Dear Doctor: My husband was diagnosed with avascular necrosis in his right hip. Can you please tell me what this is and how to treat it? He's not a surgical candidate for hip replacement due to his age, and he doesn't want to take prescription pain medication. What can he do?

Dear Reader: These are smart questions to ask. As the name implies, avascular necrosis of the bone is an interruption of the bone's blood supply. This supply consists of a rich, thin network of blood vessels similar to the small roots of a plant. Because blood supply from surrounding tissues is limited, the bone becomes dependent upon these small vessels to survive; if blood flow is interrupted, the bone nourished by a particular vessel will die. This damages the architecture of the bone and causes a loss of calcium, eventually causing the bone in that area to collapse. Each year, 20,000 to 30,000 people in the United States are diagnosed with avascular necrosis.

Such interruption can be caused by blood clots; circulating fat; bubbles of nitrogen (seen in decompression sickness); damage from fractures or dislocations at a joint; radiation therapy; or inflammation of vessels in conditions like lupus.

Drugs can play a role as well. Anti-inflammatory steroids, such as prednisone and methylprednisolone, increase the risk of avascular necrosis, especially for people treated with high-dose steroids for a prolonged period. In fact, steroids are believed to be a factor in 21 to 37 percent of patients with avascular necrosis.

Alcohol consumption is believed to be a risk factor in 31 percent of cases, with heavy use leading to fatty deposits within the vessels. The more one drinks chronically, the greater the risk of developing the disease.

Avascular necrosis is more likely in people with lupus, antiphospholipid syndrome, sickle cell disease, acute lymphoblastic leukemia or Gaucher disease and in people who have had a transplant. Many times, the cause is unknown.

Avascular necrosis of the hip -- the most likely joint to be affected -- is often the most disabling. The pain initially felt while walking can later occur at rest and, when the condition becomes severe, patients cannot walk at all due to the joint's collapse.

That's not to say treatment might not help. Bisphosphonates, such as Fosamax, have shown benefits in some, but not all, studies. (These drugs also have been linked to avascular necrosis of the jaw.) Iloprost, a dilator of blood vessels, can increase blood flow and has been linked to a delay in the need for a hip replacement. And statins may reduce the risk of avascular necrosis in people taking steroids.

As for pain, core decompression might help. In this procedure, a needle is placed in the bone marrow to encourage bone regeneration. Also, a procedure called osteotomy can alter the bone at the hip so that the area won't be subject to further damage from walking. For most people, however, a total hip replacement is the ultimate solution, resolving symptoms in a majority of patients.

For your husband, I'd recommend drugs to slow the progression of the necrosis, as well as a second opinion from a physician who can help further assess the risks versus benefits of a hip replacement. Age alone generally isn't a deal-breaker. If he truly isn't a candidate for joint replacement, however, his doctor can assess other potential therapies.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Does loss of taste occur naturally with old age, or could it be a symptom of an illness? I'm 89, in pretty good shape with good blood pressure, but seem to be losing my sense of taste.

Dear Reader: While it's true than an impaired sense of taste can be related to illnesses that range from a simple cold to a complex neurological disorder, by the time one is 89 (congratulations, by the way!) it's more likely that the decline is age-related. To understand why, we need to talk about two of our senses -- taste and smell.

Let's begin with a tiny and amazing organ -- the taste bud. We enter the world with about 10,000 taste buds, each of which is made up of between 10 and 50 sensory cells. These cells are bundled together like the sections of an orange, and are connected to a complex web of nerve fibers.

Each bundle is tipped with a fluid-filled pore that behaves as a funnel and, via minute fibers known as taste hairs, delivers molecules to the sensory cells to be "tasted." The nerve fibers send chemical messages from the taste buds to the brain, where they are interpreted as sweet, salty, bitter, sour and savory, also referred to as "umami."

