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From the Department of Neurology, Emory University School of Medicine (M.B.), and Department of Neurology, Case Western Reserve University, Louis Stokes Cleveland VA Medical Center (H.J.K.), Cleveland, OH.
Address correspondence and reprint requests to the American Academy of Neurology, 1080 Montreal Ave., St. Paul, MN 55116 guidelines{at}aan.com
| Abstract. |
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Methods: Medline, EMBASE, and the Cochrane Neuromuscular Disease Group Register were searched for articles of possible relevance to the medical treatment of ocular myasthenia. The titles and abstracts of all articles, as well as the full texts of all potentially relevant manuscripts, were read by both reviewers. Experts in the field were also contacted to identify other published or unpublished literature. All articles were evaluated using predefined criteria to evaluate their methodologic quality. Data from these articles were extracted to address two questions: 1) Are there any effective treatments for symptoms of ocular myasthenia? 2) Are there any treatments that reduce the risk of progression from ocular to generalized myasthenia gravis (MG)?
Results: A single randomized controlled trial compared the efficacy of intranasal neostigmine to placebo for the treatment of ocular symptoms. Methodologic limitations of this study preclude any firm conclusions. A second randomized controlled trial compared the efficacy of corticotropin with placebo, but outcome was reported in terms of a quantification of the range of eye movements. For this reason, the results of the second study could not be used to address the issues of improvement in ocular symptoms or the risk of progression to generalized MG. This review did not identify any randomized controlled trials addressing the risk of progression to generalized MG but did identify five observational studies reporting the effects of corticosteroids on progression to generalized MG, two of which also reported the effects of azathioprine.
Recommendations: The absence of high-quality evidence means that it is not possible to make any evidence-based recommendations regarding the effects of cholinesterase inhibitors, corticosteroids, or other immunosuppressive agents with respect to improvement of ocular symptoms. There is similarly an absence of evidence regarding the effects of cholinesterase inhibitors on the risk of progression to generalized myasthenia gravis (MG). Based on data from several observational studies, corticosteroids and azathioprine are of uncertain benefit in terms of their effect on the risk of progression to generalized MG.
| INTRODUCTION |
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The treatment of ocular myasthenia, with the goals of alleviating symptoms and preventing progression to generalized MG, is a subject of debate.911 Options for treatment include cholinesterase inhibitors, blepharoplasty, and lid crutches for relief of symptoms as well as immunosuppressive therapy with corticosteroids and/or a range of corticosteroid-sparing immunosuppressive agents to prevent progression to generalized MG. Opponents of immunosuppressive therapy argue that ocular myasthenia is not life-threatening and, therefore, that symptoms may not justify the potential for significant adverse effects associated with immunosuppressive drugs, that symptoms may be alleviated via other means such as a lid crutches or eye patching, and that there is little evidence to support the use of immunosuppressive therapy either in terms of permanent relief of ocular symptoms or with regard to the risk of progression to generalized disease.9 The proponents of immunosuppressive therapy, on the other hand, argue that the symptoms of ocular myasthenia (diplopia and ptosis) may impair vision sufficiently to interfere with work and quality of life and that such treatment often eliminates symptoms. Further, the initial presentation with ocular myasthenia affords the opportunity to intervene therapeutically to reduce the likelihood of progression to generalized MG.10
Clinical questions. Because the primary goals of treatment for ocular myasthenia are 1) to alleviate the symptoms of ocular myasthenia and 2) to prevent or limit the severity of the generalization of the disease, this review was performed to address these two specific questions:
The question of the role of thymectomy in the treatment of ocular myasthenia was not addressed by this review given that the general issue of the benefits of thymectomy in MG has been the subject of a previous practice parameter.12
Description of the analytical process. Panel selection and literature review process. Two neurologists with experience in the evaluation and treatment of patients with MG were appointed by the American Academy of Neurology Quality Standards Subcommittee to prepare this review. The Cochrane Neuromuscular Disease Group Register was searched for randomized controlled trials; Medline (1966 to 2004) and EMBASE (1980 to 2004) were also searched for randomized controlled trials, casecontrol studies, and cohort studies. Search terms included myasthenia gravis, eye, ocular, and vision, as well as a series of terms describing specific therapies and specific types of clinical studies. To be included in the review, studies had to meet three criteria: 1) randomized (or quasi-randomized) controlled trial or observational (cohort or casecontrol) study design; 2) active treatment compared with placebo, no treatment, or some other treatment; and 3) results reported separately for patients with ocular myasthenia (Grade 1) as defined by the Myasthenia Gravis Foundation of America.13 Studies reporting outcome in children and adults were considered.
