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).
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.
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.
NL72562.041.20 (registered at https://www.toetsingonline.nl . 26-03-2020).
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.
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.
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.
Abstract We aimed to disentangle the proportional contributions of upper and lower motor neuron dysfunction to motor impairment in children with spina bifida. We enrolled 42 children (mean age, 11.2 ...years; standard deviation, 2.8 years) with spina bifida and 36 control children (mean age, 11.4 years; standard deviation, 2.6 years). Motor impairment was graded to severity scales in children with spina bifida. We recorded motor evoked potentials after transcranial and lumbosacral magnetic stimulation and compound muscle action potentials after electric nerve stimulation. Regarding lower motor neuron function, severely impaired children with spina bifida demonstrated smaller compound muscle action potential areas and lumbosacral motor evoked potential areas than control children; mildly impaired children hardly differed from control children. Compound muscle action potential latencies and lumbosacral motor evoked potential latencies did not differ between children with spina bifida and control children. Regarding upper motor neuron function, children with spina bifida demonstrated smaller transcranial motor evoked potential areas and longer central motor conduction times than control children. The smallest motor evoked potential areas and longest central motor conduction times were observed in severely impaired children. In children with spina bifida, the contribution of upper motor neuron dysfunction to motor impairment is more considerable than expected from clinical neurologic examination.
To evaluate the safety and clinical efficacy of nusinersen in patients older than 7 months with spinal muscular atrophy type 1 (SMA1).
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).
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 (
< 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 (
) gene.
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.
NCT02865109.
This study provides Class IV evidence that for patients with SMA1 who are older than 7 months, nusinersen is beneficial.
To investigate the natural course of scoliosis and to estimate lifetime probability of scoliosis surgery in spinal muscular atrophy (SMA).
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.
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 (
= 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,
= 0.017). Scoliosis development was characterized by initial slow progression, followed by acceleration in the 1.5- to 2-year period before surgery.
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.
Aim
To determine factors associated with acquisition of a sitting position in patients with spinal muscular atrophy type 1 (SMA1) treated with nusinersen.
Method
Using data from the registry of ...patients with SMA1 treated with nusinersen, we compared the subgroups of sitters and non‐sitters after 14 months of therapy as a function of baseline level, SMN2 copy number, age at treatment initiation, and improvement at 2 and 6 months post‐treatment initiation. We used Hammersmith Infant Neurological Examination, Section 2 (HINE‐2) and Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders for motor evaluation.
Results
Fifty children (22 females, 28 males), mean age 22 months (SD 20.7; range 2.5–102.8mo) were treated. Data on sitting position acquisition were collected for 47 patients at month 14. Fifteen patients were able to sit unassisted; 11 of 15 had a baseline HINE‐2 score of at least 2 points and 11 of 14 had an improvement over baseline of at least 2 points at month 6. Patients who improved by 2 or more points at month 6 were three times more likely to be sitters at month 14 than those who did not.
Interpretation
High baseline motor function and improvement in HINE‐2 score after 6 months of treatment are associated with the probability of acquiring a sitting position in patients with SMA1 treated with nusinersen.
What this paper adds
Fifteen of 47 patients with spinal muscular atrophy could sit unaided 14 months after treatment with nusinersen.
The number of SMN2 copies were not predictive of acquisition of a sitting position.
Baseline condition and clinical response after 6 months of treatment were most predictive of sitting position acquisition.
What this paper adds
Fifteen of 47 patients with spinal muscular atrophy could sit unaided 14 months after treatment with nusinersen.
The number of SMN2 copies were not predictive of acquisition of a sitting position.
Baseline condition and clinical response after 6 months of treatment were most predictive of sitting position acquisition.
This article is commented on by Smith on page 267 of this issue.
Editor's Choice
At long last, medical treatments specifically developed to circumvent mutations in children with genetic developmental conditions appear to alter their development, hopefully in meaningful ways. The notion that children with spinal muscular atrophy type 1 (SMA1) do not achieve the sitting motor milestone had very strong diagnostic and counselling implications until recently. But the advent of antisense nucleotide and gene therapy for SMA1 has potential for rewriting the natural history of the condition in much better terms. My Editor's Choice for the March 2020 issue reports on factors associated with acquisition of sitting in a group of children with SMA1 treated with nusinersen. Hopefully, these results will contribute to improvements in early recognition and treatments, and will feed the ethical and societal questioning with emerging, actual information.
•Distal muscles in patients with spinal muscular atrophy (SMA) showed marked motor unit (MU) loss detected by the compound muscle action potential (CMAP) scan.•Severity of pathological MU changes ...differed between SMA types 2–4.•Pathological MU changes derived from the CMAP scan are potentially useful for follow-up in SMA.
To assess motor unit (MU) changes in patients with spinal muscular atrophy (SMA) using compound muscle action potential (CMAP) scans.
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 (CMAPmax), a motor unit number estimate (MUNE), and D50 which quantifies the largest discontinuities within CMAP scans.
Median CMAPmax 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 CMAPmax (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). CMAPmax, MUNE and D50 values differed between SMA types (P < 0.001). Lower motor function scores were related to patients with lower CMAPmax, MUNE and D50 values (P < 0.001).
The CMAP scan is an easily applicable technique that is superior to routine assessment of CMAPmax in SMA.
The detection of pathological MU changes across the spectrum of SMA may provide important biomarkers for evaluating disease course and monitoring treatment efficacy.
•The majority of children treated with nusinersen show improvement in at least 1 item.•Most common score changes are changes from 0 to 1.•Sitters most likely improve in items that assess ...rolling.•Walkers most likely improve in items that assess half-kneeling.
The Hammersmith Functional Motor Scale-Expanded (HFMSE) is a validated outcome measure for monitoring changes in functional strength in patients with spinal muscular atrophy (SMA). The objective of this study was to explore changes in HFMSE item-scores in children with SMA types 2 and 3a treated with nusinersen over a period of six to twenty months. We stratified patients according to motor ability (sitting and walking), and calculated numbers and percentages for each specific improvement (positive score change) or decrease (negative score change) for the total group and each subgroup and calculated frequency distributions of specific score changes. Ninety-one percent of the children showed improvement in at least 1 item, twenty-eight percent showed a score decrease in 1 or more items. In the first six to twenty months of nusinersen treatment motor function change was characterized by the acquisition of the ability to perform specific tasks with compensation strategies (score changes from 0 to 1). Children with the ability to sit were most likely to improve in items that assess rolling, whilst children with the ability to walk most likely improved in items that assess half-kneeling. The ability most frequently lost was hip flexion in supine position.
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