DEAR DR. DONOHUE: My husband is 66 years old and has been diagnosed with hyponatremia. He has high blood pressure and takes medicine for it. He is also an alcoholic, eats very little and has lost a lot of weight.

Will you please discuss hyponatremia? I’m at my wits’ end because he looks so bad. He sees a kidney specialist, and I found “hyponatremia” on a piece of paper he brought home from the doctor. — J.B.

ANSWER: Hyponatremia is a low blood level of sodium. It’s not really an illness. It’s a sign of many possible disorders. Something in the body has gone wrong and makes the body retain too much water or lose too much sodium (salt). Excessive sweating, drinking way too much water, burns, vomiting, diarrhea, adrenal gland abnormalities, pituitary gland problems, liver diseases, kidney diseases and congestive heart failure are some of the processes that lead to a drop in blood sodium.

A frequent cause, and perhaps your husband’s cause, is diuretics — water pills. They’re often used for control of high blood pressure. Many of them induce a loss of sodium. This is corrected by adjusting the diuretic dose.

Most of the time the sodium drop isn’t that great, and no symptoms are generated. I have to believe that applies to your husband. His doctor would not have let him come home if his sodium level was too low. Large drops in sodium cause nausea, a general sense of discomfort and headaches. Very large drops lead to lethargy and mental confusion.

About your husband’s other problems, I don’t have a ready answer.

DEAR DR. DONOHUE: I have a Baker’s cyst behind my left knee. I have been told it can be cured when I have my knee replaced. However, that is impossible because of another physical condition.

I can get very little information about this disorder. I was told to wear an elastic stocking, which I do and which seems to help. What is a Baker’s cyst? Are there things I should be doing? — W.K.

ANSWER: Ever hear of bursas? They’re small, pancake-shaped affairs that are wedged between bones and tendons to prevent friction when the tendon rubs against bone. A Baker’s cyst is a swelling of a bursa behind the knee. It’s actually connected to the knee joint by a tunnel. The tunnel has a one-way valve that closes as fluid from the knee finds its way to the bursa. The bursa swells. The basic problem, most often, lies with the knee itself — arthritis, torn cartilage or other joint problems. Baker’s cysts are quite common.

What’s this about needing a knee replacement to fix it? That’s not true. A doctor can drain the cyst with a needle and syringe. Often, the cyst reforms. Injecting cortisone into the cyst after drainage lessens the chance of recurrence. Elevation of the leg and a compression bandage like an ACE wrap are helpful. So are anti-inflammatory medicines like Aleve and Advil if you can tolerate them. In stubborn cases, a doctor can surgically remove such a cyst. If the cyst isn’t bothering you, you can let it be. Your current treatment is sufficient.

DEAR DR. DONOHUE: I need to know about shingles. Can you get them on the scalp? My hair has been coming out, and I would like to know if shingles is the cause. Who should I see about it? Will my hair grow back? — M.B.

ANSWER: Shingles can occur in any place served by nerves, and that’s the entire body. They rarely appear on the scalp. They’re not a common cause of hair loss, which has many, many causes. Shingles is the awakened chickenpox virus that lives in nerve cells ever since childhood infection. It’s painful.

Other explanations are more in line. If you have round bald spots, a condition called alopecia areata is the likely cause.

You’re going to have to get your family doctor or a dermatologist involved to track down the exact cause for the proper treatment.

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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