Ocular myasthenia gravis: a review and practical guide for clinicians

Seronegative Myasthenia Gravis: A Rare Disease Triggered by SARS-CoV-2 or a Coincidence?

Myasthenia gravis (MG) results from the production of autoantibodies against the neuromuscular junction, leading to muscle weakness. Although the exact cause is not fully understood, it is known that the onset and exacerbations of MG can occur after viral infections. We present the case of a patient with no prior history of MG with new-onset proximal muscle weakness and ptosis, following SARS-CoV-2 infection, This case underscores the potential for autoimmune diseases to be triggered by SARS-CoV-2.

Cavernous Sinus MRI Findings in Inflammatory and Ischemic Oculomotor Cranial Nerve Palsies

BACKGROUND

The significance of asymmetric enhancement on cavernous sinus MRIs in the differential diagnosis of ischemic and inflammatory oculomotor cranial nerve (OCN) palsies remains controversial. This study explored the cavernous sinus MRI findings for cavernous sinus idiopathic inflammation (inflammation group), microvascular ischemic OCN palsy (ischemic group), and ocular myasthenia gravis (OMG group) patients.

METHODS

A total of 66, 117, and 60 patients were included in the inflammation, ischemic, and OMG groups, respectively. Cavernous sinus MRIs were retrospectively analyzed.

RESULTS

The abnormality rates of cavernous sinus MRIs for OMG and ischemic groups were 41.7% (25/60) and 61.5% (72/117), respectively. Inconsistency rates between clinical topical diagnosis and imaging findings for inflammation and ischemic groups were 3.0% (2/66) and 13.7% (16/117), respectively ( P = 0.020). In the inflammation group, cavernous sinus thickness, thickening enhancement, and enhancing adjacent lesions were noted in 90.9% (60/66), 71.2% (47/66), and 25.8% (17/66) of the patients, whereas in the ischemic group, they were noted in 51.3% (60/117), 38.5% (45/117), and 0.9% (3/117) of the patients, respectively ( P < 0.001). Among ischemic CN III palsy patients, 55.5% (15/27) and 16.7% (2/12) of the cases had CN III enlargement and enhancement in the diabetic and nondiabetic groups, respectively ( P = 0.037).

CONCLUSIONS

Cavernous sinus MRI abnormalities can be explained by specific pathologic mechanisms of the primary disease based on the complex neuroanatomy. However, suspicious inflammatory changes cannot exclude the possibility of ischemia and over reliance on these findings should be avoided.

Advances in Understanding and Managing Myasthenia Gravis: Current Trends and Future Directions

Myasthenia gravis (MG) is an autoimmune illness characterized by autoantibodies against the acetylcholine receptor (AChR), muscle-specific tyrosine kinase (MuSK), and an increasing number of extra postsynaptic proteins. Pathogenic autoantibodies reduce the number of functional AChRs in the neuromuscular junction's (NMJ) muscle end plate. The cause of the autoimmune response is unknown, but thymic abnormalities and immune regulatory deficiencies are significant. The disease's incidence is likely influenced by genetic predisposition, with sex hormones and exercise playing a role. MG can affect any age, race, or gender and can be caused by any stressor, with infections being the most frequent cause. Treatment focuses on airway support and the triggering incident. MG is a rare autoimmune disease causing fatigue-inducing weakness in the axial, respiratory, leg, and bulbar muscles. Initially affecting the eyes, most MG patients experience at least one worsening symptom during their illness. The disease is mainly caused by antibodies against the AChR, dependence on the immune system within cells, and engagement of the complement system. The complement system plays a significant role in MG, and complement inhibition can both prevent the onset and slow its development. Ocular MG affects around 15% of people, with most patients having blocking antibodies against the cholinergic receptor. There may be correlations between thymoma and other autoimmune conditions, especially thyroid illness. Treatment and management for MG involve removing autoantibodies from circulation or blocking effector mechanisms using techniques such as complement inhibition, plasmapheresis, and B-cell elimination.

