Dear Doctor: Our dad’s left eye and the side of his face started to droop suddenly, and it seemed like he’d had a stroke. The doctor says it’s actually Bell’s palsy. What is that?

Dear Reader: We can imagine the concern -- and subsequent relief -- when the signs that suggested your father had suffered a stroke turned out to be Bell’s palsy. Although the two are quite different, there is some crossover in symptoms. Add in the fact that, unlike stroke, Bell’s palsy isn’t that well-known, and it’s easy to understand the confusion.

Bell’s palsy is a type of temporary facial paralysis that arises from damage to the facial nerve. For fellow science nerds, this is the seventh cranial nerve, which animates the muscles we use to make facial expressions like smiling, raising our eyebrows, frowning and winking. It’s also involved in the sense of taste, the functioning of the salivary and tear glands, and the muscles of a small bone in the middle ear.

Although the exact cause for Bell’s palsy isn’t known, it occurs when something causes the nerve to become swollen, inflamed or compressed. Illness, injury and a family history of the disorder may also play a role.

As happened with your dad, the symptoms of Bell’s palsy can appear quite suddenly. In other cases, the paralysis may take a few days to develop. The onset of facial drooping, which usually occurs on only one side of the face, can indeed seem like the effects of a stroke. So can the ensuing weakness, numbness or twitching. Other possible symptoms of Bell’s palsy include headache, mild fever, ringing in the ears, pain behind the ear or near the jaw of the affected side, drooling and changes to taste and hearing. Once the symptoms begin, there is no known way to stop them.

About 40,000 people in the United States develop Bell’s palsy each year. It affects men and women at equal rates, and it is most common between ages 15 and 60. People living with diabetes and those recovering from a respiratory ailment such as a cold or the flu appear to be at greater risk. With no diagnostic tests currently available, Bell’s palsy is identified via a physical exam and the process of elimination. The symptoms are localized and specific, though, so it’s not a difficult diagnosis.

Mild cases don’t require treatment and begin to resolve on their own, often within two or three weeks of the onset of symptoms. In most people, facial nerve function returns to normal within three to six months.

It’s possible -- but quite rare -- for the symptoms to become permanent. Also possible but rare are recurrences of the disorder. In more serious cases, steroids such as prednisone can be effective in reducing inflammation and swelling. If infection is present, it will also be addressed. Since the facial paralysis can affect the eyelid and tear ducts, it’s important to take steps to protect the affected eye from debris, and to keep it lubricated.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: What's with all the ads for brain-enhancing products? Prevagen is one that claims it’s been clinically proven to help, but my family doctor says that it hasn’t. Who’s right? Do these products actually help with memory issues?

Dear Reader: More than one-third of the United States population is now aged 50 and older, a time of life when people start noticing changes to memory and the ability to learn. With each momentary lapse -- fumbling for a word or forgetting a name -- people are reminded of their aging brains. It’s not surprising that a multibillion-dollar industry in brain health supplements has sprung up.

These products promise not only to preserve and enhance memory, but to sharpen focus, boost attention spans, lift moods and increase creativity. Supplements marketed as brain boosters typically include omega-3 fatty acids, certain B vitamins, vitamin E, ginseng and ginkgo biloba extract. However, despite decades of study into whether these substances actually work to preserve or enhance brain health and functioning, the research remains inconclusive.

When it comes to Prevagen, a memory supplement derived from jellyfish, the parent company’s advertising claims led the Federal Trade Commission to charge it with fraud in early 2017. That legal battle is ongoing. Meanwhile, since the product is marketed as a supplement, it doesn’t have to undergo Food and Drug Administration testing for safety or review for efficacy. It’s also free from a range of FDA scrutiny and oversight.

You’re correct that the company’s marketing cites positive results from a clinical study. But critics point out that these claims arise from selective use of data drawn from a single study, which was carried out in-house by the parent company of the product. In that study, the product and a placebo were found to be equally effective.

Until the day that science develops a real brain pill, we advise our patients to preserve their cognitive health the old-fashioned way. That is, eat right, control blood pressure, get enough sleep and exercise regularly. A diet that focuses on fresh fruits and vegetables, lean meat, fish, whole grains, legumes and healthful fats has been shown to reduce the risk of chronic disease, including heart disease. That’s important because heart disease, as well as uncontrolled high blood pressure, have been linked to cognitive impairment later in life.

Research has also repeatedly drawn a connection between regular exercise and cognition. Not only does a mix of aerobic exercise, weight training and stretching improve strength, balance, endurance and mood, it has been shown to help the brain maintain existing neural connections, and to build new ones. With just 30 minutes of moderate exercise each day, you’ll exceed the federal guidelines for adults, which recommend about 150 minutes per week.

One final piece of the cognitive health puzzle is ongoing social interaction. Recent research suggests that adults who have regular contact with other people have better memory and preserve their cognitive abilities to a greater degree than do adults who are solitary.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I just turned 55 and have noticed that I get winded faster these days when I go running. Does getting older affect how much air your lungs can hold? Is there any way to increase it?

Dear Reader: Yes, aging does have an effect on our lungs and how they function. In fact, the decrease in capacity begins about a decade after our lungs become fully mature, which is in our early- to mid-20s.

Your question addresses something known as tidal volume, which is the amount of air that moves into and out of our lungs with each breath. For healthy adult women, tidal volume is about 0.4 liters. For men, it’s about 0.5 liters. However, the volume of each breath is one of several variables that affect breathing function.

In addition to the lungs, the respiratory system includes the diaphragm, the dome-shaped muscle that separates the chest cavity from the abdomen; it also includes the ribs, sternum and supporting muscles and soft tissues, also referred to as the thoracic cage. Each of these plays an important role in breathing. The lungs hold the air, the motion of the diaphragm causes the lungs to fill and empty, and the thoracic cage provides support and protection.

As we age, the respiratory system undergoes gradual changes that affect its structure, physiology and immune function. Injury, poor posture, osteoporosis and the natural shrinkage of bones, muscles and soft tissues all contribute to a decrease in the size of the thoracic cage. This, in turn, has an effect on maximum air volume. A decrease in the strength of the diaphragm also affects how much air can be drawn into (and out of) the lungs. The lungs themselves lose elasticity with age, and the millions of tiny air sacs that they contain, known as alveoli, can lose shape and become “baggy.” Smoking and exposure to air pollution contribute to a decline in lung function. So do repeated respiratory illnesses, another reason to stay current with flu and other vaccinations.

The good news is that regular exercise can help to maintain lung function and tidal volume. Aerobic exercise is a great way to keep your lungs fit. Resistance training that targets the chest, shoulders and back muscles helps maintain strength and flexibility of the diaphragm and the thoracic cage. Breathing exercises, such as those done in yoga, are excellent tools for maintaining or increasing lung capacity. In deep breathing, also known as diaphragmatic breathing, you breathe in through the nose to fill your lungs from top to bottom. Be sure to also breathe out as deeply as possible, so you get the maximum volume of air moving through the lungs. Adding resistance to the exhale by pursing the lips or tightening the throat is also beneficial.

It’s important to remember that age-related changes to lung capacity occur gradually. If you ever experience a sudden or dramatic change to breathing, which can signal illness or injury, see your doctor right away.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)