Guideline for the management of myasthenic syndromes

Myasthenia gravis (MG), Lambert-Eaton myasthenic syndrome (LEMS), and congenital myasthenic syndromes (CMS) represent an etiologically heterogeneous group of (very) rare chronic diseases. MG and LEMS have an autoimmune-mediated etiology, while CMS are genetic disorders. A (strain dependent) muscle weakness due to neuromuscular transmission disorder is a common feature. Generalized MG requires increasingly differentiated therapeutic strategies that consider the enormous therapeutic developments of recent years. To include the newest therapy recommendations, a comprehensive update of the available German-language guideline 'Diagnostics and therapy of myasthenic syndromes' has been published by the German Neurological society with the aid of an interdisciplinary expert panel. This paper is an adapted translation of the updated and partly newly developed treatment guideline. It defines the rapid achievement of complete disease control in myasthenic patients as a central treatment goal. The use of standard therapies, as well as modern immunotherapeutics, is subject to a staged regimen that takes into account autoantibody status and disease activity. With the advent of modern, fast-acting immunomodulators, disease activity assessment has become pivotal and requires evaluation of the clinical course, including severity and required therapies. Applying MG-specific scores and classifications such as Myasthenia Gravis Activities of Daily Living, Quantitative Myasthenia Gravis, and Myasthenia Gravis Foundation of America allows differentiation between mild/moderate and (highly) active (including refractory) disease. Therapy decisions must consider age, thymic pathology, antibody status, and disease activity. Glucocorticosteroids and the classical immunosuppressants (primarily azathioprine) are the basic immunotherapeutics to treat mild/moderate to (highly) active generalized MG/young MG and ocular MG. Thymectomy is indicated as a treatment for thymoma-associated MG and generalized MG with acetylcholine receptor antibody (AChR-Ab)-positive status. In (highly) active generalized MG, complement inhibitors (currently eculizumab and ravulizumab) or neonatal Fc receptor modulators (currently efgartigimod) are recommended for AChR-Ab-positive status and rituximab for muscle-specific receptor tyrosine kinase (MuSK)-Ab-positive status. Specific treatment for myasthenic crises requires plasmapheresis, immunoadsorption, or IVIG. Specific aspects of ocular, juvenile, and congenital myasthenia are highlighted. The guideline will be further developed based on new study results for other immunomodulators and biomarkers that aid the accurate measurement of disease activity.

Sensitivity and specificity in signal detection with the reporting odds ratio and the information component

PURPOSE

As measures of association between an adverse drug reaction (ADR) and exposure to a drug the reporting odds ratio (ROR) and the information component (IC) can be used. We sought to test the reliability of signal detection with these.

METHODS

We simulated ADR counts as binomially distributed random numbers for different expected ADR frequencies and theoretical reporting odds ratios (RORs). We then calculated the empirical IC and the empirical ROR and their confidence intervals. The rate of signals that was detected despite a theoretical ROR of 1 represented the false positive rate, and represented the sensitivity if the ROR was >1.

RESULTS

For expected case counts below 1 the false positive rate oscillates from 0.01 to 0.1 even though 0.025 were intended. Even beyond expected case counts of 5 oscillations can cover a range of 0.018 to 0.035. The first n oscillations with the largest amplitude are eliminated if a minimum case count of n is required. To detect an ROR of 2 with a sensitivity of 0.8, a minimum of 12 expected ADRs are required. In contrast, 2 expected ADRs suffice to detect an ROR of 4.

CONCLUSION

Summaries of measures for disproportionality should include the expected number of cases in the group of interest if a signal was detected. If no signal was detected the sensitivity for the detection of a representative ROR or the minimum ROR that could be detected with probability 0.8 should be reported.

Myasthenia gravis with achalasia secondary to thymoma: a case report and literature review

Background

Myasthenia gravis is an autoimmune neuromuscular junction disorder characterized by fatigable muscle weakness and autoantibodies. Frequent associations exist between myasthenia gravis and thymic abnormalities, including hyperplasia and thymoma. Several autoimmune illnesses have been identified to be associated with thymoma; however, a few case reports have linked thymoma and achalasia, and the underlying mechanism is unknown.

