Sequencing chromosomal abnormalities reveals neurodevelopmental loci that confer risk across diagnostic boundaries.

Balanced chromosomal abnormalities (BCAs) represent a relatively untapped reservoir of single-gene disruptions in neurodevelopmental disorders (NDDs). We sequenced BCAs in patients with autism or related NDDs, revealing disruption of 33 loci in four general categories: (1) genes previously associated with abnormal neurodevelopment (e.g., AUTS2, FOXP1, and CDKL5), (2) single-gene contributors to microdeletion syndromes (MBD5, SATB2, EHMT1, and SNURF-SNRPN), (3) novel risk loci (e.g., CHD8, KIRREL3, and ZNF507), and (4) genes associated with later-onset psychiatric disorders (e.g., TCF4, ZNF804A, PDE10A, GRIN2B, and ANK3). We also discovered among neurodevelopmental cases a profoundly increased burden of copy-number variants from these 33 loci and a significant enrichment of polygenic risk alleles from genome-wide association studies of autism and schizophrenia. Our findings suggest a polygenic risk model of autism and reveal that some neurodevelopmental genes are sensitive to perturbation by multiple mutational mechanisms, leading to variable phenotypic outcomes that manifest at different life stages.

The functional impact of 1,570 individual amino acid substitutions in human OTC.

Deleterious mutations in the X-linked gene encoding ornithine transcarbamylase (OTC) cause the most common urea cycle disorder, OTC deficiency. This rare but highly actionable disease can present with severe neonatal onset in males or with later onset in either sex. Individuals with neonatal onset appear normal at birth but rapidly develop hyperammonemia, which can progress to cerebral edema, coma, and death, outcomes ameliorated by rapid diagnosis and treatment. Here, we develop a high-throughput functional assay for human OTC and individually measure the impact of 1,570 variants, 84% of all SNV-accessible missense mutations. Comparison to existing clinical significance calls, demonstrated that our assay distinguishes known benign from pathogenic variants and variants with neonatal onset from late-onset disease presentation. This functional stratification allowed us to identify score ranges corresponding to clinically relevant levels of impairment of OTC activity. Examining the results of our assay in the context of protein structure further allowed us to identify a 13 amino acid domain, the SMG loop, whose function appears to be required in human cells but not in yeast. Finally, inclusion of our data as PS3 evidence under the current ACMG guidelines, in a pilot reclassification of 34 variants with complete loss of activity, would change the classification of 22 from variants of unknown significance to clinically actionable likely pathogenic variants. These results illustrate how large-scale functional assays are especially powerful when applied to rare genetic diseases.

Severity-adjusted evaluation of liver transplantation on health outcomes in urea cycle disorders.

PURPOSE: Liver transplantation (LTx) is performed in individuals with urea cycle disorders when medical management (MM) insufficiently prevents the occurrence of hyperammonemic events. However, there is a paucity of systematic analyses on the effects of LTx on health-related outcome parameters compared to individuals with comparable severity who are medically managed. METHODS: We investigated the effects of LTx and MM on validated health-related outcome parameters, including the metabolic disease course, linear growth, and neurocognitive outcomes. Individuals were stratified into "severe" and "attenuated" categories based on the genotype-specific and validated in vitro enzyme activity. RESULTS: LTx enabled metabolic stability by prevention of further hyperammonemic events after transplantation and was associated with a more favorable growth outcome compared with individuals remaining under MM. However, neurocognitive outcome in individuals with LTx did not differ from the medically managed counterparts as reflected by the frequency of motor abnormality and cognitive standard deviation score at last observation. CONCLUSION: Whereas LTx enabled metabolic stability without further need of protein restriction or nitrogen-scavenging therapy and was associated with a more favorable growth outcome, LTx-as currently performed-was not associated with improved neurocognitive outcomes compared with long-term MM in the investigated urea cycle disorders.

Impact of supplementation with L-citrulline/arginine after liver transplantation in individuals with Urea Cycle Disorders.

