Monitoring Nusinersen Treatment Effects in Children with Spinal Muscular Atrophy with Quantitative Muscle MRI

BACKGROUND

Spinal muscular atrophy (SMA) is caused by deficiency of survival motor neuron (SMN) protein. Intrathecal nusinersen treatment increases SMN protein in motor neurons and has been shown to improve motor function in symptomatic children with SMA.

OBJECTIVE

We used quantitative MRI to gain insight in microstructure and fat content of muscle during treatment and to explore its use as biomarker for treatment effect.

METHODS

We used a quantitative MRI protocol before start of treatment and following the 4th and 6th injection of nusinersen in 8 children with SMA type 2 and 3 during the first year of treatment. The MR protocol allowed DIXON, T2 mapping and diffusion tensor imaging acquisitions. We also assessed muscle strength and motor function scores.

RESULTS

Fat fraction of all thigh muscles with the exception of the m. adductor longus increased in all patients during treatment (+3.2%, p = 0.02). WaterT2 showed no significant changes over time (-0.7 ms, p = 0.3). DTI parameters MD and AD demonstrate a significant decrease in the hamstrings towards values observed in healthy muscle.

CONCLUSIONS

Thigh muscles of children with SMA treated with nusinersen showed ongoing fatty infiltration and possible normalization of thigh muscle microstructure during the first year of nusinersen treatment. Quantitative muscle MRI shows potential as biomarker for the effects of SMA treatment strategies.

Longitudinal prospective cohort study to assess peripheral motor function with extensive electrophysiological techniques in patients with Spinal Muscular Atrophy (SMA): the SMA Motor Map protocol

BACKGROUND

Hereditary spinal muscular atrophy (SMA) is a motor neuron disorder with a wide range in severity in children and adults. Two therapies that alter splicing of the Survival Motor Neuron 2 (SMN2) gene, i.e. nusinersen and risdiplam, improve motor function in SMA, but treatment effects vary. Experimental studies indicate that motor unit dysfunction encompasses multiple features, including abnormal function of the motor neuron, axon, neuromuscular junction and muscle fibres. The relative contributions of dysfunction of different parts of the motor unit to the clinical phenotype are unknown. Predictive biomarkers for clinical efficacy are currently lacking. The goals of this project are to study the association of electrophysiological abnormalities of the peripheral motor system in relation to 1) SMA clinical phenotypes and 2) treatment response in patients treated with SMN2-splicing modifiers (nusinersen or risdiplam).

METHODS

We designed an investigator-initiated, monocentre, longitudinal cohort study using electrophysiological techniques ('the SMA Motor Map') in Dutch children (≥ 12 years) and adults with SMA types 1-4. The protocol includes the compound muscle action potential scan, nerve excitability testing and repetitive nerve stimulation test, executed unilaterally at the median nerve. Part one cross-sectionally assesses the association of electrophysiological abnormalities in relation to SMA clinical phenotypes in treatment-naïve patients. Part two investigates the predictive value of electrophysiological changes at two-months treatment for a positive clinical motor response after one-year treatment with SMN2-splicing modifiers. We will include 100 patients in each part of the study.

DISCUSSION

This study will provide important information on the pathophysiology of the peripheral motor system of treatment-naïve patients with SMA through electrophysiological techniques. More importantly, the longitudinal analysis in patients on SMN2-splicing modifying therapies (i.e. nusinersen and risdiplam) intents to develop non-invasive electrophysiological biomarkers for treatment response in order to improve (individualized) treatment decisions.

TRIAL REGISTRATION

NL72562.041.20 (registered at https://www.toetsingonline.nl . 26-03-2020).

Swallowing Problems in Spinal Muscular Atrophy Types 2 and 3: A Clinical, Videofluoroscopic and Ultrasound Study

Background: Spinal muscular atrophy (SMA) is a hereditary motor neuron disorder, characterized by the degeneration of motor neurons and progressive muscle weakness. There is a large variability of disease severity, reflected by the classification of SMA types 1–4. Objective: The aim of this cross-sectional study was to determine the nature of swallowing problems and underlying mechanisms in patients with SMA types 2 and 3, and the relationship between swallowing and mastication problems. Methods: We enrolled patients (aged 13–67 years) with self-reported swallowing and/or mastication problems. We used a questionnaire, the functional oral intake scale, clinical tests (dysphagia limit, and timed test swallowing, the test of mastication and swallowing solids), a videofluoroscopic swallowing study (VFSS), and muscle ultrasound of the bulbar muscles (i.e. digastric, geniohyoid and tongue muscles). Results: Non-ambulant patients (n = 24) had a reduced dysphagia limit (median 13 ml (3–45), and a swallowing rate at the limit of normal (median 10 ml/sec (range 4–25 ml). VFSS revealed piecemeal deglutition and hypo-pharyngeal residue. We found pharyngo-oral regurgitation in fourteen patients (58%), i.e. they transported the residue from the hypopharynx back into the oral cavity and re-swallowed it. Six patients (25%) demonstrated impaired swallowing safety (i.e. PAS >3). Muscle ultrasound revealed an abnormal muscle structure of the submental and tongue muscles. Ambulant patients (n = 3), had a normal dysphagia limit and swallowing rate, but VFSS showed hypo-pharyngeal residue, and muscle ultrasound demonstrated an abnormal echogenicity of the tongue. Swallowing problems were associated with mastication problems (p = 0.001).

Lung function decline preceding chronic respiratory failure in spinal muscular atrophy: a national prospective cohort study

BACKGROUND

Progressive lung function decline, resulting in respiratory failure, is an important complication of spinal muscular atrophy (SMA). The ability to predict the need for mechanical ventilation is important. We assessed longitudinal patterns of lung function prior to chronic respiratory failure in a national cohort of treatment-naïve children and adults with SMA, hypothesizing an accelerated decline prior to chronic respiratory failure.

METHODS

We included treatment-naïve SMA patients participating in a prospective national cohort study if they required mechanical ventilation because of chronic respiratory failure and if lung function test results were available from the years prior to initiation of ventilation. We analyzed Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 s (FEV₁), Peak Expiratory Flow (PEF) and Maximum Expiratory Pressure (PE_max). We studied the longitudinal course using linear mixed-effects models. We compared patients who electively started mechanical ventilation compared to patients who could not be weaned after acute respiratory failure.

RESULTS

We analyzed 385 lung function tests from 38 patients with SMA types 1c-3a. At initiation of ventilation median age was 18.8 years (IQR: 13.2-30.1) and median standardized FVC, FEV₁ and PEF were 28.8% (95% CI: 23.5; 34.2), 28.8% (95% CI: 24.0; 33.7) and 30.0% (95% CI: 23.4; 36.7), with an average annual decline of 1.75% (95% CI: 0.86; 2.66), 1.72% (95% CI: 1.04; 2.40) and 1.65% (95% CI: 0.71; 2.59), respectively. Our data did not support the hypothesis of an accelerated decline prior to initiation of mechanical ventilation. Median PE_max was 35.3 cmH₂O (95% CI: 29.4; 41.2) at initiation of mechanical ventilation and relatively stable in the years preceding ventilation. Median FVC, FEV_1, PEF and PE_max were lower in patients who electively started mechanical ventilation (p < 0.001).

CONCLUSIONS

Patterns of lung function decline cannot predict impending respiratory failure: SMA is characterized by a gradual decline of lung function. We found no evidence for an accelerated deterioration. In addition, PE_max remains low and stable in the years preceding initiation of ventilation. Patients who electively started mechanical ventilation had more restrictive lung function at initiation of ventilation, compared to patients who could not be weaned after surgery or a respiratory tract infection.

