Protocol for combined N-of-1 trials to assess cerebellar neurostimulation for movement disorders in children and young adults with dyskinetic cerebral palsy.

BACKGROUND: Movement and tone disorders in children and young adults with cerebral palsy are a great source of disability. Deep brain stimulation (DBS) of basal ganglia targets has a major role in the treatment of isolated dystonias, but its efficacy in dyskinetic cerebral palsy (DCP) is lower, due to structural basal ganglia and thalamic damage and lack of improvement of comorbid choreoathetosis and spasticity. The cerebellum is an attractive target for DBS in DCP since it is frequently spared from hypoxic ischemic damage, it has a significant role in dystonia network models, and small studies have shown promise of dentate stimulation in improving CP-related movement and tone disorders. METHODS: Ten children and young adults with DCP and disabling movement disorders with or without spasticity will undergo bilateral DBS in the dorsal dentate nucleus, with the most distal contact ending in the superior cerebellar peduncle. We will implant Medtronic Percept, a bidirectional neurostimulator that can sense and store brain activity and deliver DBS therapy. The efficacy of cerebellar DBS in improving quality of life and motor outcomes will be tested by a series of N-of-1 clinical trials. Each N-of-1 trial will consist of three blocks, each consisting of one month of effective stimulation and one month of sham stimulation in a random order with weekly motor and quality of life scales as primary and secondary outcomes. In addition, we will characterize abnormal patterns of cerebellar oscillatory activity measured by local field potentials from the intracranial electrodes related to clinical assessments and wearable monitors. Pre- and 12-month postoperative volumetric structural and functional MRI and diffusion tensor imaging will be used to identify candidate imaging markers of baseline disease severity and response to DBS. DISCUSSION: Our goal is to test a cerebellar neuromodulation therapy that produces meaningful changes in function and well-being for people with CP, obtain a mechanistic understanding of the underlying brain network disorder, and identify physiological and imaging-based predictors of outcomes useful in planning further studies. TRIAL REGISTRATION: ClinicalTrials.gov NCT06122675, first registered November 7, 2023.

De novo and inherited mutations in the X-linked gene CLCN4 are associated with syndromic intellectual disability and behavior and seizure disorders in males and females.

Variants in CLCN4, which encodes the chloride/hydrogen ion exchanger CIC-4 prominently expressed in brain, were recently described to cause X-linked intellectual disability and epilepsy. We present detailed phenotypic information on 52 individuals from 16 families with CLCN4-related disorder: 5 affected females and 2 affected males with a de novo variant in CLCN4 (6 individuals previously unreported) and 27 affected males, 3 affected females and 15 asymptomatic female carriers from 9 families with inherited CLCN4 variants (4 families previously unreported). Intellectual disability ranged from borderline to profound. Behavioral and psychiatric disorders were common in both child- and adulthood, and included autistic features, mood disorders, obsessive-compulsive behaviors and hetero- and autoaggression. Epilepsy was common, with severity ranging from epileptic encephalopathy to well-controlled seizures. Several affected individuals showed white matter changes on cerebral neuroimaging and progressive neurological symptoms, including movement disorders and spasticity. Heterozygous females can be as severely affected as males. The variability of symptoms in females is not correlated with the X inactivation pattern studied in their blood. The mutation spectrum includes frameshift, missense and splice site variants and one single-exon deletion. All missense variants were predicted to affect CLCN4's function based on in silico tools and either segregated with the phenotype in the family or were de novo. Pathogenicity of all previously unreported missense variants was further supported by electrophysiological studies in Xenopus laevis oocytes. We compare CLCN4-related disorder with conditions related to dysfunction of other members of the CLC family.

Mutations in PNPLA6 are linked to photoreceptor degeneration and various forms of childhood blindness.

Blindness due to retinal degeneration affects millions of people worldwide, but many disease-causing mutations remain unknown. PNPLA6 encodes the patatin-like phospholipase domain containing protein 6, also known as neuropathy target esterase (NTE), which is the target of toxic organophosphates that induce human paralysis due to severe axonopathy of large neurons. Mutations in PNPLA6 also cause human spastic paraplegia characterized by motor neuron degeneration. Here we identify PNPLA6 mutations in childhood blindness in seven families with retinal degeneration, including Leber congenital amaurosis and Oliver McFarlane syndrome. PNPLA6 localizes mostly at the inner segment plasma membrane in photoreceptors and mutations in Drosophila PNPLA6 lead to photoreceptor cell death. We also report that lysophosphatidylcholine and lysophosphatidic acid levels are elevated in mutant Drosophila. These findings show a role for PNPLA6 in photoreceptor survival and identify phospholipid metabolism as a potential therapeutic target for some forms of blindness.

