Objective: This study aimed to validate the single breath count test (SBCT) against volitional measures of respiratory muscle function in healthy subjects and people with neuromuscular disorders (NMD; n = 100 per group). Methods: Testing comprised upright and supine SBCT, forced vital capacity (FVC), maximum inspiratory pressure (MIP), and sniff nasal inspiratory pressure (SNIP). Predictability of FVC by SBCT was assessed using logarithmic regression analysis. Receiver operating characteristics curves were used to identify SBCT thresholds for lung restriction (FVC < 80% predicted), inspiratory muscle weakness (MIP < 60 cmH2O), and indication for non-invasive ventilation (NIV) in NMD patients. Results: In both groups, SBCT showed moderate correlation with FVC. In patients, SBCT values were also correlated with MIP and SNIP. Strength of correlations was similar with supine and upright SBCT which accounted for 23.7% of FVC variance in healthy individuals (44.5% in patients). Predictive thresholds of upright SBCT were < 27 for MIP < 60 cmH2O (sensitivity 0.61/specificity 0.86), <39 for NIV indication (0.92/0.46), and <41 for FVC < 80% predicted (0.89/0.62). Conclusion: The SBCT is positively correlated with spirometry. It predicts both lung restriction and NIV indication in NMD patients. The SBCT allows for remote monitoring and may substitute for spirometry/manometry if appropriate devices are unavailable.

Background Pompe Disease (PD) is a rare inherited metabolic myopathy, caused by lysosomal-α-glucosidase (GAA) deficiency, which leads to glycogen accumulation within the lysosomes, resulting in cellular and tissue damage. Due to the emergence of a disease modifying treatment with recombinant GAA there has been a large increase in studies of late onset Pompe Disease (LOPD) during the last decade. Methods The present study evaluates muscle quality in 10 patients with LOPD receiving treatment with enzyme replacement therapy and in 10 age and gender matched healthy controls applying T1-weighted Dixon MR imaging and isokinetic dynamometry. Muscle quality was determined by muscle strength in relation to muscle size (contractile cross-sectional area, CSA) and to muscle quality (fat fraction). A follow-up evaluation of the patients was performed after 8–12 months. Patient evaluations also included: six-minute walking test (6MWT), forced vital capacity, manual muscle testing and SF-36 questionnaire. Results Fat fraction of knee flexors (0.15 vs 0.07, p < 0.05) and hip muscles (0.11 vs 0.07, p < 0.05) were higher in patients than controls. In patients, contractile CSA correlated with muscle strength (knee flexors: r = 0.86, knee extensors: r = 0.88, hip extensors: r = 0.83, p < 0.05). No correlation was found between fat fraction and muscle strength. The fat fraction of thigh muscles did not correlate with scores from the clinical tests nor did it correlate with the 6MWT. During follow-up, the contractile CSA of the knee extensors increased by 2%. No other statistically significant change was observed. Quantitative MRI reflects muscle function in patients with LOPD, but larger long-term studies are needed to evaluate its utility in detecting changes over time.

Sleep-related hypermotor epilepsy, or nocturnal frontal lobe epilepsy, as it was formerly called, is a focal epilepsy with mostly sleep-related seizures of hypermotor, tonic or dystonic semiology. Sleep-related hypermotor epilepsy may be attributed to a monogenetic cause with autosomal dominant inheritance. Mutations are described in different genes, including the genes for three subunits of the nicotinic acetylcholine receptor. We present a family with members over four generations exhibiting sleep-related hypermotor epilepsy. Genetic testing was available for three members from three generations, and revealed two variants in the alpha-4 subunit of the nicotinic acetylcholine receptor (one of them being novel) which are likely to be disease-causing. As these mutations were identified in cis configuration (on the same allele), we do not know whether one of the variants alone or a combination of the two is responsible for the pathogenicity.

