AN AUTOIMMUNE NEUROMUSCULAR DISORDER.
MEDICAL TREATMENT :
MG is associated with many other autoimmune disorders. Patients must be checked for the following conditions:
Rheumatoid arthritis
Systemic lupus erythematosus
Pemphigus
Hashimoto thyroiditis
Scleroderma
Dermatitis herpetiformis
Autoimmune hemolytic anemia
Polymyositis
Sarcoidosis
Management of myasthenic crisis requires careful monitoring. Arterial blood gas values must be monitored in patients with increasing weakness.
Plasmapheresis is an expensive procedure used in patients in myasthenic crisis. Together with steroids, plasmapheresis is a very effective treatment. It consists of 3-6 exchanges of 2-3 L over 1-2 weeks. It is safe during pregnancy and has even saved patients during fulminant crises. Plasmapheresis can result in premature delivery because of large hormone shifts. Other complications can occur from hypovolemic reactions or allergies.
Intravenous immunoglobulin is also useful in patients in myasthenic crisis. It is thought to interfere with anti-AChR antibodies. It is infused at 0.4 g/kg/d for 5 consecutive days. Improvement is noticeable in 3-21 days and lasts as long as 3 months.
Monitoring patients for infection is important, especially those on steroids.
Many patients develop depression or comorbid depressive episodes. Bupropion (Wellbutrin XL) has been studied extensively and may be a good addition for these patients.
Surgical Care:
Surgery is very stressful; therefore, delivery via cesarean delivery is reserved only for necessary cases. Also, the hazards of anesthesia must be kept in mind because patients are sensitive to sedatives and narcotics. Not depressing respiration is important. In 1978, Rolbin and colleagues reported on their evaluation of the safety of anesthesia for MG patients. They concluded that regional anesthesia is good for abdominal delivery. They stated that epidural anesthesia could be used to decrease the requirements of systemic medications and provide anesthesia for outlet forceps. Amide-type local anesthetics are thought to be safe when large doses of drugs are needed. The group recommended general endotracheal anesthesia for cesarean delivery in patients with respiratory problems. Depolarizing anesthetics must always be avoided.
Thymectomy is recommended for most young patients. It improves the disease course and can improve remission. Thymectomy is thought to remove an antigen source and reduce an anti-AChR antibody source. A thymoma, which is a potentially invasive tumor that must be removed, is found in few cases. In 1999, Batocchi et al reported that 4 of 44 patients had thymomas. To avoid any postoperative problems, thymectomy is performed when the disease is in control. Plasmapheresis can be used for disease control. In 1986, Ip et al used thymectomy as a treatment for myasthenic crisis during pregnancy. The patient improved, and although she had to receive large doses of pyridostigmine, she delivered her baby at 39 weeks' gestation.
Activity: Rest is very important to restore muscle strength, especially during pregnancy.
DRUG TREATMENT : Combination drug therapy is reported to be safer and more effective than monotherapy. Pharmaceutical treatment for MG is very effective.
1. ANTICHOLINESTERASE MUSCLE STIMULANTS -- Preferred treatment for MG and reportedly are safe in pregnancy. Increase the amount of acetylcholine available to bind to receptors. Neostigmine was the first drug used for MG.
- NEOSTIGMINE ( PROSTIGMINE ) : Longer-acting cholinesterase inhibitor that can be used when edrophonium is ineffective. Inhibits destruction of acetylcholine by acetylcholinesterase, which facilitates transmission of impulses across myoneural junctions. Although has a short duration, activity is more pronounced.
Because of changed renal excretion rates and changed absorption of drugs, patients who are pregnant receive increased doses in increments of 5-10 mg. IM injection may eliminate these problems.
- PYRIDOSTIGMINE ( MESTINON ) - Acts in smooth muscle, CNS, and secretory glands. Blocks action of acetylcholine at parasympathetic sites and facilitates transmission of impulses across myoneural junctions.
Longer-acting medication that may last throughout night. Edrophonium test can be used with caution to find therapeutic doses.
Because of changed renal excretion rates and changed absorption of drugs, pregnant patients receive increased doses in increments of 15-30 mg. IM injection may eliminate these problems.
2. CORTICOSTEROIDS : Immunosuppressants useful in treatment of MG. DOCs for severely ill patients. Work by decreasing antibody synthesis and inhibiting CD4+ T-cell proliferation. Johns' regimen is the accepted regimen for steroid use in MG. Prednisone is fairly safe during pregnancy. Patients who wish to become pregnant are recommended to get pregnant while in steroid-induced remission. Cleft lip and palate in newborns of patients on steroids were noted in a few instances. High-dose corticosteroids can lead to premature rupture of membranes. Weight gain and cushingoid appearance are common complications.
- PREDNISONE : Immunosuppressant for treatment of autoimmune disorders. May decrease inflammation by reversing increased capillary permeability and suppressing PMN activity. Stabilizes lysosomal membranes and also suppresses lymphocytes and antibody production.
Steroids cannot be discontinued because relapse will follow.
3. ANTIMETABOLITES : Azathioprine is used when response to corticosteroids is not adequate or when corticosteroid dosage must be decreased. Also, this drug added if symptoms are not controlled satisfactorily with acetylcholinesterase. It is converted to the metabolite mercaptopurine and inhibits T-cell reactivity. Azathioprine is found to reduce serum anti-AChR antibody titers. Cyclosporine is a strong immunosuppressant and inhibits T-cell activation. It is restricted to patients who do not respond well to other medications.
- AZATHIOPRINE
- CYCLOSPORINE
4. IMMUNOGLOBULINS : Useful in myasthenic crisis. Neutralize circulating myelin antibodies through antiidiotypic antibodies. Down-regulate proinflammatory cytokines (including INF-gamma), block Fc receptors on macrophages, suppress inducer T and B cells and augment suppressor T cells, block complement cascade, and promote remyelination.
- IMMUNE GLOBULIN, I.V.