Radiation Induced Lumbar Plexopathy (RILP) in Patients of Cancer Cervix Treated by IMRT Technique: A Study of Dosimetry and Clinical Correlation

PURPOSE/OBJECTIVE(S)

To assess the Dosimetric parameters of lumbo sacral plexus in carcinoma cervix patients treated with concurrent chemo-radiation by Intensity modulated radiotherapy (IMRT) technique & to clinically correlate these Dosimetric parameters with the lumbo sacral plexus toxicity.

MATERIALS/METHODS

Total twenty-four patients were included in this study between December 2020 to December 2021. They were all treated by Intensity modulated radiotherapy (IMRT) technique. Radiotherapy dose delivered was 50Gy in 25 fractions at 2Gy/#, it was followed by 3 applications of intracavitary brachytherapy of 7Gy/ fraction each. The lumbo-sacral plexus was delineated according to guidelines given by Sun and Xi et al. No dose constraint was prescribed to the lumbo-sacral plexus prior to the treatment. Magnetic resonance imaging (MRI) of bilateral lumbo-sacral plexus test was done prior to the treatment and 12 months' post treatment. Dose received by the lumbo-sacral plexus was calculated DVH parameters was evaluated. The lumbo-sacral plexus toxicity was assessed by the 10-point questionnaire pre-treatment & post treatment and was compared. Assessment of toxicity was done by RTOG (Radiation Therapy Oncology Group) scoring criteria.

RESULTS

Out of the 24 patients treated, 7 patients had gross nodes which were treated with a boost dose of 60 Gy. Out of these patients 9 patients (37.5%) developed signs and symptoms of radiation induced lumbar plexopathy (RILP). Among these patients, the most common symptom was weakness in the lower limbs followed by impaired leg movement and activities interfering daily activities such as walking, squatting and getting up from the chair. Other positive findings included stiffness, lower limb pain, lower back ache radiating the lateral aspect of the thigh and numbness of the lower limbs. Total prescribed dose to 95% of the planned target volume ranged from 49.2Gy - 61.9 Gy (median - 57 Gy). The mean volume of the LS plexus was 128 cc (range, 92- 143 cc). The mean of the D-max of LS plexus was 56.2 Gy (range, 43.2 Gy- 61.9 Gy). The V30 Gy was received by 84 % of LS plexus, whereas V40, V50, V60 was received by 64 %, 13 % and 4%. The most common significant findings on MRI post treatment were unilateral thickening of the nerve roots followed by hyperintensity in T2 weighted image and STIR sequencing. Mild contrast uptake and edema were present in the nerve roots.

CONCLUSION

Radiation induced lumbar plexopathy (RILP) is one of the late complications after chemoradiotherapy in patients of carcinoma cervix, which is often misdiagnosed or missed on follow up. Therefore, lumbar plexus must be contoured in all pelvic malignancies which are treated by chemoradiotherapy with IMRT technique as it prevents dose dumping in that region. Further studies with longer follow up are needed.

Craniofacial features of POLR3-related leukodystrophy caused by biallelic variants in POLR3A, POLR3B and POLR1C

BACKGROUND

RNA polymerase III-related or 4H leukodystrophy (POLR3-HLD) is an autosomal recessive hypomyelinating leukodystrophy characterized by neurological dysfunction, hypodontia and hypogonadotropic hypogonadism. The disease is caused by biallelic pathogenic variants in POLR3A, POLR3B, POLR1C or POLR3K. Craniofacial abnormalities reminiscent of Treacher Collins syndrome have been originally described in patients with POLR3-HLD caused by biallelic pathogenic variants in POLR1C. To date, no published studies have appraised in detail the craniofacial features of patients with POLR3-HLD. In this work, the specific craniofacial characteristics of patients with POLR3-HLD associated with biallelic pathogenic variants in POLR3A, POLR3B and POLR1C are described.

METHODS

The craniofacial features of 31 patients with POLR3-HLD were evaluated, and potential genotype-phenotype associations were evaluated.

RESULTS

Various craniofacial abnormalities were recognized in this patient cohort, with each individual presenting at least one craniofacial abnormality. The most frequently identified features included a flat midface (61.3%), a smooth philtrum (58.0%) and a pointed chin (51.6%). In patients with POLR3B biallelic variants, a thin upper lip was frequent. Craniofacial anomalies involving the forehead were most commonly associated with biallelic variants in POLR3A and POLR3B while a higher proportion of patients with POLR1C biallelic variants demonstrated bitemporal narrowing.