Inflammatory markers in cerebrospinal fluid of paediatric spinal muscular atrophy patients receiving nusinersen treatment

Spinal muscular atrophy (SMA) is a progressive motor neuron disease with onset during infancy or early childhood. Recent therapeutic advances targeting the genetic defect that underlies SMA improved survival in patients with infantile onset SMA (type 1) and improved motor function in SMA type 1-3. The most commonly used therapy for SMA, the antisense oligonucleotide nusinersen, is delivered by repeated intrathecal injections. The long-term safety effects of this procedure, however, have not yet been investigated in detail. We here present case reports of three children with SMA in which routine laboratory investigation revealed increased leukocyte counts in cerebrospinal fluid (CSF) collected during the course of nusinersen treatment. To further characterize this observation, we used a multiplex method to analyse a broad spectrum of inflammatory markers in the CSF of these patients. We found that interleukin-10 (IL10) was consistently elevated in CSF with increased leukocyte counts, but other inflammatory markers were not. Based on this analysis we selected 7 markers for further analysis in a cohort of 38 children with SMA and determined their expression during the course of nusinersen therapy. No consistent association was found between levels of inflammatory markers and the duration of nusinersen therapy in individual patients. However, monocyte chemoactive protein 1 (MCP1/CCL2) -a neuroprotective protein secreted by astrocytes and previously associated with SMA- levels increased over the course of nusinersen treatment, indicating a possible neuroprotective mechanism associated with nusinersen therapy. In summary, our findings confirm that repeated intrathecal injections are safe and do not trigger unwanted immune responses.

Randomized double-blind placebo-controlled crossover trial with pyridostigmine in spinal muscular atrophy types 2-4

Hereditary proximal spinal muscular atrophy causes weakness and increased fatigability of repetitive motor functions. The neuromuscular junction is anatomically and functionally abnormal in patients with spinal muscular atrophy. Pharmacological improvement of neuromuscular transmission may therefore represent a promising additional treatment strategy. We conducted a Phase II, monocentre, placebo-controlled, double-blind, cross-over trial with the acetylcholinesterase inhibitor pyridostigmine in treatment-naïve patients with spinal muscular atrophy types 2-4. We investigated the safety and efficacy of pyridostigmine on fatigability and motor function. Each participant received pyridostigmine and a placebo for 8 weeks, in random order. Primary outcomes were the repeated nine-hole peg test for fatigability and motor function measure. Secondary outcomes were patient-reported effects, endurance shuttle test combined scores and adverse events. We included 35 patients. For the repeated nine-hole peg test, the mean difference was 0.17 s/trial (95% confidence interval: -1.17-1.49; P = 0.8), favouring placebo, and for the motor function measure, 0.74% (95% confidence interval: 0.00-1.49; P = 0.05), favouring pyridostigmine. Around 74% of patients reported medium-to-large beneficial effects of pyridostigmine on fatigability, compared with 29.7% in the placebo arm. This was paralleled by a reduced dropout risk of 70% on the endurance shuttle test combined scores (hazard ratio: 0.30; 95% confidence interval: 0.15-0.58) under pyridostigmine. Adverse events, mostly mild and self-limiting, occurred more frequently under pyridostigmine. No serious adverse events related to the study medication were observed. Patients with spinal muscular atrophy tolerated pyridostigmine well. There were no significant differences in primary outcomes, but the self-reported reduction of fatigability and improved endurance shuttle test combined score performance suggest that pyridostigmine may be useful as an additional therapy to survival motor neuron-augmenting drugs. Trial registration number: EudraCT: 2011-004369-34, NCT02941328.

Population-based assessment of nusinersen efficacy in children with spinal muscular atrophy: a 3-year follow-up study

Nusinersen (Spinraza®) improves survival of infants with hereditary proximal spinal muscular atrophy and motor function in children up to 12 years. Population-based assessments of treatment efficacy are limited and confined to select cohorts of patients. We performed a nationwide, population-based, single-centre cohort study in children with spinal muscular atrophy younger than 9.5 years at start of treatment in line with reimbursement criteria in the Netherlands. We assessed age-relevant motor function scores, the need for tube feeding, hours of ventilatory support and documented adverse events. We used linear mixed modelling to assess treatment effects. We compared motor function during treatment with natural history data and to individual trajectories of muscle strength and motor function before the start of treatment. We included 71 out of 72 Dutch children who were treated (median age 54 months; range 0–117) and followed them for a median of 38 months (range 5–52). We observed improvement of motor function in 72% and stabilization in another 18% of the symptomatic children, which differed from the natural disease course in a matched cohort of which we had previously collected natural history data. Longitudinal analysis showed that motor function improved up to a median of 24 months (range 12–30) of treatment after which it stabilized. Shorter disease duration at start of treatment resulted in better treatment efficacy (P < 0.01). Sixteen children (23%) achieved new motor milestones. Bulbar and respiratory function did not improve significantly during treatment. In 15 patients from whom treatment-naïve data were available, the pre-treatment trajectory of motor function decline changed to stabilization or improvement after the start of treatment. We documented 82 adverse events after 934 injections (9%) in 45 patients. None of the adverse events led to treatment discontinuation. Intrathecal nusinersen treatment is safe and improves or stabilizes motor function in 90% of young children with spinal muscular atrophy types 1c–3a. We did not observe improvement of respiratory and bulbar functions.

Genetic, biochemical, and clinical spectrum of patients with mitochondrial trifunctional protein deficiency identified after the introduction of newborn screening in the Netherlands

Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is included in many newborn screening (NBS) programs. Acylcarnitine-based NBS for LCHADD not only identifies LCHADD, but also the other deficiencies of the mitochondrial trifunctional protein (MTP), a multi-enzyme complex involved in long-chain fatty acid β-oxidation. Besides LCHAD, MTP harbors two additional enzyme activities: long-chain enoyl-CoA hydratase (LCEH) and long-chain ketoacyl-CoA thiolase (LCKAT). Deficiency of one or more MTP activities causes generalized MTP deficiency (MTPD), LCHADD, LCEH deficiency (not yet reported), or LCKAT deficiency (LCKATD). To gain insight in the outcomes of MTP-deficient patients diagnosed after the introduction of NBS for LCHADD in the Netherlands, a retrospective evaluation of genetic, biochemical, and clinical characteristics of MTP-deficient patients, identified since 2007, was carried out. Thirteen patients were identified: seven with LCHADD, five with MTPD, and one with LCKATD. All LCHADD patients (one missed by NBS, clinical diagnosis) and one MTPD patient (clinical diagnosis) were alive. Four MTPD patients and one LCKATD patient developed cardiomyopathy and died within 1 month and 13 months of life, respectively. Surviving patients did not develop symptomatic hypoglycemia, but experienced reversible cardiomyopathy and rhabdomyolysis. Five LCHADD patients developed subclinical neuropathy and/or retinopathy. In conclusion, patient outcomes were highly variable, stressing the need for accurate classification of and discrimination between the MTP deficiencies to improve insight in the yield of NBS for LCHADD. NBS allowed the prevention of symptomatic hypoglycemia, but current treatment options failed to treat cardiomyopathy and prevent long-term complications. Moreover, milder patients, who might benefit from NBS, were missed due to normal acylcarnitine profiles.

