The Duke Myasthenia Gravis Clinic Registry: II. Analysis of outcomes.

INTRODUCTION/AIMS: The Duke Myasthenia Gravis (MG) Clinic Registry contains comprehensive physician-derived data on patients with MG seen in the Duke MG Clinic since 1980. The aim of this study was to report outcomes in patients seen in the clinic and treated according to the International Consensus Guidance statements. METHODS: This is a retrospective cohort study of patients initially seen after 2000 and followed for at least 2 years in the clinic. Treatment goal (TG) was defined as achieving MGFA post-intervention status of "minimal manifestations" or better; PIS was determined by the treating neurologist. Time-to-event analysis, including Cox proportional hazards modeling, was performed to assess the effect of sex, acetylcholine receptor antibody (AChR-Ab) status, age at disease onset, distribution (ocular vs generalized), thymectomy, and thymoma on the time to achieve TG. RESULTS: Among the 367 cohort patients, 72% achieved TG (median time less than 2 years). A greater proportion of patients with AChR-Abs and thymectomy achieved TG and they did so sooner than patients without these antibodies or thymectomy. Otherwise, there were no significant differences in these findings within the tested subgroups. The disease duration at the first Duke Clinic visit was shorter in patients who achieved TG than in those who did not. DISCUSSION: These results demonstrate outcomes that can be achieved in patients with MG treated according to the current Consensus Guidance statements. Among other things, they can be used to determine the added value and potential role of new treatment modalities developed since 2018.

Pregnancy in MuSK-positive myasthenia gravis: A single-center case series.

INTRODUCTION/AIMS: Myasthenia gravis (MG) with muscle-specific tyrosine kinase (MuSK) antibodies (MMG) is predominantly seen in women of childbearing age. Our objective in this study was to describe the course of MMG during pregnancy and within 6 months postpartum, and to document any effect on fetal health. METHODS: A retrospective review was performed of medical records of patients with MMG seen in the Duke Myasthenia Gravis Clinic from 2003 to 2022. MMG patients with onset of MMG symptoms before or during pregnancy as well as within 6 months postpartum were reviewed. RESULTS: A total of 14 pregnancies in 10 patients were included in our study cohort. Initial MG symptoms developed during pregnancy or within 6 months postpartum in six patients. Four patients had two pregnancies, three of whom developed MG during their first pregnancy. In the patients diagnosed before pregnancy, MG symptoms increased in five of eight patients during pregnancy or postpartum. Four patients required rescue therapy with plasma exchange or intravenous immunoglobulin during pregnancy or postpartum. One patient had a cesarean section after prolonged labor due to failure of progression. There were no other complications of pregnancy or delivery, and all infants were healthy at delivery. DISCUSSION: As in non-MuSK MG, women with MMG may also have worsening or may develop initial MG symptoms during pregnancy or within 6 months postpartum. More aggressive medical therapy may be required for pregnant patients with MMG. Further study is needed to identify the mechanism and risk of worsening of MMG during pregnancy or postpartum.

The Duke myasthenia gravis clinic registry: I. Description and demographics.

INTRODUCTION: The Duke Myasthenia Gravis (MG) Clinic Registry is a disease-specific database containing physician-derived data from patients seen in the Duke MG Clinic since 1980. METHODS: Data from 1060 MG patients initially seen between 1980 and 2008 were reviewed. RESULTS: Fifty-four percent were male. Symptoms began after age 50 in 66% of males and 42% of females. Peak onset age in males was in their 60's; females had no predominant onset age. Onset age for both sexes increased from 1980 to 2008. Thymoma was present in 8.5%. Weakness was limited to ocular muscles for at least 2 y in 22% and became generalized later in 8.3% of these. Acetylcholine receptor antibodies were present in 78% overall, 82% with generalized MG and 52% with ocular MG (OMG). The distribution of MG disease class was similar in males and females, except that a greater proportion of women experienced myasthenic crisis and men were more likely to have OMG. DISCUSSION: Data in the Registry permit comprehensive and longitudinal analysis of a validated MG population. Analysis of Registry data shows that the frequency of AChR antibody negative MG, ocular MG, and thymoma are similar to other reports, but the onset age and proportion of males have progressively increased compared to studies published more than 20 y ago. These observations demonstrate the value of collecting comprehensive clinical information and comparing historic and contemporary populations. Other potential uses of Registry data include comparison of outcome measures in different disease subgroups and the response to specific treatments.

