eMedicine Specialties > Ophthalmology > Ophthalmology for the General Practitioner

Myasthenia Gravis: Treatment & Medication

Author: Shady Awwad, MD, Staff Physician, Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas
Coauthor(s): Riad Ma'luf, MD, Head, Division of Oculoplastics, Department of Ophthalmology, Clinical Assistant Professor, American University of Beirut Medical Center; Nicolas Hamush, MD, Consulting Staff, Department of Ophthalmology, Eye & Ear Hospital International, Naccache, Lebanon
Contributor Information and Disclosures

Updated: Jul 13, 2007

Treatment

Medical Care

A wide armamentarium of medical therapy exists for patients with MG. No general consensus exists about which to start first or which to combine. Medical treatment is administered best by a neurologist. The role of the ophthalmologist is to follow up on the ophthalmic symptoms, notably diplopia and ptosis.

• Ptosis, when it becomes bothersome, is treated best by lid crutches, since surgery is contraindicated because of the fluctuation of the disease, producing lagophthalmus with all of its complications. Diplopia is eliminated by Fresnel prisms unless the deviation is large and variable, in which case an opaque lens in front of the involved eye is preferred.
• The neurologist orchestrates the pharmacologic treatment. This includes anticholinesterase medication and immunosuppressive agents, such as corticosteroids, azathioprine, cyclosporine, plasmapheresis, and intravenous immune globulin (IV Ig).
• No evidence-based studies fully prove the usefulness of cholinesterase inhibitors, corticosteroids, and other immunosuppressive agents in improving ocular symptoms. In addition, the effect of corticosteroids and azathioprine on the progression to generalized MG is still uncertain.
• Plasmapheresis (as well as IV Ig) is reserved for myasthenic crisis and refractory cases. It removes anti-AChR antibodies from the circulation. Improvement is noted in a couple of days, but it does not last for more than 2 months.

Surgical Care

• Thymectomy
  
  
  • In the absence of a thymoma, 85% of patients experience improvement and 35% of these patients achieve drug-free remission.
  • In one study by Nieto and coworkers, the rate of remission in the presence of thymic hyperplasia was 42% compared to 18% in patients with thymoma.¹¹
  • In ocular MG, thymectomy should be delayed at least 2 years to allow for spontaneous remission or for generalized MG to develop.
  • Whether thymectomy is to be performed for prepubescent patients or patients older than 55 years is still controversial. Recent reports encourage surgery for the latter group.
  • Patients often experience some transient worsening of symptoms early in the postoperative period.
  • Improvement usually is delayed for months or years.
  • Complete removal of thymic tissue is of utmost importance because any small remnant might lead to recurrence.
• Strabismus surgery: Muscle surgery for selected patients with a stable course of MG and persistent diplopia has been reported with success.^12,13
• Blepharoptosis surgery: Ptosis surgery for patients with a stable ptosis, which has failed to respond to medical therapy for MG, has recently gained popularity. The surgical technique can include external levator advancement, frontalis suspension sling, or tarsomyectomy.^14,15

Consultations

• Consult neurologists after diagnosing patients with ocular MG. Treatment is initiated best by them rather than the ophthalmologist.
• Consult cardiothoracic surgeons whenever thymectomy is contemplated as part of the treatment.

Diet

• Solid diet might be difficult for some patients to chew in acute oropharyngeal exacerbations.
• Aspiration might occur too, so clear fluids are to be avoided and are supplanted best by full fluids when dysphagia is present.
  

Medication

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Anticholinesterase inhibitors

Increase the availability of ACh in the neuromuscular junction. They continue to be used as the first line of treatment of MG. The improvement is usually partial and frequently decreases after many weeks to months of treatment. Besides, they are not as beneficial for ocular MG as for the generalized form of the disease. Hence, they often are complemented (and sometimes substituted) with immunosuppressive therapy.

Pyridostigmine bromide (Mestinon)

Intermediate-acting agent. Clinical effect begins in 30-60 min, peaks after 2 h, and lasts up to 6 h.

Neostigmine bromide (Prostigmine)

Comes second in preference to pyridostigmine bromide. Has a poor absorption when taken PO.

Immunomodulatory agents

Aim at suppressing the autoimmune process. The armamentarium includes prednisone, azathioprine, cyclosporine, IV Ig, and plasmapheresis.

Prednisone (Deltasone, Orasone, Meticorten)

Corticosteroids are anti-inflammatory and immunomodulating agents. They are used whenever AChE inhibitors and/or thymectomy fail. Transient worsening might occur initially, then clinical improvement shows after 2-4 weeks. Usually given over 1 or 2 years before tapering is begun. Remissions are noted in 30% and marked improvement in 40%, as shown by Mann, Johns, and Campa. Act in ocular MG and generalized MG. Can be combined with other immunosuppressive medication for better effect with lesser dose and shorter duration of administration. Pulsed IV steroids might be beneficial in refractory patients.
Regimen should be tailored according to the patient's overall improvement.

Azathioprine (Imuran)

Inhibits T-lymphocyte–dependent immune responses. Preferred drug among the noncorticosteroid-immunosuppressive agents. Can be combined with steroids to decrease their adverse effects by obviating the need to use high-dose corticosteroids. However, they require 3-12 months for clinical benefit to be noted.

Cyclosporine A (Neoral, Sandimmune)

Fungal peptide with potent immunosuppressive activity. Used as a second-line immunosuppressive agent. Its adverse effects are more serious than azathioprine. However, unlike the latter, clinical improvement is noted within 1-2 months at most.

Intravenous immunoglobulin (Gammagard, Gammar-P, Sandoglobulin)

Unknown mechanism of action. Used in critically ill patients (eg, myasthenic crisis), instead or in combination with plasmapheresis. Action starts in a couple of days, but it does not last for too long.

Mycophenolate mofetil (Cellcept)

Derivative of mycophenolic acid (MPA), it blocks the de novo pathway of guanosine nucleotide synthesis by inhibiting the activity of inosine monophosphate dehydrogenase. Both T and B lymphocytes are highly dependent upon the de novo pathway, whereas other cells use the salvage pathway of nucleotide synthesis. As a result, MPA selectively inhibits lymphocyte activity. Mycophenolate mofetil was recently shown to be effective in MG. It is recommended to be used as steroid-sparing immune modulator. Onset of action is variable and usually starts between 1-12 months.

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