DEAR DR. DONOHUE: I am 50. About a month ago, I was told I have a muscle problem in my eyes — myasthenia gravis. I have double vision. It’s hard for me to keep my eyelids open. I am on pyridostigmine and prednisone. Will this ever go away? Where did it come from? I am a welder. Did my job have something to do with it? — M.H.

ANSWER: Myasthenia gravis is a disconnect between muscles and nerve. For muscles to perform, they have to be activated by acetylcholine, a chemical that comes from a nerve serving the muscle. Acetylcholine lands on the surface of a muscle. It’s a situation like tying up a boat at a dock. When acetylcholine lands on the muscle dock (a receptor), the muscle responds. In myasthenia, the immune system has covered the landing docks with antibodies. Acetylcholine can’t land on them. The muscles become weak. This is an autoimmune illness, one where the body’s immune system turns on its own tissues — here, the muscle receptors.

Your job as a welder had nothing to do with it.

Double vision is the result of eye-muscle weakness. The eye muscles can’t align the eyes properly, so two images are seen instead of one fused image. The eyelid muscles are weak, and that’s why your lids droop down. Other muscles might be affected in the same way. If the swallowing muscles are targeted, swallowing becomes a problem. Arm and leg muscles also can be involved. Usually, the weakness fluctuates; it’s not there all the time.

Today’s medicines make it possible for most people with myasthenia to carry on an active life. Your two medicines are prescribed often and are quite effective. Pyridostigmine (Mestinon) increases the amount of the nerve chemical acetylcholine. Prednisone makes the immune system behave. The thymus gland, located in the upper chest, is a mysterious gland. Its removal often improves myasthenia. Your doctor will talk to you about this.

Contact the Myasthenia Gravis Foundation of America at www.myasthenia.org or by phone at 800-541-5454. It will provide you with the latest information about myasthenia and put you in touch with chapters near you.

DEAR DR. DONOHUE: I need an operation on my back. A second opinion is now in progress. I am currently taking Coumadin. I am fearful of stopping the medicine. Are there alternatives? — H.S.

ANSWER: You face a dilemma encountered by people who are on blood-thinning medicines (anticoagulants) like Coumadin and are scheduled for surgery. Stopping the medicine risks forming a clot that could cause a stroke. Not stopping the medicine risks excessive bleeding during the surgery. There are ways to surmount this predicament.

If surgery is short and not complicated, the anticoagulant could be continued.

For long, involved surgery, Coumadin can be stopped and the surgery scheduled for a time when its anticoagulation effects haven’t completely worn off.

Or anticoagulation with short-acting heparin can substitute for Coumadin. The heparin is stopped hours before the surgery and is restarted as soon as the surgeon has securely tied all blood vessels.

DEAR DR. DONOHUE: Some time ago, you wrote about multiple system atrophy. Can you repeat this? — J.S.

ANSWER: Multiple system atrophy is a group of disorders that share a variety of symptoms, including some symptoms of Parkinson’s disease, symptoms of trouble with the cerebellum (such as loss of balance), symptoms denoting damage to other parts of the brain and spinal cord, and symptoms of trouble with the autonomic nervous system. The autonomic nervous system takes part in regulating blood pressure, heart rate, sweating and all the many bodily functions not under voluntary control. Fainting spells, walking difficulty because of imbalance, fluctuations between very high and very low blood pressure, loss of bladder control and trouble emptying the bladder are examples of the things that happen in MSA. No specific medicine works for all MSA symptoms. Medicines that help control individual problems like low blood pressure are useful. Physical therapy helps with balance problems.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.

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