Knowledge and perceptions of the COVID-19 pandemic among patients with myasthenia gravis.

BACKGROUND: Patients with myasthenia gravis (MG) may be particularly vulnerable during the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic due to risk of worsening disease during infection, potential adverse impacts of coronavirus disease 2019 (COVID-19) treatments on neuromuscular transmission, and a limited ability to fight off infection related to immunosuppressive treatments. Our goal is to understand how patients are experiencing the COVID-19 pandemic, including where they receive relevant information, how it has affected medical care, and what measures they use to protect themselves. METHODS: This is a prospective online survey study at large academic practice. All patients with a neuromuscular junction disorder diagnosis code in the Duke Health System were invited to participate. RESULTS: One thousand eight hundred and forty eight patients were approached to participate and 75 completed the survey between 16 April 2020 and 28 May 2020. The most frequently used information sources were non-presidential federal government (75%), state government (57%), local healthcare provider (37%), and television news (36%). Non-presidential federal government (80%), local healthcare providers (55%), state government (33%), and patient support organizations (29%) were considered the most trusted information sources. Thirty-three (44%) of survey responders had attended a telemedicine visit. Patients were taking recommended precautions during the pandemic and remained very concerned (69%) about COVID-19. Generalized Anxiety Disorder-7 scores were moderate-severe in 20% of responders. CONCLUSIONS: Healthcare providers, the government, and patient organizations play a critical role in communicating with the MG patient community. Use of targeted messaging strategies by these groups to convey accurate information may increase effectiveness and lead to more informed patients with reduced anxiety.

Reduced plasmablast frequency is associated with seronegative myasthenia gravis.

BACKGROUND: The immunopathology of autoimmune seronegative myasthenia gravis (SN MG) is poorly understood. Our objective was to determine immune profiles associated with a diagnosis of SN MG. METHODS: We performed high-dimensional flow cytometry on blood samples from SN MG patients (N = 68), healthy controls (N = 46), and acetylcholine receptor antibody (AChR+) MG patients (N = 27). We compared 12 immune cell subsets in SN MG to controls using logistic modeling via a discovery-replication design. An exploratory analysis fit a multinomial model comparing AChR+ MG and controls to SN MG. RESULTS: An increase in CD19+ CD20- CD38hi plasmablast frequencies was associated with lower odds of being a SN MG case in both the discovery and replication analyses (discovery P-value = .0003, replication P-value = .0021). Interleukin (IL) -21 producing helper T cell frequencies were associated with a diagnosis of AChR+ MG (P = .004). CONCLUSIONS: Reduced plasmablast frequencies are strongly associated with a SN MG diagnosis and may be a useful diagnostic biomarker in the future.

Validation of the triple timed up-and-go test in Lambert-Eaton myasthenia.

INTRODUCTION: There are no validated, practical, and quantitative measures of disease severity in Lambert-Eaton myasthenia (LEM). METHODS: Data from the Effectiveness of 3,4-Diaminopyridine in Lambert-Eaton Myasthenic Syndrome (DAPPER) trial were analyzed to assess triple timed up-and-go (3TUG) reproducibility and relationships between 3TUG times and other measures of LEM severity. RESULTS: The coverage probability technique showed ≥0.90 probability for an acceptable 3TUG difference of ≤0.2, indicating that it is reproducible in LEM patients. The correlation between 3TUG times and lower extremity function scores was significant in subjects who continued and in those who were withdrawn from 3,4-diaminopyridine free base. Worsening patient-reported Weakness Self-Assessment Scale and Investigator Assessment of Treatment Effect scores corresponded with prolongation of 3TUG times. DISCUSSION: The 3TUG is reproducible, demonstrates construct validity for assessment of lower extremity function in LEM patients, and correlates with changes in patient and physician assessments. These findings, along with prior reliability studies, indicate 3TUG is a valid measure of disease severity in LEM.

3,4-diaminopyridine base effectively treats the weakness of Lambert-Eaton myasthenia.

