April 24, 2018April 10, 2018Free AccessIndividual N-of-1 Trial Salbutamol Versus Placebo as Attack Treatment in a Patient with Hyperkalemic Periodic Paralysis (P3.455)Robyn Weijma, Esther Merkus, Bas van Vlijmen, Hans Groenewoud, Gert Jan van der Wilt, Baziel van Engelen, Joost Raaphorst, Christiaan Saris, and Bas StunnenbergAuthors Info & AffiliationsApril 10, 2018 issue90 (15_supplement) Letters to the Editor
Neuromuscular disorders (NMDs) are clinically and genetically heterogeneous. Accurate molecular genetic diagnosis can improve clinical management, provides appropriate genetic counseling and testing of relatives, and allows potential therapeutic trials.To establish the clinical utility of panel-based whole exome sequencing (WES) in NMDs in a population with children and adults with various neuromuscular symptoms.Clinical exome sequencing, followed by diagnostic interpretation of variants in genes associated with NMDs, was performed in a cohort of 396 patients suspected of having a genetic cause with a variable age of onset, neuromuscular phenotype, and inheritance pattern. Many had previously undergone targeted gene testing without results.Disease-causing variants were identified in 75/396 patients (19%), with variants in the three COL6-genes (COL6A1, COL6A2 and COL6A3) as the most common cause of the identified muscle disorder, followed by variants in the RYR1 gene. Together, these four genes account for almost 25% of cases in whom a definite genetic cause was identified. Furthermore, likely pathogenic variants and/or variants of uncertain significance were identified in 95 of the patients (24%), in whom functional and/or segregation analysis should be used to confirm or reject the pathogenicity. In 18% of the cases with a disease-causing variant of which we received additional clinical information, we identified a genetic cause in genes of which the associated phenotypes did not match that of the patients. Hence, the advantage of panel-based WES is its unbiased approach.Whole exome sequencing, followed by filtering for NMD genes, offers an unbiased approach for the genetic diagnostics of NMD patients. This approach could be used as a first-tier test in neuromuscular disorders with a high suspicion of a genetic cause. With uncertain results, functional testing and segregation analysis are needed to complete the evidence.
Objective: We aimed to validate the aggregated N-of-1 trials design using the case of mexiletine treatment in non-dystrophic myotonia. Background: In rare diseases it is difficult to achieve level 1 evidence of treatment efficacy due to small cohorts and clinical heterogeneity. With emerging treatments for rare diseases, validation of innovative trial designs is urgently needed. Design/Methods: We performed a series of aggregated, double-blind, randomized-controlled N-of-1-trials (mexiletine versus placebo) in 30 patients with non-dystrophic myotonia. The primary outcome measure was daily-reported muscle stiffness on a 1–9 scale, with higher scores indicating more impairment. Secondary outcomes included quality of life, myotonia and safety measures. A Bayesian hierarchical model combined individual N-of-1 trial results into the probability of reaching a clinically meaningful effect ( ≥ 0.75 difference on the primary outcome measure). To assess our trial design validity, we compared our results head-to-head with a previously conducted RCT. Eligibility criteria, treatment regimen, end-points and assessments were fully compatible between trials. Results: In 24 of the 27 patients who completed their N-of-1 trial, a clinically meaningful treatment effect was found. Mexiletine resulted in a mean muscle stiffness reduction of 3.06 (n=27, 95% credible interval 1.96–4.15). Adverse reactions included gastro-intestinal complaints (70%). The evidence that mexiletine reduces myotonia with a meaningful difference, with 95% probability, was reached after the first 11 consecutive patients. Meta-analysis of aggregated N-of-1 trials and RCT results showed absence of statistical heterogeneity (I2 = 0%) on the primary outcome measure. Secondary outcomes and adverse reactions profiles were comparable between trials. Conclusions: Our data show that aggregated N-of-1 trials produce a valid estimate of treatment effect at the group level. Compared to conventional designs, this trial approach seems promising with regard to efficiency and when dealing with patient heterogeneity. Furthermore, our data strengthen the evidence of mexiletine as a safe and effective treatment in non-dystrophic myotonia. Study Supported by: ZonMw, The Netherlands Organisation for Health Research and Development (Project number: 152002029) Disclosure: Dr. Stunnenberg has nothing to disclose. Dr. Raaphorst has nothing to disclose. Dr. Groenewoud has nothing to disclose. Dr. Statland has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Strongbridge, Acceleron, Regeneron, and Sanofi. Dr. Griggs has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Serve on DSMB for PTC Therapeutics, Idera Pharma; consultant for Saretpta, Marathon, Strongbridge and Taro Pharma. Dr. Griggs has received personal compensation in an editorial capacity for Correspondence editor for Neurology. Dr. Griggs has received royalty, license fees, or contractual rights payments from Royalties from Marathon and PTC Pharmaceuticals. Dr. Griggs has received research support from Research support from Marathon, PTC. Dr. Woertman has nothing to disclose. Dr. Stegeman has nothing to disclose. Dr. Timmermans has nothing to disclose. Dr. Trivedi has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Sanofi. Dr. Trivedi has received research support from Sanofi, CSL Behring. Dr. Matthews has nothing to disclose. Dr. Saris has nothing to disclose. Dr. Schouwenberg has nothing to disclose. Dr. Drost has nothing to disclose. Dr. van Engelen has nothing to disclose. Dr. van der Wilt has nothing to disclose.
