Single-fiber electromyography in the orbicularis oculi muscle in patients with ocular myasthenia gravis symptoms: does abnormal jitter predict response to treatment?

Using jitter analysis with concentric needle electrodes to assess disease status and treatment responses in myasthenia gravis

Objective

This study assesses the utility of jitter analysis with concentric needles to evaluate disease severity in myasthenia gravis (MG), correlate changes in jitter with clinical status as well as identify reasons for any discordance.

Methods

We performed a retrospective chart review of 82 MG patients and extracted data on demographics, MG subtype, antibody status, clinical scales, electrophysiology, and interventions at baseline and follow-up.

Results

Baseline MGII scores correlated with jitter (r = 0.25, p = 0.024) and abnormal pairs (r = 0.24, p = 0.03). After 28 months, MGII scores correlated with jitter (r = 0.31, p = 0.006), abnormal pairs (r = 0.29, p = 0.009), and pairs with blocks (r = 0.35, p = 0.001). Changes in MGII scores correlated with changes in jitter (r = 0.35, p = 0.002), abnormal pairs (r = 0.27, p = 0.014), and pairs with blocks (r = 0.36, p = 0.001).

Conclusions

Concentric needle jitter analysis may have the potential to evaluate baseline and sequential disease severity in MG.

Significance

This study highlights the potential for improved MG patient care through precise assessment and management using concentric needle jitter analysis to improve the accuracy of MG diagnosis and monitoring of disease activity.

Should We Consider Routine Blood Work for Diplopia and Ptosis in a Primary Care Setting?

Myasthenia gravis (MG) is a rare disorder that most commonly presents with ocular symptoms. Despite the highly sensitive blood work that can be used to diagnose the disease, it is frequently misdiagnosed until the disease becomes systemic. Literature, however, shows that those who begin treatment with acetylcholinesterase inhibitors before systemic presentation have a better prognosis. We discuss the case of a patient who presented to the clinic with a chief complaint of diplopia that was subsequently referred to ophthalmology. It was not until lab work was done by a subspecialist that the diagnosis of MG was made. The patient quickly responded to an acetylcholinesterase inhibitor and has since had a great prognosis. Here, we are advocating for the inclusion of routine lab work in the evaluation of patients who present to the primary care setting with diplopia in the absence of red flag symptoms. This approach aids in deciphering the potential involvement of MG in diplopia or ptosis. While such symptoms justify referral to ophthalmology, logistical challenges often hinder a prompt evaluation. Early diagnosis with the incorporation of routine lab work offers the potential to expedite the diagnosis of a rare disease. In doing so, providers can improve prognosis and potentially mitigate additive medical consultations.

Prognostic predictors of remission in ocular myasthenia gravis

BACKGROUND

Ocular myasthenia gravis (OMG) constitutes 15% of all myasthenia gravis patients.

METHODS

One hundred eight patients with OMG followed-up for over 36 months were retrospectively evaluated regarding factors associated with remission. Demographic features, neuro-ophthalmologic findings at onset, acetylcholine receptor (AChR Ab) and muscle-specifc tyrosine kinase antibodies (MuSK Ab), thymic status, single fiber electromyography (SFEMG) results were the variables considered.

RESULTS

Median age of disease onset was 57 years (range 18-82 years). Clinical features at onset was isolated ptosis in 55 (50.9%) and isolated diplopia in 33 (30.6%) patients. Combined ptosis and diplopia were present in 20 (18.5%) patients. Among 75 patients with ptosis, it was unilateral in 65 (86.7%) and bilateral in 10 (13.3%). AChR Abs were found in 66 (61.1%) and MuSK Abs in 2 (1.9%) patients. SFEMG abnormality was detected in 74 (68.5%) patients. Thymoma was present in 16 (14.8%) and thymic hyperplasia in 6 (5.6%) patients. Forty-one patients (37.9%) had been treated with pyridostigmine alone. Sixty-seven (62%) patients were given immunosupressive drugs. In 53 (49.1%) prednisone was used and in 14 (12.9%) patients it was combined with azathioprine. Thymectomy was performed in all 16 patients with thymoma. Complete stable remission (CSR) was achieved in 49 (45.4%) patients. Fifty-nine (54.6%) patients had reached minimal manifestation (MM) status; 32 (29.6%) having a status of MM-1 and 27 (25%) a status of MM-3.

CONCLUSIONS

The presence of AchR Abs (p = 0.034) and an abnormal SFEMG (p = 0.006) at onset as increased risk factors for the presence of ongoing signs necessitating medical treatment.

Immune checkpoint inhibitor-induced myocarditis, myositis, myasthenia gravis and transaminitis: a case series and review

Immune checkpoint inhibitors have been incorporated into the treatment of various malignancies. An increasing body of literature is reporting rare but potentially fatal adverse events associated with these agents. In this case series, the authors report the clinical features and outcomes of seven patients who received immune checkpoint inhibitors for different solid organ malignancies and developed a tetrad of immune-related myocarditis, myositis, myasthenia gravis and transaminitis. Herein the authors review the literature and describe the current diagnostic and management approach for this overlapping syndrome. The authors' series highlights the importance of a high index of clinical suspicion, prompt comprehensive investigations, early multidisciplinary team involvement and initiation of immunosuppressive therapy when immune-related adverse events are suspected.