OBJECTIVE: Liver transplantation (LTx) is an intervention when medical management is not sufficiently preventing individuals with urea cycle disorders (UCDs) from the occurrence of hyperammonemic events. Supplementation with L-citrulline/arginine is regularly performed prior to LTx to support ureagenesis and is often continued after the intervention. However, systematic studies assessing the impact of long-term L-citrulline/arginine supplementation in individuals who have undergone LTx is lacking to date. METHODS: Using longitudinal data collected systematically, a comparative analysis was carried out by studying the effects of long-term L-citrulline/arginine supplementation vs. no supplementation on health-related outcome parameters (i.e., anthropometric, neurological, and cognitive outcomes) in individuals with UCDs who have undergone LTx. Altogether, 52 individuals with male ornithine transcarbamylase deficiency, citrullinemia type 1 and argininosuccinic aciduria and a pre-transplant "severe" disease course who have undergone LTx were investigated by using recently established and validated genotype-specific in vitro enzyme activities. RESULTS: Long-term supplementation of individuals with L-citrulline/arginine who have undergone LTx (n = 16) does neither appear to alter anthropometric nor neurocognitive endpoints when compared to their severity-adjusted counterparts that were not supplemented (n = 36) after LTx with mean observation periods between four to five years. Moreover, supplementation with L-citrulline/arginine was not associated with an increase of disease-specific plasma arithmetic mean values for the respective amino acids when compared to the non-supplemented control cohort. CONCLUSION: Although supplementation with L-citrulline/arginine is often continued after LTx, this pilot study does neither identify altered long-term anthropometric or neurocognitive health-related outcomes nor does it find an adequate biochemical response as reflected by the unaltered plasma arithmetic mean values for L-citrulline or L-arginine. Further prospective analyses in larger samples and even longer observation periods will provide more insight into the usefulness of long-term supplementation with L-citrulline/arginine for individuals with UCDs who have undergone LTx.

Consensus guidelines for the diagnosis and management of succinic semialdehyde dehydrogenase deficiency.

Succinic semialdehyde dehydrogenase deficiency (SSADHD) (OMIM #271980) is a rare autosomal recessive metabolic disorder caused by pathogenic variants of ALDH5A1. Deficiency of SSADH results in accumulation of γ-aminobutyric acid (GABA) and other GABA-related metabolites. The clinical phenotype of SSADHD includes a broad spectrum of non-pathognomonic symptoms such as cognitive disabilities, communication and language deficits, movement disorders, epilepsy, sleep disturbances, attention problems, anxiety, and obsessive-compulsive traits. Current treatment options for SSADHD remain supportive, but there are ongoing attempts to develop targeted genetic therapies. This study aimed to create consensus guidelines for the diagnosis and management of SSADHD. Thirty relevant statements were initially addressed by a systematic literature review, resulting in different evidence levels of strength according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria. The highest level of evidence (level A), based on randomized controlled trials, was unavailable for any of the statements. Based on cohort studies, Level B evidence was available for 12 (40%) of the statements. Thereupon, through a process following the Delphi Method and directed by the Appraisal of Guidelines for Research and Evaluation (AGREE II) criteria, expert opinion was sought, and members of an SSADHD Consensus Group evaluated all the statements. The group consisted of neurologists, epileptologists, neuropsychologists, neurophysiologists, metabolic disease specialists, clinical and biochemical geneticists, and laboratory scientists affiliated with 19 institutions from 11 countries who have clinical experience with SSADHD patients and have studied the disorder. Representatives from parent groups were also included in the Consensus Group. An analysis of the survey's results yielded 25 (83%) strong and 5 (17%) weak agreement strengths. These first-of-their-kind consensus guidelines intend to consolidate and unify the optimal care that can be provided to individuals with SSADHD.

Ophthalmic manifestations of NAA10-related and NAA15-related neurodevelopmental syndromes: Analysis of cortical visual impairment and refractive errors.