CONCLUSION

Through this study, we demonstrated that craniofacial abnormalities are common in patients with POLR3-HLD. This report describes in detail the dysmorphic features of POLR3-HLD associated with biallelic variants in POLR3A, POLR3B and POLR1C.

A comparative study of rectal volume variation in patients with prostate cancer: A tertiary care center study

INTRODUCTION

Every day variations in rectal filling in prostate cancer radiotherapy can significantly alter the delivered dose distribution from what was intended. The goal of this study was to see if the time of treatment delivery affected the rectal filling.

METHODS

This is a retrospective study which included 50 patients with localized prostate cancer treated with volumetric modulated arc therapy (VMAT) to the primary and regional lymph nodes. Cone Beam Computed Tomography (CBCT) image-sets were done for all patient's daily setup verification. The radiation therapist contoured the rectum on all CBCT image sets. The rectal volumes delineated on CBCT and the planning CT image sets were compared. The change in rectal volumes between morning and afternoon treatments were calculated and compared.

RESULTS

A total of 1000 CBCT image sets were obtained on 50 patients in the morning and afternoon. The percentage variation of the CBCT rectal volumes over the planning CT scan was 16.57% in the AM group and 24.35% in the PM group.

CONCLUSION

The percentage change in rectal volume was significantly lesser in AM group compared to PM group and therefore morning treatments may result in dose distribution that is close to the intended dose distribution.

IMPLICATIONS FOR PRACTICE

In prostate cancer radiotherapy our study suggests that a simple technique of changing the time of treatment from afternoon to morning can help to reduce the rectal volume.

Meta-analysis comparing the efficacy of dobutamine versus milrinone in acute decompensated heart failure and cardiogenic shock

Objective

This study aims to evaluate the difference between dobutamine and milrinone in patients presenting with acute decompensated heart failure (AHF).

Background

Inotropes are indicated for treating AHF, especially in patients with concomitant hypoperfusion indicative of cardiogenic shock. However, previous studies have not identified the optimal inotrope. We sought to compare outcomes associated with milrinone versus dobutamine in patients with AHF.

Methods

A systematic literature search was performed to identify relevant trials from inception to August 2021. Our primary outcome of interest was mortality. Analysis was sub-categorized according to subpopulation, including AHF, AHF with cardiogenic shock (AHF-shock), AHF with a bridge to transplantation (AHF-BTT), and AHF with destination therapy (AHF-DT). Summary effects were calculated using a fixed-effects model as risk ratio or mean difference with 95% confidence intervals for all the clinical endpoints.

Results

Ten studies, including one randomized controlled trial with 21,106 patients, were included in the analysis (4918 patients were in the Milrinone group, while 15188 were in the Dobutamine group). Milrinone was associated with a lower risk of mortality in patients with AHF [relative risk (RR) 0.87; confidence interval (CI):0.79–0.97; p<0.05, heterogeneity I2=0%] with event rates of 9.4% vs. 9.8% [number needed to treat (NNT) of 250]. Milrinone was also associated with improved mortality with RR 0.76 (0.79–0.95; p<0.05) in patients with AHF-DT. There was a non-significant trend towards improved mortality in AHF-shock patients. However, AHF-BTT patients had a non-significant trend towards improved mortality with dobutamine. There was no difference between the two strategies for the outcomes of acute kidney injury, initiation of renal replacement therapy, mechanical ventilation, arrhythmias, symptomatic hypotension, and length of hospital stay (LOS) in the overall population. Intensive care unit (ICU) LOS was lower in AHF-shock patients in the milrinone group, whereas dobutamine was associated with a lower length of ICU stay in AHF patients.

Conclusion

The cumulative data comparing milrinone with dobutamine indicate an overall marginal benefit of milrinone compared to dobutamine in the totality of patients with AFH with or without cardiogenic shock, and whether or not they are bridged to transplantation or destination assist device. More appropriately powered prospective studies are needed to identify a conclusive benefit of one inotrope over another.

Funding Acknowledgement

Type of funding sources: None.

Endocrine and Growth Abnormalities in 4H Leukodystrophy Caused by Variants in POLR3A, POLR3B, and POLR1C

CONTEXT

4H or POLR3-related leukodystrophy is an autosomal recessive disorder typically characterized by hypomyelination, hypodontia, and hypogonadotropic hypogonadism, caused by biallelic pathogenic variants in POLR3A, POLR3B, POLR1C, and POLR3K. The endocrine and growth abnormalities associated with this disorder have not been thoroughly investigated to date.

OBJECTIVE

To systematically characterize endocrine abnormalities of patients with 4H leukodystrophy.

