The effect of prednisone on the progression from ocular to generalized myasthenia gravis
Introduction
Approximately 50% of all acquired myasthenia gravis patients present with ocular symptoms of ptosis and/or diplopia with no clinical evidence of bulbar, respiratory, or limb muscle weakness [1], [2], [3], [4], [5], [6]. Of those patients with ocular myasthenia gravis (OMG), about 50–60% will subsequently develop generalized myasthenia gravis (GMG), with 80% progressing within the first year and 90% within 3 years [1], [5], [6], [7]. About 10% will have episodes of spontaneous remission and be symptom-free [1], [5]. Serum acetylcholine receptor antibodies (positive in about 35–50% in OMG), abnormal results on repetitive nerve stimulation, single-fiber electromyography, or abnormal curare sensitivity is not predictive of those patients who are more likely to develop generalized myasthenia gravis [1], [4], [8], [9], [10], [11].
There have been reports of a lower rate of OMG progressing to GMG in patients who received immunomodulating therapy [8], [12]. Oosterhuis [9] noted complete remission in 6 of 12 patients with OMG after starting oral steroids but made no further analysis or comment. Grob et al. [5] reported a higher incidence of remission and improvement in his 202 patients with ocular myasthenia gravis treated with oral steroids between the years of 1966 and 1985. Kupersmith et al. [12] found that prednisone was associated with a reduced frequency of patients with OMG progressing to GMG. Although there were no internal controls, these results were better than the generally accepted 50–60% of OMG progressing to GMG found in the literature [1], [5], [6]. Kupersmith et al. [13], in a subsequent study, showed that the rate of development of GMG was reduced from 36% in the group not treated with prednisone to 7% in the group treated with prednisone.
We retrospectively evaluated a group of patients with ocular myasthenia to determine if those that were treated early with prednisone had a lower proportion that progressed to generalized myasthenia gravis compared to those that were treated only with acetylcholinesterase inhibitors.
Section snippets
Methods
Patients with a diagnosis of ocular myasthenia gravis were selected from databases of the Yale Neuromuscular and Ophthalmology services. The diagnosis of OMG was determined primarily on clinical evaluation and confirmatory diagnostic tests that included one or more of the following: electromyography, antiacetylcholine receptor antibody titers, edrophonium test, and ice and sleep test. The minimum duration of follow-up was 24 months. An experienced neurologist diagnosed all GMG patients. All OMG
Results
One hundred thirty-six charts of patients diagnosed with myasthenia gravis were identified from the database. Fifty-six patients met the inclusion criteria. The mean age of the entire patient population included in the study was 53 years. The mean age of all patients in the PT group was 55.4 years (n=27), and 50.9 years in the NPT group (n=29). The mean age of patients in the PT group who remained at OMG was 54.6 years and those that progressed to GMG was 62 years. The mean age of patients in
Discussion
This study was done to see if oral prednisone affects the progression of OMG to generalized myasthenia gravis. Two years from the onset of OMG, we found a statistically significant difference in the progression from OMG to GMG between the treated and untreated patients.
Our study specifically looked at initiating steroids within a time frame that has the potential to alter the natural history of ocular myasthenia gravis progressing to generalized myasthenia gravis. In interpreting the
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