NAA10-related (Ogden syndrome) and NAA15-related neurodevelopmental syndrome are known to present with varying degrees of intellectual disability, hypotonia, congenital cardiac abnormalities, seizures, and delayed speech and motor development. However, the ophthalmic manifestations of NAA10 and NAA15 variants are not yet fully characterized or understood. This study analyzed the prevalence of six ophthalmic conditions (cortical visual impairment, myopia, hyperopia, strabismus, nystagmus, and astigmatism) in 67 patients with pathogenic (P) or likely pathogenic (LP) variants in the NAA10 cohort (54 inherited, 10 de novo; 65 missense, 2 frameshift) and 19 patients with (L)P variants in the NAA15 cohort (18 de novo; 8 frameshift, 4 missense, 4 nonsense, and 1 splice site). Patients were interviewed virtually or in-person to collect a comprehensive medical history verified by medical records. These records were then analyzed to calculate the prevalence of these ophthalmic manifestations in each cohort. Analysis revealed a higher prevalence of ophthalmic conditions in our NAA10 cohort compared to existing literature (myopia 25.4% vs. 4.7%; astigmatism 37.3% vs. 13.2%; strabismus 28.4% vs. 3.8%; CVI 22.4% vs. 8.5%, respectively). No statistically significant differences were identified in the prevalence of these conditions between the NAA10 and NAA15 variants. Our study includes novel neuroimaging of 13 NAA10 and 5 NAA15 probands, which provides no clear correlation between globe size and severity of comorbid ophthalmic disease. Finally, anecdotal evidence was compiled to underscore the importance of early ophthalmologic evaluations and therapeutic interventions.

Dysfunctional Postnatal Mitochondrial Energy Metabolism in a Patient with Neurodevelopmental Defects Caused by Intrauterine Growth Restriction Due to Idiopathic Placental Insufficiency.

We report the case of a four-year-old male patient with a complex medical history born prematurely as the result of intrauterine growth restriction due to placental insufficiency. His clinical manifestations included severe neurodevelopmental deficits, global developmental delay, Pierre-Robin sequence, and intractable epilepsy with both generalized and focal features. The proband's low levels of citrulline and lactic acidosis provoked by administration of Depakoke were evocative of a mitochondrial etiology. The proband's genotype-phenotype correlation remained undefined in the absence of nuclear and mitochondrial pathogenic variants detected by deep sequencing of both genomes. However, live-cell mitochondrial metabolic investigations provided evidence of a deficient oxidative-phosphorylation pathway responsible for adenosine triphosphate (ATP) synthesis, leading to chronic energy crisis in the proband. In addition, our metabolic analysis revealed metabolic plasticity in favor of glycolysis for ATP synthesis. Our mitochondrial morphometric analysis by transmission electron microscopy confirmed the suspected mitochondrial etiology, as the proband's mitochondria exhibited an immature morphology with poorly developed and rare cristae. Thus, our results support the concept that suboptimal levels of intrauterine oxygen and nutrients alter fetal mitochondrial metabolic reprogramming toward oxidative phosphorylation (OXPHOS) leading to a deficient postnatal mitochondrial energy metabolism. In conclusion, our collective studies shed light on the long-term postnatal mitochondrial pathophysiology caused by intrauterine growth restriction due to idiopathic placental insufficiency and its negative impact on the energy-demanding development of the fetal and postnatal brain.

Reading skills in males with 47,XXY: Risk factors and the influence of hormonal replacement therapy (HRT).