DESIGN

An international cross-sectional study was performed on 150 patients with genetically confirmed 4H leukodystrophy between 2015 and 2016. Endocrine and growth abnormalities were evaluated, and neurological and other non-neurological features were reviewed. Potential genotype/phenotype associations were also investigated.

SETTING

This was a multicenter retrospective study using information collected from 3 predominant centers.

PATIENTS

A total of 150 patients with 4H leukodystrophy and pathogenic variants in POLR3A, POLR3B, or POLR1C were included.

MAIN OUTCOME MEASURES

Variables used to evaluate endocrine and growth abnormalities included pubertal history, hormone levels (estradiol, testosterone, stimulated LH and FSH, stimulated GH, IGF-I, prolactin, ACTH, cortisol, TSH, and T4), and height and head circumference charts.

RESULTS

The most common endocrine abnormalities were delayed puberty (57/74; 77% overall, 64% in males, 89% in females) and short stature (57/93; 61%), when evaluated according to physician assessment. Abnormal thyroid function was reported in 22% (13/59) of patients.

CONCLUSIONS

Our results confirm pubertal abnormalities and short stature are the most common endocrine features seen in 4H leukodystrophy. However, we noted that endocrine abnormalities are typically underinvestigated in this patient population. A prospective study is required to formulate evidence-based recommendations for management of the endocrine manifestations of this disorder.

GATAD2B-associated neurodevelopmental disorder (GAND): clinical and molecular insights into a NuRD-related disorder

PURPOSE

Determination of genotypic/phenotypic features of GATAD2B-associated neurodevelopmental disorder (GAND).

METHODS

Fifty GAND subjects were evaluated to determine consistent genotypic/phenotypic features. Immunoprecipitation assays utilizing in vitro transcription-translation products were used to evaluate GATAD2B missense variants' ability to interact with binding partners within the nucleosome remodeling and deacetylase (NuRD) complex.

RESULTS

Subjects had clinical findings that included macrocephaly, hypotonia, intellectual disability, neonatal feeding issues, polyhydramnios, apraxia of speech, epilepsy, and bicuspid aortic valves. Forty-one novelGATAD2B variants were identified with multiple variant types (nonsense, truncating frameshift, splice-site variants, deletions, and missense). Seven subjects were identified with missense variants that localized within two conserved region domains (CR1 or CR2) of the GATAD2B protein. Immunoprecipitation assays revealed several of these missense variants disrupted GATAD2B interactions with its NuRD complex binding partners.

CONCLUSIONS

A consistent GAND phenotype was caused by a range of genetic variants in GATAD2B that include loss-of-function and missense subtypes. Missense variants were present in conserved region domains that disrupted assembly of NuRD complex proteins. GAND's clinical phenotype had substantial clinical overlap with other disorders associated with the NuRD complex that involve CHD3 and CHD4, with clinical features of hypotonia, intellectual disability, cardiac defects, childhood apraxia of speech, and macrocephaly.

Intellectual and Developmental Disabilities Research Centers: A Multidisciplinary Approach to Understand the Pathogenesis of Methyl-CpG Binding Protein 2-related Disorders

Disruptions in the gene encoding methyl-CpG binding protein 2 (MECP2) underlie complex neurodevelopmental disorders including Rett Syndrome (RTT), MECP2 duplication disorder, intellectual disabilities, and autism. Significant progress has been made on the molecular and cellular basis of MECP2-related disorders providing a new framework for understanding how altered epigenetic landscape can derail the formation and refinement of neuronal circuits in early postnatal life and proper neurological function. This review will summarize selected major findings from the past years and particularly highlight the integrated and multidisciplinary work done at eight NIH-funded Intellectual and Developmental Disabilities Research Centers (IDDRC) across the US. Finally, we will outline a path forward with identification of reliable biomarkers and outcome measures, longitudinal preclinical and clinical studies, reproducibility of results across centers as a synergistic effort to decode and treat the pathogenesis of the complex MeCP2 disorders.

Correction: GATAD2B-associated neurodevelopmental disorder (GAND): clinical and molecular insights into a NuRD-related disorder

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Loss-of-function mutations in UDP-Glucose 6-Dehydrogenase cause recessive developmental epileptic encephalopathy

Developmental epileptic encephalopathies are devastating disorders characterized by intractable epileptic seizures and developmental delay. Here, we report an allelic series of germline recessive mutations in UGDH in 36 cases from 25 families presenting with epileptic encephalopathy with developmental delay and hypotonia. UGDH encodes an oxidoreductase that converts UDP-glucose to UDP-glucuronic acid, a key component of specific proteoglycans and glycolipids. Consistent with being loss-of-function alleles, we show using patients' primary fibroblasts and biochemical assays, that these mutations either impair UGDH stability, oligomerization, or enzymatic activity. In vitro, patient-derived cerebral organoids are smaller with a reduced number of proliferating neuronal progenitors while mutant ugdh zebrafish do not phenocopy the human disease. Our study defines UGDH as a key player for the production of extracellular matrix components that are essential for human brain development. Based on the incidence of variants observed, UGDH mutations are likely to be a frequent cause of recessive epileptic encephalopathy.