Impaired activity of the fusogenic micropeptide Myomixer causes myopathy resembling Carey-Fineman-Ziter syndrome

Skeletal muscle fibers contain hundreds of nuclei, which increase the overall transcriptional activity of the tissue and perform specialized functions. Multinucleation occurs through myoblast fusion, mediated by the muscle fusogens Myomaker (MYMK) and Myomixer (MYMX). We describe a human pedigree harboring a recessive truncating variant of the MYMX gene that eliminates an evolutionarily conserved extracellular hydrophobic domain of MYMX, thereby impairing fusogenic activity. Homozygosity of this human variant resulted in a spectrum of abnormalities that mimicked the clinical presentation of Carey-Fineman-Ziter syndrome (CFZS), caused by hypomorphic MYMK variants. Myoblasts generated from patient-derived induced pluripotent stem cells displayed defective fusion, and mice bearing the human MYMX variant died perinatally due to muscle abnormalities. In vitro assays showed that the human MYMX variant conferred minimal cell-cell fusogenicity, which could be restored with CRISPR/Cas9-mediated base editing, thus providing therapeutic potential for this disorder. Our findings identify MYMX as a recessive, monogenic human disease gene involved in CFZS, and provide new insights into the contribution of myoblast fusion to neuromuscular diseases.

'This battle, between your gut feeling and your mind. Try to find the right balance': Parental experiences of children with spinal muscular atrophy during COVID-19 pandemic

AIMS

Parents of children with spinal muscular atrophy (SMA) often struggle with the all-consuming nature of the demands of caring for a child with substantial physical needs. Our aim was to explore experiences, challenges and needs of parents of a child with SMA in a COVID-19 pandemic situation.

METHOD

Nineteen parents of 21 children (15 months to 13 years of age) with SMA types 1-3 participated in semi-structured interviews in June to July 2020. The interviews were analysed using inductive thematic analysis.

RESULTS

Parents mentioned the protection of the health and well-being of the child as the central perspective and driving force during the COVID-19 pandemic. Three subthemes were identified: (1) responsibility, (2) balancing vulnerability and resilience and (3) (in)security. Some parents focused on the positive aspects during the lockdown, such as continuation of nusinersen treatment and family life. Some parents described helpful and positive cognitions to cope with the situation. In general, parents described a need for information with regard to COVID-19 and their child with SMA and a need for discussing their dilemmas and insecurities with a healthcare professional.

INTERPRETATION

Parents put the health and well-being of their children first during the pandemic. From this study, we learned that parents of children with SMA need information and value direct contact with a healthcare professional to share their dilemmas and insecurities. The dialogue can help to empower parents in the conflicts and decisions they have to make during a pandemic.

Natural history of respiratory muscle strength in spinal muscular atrophy: a prospective national cohort study

Background

Respiratory complications are the most important cause of morbidity and mortality in spinal muscular atrophy (SMA). Respiratory muscle weakness results in impaired cough, recurrent respiratory tract infections and eventually can cause respiratory failure. We assessed longitudinal patterns of respiratory muscle strength in a national cohort of treatment-naïve children and adults with SMA, hypothesizing a continued decline throughout life.

Methods

We measured maximal expiratory and inspiratory pressure (PE_max and PI_max), Sniff Nasal inspiratory pressure (SNIP), peak expiratory flow (PEF), and peak cough flow (PCF) in treatment-naïve patients with SMA. We used mixed-models to analyze natural history patterns.

Results

We included 2172 measurements of respiratory muscle function from 80 treatment-naïve patients with SMA types 1c-3b. All outcomes were lower in the more severe phenotypes. Significant differences in PEF were present between SMA types from early ages onwards. PEF decline was linear (1–2%/year). PEF reached values below 80% during early childhood in types 1c-2, and during adolescence in type 3a. PE_max and PI_max were severely lowered in most patients throughout life, with PE_max values abnormally low (i.e. < 80 cmH₂O) in virtually all patients. The PE_max/PI_max ratio was < 1 throughout life in all SMA types, indicating that expiratory muscles were most affected. All but SMA type 3b patients had a lowered PCF. Patients with types 2b and 3a had PCF levels between 160 and 270 L/min, those with type 2a around 160 L/min and patients with type 1c well below 160 L/min. Finally, SNIP was low in nearly all patients, most pronounced in more severely affected patients.

Conclusions

There are clear differences in respiratory muscle strength and its progressive decline between SMA types. We observed lower outcomes in more severe SMA types. Particularly PEF may be a suitable outcome measure for the follow-up of respiratory strength in patients with SMA. PEF declines in a rather linear pattern in all SMA types, with clear differences at baseline. These natural history data may serve as a reference for longer-term treatment efficacy assessments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02227-7.

Mastication in Patients with Spinal Muscular Atrophy Types 2 and 3 is Characterized by Abnormal Efficiency, Reduced Endurance, and Fatigue

Mastication problems can have a negative impact on the intake of food and quality of life. This cross-sectional study characterizes mastication problems using clinical and instrumental assessments in patients with spinal muscular atrophy (SMA) types 2 and 3 with self-reported bulbar problems. We included 27 patients (aged 13–67 years), 18 with SMA type 2 and 9 patients with SMA type 3 (of whom three were still ambulant) and applied a questionnaire, clinical mastication tests (TOMASS and 6-min mastication test), and muscle ultrasound of the mastication muscles. Non-ambulant patients demonstrated inefficient mastication as reflected by median z scores for masticatory cycles (z = 1.8), number of swallows (z = 4.3) and time needed to finish the cracker (z = 3.4), and limited endurance of continuous mastication as demonstrated by the median z scores of the 6-min mastication test (z = − 1.5). Patients reported increased fatigue directly after the 6-min mastication test as well as 5 min after completing the test (p < 0.001; p = 0.003). Reduced maximal mouth opening was associated with mastication problems (p < 0.001). Muscle ultrasound of the mastication muscles showed an abnormal muscle structure in 90% of both ambulant and non-ambulant patients. This study aims to understand the nature and underlying mechanisms of mastication problems in patients with SMA types 2 and 3 with reported bulbar problems.

Prevalence of Bladder and Bowel Dysfunction in Duchenne Muscular Dystrophy Using the Childhood Bladder and Bowel Dysfunction Questionnaire

Introduction: Lower urinary tract symptoms (LUTS) and gastrointestinal (GI) problems are common in Duchenne muscular dystrophy (DMD), but not systematically assessed in regular care. We aimed to determine the prevalence of bladder and bowel dysfunction (BBD) in DMD patients compared with healthy controls (HC). Methods: The Childhood Bladder and Bowel Dysfunction Questionnaire (CBBDQ) based on the International Rome III criteria and the International Children’s Continence Society was filled out by 57 DMD patients and 56 HC. Additionally, possible associations of BBD with, for example, medication use or quality of life were evaluated in an additional questionnaire developed by experts. Results: In 74% of patients versus 56% of HC ≥ 1 LUTS (n.s.) were reported, 68% of patients versus 39% of HC reported ≥1 bowel symptom (p = 0.002) and 53% of patients versus 30% of HC reported combined LUTS and bowel symptoms (p = 0.019). A negative impact of BBD on daily life functioning was reported by 42% of patients. Conclusions: These data underscore that standard screening for BBD is needed and that the CBBDQ could be of added value to optimize DMD care.

Parents' perspectives on nusinersen treatment for children with spinal muscular atrophy

AIM

To gain insight into parents' perspectives about their decision-making process concerning nusinersen treatment for their child, including perceived needs and concerns, and to explore factors that influence this process.

METHOD

This was an exploratory qualitative interview study among parents of children with spinal muscular atrophy types 1 to 3. Data were analysed using inductive thematic analysis.

