Transcriptome-based variant calling and aberrant mRNA discovery enhance diagnostic efficiency for neuromuscular diseases.

BACKGROUND: Whole-exome sequencing-based diagnosis of rare diseases typically yields 40%-50% of success rate. Precise diagnosis of the patients with neuromuscular disorders (NMDs) has been hampered by locus heterogeneity or phenotypic heterogeneity. We evaluated the utility of transcriptome sequencing as an independent approach in diagnosing NMDs. METHODS: The RNA sequencing (RNA-Seq) of muscle tissues from 117 Korean patients with suspected Mendelian NMD was performed to evaluate the ability to detect pathogenic variants. Aberrant splicing and CNVs were inspected to identify additional causal genetic factors for NMD. Aberrant splicing events in Dystrophin (DMD) were investigated by using antisense oligonucleotides (ASOs). A non-negative matrix factorisation analysis of the transcriptome data followed by cell type deconvolution was performed to cluster samples by expression-based signatures and identify cluster-specific gene ontologies. RESULTS: Our pipeline called 38.1% of pathogenic variants exclusively from the muscle transcriptomes, demonstrating a higher diagnostic rate than that achieved via exome analysis (34.9%). The discovery of variants causing aberrant splicing allowed the application of ASOs to the patient-derived cells, providing a therapeutic approach tailored to individual patients. RNA-Seq data further enabled sample clustering by distinct gene expression profiles that corresponded to clinical parameters, conferring additional advantages over exome sequencing. CONCLUSION: The RNA-Seq-based diagnosis of NMDs achieves an increased diagnostic rate and provided pathogenic status information, which is not easily accessible through exome analysis.

Risk factors for developing post-thymectomy myasthenia gravis in patients with thymoma.

BACKGROUND: Thymectomy is required for the treatment of thymoma-associated myasthenia gravis (MG). However, MG may develop only after thymectomy, a condition known as post-thymectomy MG. This study aimed to investigate the risk factors for post-thymectomy MG in patients with thymoma. METHODS: We retrospectively identified 235 patients with thymoma who underwent thymectomy at a single hospital from January 2008 to December 2017: 44 with preoperatively diagnosed MG were excluded, leaving 191 patients in the final analysis. Univariable survival analyses using Cox proportional hazards regression model and Kaplan-Meier estimate were conducted to identify risk factors for post-thymectomy MG. RESULTS: Post-thymectomy MG developed in 4.2% (8/191) of the patients with thymoma between 18 days and 108 mo after surgery. Hazard ratios (HRs) of pre- and postoperative anti-acetylcholine receptor antibody (AChR-Ab) titers were 2.267 (P = .002) and 1.506 (P < .001), respectively. Patients with extended thymectomy had a low chance of post-thymectomy MG (HR 0.035, P = .007). Larger thymoma (HR, 1.359; P = .005) and type A or AB thymoma according to World Health Organization histological classification (HR, 11.92; P = .021) were associated with higher chances of post-thymectomy MG. Within the subgroup of preoperatively AChR-Ab seropositive patients, post-thymectomy MG developed in 22.2% (6/27). CONCLUSIONS: Pre- and postoperative AChR-Ab levels should be measured in patients with thymoma. A large thymoma and partial thymectomy appear to be associated with a higher probability of post-thymectomy MG.

HyperCKemia in Guillain-Barré Syndrome.

The aim of the present study was to investigate the frequency and clinical features of Guillain-Barré syndrome (GBS) with hyperCKemia. We retrospectively identified 139 patients with GBS at 2 teaching hospitals in South Korea. We excluded patients with Miller-Fisher syndrome (n = 19), acute bulbar palsy (n = 3), and those whose serum creatine kinase (CK) levels were not measured (n = 45). Twelve of 72 patients (16.7%) had transient hyperCKemia, defined as serum CK ≥300 IU/L. The frequency of male sex and non-demyelinating electrodiagnostic features were higher in patients with hyperCKemia than those without. Transient hyperCKemia, occasionally seen in patients with GBS may be associated with the non-demyelinating subtype.

Electrodiagnostic data-driven clustering identifies a prognostically different subgroup of patients with chronic inflammatory demyelinating polyneuropathy.