Objective To test the hypothesis that monogenic neuropathies such as Charcot-Marie-Tooth disease (CMT) contribute to frequent but often unexplained neuropathies in the elderly, we performed genetic analysis of 230 patients with unexplained axonal neuropathies and disease onset >= 35 years. Methods We recruited patients, collected clinical data, and conducted whole-exome sequencing (WES; n = 126) and MME single-gene sequencing (n = 104). We further queried WES repositories for MME variants and measured blood levels of the MME-encoded protein neprilysin. Results In the WES cohort, the overall detection rate for assumed disease-causing variants in genes for CMT or other conditions associated with neuropathies was 18.3% (familial cases 26.4%, apparently sporadic cases 12.3%). MME was most frequently involved and accounted for 34.8% of genetically solved cases. The relevance of MME for late-onset neuropathies was further supported by detection of a comparable proportion of cases in an independent patient sample, preponderance ofMMEvariants among patients compared to population frequencies, retrieval of additional late-onset neuropathy patients with MME variants from WES repositories, and low neprilysin levels in patients' blood samples. Transmission of MME variants was often consistent with an incompletely penetrant autosomal-dominant trait and less frequently with autosomal-recessive inheritance. Conclusions A detectable fraction of unexplained late-onset axonal neuropathies is genetically determined, by variants in either CMT genes or genes involved in other conditions that affect the peripheral nerves and can mimic a CMT phenotype. MME variants can act as completely penetrant recessive alleles but also confer dominantly inherited susceptibility to axonal neuropathies in an aging population.

Die spinale Muskelatrophie (SMA) ist eine progressive, autosomal-rezessive neurodegenerative Erkrankung mit einer Inzidenz von 1:10.000 Lebendgeburten. Mit besserem Verständnis der molekularen Basis der SMA in den letzten beiden Jahrzehnten richtete sich der Fokus therapeutischer Entwicklungen auf eine Erhöhung des Anteils an funktionsfähigem SMN-Protein, entweder durch Einschluss von Exon 7 in SMN2-Transkripte, Erhöhung der SMN2-Genexpression oder durch direkten Genersatz von SMN1. Seit Juni 2017 steht mit Nusinersen/Spinraza® (Biogen GmbH, Ismaning, Deutschland) – ein Antisense-Oligonukleotid, dass das Pre-Messenger-RNA-Spleißen von Exon 7 des SMN2-Gens modifiziert und so zu stabiler SMN-Proteinexpression führt – erstmals eine wirksame krankheitsmodifizierende Therapie zur Verfügung. Nusinersen zeigte in mehreren kontrollierten Studien ein sehr gutes Nutzen-Risiko-Profil und war mit klinisch relevanten Verbesserungen der motorischen Funktion assoziiert. Dabei war ein präsymptomatischer Therapiebeginn mit einem größeren therapeutischen Nutzen verbunden, was die Notwendigkeit eines Neugeborenenscreenings unterstreicht. Die wiederholte intrathekale Applikation von Nusinersen ist vor allem bei Patienten mit schweren Skoliosen oder nach wirbelsäulenaufrichtenden Operationen eine technische Herausforderung. Bisher liegt die überwiegende Mehrheit der SMA-Patienten außerhalb der Studienpopulationen, sodass Experten einen Mangel an Daten zu Wirksamkeit und Sicherheit über das Kindesalter hinaus beklagen. Diese Lücke soll durch eine systematische Datensammlung der SMArtCARE-Initiative geschlossen werden, in der Daten möglichst umfassend und systematisch im Rahmen der klinischen Routine erfasst werden, unabhängig davon, ob und wie ein Patient therapiert wird.