RESULTS

Nineteen parents of 16 children representing 13 families participated. A wide variety of perspectives was reported ranging from a biomedical approach, which focused on battling the disease, to a holistic approach, which aimed for a good quality of life for their child. The most important factors that helped parents to decide were honest and neutral communication with their physician and access to available information.

INTERPRETATION

It is important physicians understand that there are different perspectives influencing the decision-making process. Physicians should create an environment that allows parents to accept or reject treatment by communicating honestly and openly with them and by discussing both options extensively. Clear information about pros and cons, recent developments in research, and the experiences of other parents should be made available to enable parents to make an informed decision. What this paper adds Parents perceived different needs and concerns about nusinersen treatment, which emphasized individual differences. Parents' perspectives varied from battling the disease to preserving quality of life. Life expectancy, stopping deterioration, and improving quality of life were the perceived benefits of nusinersen treatment. Open communication about the pros and cons of treatment with clinicians facilitated decision-making. Clear and honest information facilitated the alignment of values and goals.

Quantification of disease progression in spinal muscular atrophy with muscle MRI-a pilot study

OBJECTIVES

Quantitative MRI (qMRI) of muscles is a promising tool to measure disease progression or to assess therapeutic effects in neuromuscular diseases. Longitudinal imaging studies are needed to show sensitivity of qMRI in detecting disease progression in spinal muscular atrophy (SMA). In this pilot study we therefore studied one-year changes in quantitative MR parameters in relation to clinical scores.

METHODS

We repeated quantitative 3 T MR analysis of thigh muscles and clinical testing one year after baseline in 10 treatment-naïve patients with SMA, 5 with Type 2 (21.6 ± 7.0 years) and 5 with Type 3 (33.4 ± 11.9 years). MR protocol consisted of Dixon, T₂ mapping and diffusion tensor imaging (DTI). The temporal relation of parameters was examined with a mixed model.

RESULTS

We detected a significant increase in fat fraction (baseline, 38.2% SE 0.6; follow-up, 39.5% SE 0.6; +1.3%, p = 0.001) in all muscles. Muscles with moderate to high fat infiltration at baseline show a larger increase over time (+1.6%, p < 0.001). We did not find any changes in DTI parameters except for low fat-infiltration muscles (m. adductor longus and m. biceps femoris (short head)). The T₂ of muscles decreased from 28.2 ms to 28.0 ms (p = 0.07). Muscle strength and motor function scores were not significantly different between follow-up and baseline.

CONCLUSION

Longitudinal imaging data show slow disease progression in skeletal muscle of the thigh of (young-) adult patients with SMA despite stable strength and motor function scores. Quantitative muscle imaging demonstrates potential as a biomarker for disease activity and monitoring of therapy response.

Feeding and Swallowing Problems in Infants with Spinal Muscular Atrophy Type 1: an Observational Study

BACKGROUND

Infantile hereditary proximal spinal muscular atrophy (SMA) type 1 is characterized by onset in the first 6 months of life and severe and progressive muscle weakness. Dysphagia is a common complication but has not been studied in detail.

OBJECTIVE

To study feeding and swallowing problems in infants with SMA type 1, and to explore the relation between these problems and functional motor scores.

METHODS

We prospectively included 16 infants with SMA type 1 between September 2016 and October 2018. Eleven infants received palliative care and five infants best supportive care in combination with nusinersen. We compiled and used an observation list with feeding related issues and observed feeding sessions during inpatient and outpatient visits. The Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP INTEND) was used as a measure of motor function.

RESULTS

All infants in the palliative care group (median onset of disease 14 days (range 1-56); median inclusion in the study 52 days (range 16-252) demonstrated symptoms of fatigue during feeding and unsafe swallowing. Symptoms were short nursing sessions (10-15 minutes), and not being able to finish the recommended feeding volumes (72%); increased frequency of feeding sessions (55%); coughing when drinking or eating (91%), and wet breathing during and after feeding (64%).Two out of five infants in the nusinersen group (median onset of disease 38 days (range 21-90); inclusion in the study at 63 days (range 3-218) were clinically pre-symptomatic at the start of treatment. The other three infants showed symptoms of fatigue and unsafe swallowing at inclusion in the study. These symptoms initially decreased after the start of the treatment, but (re)appeared in all five infants between the ages of 8 to 12 months, requiring the start tube of feeding. In the same period motor function scores significantly improved (median increase CHOP INTEND 16 points).

CONCLUSION

Impaired feeding and swallowing remain important complications in infants with SMA type 1 after the start of nusinersen. Improvement of motor function does not imply similar gains in bulbar function.

Deep intronic TIMMDC1 variant delays diagnosis of rapidly progressive complex I deficiency

Complex I deficiency is the most common pediatric mitochondrial disease. It can cause a wide range of clinical disorders, including Leigh syndrome. TIMMDC1 encodes an assembly protein of complex I and has been recently associated with early onset mitochondrial disease in three unrelated families. In all three families the same homozygous deep intronic variant was identified leading to inclusion of a new exon resulting in a frameshift and premature stop codon (c.596 + 2146A > G, p.Gly199_Thr200ins5*). Herein, we describe two brothers of Dutch descent, presenting in infancy with hypotonia and respiratory insufficiency and a rapidly progressive and fatal disease course. Laboratory findings and metabolic investigations revealed no specific abnormalities, notably no raised plasma lactate. MRI showed transient lesions in the basal ganglia of brother 1. A muscle biopsy demonstrated complex I deficiency in brother 2. Exome sequencing yielded a novel heterozygous TIMMDC1 variant: c.385C > T, p.(Arg129*). Targeted sequencing revealed the previously published deep intronic variant c.596 + 2146A > G, p.(Gly199_Thr200ins5*) on the second allele which is not detected by exome sequencing. In summary, we present the fourth family with TIMMDC1-related disease, with a novel nonsense variant. This report illustrates the importance of considering mitochondrial disease even when laboratory findings are normal, and the added value of targeted sequencing of introns.

Quantitative MRI of skeletal muscle in a cross-sectional cohort of patients with spinal muscular atrophy types 2 and 3

The aim of this study was to document upper leg involvement in spinal muscular atrophy (SMA) with quantitative MRI (qMRI) in a cross-sectional cohort of patients of varying type, disease severity and age. Thirty-one patients with SMA types 2 and 3 (aged 29.6 [7.6-73.9] years) and 20 healthy controls (aged 37.9 [17.7-71.6] years) were evaluated in a 3 T MRI with a protocol consisting of DIXON, T2 mapping and diffusion tensor imaging (DTI). qMRI measures were compared with clinical scores of motor function (Hammersmith Functional Motor Scale Expanded [HFMSE]) and muscle strength. Patients exhibited an increased fat fraction and fractional anisotropy (FA), and decreased mean diffusivity (MD) and T2 compared with controls (all P < .001). DTI parameters FA and MD manifest stronger effects than can be accounted for the effect of fatty replacement. Fat fraction, FA and MD show moderate correlation with muscle strength and motor function: FA is negatively associated with HFMSE and Medical Research Council sum score (τ = -0.56 and -0.59; both P < .001) whereas for fat fraction values are τ = -0.50 and -0.58, respectively (both P < .001). This study shows that DTI parameters correlate with muscle strength and motor function. DTI findings indirectly indicate cell atrophy and act as a measure independently of fat fraction. Combined these data suggest the potential of muscle DTI in monitoring disease progression and to study SMA pathogenesis in muscle.