PURPOSE: 47,XXY is often associated with reduced expressive language and literacy skills. This retrospective cross-sectional study investigated risk factors (hormone replacement deficiency, pre-or postnatal diagnosis, and history of family learning disabilities [FLDs]) associated with reading skills in 152 males. METHODS: We analyzed Woodcock Reading Mastery Test scores among 7 prenatally diagnosed male hormone replacement therapy (HRT) groups using analysis of variance along with analysis of variance and 2 postnatally diagnosed male HRT groups (No-T and T) using t tests. Treated prenatally diagnosed males with FLDs were compared with an identically treated prenatal HRT group with no history of FLDs using a t test. RESULTS: In prenatally diagnosed males, significant treatment differences were observed on several reading scales (eg, total reading: χ2 = 17.96, P = .006), in which the highest modality HRT group (mean [M] =119.87) outperformed the untreated group (M = 99.88). In the postnatal analysis, we observed a significant effect of treatment on basic skills (P = .01). Despite equal HRT status, males with FLDs (M = 105.79) exhibited reduced total reading skills compared with those in the no FLD group (P = 0.0006). CONCLUSION: Our findings in this pilot study reveal that the most optimal reading trajectory is associated with a prenatal diagnosis, absence of FLDs, and the highest modality HRT.

The behavioral profile of 49,XXXXY and the potential impact of testosterone replacement therapy.

PURPOSE: 49,XXXXY (1:85,000-100,000) is a rare sex chromosome aneuploidy that often presents with complex musculoskeletal abnormalities, decreased cognitive capabilities, speech and language dysfunction, and behavioral complications. Hormonal replacement therapy, or testosterone replacement therapy, is associated with improved neurodevelopmental and behavioral outcomes in males with 49,XXXXY. Two forms of testosterone replacement therapy, early hormonal treatment (EHT) and hormonal booster therapy (HBT), are associated with improved neurodevelopmental and behavioral outcomes in these boys. This study investigates the impact of EHT and HBT on behavioral symptoms in males with 49,XXXXY. METHODS: A total of 59 individuals were divided into 4 groups: 19 no testosterone (no-T), 23 EHT, 6 HBT, and 11 EHT and HBT. An analysis of variance examined group differences on the Child Behavior Checklist and the Behavior Rating Inventory of Executive Function ranging from 5 to 18 years. RESULTS: Although no differences were identified on the Behavior Rating Inventory of Executive Function, the 3 hormonal replacement therapy groups presented with decreased complications on numerous variables on the Child Behavior Checklist; these include somatic complaints (P = .0095), somatic problems (P = .041), internalizing problems (P = .034), externalizing problems (P = .0001), and withdrawn/depression (P = .025). CONCLUSION: This study presents evidence that HBT may be a beneficial treatment for individuals with 49,XXXXY.

A longitudinal perspective of hormone replacement therapies (HRTs) on neuromotor capabilities in males with 47,XXY (Klinefelter syndrome).

PURPOSE: The purpose of this study was to delineate the effects of variable hormone replacement therapies on neuromotor function in a large cohort of males with 47,XXY from birth to adulthood. METHODS: A total of 270 participants aged 16 days to 17 years 11 months prenatally diagnosed with 47,XXY were assessed by their pediatric endocrinologist and were administered hormone replacement therapies accordingly. Infants and school-aged children with 47,XXY were administered neuromotor assessments during routine neurodevelopmental evaluations. For statistical analysis, participants were segregated on the basis of treatment status. Two-tailed t tests, 1-way analysis of variance, and post hoc analysis determined significant group differences on each assessment. RESULTS: In infants, the early hormonal treatment (EHT) group performed significantly better than the untreated group on fine motor and motor composite domains. In school-aged children, we observed significantly improved scores on fine motor control, coordination, agility, and strength domains among males treated with EHT (or any combination thereof) compared with those who did not receive early treatment. CONCLUSION: The highest treated combination group was associated with the highest neuromotor function, although the EHT group also often performed better than the other groups. This suggests EHT may be essential in promoting long-term optimal neuromotor outcome in males with an additional X.

Fifteen years of urea cycle disorders brain research: Looking back, looking forward.