Disruption of PHF21A causes syndromic intellectual disability with craniofacial anomalies, epilepsy, hypotonia, and neurobehavioral problems including autism

Background

PHF21A has been associated with intellectual disability and craniofacial anomalies based on its deletion in the Potocki-Shaffer syndrome region at 11p11.2 and its disruption in three patients with balanced translocations. In addition, three patients with de novo truncating mutations in PHF21A were reported recently. Here, we analyze genomic data from seven unrelated individuals with mutations in PHF21A and provide detailed clinical descriptions, further expanding the phenotype associated with PHF21A haploinsufficiency.

Methods

Diagnostic trio whole exome sequencing, Sanger sequencing, use of GeneMatcher, targeted gene panel sequencing, and MiSeq sequencing techniques were used to identify and confirm variants. RT-qPCR was used to measure the normal expression pattern of PHF21A in multiple human tissues including 13 different brain tissues. Protein-DNA modeling was performed to substantiate the pathogenicity of the missense mutation.

Results

We have identified seven heterozygous coding mutations, among which six are de novo (not maternal in one). Mutations include four frameshifts, one nonsense mutation in two patients, and one heterozygous missense mutation in the AT Hook domain, predicted to be deleterious and likely to cause loss of PHF21A function. We also found a new C-terminal domain composed of an intrinsically disordered region. This domain is truncated in six patients and thus likely to play an important role in the function of PHF21A, suggesting that haploinsufficiency is the likely underlying mechanism in the phenotype of seven patients. Our results extend the phenotypic spectrum of PHF21A mutations by adding autism spectrum disorder, epilepsy, hypotonia, and neurobehavioral problems. Furthermore, PHF21A is highly expressed in the human fetal brain, which is consistent with the neurodevelopmental phenotype.

Conclusion

Deleterious nonsense, frameshift, and missense mutations disrupting the AT Hook domain and/or an intrinsically disordered region in PHF21A were found to be associated with autism spectrum disorder, epilepsy, hypotonia, neurobehavioral problems, tapering fingers, clinodactyly, and syndactyly, in addition to intellectual disability and craniofacial anomalies. This suggests that PHF21A is involved in autism spectrum disorder and intellectual disability, and its haploinsufficiency causes a diverse neurological phenotype.

Electronic supplementary material

The online version of this article (10.1186/s13229-019-0286-0) contains supplementary material, which is available to authorized users.

Mutation update for the SATB2 gene

SATB2-associated syndrome (SAS) is an autosomal dominant neurodevelopmental disorder caused by alterations in the SATB2 gene. Here we present a review of published pathogenic variants in the SATB2 gene to date and report 38 novel alterations found in 57 additional previously unreported individuals. Overall, we present a compilation of 120 unique variants identified in 155 unrelated families ranging from single nucleotide coding variants to genomic rearrangements distributed throughout the entire coding region of SATB2. Single nucleotide variants predicted to result in the occurrence of a premature stop codon were the most commonly seen (51/120 = 42.5%) followed by missense variants (31/120 = 25.8%). We review the rather limited functional characterization of pathogenic variants and discuss current understanding of the consequences of the different molecular alterations. We present an expansive phenotypic review along with novel genotype-phenotype correlations. Lastly, we discuss current knowledge of animal models and present future prospects. This review should help provide better guidance for the care of individuals diagnosed with SAS.

Corticosteroid-associated lupus pancreatitis: a case series and systematic review of the literature

BACKGROUND

Acute pancreatitis is an uncommon complication that occurs in 0.85% to 4% of patients with systemic lupus erythematosus (SLE). In some patients, it occurs within days to weeks of starting medium-to-high dose corticosteroids. The authors have used the term 'corticosteroid-associated lupus pancreatitis' for these patients, and they report a case series and perform a systematic review of previously published reports.

METHODS

For the purpose of this study, corticosteroid-associated lupus pancreatitis was defined as occurrence of acute pancreatitis in patients with SLE (fulfilling the 1997 ACR), within 3 weeks of starting therapy with medium-to-high dose corticosteroids - either newly initiated or escalated from a lower dose. All patients with SLE admitted in the last 2.5 years in a North Indian university hospital were reviewed, and those with pancreatitis who fulfilled the above criteria were included in the case series. For the systematic review, a PUBMED search using the keywords 'lupus' and 'pancreatitis' was performed, and reports in English were reviewed for an association with corticosteroids.