X-linked congenital ptosis and associated intellectual disability, short stature, microcephaly, cleft palate, digital and genital abnormalities define novel Xq25q26 duplication syndrome.

Submicroscopic duplications along the long arm of the X-chromosome with known phenotypic consequences are relatively rare events. The clinical features resulting from such duplications are various, though they often include intellectual disability, microcephaly, short stature, hypotonia, hypogonadism and feeding difficulties. Female carriers are often phenotypically normal or show a similar but milder phenotype, as in most cases the X-chromosome harbouring the duplication is subject to inactivation. Xq28, which includes MECP2 is the major locus for submicroscopic X-chromosome duplications, whereas duplications in Xq25 and Xq26 have been reported in only a few cases. Using genome-wide array platforms we identified overlapping interstitial Xq25q26 duplications ranging from 0.2 to 4.76 Mb in eight unrelated families with in total five affected males and seven affected females. All affected males shared a common phenotype with intrauterine- and postnatal growth retardation and feeding difficulties in childhood. Three had microcephaly and two out of five suffered from epilepsy. In addition, three males had a distinct facial appearance with congenital bilateral ptosis and large protruding ears and two of them showed a cleft palate. The affected females had various clinical symptoms similar to that of the males with congenital bilateral ptosis in three families as most remarkable feature. Comparison of the gene content of the individual duplications with the respective phenotypes suggested three critical regions with candidate genes (AIFM1, RAB33A, GPC3 and IGSF1) for the common phenotypes, including candidate loci for congenital bilateral ptosis, small head circumference, short stature, genital and digital defects.

A novel deletion partly removing the AVP gene causes autosomal recessive inheritance of early-onset neurohypophyseal diabetes insipidus.

Familial neurohypophyseal diabetes insipidus (FNDI) typically presents with age-dependent penetrance and autosomal dominant inheritance caused by missense variations in one allele of the AVP gene encoding the arginine vasopressin (AVP) prohormone. We present the molecular genetic characteristics underlying an unusual form of FNDI occurring with very early onset and seemingly autosomal recessive inheritance. By DNA amplification and sequencing, we identified a novel variant allele of the AVP gene carrying a 10,396 base pair deletion involving the majority of the AVP gene as well as its regulatory sequences in the intergenic region between the AVP and the OXT gene, encoding the oxytocin prohormone. We found two chromosomes carrying the deletion in affected family members and one in unaffected family members suspected to transmit the deleted allele. Whole-genome array analysis confirmed the results and excluded the presence of any additional major pathogenic abnormalities. The deletion is predicted to abolish the transcription of the AVP gene, thus the fact that family members heterozygous for the deletion remain healthy argues, in general, against haploinsufficiency as the pathogenic mechanism FNDI. Accordingly, our data is strong support to the prevailing idea that dominant inheritance of FNDI is due to a dominant-negative effect exerted by variant AVP prohormone.

MLL2 mosaic mutations and intragenic deletion-duplications in patients with Kabuki syndrome.

Kabuki syndrome (KS) is a rare multi-system disorder that can result in a variety of congenital malformations, typical dysmorphism and variable learning disability. It is caused by MLL2 point mutations in the majority of the cases and, rarely by deletions involving KDM6A. Nearly one third of cases remain unsolved. Here, we expand the known genetic basis of KS by presenting five typical patients with the condition, all of whom have novel MLL2 mutation types- two patients with mosaic small deletions, one with a mosaic whole-gene deletion, one with a multi-exon deletion and one with an intragenic multi-exon duplication. We recommend MLL2 dosage studies for all patients with typical KS, where traditional Sanger sequencing fails to identify mutations. The prevalence of such MLL2 mutations in KS may be comparable with deletions involving KDM6A. These findings may be helpful in understanding the mutational mechanism of MLL2 and the disease mechanism of KS.

Familial Kleefstra syndrome due to maternal somatic mosaicism for interstitial 9q34.3 microdeletions.