Urea cycle disorders (UCD) are inherited diseases resulting from deficiency in one of six enzymes or two carriers that are required to remove ammonia from the body. UCD may be associated with neurological damage encompassing a spectrum from asymptomatic/mild to severe encephalopathy, which results in most cases from Hyperammonemia (HA) and elevation of other neurotoxic intermediates of metabolism. Electroencephalography (EEG), Magnetic resonance imaging (MRI) and Proton Magnetic resonance spectroscopy (MRS) are noninvasive measures of brain function and structure that can be used during HA to guide management and provide prognostic information, in addition to being research tools to understand the pathophysiology of UCD associated brain injury. The Urea Cycle Rare disorders Consortium (UCDC) has been invested in research to understand the immediate and downstream effects of hyperammonemia (HA) on brain using electroencephalogram (EEG) and multimodal brain MRI to establish early patterns of brain injury and to track recovery and prognosis. This review highlights the evolving knowledge about the impact of UCD and HA in particular on neurological injury and recovery and use of EEG and MRI to study and evaluate prognostic factors for risk and recovery. It recognizes the work of others and discusses the UCDC's prior work and future research priorities.

The effect of early hormonal treatment (EHT) on expressive and receptive language capabilities in boys with 47,XXY (Klinefelter syndrome) during infancy and early childhood.

PURPOSE: 47,XXY is associated with variable neurodevelopmental outcomes including deficits in expressive and receptive language development. Early hormonal treatment (EHT) has been associated with mitigating some deficiencies in boys with 47,XXY. This study investigates these language capabilities of 47,XXY boys in the first five years of life and the associated effects of EHT on these capabilities. METHODS: One hundred and seventy-five boys with 47,XXY between the ages of 0 and 5 years, 11 months completed neurodevelopmental assessments specific to age examining their expressive and receptive language capabilities. Subjects were grouped by treatment (EHT and No-T) and differences were analyzed. RESULTS: In the age groups of under 12 months, 24-35 months, 36-47 months, and 60-71 months, the EHT group scored significantly higher on expressive language assessments than the No-T group (p = 0.09, p = 0.0002, p = 0.009, and p = 0.02, respectively). In the age groups of under 12 months and 24-35 months, the EHT group scored significantly better on the auditory comprehension domain of the PLS-4/5 (p = 0.02 and p = 0.05, respectively) than the No-T group. CONCLUSION: Study data suggest EHT may be essential in optimizing receptive and expressive language development in 47,XXY boys during early childhood, which is critical in fostering reading skills and later academic success.

Variants in GNAI1 cause a syndrome associated with variable features including developmental delay, seizures, and hypotonia.

PURPOSE: Neurodevelopmental disorders (NDDs) encompass a spectrum of genetically heterogeneous disorders with features that commonly include developmental delay, intellectual disability, and autism spectrum disorders. We sought to delineate the molecular and phenotypic spectrum of a novel neurodevelopmental disorder caused by variants in the GNAI1 gene. METHODS: Through large cohort trio-based exome sequencing and international data-sharing, we identified 24 unrelated individuals with NDD phenotypes and a variant in GNAI1, which encodes the inhibitory Gαi1 subunit of heterotrimeric G-proteins. We collected detailed genotype and phenotype information for each affected individual. RESULTS: We identified 16 unique variants in GNAI1 in 24 affected individuals; 23 occurred de novo and 1 was inherited from a mosaic parent. Most affected individuals have a severe neurodevelopmental disorder. Core features include global developmental delay, intellectual disability, hypotonia, and epilepsy. CONCLUSION: This collaboration establishes GNAI1 variants as a cause of NDDs. GNAI1-related NDD is most often characterized by severe to profound delays, hypotonia, epilepsy that ranges from self-limiting to intractable, behavior problems, and variable mild dysmorphic features.

Evidence of intrauterine growth restriction and growth hormone deficiency in 49,XXXXY syndrome.