RESULTS

Among 420 admissions of SLE patients, six patients (1.4%) fulfilled criteria for corticosteroid-associated lupus pancreatitis. All were female, with mean age and disease duration of 19.7 ± 3.3 and 3.8 ± 2.5 years respectively. All had active disease and developed acute pancreatitis within 48-72 hours of newly initiating medium-to-high dose corticosteroids (in three patients) or escalating them to medium-high dose (in three patients). After the development of pancreatitis, corticosteroids were continued in all except one patient. In addition, two patients received pulse methylprednisolone, two received pulse cyclophosphamide and one was started on azathioprine. Three patients died during hospitalization, all with severe pancreatitis. On systematic review, among 451 cases of lupus pancreatitis reported, 23 (5%) fulfilled criteria for 'corticosteroid-associated lupus pancreatitis'. A majority of them had pancreatitis within 3 days of starting treatment with medium-to-high dose corticosteroids. The mortality in these patients was 37.5%.

CONCLUSION

In a small but substantial proportion of patients with lupus who develop pancreatitis, it occurs within days to weeks of starting medium-to-high dose corticosteroids. Many of these patients continue to receive corticosteroids, and some receive more aggressive immunosuppression. However, they have significant mortality, and further studies are required to identify appropriate treatment in this subgroup of patients.

Natural History of Vanishing White Matter

OBJECTIVE

To comprehensively describe the natural history of vanishing white matter (VWM), aiming at improving counseling of patients/families and providing natural history data for future therapeutic trials.

METHODS

We performed a longitudinal multicenter study among 296 genetically confirmed VWM patients. Clinical information was obtained via disease-specific clinical questionnaire, Health Utilities Index and Guy's Neurological Disability Scale assessments, and chart review.

RESULTS

First disease signs occurred at a median age of 3 years (mode = 2 years, range = before birth to 54 years); 60% of patients were symptomatic before the age of 4 years. The nature of the first signs varied for different ages of onset. Overall, motor problems were the most common presenting sign, especially in children. Adolescent and adult onset patients were more likely to exhibit cognitive problems early after disease onset. One hundred two patients were deceased. Multivariate Cox regression analysis revealed a positive relation between age at onset and both preservation of ambulation and survival. Absence of stress-provoked episodes and absence of seizures predicted more favorable outcome. In patients with onset before 4 years, earlier onset was associated with more severe disability and higher mortality. For onset from 4 years on, disease course was generally milder, with a wide variation in severity. There were no significant differences for sex or for the 5 eIF2B gene groups. The results confirm the presence of a genotype-phenotype correlation.

INTERPRETATION

The VWM disease spectrum consists of a continuum with extremely wide variability. Age at onset is a strong predictor for disease course. Ann Neurol 2018;84:274-288.

Truncating Variants in NAA15 Are Associated with Variable Levels of Intellectual Disability, Autism Spectrum Disorder, and Congenital Anomalies

N-alpha-acetylation is a common co-translational protein modification that is essential for normal cell function in humans. We previously identified the genetic basis of an X-linked infantile lethal Mendelian disorder involving a c.109T>C (p.Ser37Pro) missense variant in NAA10, which encodes the catalytic subunit of the N-terminal acetyltransferase A (NatA) complex. The auxiliary subunit of the NatA complex, NAA15, is the dimeric binding partner for NAA10. Through a genotype-first approach with whole-exome or genome sequencing (WES/WGS) and targeted sequencing analysis, we identified and phenotypically characterized 38 individuals from 33 unrelated families with 25 different de novo or inherited, dominantly acting likely gene disrupting (LGD) variants in NAA15. Clinical features of affected individuals with LGD variants in NAA15 include variable levels of intellectual disability, delayed speech and motor milestones, and autism spectrum disorder. Additionally, mild craniofacial dysmorphology, congenital cardiac anomalies, and seizures are present in some subjects. RNA analysis in cell lines from two individuals showed degradation of the transcripts with LGD variants, probably as a result of nonsense-mediated decay. Functional assays in yeast confirmed a deleterious effect for two of the LGD variants in NAA15. Further supporting a mechanism of haploinsufficiency, individuals with copy-number variant (CNV) deletions involving NAA15 and surrounding genes can present with mild intellectual disability, mild dysmorphic features, motor delays, and decreased growth. We propose that defects in NatA-mediated N-terminal acetylation (NTA) lead to variable levels of neurodevelopmental disorders in humans, supporting the importance of the NatA complex in normal human development.

