The use of steroids in the treatment of OMG remains controversial. While the effectiveness of steroids for preventing progression to generalized MG is unproven, there is no question that most patients with OMG do better symptomatically with prednisone than with pyridostigmine bromide. Corticosteroids achieve improvement of visual symptoms in 70–90% of patients. Outpatient oral therapy is usually employed, starting at low dose and slowly increasing. One suggested protocol consists of prednisone 10 mg every other day, increasing by 10 mg every four days to reach a maximum dose of 80 mg. The dose is then reduced by 10 mg every month down to 30 mg and then by 5 mg each month thereafter. Improvement usually occurs within two weeks of achieving the maximum dose. Long-term, low dose (5 to 10 mg), alternate day treatment is required to maintain remission in about one-third of patients. An alternative approach begins with daily dosing, starting at 10 mg and increasing every three doses to a maximum of 60 mg, then switching to an alternate day regimen once a response has been seen.

While the list of potential complications of steroid treatment is lengthy, the use of alternate day dosing, the relatively short duration of high-dose treatment, and the low dose needed to maintain remission in most patients usually prevent significant long-term adverse effects. The potential for an initial exacerbation of myasthenic weakness upon starting steroid treatment can be prevented by the slow initiation described above. Patients should be monitored for elevations of blood pressure and blood sugar, bone densitometry should be assessed at the onset of treatment, and treatment with a bone sparing agent may be initiated.

For patients who fail to improve with corticosteroids, develop significant steroid side-effects, or cannot reduce their steroid dose below a tolerable amount, other immunosuppressive therapy may be needed. Such modalities include azathioprine, ciclosporin, tacrolimus, mycophenolate mofetil, plasmapheresis and intravenous immunoglobulin (IVIg). Thymectomy has not been widely employed for the management of patients with

Chapter 12: Management misadventures 203

OMG in the absence of a thymoma. However, as the morbidity of the procedure decreases, particularly via the transcervical route, it is gaining greater acceptance for use in selected patients with OMG.

Until more definitive data are available, management of the patient with OMG must be individualized, specifically balancing the severity of symptoms, the patient’s visual requirements and the risk of developing complications of treatment.

Tip: Oral pyridostigmine bromide may improve ptosis, but resolution of diplopia is rarely achieved. Corticosteroids are the mainstay for treatment of ocular myasthenia gravis.

Failure to provide symptomatic treatment

Case: A 62-year-old woman experienced new onset of horizontal diplopia that progressed over one week and then remained stable for the next several months. Her neurologic history was significant for a 30-year history of relapsing remitting multiple sclerosis with secondary progression. She suffered poor balance, moderate spasticity and some loss of sensation in the lower extremities. Examination showed a 35 diopter esotropia with 15 degrees of abduction in the right eye and slowing of right lateral rectus saccades. Her MRI showed extensive white matter disease consistent with demyelinating disease (Figure 12.7). A course of IV methylprednisolone brought no improvement. Initially she wore a patch to prevent diplopia but eventually found that she could ignore one image with both eyes open, but was still troubled by visual confusion and lack of depth perception. Re-evaluation eight months later showed no change. Her deviation was still too large and too incomitant to treat with prisms and she was told that nothing could be done.

She sought a second opinion regarding treatment and, after an additional six month period of observation, was offered the option of strabismus surgery. The potential benefits and risks of surgery were fully discussed, including the possibility that her ocular alignment could change in the future due to progression of her demyelinating disease. She elected to

undergo extraocular muscle surgery consisting of a recession-resection procedure. Post-operatively her eyes were well aligned in primary position with good range of motion. She remains well four years later.

Discussion: Medical treatment has a range of components. Ideally, we address and correct the underlying disease process and reverse any deficits. In some cases, however, this is not possible and we settle instead for offering prognostic information and comfort. In the face of these limitations we may sometimes neglect forms of treatment that provide only symptomatic relief. In this section, we will address a few examples of such errors of omission.

The ultimate symptomatic treatment for diplopia is occluding one eye (either with a patch or an opaque contact lens) and many patients resort to this option. We can often do better, however. In some cases of ocular misalignment, prisms can restore binocular fusion. In other cases the deviation is too large or too incomitant to treat in this

way and extraocular muscle surgery is needed to reestablish single vision. Even in cases with severe loss of eye muscle function, surgery can often be surprisingly effective. An example of this is the use of full tendon transfer of vertical muscles to restore alignment and some abduction in patients with a complete sixth nerve palsy. Ideally, surgery is postponed until a deficit is stable. However, in some patients whose disorder is expected to be slowly progressive, it may nevertheless be appropriate to intervene surgically at a point when the degree of prism correction becomes cumbersome. The usual limit for ground-in prism is 10 diopters in each lens before spectacles become excessively thick and heavy. Paste-on prisms can be used at higher magnitudes but the resultant blur is often objectionable. Eye muscle surgery can “reset the clock”, correcting the motility deficit at least for some period of time. Any subsequent progression can be addressed again with increasing prisms. The above patient is an example of this clinical scenario.