49,XXXXY is an X and Y chromosome variation that occurs in 1:85,000 to 1:100,000 live male births. Previous case studies have described boys with this disorder to be shorter than average when compared with boys with only one extra chromosome and with the mean stature in a small cohort reported to range from the seventh to 33rd percentile. The origin behind the possible differences in height between boys with 47,XXY and 49,XXXXY is currently unknown, however one study hypothesized that it was due to a difference in the expression of the SHOX gene. This study reports on the anthropometric measurements of 84 boys with 49,XXXXY. Forty-five percent of children with 49,XXXXY were found to be below the third percentile in height at the time of evaluation. In addition, 7.14% of the cohort were diagnosed and given treatment for growth hormone deficiency (GHD). The analysis of this cohort demonstrates that the below average heights seen throughout childhood in this population potentially begins prenatally and suggests that boys with 49,XXXXY may be at a higher risk for intrauterine growth restriction (IUGR) and GHD. Future research is needed to investigate the etiology of the poor growth in boys with 49,XXXXY and evaluate the incidence of GHD and IUGR in this population.

Speech and language development in children with 49,XXXXY syndrome.

49,XXXXY is the rarest X and Y chromosomal variation and is frequently characterized by expressive and receptive language dysfunction, low muscle tonus, and intellectual deficits. Due to the low incidence of this disorder, comprehensive studies analyzing the specific aspects of the speech and language phenotype in these boys have been uncommon. This is the first in-depth investigation of the speech and language profiles in a large cohort of boys with 49,XXXXY. Based on the clinical judgment of speech and language pathologists, there was an increased incidence (91.8%) of Childhood Apraxia of Speech (CAS), which has not been previously described in this disorder. In preschool boys, some significant differences were demonstrated between boys who received early hormonal treatment (n = 16) and untreated boys (n = 4) on the language scales (p = .047) on the Bayley Scales of Infants and Toddlers, as well as significant differences between treated (n = 13) and untreated boys (n = 8) on the Expressive One Word Picture Vocabulary Test (p = .008). No significant differences between treatment groups were found in school age children, however, treated groups demonstrated less discrepancies between expressive and receptive language. More research and larger samples are needed to determine the extent of the impact of testosterone treatment on boys with 49,XXXXY. This study identifies CAS as a potential explanation for the significant expressive language dysfunction and subsequent behavioral dysfunction. These findings may assist in facilitating more targeted treatment and improved outcomes for boys with 49,XXXXY.

49,XXXXY syndrome: A study of neurological function in this uncommon X and Y chromosomal disorder.

49,XXXXY is a rare chromosomal variation characterized by deficits in motor, language, and cognitive domains. This study reports on the neurological function and dysmorphic features in the largest cohort to date. Seventy-two boys with 49,XXXXY were evaluated on a variety of domains including a neurological examination and neuromotor assessments including the Beery Buktenica Developmental Test of Visual-Motor Integration, Sixth Edition, the Bayley Scales of Infant and Toddler Development, Third Edition (BSID-III), and the Bruininks-Oseretsky Test of Motor Proficiency, Second Edition. Results supported previous literature by describing high occurrences of truncal and extremity hypotonia, which significantly impacts on motor milestones and ambulation in this population. The boys presented with dysmorphic features including epicanthal folds, frontal bossing, and synophrys. Visual perception skills were mildly impaired and cranial nerves were typically intact, however capabilities in motor coordination and fine motor precision were greatly delayed, supporting deficits in refined and controlled hand movements versus widespread visual deficits. Preschool boys treated with testosterone replacement had significantly increased scores when compared to the untreated group on the BSID-III Psychomotor Development Index, further supporting previous research indicating that testosterone replacement may have a positive impact on neurodevelopmental outcomes in males with additional X chromosomes. Boys with 49,XXXXY may benefit from hormonal treatment in conjunction with early intervention services to address their significant motor deficits.

Neurocognitive development and capabilities in boys with 49,XXXXY syndrome.

