Dear Doctor: Our sons are ages 9, 11 and 14, and like all of the other schoolkids we know, they’re hauling around crazy-huge backpacks all day. What does that weight do to a child’s back? Can carrying a heavy backpack every day cause scoliosis?

Dear Reader: We hear from a lot of parents about the hefty load children carry around while they’re at school.

By the time kids stow all of the textbooks, notebooks, laptops, tablets, binders, snacks, water and miscellaneous school supplies they’ll need during a typical day, these packs can easily tip the scales at 10 pounds -- and frequently much more. Considering that the current recommendation is that a child’s backpack shouldn’t exceed 10 percent of his or her body weight, the plain truth is that our kids are spending their weekdays yoked to considerably more weight than is good for them.

When it comes to scoliosis, a condition in which the spine grows with an abnormal sideways curve, there is no evidence that carrying a heavy backpack will cause it. But plenty of kids with overloaded backpacks do wind up paying a physical price. All of that weight forces them to hunch, slump, tilt or even stagger as they walk, which can stress, torque or compress the spine, neck and shoulders. This can result in aches, pain and muscle strain. Over the long term, the adjustments and contortions needed to repeatedly lift and lug around a hefty backpack during the school day can lead to nerve damage, which reveals itself in tingling, numbness or pins-and-needles sensations.

A study published in 2016 in the Spine Journal found that more than 60 percent of the 5,300 students surveyed suffered from backpack-related pain. And while much importance is placed on the weight of a pack, the study found that how long a pack is carried each day also had a bearing on pain and injury.

Left to their own devices, kids will often choose a backpack for its color, shape or design. That’s when we parents have to step in. Ergonomics aren’t nearly the draw that a cool logo or graphic can be, but they can save your child pain and injury. When shopping for a backpack:

-- Select the proper size. Your child’s backpack should be no wider and no longer than his or her torso. Make sure the pack doesn’t reach more than just a few inches below the waist.

-- Get a pack with wide, padded shoulder straps that are easily adjustable. A padded back panel adds to comfort, too.

-- Just as with backpacks that are used in hiking and camping, chest and hip belts in school packs can help to equalize and stabilize the load.

-- Instead of a pack with a single central pocket, look into those with multiple compartments. Not only can that help with organization, but it makes it easier to evenly distribute the weight.

-- Help your kids evaluate his or her gear and work to lighten the daily load.

To catch potential problems as quickly as possible, let your kids know that when it comes to backpack-related aches or pains, you always want to know the details ASAP.

(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 was a huge Luke Perry fan in high school, and like so many others, I was shocked that he had a stroke at just 52 years old. Isn’t that awfully young? How do you know if you’re having a stroke?

Dear Reader: While it’s true that the majority of strokes occur in people 65 and older, they can happen in people of any age. This includes not only young and middle-aged adults, but also children and even infants in utero.

Stroke is the fifth-leading cause of death in the United States. Risk factors include high blood pressure, high cholesterol, smoking, obesity and diabetes. Of the 795,000 people each year who have a stroke, 140,000 do not survive. A significant percentage of those who do survive are left with a range of disabilities that affect speech, movement and cognition. One of the challenges for younger stroke victims is misdiagnosis. Symptoms can be mistaken for conditions like migraine, seizure and inner ear disorders.

A stroke occurs when the blood supply to the brain is interrupted, which happens in two ways. The most common type of stroke, known as an ischemic stroke, occurs when blood is unable to travel through a blood vessel and reach the brain. This can be due to a clot that arises in or travels to the brain and blocks the vessel, or to narrowing of the blood vessel itself. In a hemorrhagic stroke, the second major type of stroke, the blood vessel tears or ruptures. In both types of stroke, the result is the same -- the oxygen and nutrients carried by the blood can’t reach the brain cells. In a very short period of time, the brain cells begin to die.

A third type of stroke is known as a transient ischemic attack, or TIA. This is when stroke symptoms appear for a brief period of time but then go away. These so-called "mini strokes" can sometimes be precursors to a major stroke, so it’s important to take TIAs seriously and seek medical treatment immediately.

Signs of stroke include sudden weakness or numbness in a limb or in the face, often on just one side of the body. Sudden dizziness, confusion, garbled speech, loss of balance or coordination, or problems with eyesight in one or both eyes can also signal a stroke. So can the advent of a sudden headache, often quite severe, sometimes accompanied by tingling sensations in the face or body.

A useful memory prompt for stroke symptoms is the word FAST. The letters represent three major indicators of stroke. F is for face drooping, A is for arm weakness and S is for speech. The final letter, T, stands for “time to call 911.” That’s particularly important because swift treatment can be the difference between life and death. It can also affect the level of disability that the stroke causes in a survivor. Studies show that receiving emergency medical care within three hours of the first symptoms of stroke results in less disability three months later as compared to those for whom medical care was delayed. So no matter someone’s age, when symptoms suggest a stroke, seek immediate medical help.

(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: Stem cell therapies are being heavily marketed here in Florida as promising treatments for a variety of illnesses, but I have my doubts. As a retired doctor, I hate to see people go into debt to pay for something fraudulent or unsafe. Am I being too critical?

Dear Reader: Stem cell therapies are making headlines right now in two very different ways. One is the news that a patient infected with HIV has been in remission for 18 months following a stem cell transplant. The other stem cell news arises from the subject of your letter. That is, unproven and unapproved stem cell treatments. These are being widely marketed as miracle cures for everything from Parkinson’s disease, autism, arthritis and dementia to depression, multiple sclerosis, macular degeneration and traumatic brain injury.

Although the use of embryonic stem cells is federally monitored, adult stem cells can be extracted from a patient’s own body. That makes regulation and oversight challenging.

Despite extravagant claims of success by stem cell clinics, outcomes are largely unproven. However, the potential dangers are clear. In the past year, at least 17 people in five states have become gravely ill following stem cell treatments that used injections of umbilical cord blood and required hospitalization. In one such case, a man who received an injection of umbilical cord blood to address joint pain developed sepsis, a life-threatening infection. He spent 58 days in the hospital.

Last December, the Centers for Disease Control and Prevention published a report warning about unapproved stem cell treatments. The Food and Drug Administration has issued numerous warnings on the issue as well.

The allure of stem cells is that they are a kind of blank canvas. These "unprogrammed" cells divide rapidly and have the ability to change into other types of cells, such as bone, brain or muscle cells. As a result, stem cells are the centerpiece of regenerative medicine, in which disease and injury are treated by growing new cells, or by replacing or repairing those that are dead and damaged.

Thanks to their unique properties, stem cells are seen as important tools in potential new therapies for diabetes, Parkinson’s and heart disease, among others. But because stem cells are undifferentiated, they must first go through a special process, somewhat like programming, in which they are prepared to become specific types of cells. It is during this process, as well as during the act of transplantation, that potential risks to patients can arise.

According to the CDC, a number of vials of stem cell products made from umbilical cord blood were found to be contaminated with E. coli. Even before this latest spate of bad news, various unapproved stem cell treatments were found to cause harm to patients that included severe respiratory illness, blindness and even death.

With few consumer protections in place at this time, the FDA recommends that patients avoid stem cell therapies that are not part of an approved clinical trial. To find ongoing and upcoming clinical trials that use stem cells, visit clinicaltrials.gov. The home page contains a form that you can use to focus your search.

(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.)