Prediction of generalization of ocular myasthenia gravis under immunosuppressive therapy in Northwest China

Abstract

Background It is well demonstrated that immunosuppressants can reduce, but not eliminate the risk of generalized development in ocular myasthenia gravis (OMG). In this study, we aimed to explore the predictive factors of generalized conversion of OMG patients who received immunosuppressive treatments. Methods OMG patients under immunosuppressive treatments in Tangdu Hospital from June 2008 to June 2012 were retrospectively reviewed. Baseline clinical characteristics were documented. Patients were followed up regularly by face-to-face interview and the main outcome measure was generalized conversion. The logistic regression analysis was performed to determine the predictive factors of generalization of OMG. Results Two hundred twenty-three eligible OMG patients completed the final follow-up visit and 38 (17.0%) progressed to generalized MG (GMG) at a median time to generalization of 0.9 year. Patients with adult onset and positive repetitive nerve stimulation (RNS) of facial or axillary nerve had higher conversion rate than those with juvenile onset and negative RNS (p = 0.001; p = 0.019; p = 0.015, respectively). Adult-onset patients converted earlier than juvenile-onset OMG patients (p = 0.014). Upon multivariate logistic regression analysis, age of onset (Odds ratio [OR] 1.023, 95% confidence interval [CI] 1.006–1.041, p = 0.007) and positive facial nerve RNS (OR 2.826, 95%CI 1.045–5.460, p = 0.038) were found to be positively associated with generalized development. Moreover, an obviously negative association was found for disease duration (OR 0.603, 95%CI 0.365–0.850, p = 0.019). Conclusions Age of onset, disease duration and facial nerve RNS test can predict generalized conversion of OMG under immunosuppressive therapy. Adult-onset, shorter disease duration and facial nerve RNS-positive OMG patients have a higher risk of generalized development.

Initial Repetitive Nerve Stimulation Test Predicts Conversion of Ocular Myasthenia Gravis to Generalized Myasthenia Gravis

“…Several previous studies have found that decreased responses were more frequent in patients who experienced conversion to generalized MG than in those who remained ocular. 8 10 14 However, several points should be considered when interpreting these data, especially regarding the results of the RNS test. In one study, the results were not statistically significant after adjusting for other variables.…”

“… 10 A recent study that showed that a positive RNS test for the facial muscle was an independent predictor only analyzed subjects with ocular MG under immunosuppressive therapy. 14 In addition, the RNS test was conducted mainly on the facial nerve, and applied to the ulnar nerve in only 34% of the patients. Since the RNS test was not conducted in every patient in a consistent manner, the possibility of selection bias exists.…”

“…Some previous studies showed that the RNS test does not predict symptom conversion, 11 12 13 whereas others have suggested that the RNS test could predict the conversion to generalized MG. Hong et al 8 reported that an abnormal result on the RNS test is more frequently observed in patients who developed generalized MG than in those who remained as ocular MG. Other studies have also suggested that abnormal results on the RNS test could predict symptom conversion. 10 14 However, in those studies the RNS test was not applied to all subjects and the investigated muscles differed between patients. Therefore, there are some limitations in interpreting the effect of the RNS test in predicting conversion to generalized MG based on the current evidence.…”

Diagnosis of Myasthenia Gravis

“…Thus, it may be used to monitor treatment response. RNS abnormality in a peripheral muscle in ocular onset MG increases the risk of generalization, according to some authors [62,63]. In an emergency setting, RNS may distinguish a cholinergic crisis from a myasthenic crisis [48].…”

Pediatric Ocular Myasthenia Gravis: A Review

“…The factors which are proposed to be associated with generalization are older age at onset, RNS abnormalities in facial nerve, AChR antibody positivity, less use of early immunosuppressive therapy, presence of thymoma, and shorter disease duration. [97][98][99][100] However, these studies were retrospective and the patients were treated with immunosuppressive agents, which might have confounded the association results due to their disease modifying effects. 74 Though a study to evaluate the risk factors in nonimmunosuppressed patients is required; it might not be ethically justified.…”