OBJECTIVE: This study aimed to explore the correlations between electrodiagnostic (EDX) features in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and to investigate whether EDX data-driven clustering can identify a distinct subgroup regarding clinical phenotype and treatment response. METHODS: We reviewed clinical and EDX data of 56 patients with definite CIDP fulfilling the 2010 European Federation of Neurological Societies and Peripheral Nerve Society criteria at two teaching hospitals. A hierarchical agglomerative clustering algorithm with complete linkage was used to partition the patients into subgroups with similar EDX features. A stepwise logistic regression analysis was performed to evaluate predictors of the long-term outcome. RESULTS: EDX data-driven clustering partitioned the patients into two clusters, identifying a distinct subgroup characterised by coexistence of prominent conduction slowing and markedly reduced distally evoked compound muscle action potential (CMAP) amplitudes. This cluster of patients was significantly over-represented by an atypical subtype (distal acquired demyelinating symmetric polyneuropathy) compared with the other cluster (70% vs 26.1%, p=0.042). Furthermore, patients in this cluster invariably showed favourable long-term treatment outcome (100% vs 63%, p=0.023). In logistic regression analyses, the initial disability (OR 6.1, 95% CI 2.4 to 25.4), F-wave latency (OR 0.93, 95% CI 0.86 to 0.98) and distal CMAP duration (OR 0.96, 95% CI 0.91 to 0.99) were significant predictors of the poor long-term outcome. CONCLUSION: Our results show that EDX data-driven clustering could differentiate a pattern of EDX features with prognostic implication in patients with CIDP. Reduced distally evoked CMAPs may not necessarily predict poor responses to treatment, and active treatment is warranted when prominent slowing of conduction is accompanied in the distal segments.

Split-hand phenomenon in amyotrophic lateral sclerosis: A motor unit number index study.

INTRODUCTION: The split-hand phenomenon refers to preferential wasting of the thenar muscles with relative sparing of the hypothenar muscles in amyotrophic lateral sclerosis (ALS). METHODS: We compared the split-hand index (SI) calculated from the compound muscle action potential (CMAP; SICMAP ) with that calculated from the motor unit number index (MUNIX; SIMUNIX ). We performed MUNIX on the abductor policis brevis (APB), first dorsal interosseous (FDI), and abductor digiti minimi (ADM) muscles of 39 ALS patients and 40 age-matched, healthy controls. SI is derived by multiplying the CMAP (or MUNIX) recorded over the APB and FDI and dividing by the CMAP (or MUNIX) recorded over the ADM. RESULTS: Receiver-operating characteristic curve analysis revealed good diagnostic accuracy for both indices, but better performance of SIMUNIX than SICMAP . CONCLUSION: SIMUNIX and SICMAP were useful in differentiating ALS patients from healthy controls. SIMUNIX appears to be a better electrophysiological marker than SICMAP for the split-hand sign of ALS. Muscle Nerve 53: 885-888, 2016.

Motor unit number index (MUNIX) in the orbicularis oculi muscle of healthy subjects.

INTRODUCTION: The motor unit number index (MUNIX) refers to an electrophysiological method that measures the number of motor units in the surface electromyographic interference pattern (SIP) recorded during graded muscle contractions. MUNIX studies of limb muscles have been conducted, but MUNIX studies of bulbo-facial muscles have not been reported. METHODS: We assessed bilateral orbicularis oculi muscles using MUNIX, and the reference values and reproducibility of MUNIX and motor unit size index (MUSIX) were investigated in healthy subjects. RESULTS: In this study, MUNIX was applied successfully to the orbicularis oculi muscles and showed good reproducibility. The correlation coefficients for MUNIX and MUSIX were 0.803 and 0.592, respectively, and the coefficients of variation were 20.9% and 8.5%, respectively. CONCLUSIONS: The MUNIX procedure for the orbicularis oculi muscle would be a useful tool for evaluating bulbar symptoms, especially in amyotrophic lateral sclerosis.

Serum C3 complement levels predict prognosis and monitor disease activity in Guillain-Barré syndrome.