Diaphragm weakness in Charcot-Marie-Tooth disease 1A (CMT1A) is usually associated with severe disease manifestation. This study comprehensively investigated phrenic nerve conductivity, inspiratory and expiratory muscle function in ambulatory CMT1A patients. Nineteen adults with CMT1A (13 females, 47 +/- 12 years) underwent spiromanometry, diaphragm ultrasound, and magnetic stimulation of the phrenic nerves and the lower thoracic nerve roots, with recording of diaphragm compound muscle action potentials (dCMAP, n = 15), transdiaphragmatic and gastric pressures (twPdi and twPgas, n = 12). Diaphragm motor evoked potentials (dMEP, n = 15) were recorded following cortical magnetic stimulation. Patients had not been selected for respiratory complaints. Disease severity was assessed using the CMT Neuropathy Scale version 2 (CMT-NSv2). Healthy control subjects were matched for age, sex, and body mass index. The following parameters were significantly lower in CMT1A patients than in controls (all P < .05): forced vital capacity (91 +/- 16 vs 110 +/- 15% predicted), maximum inspiratory pressure (68 +/- 22 vs 88 +/- 29 cmH(2)O), maximum expiratory pressure (91 +/- 23 vs 123 +/- 24 cmH(2)O), and peak cough flow (377 +/- 135 vs 492 +/- 130 L/min). In CMT1A patients, dMEP and dCMAP were delayed. Patients vs controls showed lower diaphragm excursion (5 +/- 2 vs 8 +/- 2 cm), diaphragm thickening ratio (DTR, 1.9 [1.6-2.2] vs 2.5 [2.1-3.1]), and twPdi (8 +/- 6 vs 19 +/- 7 cmH(2)O; all P < .05). DTR inversely correlated with the CMT-NSv2 score (r = -.59, P = .02). There was no group difference in twPgas following abdominal muscle stimulation. Ambulatory CMT1A patients may show phrenic nerve involvement and reduced respiratory muscle strength. Respiratory muscle weakness can be attributed to diaphragm dysfunction alone. It relates to neurological impairment and likely reflects a disease continuum.

An vier verschiedenen Zentren in Deutschland wurden insgesamt 158 Patienten, bei denen eine molekulargenetisch gesicherte CMT1a bestand, rekrutiert.

Gängige Outcome-Kriterien für klinische Studien zur Behandlung von CMT, wie der CMTNSv2 und der ONLS, basieren auf klinischen und elektrophysiologischen Parametern. Dabei werden zugrundeliegende Nervenschäden nicht berücksichtigt. Um zusätzliche objektive und reproduzierbare Outcome-Kriterien für künftige Studien zu finden, haben wir die Innervierung von Hautbiopsien des Fingers von 40 CMT1A-Patienten mithilfe von Immunhistochemie untersucht und mit 45 gesunden Kontrollen (GK), 7 CIDP- und 16 SFN-Patienten verglichen. Die intraepidermale Nervenfaserdichte (IENFD) von CMT1A-Patienten war signifikant verringert im Vergleich zu den drei Kontrollgruppen (CMT1A: 3.25 Fasern/mm, CIDP: 6.1 F/mm, p = 0.036, SFN: 5.9 F/mm, p = 0.022, GK: 5.0 F/mm, p = 0.002). Zudem korrelierten die IENFD negativ mit dem CMTNSv2 der CMT1A-Patienten und dem Alter der gesunden Kontrollen (CMTNSv2-IENFD: R =-0.37, p = 0.019, Alter-IENFD: R -0.51, p = 0.0003). Ebenso konnte eine Abnahme der Merkelzellen (MrkC) und der Meissner-Körperchen (MC) in der CMT1A-Gruppe verglichen mit den GK festgestellt werden (CMT1A: 0.5 MrkC/mm, GK: 1.1MrkC/mm, p = 0.037; CMT1A: 0.036 MC/mm, GK:0.053 MC/mm, p = 0.046). Langerhanszell-Dichten der CMT1A-, SFN- und GK-Gruppen unterschieden sich nicht. Eine Reduzierung der dermalen Nervenfaserbündeln mit oder ohne myelinisierte Fasern gab es in CMT1A verglichen mit den Kontrollgruppen ebenfalls nicht. Analysen von Verlaufsbiopsien werden zeigen, ob die IENFD als möglicher Biomarker geeignet ist.

In einem etablierten CMT1A Rattenmodell konnten wir Erkrankungsmarker („Biomarker“) in den Nerven und der Haut finden, die Rückschlüsse auf die Erkrankung und deren Schwere zulassen. Ziel war es nun, diese Biomarker im Rahmen einer „forward translation“ auf Patienten zu übertragen.