INTRODUCTION: 3,4-diaminopyridine has been used to treat Lambert-Eaton myasthenia (LEM) for 30 years despite the lack of conclusive evidence of efficacy. METHODS: We conducted a randomized double-blind placebo-controlled withdrawal study in patients with LEM who had been on stable regimens of 3,4-diaminopyridine base (3,4-DAP) for ≥ 3 months. The primary efficacy endpoint was >30% deterioration in triple timed up-and-go (3TUG) times during tapered drug withdrawal. The secondary endpoint was self-assessment of LEM-related weakness (W-SAS). RESULTS: Thirty-two participants were randomized to continuous 3,4-DAP or placebo groups. None of the 14 participants who received continuous 3,4-DAP had > 30% deterioration in 3TUG time versus 72% of the 18 who tapered to placebo (P < 0.0001). W-SAS similarly demonstrated an advantage for continuous treatment over placebo (P < 0.0001). Requirement for rescue and adverse events were more common in the placebo group. DISCUSSION: This trial provides significant evidence of efficacy of 3,4-DAP in the maintenance of strength in LEM. Muscle Nerve 57: 561-568, 2018.

Reliability of the triple-timed up-and-go test.

INTRODUCTION: We report the reliability of a new measure, the triple-timed up-and-go (3TUG) test, for assessing clinical function in patients with Lambert-Eaton myasthenia (LEM). METHODS: Intrarater reproducibility and interrater agreement of the 3TUG test were assessed in 25 control participants, 24 patients with non-LEM neuromuscular disease, and 12 patients with LEM. The coverage probability (CP) method was the primary measure of reproducibility and agreement. The a priori acceptable range was < 20% difference in 3TUG test times and a CP ≥0.90 confirmed agreement. RESULTS: CP values > 0.90 for intrarater and interrater tests confirmed acceptable reproducibility and agreement for all groups. DISCUSSION: The 3TUG test is a quick, noninvasive, and reproducible measure that is easy to perform, measures clinically important weakness in LEM patients, and requires little training. Additional evaluation in a larger number of LEM patients is in progress to validate the 3TUG test as a clinical measure in LEM. Muscle Nerve 57: 136-139, 2017.

International clinimetric evaluation of the MG-QOL15, resulting in slight revision and subsequent validation of the MG-QOL15r.

INTRODUCTION: The MG-QOL15 is a validated, health-related quality of life (HRQOL) measure for myasthenia gravis (MG). Widespread use of the scale gave us the opportunity to further analyze its clinimetric properties. METHODS: We first performed Rasch analysis on >1,300 15-item Myasthenia Gravis Quality of Life scale (MG-QOL15) completed surveys. Results were discussed during a conference call with specialists and biostatisticians. We decided to revise 3 items and prospectively evaluate the revised scale (MG-QOL15r) using either 3, 4, or 5 responses. Rasch analysis was then performed on >1,300 MG-QOL15r scales. RESULTS: The MGQOL15r performed slightly better than the MG-QOL15. The 3-response option MG-QOL15r demonstrated better clinimetric properties than the 4- or 5-option scales. Relative distributions of item and person location estimates showed good coverage of disease severity. CONCLUSIONS: The MG-QOL15r is now the preferred HRQOL instrument for MG because of improved clinimetrics and ease of use. This revision does not negate previous studies or interpretations of results using the MG-QOL15. Muscle Nerve 54: 1015-1022, 2016.

Do acetylcholine receptor and striated muscle antibodies predict the presence of thymoma in patients with myasthenia gravis?

INTRODUCTION: Acetylcholine receptor (AChR) and striated muscle antibodies (StrAbs) are found frequently in myasthenia gravis (MG) patients with thymoma. In this study we aimed to determine the positive predictive value (PPV) and negative predictive value (NPV) of these antibodies for thymoma in patients with MG. METHODS: Antibody findings, thymic histology, and onset age were reviewed for 1141 patients with MG. PPV and NPV of these antibodies for thymoma were determined. RESULTS: The PPV of AChR binding antibodies plus StrAbs was highest (50.0%) with onset before the age of 40 years. The PPV of all antibodies was low (<9%) after age 40. Higher StrAb levels did not increase the PPV. The NPV of AChR binding antibodies was high (99.7%) for all ages. CONCLUSIONS: Patients without AChR binding antibody are not likely to have a thymoma. StrAbs and AChR binding antibodies are not diagnostic for thymoma, but in early-onset MG their presence should raise the clinical suspicion for thymoma.

Does change in acetylcholine receptor antibody level correlate with clinical change in myasthenia gravis?