OBJECTIVE: Biomarkers are needed to predict prognosis and disease activity in patients with Guillain-Barré syndrome (GBS). The complement system is a key player in the pathogenesis of GBS. This study aimed to assess the potential utility of serum complement proteins as novel biomarkers in GBS. METHODS: We reviewed the medical records of 76 GBS patients with C3 and C4 measurements during hospitalization between 2010 and 2021. Clinical outcomes were correlated with baseline serum C3, C4, and seven additional predictors: four existing biomarkers (GM1, albumin, immunoglobulin G, neutrophil-lymphocyte ratio) and three clinical factors from the modified Erasmus GBS outcome score model. Five complement activation products (C3a, C4a, C5a, soluble C5b-9, factor Bb) were measured in 35 patients and were compared with C3 and C4 levels. Longitudinal changes in C3 and C4 levels were compared with the disease course in 12 patients. RESULTS: Higher C3, but not C4, was associated with poorer outcomes: lower Medical Research Council sum scores (MRCSS), higher GBS disability score (GBSDS), longer hospitalization, and more frequent treatment-related fluctuations. Age, MRCSS at admission, and baseline serum C3 were significant independent indicators of 1- and 3-month GBSDS. We found that C3 was positively correlated with C3a (r = 0.32) and C5a (r = 0.37), which indicates an activated complement cascade with high C3. Longitudinal change of C3 coincided with clinical severity of the disease course. INTERPRETATION: This study highlights the use of serum C3 as a novel mechanistic biomarker in GBS. Larger prospective studies are needed to validate our findings.

Safety and efficacy of clonazepam in patients with hemifacial spasm: A double-blind, randomized, placebo-controlled trial.

INTRODUCTION: Hemifacial spasm (HFS) is an involuntary intermittent twitching of the facial muscles. Medical and surgical treatments can be considered for HFS. Among medical treatments, clonazepam is a benzodiazepine used to treat epilepsy, psychiatric symptoms, and movement disorders. This study aimed to investigate the efficacy and safety of clonazepam for the treatment of HFS. METHODS: This randomized double-blind placebo-controlled trial prospectively enrolled patients with HFS aged 20-79 years. The patients were randomly assigned in a 1:1 ratio to receive either clonazepam (0.5 mg twice daily) or a placebo for 4 weeks. All participants underwent clinical assessment and laboratory tests at baseline and visit 2. The primary endpoint was the clinical global impression-improvement (CGI-I) score at visit 2. RESULTS: A total of 34 patients with HFS assessed for eligibility were enrolled between April 2015 and November 2016. Among them, two patients were withdrawn before randomization. Thus, the intention-to-treat analysis included 32 patients with HFS. The median CGI-I scores at visit 2 did not differ significantly between the clonazepam (3; range 1-6) and placebo (3.5; range 3-5) groups. In the safety analysis, only mild or no serious adverse events were observed. CONCLUSION: The results of this study demonstrated the safety of clonazepam in patients with HFS. However, clonazepam did not show a statistically significant effect on HFS. Further studies are needed to provide evidence of the clinical benefits in patients with HFS.

Skin Biopsy as a Novel Diagnostic Aid in Immune-Mediated Neuropathies.

Immune-mediated neuropathies are a heterogenous group of inflammatory peripheral nerve disorders. They can be classified according to the domain where the autoimmune process begins: the internode, paranode, or node. However, conventional diagnostic tools, electrodiagnosis (EDX), and autoantibody testing do not fully address this issue. In this institutional cohort study, we investigated the value of dermal myelinated fiber analysis for target domain-based classification. Twenty-seven consecutive patients with immune-mediated neuropathies underwent skin biopsies. The sections were stained with antibodies representative of myelinated fiber domains and were scanned using a confocal microscope. Clinical and pathological features of each patient were reviewed comprehensively. Quantitative morphometric parameters were subjected to clustering analysis, which stratified patients into 3 groups. Cluster 1 ("internodopathy") was characterized by prominent internodal disruption, intact nodes and paranodes, demyelinating EDX pattern, and absence of nodal-paranodal antibodies. Cluster 2 ("paranodopathy") was characterized by paranodal disruption and corresponding antibodies. Morphological changes were restricted to the nodes in cluster 3; we designated this cluster as "nodopathy." This report highlights the utility of skin biopsy as a diagnostic aid to gain pathogenic insight and classify patients with immune-mediated neuropathies.