A controlled clinical study on efficacy and safety of periocular triamcinolone acetonide injection for treating ocular myasthenia gravis

OBJECTIVE

To evaluate the efficacy and safety of peribulbar triamcinolone acetonide injection for treating ocular myasthenia gravis (OMG), with a comparison of traditional oral drug therapy.

METHODS

A total of 22 patients with OMG who received periocular triamcinolone acetonide injection (initially 20 mg weekly, then once per month later if symptoms were improved) from July 2019 to July 2022 were evaluated by a comparison of symptom degree before and after treatment. Adverse reactions were also monitored during the period of treatment. The period of follow-up was more than 6 months. Additionally, a comparison of the treatment efficacy between this periocular injection and traditional oral administration was performed in OMG patients.

RESULTS

After 4 weeks of treatment, the degree of ptosis in OMG patients decreased to -3.00 ± 0.69, compared to the value (-0.86 ± 1.32) before treatment. The degree of ophthalmoplegia also decreased from 3.12 ± 0.72 to 0.86 ± 0.88 (P < 0.001) after treatment. The achievement rates of minimal manifestations status (MMS)for ptosis and ophthalmoplegia after 4 week-treatment were 86.3% and 75%, respectively, while they were 50% and 30% in patients with traditional oral administration. There was statistically significant difference only in MMS (rather than symptom relief rate and generalization conversion rate) between two groups. No serious complications (except for intraorbital hematoma) were found in OMG patients during the treatment period.

CONCLUSION

Repeated peribulbar injection of triamcinolone acetonide can effectively alleviate the initial symptoms of OMG patients. However, the evaluation of its long-term efficacy is still needed.

CLINICAL TRIAL REGISTRY

This study has been clinically registered by Chinese Clinical Trial Registry (ChiCTR), first trial registration date:05/07/2019, registration number: ChiCTR1900024285.

A case report of dermatomyositis mimicking myasthenia gravis

RATIONALE

Patients who have myasthenia gravis or dermatomyositis show clinical signs of muscular weakening. Ocular muscle involvement is uncommon, and symmetrical proximal limb weakness is the typical presentation of dermatomyositis. However, the earliest and most noticeable sign in those with myasthenia gravis is extraocular muscular paralysis. Dermatomyositis is frequently complicated by malignancy, and the common malignancies associated with dermatomyositis vary by region and ethnicity, while thymoma is relatively rare. About 10% to 15% of people with myasthenia gravis have thymoma, which is involved in the etiology of the disease.

PATIENT CONCERNS

A 68-year-old female presented with ocular muscle weakness for 10 days that manifested as bilateral blepharoptosis with the phenomenon of "light in the morning and heavy in the evening." Imaging examination showed anterior mediastinal thymic tumor with metastasis.

DIAGNOSES

After a thorough physical examination, we discovered bilateral upper limbs with grade IV muscle strength and the typical rash of dermatomyositis. In combination with elevated serum kinase levels and electromyography suggesting myogenic damage, the patient was finally diagnosed as dermatomyositis with multiple metastases of thymoma.

INTERVENTIONS

The patient received oral hydroxychloroquine sulfate, topical corticosteroids, and tacrolimus ointment, but these did not work very well. Subsequently, the patient underwent surgery combined with radiotherapy for the thymoma.

OUTCOMES

Muscle weakness in the patient improved after effective treatment of tumor, and the rash mostly disappeared.

CONCLUSION

Ocular muscle weakness and thymoma are more common in myasthenia gravis, but we cannot ignore the possibility of dermatomyositis. To further establish the diagnosis, a thorough physical examination and laboratory findings are required. Further tumor screening should be performed for patients with dermatomyositis. Early detection and management of possible tumors are essential to the treatment of dermatomyositis linked to malignancies.

