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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., (© 2020 Wiley Periodicals LLC.)

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between 3TUG times and lower extremity function scores was significant in subjects who continued and in those who were withdrawn from 3,4-diaminopyridine free base.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., (© 2019 Wiley Periodicals, Inc.)

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., (© 2017 The Authors Muscle & Nerve Published by Wiley Periodicals, Inc.)

The safety factor of neuromuscular transmission can be assessed by measuring the neuromuscular jitter, which reflects the time variability of processes in the motor end-plate. Jitter is increased in any condition with disturbed end-plate function, such as myasthenic conditions and ongoing reinnervation. Jitter is increasingly being measured with concentric needle (CN) electrodes, which are more prone to artefacts than single fiber EMG recordings. The objective of this review is to identify and demonstrate pitfalls that can be seen with CN jitter measurements, made with both voluntary activation and electrical stimulation. With voluntary activation, errors are caused by poor signal quality; inappropriate time reference points on the signal; an irregular firing rate; and signals with dual latencies, i.e., “flip-flop.” With electrical stimulation, additional errors result from insufficient stimulation intensity; from abrupt change in firing rate; and from axon reflexes. Many pitfalls cannot be avoided during recording and can only be detected during post-processing. It is critical to be aware of these artefacts when measuring jitter with CN electrodes. [ABSTRACT FROM AUTHOR]