The Kleefstra syndrome (Online Mendelian Inheritance in Man 607001) is caused by a submicroscopic 9q34.3 deletion or by intragenic euchromatin histone methyl transferase 1 (EHMT1) mutations. So far only de novo occurrence of mutations has been reported, whereas 9q34.3 deletions can be either de novo or caused by complex chromosomal rearrangements or translocations. Here we give the first descriptions of affected parent-to-child transmission of Kleefstra syndrome caused by small interstitial deletions, approximately 200 kb, involving part of the EHMT1 gene. Additional genome-wide array studies in the parents showed the presence of similar deletions in both mothers who only had mild learning difficulties and minor facial characteristics suggesting either variable clinical expression or somatic mosaicism for these deletions. Further studies showed only one of the maternal deletions resulted in significantly quantitative differences in signal intensity on the array between the mother and her child. But by investigating different tissues with additional fluorescent in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) analyses, we confirmed somatic mosaicism in both mothers. Careful clinical and cytogenetic assessments of parents of an affected proband with an (interstitial) 9q34.3 microdeletion are merited for accurate estimation of recurrence risk.

Mutation update for the CSB/ERCC6 and CSA/ERCC8 genes involved in Cockayne syndrome.

Cockayne syndrome is an autosomal recessive multisystem disorder characterized principally by neurological and sensory impairment, cachectic dwarfism, and photosensitivity. This rare disease is linked to mutations in the CSB/ERCC6 and CSA/ERCC8 genes encoding proteins involved in the transcription-coupled DNA repair pathway. The clinical spectrum of Cockayne syndrome encompasses a wide range of severity from severe prenatal forms to mild and late-onset presentations. We have reviewed the 45 published mutations in CSA and CSB to date and we report 43 new mutations in these genes together with the corresponding clinical data. Among the 84 reported kindreds, 52 (62%) have mutations in the CSB gene. Many types of mutations are scattered along the whole coding sequence of both genes, but clusters of missense mutations can be recognized and highlight the role of particular motifs in the proteins. Genotype-phenotype correlation hypotheses are considered with regard to these new molecular and clinical data. Additional cases of molecular prenatal diagnosis are reported and the strategy for prenatal testing is discussed. Two web-based locus-specific databases have been created to list all identified variants and to allow the inclusion of future reports (www.umd.be/CSA/ and www.umd.be/CSB/).

Semi-dominant X-chromosome linked learning disability with progressive ataxia, spasticity and dystonia associated with the novel MECP2 variant p.V122A: akin to the new MECP2 duplication syndrome?

A novel X-chromosome linked phenotype is reported. Three affected males had learning disability in early childhood and subsequently developed progressive ataxia, dystonia, and spasticity with death at ages 9, 14 and 19 years. Two female obligate carriers had learning difficulties with psychosis in one case. A third, possible carrier had learning difficulties and epilepsy. A family study indicates that this inherited syndrome is most likely due to an unreported MECP2 variant, p.V122A, located in the methyl binding domain of the MECP2 protein. The clinical features are similar to those present in the newly reported MECP2 duplication syndrome. Non-progressive neuropsychiatric symptoms in female relatives of a male child with learning disability, ataxia and progressive spasticity may constitute a clue to inherited, MECP2 pathogenesis.

17q21.31 microdeletion syndrome: further expanding the clinical phenotype.

Microdeletions of the 17q21.31 region are associated with hypotonia, oromotor dyspraxia, an apparently characteristic face, moderate learning disability and have an estimated prevalence of approximately 1 in 16,000. Here we report 3 individuals who extend further the phenotypic spectrum observed with microdeletions of the 17q21.31 region. They all have learning disability, hypotonia, and craniofacial dysmorphism in keeping with previous reported cases. One case has iris-choroid coloboma and partial situs inversus, 2 features that are newly recorded phenotype abnormalities. These deletions were detected from a cohort of 600 individuals with learning disability and congenital anomalies, reflecting that 17q21.31 microdeletions are a common finding in such cases. FISH analysis demonstrated that each of the deletions occurred as de novo events. The deleted region in our cases encompasses the previously defined critical region for 17q21.31, and includes CRHR1 and MAPT, putative candidate genes for the 17q21.31 phenotype. The 17q21.31 microdeletion phenotype is perhaps more variable than previously described despite haploinsufficiency for the same genes in many cases.

Cerebro-oculo-facio-skeletal syndrome: three additional cases with CSB mutations, new diagnostic criteria and an approach to investigation.

