Peripheral neuropathy

I’m writing about peripheral neuropathy because several of my friends have this condition, one in which nerves outside the brain and spinal cord are damaged. It causes their feet and lower legs to be numb, and, as a result, has curtailed their ability to drive, among other things. (If you have no sensation in your feet, you can’t feel the brake and gas pedals.) The condition may also include weakness and lack of awareness of your body’s position in space (proprioception), which leads to an increased risk of falling.  

Typically, peripheral neuropathy starts in the toes and may slowly progress toward the knees. Sometimes it’s also in the hands. You’re most likely to develop peripheral neuropathy as you age. It’s most common in 70- and 80-year-olds.

According to the Journal of the American Medical Association, “more than 200 causes of peripheral neuropathy exist” [!]. Most common is diabetes. (My friends are not diabetic.)  Chronic hyperglycemia (high blood sugar) damages peripheral nerves. About 50 percent of people who have diabetes develop peripheral neuropathy over time. With diabetics, the lack of sensation leads to unrecognized injuries such as cuts and burns which, because of insufficient wound healing, can ulcerate, become infected, and require amputation.

Other causes of peripheral neuropathy include chemotherapy (the cause for one of my friend’s neuropathy); nutritional imbalances, such as vitamin B12 and vitamin B1 (thiamine) deficiency; excessive alcohol use; heredity; and autoimmune conditions.

Damage to peripheral nerves cannot be completely reversed and symptoms almost always persist.

It occurs to me that I have peripheral neuropathy. Some of my fingertips are numb. In my case, the cause was compression of the medial nerves in my wrists (carpal tunnel syndrome). I’ve had the surgeries, but, so far, the numbness persists. Nevertheless, I can still type.

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The good and bad of your immune system

Your immune system must be balanced to work properly. If it’s too sluggish, it can’t fight invading microbes, such as bacteria and viruses. If it’s overly aggressive, it can attack the body’s own cells, giving rise to autoimmune diseases such as rheumatoid arthritis, as well as type 1 diabetes and cancer.

For more than twenty years, Shimon Sakaguchi had been trying to understand how our immune systems stay in balance and why they sometimes don’t. This year he won the Nobel Prize in Physiology or Medicine for discovering “how we keep our immune system under control so we can fight all imaginable microbes and still avoid autoimmune disease” in the words of the Nobel committee. (Immunologists Mary E. Brunkow and Fred Ramsdell shared the prize.)

What Sakaguchi finally discovered was an elusive type of T cell—which he called regulatory T cell (or Treg) that prevents the immune system from overacting and causing harm. (T cells are a type of white blood cell that helps protect the body from infection and cancer.) The newly discovered Treg cells act as “peacekeepers” to stop the immune system from entering self-destruct mode—aka autoimmunity. The scientists also discovered a gene called FOXP3 which is required for the formation of Treg cells. (Humans who lack this gene develop a rare—and deadly—disease called IPEX.)

Because of these discoveries, potential new treatments are currently being developed to either suppress overactive immune responses or enhance the immune response. More than 200 clinical trials on such therapies are now in the works. Good news.

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How air pollution affects your brain

Scientists at the University of Pennsylvania have been studying the effects of pollution on brains for more than twenty years. Among other things, they perform autopsies on the brains of people with dementia. What they learned was that people who had been exposed to air pollution were more likely to have Alzheimer’s disease than those who did not. As Dr. Edward Lee, who directs the brain bank, concludes, “The quality of the air you live in affects your cognition.”

For example, an 83-year-old man who died with dementia had lived near a freeway. At autopsy, his brain showed large amounts of the plaques and tangles associated with Alzheimer’s disease. In contrast, an 84-year-old woman, who died of brain cancer, lived in an area surrounded by woods. As one of the researchers attested, her brain autopsy showed that she had “barely any Alzheimer’s pathology. We had tested her year after year and she had no cognitive issues at all.”