INTRODUCTION: The objective of this study is to determine if change in acetylcholine receptor antibody (AChR-ab) levels reflects change in clinical severity in patients with myasthenia gravis (MG). METHODS: We reviewed results from a prospective trial in MG and from all 85 patients in an MG Clinic who had AChR-ab determinations performed at least twice by the same commercial laboratory. RESULTS: Change in AChR-ab levels correlated only weakly with change in clinical severity. AChR-ab levels fell in 92% of patients who improved and in 63% who did not. A fall in AChR-ab level had a positive predictive value for clinical improvement of 83% and a negative predictive value of only 59%. CONCLUSIONS: AChR-ab levels fell in almost all patients who improved, but also in most patients who did not. Thus, we do not recommend commercially available AChR-ab levels as a biomarker of improvement in MG. However, antibody levels might be useful as a marker for inadequate immunotherapy.

Immune dysregulation in chronic inflammatory demyelinating polyneuropathy.

OBJECTIVE: Chronic inflammatory demyelinating polyneuropathy (CIDP) is an autoimmune disorder of the peripheral nerves with an incompletely understood underlying pathophysiology. This investigation focused on defining B and T cell frequencies, T cell functional capacity and innate immune system analysis in patients with CIDP. METHODS: By using multi-parameter flow cytometry, we examined the phenotype and function of PBMCs in 25 CIDP patients who were relatively clinically stable on treatment who met EFNS/PNS criteria, 21 patients with genetically confirmed hereditary neuropathy and 25 healthy controls. We also evaluated the regulatory T cell (Treg) inhibitory capacity by co-culturing Treg and effector T cells. RESULTS: Proinflammatory CD4 T cells, especially type 1 helper T cell (Th1) and CD8 T cells in patients with CIDP were found to have an enhanced capacity to produce inflammatory cytokines. There was no difference in frequency of Th17 regulatory cells in CIDP patients versus healthy controls, however, Treg function was impaired in CIDP patients. There was no remarkable difference in innate immune system measures. Within B cell subsets, transitional cell frequency was decreased in CIDP patients. INTERPRETATION: Patients with CIDP clinically stable on treatment continued to show evidence of a proinflammatory state with impaired Treg function. This potentially implies an inadequate suppression of ongoing inflammation not addressed by standard of care therapies as well as persistent activity of disease while on treatment. Targeting T cells, especially inhibiting Th1 and polyfunctional CD8 T cells or improving Treg cell function could be potential targets for future therapeutic research.

Nerve ultrasound in diabetic polyneuropathy: correlation with clinical characteristics and electrodiagnostic testing.

INTRODUCTION: Diabetic polyneuropathy (DPN) is increasingly prevalent in the USA, but nerve ultrasound (US) findings have not been assessed systematically. Our aim was to establish the sonographic characteristics of lower extremity nerves in DPN and correlate them with electrodiagnostic (EDx) findings. METHODS: Consecutive patients (n = 25) with evidence of DPN and 25 patient controls without DPN underwent blinded US imaging of the fibular and sural nerves. Nerve cross-sectional area (CSA), diameter and echogenicity were recorded. RESULTS: There were no differences in fibular or sural nerve CSA, diameter, or echogenicity between the 2 groups. No correlations between nerve CSA and EDx studies were found. In DPN, there were moderate inverse correlations with age (r = -0.44 sural ankle, r = -0.39 sural leg, r = -0.45 fibular ankle). CONCLUSIONS: US measurements of lower extremity nerves in DPN do not differ from controls or correlate with EDx findings. Novel US techniques and/or pedal nerve US may be necessary to detect differences.

A retrospective study of complications of therapeutic plasma exchange in myasthenia.

INTRODUCTION: Venous access for therapeutic plasma exchange (TPE) in myasthenia gravis (MG) can be achieved by central venous catheters (CVC) or peripheral veins (PV), and the preferred method varies among providers. We evaluated our institutional experience with TPE venous access method and complications. METHODS: We reviewed all TPE-treated MG patients (2005-2010) through blinded chart review. TPE complications were categorized as serious or minor. Serious complications ended the procedure and/or were potentially life-threatening. RESULTS: A total of 134 MG patients received 230 TPE courses; 56% were outpatient procedures. Whenever feasible, TPE was performed by PV access, which was successful in 75% of courses. Over 90% in both groups improved after TPE. Compared with PV access, CVCs were associated with more total (68% vs. 35%) and serious complications (41% vs. 4%), including 2 deaths. CONCLUSIONS: PV access for TPE can be used successfully in most MG patients and may reduce morbidity of the procedure.