Sensory Guillain-Barre syndrome following the ChAdOx1 nCov-19 vaccine: Report of two cases and review of literature.

Massive vaccination against COVID-19 has become a global priority. Simultaneously, concerns regarding the safety of vaccines are growing. We describe two patients who developed sensory Guillain-Barre syndrome (GBS) shortly after the first dose of the ChAdOx1 vaccine. We also summarize 12 published cases of GBS after ChAdOx1 vaccination, highlighting their unique clinical and paraclinical features. We propose a possible association between the risk of GBS and the ChAdOx1 vaccine and recommend surveillance for GBS following vaccination. Population-based studies are needed to determine causality and whether specific subpopulations are susceptible.

Guillain-Barré Syndrome and Variants Following COVID-19 Vaccination: Report of 13 Cases.

BACKGROUND: Amidst growing concern about an increased risk of Guillain-Barré syndrome (GBS) following COVID-19 vaccination, clinical and electrodiagnostic features have not been fully characterized. METHODS: We retrospectively reviewed medical records of the patients diagnosed with GBS and its variants following COVID-19 vaccination at four referral hospitals during the period of the mass vaccination program in South Korea (February to October 2021). RESULTS: We identified 13 patients with GBS and variants post COVID-19 vaccination: AstraZeneca vaccine (Vaxzevria) in 8, and Pfizer-BioNTech vaccine (Comirnaty) in 5. The mean time interval from vaccination to symptom onset was 15.6 days (range 4-30 days). Electrodiagnostic classification was demyelinating in 7, axonal in 4 and normal in 2 cases. Clinical manifestations were diverse with varying severity: classical GBS in 8 cases, paraparetic variant in 3, Miller-Fisher syndrome in 1 and acute cervicobrachial weakness in 1. Four patients developed respiratory failure, and 2 of them showed treatment-related fluctuations. CONCLUSION: Our observations suggest that COVID-19 vaccines may be associated with GBS of distinctive clinical features characterized by severe quadriplegia, disproportionately frequent bilateral facial palsy or atypical incomplete variants. Continuous surveillance and further studies using robust study designs are warranted to fully assess the significance of the association.

EBI2-expressing B cells in neuromyelitis optica spectrum disorder with AQP4-IgG: Association with acute attacks and serum cytokines.

Epstein-Barr virus-induced G-protein coupled receptor 2 (EBI2) is important in regulating B cell activation. We investigated whether EBI2 expression on B cells is associated with acute attacks in neuromyelitis optica spectrum disorder with aquaporin-4 IgG (AQP4-IgG(+) NMOSD). Blood samples were collected from patients with AQP4-IgG(+) NMOSD, multiple sclerosis (MS), and patients without inflammatory demyelinating diseases (non-IDD controls). CD19+ B cells and CD4+ T cells were analyzed for surface expression of EBI2. Serum cytokine levels were also analyzed. The EBI2+CD19+ to EBI2-CD19+ cell ratio was significantly higher in patients with AQP4-IgG(+) NMOSD enrolled within 2 months of an attack than in those with non-IDDs (p = 0.007) and MS (p = 0.003). Patients with AQP4-IgG(+) NMOSD enrolled within 2 months of an attack had a higher EBI2+CD19+ cell frequency than patients with AQP4-IgG(+) NMOSD enrolled 2 months after a recent attack (p = 0.001). The EBI2+CD19+ cell frequency was positively correlated with interleukin (IL)-6 and IL-10. EBI2 expression on B cells could be associated with acute attacks of AQP4-IgG(+) NMOSD, possibly through IL-6- or IL-10-related pathways.

Dissociated leg muscle atrophy in amyotrophic lateral sclerosis/motor neuron disease: the 'split-leg' sign.