To perform a systematic review of published N-of-1 trials (e.g., single patient crossover trials) in neurologic disorders, including an assessment of methodologic quality and reporting.We searched PubMed, MEDLINE, and Embase from inception date to the December 1, 2019, for reports on N-of-1 trials in neurologic disorders. Basic trial information on design, disease, intervention, analysis, and treatment success was extracted. Strengths and weaknesses of the N-of-1 trials were assessed with the Consolidated Standards of Reporting Trials extension for N-of-1 trials (CENT) 2015 criteria checklist and the Jadad score as measures of quality and reporting.We retrieved 40 reports of N-of-1 trials in neurologic disorders (19 individual N-of-1 trials, 21 series of N-of-1 trials). Most N-of-1 trials were performed in neuromuscular and neurodegenerative/movement disorders. Unlike the majority of trials that studied the main symptom(s) of a chronic stable condition, 9 N-of-1 trials studied a stable chronic symptom of a progressive or acute neurologic disorder. Besides pharmacologic interventions, electric stimulation protocols and nutritional products were studied. A mean total CENT score of 20.88 (SD 9.10, range 0-43) and mean total Jadad score of 2.90 (SD 2.15, range 0-5) were found as methodologic measures of quality and reporting across all N-of-1 trials.N-of-1 trials have been reported in numerous neurologic disorders, not only in chronic stable disorders, but also in progressive or acute disorders with a stable symptom. This indicates the emerging therapeutic area of N-of-1 trials in neurology. Methodologic quality and reporting of N-of-1 trials were found to be suboptimal and can easily be improved in future trials by appropriately describing the methods of blinding and randomization and following CENT guidelines. Because most N-of-1 trials remain unreported in medical literature, this systematic review probably represents only the tip of the iceberg of conducted N-of-1 trials in neurologic disorders. In addition to conventional trial designs, N-of-1 trials can help to bridge the gap between research and clinical care by providing an alternative, personalized level 1 evidence base for suitable treatments.
Sodium channelopathies (NaCh), as part of the non-dystrophic myotonic syndromes (NDMs), reflect a heterogeneous group of clinical phenotypes accompanied by a generalized myotonia. Because of recent availability of diagnostic genetic testing in NDM, there is a need for identification of clear clinical genotype-phenotype correlations. This will enable clinicians to distinguish NDMs from myotonic dystrophy, thus allowing them to inform patients promptly about the disease, perform genetic counseling, and orient therapy (Vicart et al. Neurol Sci 26:194-202, 2005). We describe the first distinctive clinical genotype-phenotype correlation within NaCh: a strictly isolated eyelid closure myotonia associated with the L250P mutation in SCN4A. Using clinical assessment and needle EMG, we identified this genotype-phenotype correlation in six L250P patients from one NaCh family and confirmed this finding in another, unrelated NaCh family with three L250P patients.
