Characterization of patients with ocular myasthenia gravis - A case series

[Myasthenia gravis-Gender aspects and family planning]

BACKGROUND

There is evidence that gender-specific differences can influence the diagnostics, treatment and long-term disease course of myasthenia gravis (MG). In women the diagnosis is often made during childbearing age.

OBJECTIVE

Gender-specific differences in MG and relevant aspects in routine clinical practice are presented. In addition, current studies on family planning, pregnancy and childbirth in MG are highlighted and treatment recommendations are derived.

MATERIAL AND METHODS

Narrative literature review.

RESULTS

In addition to sociodemographic data, gender-specific differences encompass clinical as well as paraclinical factors, such as disease severity and antibody status. With few exceptions pregnancy is possible with good maternal and neonatal outcome. During pregnancy and peripartum, children of MG patients should be closely monitored for early detection and treatment of potential syndromes caused by diaplacental transfer of maternal antibodies.

CONCLUSION

Gender-specific factors can influence the course of MG. Adequate medical counselling and multidisciplinary collaboration are essential for MG patients who wish to have children.

The Role of Thymoma and Thymic Hyperplasia as Prognostic Risk Factors for Secondary Generalisation in Adults with Ocular Myasthenia Gravis: A Systematic Narrative Review

Purpose

The conversion of ocular myasthenia gravis (OMG) to generalised myasthenia gravis (GMG) is reported to differ depending on the presence of generalisation risk factors (Mazzoli et al. 2018). Thymic pathology has been recognised as a potential risk factor for generalisation in the literature (Teo et al. 2017). Thymoma and thymic hyperplasia have yet to be examined as a risk factor for generalisation of OMG independently of other risk factors in the literature. Thus, the purpose of this review is to examine the literature to identify whether thymoma and thymic hyperplasia do increase the risk of OMG progressing to GMG.

Methods

A literature search was carried out which employed a systematic approach. The search was undertaken using the following academic libraries: MEDLINE, Embase and Starplus. The search was limited to publications between the years 2001 to 2021. The search yielded 82 studies, which after the screening of titles and abstracts, left 62 studies for further analysis against the inclusion and exclusion criteria.

Results

The review found thymoma to be associated with an increased risk of GMG development. However, there was a scarce amount of literature which investigated thymic hyperplasia. Therefore, a firm conclusion could not be made with regards to thymic hyperplasia and the risk of GMG development.

Conclusions

This review provides evidence for the consideration of thymectomy early after thymomatous OMG diagnosis to prevent GMG conversion. As the review did not collect enough evidence to support the influence of thymic hyperplasia on OMG conversion, further research is required.

Low probability of myasthenia Gravis in patients presenting to neuro-ophthalmology clinic for evaluation of isolated ptosis

BACKGROUND

Concerning causes of ptosis, most notably third nerve palsy and Horner's syndrome, can be ruled out with normal ocular motility and pupillary examination. Myasthenia gravis (MG) however, rarely can present with ptosis as an isolated finding. We reviewed all patients presenting to tertiary neuro-ophthalmology practice with ptosis of unknown etiology to determine the frequency of MG.

METHODS

Retrospective chart review of patients referred to a tertiary neuro-ophthalmology practice with undifferentiated ptosis.

RESULTS

Sixty patients were included in the study. Twenty eight (47%) patients had ptosis along with various abnormalities of ocular motility and/or alignment and 32 (53%) had isolated unilateral ptosis defined as ptosis with absence of diplopia, or symptoms of generalized MG (GMG). Final diagnosis was aponeurotic ptosis due to levator palpebrae dehiscence in the majority (73%) of patients, while 10 (17%) were diagnosed with MG (6 with OMG, 4 with GMG). Diplopia was present in 9/10 patients with MG and 8/10 had abnormal ocular findings on clinical examination such as orbicularis oculi weakness, Cogan's lid twitch or fatiguability of ptosis on sustained upgaze. Only one patient referred for isolated unilateral ptosis was diagnosed with OMG and this patient had orbicularis oculi weakness.

CONCLUSIONS

None of the patients with isolated unilateral ptosis and otherwise normal examination had MG. All patients eventually diagnosed with MG had diplopia or orbicularis weakness on examination. Thus, the yield of investigating patients with isolated ptosis for MG is exceedingly low.

Paraneoplastic Syndromes in Neuro-Ophthalmology

Paraneoplastic neurological syndromes (PNS) occur in about 1 in 300 cases of cancer. The usual mechanism is that an antigen on the cancer sets off an immune response that then cross-reacts with a nervous system antigen. The presentation is usually with a subacute progressive neurological disorder. The management of these conditions is usually of both the underlying tumor and immunomodulation to suppress the autoimmune response. There are a number of these conditions that can present to the Neuro-Ophthalmology clinic, either as a discrete condition affecting vision or eye movements or as part of a more widespread neurological disorder. This article will discuss these conditions, their management and prognosis.

Clinical Utility of Striational Antibodies in Paraneoplastic and Myasthenia Gravis Paraneoplastic Panels

OBJECTIVE

To critically assess the clinical utility of striational antibodies (StrAbs) within paraneoplastic and myasthenia gravis (MG) serologic evaluations.

METHODS

All Mayo Clinic patients tested for StrAbs from January 1, 2012, to December 31, 2018, utilizing Mayo's Unified Data Platform (UDP) were reviewed for neurologic diagnosis and cancer.