Disproportionate muscle atrophy is a distinct phenomenon in amyotrophic lateral sclerosis (ALS); however, preferentially affected leg muscles remain unknown. We aimed to identify this split-leg phenomenon in ALS and determine its pathophysiology. Patients with ALS (n = 143), progressive muscular atrophy (PMA, n = 36), and age-matched healthy controls (HC, n = 53) were retrospectively identified from our motor neuron disease registry. We analyzed their disease duration, onset region, ALS Functional Rating Scale-Revised Scores, and results of neurological examination. Compound muscle action potential (CMAP) of the extensor digitorum brevis (EDB), abductor hallucis (AH), and tibialis anterior (TA) were reviewed. Defined by CMAPEDB/CMAPAH (SIEDB) and CMAPTA/CMAPAH (SITA), respectively, the values of split-leg indices (SI) were compared between these groups. SIEDB was significantly reduced in ALS (p < 0.0001) and PMA (p < 0.0001) compared to the healthy controls (HCs). SITA reduction was more prominent in PMA (p < 0.05 vs. ALS, p < 0.01 vs. HC), but was not significant in ALS compared to the HCs. SI was found to be significantly decreased with clinical lower motor neuron signs (SIEDB), while was rather increased with clinical upper motor neuron signs (SITA). Compared to the AH, TA and EDB are more severely affected in ALS and PMA patients. Our findings help to elucidate the pathophysiology of split-leg phenomenon.

High neutrophil-to-lymphocyte ratio predicts short survival duration in amyotrophic lateral sclerosis.

The present study aimed to investigate the prognostic importance of the neutrophil-to-lymphocyte ratio (NLR) in patients with amyotrophic lateral sclerosis (ALS). Among 322 patients diagnosed as having definite, probable, or possible ALS at a single tertiary hospital, 194 patients were included in the final analysis. Patients were divided into three groups (T1, T2, and T3) according to the tertile of their NLR. Survival rate was significantly lower in T3 compared to the other groups (log-rank test; T1 vs. T3, p = 0.009; T2 vs. T3, p = 0.008). Median survival duration was 37.0 (24.0-56.0), 32.5 (19.5-51.2), and 22.0 (17.0-38.0) months in T1, T2, and T3, respectively. In a multivariable Cox proportional hazards regression analysis, the hazard ratio of age at onset, bulbar-onset, and NLR (T3/T1) was 1.04 (1.02-1.06, p < 0.001), 1.68 (1.10-2.57, p = 0.015), and 1.60 (1.01-2.51, p = 0.041), respectively. A high baseline NLR may serve as a useful indicator for short survival duration in patients with ALS.

Downregulated miR-18b-5p triggers apoptosis by inhibition of calcium signaling and neuronal cell differentiation in transgenic SOD1 (G93A) mice and SOD1 (G17S and G86S) ALS patients.

BACKGROUND: MicroRNAs (miRNAs) are endogenous non-coding RNAs that regulate gene expression at the post-transcriptional level and are key modulators in neurodegenerative diseases. Overexpressed miRNAs play an important role in ALS; however, the pathogenic mechanisms of deregulated miRNAs are still unclear. METHODS: We aimed to assess the dysfunction of RNAs or miRNAs in fALS (SOD1 mutations). We compared the RNA-seq of subcellular fractions in NSC-34 WT (hSOD1) and MT (hSOD1 (G93A)) cells to find altered RNAs or miRNAs. We identified that Hif1α and Mef2c were upregulated, and Mctp1 and Rarb were downregulated in the cytoplasm of NSC-34 MT cells. RESULTS: SOD1 mutations decreased the level of miR-18b-5p. Induced Hif1α which is the target for miR-18b increased Mef2c expression as a transcription factor. Mef2c upregulated miR-206 as a transcription factor. Inhibition of Mctp1 and Rarb which are targets of miR-206 induces intracellular Ca2+ levels and reduces cell differentiation, respectively. We confirmed that miR-18b-5p pathway was also observed in G93A Tg, fALS (G86S) patient, and iPSC-derived motor neurons from fALS (G17S) patient. CONCLUSIONS: Our data indicate that SOD1 mutation decreases miR-18b-5p, which sequentially regulates Hif1α, Mef2c, miR-206, Mctp1 and Rarb in fALS-linked SOD1 mutation. These results provide new insights into the downregulation of miR-18b-5p dependent pathogenic mechanisms of ALS.

Infarction in the territory of anterior inferior cerebellar artery: spectrum of audiovestibular loss.

