Dear Doctor: In the last few years I've noticed that after making an appointment to see a doctor, I'm often seen by a physician's assistant or nurse practitioner instead. What's the difference? When should I insist on being seen by a physician?

Dear Reader: You're correct -- nurse practitioners and physician's assistants are now playing larger roles in preventive health care for many Americans. While they can't replace physicians, what they can do is take on a significant range of duties in primary care. This frees up doctors to manage the big picture of a patient's health care and to spend more time with difficult, complex cases.

Let's start with some definitions.

The difference between a physician, a physician's assistant and a nurse practitioner is in their schooling. Each is a nationally certified and state-licensed medical professional who has successfully completed four years of college as an undergraduate.

Aspiring physicians go from college to four years of medical school, followed by an additional three to seven years of specialized training as residents. Many then undergo additional training in fellowships, which can last from one to three years.

For physician's assistants, or PAs, college is followed by three years of medical training in an accredited program. More than 2,000 hours are spent in clinical rotations that include family medicine, internal medicine, general surgery, emergency medicine, pediatrics, and obstetrics and gynecology. In order to enter practice, PAs must pass a national certifying exam and qualify for a state license. All PAs are required to work with a supervising physician.

A nurse practitioner, or NP, is a registered nurse whose advanced training allows her or him to perform an expanded range of duties. These include physical exams, diagnosing and treating chronic diseases like diabetes and arthritis, ordering and interpreting diagnostic tests, and prescribing medications. An NP can perform procedures like stitching a wound, setting a break and performing a skin biopsy. Their focus is preventive medicine, wellness and education. Depending on the state, NPs may work independently of a physician's supervision.

Both PAs and NPs have a role in surgery, but to what extent depends on laws and regulations, which vary greatly from state to state.

Like many of our colleagues, we see a role for PAs and NPs in preventive care, such as well-woman and well-baby exams, geriatric assessments, and in urgent care cases that are not complex or severe. Here at UCLA, many hematologists and oncologists work alongside an NP. The NPs help care for complex cancer patients, coordinating imaging, therapy and routine follow-up visits.

By handling certain parts of a medical visit, like collecting data, compiling a medical history and assessing general health, PAs and NPs free up physicians' time so they can focus on more complex issues.

This leads us to the second part of your question, which is when to ask to see a physician. We suggest that you make it a practice to ask whether a doctor is available during your appointment. That way, if an exam or test reveals anything troubling or abnormal, if you want a second opinion about something the PA or NP has said or if you have questions that you prefer to have answered by your doctor, then you know he or she is available to you.

(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: The back of my neck hurts when I have my hair shampooed at the salon. This worries me because I've read that some people have strokes when they have this type of shampoo, due to the arteries in the neck. Is there truth to this?

Dear Reader: While it's true that some individuals have experienced strokes after spending time in a shampoo chair at a hair salon, it's actually quite rare. And don't worry -- there's more to it than simply leaning one's head back for a few moments.

An early take on the topic appeared in the Journal of the American Medical Association in 1993. Since then, additional research and case studies have been published, and occasional cases of women -- and a few men -- suffering strokes after a visit to the shampoo chair have made a splash in the headlines.

Most recently it's been in the news because a woman filed a lawsuit against a hair salon in San Diego, claiming a neck injury she suffered while getting a shampoo led to a stroke two weeks later. Specifically, she said an artery in her neck was damaged when she angled her head back and rested her neck against the hard surface of the sink. This reportedly caused bleeding, which led to a blood clot, which caused a stroke.

In media coverage, the injury goes by the name "beauty parlor stroke syndrome." In reality, though, what we're talking about is cervical artery dissection. That is, a rip or tear in one of the arteries in the neck, which supply blood to the brain. And despite what the injury's colorful nickname implies, it has multiple causes outside of the shampoo chair.

The injury begins with the anatomy of the neck, which includes arteries that run along the back of the vertebrae and deliver blood to the brain. In the people who experienced the so-called beauty parlor stroke, either one of two things appears to have happened: An artery was damaged by pressure from a vertebra, or pressure from the rim of the sink or the back of the chair squeezed the artery shut. In either scenario the result was the same -- a lack of blood flow to the brain, which is the definition of stroke.

This same injury has been seen in individuals undergoing prolonged dental work, receiving anesthesia, having chiropractic manipulations of the neck, and even painting a ceiling or doing yoga. In each case, hyperextension of the neck played a part.

If you're worried about your safety while getting a shampoo, talk to your hairdresser. Make sure the chair is adjusted properly for your height. Ask for additional towels for padding and support. Don't allow your neck to hyperextend. Or skip the backward approach entirely and ask to stand up and lean forward while your hair is washed.

Neck pain is not necessarily a sign that something is wrong. However, if you experience symptoms like loss of muscle tone in the face, weakness or paralysis on one side of the body, slurred speech, impaired vision or loss of coordination, you should definitely -- and immediately -- seek medical attention.

(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: I am 56 and in menopause. A couple of months ago, I started having severe restless leg syndrome, which even included my arms. I am now taking ropinirole before bed every night -- I also take Pristiq for depression. Although the medication has eliminated my restless leg syndrome, I worry about potential long-term effects. Any idea what could cause restless leg syndrome?

Dear Reader: Restless leg syndrome (RLS) is appropriately named. The syndrome is defined by an uncomfortable urge to move one's legs or arms during periods of inactivity. Because most people are less active in the evening, these symptoms often are first noted at that time. People describe the feeling as a pulling, creeping, cramping, crawling or tingling sensation that makes them feel an urge to move in order to relieve it. The periodic leg movements can also awaken people with the condition -- or those who sleep with them.

Restless leg syndrome occurs more often in people of Northern European ancestry; it's rare in those from East Asia and from Africa. Overall, it affects 2 to 3 percent of the population.

There is no specific cause of RLS, although genetic factors can play a part. Forty to 60 percent of people with RLS report a family history of the condition. Low iron storage can also be a factor, as can alterations in the brain function of the neurotransmitter dopamine.

Certain medications can worsen RLS symptoms, such as the antihistamine diphenhydramine and antidepressants. Thus, the antidepressant Pristiq (desvenlafaxine) could make your symptoms worse, but there are no specific studies of its connection with RLS.

Because poor sleep can aggravate RLS, be sure you are getting good rest. Exercise also appears to decrease symptoms, as can reductions in caffeine. Doing mental activities during a person's evening "down time," such as crossword puzzles, can reduce the focus on symptoms.

Medication that binds dopamine receptors, such as the ropinirole that you're taking, can decrease the symptoms of restless legs. Such medications are started at night and, although they can initially cause drowsiness, this subsides after 10 to 14 days. One problem with such drugs is that they can lead to rebound symptoms -- that is, the restless leg sensations -- in the morning. An even bigger problem is that long-term use can lead to decreased effectiveness, a shorter duration of action, symptoms noted earlier in the day and a spread of symptoms into the arms; these problems can worsen with increased dosages. To reduce the likelihood of this, I'd recommend staying on low doses of the drug and not taking it on a nightly basis, if possible.

You might also want to consider the anti-seizure medications gabapentin or pregabalin. They may not be as effective as ropinirole, but there is less likelihood of rebound or worsening of symptoms. Benzodiazepines, such as clonazepam, can be used for RLS, but can lead to tolerance or even dependency.

In summary, have your doctor check your blood ferritin level, a marker for iron stores. If it's low, consider iron supplementation. Also, be sure to increase your levels of exercise, decrease your caffeine intake and try mental activities at night.

If you feel that your symptoms are worsening on the ropinirole, talk to your doctor further. You have other options.

(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.)