Relative hyperventilation in non-ventilated patients with spinal muscular atrophy

Spinal muscular atrophy (SMA) is a relatively common autosomal recessive neuromuscular disorder, characterised by progressive degeneration of spinal cord and bulbar motor neurons. It is caused by survival motor neuron (SMN) protein deficiency, due to homozygous loss of function of the SMN1 gene. Due to the effects of genetic modifiers, SMA displays a broad range in severity. The current clinical classification system distinguishes four types, based on age at onset and acquired motor milestones, i.e. infantile onset without achieving the ability to sit (type 1), childhood onset with the ability to sit but not to walk (type 2), childhood onset with the ability to walk for at least a short period of time (type 3) and adult onset with mild symptoms (type 4) [1, 2]. Disease course is progressive, irrespective of type [3] and patients with SMA type 1, 2 and 3 are at high or moderate risk of developing respiratory insufficiency, which may necessitate initiating mechanical ventilation [4, 5].

Lower ranges of carbon dioxide levels are normal in non-ventilated SMA patients. Physicians should be aware of pending respiratory insufficiency if carbon dioxide levels increase to normal levels in patients with pre-existing low carbon dioxide levelshttps://bit.ly/2Ag7jQ5

Distinct effects on mRNA export factor GANP underlie neurological disease phenotypes and alter gene expression depending on intron content

Defects in the mRNA export scaffold protein GANP, encoded by the MCM3AP gene, cause autosomal recessive early-onset peripheral neuropathy with or without intellectual disability. We extend here the phenotypic range associated with MCM3AP variants, by describing a severely hypotonic child and a sibling pair with a progressive encephalopathic syndrome. In addition, our analysis of skin fibroblasts from affected individuals from seven unrelated families indicates that disease variants result in depletion of GANP except when they alter critical residues in the Sac3 mRNA binding domain. GANP depletion was associated with more severe phenotypes compared with the Sac3 variants. Patient fibroblasts showed transcriptome alterations that suggested intron content-dependent regulation of gene expression. For example, all differentially expressed intronless genes were downregulated, including ATXN7L3B, which couples mRNA export to transcription activation by association with the TREX-2 and SAGA complexes. Our results provide insight into the molecular basis behind genotype-phenotype correlations in MCM3AP-associated disease and suggest mechanisms by which GANP defects might alter RNA metabolism.

Natural history of lung function in spinal muscular atrophy

BACKGROUND

Respiratory muscle weakness is an important feature of spinal muscular atrophy (SMA). Progressive lung function decline is the most important cause of mortality and morbidity in patients. The natural history of lung function in SMA has, however, not been studied in much detail.

RESULTS

We analysed 2098 measurements of lung function from 170 treatment-naïve patients with SMA types 1c-4, aged 4-74 years. All patients are participating in an ongoing population-based prevalence cohort study. We measured Forced Expiratory Volume in 1 s (FEV₁), Forced Vital Capacity (FVC), and Vital Capacity (VC). Longitudinal patterns of lung function were analysed using linear mixed-effects and non-linear models. Additionally, we also assessed postural effects on results of FEV₁ and FVC tests. In early-onset SMA types (1c-3a), we observed a progressive decline of lung function at younger ages with relative stabilisation during adulthood. Estimated baseline values were significantly lower in more severely affected patients: %FEV₁ ranged from 42% in SMA type 1c to 100% in type 3b, %FVC 50 to 109%, and %VC 44 to 96%. Average annual decline rates also differed significantly between SMA types, ranging from - 0.1% to - 1.4% for FEV₁, - 0.2% to - 1.4% for FVC, and + 0.2% to - 1.7% for VC. In contrast to SMA types 1c-3a, we found normal values for all outcomes in later-onset SMA types 3b and 4 throughout life, although with some exceptions and based on limited available data. Finally, we found no important differences in FVC or FEV₁ values measured in either sitting or supine position.

CONCLUSIONS

Our data illustrate the longitudinal course of lung function in patients with SMA, which is characterised by a progressive decline in childhood and stabilisation in early adulthood. The data do not support an additional benefit of measuring FEV₁ or FVC in both sitting and supine position. These data may serve as a reference to assess longer-term outcomes in clinical trials.

Population-based analysis of survival in spinal muscular atrophy

OBJECTIVE

To investigate probabilities of survival and its surrogate, that is, mechanical ventilation, in patients with spinal muscular atrophy (SMA).

METHODS

We studied survival in a population-based cohort on clinical prevalence of genetically confirmed, treatment-naive patients with SMA, stratified for best acquired motor milestone (i.e., none: type 1a/b; head control in supine position or rolling: type 1c; sitting independently: type 2a; standing: type 2b; walking: type 3a/b; adult onset: type 4). We also assessed the need for mechanical ventilation as a surrogate endpoint for survival.

RESULTS

We included 307 patients with a total follow-up of 7,141 person-years. Median survival was 9 days in SMA type 1a, 7.7 months in type 1b, and 17.0 years in type 1c. Patients with type 2a had endpoint-free survival probabilities of 74.2% and 61.5% at ages 40 and 60 years, respectively. Endpoint-free survival of SMA types 2b, 3, and 4 was relatively normal, at least within the first 60 years of life. Patients with SMA types 1c and 2a required mechanical ventilation more frequently and from younger ages compared to patients with milder SMA types. In our cohort, patients ventilated up to 12 h/d progressed not gradually, but abruptly, to ≥16 h/d.

CONCLUSIONS

Shortened endpoint-free survival is an important characteristic of SMA types 1 and 2a, but not types 2b, 3, and 4. For SMA types 1c and 2a, the age at which initiation of mechanical ventilation is necessary may be a more suitable endpoint than the arbitrarily set 16 h/d.

Bulbar Problems Self-Reported by Children and Adults with Spinal Muscular Atrophy

BACKGROUND

Spinal muscular atrophy (SMA) is hereditary motor neuron disorder, characterised by the degeneration of motor neurons and progressive muscle weakness. It is caused by the homozygous loss of function of the survival motor neuron (SMN) 1 gene. SMA shows a wide variability of disease severity.

OBJECTIVE

To investigate self-reported bulbar problems in patients with SMA, and their relationship to age, functional motor scores and active maximum mouth opening.

METHODS

We used the Diagnostic List of Dysphagia and Dysarthria in (pediatric) patients and relevant recent clinical data from the national SMA database.

RESULTS

The 118 included patients with SMA frequently reported jaw problems (34%), fatigue associated with mastication (44%), choking (56%) and intelligibility problems (27%). Jaw, mastication and swallowing problems frequently occurred in combination with each other. There was an increase of reported bulbar problems in patients with SMA type 3a, older than 30 years of age, compared to younger patients of this SMA type.The Hammersmith Functional Motor Scale Expanded scores showed a negligible correlation with jaw and mastication problems, a low negative correlation with swallowing problems and a moderate negative correlation with intelligibility problems. Reduced mouth opening showed a significant, but low correlation with bulbar complaints in patients with SMA type 2.

CONCLUSIONS

Fatigue associated with mastication and swallowing problems were frequently reported complaints. Patients 30 years and older with milder forms of SMA showed an increase of self-reported bulbar problems.

Assessment of motor unit loss in patients with spinal muscular atrophy

OBJECTIVE

To assess motor unit (MU) changes in patients with spinal muscular atrophy (SMA) using compound muscle action potential (CMAP) scans.

METHODS

We performed CMAP scan recordings in median nerves of 24 treatment-naïve patients (median age 39; range 12-75 years) with SMA types 2-4. From each scan, we determined maximum CMAP amplitude (CMAP_max), a motor unit number estimate (MUNE), and D50 which quantifies the largest discontinuities within CMAP scans.