BACKGROUND: The cerebro-oculo-facio-skeletal syndrome (COFS syndrome) is an autosomal recessive disorder which was initially described in a specific aboriginal population from Manitoba. In recent years, COFS syndrome has been linked in this original population to a defective DNA repair pathway and to a homozygous mutation in the major gene underlying Cockayne syndrome (CSB). However, most reports of suspected COFS syndrome outside this population have not been confirmed at the molecular level, leading to considerable heterogeneity within the syndrome and confusing overlaps between COFS syndrome and other eye and brain disorders. OBJECTIVE: To refine the delineation of the syndrome on genetically proven COFS cases. METHODS: We report the exhaustive clinical, cellular and molecular data of three unrelated COFS patients with mutations in the CSB gene. RESULTS: All three patients present the cardinal features of COFS syndrome including extreme microcephaly, congenital cataracts, facial dysmorphism and arthrogryposis. They also exhibit a predominantly postnatal growth failure, a severe psychomotor retardation, with axial hypotonia and peripheral hypertonia and neonatal feeding difficulties. Fibroblasts from the patients show the same DNA repair defect which can be complemented by transfection of the CSB wild-type cDNA. Five new mutations in the CSB gene have been identified in these patients. CONCLUSIONS: Our data indicate that COFS syndrome represents the most severe end of the Cockayne spectrum. New diagnostic criteria for COFS syndrome are proposed, based on our findings and on the few genetically proven COFS cases from the literature.

Cerebroretinal microangiopathy with calcifications and cysts (CRMCC).

Extensive intracranial calcifications and leukoencephalopathy are seen in both Coats plus and leukoencephalopathy with calcifications and cysts (LCC; Labrune syndrome). Coats plus syndrome is additionally characterized by the presence of bilateral retinal telangiectasia and exudates while LCC shows the progressive formation of parenchymal brain cysts. Despite these apparently distinguishing features, recent evidence suggests that Coats plus and LCC represent the same clinical entity with a common primary pathogenesis involving a small vessel obliterative microangiopathy. Here, we describe eight previously unreported cases, and present an update on one of the original Coats plus patients to highlight the emerging core clinical features of the "cerebroretinal microangiopathy with calcification and cysts" (CRMCC) phenotype.

The molecular basis of the folate-sensitive fragile site FRA11A at 11q13.

We report on the molecular basis of the rare, folate-sensitive fragile site FRA11A in chromosome band 11q13 in a family with cytogenetic expression. Five individuals express the fragile site and one was mentally retarded. Expansion of a polymorphic CGG-repeat located at the 5' end of the C11orf80 gene causes FRA11A. The CGG-repeat elongation coincides with hypermethylation of the adjacent CpG island and subsequent transcriptional silencing of the C11orf80 gene. This gene has no homology with known genes. A relationship between cytogenetic expression of the fragile site and the mental handicap seems unlikely, as FRA11A was found in a mentally retarded patient as well as in phenotypically normal carriers from the same family. However, incomplete penetrance cannot be entirely excluded.

Investigation of global developmental delay.

The investigation of global developmental delay in preschool children varies between centres and between paediatricians. Following a literature search and review of the evidence base, guidelines were developed to assist in the assessment and management of such children presenting to secondary level services. Evidence supporting the use of genetic and biochemical investigations on a screening basis was found, but there was no evidence to support the use of metabolic investigations or neuroimaging in the absence of other positive findings on history or examination. Detailed history and examination are paramount in the assessment of children with global developmental delay. Investigations can be a useful adjunct in determining aetiology. Evidence based guidelines have been developed to assist doctors in the selection of appropriate investigations for this group of children.

CDKL5 mutations cause infantile spasms, early onset seizures, and severe mental retardation in female patients.

OBJECTIVE: To determine the frequency of mutations in CDKL5 in both male and female patients with infantile spasms or early onset epilepsy of unknown cause, and to consider whether the breadth of the reported phenotype would be extended by studying a different patient group. METHODS: Two groups of patients were investigated for CDKL5 mutations. Group 1 comprised 73 patients (57 female, 16 male) referred to Cardiff for CDKL5 analysis, of whom 49 (42 female, 7 male) had epileptic seizure onset in the first six months of life. Group 2 comprised 26 patients (11 female, 15 male) with infantile spasms previously recruited to a clinical trial, the UK Infantile Spasms Study. Where a likely pathogenic mutation was identified, further clinical data were reviewed. RESULTS: Seven likely pathogenic mutations were found among female patients from group 1 with epileptic seizure onset in the first six months of life, accounting for seven of the 42 in this group (17%). No mutations other than the already published mutation were found in female patients from group 2, or in any male patient from either study group. All patients with mutations had early signs of developmental delay and most had made little developmental progress. Further clinical information was available for six patients: autistic features and tactile hypersensitivity were common but only one had suggestive Rett-like features. All had a severe epileptic seizure disorder, all but one of whom had myoclonic jerks. The EEG showed focal or generalised changes and in those with infantile spasms, hypsarrhythmia. Slow frequencies were seen frequently with a frontal or fronto-temporal predominance and high amplitudes. CONCLUSIONS: The spectrum of the epileptic seizure disorder, and associated EEG changes, in those with CDKL5 mutations is broader than previously reported. CDKL5 mutations are a significant cause of infantile spasms and early epileptic seizures in female patients, and of a later intractable seizure disorder, irrespective of whether they have suspected Rett syndrome. Analysis should be considered in these patients in the clinical setting.

