motor skills, language, social skills and quality of life.

ETHICS AND DISSEMINATION

This trial has hospital ethics approval and the results will be disseminated through peer-reviewed publications and international conferences.

TRIAL REGISTRATION NUMBER

ACTRN12611000765921.