A randomized, double-blind, placebo-controlled phase II study of eculizumab in patients with refractory generalized myasthenia gravis.

INTRODUCTION: Complement activation at the neuromuscular junction is a primary cause of acetylcholine receptor loss and failure of neuromuscular transmission in myasthenia gravis (MG). Eculizumab, a humanized monoclonal antibody, blocks the formation of terminal complement complex by specifically preventing the enzymatic cleavage of complement 5 (C5). METHODS: This study was a randomized, double-blind, placebo-controlled, crossover trial involving 14 patients with severe, refractory generalized MG (gMG). RESULTS: Six of 7 patients treated with eculizumab for 16 weeks (86%) achieved the primary endpoint of a 3-point reduction in the quantitative myasthenia gravis (QMG) score. Examining both treatment periods, the overall change in mean QMG total score was significantly different between eculizumab and placebo (P = 0.0144). After assessing data obtained from all visits, the overall change in mean QMG total score from baseline was found to be significantly different between eculizumab and placebo (P < 0.0001). Eculizumab was well tolerated. CONCLUSION: The data suggest that eculizumab may have a role in treating severe, refractory MG.

Pregnancy in Seronegative Myasthenia Gravis: A Single-Center Case Series.

INTRODUCTION: The course of double-seronegative myasthenia gravis (DSNMG) during and after pregnancy has not been well described. OBJECTIVE: To assess the course of DSNMG during pregnancy and within 6 months postpartum. METHODS: A retrospective cohort study of women with DSNMG seen in the Duke Myasthenia gravis (MG) Clinic after 2003. RESULTS: Review of the Duke MG Clinic Registry and electronic medical record identified 8 patients who became pregnant after MG onset; the mean age at disease onset was 17.6 (SD = 10.0) years. Increased MG symptoms were observed in the first and third trimester and, most commonly, postpartum in 6 of 18 pregnancies. Except for 1 infant who developed respiratory distress that required neonatal intensive care admission, all the newborns were healthy at birth. CONCLUSIONS: As in seropositive MG, increased MG symptoms during pregnancy and within 6 months postpartum is also seen in women with DSNMG.

Clinicoserological insights into patients with immune checkpoint inhibitor-induced myasthenia gravis.

To compare the immunopathology of immune checkpoint inhibitor-induced myasthenia gravis (ICI-MG) and idiopathic MG, we profiled the respective AChR autoantibody pathogenic properties. Of three ICI-MG patients with AChR autoantibodies, only one showed complement activation and modulation/blocking potency, resembling idiopathic MG. In contrast, AChR autoantibody-mediated effector functions were not detected in the other two patients, questioning the role of their AChR autoantibodies as key mediators of pathology. The contrasting properties of AChR autoantibodies in these cases challenge the accuracy of serological testing in establishing definite ICI-MG diagnoses and underscore the importance of a thorough clinical assessment when evaluating ICI-related adverse events.

Median nerve ultrasound as a screening tool in carpal tunnel syndrome: correlation of cross-sectional area measures with electrodiagnostic abnormality.

INTRODUCTION: Sonographically measured median nerve cross-sectional area (CSA) at the wrist is increased in patients with carpal tunnel syndrome (CTS). Ultrasound of the median nerve may be useful in screening for electrodiagnostic (EDx) abnormalities. METHODS: EDx studies were performed on all participants. Sonographic evaluation of median nerve CSA at the wrist and in the forearm was performed by a physician blinded to the EDx results. Multivariate and receiver operating characteristic (ROC) analysis were used to assess the data. RESULTS: Fifty control wrists and 192 symptomatic wrists were analyzed. Sensitivity of ultrasound in excluding EDx abnormality was 99% for CSA of 9 mm(2) and 97% for a wrist-forearm ratio (WFR) of 1.4. There was no clinically significant correlation between ultrasound parameters and EDx severity. CONCLUSIONS: Median nerve ultrasound is a highly sensitive screening tool for EDx abnormality, but it cannot determine severity. This may lead to changes in the current standards for evaluating CTS.