**5. Treatment**

The treatment goal for patients with OM is to produce normal vision with a minimum of adverse effects. Unfortunately, treatment of OM has not been subject to rigorous evaluation and longitudinal studies of the risks of chronic treatment do not exist. Also, the individual tolerance of patients needs to be considered in making treatment recommendations. Some patients with OM respond well to non-pharmacologic therapies that are often overlooked by neurologists. If non- pharmacologic therapies cannot provide adequate relief, acetylcholesterase are typically administered, but the majority of patients do not respond well, and immunosuppressive treatments are required (Table).

sensitivity of repetitive nerve stimulation for OM is poor (11-54 percent), but specificity is high (89-98 percent) (Roh et al. 2011). Evaluation of the orbicularis oculi (especially the lower orbicularis oculi), orbicularis oris, or nasalis will increase the percentage of patients identified, but such evaluations are much more difficult to tolerate for patients than extremity evaluations (Mercelis and Merckaert 2011). Although identification of decremental responses in non-ocular muscles indicates subclinical disease in other muscles, the finding does not indicate the presence or predict progression to generalized

Single fiber electromyography (SFEMG) involves repetitive measures of the time between action potentials of two fibers in a muscle during a slight contraction. Abnormalities occur because of a fiber's slowed transmission of an action potential because of a compromised endplate potential that does not reach threshold. A fiber may not be activated which produces a neuromuscular block. If the mean jitter - time between activation of all fiber pairs (or endplates) - exceeds the upper limit of normal for that muscle, or if more than 10% of pairs have jitter that exceeds the upper limit of jitter during voluntary activation, then the study is considered abnormal. SFEMG is 62 to 99 percent sensitive for detection of MG, and its specificity is reported to be from 66 to 98 percent (Ukachoke et al. 1994; de Entrambasaguas et al. 2007; Mercelis and Merckaert 2011); however, it implementation is limited due to the requirements of specially-trained, experienced examiners. Although it is labor-intensive, SFEMG should be considered in patients with a strong clinical suspicion for OM in which repetitive nerve stimulation is negative, due to its higher sensitivity (Srivastava et al. 2007). The SFEMG is also useful in ruling out myasthenic weakness. If the SFEMG is normal in a clinically weak muscle, then the weakness is not due to a neuromuscular transmission disorder (Sanders and Stalberg 1996; Katirji and Kaminski

When the clinician thinks the OM diagnosis is likely additional testing is necessary. Thyroid dysfunction is a common co-morbidity and therefore, it is appropriate to screen all OM patients for hypo- or hyperthyroidism. Identification of concurrent thyroid dysfunction may improve MG related weakness. If clinically indicated the co-existence of other autoimmune disorders should be evaluated, in particular pernicious anemia, Chest imaging should be performed to exclude thymoma although thymoma is rare in OM patients. In anticipation of immunosuppressive treatments, screening for tuberculosis is

The treatment goal for patients with OM is to produce normal vision with a minimum of adverse effects. Unfortunately, treatment of OM has not been subject to rigorous evaluation and longitudinal studies of the risks of chronic treatment do not exist. Also, the individual tolerance of patients needs to be considered in making treatment recommendations. Some patients with OM respond well to non-pharmacologic therapies that are often overlooked by neurologists. If non- pharmacologic therapies cannot provide adequate relief, acetylcholesterase are typically administered, but the majority of patients do not respond

2002; Meriggioli and Sanders 2004; Sanders 2004).

well, and immunosuppressive treatments are required (Table).

**4.5 Other evaluations** 

appropriate.

**5. Treatment** 

MG.


\* From Epocrates® online Searched April 2011.

Table 1. Ocular Myasthenia Treatment Options