De novo PHIP-predicted deleterious variants are associated with developmental delay, intellectual disability, obesity, and dysmorphic features

Using whole-exome sequencing, we have identified novel de novo heterozygous pleckstrin homology domain-interacting protein (PHIP) variants that are predicted to be deleterious, including a frameshift deletion, in two unrelated patients with common clinical features of developmental delay, intellectual disability, anxiety, hypotonia, poor balance, obesity, and dysmorphic features. A nonsense mutation in PHIP has previously been associated with similar clinical features. Patients with microdeletions of 6q14.1, including PHIP, have a similar phenotype of developmental delay, intellectual disability, hypotonia, and obesity, suggesting that the phenotype of our patients is a result of loss-of-function mutations. PHIP produces multiple protein products, such as PHIP1 (also known as DCAF14), PHIP, and NDRP. PHIP1 is one of the multiple substrate receptors of the proteolytic CUL4-DDB1 ubiquitin ligase complex. CUL4B deficiency has been associated with intellectual disability, central obesity, muscle wasting, and dysmorphic features. The overlapping phenotype associated with CUL4B deficiency suggests that PHIP mutations cause disease through disruption of the ubiquitin ligase pathway.

Neurodevelopmental Disorders Caused by De Novo Variants in KCNB1 Genotypes and Phenotypes

Importance

Knowing the range of symptoms seen in patients with a missense or loss-of-function variant in KCNB1 and how these symptoms correlate with the type of variant will help clinicians with diagnosis and prognosis when treating new patients.

Objectives

To investigate the clinical spectrum associated with KCNB1 variants and the genotype-phenotype correlations.

Design, Setting, and Participants

This study summarized the clinical and genetic information of patients with a presumed pathogenic variant in KCNB1. Patients were identified in research projects or during clinical testing. Information on patients from previously published articles was collected and authors contacted if feasible. All patients were seen at a clinic at one of the participating institutes because of presumed genetic disorder. They were tested in a clinical setting or included in a research project.

Main Outcomes and Measures

The genetic variant and its inheritance and information on the patient's symptoms and characteristics in a predefined format. All variants were identified with massive parallel sequencing and confirmed with Sanger sequencing in the patient. Absence of the variant in the parents could be confirmed with Sanger sequencing in all families except one.

Results

Of 26 patients (10 female, 15 male, 1 unknown; mean age at inclusion, 9.8 years; age range, 2-32 years) with developmental delay, 20 (77%) carried a missense variant in the ion channel domain of KCNB1, with a concentration of variants in region S5 to S6. Three variants that led to premature stops were located in the C-terminal and 3 in the ion channel domain. Twenty-one of 25 patients (84%) had seizures, with 9 patients (36%) starting with epileptic spasms between 3 and 18 months of age. All patients had developmental delay, with 17 (65%) experiencing severe developmental delay; 14 (82%) with severe delay had behavioral problems. The developmental delay was milder in 4 of 6 patients with stop variants and in a patient with a variant in the S2 transmembrane element rather than the S4 to S6 region.

Conclusions and Relevance

De novo KCNB1 missense variants in the ion channel domain and loss-of-function variants in this domain and the C-terminal likely cause neurodevelopmental disorders with or without seizures. Patients with presumed pathogenic variants in KCNB1 have a variable phenotype. However, the type and position of the variants in the protein are (imperfectly) correlated with the severity of the disorder.

Randomized open-label trial of dextromethorphan in Rett syndrome

OBJECTIVE

To determine safety and perform a preliminary assessment of dose-dependent efficacy of dextromethorphan in normalizing electrographic spikes, clinical seizures, and behavioral and cognitive functions in girls with Rett syndrome.

METHODS

We used a prospective randomized, open-label trial in fast metabolizers of dextromethorphan to examine the effect of dextromethorphan on core clinical features of Rett syndrome. Interictal spike activity and clinical seizures were determined using EEG and parent reporting. Cognitive data were obtained using the Mullen Scales of Early Learning and Vineland Adaptive Behavior Scales, while behavioral data were obtained from parent-completed checklists, the Aberrant Behavior Checklist-Community Version, and the Screen for Social Interaction. Anthropometric data were obtained according to the National Health and Nutrition Examination Survey. The Rett Syndrome Severity Scale provided a clinical global impression of the effect of dextromethorphan on clinical severity.

RESULTS

Dextromethorphan is safe for use in 3- to 15-year-old girls with Rett syndrome. Thirty-five girls were treated with 1 of 3 doses of dextromethorphan over a period of 6 months. Statistically significant dose-dependent improvements were seen in clinical seizures, receptive language, and behavioral hyperactivity. There was no significant improvement in global clinical severity as measured by the Rett Syndrome Severity Scale.