The quality of randomized controlled trials was evaluated in six domainsmethod of randomization, allocation concealment, patient blinding, observer blinding, explicit inclusion/exclusion criteria, and completeness of follow-upusing a set of predefined criteria. The quality of observational studies was similarly evaluated in three domainscontrol for confounding, completeness of follow-up, and observer blindingusing predefined criteria. The method of randomization was graded as adequate (computer-generated random numbers, tables of random numbers, coin toss), unclear (statement made that trial is randomized but method not described), or inadequate (quasi-randomized). Allocation concealment was graded as adequate (identical prenumbered containers prepared by an independent pharmacy of central randomization unit or sequentially numbered opaque sealed envelopes), unclear (no details given of how the next assignment in the sequence was concealed), inadequate (open allocation schedule, unsealed or nonopaque envelopes, alternation, days of week, etc.), or not done. Patient and observer blinding were graded as adequate (method of blinding described and thought to be sufficient to ensure that the investigator was unaware of the treatment received at the time outcome evaluation was performed), unclear (authors state that study was blinded, but details not provided), inadequate (some method used to blind investigators, but technique was unreliable), or not done. Completeness of follow-up was graded as adequate (analysis performed with >80% of patients), unclear (insufficient details provided on withdrawals, dropouts, etc.), inadequate (<80% of patients included in the analysis), or not done. Finally, control for confounding was graded as adequate (multivariate analysis that included at least two factorsage, duration of ocular symptoms before initiation period of follow-up, concomitant immunosuppressive therapy, duration of follow-up after entry into the study, antibody status, presence of abnormalities on repetitive nerve stimulation or single fiber electromyographyor data presented showing that the treatment groups were comparable at baseline with respect to this same set of factors), unclear (authors state that they controlled for confounding, but details not given), inadequate (some effort made to control for confounding, but insufficient number of relevant factors were considered in the analysis), or not done.
| ANALYSIS OF EVIDENCE |
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The second study included only three patients with ocular myasthenia (and seven patients with generalized myasthenia) who were randomly assigned to receive a 2-week course of either intranasal neostigmine or placebo in a crossover study design without a washout period (Class III).15 No primary outcome measure was specified, but the authors reported that ptosis was improved in one of the patients during treatment with neostigmine. The review did not identify any observational studies that reported outcome in terms of improvement in ocular symptoms.
Conclusions. There is only a single randomized controlled trial that has examined the question of whether pharmacotherapy improves symptoms in ocular myasthenia. This study compared the efficacy of intranasal neostigmine to placebo (Class III).15 No firm conclusions can be drawn from this study given the extremely small sample size (n = 3) and other methodologic limitations of the study. There are no studies that examined the efficacy of pyridostigmine (Mestinon), corticosteroids, or other immunosuppressive agents in improving the symptoms of ocular myasthenia.
Recommendations. Given the absence of evidence, it is not possible to make any evidence-based recommendations regarding the effects of cholinesterase inhibitors, corticosteroids, or other immunosuppressive agents in improving the symptoms of ocular myasthenia.
Are cholinesterase inhibitors, corticosteroids, or other immunosuppressive agents effective in reducing the risk of progression from ocular to generalized MG? Evidence. Neither of the two randomized controlled trials identified by this review reported outcome in terms of the risk of progression to generalized MG. The review did identify five observational studies that reported the impact of corticosteroids on the risk of progression from ocular to generalized MG,1620 two of which also examined the effect of azathioprine on the risk of developing generalized MG.17,20 The methodologic quality of these studies (table 2) was fairly uniform with adequate follow-up in most, and adequate control for confounding but lack of independent assessment of outcome (Class IV). The point estimates of the risk ratios and odds ratios in the studies that examined the effects of oral corticosteroids showed a benefit in terms of reducing the risk of progression to generalized MG in three studies17,18,20 (Class IV), with the confidence interval (CI) spanning unity in two studies,16,19 only one of which did not show a benefit (Class IV)16 (table 2). The two studies that examined the effects of azathioprine similarly showed a beneficial effect on the risk of progression to generalized MG with CIs that did not span unity (Class IV)17,20 (table 2).