Case report

A 43-year-old man with thymoma-associated myasthenia gravis presented with dysphagia that was refractory to conventional treatment of myasthenia gravis. This dysphagia was challenging to diagnose even after multiple gastroenterology consults and upper endoscopy. The diagnosis of achalasia type II was established after a comprehensive evaluation, including upper endoscopy, barium swallow, and high-resolution esophageal manometry. The patient underwent elective pneumatic balloon dilatation, which successfully alleviated his dysphagia.

Conclusion

This case confirmed the association between myasthenia gravis secondary to thymoma and achalasia and showed how the diagnosis of achalasia was challenging. Awareness of this association is crucial for early diagnosis and treatment, improving affected patients' quality of life.

The risk of worsening of myasthenia by cardiovascular medication as reflected by reporting frequency

BACKGROUND AND PURPOSE

Some groups of cardiovascular drugs (beta-blocking drugs, Ca antagonists, antiarrhythmics) are listed as potentially worsening myasthenia. An empirical basis for alternative recommendations for antihypertensive and antiarrhythmic therapy in myasthenia patients has not yet been provided.

METHODS

From the World Health Organization pharmacovigilance database, we retrieved total and myasthenia-related counts of adverse drug reactions for various groups of drugs used in cardiovascular disease and drugs with related mechanism of action used in other indications. We calculated the reporting odds ratio as a measure of a disproportional fraction of myasthenia-related events among all events. A 95% confidence interval of reporting odds ratio (ROR) >1 was taken as an indication for a higher risk. Because our approach involves a considerable number of tests, this situation is referred to as a signal that requires additional confirmation.

RESULTS

A signal for an increased risk was noted for tizanidine, for alpha-blocking drugs, for beta-blocking drugs, and for Ca antagonists. ROR indicated a lower-than-average risk for salbutamol, angiotensin receptor antagonists, oral anticoagulants, thrombocytic function inhibitors, and heparins.

CONCLUSIONS

Angiotensin receptor antagonists, angiotensin-converting enzyme inhibitors, and diuretics seem to be safe in antihypertensive therapy. Surprisingly, and yet requiring confirmation by case reports, alpha receptor-blocking drugs seem to carry a risk of myasthenia worsening. Amiodarone seems to be a safe alternative in antiarrhythmic therapy in patients with myasthenia.

Worsening of myasthenia due to antiepileptic, antipsychotic, antidepressant, and sedative medication: An estimation of risk based on reporting frequency

BACKGROUND AND PURPOSE

Many drugs can worsen myasthenia symptoms. The clinician usually relies on cautionary lists compiled according to case reports. We intended to provide a quantitative basis for a risk comparison within the groups of antiepileptic, antidepressant, neuroleptic, and sedative drugs.

METHODS

We extracted adverse drug reaction (ADR) counts (total and myasthenia related) for drugs from these groups and calculated the reporting odds ratio (ROR) within the drug groups from the World Health Organization pharmacovigilance database. For a given drug, the ROR was increased above 1 if the proportion of myasthenia-related ADRs for this drug was larger than the same proportion for the rest of drugs in that same group. If the 95% confidence interval of ROR was >1, this was taken as a signal for a higher risk of the given drug as compared to the average of the respective group.

RESULTS

Gabapentin, sertraline, citalopram, lithium, and amisulpride had a signal for the ROR to be increased above 1 within their respective groups. Bupropion, desvenlafaxine, duloxetine, escitalopram, and paroxetine had ROR values <1. For all other drugs, 1 was within the ROR confidence interval.

CONCLUSIONS

For gabapentin and lithium, the analysis of RORs confirmed case reports and cautionary lists. For a number of antidepressant drugs associated with a higher-than-average risk, no case reports exist substantiating our results. For these drugs, special attention should be paid to this risk. The remarkable difference between citalopram and escitalopram could prompt experimental work to confirm differential influence of the two preparations on neuromuscular transmission.