RESULTS

A total of 38,502 unique paraneoplastic evaluations and 1,899 patients with MG were tested. In paraneoplastic evaluations, the StrAbs positivity rate was higher in cancer vs without cancer (5% [321/6,775] vs 4% [1,154/31,727]; p < 0.0001; odds ratio [OR] 1.35; confidence interval [CI] 1.19-1.53), but receiver operating characteristic (ROC) analysis indicated no diagnostic accuracy in cancer (area under the ROC curve [AUC] 0.505). No neurologic phenotype was significantly associated with StrAbs in the paraneoplastic group. Positivity was more common in all MG cancers compared to paraneoplastic cancers (p < 0.0001). In MG evaluations, the StrAbs positivity rate was higher in those with cancer vs without (46% [217/474] vs 26% [372/1,425]; p < 0.0001; OR 2.39, CI 1.9-2.96), with ROC analysis indicating poor diagnostic accuracy for thymic cancer (AUC 0.634, recommended cutoff = 1:60, sensitivity = 56%, specificity = 71%), with worse accuracy for extrathymic cancers (AUC 0.543). In paraneoplastic or MG evaluations, the value of antibody positivity did not improve cancer predictions. Paraneoplastic evaluated patients with positive StrAbs were more likely to obtain CT (p = 0.0001), with cancer found in 3% (12/468).

CONCLUSION

Despite a statistically significant association with cancer, an expansive review of performance in clinical service demonstrates that StrAbs are neither specific nor sensitive in predicting malignancy or neurologic phenotypes. CT imaging is overutilized with positive StrAbs results. Removal of StrAbs from paraneoplastic or MG evaluations will improve the diagnostic characteristics of the current MG test.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that the presence of StrAbs does not accurately identify patients with malignancy or neurologic phenotypes.

Acetylcholine receptor antibody positivity rate in ocular myasthenia gravis: a matter of age?

BACKGROUND

Anti-acetylcholine receptor antibodies (AChR Abs) are detected in 85% of myasthenia gravis (MG) patients, at higher rates in patients with late-onset disease. AChR Ab frequency is generally thought to be much lower in ocular MG (OMG), although recent studies reported positivity rates higher than 70%. We hypothesized that the improved AChR Ab diagnostic yield in OMG could be related to an increased frequency of late-onset disease, as observed in generalized MG.

METHODS

We compared OMG patients, with disease onset before or after 1998, for the age of onset, sex, presence of thymoma, immunosuppressive therapy rate, AChR Ab positivity, and follow-up duration. All patients had a follow-up ≥ 2 years. AChR Abs were tested by radioimmunoassay.

RESULTS

The study included 133 patients. Disease onset occurred before 1998 in 54/133 cases (41%). Age of onset, the proportion of late-onset patients, and AChR Ab positivity rate were significantly increased in the more recent population. Thymoma frequency was similar in the two series. On multivariate analysis, the only variable predicting AChR Ab positivity was the age at onset ≥ 50 years (OR = 6.50, 95% CI = 2.70-15.63, p < 0.0001).

CONCLUSIONS

Our results confirm that current AChR Ab positivity in OMG may be higher than generally thought. In our population, this finding was associated with an increased frequency of late-onset cases.

Controversies in Ocular Myasthenia Gravis

Myasthenia gravis (MG) with symptoms limited to eye muscles [ocular MG (OMG)] is a rare disease. OMG incidence varies according to ethnicity and age of onset. In recent years, both an increase in incidence rate, particularly in the elderly, and a lower risk for secondary generalization may have contributed to the growing disease prevalence in Western countries. OMG should be considered in patients with painless ptosis and extrinsic ophthalmoparesis. Though asymmetric muscle involvement and symptom fluctuations are typical, in some cases, OMG can mimic isolated cranial nerve paresis, internuclear ophthalmoplegia, and conjugate gaze palsy. Diagnostic confirmation can be challenging in patients negative for anti-acetylcholine receptor and anti-muscle-specific tyrosine kinase antibodies on standard radioimmunoassay. Early treatment is aimed at relieving symptoms and at preventing disease progression to generalized MG. Despite the absence of high-level evidence, there is general agreement on the efficacy of steroids at low to moderate dosage; immunosuppressants are considered when steroid high maintenance doses are required. The role of thymectomy in non-thymoma patients is controversial. Prolonged exposure to immunosuppressive therapy has a negative impact on the health-related quality of life in a proportion of these patients. OMG is currently excluded from most of the treatments recently developed in generalized MG.

Paraneoplastic Syndromes in Neuro-ophthalmology

PURPOSE OF REVIEW

This article discusses the varied types of paraneoplastic syndromes that commonly have neuro-ophthalmologic manifestations. Diagnostic considerations and therapeutic options for individual diseases are also discussed.

RECENT FINDINGS

Paraneoplastic syndromes can affect the afferent and efferent visual systems. Paraneoplastic syndromes may result in reduced visual acuity from retinal degeneration, alterations in melanocyte proliferation and uveal thickening, or acquired nystagmus. Ocular motor abnormalities related to paraneoplastic syndromes may present with symptoms from opsoclonus or from neuromuscular junction disease. Diagnosis remains challenging, but serologic identification of some specific antibodies may be helpful or confirmatory. Treatment, in addition to directed therapies against the underlying cancer, often requires systemic corticosteroids, plasma exchange, or immunosuppression, but some specific syndromes improve with use of targeted pharmacologic therapy.

SUMMARY

Diagnosis and therapy of paraneoplastic syndromes presenting with neuro-ophthalmic symptoms remain a challenge, but strategies are evolving and new approaches are on the horizon.