Diagnosis and therapy of myasthenia gravis-the patients' perspective: a cross-sectional study

The survey aimed to explore patients' perspectives with myasthenia gravis (MG) toward the diagnosis made and the therapy used to treat MG. The survey was conducted with a quantitative method, using the CAWI technique. A total of 321 people participated in the survey. More than half of the respondents (56.4%) had suffered from MG for less than 10 years. In three out of 10 cases (30.9%), the diagnosis of MG lasted 3 years or longer. The diagnostic delay was significantly longer in female respondents than in the males (p = 0.029). Cholinergic drugs were used in 92.9% of cases initially, and as maintenance therapy in 84.3% of cases. Corticosteroids were used in initiating therapy (45.8%) and as maintenance therapy (46.4%). One in four respondents (25.5%) reported experiencing very strong and strong side effects after using steroids. The side effects from steroid therapy very strong or strong affected overall physical health in 55.9% of respondents, very strong or strong affected self-acceptance in 52%, to a very large or large extent on mental health in 47.1%, and to a very strong or strong extent influenced the performance of daily activities in 28.2%. More than half of the respondents (57.0%) had had a thymectomy. Seven out of 10 respondents (72.0%) declared that the therapy they were on at the time of the survey allowed them (to varying degrees) to control their course of MG. Low therapy acceptance and less well controlled MG was associated with a preference for non-tablet therapies (p = 0.045). Regular follow-up and cooperation with the specialist health care system should improve MG symptoms, activities of daily living, and quality of life.

[Ocular myasthenia gravis]

The article describes an urgent medical and social problem - the diagnosis and treatment of the ocular myasthenia gravis. Despite recent advances in the study of synaptic pathology, the diagnosis of the ocular form of myasthenia gravis remains a challenging problem. This is due to the poor information content of laboratory and electromyographic methods in the diagnosis of ocular myasthenia gravis, and the generalized myasthenia gravis manifests in 90% of cases by external ophthalmoplegia and ptosis. The article highlights the features of the diagnosis and differential diagnosis of ocular myasthenia gravis. Data on the course and features of the clinical presentation of the disease are presented. The importance of analyzing anamnestic data and clinical manifestations of the disease is emphasized. The article discusses modern approaches to the treatment of the ocular myasthenia gravis. The authors present clinical observations of 2 patients with ocular myasthenia gravis.

Ocular myasthenia gravis saccades as a measure of extraocular muscle function

Background

It is important to understand the pathophysiology of ocular myasthenia gravis (OMG) to improve treatment.

Aim

To use modern video-oculography to characterise saccadic eye movements in patients with OMG, including anti-AChR, anti-MuSK, anti-LRP4, and seronegative OMG.

Methods

In total, 21 patients with OMG and five age-matched healthy control subjects underwent video-oculography. Participants performed a sequence of horizontal saccades (3 minutes each) at ±5°, ± 10°, and ±20°, followed by 3 minutes of saccades directed at randomly presented targets at ±5°, ± 10°, and ±15°. We recorded the direction, amplitude, duration, peak, and average velocity of each saccade for each task for each participant.

Results

Saccadic amplitude, duration, and average velocity were all lower in OMG patients than in control subjects (p < 0.021). Saccadic amplitude and velocity decreased over time, but this decrease was similar in OMG patients and control subjects. Fixation drift and ocular disparity tended to be greater in OMG patients than in control subjects. Saccadic intrusions occurred more frequently in OMG patients than in control subjects (p < 0.001). No significant effects of time or group by time on fixation drift or ocular disparity were found.

Discussion

Saccadic velocities in OMG patients differed from those in normal control subjects, which suggests that OMG affects fast-twitch fibres, although fast-twitch fibres were still able to generate "twitch" or "quiver" movements in the presence of even severe ophthalmoplegia. Slow-twitch muscle fibres involved in gaze holding were also affected, accounting for increased fixation drift following saccades. Our objective finding of increased fixation drift and a larger number of saccadic intrusions mirror our anecdotal experience of patients with OMG who report significant diplopia despite minimal ophthalmoplegia on examination. Such microsaccades may be a surrogate for compensation of a gaze-holding deficit in MG.