The taste buds themselves are tucked into undulating walls and grooves on the surface of the tongue, which are known as papillae. The papillae greatly increase the surface area of the tongue. This allows for a significant increase in sensitivity without a corresponding increase in the size of the tongue. Additional tasting cells are found on the roof of the mouth and along the lining of the throat.

As you may have noticed, we recover from a bite or burn to the tongue far more quickly than to other parts of the body. This is due to the remarkable rate at which the sensory cells in the taste buds can regenerate. As we age, though, these cells tend to regenerate more slowly. This affects our sense of taste.

At the same time, our sense of smell, which plays a crucial role in our ability to taste and distinguish the subtleties of flavors, also begins to diminish. When we chew, volatile molecules travel via the nasal cavity from the mouth to the nose. There, as on the tongue, highly specialized cells send signals to the brain, where the incoming data get interpreted as flavor.

Research shows that what is perceived as a loss in the sense of taste is, in fact, often a loss in the sense of smell. The tongue will tell us that something is sweet. But it's the sense of smell allows us to say whether that sweet bite is a peach or an apricot.

A diminished sense of smell has many causes. If the decline in your ability to taste is sudden or severe, a visit to your primary care physician is a good idea. He or she can perform tests to assess the degree of the loss, conduct a physical exam to rule out chronic conditions or disease, and propose medical treatment, if appropriate.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: A relative long ago diagnosed with atrial fibrillation has been behaving differently, such as sitting with his mouth gaping open, not attending to financial matters, taking too long to do errands, that kind of thing. Could silent TIAs be the culprit?

Dear Reader: Yes, they could. First, let's explain atrial fibrillation. Two chambers known as atria make up the top portion of the heart, storing blood before it goes into the two bottom chambers, known as ventricles. The atria contract first, then the ventricles, setting the overall rhythm of the heart. In atrial fibrillation, the atria are damaged or enlarged and don't contract sufficiently or rhythmically. Because of this, some blood can stay within them, leading to a clotting of blood in this portion of the heart.

If the atria contract normally or the clot mobilizes for some other reason, then the clot can move into the ventricles, where it can then shoot into the circulatory system when the ventricles contract. The clot can then become lodged in the smaller blood vessels of the brain, leading to lack of blood flow to that area. The result is either a transient ischemic attack (TIA), in which a portion of the brain loses function for a short period, or a full-fledged stroke.

Atrial fibrillation could indeed be leading to small strokes in your relative. Often, these small strokes are not noted by the patient or by family members. A study in elderly residents in Germany found that 12.7 percent of them had experienced what's known as "silent strokes." Such strokes don't have obvious symptoms; instead, they can manifest as a difficulty in performing cognitive tasks or a slowing in everyday activities. Your relative's risk of strokes linked to atrial fibrillation would be lower if he has been taking blood thinners, but they still could occur.

A CT scan or MRI can easily determine whether your relative has had these silent strokes. It's important to get such a diagnosis because if his symptoms are related to a small stroke, he'll be at greater risk of having a large, debilitating stroke.

His symptoms could be linked to another type of stroke as well -- a lacunar stroke caused by very high blood pressure and diabetes, which lead to a narrowing of smaller blood vessels in the brain. These strokes can cause loss of function in a limb or the problems traditionally found in silent strokes.

Whether caused by atrial fibrillation or a narrowing of blood vessels, multiple strokes can lead to dementia, which also may be the reason for your relative's recent behavior. Alzheimer's disease, Lewy body dementia and normal pressure hydrocephalus also can cause the symptoms you describe, and imaging of the brain and a consultation with a neurologist can confirm these diagnoses.

Let's not forget another cause: depression. Depression in the elderly can have many of the same symptoms as dementia, causing difficulty in focusing on tasks, memory and self-care. Lastly, if the symptoms in your relative developed suddenly, infection could be the culprit.

In short, your relative's symptoms have many possible causes. But you're astute in thinking that TIAs or silent strokes due to atrial fibrillation may be to blame. Please encourage him and his closest family member to see a doctor; he obviously needs medical attention and recommendations specific to his needs.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)