Q. Could you please tell me about Lou Gehrig's disease, or let me know where I can find out more about it? Specifically, I'd like to know how fast it spreads through the body and if age is a factor. Is there anyone in the area that specializes in its treatment?

A. Named after the famous baseball player who died of it, Lou Gehrig's disease is the popular name for amyotrophic lateral sclerosis, commonly called ALS. Amyotrophic means muscle-wasting, and lateral sclerosis refers to scarring (sclerosis) of nerve cells on either side (lateral) of the spinal cord.

ALS is a rare disease. Only about one in 50,000 to 100,000 persons gets it, and it typically strikes people in their forties and fifties. The cause is unknown, there is no cure, and the illness is ultimately fatal. People with ALS live an average of two to five years.

ALS destroys certain nerve cells in the spinal cord and brain, leading to a wasting away of the muscles they control. People with ALS have slowly progressive weakness, especially of the hands, arms, legs and feet. They may find opening jars or getting up from a chair increasingly difficult. ALS can also affect the tongue and muscles of chewing and swallowing. Eventually even the muscles of breathing become affected, and many ALS victims die from inability to breathe.

Neurologists specialize in treating ALS, and you can get more information, support and counseling about this devastating disease from the following resources:

*The ALS Support Group, sponsored by the National Hospital for Orthopaedics and Rehabilitation. Call Gail Raymond at 553-2462.

*ALS Society of America. The local representative is Elmer Cerin at 362-0923.

*ALS Association (national office), 185 Madison Ave., New York, N.Y. 10016, (212) 679-4016.

Q. I'd like to know more about steroid medications. What are the pros and cons of using cortisone and prednisone? What diseases are they good for?

A. Cortisone and prednisone are commonly called steroid medications. Actually, steroids are a large class of substances in the body, which include many hormones, vitamins and cholesterol. But when medical people talk about steroid medications, they're usually referring to certain substances produced by the adrenal glands, which lie on top of the kidneys.

The adrenal glands play a role in the so-called "flight or fight" responses. They make adrenalin (not a steroid), which gives you an extra burst of energy in a race, or a sudden jolt when you're startled. They also make cortisone and related substances, which help your body fight disease and respond to stress.

Doctors use these naturally occurring substances, or synthetic substitutes such as prednisone, to boost a person's ability to combat a wide range of disorders including certain types of arthritis, such as rheumatoid arthritis; many skin conditions, such as eczema and psoriasis; allergic disorders such as severe asthma; inflammatory diseases such as ulcerative colitis and lupus; and cancers such as leukemia and lymphoma.

These powerful drugs come in different forms -- topical creams, pills, injections, enemas, nose sprays, inhalation sprays and eye drops. The risks of use are many, and increase with higher doses and longer duration of use. Injection or pills have higher risk than topical therapy and sprays.

One serious but rare problem that can occur in people taking high doses for long periods of time is that their adrenal glands will "shut down" and not respond to severe stress, such as major infection, injury or surgery. For this reason, I advise people taking long-term steroids to wear a bracelet identifying them as steroid users.

Taken for short periods of time, especially a week or less, steroids are generally safe medicines. Among the side effects of long-term use, however, are the following: swelling and fluid retention, thinning of the skin, glaucoma and cataracts, increased blood pressure, intestinal ulcers, bone thinning (osteoporosis), mood changes, muscle weakness, and worsening of some infections, such as tuberculosis.

Some rules of thumb to follow to reduce side effects are to take the lowest dose necessary for the shortest time, and on alternating days if possible. Also, it's best to take the medicine in a single dose in the morning to match the time of the body's peak production of adrenal steroids. When stopping steroid medications, your doctor will usually taper the dose gradually, to allow your adrenal glands to resume normal production.