49,XXXXY was previously associated with profound to severe intellectual deficits. However, prior research papers on the cognitive profiles of this population were confounded by small samples sizes, wide age spreads, and incomplete histories of testosterone replacement therapy. This study is the first comprehensive, international investigation of the neurocognitive aspects of 49,XXXXY, and the potential effects of biological treatment on this profile. Sixty-seven boys from infancy to 11 years of age were enrolled in this longitudinal study, with the majority of boys postnatally diagnosed though chromosomal analysis. These boys received a comprehensive neurocognitive evaluation tailored to specific language-based deficits and cognitive challenges. Results revealed higher neurocognitive capacities, both verbally and nonverbally, than previously reported in this disorder. Infant boys with 49,XXXXY who received early hormonal therapy (EHT) had significantly higher scores on the cognitive domain of the Bayley Scales of Infant Development than untreated infants (p = .013). In addition, treated school-aged participants had significantly better scaled scores than untreated boys in form completion (p = .042), a task that requires deductive reasoning, on nonverbal testing on the Leiter International Performance Scales. This study indicates greater cognitive capacities with a wide range of abilities in the child with 49,XXXXY, thus warranting further investigation to identify and understand the critical influences on the etiology and the variability of those capacities.

Musculoskeletal abnormalities in a large international cohort of boys with 49,XXXXY.

49,XXXXY is the rarest X and Y chromosomal variation, with an incidence of 1 in 80,000-100,000 live male births and has been associated with numerous musculoskeletal abnormalities. Data was collected from an international cohort of boys with 49,XXXXY over 10 years. Children were evaluated by a multidisciplinary team consisting of a pediatric orthopedist, a neurogeneticist, a neurodevelopmentalist, and two physical therapists. Increased rates of torticollis (32.4%), hamstring tightness (42%), radioulnar synostosis (67.6%), pes planus (65.2%), and other foot abnormalities (86.9%) were observed. Several anomalies increased with age, specifically hamstring tightness, kyphosis, and scoliosis. The elucidation of the orthopedic profile of this population is necessary in order to provide healthcare providers with current medical information. This research further supports the necessity for the comprehensive multidisciplinary treatment of boys with 49,XXXXY.

Differentiating Moebius syndrome and other congenital facial weakness disorders with electrodiagnostic studies.

INTRODUCTION: Congenital facial weakness (CFW) can result from facial nerve paresis with or without other cranial nerve and systemic involvement, or generalized neuropathic and myopathic disorders. Moebius syndrome is one type of CFW. In this study we explored the utility of electrodiagnostic studies (EDx) in the evaluation of individuals with CFW. METHODS: Forty-three subjects enrolled prospectively into a dedicated clinical protocol and had EDx evaluations, including blink reflex and facial and peripheral nerve conduction studies, with optional needle electromyography. RESULTS: MBS and hereditary congenital facial paresis (HCFP) subjects had low-amplitude cranial nerve 7 responses without other neuropathic or myopathic findings. Carriers of specific pathogenic variants in TUBB3 had, in addition, a generalized sensorimotor axonal polyneuropathy with demyelinating features. Myopathic findings were detected in individuals with Carey-Fineman-Ziter syndrome, myotonic dystrophy, other undefined myopathies, or CFW with arthrogryposis, ophthalmoplegia, and other system involvement. DISCUSSION: EDx in CFW subjects can assist in characterizing the underlying pathogenesis, as well as guide diagnosis and genetic counseling.

Neuromonitoring in Rare Disorders of Metabolism.

Inborn errors of metabolism (IEM) are a unique class of genetic diseases due to mutations in genes involved in key metabolic pathways. The combined incidence of IEM has been estimated to be as high as 1:1000. Urea Cycle disorders (UCD), one class of IEM, can present with cerebral edema and represent a possible target to explore the utility of different neuromonitoring techniques during an hyperammonemic crisis. The last two decades have brought advances in the early identification and comprehensive management of UCD, including further understanding of neuroimaging patterns associated with neurocognitive function. Nonetheless, very important questions remain about the potential acute neurotoxic effects of hyperammonemia to better understand how to treat and prevent secondary brain injury. In this review, we describe existing neuromonitoring techniques that have been used in rare metabolic disorders to assess and allow amelioration of ongoing brain injury. Directions of future research should be focused on identifying new diagnostic approaches in the management of metabolic crises to optimize care and reduce long term morbidity and mortality in patients with IEM.