CONCLUSIONS

Dextromethorphan is a potent noncompetitive antagonist of the NMDA receptor channel that is safe for use in young girls with Rett syndrome. Preliminary evidence suggests that dextromethorphan may improve some core features of Rett syndrome.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that dextromethorphan at various doses does not change EEG spike counts over 6 months, though precision was limited to exclude an important effect.

Loss-of-Function and Gain-of-Function Mutations in KCNQ5 Cause Intellectual Disability or Epileptic Encephalopathy

KCNQ5 is a highly conserved gene encoding an important channel for neuronal function; it is widely expressed in the brain and generates M-type current. Exome sequencing identified de novo heterozygous missense mutations in four probands with intellectual disability, abnormal neurological findings, and treatment-resistant epilepsy (in two of four). Comprehensive analysis of this potassium channel for the four variants expressed in frog oocytes revealed shifts in the voltage dependence of activation, including altered activation and deactivation kinetics. Specifically, both loss-of-function and gain-of-function KCNQ5 mutations, associated with increased excitability and decreased repolarization reserve, lead to pathophysiology.

Epileptic Encephalopathy Due to BRAT1 Pathogenic Variants

Investigators from Institut für Medizinische Genetik und Humangenetik have highlighted the role of compound heterozygous BRAT1 variants in two German brothers with variable presentations of intractable epilepsy, poor development, postnatal microcephaly, hypertonia, apnea, and infantile/childhood death.

Update on Leukodystrophies: A Historical Perspective and Adapted Definition

Leukodystrophies were defined in the 1980s as progressive genetic disorders primarily affecting myelin of the central nervous system. At that time, a limited number of such disorders and no associated gene defects were known. The majority of the leukodystrophy patients remained without a specific diagnosis. In the following two decades, magnetic resonance imaging pattern recognition revolutionized the field, allowing the definition of numerous novel leukodystrophies. Their genetic defects were usually identified through genetic linkage studies. This process required substantial numbers of cases and many rare disorders remained unclarified. As recently as 2010, 50% of the leukodystrophy patients remained unclassified. Since 2011, whole-exome sequencing has resulted in an exponential increase in numbers of known, distinct, genetically determined, ultrarare leukodystrophies. We performed a retrospective study concerning three historical cohorts of unclassified leukodystrophy patients and found that currently at least 80% of the patients can be molecularly classified. Based on the original definition of the leukodystrophies, numerous defects in proteins important in myelin structure, maintenance, and function were expected. By contrast, a high percentage of the newly identified gene defects affect the housekeeping process of mRNA translation, shedding new light on white matter pathobiology and requiring adaptation of the leukodystrophy definition.

Recent advances in understanding synaptic abnormalities in Rett syndrome

Rett syndrome is an extremely disabling X-linked nervous system disorder that mainly affects girls in early childhood and causes autism-like behavior, severe intellectual disability, seizures, sleep disturbances, autonomic instability, and other disorders due to mutations in the MeCP2 (methyl CpG-binding protein 2) transcription factor. The disorder targets synapses and synaptic plasticity and has been shown to disrupt the balance between glutamate excitatory synapses and GABAergic inhibitory synapses. In fact, it can be argued that Rett syndrome is primarily a disorder of synaptic plasticity and that agents that can correct this imbalance may have beneficial effects on brain development. This review briefly summarizes the link between disrupted synaptic plasticity mechanisms and Rett syndrome and early clinical trials that aim to target these abnormalities to improve the outcome for these severely disabled children.

Heightened Delta Power during Slow-Wave-Sleep in Patients with Rett Syndrome Associated with Poor Sleep Efficiency