Type 1 Stickler syndrome: a histological and ultrastructural study of an untreated globe.

AIMS: To present a histological and ultrastructural study of an untreated globe in a patient with genetically confirmed type 1 Stickler syndrome. METHODS: Histological and electron microscopic examinations were performed on the enucleated globe from the proband of a pedigree with type 1 Stickler syndrome. Linkage analysis was carried out using polymorphic markers flanking the COL2A1 gene and the mutation was identified by direct sequencing. RESULTS: The significant retinal abnormality was incarceration of vitreous collagen within glial strands on the inner surface of an atrophic and gliotic detached retina. The incarcerated collagenous layers contained glial cells and extended from the retina to form strands, some of which contributed to a retrolental membrane. Mutation screening detected a C to T mutation in exon 47 that inserted a premature termination codon into the reading frame of the mRNA. Sequence analysis of three of the four affected children confirmed that they were also heterozygous for the base change. The youngest child's DNA was not analysed. CONCLUSIONS: The study represents the first evidence of abnormal interactions between pathological vitreous collagen and the inner retina in a patient with type 1 Stickler syndrome with a confirmed mutation in the COL2A1 gene.

Coats' plus: a progressive familial syndrome of bilateral Coats' disease, characteristic cerebral calcification, leukoencephalopathy, slow pre- and post-natal linear growth and defects of bone marrow and integument.

In 1988 we reported two sisters with bilateral Coats' disease, sparse hair, dystrophic nails, and primeval splashes of intracranial calcification. We now provide an update on this family documenting the occurrence of skeletal defects comprising abnormal bone marrow, osteopenia, and sclerosis with a tendency to fractures, a mixed cerebellar and extrapyramidal movement disorder, infrequent epileptic seizures, leukodystrophic changes, and postnatal growth failure. Additionally, we present two previously unreported individuals from Ireland and Switzerland with the identical disorder which we designate Coats' plus. Since our original publication a number of other authors have described, frequently as a "new" syndrome, cases with a variable combination of the same features observed in our patients. We review this literature and suggest that the phenotypic overlap with dyskeratosis congenita may provide a clue to the molecular aetiology of this multisystem disorder.

The Southwest of Scotland Structural Chromosomal Abnormalities Database: an assessment of its contribution to genetic counselling in affected families.

AIM: To assess the effect of establishing a genetic database on the provision of genetic counselling to individuals and families with structural chromosomal abnormalities. METHOD: For the four year period 1997-2000, we compared all cytogenetics laboratory records with entries on the database to determine its completeness. We assessed the extent to which families had been followed up, compared these findings with a previous four year period (1977-1980) and sought to discover why some families were not followed up. RESULTS: Of 215 probands identified during 1997-2000, 19 (9%) were not recorded on the register. Approximately one third of families were followed up completely, one third were partially followed up and one third had had no follow-up, for a variety of reasons. In this last group, there was evidence that some had received inadequate or incorrect genetic advice. There was no evidence that the database improved follow-up in families with structural chromosome abnormalities. Over 20 years, there has been a downward trend in the proportion of cases referred to the genetic clinic. CONCLUSIONS: Our register can be used to monitor trends in clinical practice but has had no direct effect on the service provided to patients and their families.

Cleft palate, hypotelorism, and hypospadias: Schilbach-Rott syndrome.

A mother and two sons have cleft palate and facial appearance closely resembling cases described by Schilbach and Rott in 1988. One of the two males has hypospadias and learning disability and, like his mother, is of short stature. The family described by Schilbach and Rott also supports an autosomal dominant inheritance pattern.