Dear Doctors: I’m having radial nerve problems whenever I use my triceps, like pushing the lawn mower, opening doors or pushing up from the recliner. It’s making my thumb and pointer finger very weak. An ultrasound didn't show any nerve compression. If compression happens only when I flex the muscle, does that mean it won’t show on a diagnostic workup?

Dear Reader: The radial nerve weaves its way from just below the armpit, through the elbow joint and down the length of the forearm. It animates the triceps, the muscle group at the back of the upper arm that engages during the pushing and pressing movements you have described. A branch of the radial nerve continues down through the wrist and into a portion of the hand. It controls extension and flexion of the wrist, the thumb, the index and middle fingers, and the inner half of the ring finger. It also provides sensation to the back of the hand and those fingers.

The meandering path of the radial nerve brings it close to bone, muscles and connective tissue, making it vulnerable to compression. This can occur from overuse, trauma, injury, repeated or sustained pressure, structural anomalies and inflammatory conditions, such as arthritis or diabetes. If the nerve is squeezed or trapped by the surrounding tissues, the pressure can interfere with its ability to function.

The weakness in your thumb and index finger are consistent with radial nerve compression. Additional symptoms can include a dull ache in the outer forearm, just below the elbow, and numbness, tingling or a burning sensation in the fingers the radial nerve serves. These may become worse at night. More severe compression can cause weakness in the wrist or fingers, and may make it difficult to grip objects, turn the palm upward or perform precision movement.

Diagnosis begins with a physical exam and a patient history, and may include imaging tests, including the ultrasound you underwent. This technique involves a device that emits high-frequency sound waves that scatter as they enter the body. As they encounter solid tissue, the sound waves bounce, each at a unique frequency based on the type of tissue encountered. On their return journey, the high-frequency waves are converted into electrical impulses, then processed by a computer and presented as visual images.

Because the weakness in your thumb and index finger occurs during movements that engage your triceps, a scan known as dynamic ultrasound can be a useful diagnostic tool. Unlike regular ultrasound, which creates static images, this form of the scan allows clinicians to view their patient’s skeletal structures in motion. This, along with significant advances in image quality, have made dynamic ultrasound an important diagnostic tool for musculoskeletal injuries and nerve impingement or compression.

If left untreated, the discomfort, weakness and limits to range of motion associated with radial nerve compression can worsen. If nerve damage occurs, they can even become permanent. We think it would be wise for you to ask your doctor about a dynamic ultrasound scan. If they are dismissive or resistant, don’t hesitate to seek a second opinion.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Hello, dear readers, and welcome to a bonus letters column. We’re thrilled to have an abundance of interesting mail. Let’s dive right in.

-- We recently wrote about the practice of microdosing GLP-1 drugs like Ozempic, which are used to manage Type 2 diabetes. For those who are not familiar, microdosing refers to the practice of using small amounts of a medication or substance to gain some of the benefits.

This led to a question from a reader: “Is it safe for me to microdose Ozempic if I want to lose 20lbs?” she asked. “I haven’t been able to lose the weight by conventional methods of diet and exercise.”

Because they mimic a naturally occurring hormone that regulates blood sugar and appetite, GLP-1 drugs are often used as an aid for weight loss. Due to possible side effects like nausea and diarrhea, microdosing GLP-1s has become popular. However, this is an off-label practice, and it is not yet clear whether using sub-clinical doses are either effective or safe.

These drugs are prescription-only, so you will need to see your doctor. You can then discuss your weight loss goal and ask whether they are willing to guide you through this process.

-- Several readers have asked us to make a clarification to a column about the Dirty Dozen of Produce. This is an annual list, compiled by the Environmental Working Group, that identifies the 12 vegetables and fruits most likely to be contaminated with pesticide residue.

“It is not correct that produce that is labeled organic isn’t grown with pesticides,” a reader from Los Angeles wrote. “You need to make that clear.”

It’s true that pesticides may be used in produce that bears the organic label. However, federal regulations require that they come from biological, botanical or mineral-based sources. The synthetic pesticides that are the focus of the Dirty Dozen list are not allowed.

That said, you should always thoroughly wash all produce, no matter the origin, before using.

-- A discussion of heat-related illnesses during heat waves, which are on the rise in our warming world, led a reader in Arizona to share a tip that comes from his grandmother.

“Anyone who has sat in front of a fan during a hot day knows that it won’t actually you cool off,” he wrote. “My grandmother used to bring out her ironing spray bottle and mist us kids with water. Then the breeze from the fan really did cool us off.”

Thank you for an easy, affordable and useful tip. Yes, the mist from the spray bottle creates a film of moisture that has an evaporative, and thus cooling, effect. This can be particularly helpful for older adults who, due to age-related changes, don’t produce as much sweat as younger people in warmer weather.

Thank you, as always, for taking the time to write. We love hearing from you. We will be back soon with the regular monthly letters column.

Meanwhile, if it occurs to you, please let us know where you are writing from. It’s so interesting to know where these columns are reaching you.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Kansas City, MO 64106; 816-581-7500

Dear Doctors: The more I read about microplastics, the more I want to do something to lower my family’s exposure to them. Any thoughts? Also, what is so much worse about microplastics than dust or pollen?

Dear Reader: For those who are not familiar, the term “microplastics” refers to tiny particles of plastic that range in size from smaller than a grain of sand to microscopic.

Some of these particles are added to a wide range of products to act as thickeners or exfoliants, or to add structure and texture. However, the majority enter the environment when products made with plastic undergo wear and tear.

It is estimated that between 10 and 40 metric tons of these miniscule pollutants are released into the environment each year. Researchers have found microplastics in fresh snowfall in Antarctica, in the cloud vapor around Mt. Everest and in the Mariana Trench -- the deepest region of the ocean we know. They have even been found in meconium, which is the first bowel movement of a newborn infant.

Unlike natural materials, plastics do not decompose or degrade. Instead, they split, break, shatter and then crumble into ever-smaller particles. These particles become small enough to be swallowed, inhaled or absorbed through the skin.

They are also able to penetrate cell membranes, enter the bloodstream and even cross the blood-brain barrier. This is due to their chemical properties and their minute size -- often mere nanometers -- which is far smaller than the dust and pollen you asked about.

The chemicals contained in microplastics have been shown to accumulate in bodily tissues. This can lead to bioactive effects, including causing inflammation, changing hormone interactions, altering immune response, disrupting the gut microbiome and causing physical damage. Microplastics also easily bond to heavy metals, endocrine disruptors and so-called forever chemicals, and they can carry them into the body.

To start reducing the microplastics around you, avoid single-use water bottles and food containers. They not only shed microplastics into their contents, but they also become a major source of environmental pollutants when discarded. Even to-go cups in coffee shops are lined with plastic, so bringing a non-plastic cup can reduce that exposure.

Many of us rely on plastic bags and wraps for food storage; however, these also transfer microplastics into their contents. And don’t use plastic wrap in the microwave as this causes chemicals to leach out.

You might consider investing in a good water filter, and in stainless steel or microwave-safe glass containers for food storage. Speaking of food, you’ll find fewer microplastics in fresh and unprocessed foods, and in those that sit lower on the food chain.

Even our clothes -- many of which contain synthetic fabrics -- shed microplastics when we wear them and when we wash them. Opt for natural fabrics when shopping, like cotton, linen and wool.

The United States Environmental Protection Agency is a good resource for guidance about products that are free of microplastics, at www.epa.gov/saferchoice. And remember, as with any change, it’s easiest to undertake in increments.

If any readers have suggestions, let us know. We would love to hear and to share them.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)