Febrile seizures are the most common form of convulsions between the age of 6 months and 5 years (Leviton & Cowan, 1982), but genetic factors have not been identified. Here we investigated the molecular basis of febrile seizures in a small family with co-occurring hemiplegic migraine (IHS, 2004) and febrile seizures (Fig. S1). Intermittent ataxia and diffuse encephalopathic episodes are also present in this family. Using direct sequencing (see Vanmolkot et al., 2003), we identified a novel de novo heterozygous 2563 G>A substitution in exon 18 resulting in an amino acid change from a glycine to an arginine at position 855 in the ATP1A2 FHM2 gene (De Fusco et al., 2003) that encodes the α2 subunit of Na+, K+-ATPase pumps. Only, the proband (III-1), the affected mother (II-2), and affected brother (III-2) carry this ATP1A2 mutation. Gly855 is evolutionary conserved (Fig. S2A), and the mutation was not identified in 300 control chromosomes. An ouabain challenge assay (see Vanmolkot et al., 2006) for the mutant p.Gly855Arg construct, unlike wild-type, showed complete loss of cell survival, indicating that the mutation has functional consequences at the protein level (Fig. S2B). This now 13-year-old proband (III-1) (Fig. S1) experienced, from the age of 9 months to 3 years, five complex febrile seizures and one simple febrile seizure. The complex seizures either lasted more than 15 min or started focally. There were also episodes of several seizures occurring sequentially. From the age of 7 months to 5 years, he also experienced several nonfebrile seizures, which typically had a focal onset and were secondary generalized. These seizures usually lasted up to 5 min, but sometimes were prolonged (up to 40 min), and at times occurred in clusters. Seizures stopped at age 5. From age 2.5, he experienced headache attacks accompanied by transient hemiparesis as well as frequent unprovoked episodes of ataxia lasting a few minutes to days. In addition, he had episodes of rapidly progressive drowsiness down to Glasgow Coma scale (GCS) 6–7, without any focal neurologic deficits or epilepsy. The patient has ongoing behavioral problems and mild learning difficulties. His now 3-year-old half-brother (III-2) had one complex (focal) febrile seizure lasting 15 min when he was 7 months old. Since the age of 21 months he had episodes of hemiplegia, and recurrent encephalopathic episodes often preceded by headache and hemiplegia, and one episode of unsteadiness after minor head injury. The mother (II-2), now age 31 years, had two simple febrile seizures at age 2 and also had attacks of hemiplegic migraine. The father of the proband (II-1) and the father (II-3) of his half-brother and their grandparents (I-1 and I-2) never had hemiplegic migraine, ataxia, or seizures. We feel that the ATP1A2 p.Gly855Arg mutation is the causal mutation in this family for a number of reasons: (1) FHM and febrile convulsions were present only in the three mutation carriers and not in non–mutation carriers; (2) the mutation was not identified in a panel of 150 healthy control individuals, and (3) functional studies revealed that the mutant has a deleterious effect on cell survival. Febrile seizures are reported in only some mutation carriers of three FHM2 families (Vanmolkot et al., 2003; Deprez et al., 2008; Fernandez et al., 2008). Future identification of additional families with co-occurring hemiplegic migraine and febrile seizures may shed light on the association between ATP1A2 gene mutations and febrile seizures. We, therefore, recommend genetic analysis of the ATP1A2 gene in patients with febrile seizures. We thank Dr. Thomas A. Pressley (the University of Texas Medical School, Lubbock, TX, U.S.A.) for providing anti-HERED antibody and L. Broos for technical assistance. This work was supported by grants of the Netherlands Organization for Scientific Research (NWO) (907-00-217 G.M.T, and Vici 918.56.602, M.D.F), and the Center of Medical System Biology (CMSB) established by the Netherlands Genomics Initiative/Netherlands Organisation for Scientific Research (NGI/NWO). We confirm that we have read the Journal’s position on issues involved in ethical publication and affirm that this report is consistent with those guidelines. None of the authors has any conflict of interest to disclose. Figure S1. Pedigree of the FHM 2 family. The arrow indicates the proband. Squares indicate male subjects and circles indicate female subjects. To indicate clinical diagnosis; symbols with lower half filled represent FHM and double lined symbols represent febrile seizures. Individuals heterozygous for the ATP1A2 mutation are indicated by G855R. Wild-type (WT) indicates that the individual does not have the mutation. Figure S2. Genetic and functional data on mutant p.Gly855Arg. (A) Alignment of amino acid sequences of several vertebrate sodium-potassium ATPase α-subunits; Gly855 is represented as a black box. (B) Upper panel shows western blot analysis of transfected HeLa cells. Lower panel shows graphic representation of ouabain cell survival assay. Bars represent cell survival after 5 days of ouabain treatment (error bars indicate SEM). Please note: Wiley-Blackwell is not responsible for the content or functionality of any supporting materials supplied by the authors. Any queries (other than missing material) should be directed to the corresponding author for the article. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
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