Hereditary sensory and autonomic neuropathy type 1 (HSAN1) is a rare, autosomal dominantly inherited, slowly progressive and length-dependent axonal peripheral neuropathy. HSAN1 is associated with several mutations in serine-palmitoyltransferase (SPT), the first enzyme in the de novo sphingolipid biosynthetic pathway. HSAN1 mutations alter the substrate specificity of SPT, which leads to the formation of 1-deoxysphingolipids, an atypical and neurotoxic subclass of sphingolipids. This study describes the clinical and neurophysiological phenotype of a German family with a novel SPTCL2 mutation (c.529A > G; N177D) associated with HSAN1 and the biochemical characterization of this mutation.) The mutaion was identified in five family members that segregated with the diesease. Patients were characterized genetically and clinically for neurophysiological function. Their plasma sphingolipid profiles were analyzed by LC–MS. The biochemical properties of the mutation were characterized in a cell-based activity assay. Affected family members showed elevated 1-deoxysphingolipid plasma levels. HEK293 cells expressing the N177D SPTLC2 mutant showed increased de novo 1-deoxysphingolipid formation, but also displayed elevated canonical SPT activity and increased C20 sphingoid base production. This study identifies the SPTLC2 N177D variant as a novel disease-causing mutation with increased 1-deoxySL formation and its association with a typical HSAN1 phenotype.

Mutations in the SACS gene have been initially reported in a rare autosomal recessive cerebellar ataxia syndrome featuring prominent cerebellar atrophy, spasticity and peripheral neuropathy as well as retinal abnormalities in some cases (autosomal recessive spastic ataxia of Charlevoix–Saguenay, ARSACS). In the past few years, the phenotypic spectrum has broadened, mainly owing to the availability and application of high-throughput genetic testing methods. We identified nine patients (three sib pairs, three singleton cases) with isolated, non-syndromic hereditary motor and sensory neuropathy (HMSN) who carried pathogenic SACS mutations, either in the homozygous or compound heterozygous state. None of the patients displayed spasticity or pyramidal signs. Ataxia, which was noted in only three patients, was consistent with a sensory ataxia. Nerve conduction and nerve biopsy studies showed mixed demyelinating and axonal neuropathy. Brain MRI scans were either normal or revealed isolated upper vermis atrophy of the cerebellum. Our findings confirm the broad clinical spectrum associated with SACS mutations, including pure polyneuropathy without characteristic clinical and brain imaging manifestations of ARSACS.

Die häufigste neurogenetische Erkrankung in der klinischen Neurologie ist die hereditäre sensible und motorische Neuropathie (HMSN – synonym Charcot-Marie-Tooth (CMT)).

An autoimmune-mediated process in the pathophysiology of narcolepsy type 1 (NT1) is highly suspicious, if this pathomechanism is transferable to other types of central disorders of hypersomnolence (CDH), is still controversial. The association of NT1 with HLA class II system implicates a T-cell-mediated autoimmunity, in which helper CD4+ T-cells and cytotoxic CD8+ T-cells may be pathogenic. This study aimed to identify specific immune profiles in peripheral blood (PB) and cerebrospinal fluid (CSF) in different types of CDH. Forty-three people with polysomnographically confirmed CDH (24 idiopathic hypersomnia [IH], 12 NT1, and 7 NT2) were compared with 24 healthy controls (HC). PB and CSF were analyzed with multiparameter flow cytometry to distinguish between subclasses of peripheral and intrathecal immune cells and specific surface markers of T-cells. The overall proportion of helper CD4+ T-cells and cytotoxic CD8+ T-cells in PB and CSF did not differ between the patients and HC. Activated HLA-DR+ CD4+ T-cells and HLA-DR+ CD8+ T-cells in PB and CSF both in NT1, NT2 and IH were significantly increased compared with HC. A significant correlation of HLA-DR+ CD4+- and HLA-DR+ CD8+ T-cells with higher amounts of excessive daytime sleepiness was found in the NT1 and IH groups, indicating an association of activated T-cells in the central nervous system with an increase in sleepiness. These findings provide further evidence of a T-cell-mediated autoimmunity not only in NT1, but also in NT2 and IH. Moreover, the identification of activated cytotoxic CD8+ T-cells further supports the evidence of T-cell-mediated neuronal damage, which has previously been suggested in NT1.