Because of their different home locations, the amount of air pollution that the woman was exposed to was less than half that of the man’s exposure. Increasing evidence is showing that chronic exposure to fine particulate matter—called PM2.5 (it has a diameter of 2.5 micrometers or less)—is likely associated with dementia. It’s a neurotoxin that can be inhaled deeply into the lungs. It not only affects brains, but it also damages lungs and hearts.

Sources of PM2.5 include vehicle emissions, industrial activities, wildfires, and household activities, such as cooking and burning candles. 

We’ve been cooking with our gas (propane) stove for decades. No wonder I’m having memory problems! All this time I’d been thinking it was just old age.

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Your hair can reveal your body’s secrets

The New York Times article from which I got this information says, “hair sits at the boundary between biology and identity.” Also: It serves as a “sensor for your brain and an archive of your body’s secrets.” Goodness! Really?  Here’s the explanation:

Hair is made mostly of keratin, a tough protein also found in your nails. You have about 100,000 hair follicles on your scalp and many more across your body. Each follicle cranks out the strands as well as the pigment that gives it color. Bacteria, viruses and fungi live within the follicles—a microbiome that keeps out harmful germs, reduces the risk of infections, and helps your hair grow. Your hair follicles also help heal wounds by sending stem cells to the wound where they create new skin cells.

As for your brain, your hair acts like motion detectors. Because the follicles are wrapped in nerve endings that fire at the slightest touch, if an insect drifts near your eyes, for example, your lashes sense it and you blink. The nerves also feed into your brain’s emotion centers, which is why a gentle caress can feel pleasant. In addition, hair follicles contain smell and bitter-taste receptors that influence hair growth. Some research indicates that certain fragrances seem to stimulate hair growth while others might inhibit it. Like your brain, the follicles also have an internal clock with a resting and shedding cycle. (Hair grows faster in the morning than in the evening.)

As the second-fastest growing tissue in the body—after bone marrow—hair serves as an archive of your health, signaling when something’s wrong. Follicles suck up toxic compounds and deposit them in your dead hair shaft. A centimeter of your hair captures a month’s worth of biological data: drug use, poisons, chronic stress, and even medication adherence.

Because keeping the pace of growth takes a lot of energy, rapid hair loss can serve as a sign of illness or stress. Of course, some hair shedding is inevitable—we lose about 50 to 100 strands of hair each day.

The article didn’t explain what happens when you lose a lot of hair in old age. Inquiring minds want to know!

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What your tongue tells you

Traditional Chinese medicine includes studying the tongue to detect illness. A healthy tongue appears pink with a thin white film. Not-so-healthy tongues may look white (lack of iron), bluish yellow (diabetes), purple (certain cancers), and so forth. Now, some researchers are working to adapt this diagnostic method by using AI technology. 

Because color perception is very subjective and varying light conditions can affect color perception and analysis, researchers created a kiosk with a standardized lighting system. Patients would put their heads in the kiosk where images of their tongues could be collected.

Next, they trained an AI program to detect illnesses by showing it 5,260 images of healthy and unhealthy tongues, after which it was able to classify and predict conditions such as diabetes, asthma, COVID, and anemia, with 96.6 percent accuracy. After this training, the researchers tested it with 60 tongue images they’d collected with their kiosk at two hospitals. AI correctly identified patients’ conditions—based on their medical records—in 58 out of 60 images.

According to the article in Scientific American, researchers at the University of Missouri have launched an AI application, called BenCao, where users can upload tongue images and receive personalized health guidance. The app is designed and marketed as a “wellness” tool.

As you can imagine, the scientific community is wary about studying the tongue to assess a patient’s health. On the other hand, tongue examination is often part of a routine screening for oral cancer by dentists and hygienists.

I’m guessing you’ll soon be sticking out your tongue in front of a mirror.

For an introduction to this blog, see I Just Say No; for a list of blog topics, click the Topics tab.