RESULTS

Median CMAP_max was 8.1 mV (range 0.9-14.6 mV), MUNE was 29 (range 6-131), and D50 was 25 (range 2-57). We found a reduced D50 (<25) in patients with normal CMAP_max (n = 12), indicating MU loss and enlarged MUs due to reinnervation. Lower D50 values were associated with decreased MUNE (P < 0.001, r = 0.68, n = 43). CMAP_max, MUNE and D50 values differed between SMA types (P < 0.001). Lower motor function scores were related to patients with lower CMAP_max, MUNE and D50 values (P < 0.001).

CONCLUSIONS

The CMAP scan is an easily applicable technique that is superior to routine assessment of CMAP_max in SMA.

SIGNIFICANCE

The detection of pathological MU changes across the spectrum of SMA may provide important biomarkers for evaluating disease course and monitoring treatment efficacy.

Natural course of scoliosis and lifetime risk of scoliosis surgery in spinal muscular atrophy

Objective

To investigate the natural course of scoliosis and to estimate lifetime probability of scoliosis surgery in spinal muscular atrophy (SMA).

Methods

We analyzed cross-sectional data from 283 patients from our population-based cohort study. Additional longitudinal data on scoliosis progression and spinal surgery were collected from 36 consecutive patients who received scoliosis surgery at our center.

Results

The lifetime probability of receiving scoliosis surgery was ≈80% in SMA types 1c and 2. Patients with type 2 who only learned to sit (type 2a) were significantly younger at time of surgery than those who learned to sit and stand (type 2b). The lifetime risk of surgery was lower in type 3a (40%) and strongly associated with age at loss of ambulation: 71% in patients losing ambulation before 10 years of age vs 22% losing ambulation after the age of 10 years (p = 0.005). In type 3a, preserving the ability to walk 1 year longer corresponded to a 15% decrease in lifetime risk of scoliosis surgery (hazard ratio 0.852, p = 0.017). Scoliosis development was characterized by initial slow progression, followed by acceleration in the 1.5- to 2-year period before surgery.

Conclusion

The lifetime probability of scoliosis surgery is high in SMA types 1c and 2 and depends on age at loss of ambulation in type 3. Motor milestones such as standing that are not part of the standard classification system are of additional predictive value. Our data may act as a reference to assess long-term effects of new SMA-specific therapies.

Validation of a Fast, Robust, Inexpensive, Two-Tiered Neonatal Screening Test algorithm on Dried Blood Spots for Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is one of the leading genetic causes of infant mortality with an incidence of 1:10,000. The recently-introduced antisense oligonucleotide treatment improves the outcome of this disease, in particular when applied at an early stage of progression. The genetic cause of SMA is, in >95% of cases, a homozygous deletion of the survival motor neuron 1 (SMN1) gene, which makes the low-cost detection of SMA cases as part of newborn screening programs feasible. We developed and validated a new SALSA MC002 melting curve assay that detects the absence of the SMN1 exon 7 DNA sequence without detecting asymptomatic carriers and reliably discriminates SMN1 from its genetic homolog SMN2 using crude extracts from newborn screening cards. Melting curve analysis shows peaks specific for both the SMN1 gene and the disease modifying SMN2 homolog. The detection of the SMN2 homolog, of which the only clinically relevant difference from the SMN1 gene is a single nucleotide in exon 7, was only used to confirm a correct reaction in samples that lacked the SMN1 gene, and not for SMN2 quantification. We retrieved 47 DBS samples from children with genetically-confirmed SMA, after informed consent from parents, and 375 controls from the national archive of the Dutch National Institute for Public Health and the Environment (RIVM). The assay correctly identified all anonymized and randomized SMA and control samples (i.e., sensitivity and specificity of 100%), without the detection of carriers, on the three most commonly-used PCR platforms with melting curve analysis. This test's concordance with the second-tier 'golden standard' P021 SMA MLPA test was 100%. Using the new P021-B1 version, crude extracts from DBS cards could also be used to determine the SMN2 copy number of SMA patients with a high level of accuracy. The MC002 test showed the feasibility and accuracy of SMA screening in a neonatal screening program.

Impact of newborn screening for very-long-chain acyl-CoA dehydrogenase deficiency on genetic, enzymatic, and clinical outcomes

Most infants with very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD) identified by newborn screening (NBS) are asymptomatic at the time of diagnosis and remain asymptomatic. If this outcome is due to prompt diagnosis and initiation of therapy, or because of identification of individuals with biochemical abnormalities who will never develop symptoms, is unclear. Therefore, a 10-year longitudinal national cohort study of genetically confirmed VLCADD patients born before and after introduction of NBS was conducted. Main outcome measures were clinical outcome parameters, acyl-CoA dehydrogenase very long chain gene analysis, VLCAD activity, and overall capacity of long-chain fatty acid oxidation (LC-FAO flux) in lymphocytes and cultured skin fibroblasts. Median VLCAD activity in lymphocytes of 54 patients, 21 diagnosed pre-NBS and 33 by NBS was, respectively, 5.4% (95% confidence interval [CI]: 4.0-8.3) and 12.6% (95% CI: 10.7-17.7; P < 0.001) of the reference mean. The median LC-FAO flux was 33.2% (95% CI: 22.8-48.3) and 41% (95% CI: 40.8-68; P < 0.05) of the control mean, respectively. Clinical characteristics in 23 pre-NBS and 37 NBS patients revealed hypoglycemic events in 12 vs 2 patients, cardiomyopathy in 5 vs 4 patients and myopathy in 14 vs 3 patients. All patients with LC-FAO flux <10% developed symptoms. Of the patients with LC-FAO flux >10% 7 out of 12 diagnosed pre-NBS vs none by NBS experienced hypoglycemic events. NBS has a clear beneficial effect on the prevention of hypoglycemic events in patients with some residual enzyme activity, but does not prevent hypoglycemia nor cardiac complications in patients with very low residual enzyme activity. The effect of NBS on prevalence and prevention of myopathy-related complications remains unclear.

Nusinersen in patients older than 7 months with spinal muscular atrophy type 1: A cohort study

OBJECTIVE

To evaluate the safety and clinical efficacy of nusinersen in patients older than 7 months with spinal muscular atrophy type 1 (SMA1).

METHODS

Patients with SMA1 were treated with nusinersen by intrathecal injections as a part of the Expanded Access Program (EAP; NCT02865109). We evaluated patients before treatment initiation (M0) and at 2 months (M2) and 6 months (M6) after treatment initiation. Survival, respiratory, and nutritional data were collected. Motor function was assessed with the modified Hammersmith Infant Neurologic Examination Part 2 (HINE-2) and physiotherapist scales adjusted to patient age (Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders and the Motor Function Measure 20 or 32).

RESULTS

We treated 33 children ranging in age from 8.3 to 113.1 months between December 2016 and May 2017. All patients were alive and were continuing treatment at M6. Median progress on the modified HINE-2 score was 1.5 points after 6 months of treatment (p < 0.001). The need for respiratory support significantly increased over time. There were no statistically significant differences between patients presenting with 2 and those presenting with 3 copies of the survival motor neuron 2 (SMN2) gene.

CONCLUSIONS

Our results are in line with the phase 3 study for nusinersen in patients with SMA1 treated before 7 months of age and indicate that patients benefit from nusinersen even at a later stage of the disease.

CLINICALTRIALSGOV IDENTIFIER

NCT02865109.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that for patients with SMA1 who are older than 7 months, nusinersen is beneficial.