ZusammenfassungDie Gruppe der hereditären Neuropathien (Charcot-Marie-Tooth-Erkrankungen, CMT) ist eine klinisch und genetisch heterogene Gruppe von peripheren Neuropathien. Die Prävalenz beträgt 1:2 500, womit die CMT zu den seltenen Erkrankungen zählen. In der klinischen Neurologie stellen sie die häufigste neurogenetische Erkrankung dar. Die CMTFormen mit sensiblen und motorischen Symptomen sind am häufigsten. Neben diesen Formen gibt es rein sensible Formen, mit oder ohne autonome Symptome (HSAN), rein motorische Neuropathien (dHMN) und die besondere Form der hereditären Neuropathie mit Neigung zu Druckparesen (HNPP). Die molekulargenetische Diagnostik wurde zunehmend weiterentwickelt. Die Gendiagnostik ist integraler Bestandteil der Diagnostik für Patienten mit dem klinischen Verdacht auf das Vorliegen einer hereditären Neuropathie. Die klinische und genetische Zuordnung ist durch die große Heterogenität des Phänotyps bei über 80 potenziell krankheitsverursachenden Genen oft sehr erschwert. Trotzdem werden über 90% aller genetisch gesicherten CMT durch Mutationen in vier Genen (PMP22, Cx32, MPZ und MFN2) geklärt. Diese stellen die klinisch relevanten Kandidatengene im klinischen Alltag dar.

Hereditary neuropathies comprise a wide variety of chronic diseases associated to more than 80 genes identified to date. We herein examined 612 index patients with either a Charcot-Marie-Tooth phenotype, hereditary sensory neuropathy, familial amyloid neuropathy, or small fiber neuropathy using a customized multigene panel based on the next generation sequencing technique. In 121 cases (19.8%), we identified at least one putative pathogenic mutation. Of these, 54.4% showed an autosomal dominant, 33.9% an autosomal recessive, and 11.6% an X-linked inheritance. The most frequently affected genes were PMP22 (16.4%), GJB1 (10.7%), MPZ, and SH3TC2 (both 9.9%), and MFN2 (8.3%). We further detected likely or known pathogenic variants in HINT1, HSPB1, NEFL, PRX, IGHMBP2, NDRG1, TTR, EGR2, FIG4, GDAP1, LMNA, LRSAM1, POLG, TRPV4, AARS, BIC2, DHTKD1, FGD4, HK1, INF2, KIF5A, PDK3, REEP1, SBF1, SBF2, SCN9A, and SPTLC2 with a declining frequency. Thirty-four novel variants were considered likely pathogenic not having previously been described in association with any disorder in the literature. In one patient, two homozygous mutations in HK1 were detected in the multigene panel, but not by whole exome sequencing. A novel missense mutation in KIF5A was considered pathogenic because of the highly compatible phenotype. In one patient, the plasma sphingolipid profile could functionally prove the pathogenicity of a mutation in SPTLC2. One pathogenic mutation in MPZ was identified after being previously missed by Sanger sequencing. We conclude that panel based next generation sequencing is a useful, time- and cost-effective approach to assist clinicians in identifying the correct diagnosis and enable causative treatment considerations.

Pompe disease is an autosomal recessive disorder caused by deficiency of the lysosomal α–1,4-glucosidase leading to accumulation of glycogen in target tissues with progressive organ failure. While the early infantile-onset form is characterized by early severe hypertrophic cardiomyopathy with cardiac and respiratory failure, clinically relevant cardiomyopathy seems to be uncommon in patients with late-onset Pompe disease, and the prevalence and nature of myocardial abnormalities are still to be clarified.

