Factors affecting outcome in ocular myasthenia gravis

ABSTRACT

Aim of the study: 50%–60% of patients with ocular myasthenia gravis (OMG) progress to generalized myasthenia gravis (GMG) within two years. The aim of our study was to explore factors affecting prognosis of OMG and to test the predictive role of several independent clinical variables.

Materials and methods: We reviewed a cohort of 168 Caucasian patients followed from September 2000 to January 2016. Several independent variables were considered as prognostic factors: gender, age of onset, results on electrophysiological tests, presence and level of antibodies against acetylcholine receptors (AChR Abs), treatments, thymic abnormalities. The primary outcome was the progression to GMG and/or the presence of bulbar symptoms. Secondary outcomes were either achievement of sustained minimal manifestation status or worsening in ocular quantitative MG subscore (O-QMGS) or worsening in total QMG score (T-QMGS), assessed by Myasthenia Gravis Foundation of America (MGFA) quantitative scores. Changes in mental and physical subscores of health-related quality of life (HRQoL) were assessed with SF-36 questionnaire. Variance analysis was used to interpret the differences between AChR Ab titers at different times of follow up among the generalized and non-generalized patients.

Results: Conversion to GMG occurred in 18.4% of patients; it was significantly associated with sex, later onset of disease and anti-AChR Ab positivity. Antibody titer above the mean value of 25.8 pmol/mL showed no significant effect on generalization. Sex and late onset of disease significantly affected T-QMGS worsening. None of the other independent variables significantly affected O-QMGS and HRQoL.

Conclusions: Sex, later onset and anti-AChR Ab positivity were significantly associated with clinical worsening.

KEYWORDS:

• Ocular myasthenia
• generalized myasthenia
• anti-acetylcholine receptor antibodies
• early-onset myasthenia
• late-onset myasthenia
• outcome measures

Acknowledgments

The authors thank Drs. Pietro Faglioni and Francesca Benuzzi for statistical advices.

Disclosure statement

The authors have no conflict of interest or sources of funding.

Additional information

Notes on contributors

Marco Mazzoli

Marco Mazzoli is a resident in Neurology at Department of Biomedical, Metabolic and Neural Sciences, University Hospital, Modena, Italy.

Alessandra Ariatti

Alessandra Ariatti is an attending neurologist at Department of Biomedical, Metabolic and Neural Sciences, University Hospital, Modena, Italy.

Franco Valzania

Franco Valzania is now head of Department of Neurology, S.Maria Nuova Hospital di Reggio Emilia, University Hospital, Modena, Italy.

Shaniko Kaleci

Shaniko Kaleci is a researcher at Department of Diagnostic Clinical Medicine and Public Health, University of Modena and Reggio Emilia, Modena, Italy.

Manuela Tondelli

Manuela Tondelli is researcher and neurologist at Department of Biomedical, Metabolic and Neural Sciences, University Hospital, Modena, Italy.

Paolo F. Nichelli

Paolo. F. Nichelli is Professor of Neurology and Head of Department of Biomedical, Metabolic and Neural Sciences, University Hospital, Modena, Italy.

Giuliana Galassi

Giuliana Galassi is a researcher, teacher in neurology, former attending neurologist at Department of Biomedical, Metabolic and Neural Sciences, University Hospital, Modena, Italy.