Sleep problems are commonly reported in Rett syndrome (RTT); however the electroencephalographic (EEG) biomarkers underlying sleep dysfunction are poorly understood. The aim of this study was to analyze the temporal evolution of quantitative EEG (qEEG) biomarkers in overnight EEGs recorded from girls (2–9 yrs. old) diagnosed with RTT using a non-traditional automated protocol. In this study, EEG spectral analysis identified high delta power cycles representing slow wave sleep (SWS) in 8–9h overnight sleep EEGs from the frontal, central and occipital leads (AP axis), comparing age-matched girls with and without RTT. Automated algorithms quantitated the area under the curve (AUC) within identified SWS cycles for each spectral frequency wave form. Both age-matched RTT and control EEGs showed similar increasing trends for recorded delta wave power in the EEG leads along the antero-posterior (AP). RTT EEGs had significantly fewer numbers of SWS sleep cycles; therefore, the overall time spent in SWS was also significantly lower in RTT. In contrast, the AUC for delta power within each SWS cycle was significantly heightened in RTT and remained heightened over consecutive cycles unlike control EEGs that showed an overnight decrement of delta power in consecutive cycles. Gamma wave power associated with these SWS cycles was similar to controls. However, the negative correlation of gamma power with age (r = -.59; p<0.01) detected in controls (2–5 yrs. vs. 6–9 yrs.) was lost in RTT. Poor % SWS (i.e., time spent in SWS overnight) in RTT was also driven by the younger age-group. Incidence of seizures in RTT was associated with significantly lower number of SWS cycles. Therefore, qEEG biomarkers of SWS in RTT evolved temporally and correlated significantly with clinical severity.

Clinical spectrum of 4H leukodystrophy caused by POLR3A and POLR3B mutations

OBJECTIVE

To study the clinical and radiologic spectrum and genotype-phenotype correlation of 4H (hypomyelination, hypodontia, hypogonadotropic hypogonadism) leukodystrophy caused by mutations in POLR3A or POLR3B.

METHODS

We performed a multinational cross-sectional observational study of the clinical, radiologic, and molecular characteristics of 105 mutation-proven cases.

RESULTS

The majority of patients presented before 6 years with gross motor delay or regression. Ten percent had an onset beyond 10 years. The disease course was milder in patients with POLR3B than in patients with POLR3A mutations. Other than the typical neurologic, dental, and endocrine features, myopia was seen in almost all and short stature in 50%. Dental and hormonal findings were not invariably present. Mutations in POLR3A and POLR3B were distributed throughout the genes. Except for French Canadian patients, patients from European backgrounds were more likely to have POLR3B mutations than other populations. Most patients carried the common c.1568T>A POLR3B mutation on one allele, homozygosity for which causes a mild phenotype. Systematic MRI review revealed that the combination of hypomyelination with relative T2 hypointensity of the ventrolateral thalamus, optic radiation, globus pallidus, and dentate nucleus, cerebellar atrophy, and thinning of the corpus callosum suggests the diagnosis.

CONCLUSIONS

4H is a well-recognizable clinical entity if all features are present. Mutations in POLR3A are associated with a more severe clinical course. MRI characteristics are helpful in addressing the diagnosis, especially if patients lack the cardinal non-neurologic features.

De novo KCNB1 mutations in epileptic encephalopathy

OBJECTIVE

Numerous studies have demonstrated increased load of de novo copy number variants or single nucleotide variants in individuals with neurodevelopmental disorders, including epileptic encephalopathies, intellectual disability, and autism.

METHODS

We searched for de novo mutations in a family quartet with a sporadic case of epileptic encephalopathy with no known etiology to determine the underlying cause using high-coverage whole exome sequencing (WES) and lower-coverage whole genome sequencing. Mutations in additional patients were identified by WES. The effect of mutations on protein function was assessed in a heterologous expression system.

RESULTS

We identified a de novo missense mutation in KCNB1 that encodes the KV 2.1 voltage-gated potassium channel. Functional studies demonstrated a deleterious effect of the mutation on KV 2.1 function leading to a loss of ion selectivity and gain of a depolarizing inward cation conductance. Subsequently, we identified 2 additional patients with epileptic encephalopathy and de novo KCNB1 missense mutations that cause a similar pattern of KV 2.1 dysfunction.

INTERPRETATION

Our genetic and functional evidence demonstrate that KCNB1 mutation can result in early onset epileptic encephalopathy. This expands the locus heterogeneity associated with epileptic encephalopathies and suggests that clinical WES may be useful for diagnosis of epileptic encephalopathies of unknown etiology.

Novel TUBB4A mutations and expansion of the neuroimaging phenotype of hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC)

Hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC) has recently been associated with a single heterozygous p.D249N mutation in TUBB4A. We describe two novel mutations in this gene. A p.C239F mutation was found in one of the originally described H-ABC patients, for whom we provide follow-up 11 years after the original publication. The second novel mutation, p.R262H, was found in a patient with a typical clinical presentation for H-ABC, but with a novel neuroimaging phenotype, given the absence of atrophy of the putamen and caudate nucleus despite 7 years of follow-up. The recent recognition of TUBB4A mutations as the underlying etiology of H-ABC will likely lead to the identification of subtler clinical and neuroimaging presentations of this disorder, like in our third patient. Thus mutations in this gene should be suspected in any patient with hypomyelination, regardless of the long-term presence of neostriatal atrophy.