Bedside and laboratory diagnostic testing in myasthenia

Myasthenia gravis (MG) and congenital myasthenic syndromes (CMS) are a group of disorders with a well characterised autoimmune or genetic and neurophysiological basis. We reviewed the literature from the last 20 years assessing the utility of various neurophysiological, immunological, provocative and genetic tests in MG and CMS. Diagnostic sensitivity of repetitive nerve stimulation test ranges between 14 and 94% and specificity between 73 and 100%; sensitivity of single-fibre EMG (SFEMG) test ranges between 64 and 100% and specificity between 22 and 100%; anti-acetylcholine receptor (AChR) antibody sensitivity ranges from 13 to 97% and specificity ranges from 95 to 100%. Overall, SFEMG has the highest sensitivity while positive anti-AChR antibodies have the highest specificity. Newer testing strategies that have been investigated over the last couple of decades include ocular vestibular-evoked myogenic potentials, otoacoustic emissions and disease-specific circulating miRNAs in serum for autoimmune myasthenia, as well as next-generation sequencing for genetic testing of CMS. While there has been significant progress in developing newer testing strategies for diagnosing MG and CMS over the last couple of decades, more research is needed to assess the utility of these newer tools regarding their sensitivity and specificity.

Can the Jankovic-assessment be used as an alternative to electromyography? A cross-sectional study on facial dystonia patients treated with Botulinum toxin

PURPOSE

This study aims to quantitatively compare the Jankovic assessment (JA) with electromyography (EMG)-based measures for assessing changes in facial movements in patients with facial dystonia.

MATERIALS AND METHODS

Thirteen patients (five males and eight females) affected with different forms of facial dystonia (hemifacial spasm and synkinesis) participated in this study. All patients were treated with Botulinum Toxin (BTX) and evaluated with the JA scale and EMG-based measures, including motor unit potentials (MUP) latency and presence of polyphasic potentials before and after BTX injection. Correlation between the JA scores and the EMG-based measures was calculated. Statistical analysis was performed with the Pearson test.

RESULTS

Correlation between the JA scores and the EMG-based measures was found to be statistically significant, both before and after treatment with BTX.

CONCLUSION AND RELEVANCE

JA scores significantly correlated with more objective EMG-based measures, suggesting that the JA scale can be used to assess facial movement changes, for example elicited by a treatment such as BTX injection. Thus, in facial dystonia patients, the JA scale may be used for evaluating treatment outcomes as a valid and low-cost alternative to EMG.

Myasthenia gravis: State of the art and new therapeutic strategies

Myasthenia Gravis (MG) - an autoimmune neuromuscular disease - is known by the production of autoantibodies against components of the neuromuscular junction mainly to the acetylcholine receptor, which cause the destruction and compromises the synaptic transmission. This disease is characterized by fluctuating and fatigable muscle weakness, becoming more intensive with activity, but with an improvement under resting. There are many therapeutic strategies used to alleviate MG symptoms, either by improving the transmission of the nerve impulse or by ameliorating autoimmune reactions with e.g. steroids, immunosuppressant drugs, or monoclonal antibodies (rituximab and eculizumab). Many breakthroughs in the discovery of new therapeutic targets have been reported, but MG remains to be a chronic disease where the symptoms are kept in the majority of patients. In this review, we discuss the different therapeutic strategies that have been used over the years to alleviate MG symptoms, as well as innovative therapeutic approaches currently under study.

Ocular myasthenia gravis: an update on diagnosis and treatment

PURPOSE OF REVIEW

Myasthenia gravis is an autoimmune disease that commonly affects the palpebral and extraocular muscles. Ocular myasthenia gravis (OMG) is a variant of the disease that is confined to the ocular muscles but frequently becomes generalized over time. The diagnosis of OMG is often challenging but both clinical and laboratory findings are helpful in confirming the clinical suspicion. This review provides an update on the diagnostic approach and therapeutic options for OMG.

RECENT FINDINGS

Antimuscle-specific tyrosine kinase and LDL-related receptor-related protein 4 are newly available serologic testing for myasthenia gravis that can help in increasing the diagnostic sensitivity of OMG. They should be included to the diagnostic algorithm of OMG in appropriate clinical situations.

SUMMARY

OMG remains a primarily clinical diagnosis, but recent advances in laboratory testing can improve the diagnostic accuracy and should be used in appropriate clinical settings. The mainstay of treatment for OMG has not significantly changed over the past years, but the increasing availability of steroid-sparing agents improved the disease control while minimizing steroid-induced complications.

What is in the Neuromuscular Junction Literature?

This update begins with myasthenia gravis and the roles of anti-agrin and cortactin antibodies. Regarding diagnosis, a report on repeated ice pack testing is highlighted as are several reports on the close correlation of electrodiagnostic testing with clinical features and the response to treatment. The incidence of head drop and associated clinical and ventilatory features are gleaned from a retrospective study. We also discuss a study that assessed the predominantly symmetric and conjugate ocular findings in MuSK-myasthenia gravis. Other topics that are covered include quality of life and preoperative risk. We then summarize the positive treatment trials of subcutaneous immunoglobulin and eculizumab. Turning to Lambert-Eaton Myasthenic Syndrome, we report on an epidemiologic study performed on the veteran affairs population, the results of the DAPPER study of 3, 4 diaminopyridine, and look to the future for other treatment options involving calcium gating modifiers.