BACKGROUND AND PURPOSE: To define the detailed spectrum of audiovestibular dysfunction in anterior inferior cerebellar artery territory infarction. METHODS: Over 8.5 years, we prospectively identified 82 consecutive patients with anterior inferior cerebellar artery territory infarction diagnosed by MRI. Each patient completed a standardized audiovestibular questionnaire and underwent a neuro-otologic evaluation, including bithermal caloric tests and pure tone audiogram. RESULTS: All but 2 (80 of 82 [98%]) patients had acute prolonged vertigo and vestibular dysfunction of peripheral, central, or combined origin. The most common pattern of audiovestibular dysfunction was the combined loss of auditory and vestibular function (n=49 [60%]). A selective loss of vestibular (n=4 [5%]) or cochlear (n=3 [4%]) function was rarely observed. We could classify anterior inferior cerebellar artery territory infarction into 7 subgroups according to the patterns of neuro-otological presentations: (1) acute prolonged vertigo with audiovestibular loss (n=35); (2) acute prolonged vertigo with audiovestibular loss preceded by an episode(s) of transient vertigo/auditory disturbance within 1 month before the infarction (n=13); (3) acute prolonged vertigo and isolated auditory loss without vestibular loss (n=3); (4) acute prolonged vertigo and isolated vestibular loss without auditory loss (n=4); (5) acute prolonged vertigo but without documented audiovestibular loss (n=24); (6) acute prolonged vertigo and isolated audiovestibular loss without any other neurological symptoms/signs (n=1); and (7) nonvestibular symptoms with normal audiovestibular function (n=2). CONCLUSIONS: Infarction in the anterior inferior cerebellar artery territory can present with a broad spectrum of audiovestibular dysfunctions. Unlike a viral cause, labyrinthine dysfunction of a vascular cause usually leads to combined loss of both auditory and vestibular functions.

B Cell Immunophenotyping and Transcriptional Profiles of Memory B Cells in Patients with Myasthenia Gravis.

Myasthenia gravis (MG) is an autoimmune neuromuscular junction disorders mediated by various autoantibodies. Although most patients with MG require chronic immunosuppressive treatment to control disease activity, appropriate surveillance biomarkers that monitor disease activity or potential toxicity of immunosuppressants are yet to be developed. Herein, we investigated quantitative distribution of peripheral blood B cell subsets and transcriptional profiles of memory B cells (CD19+ CD27+) in several subgroups of MG patients classified according to the Myasthenia Gravis Foundation of America (MGFA) Clinical Classification. This study suggests potential immunologic B-cell markers that may guide treatment decision in future clinical settings.

Repeated low-dose rituximab treatment based on the assessment of circulating B cells in patients with refractory myasthenia gravis.

BACKGROUND: The objective of this study was to evaluate the efficacy and safety of repeated low-dose rituximab treatment guided by monitoring circulating CD19+ B cells in patients with refractory myasthenia gravis (MG). METHODS: Patients with refractory MG who had received rituximab treatment at two teaching hospitals between September 2013 and January 2017 were reviewed retrospectively. The treatment protocol consisted of an induction treatment with low-dose rituximab (375 mg/m2 twice with a 2-week interval), followed by retreatment (375 mg/m2 once). Retreatment was based on either circulating CD19+ B-cell repopulation or clinical relapse. Outcome measures included the MG Foundation of America (MGFA) clinical classification and postintervention status, prednisolone dose, CD19+ B-cell counts, clinical relapse, and adverse effects. RESULTS: Of 17 patients, 11 (65%) achieved the primary endpoint, defined as the minimal manifestation or better status with prednisolone ⩽5 mg/day, after median 7.6 months (range, 2-17 months) following rituximab treatment. Over a median follow up of 24 months (range, 7-49 months), a total of 30 retreatments were undertaken due to clinical relapse without B-cell repopulation (n = 6), on the basis of B-cell repopulation alone (n = 16) and both (n = 8). B-cell recovery appeared to be in parallel with clinical relapse on the group level, although the individual-level association appeared to be modest, with B-cell repopulation observed only at 57% (8/14) of clinical relapses. CONCLUSIONS: The repeated low-dose rituximab treatment based on the assessment of circulating B-cell depletion could be a cost-effective therapeutic option for refractory MG. Further studies are needed to verify the potentially better cost-effectiveness of low-dose rituximab, and to identify biomarkers that help optimize treatment in MG patients.