Protocol for a phase II, monocentre, double-blind, placebo-controlled, cross-over trial to assess efficacy of pyridostigmine in patients with spinal muscular atrophy types 2-4 (SPACE trial)

INTRODUCTION

Hereditary proximal spinal muscular atrophy (SMA) is caused by homozygous loss of function of the survival motor neuron 1 gene. The main characteristic of SMA is degeneration of alpha motor neurons in the anterior horn of the spinal cord, but recent studies in animal models and patients have shown additional anatomical abnormalities and dysfunction of the neuromuscular junction (NMJ). NMJ dysfunction could contribute to symptoms of weakness and fatigability in patients with SMA. We hypothesise that pyridostigmine, an acetylcholinesterase inhibitor that improves neuromuscular transmission, could improve NMJ function and thereby muscle strength and fatigability in patients with SMA.

METHODS AND ANALYSIS

We designed a monocentre, placebo-controlled, double-blind cross-over trial with pyridostigmine and placebo to investigate the effect and efficacy of pyridostigmine on muscle strength and fatigability in patients with genetically confirmed SMA. We aim to include 45 patients with SMA types 2-4, aged 12 years and older in the Netherlands. Participants receive 8 weeks of treatment with pyridostigmine and 8 weeks of treatment with placebo in a random order separated by a washout period of 1 week. Treatment allocation is double blinded. Treatment dose will gradually be increased from 2 mg/kg/day to the maximum dose of 6 mg/kg/day in four daily doses, in the first week of each treatment period. The primary outcome measures are a change in the Motor Function Measure and repeated nine-hole peg test before and after treatment. Secondary outcome measures are changes in recently developed endurance tests, that is, the endurance shuttle nine-hole peg test, the endurance shuttle box and block test and the endurance shuttle walk test, muscle strength, level of daily functioning, quality of and activity in life, perceived fatigue and fatigability, presence of decrement on repetitive nerve stimulation and adverse events.

ETHICS AND DISSEMINATION

The protocol is approved by the local medical ethical review committee at the University Medical Center Utrecht and by the national Central Committee on Research Involving Human Subjects. Findings will be shared with the academic and medical community, funding and patient organisations in order to contribute to optimisation of medical care and quality of life for patients with SMA.

TRIAL REGISTRATION NUMBER

NCT02941328.

Muscle strength and motor function throughout life in a cross-sectional cohort of 180 patients with spinal muscular atrophy types 1c-4

BACKGROUND AND PURPOSE

Natural history studies in spinal muscular atrophy (SMA) have primarily focused on infants and children. Natural history studies encompassing all age groups and SMA types are important for the interpretation of treatment effects of recently introduced survival motor neuron gene-augmenting therapies.

METHODS

We conducted a cross-sectional study to investigate muscle strength, Hammersmith Functional Motor Scale (Expanded) score and the patterns of muscle weakness in relation to age and SMA type.

RESULTS

We included 180 patients with SMA types 1-4 in the age range 1-77.5 years with median disease duration of 18 (range 0-65.8) years. With the exception of the early phases of disease in which children with SMA types 2 and 3 may achieve new motor skills and show a temporary increase in muscle strength, cross-sectional data suggested that declining muscle strength and loss of motor skills over time are characteristic of all SMA types. Mean loss of strength was at least 1 point on the Medical Research Council score and 0.5 point on the Hammersmith Functional Motor Scale (Expanded) score per year. Trend lines compatible with deterioration of motor function and muscle strength started in childhood and continued into adulthood. The age at loss of specific motor skills was associated with disease severity. Triceps, deltoid, iliopsoas and quadriceps were the weakest muscles in all patients. Hierarchical cluster analysis did not show a segmental distribution of muscle weakness as suggested previously.

CONCLUSIONS

Progressive muscle weakness and loss of motor function are characteristic of all SMA types and all ages.

MCM3AP in recessive Charcot-Marie-Tooth neuropathy and mild intellectual disability

Defects in mRNA export from the nucleus have been linked to various neurodegenerative disorders. We report mutations in the gene MCM3AP, encoding the germinal center associated nuclear protein (GANP), in nine affected individuals from five unrelated families. The variants were associated with severe childhood onset primarily axonal (four families) or demyelinating (one family) Charcot-Marie-Tooth neuropathy. Mild to moderate intellectual disability was present in seven of nine affected individuals. The affected individuals were either compound heterozygous or homozygous for different MCM3AP variants, which were predicted to cause depletion of GANP or affect conserved amino acids with likely importance for its function. Accordingly, fibroblasts of affected individuals from one family demonstrated severe depletion of GANP. GANP has been described to function as an mRNA export factor, and to suppress TDP-43-mediated motor neuron degeneration in flies. Thus our results suggest defective mRNA export from nucleus as a potential pathogenic mechanism of axonal degeneration in these patients. The identification of MCM3AP variants in affected individuals from multiple centres establishes it as a disease gene for childhood-onset recessively inherited Charcot-Marie-Tooth neuropathy with intellectual disability.

Expanding the phenotypic spectrum of GABRG2 variants: a recurrent GABRG2 missense variant associated with a severe phenotype

Pathogenic missense and truncating variants in the GABRG2 gene cause a spectrum of epilepsies, from Dravet syndrome to milder simple febrile seizures. In most cases, pathogenic missense variants in the GABRG2 gene segregate with a febrile seizure phenotype. In this case series, we report a recurrent, de novo missense variant (c0.316 G > A; p.A106T) in the GABRG2 gene that was identified in five unrelated individuals. These patients were described to have a more severe phenotype than previously reported for GABRG2 missense variants. Common features include variable early-onset seizures, significant motor and speech delays, intellectual disability, hypotonia, movement disorder, dysmorphic features and vision/ocular issues. Our report further explores a recurrent pathogenic missense variant within the GABRG2 variant family and broadens the spectrum of associated phenotypes for GABRG2-associated disorders.

Synaptic UNC13A protein variant causes increased neurotransmission and dyskinetic movement disorder

Munc13 proteins are essential regulators of neurotransmitter release at nerve cell synapses. They mediate the priming step that renders synaptic vesicles fusion-competent, and their genetic elimination causes a complete block of synaptic transmission. Here we have described a patient displaying a disorder characterized by a dyskinetic movement disorder, developmental delay, and autism. Using whole-exome sequencing, we have shown that this condition is associated with a rare, de novo Pro814Leu variant in the major human Munc13 paralog UNC13A (also known as Munc13-1). Electrophysiological studies in murine neuronal cultures and functional analyses in Caenorhabditis elegans revealed that the UNC13A variant causes a distinct dominant gain of function that is characterized by increased fusion propensity of synaptic vesicles, which leads to increased initial synaptic vesicle release probability and abnormal short-term synaptic plasticity. Our study underscores the critical importance of fine-tuned presynaptic control in normal brain function. Further, it adds the neuronal Munc13 proteins and the synaptic vesicle priming process that they control to the known etiological mechanisms of psychiatric and neurological synaptopathies.

Interhemispheric Lipoma, Callosal Anomaly, and Malformations of Cortical Development: A Case Series

Intracranial lipomas are rare congenital malformations. The most common type of intracranial lipoma is the interhemispheric lipoma, which is frequently associated with callosal anomalies such as hypogenesis or agenesis of the corpus callosum. In contrast, interhemispheric lipomas are less often accompanied with malformations of cortical development (MCD). We report magnetic resonance imaging findings of three infants with an interhemispheric lipoma, associated with a callosal anomaly, and MCD: two infants with nodular interhemispheric lipoma, agenesis of the corpus callosum, and polymicrogyria, and one infant with interhemispheric curvilinear lipoma, hypoplasia of the corpus callosum, and heterotopias. An association was suggested regarding the occurrence of these malformations.