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Conclusions. There are no randomized controlled trials that have examined the efficacy of cholinesterase inhibitors, corticosteroids, or other immunosuppressive agents in reducing the risk of progression to generalized MG. The available studies that have examined this question are all observational and of limited quality (Class IV). Three of the five observational studies that examined the efficacy of corticosteroids and both observational studies that examined the efficacy of azathioprine suggest that these agents may be effective in reducing the risk of progression from ocular to generalized MG (Class IV).
Recommendations. For patients with ocular myasthenia, the evidence does not support or refute the use of corticosteroids and/or azathioprine to reduce the risk of progression to generalized MG (Level U). The decision to use such agents should be weighed against the potential for harmful side effects of these medications. Furthermore, it is not possible to make any evidence-based recommendations with regard to the question of whether cholinesterase inhibitors have any effect in reducing the risk of progression to generalized MG. Recommendations cannot be made because of an absence of evidence.
| RECOMMENDATIONS FOR FUTURE RESEARCH |
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In the absence of randomized controlled trials, well-designed observational studies may shed light on the efficacy of cholinesterase inhibitors, corticosteroids, and other immunosuppressive agents. These studies should adequately control for potentially confounding factors (age, the use of concomitant therapy, the duration of ocular symptoms before entry into the study, the duration of follow-up following entry into the study, antibody status, and the presence of systemic abnormalities of repetitive nerve stimulation or single fiber electromyography), should assess adverse effects, and should ensure that the outcome measure is ascertained in a blinded fashion to minimize bias.
| ACKNOWLEDGMENT |
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| MISSION STATEMENT OF QSS |
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| DISCLAIMER |
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| CONFLICT OF INTEREST STATEMENT |
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| APPENDIX 1 |
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| APPENDIX 2 |
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Class I:
Prospective, randomized, controlled clinical trial with masked outcome assessment, in a representative population. The following are required:
a) primary outcome(s) clearly defined; b) exclusion/inclusion criteria clearly defined; c) adequate accounting for drop-outs and cross-overs with numbers sufficiently low to have minimal potential for bias; d) relevant baseline characteristics are presented and substantially equivalent among treatment groups or there is appropriate statistical adjustment for differences.
Class II:
Prospective matched group cohort study in a representative population with masked outcome assessment that meets ad above OR a RCT in a representative population that lacks one criteria ad.
Class III:
All other controlled trials (including well-defined natural history controls or patients serving as own controls) in a representative population, where outcome is independently assessed, or independently derived by objective outcome measurement.*
Class IV:
Evidence from uncontrolled studies, case series, case reports, or expert opinion.
| APPENDIX 3 |
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A = Established as effective, ineffective, or harmful for the given condition in the specified population. (Level A rating requires at least two consistent Class I studies.)
B = Probably effective, ineffective, or harmful for the given condition in the specified population. (Level B rating requires at least one Class I study or at least two consistent Class II studies.)
C = Possibly effective, ineffective, or harmful for the given condition in the specified population. (Level C rating requires at least one Class II study or two consistent Class III studies.)
U = Data inadequate or conflicting; given current knowledge, treatment is unproven.
*Objective outcome measurement: an outcome measure that is unlikely to be affected by an observers (patient, treating physician, investigator) expectation or bias (e.g., blood tests, administrative outcome data). ![]()
Supplemental data at www.neurology.org
This article was previously published in electronic format as an Expedited E-Pub on April 25, 2007, at www.neurology.org.
Approved by the Quality Standards Subcommittee on July 29, 2006; by the Practice Committee on March 15, 2007; and by the AAN Board of Directors on April 5, 2007.
Disclosure: The authors report no conflicts of interest.
Received December 27, 2006. Accepted in final form March 2, 2007.
| REFERENCES |
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