In juvenile or adult onset Pompe disease, non-invasive ventilation (NIV) is indicated if sleep-disordered breathing (SDB), daytime hypercapnia, or significant diaphragmatic weakness is present. We investigated both short-term and long-term effects of NIV on measures of sleep and nocturnal ventilation in patients with late-onset Pompe disease. Polysomnography (PSG) and transcutaneous capnography were performed in 22 adult patients with late-onset Pompe disease. If indicated, NIV was initiated the subsequent night and long-term follow-up visits were scheduled for up to 28 months including PSG and nocturnal carbon dioxide monitoring. Retrospective data analysis comprised PSG-based sleep and ventilation outcome measures. Daytime performance, subjective sleep quality, and health-related quality of life (HRQoL) were self-assessed using standard questionnaires. 22 patients (12 females) initially underwent detailed sleep studies. Enzyme replacement therapy had been initiated in 18 individuals, and 3 patients were treatment-naïve. 9 patients reported excessive daytime sleepiness (Epworth Sleepiness Scale score > 10), 8 patients had obstructive sleep apnea with an apnea hypopnea index above 5/h total sleep time, 3 patients showed daytime hypercapnia, and 4 individuals showed nocturnal increase of transcutaneous tcCO2 above 50 mmHg. In patients with SDB, HRQoL and both subjective and objective sleep quality were significantly reduced, the latter reflected by frequent sleep stage changes and decreased slow wave sleep. NIV was initiated in 15 patients and significantly increased mean and minimal oxygen saturation, shortened desaturation time, and enhanced CO2 elimination. Sleep outcomes were not significantly influenced in the first night on NIV but on first follow-up after three months nocturnal wake time was significantly decreased. During long-term follow-up sleep studies revealed stable normoxia and normocapnia in all patients receiving nighttime ventilatory support. Objective measures of sleep quality did not show deterioration over time. Alterations to ventilator settings were necessary only in few patients. NIV significantly improves objective sleep quality and respiration in the first night of treatment in adult patients with late-onset Pompe disease and SDB. NIV warrants nocturnal normoventilation without deterioration of sleep quality in the long run with only minor changes to ventilator settings.

STUDY OBJECTIVES:In neuromuscular disease, non-invasive ventilation (NIV) is indicated if sleep-disordered breathing (SDB) or significant respiratory muscle weakness (RMW) is present. We investigated immediate and long-term effects of NIV on sleep and nocturnal ventilation in patients with late-onset Pompe disease (LOPD). METHODS:Polysomnography and transcutaneous capnometry were performed in 22 adult patients. If indicated, NIV was initiated the subsequent night and follow-up sleep studies were scheduled. Sleep quality and health-related quality of life (HRQoL) were self-assessed using standard questionnaires. RESULTS:Fourteen patients received enzyme replacement therapy (ERT), five patients were treatment-naÏve, and three individuals had previously stopped ERT. Fifteen patients reported symptoms of SDB, all showing abnormal sleep studies. Two patients had obstructive sleep apnea (OSA), three patients showed both OSA and nocturnal hypercapnia, four individuals had nocturnal hypercapnia, and two patients had both OSA and daytime hypercapnia. Four patients showed normal apnea-hypopnea index and CO2 measures but nocturnal tachypnea, orthopnea, and significant RMW were present. Supine forced vital capacity (FVC) and positional drop of FVC were independent predictors of SDB. In patients with SDB, HRQoL was significantly reduced. NIV was initiated in 15 individuals and led to significant improvement of ventilation and oxygenation in the first night of treatment. Follow-up sleep studies revealed stable normoxia and normocapnia without deterioration of sleep outcomes for up to 40 months. CONCLUSIONS:In LOPD, SDB is common and comprises both hypoventilation and OSA. NIV significantly improves respiration already in the first night of treatment. NIV warrants nocturnal long-term normoventilation without deterioration of sleep quality.