De novo mutations in the motor domain of KIF1A cause cognitive impairment, spastic paraparesis, axonal neuropathy, and cerebellar atrophy

KIF1A is a neuron-specific motor protein that plays important roles in cargo transport along neurites. Recessive mutations in KIF1A were previously described in families with spastic paraparesis or sensory and autonomic neuropathy type-2. Here, we report 11 heterozygous de novo missense mutations (p.S58L, p.T99M, p.G102D, p.V144F, p.R167C, p.A202P, p.S215R, p.R216P, p.L249Q, p.E253K, and p.R316W) in KIF1A in 14 individuals, including two monozygotic twins. Two mutations (p.T99M and p.E253K) were recurrent, each being found in unrelated cases. All these de novo mutations are located in the motor domain (MD) of KIF1A. Structural modeling revealed that they alter conserved residues that are critical for the structure and function of the MD. Transfection studies suggested that at least five of these mutations affect the transport of the MD along axons. Individuals with de novo mutations in KIF1A display a phenotype characterized by cognitive impairment and variable presence of cerebellar atrophy, spastic paraparesis, optic nerve atrophy, peripheral neuropathy, and epilepsy. Our findings thus indicate that de novo missense mutations in the MD of KIF1A cause a phenotype that overlaps with, while being more severe, than that associated with recessive mutations in the same gene.

ALG11-CDG: Three novel mutations and further characterization of the phenotype

We report on two novel patients with ALG11-CDG. The phenotype was characterized by severe psychomotor disability, progressive microcephaly, sensorineural hearing loss, therapy-resistant epilepsy with burst suppression EEG, cerebral atrophy with, in one of them, neuronal heterotopia, and early lethality. Analysis of ALG11 revealed compound heterozygosity involving three novel mutations: the splice site mutation c.45-2A > T, the c.36dupG duplication, and the missense mutation c.479G > T (p.G160V) that was present in both.

Small Biparietal Diameter and Head Circumference Are Part of the Phenotype instead of Independent Prognostic Markers in Fetuses with Spinal Dysraphism

Objective: The aim of this retrospective study was to assess the fetal biparietal diameter (BPD) and head circumference (HC) in the second trimester of pregnancy in fetuses with open spinal dysraphism. Methods: BPD and HC were measured at 16-26 weeks in 74 fetuses with open spinal dysraphism and compared with reference values. Results: BPD was smaller in fetuses with open spinal dysraphism. Of all cases with open spinal dysraphism, 62.2% had a BPD <3rd percentile and 79.7% had a BPD <10th percentile. Of all patients, 54.1% had an HC <3rd percentile and 74.3% had an HC <10th percentile. Conclusion: Almost all fetuses with open neural tube defects have a smaller BPD and HC at 16-26 weeks compared with reference values, which implicates that this is part of the phenotype of children with open spinal dysraphism instead of an independent prognostic marker for a poor cognitive outcome.

Motor evoked potentials and compound muscle action potentials as prognostic tools for neonates with spina bifida

MEPs and CMAPs as prognostic tools for spina bifida.

AIM

The aim of this prospective study was to determine the prognostic value of neurophysiological investigations compared to clinical neurological examination in infants with spina bifida.

METHODS

Thirty-six neonates born with spina bifida between 2002 and 2007 were evaluated and followed for 2 years. Lumbar motor evoked potentials (MEPs) and compound muscle action potentials (CMAPs) were obtained at the median age of 2 days old before surgical closure of the spinal anomaly. MEPs were recorded from the quadriceps femoris, tibialis anterior, and gastrocnemius muscles and CMAPs from the latter two muscles. Areas under the curve and latencies of the MEPs and CMAPs were measured. Clinical neurological outcome at the age of 2 years was described using Muscle Function Classes (MFCs) and ambulation status.

RESULTS

The areas under the curve of MEPs and CMAPs in the legs were associated with lower neonatal levels of motor and sensory impairment. Better muscle function class of the lower limbs at 2 years of age was associated with larger MEP and CMAP areas of the gastrocnemius and tibialis anterior muscles at neonatal age.

DISCUSSION

MEPs and CMAPs of the gastrocnemius and tibialis anterior muscles are of prognostic value for clinical neurological outcome in neonates born with spina bifida.

Early infantile electroencephalography in patients with spina bifida*

OBJECTIVE

The aim of this prospective study was to assess the prognostic value of electroencephalography in infants born with spina bifida.31 infants with spina bifida born between 2002 and 2007 at the Radboud Nijmegen University Medical Centre were evaluated and followed for 2½ years. Electroencephalography (EEG) was performed during the first 8 weeks after birth.

RESULTS

EEG recordings were all within normal limits and showed no abnormalities. 3 of the 31 children showed mild mental disability and major physical disabilities at the age of 30 months.

CONCLUSION

Single Infantile EEG recordings are of limited prognostic value for infants born with spina bifida. Serial EEG recordings in combination with other clinical or neurophysiological investigations might ameliorate the contributing predictive value of neonatal EEG.

Treatment for neonatal neuralgic amyotrophy

We report a 15-day-old neonate with a brachial plexus neuropathy diagnosed as neuralgic amyotrophy concomitant with an osteomyelitis of the ipsilateral humerus. She was treated with intravenous antibiotics and oral dexamethasone and improved dramatically within days.

Broncholithiasis in an immune compromised boy with disseminated Mycobacterium kansasii

A case of broncholithiasis in a child is reported. To our knowledge, it has not been reported in children. Broncholithiasis is a condition in which a peribronchial calcified lymph node erodes into or distorts an adjacent bronchus. Symptoms of broncholithiasis include cough, recurrent episodes of fever, haemoptysis, and purulent sputum. The most common cause of broncholithiasis is Mycobacterium tuberculosis (M. tuberculosis). Here we describe a 14-year-old boy known to have disseminated Mycobacterium kansasii (M. kansasii) infection associated with hypoplastic myelodysplastic syndrome (MDS). He was presented with cough and fever. Computed tomography (CT) and bronchoscopy revealed a large calcified mass eroding in the right main bronchus. While surgical therapy was considered, haemoptysis developed and his condition deteriorated. Bone marrow puncture revealed acute myeloid leukemic transformation of the MDS. Curation was no longer possible. Post mortem examination revealed a large bronchiolith, evolving from a calcified lymph node.

Tissue expression and subcellular localization of CLN3, the Batten disease protein

Juvenile neuronal ceroid lipofuscinosis (Batten disease) is a progressive neurologic disorder which results from mutations in the CLN3 gene, which normally produces a 48-kDa polypeptide of unknown function. To help characterize the CLN3 protein, we have studied its tissue distribution and subcellular localization in human tissues using three epitope-specific polyclonal antibodies to human CLN3 by immunoblot, immunocytochemical, and immunoelectron microscopic analysis. The most abundant CLN3 protein expression was in the gray matter of the brain, where it was localized to astrocytes, capillary endothelium, and neurons. CLN3 was also evident in peripheral nerve, in pancreatic islet cells, and within the seminiferous tubules in the testis. Staining was generally diffuse within the cytoplasm with some nuclear reactivity. Subcellular localization identified the CLN3 protein within the nucleus and along cell membranes. These results were contrasted with the cellular distribution of palmitoyl-protein thioesterase (PPT), the enzyme whose deficiency is responsible for infantile neuronal ceroid lipofuscinosis (CLN1). PPT was most abundant in brain and visceral macrophages where it displayed a coarse granular staining pattern typical of lysosomal distribution. Immunoelectron microscopy confirmed that PPT immunoreactivity was limited to lysosomes.