Dear Doctor: I tripped while I was out running a few months ago and got pretty banged up, including a knock to the head. My wife worried about a concussion and wanted me to see a doctor. How do you know if you have a concussion?

Dear Reader: A concussion is a type of brain injury that can occur when a force is powerful enough to cause the head, along with the brain inside of it, to shake quickly back and forth. This can result from the type of direct impact you experienced when you fell during your run. It may also be caused by an indirect force that’s powerful enough to make the head whip back and forth, as can happen during a tackle or when you’re rear-ended in your car at high speed.

Your brain is basically a passenger within your skull. When something causes your head to stop short or suddenly change direction, your brain continues moving. It bounces and twists and bumps into the interior surfaces of the skull. A concussion results in a chemical change within the brain, along with bruises, tears or injury to the soft and fragile tissues. Because it’s not life-threatening, concussion is typically referred to as a mild traumatic brain injury, or TBI. However, the effects can be serious.

When you have a concussion, symptoms may show up right away, or they can develop over a period of hours or days. Immediately after a concussion, a person may appear dazed or bewildered. They may not immediately be aware of what happened, and it’s possible they won’t recall the moments leading up to the injury. Some people become clumsy, and they may have trouble understanding and following directions. Physical symptoms can include headache, feeling nauseated, vomiting, a feeling of pressure within the skull, blurred or double vision, ringing in the ears and problems with balance and coordination. Some people may develop a sensitivity to external stimuli, including light and sound. The person may report feeling slow or groggy or just generally not OK. A brief loss of consciousness immediately after impact is possible.

Someone with a suspected concussion should seek medical care. You’ll be asked for details about the accident, as well as any symptoms. It’s important to also share information about any medications and supplements, as some can increase risk of bleeding. Diagnosis includes a neurological exam that checks vision, hearing, strength, balance and coordination. Cognitive tests are used to evaluate memory, recall and concentration. It’s possible that someone would be asked to stay overnight in a hospital for observation. In some cases, brain imaging tests may be considered.

In 2018, the U.S. Food and Drug Administration approved a blood test to evaluate concussion. It measures levels of two protein biomarkers that the brain releases into the blood within 12 hours of a head injury. It’s not a diagnostic test for concussion, but it does help predict which patients will have injuries that will be visible in a brain scan.

With 3.8 million reported concussions per year, this is a common injury. It’s also a potentially serious one. It’s important, so we’ll say it again: If you suspect a concussion, seek medical care.

(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.)

Hello again, dear readers, and welcome to part two of our monthly letters column. We received so many letters last month that we needed a bit of additional real estate to get to the most popular topics.

-- Regarding the novel coronavirus, we have had several questions about asymptomatic carriers. These are people who, although infected with the virus, have no symptoms of COVID-19, the illness that it causes. “Can you be infected with the virus and not be sick?” a reader asked. “If you don’t have symptoms, can you still get other people sick?” The answer to both questions is yes. Some people can become infected with the novel coronavirus and not experience any symptoms. However, because the virus is replicating within their bodies, they are able to unknowingly transmit it. That’s why, as we’ve discussed here before, it’s so important for us all to wear a facial covering while in public. The virus is broadcast via the tiny droplets of moisture we emit whenever we cough, sneeze, laugh and speak. By wearing a mask, a portion of those droplets are blocked, which protects the people around us.

-- Speaking of masks, a reader asked about whether a mask protects him as well as those around him. “If you’ve got your face covered, won’t that keep the virus away from you, even a little bit?” he asked. “I’m not a scientist, but it just seems like common sense.” The virus, along with the aerosols that carry it, are both so minute that it takes a specially formulated respirator mask to completely block them. These types of masks are in very short supply and are reserved solely for medical settings. Interestingly, a new study from the University of California, San Francisco suggests that tightly woven cloth face masks may -- and the key word here is “may” -- offer a small measure of protection to the wearer as well. Until there is more evidence, though, assume that your mask protects others but not yourself. Remain vigilant about social distancing and hand-washing.

-- A reader who walks her dog every day wonders if her pet puts her at risk. “I’m careful about what I touch, but my dog is ‘barefoot’ on the sidewalk and sniffs everything,” she wrote. “Can you get the coronavirus from your dog?” The Centers for Disease Control and Prevention has good news for you. And we quote: “Currently, there is no evidence that SARS-CoV-2 can spread to people from the skin or fur of companion animals.”

-- We offer a thank-you to a reader from California who wrote in regarding a recent column about lumbar spinal stenosis. It’s a narrowing of the spinal column in the lower back that results in compression of the nerves. We talked about a minimally invasive surgery that uses a small implanted device to act as a lift, and thus create additional space within the spinal column. Our reader pointed out that this type of surgery is known as "minimally invasive indirect decompression" rather than "minimally invasive lumbar decompression." We appreciate the correction.

Thank you again for all of your mail. We look forward to seeing you here soon for our regular letters column.

(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’m having trouble sleeping these days, and so is my wife. We’re both 33 years old, we’ve been working from home and we have two very active young sons. What can we do?

Dear Reader: Even before the novel coronavirus upended our lives, poor sleep and insomnia were already affecting millions of people of all ages in the United States. That’s a problem because adequate good-quality sleep is important to physical and mental health and to emotional well-being. People who regularly get fewer than seven hours of sleep per night are at increased risk of a range of health problems, including high blood pressure, heart disease, diabetes, obesity, inflammatory diseases, anxiety and depression. And that’s not even factoring in how lack of sleep affects performance and safety during our waking hours.

It helps to understand that sleep begins at the cellular level. Our bodies respond to the daily 24-hour cycle of light and dark in a number of complex ways. Artificial light disrupts this natural rhythm, as do a host of other factors. These include the blue light from screens, which has been shown to scramble our internal clocks, and substances such as caffeine, nicotine, alcohol, sugar and certain medications. Stress, anxiety and depression, which many of us have in abundance right now, also interfere with sleep. The good news is that there are steps you can take to improve your chances for a good night’s sleep.

Optimize your environment. Make your bedroom as dark and quiet as possible. Window coverings that completely block outside light are a worthwhile investment. Some people swear by a sleep mask. And don’t forget about interior lights, such as clock faces, televisions, and computer, phone and tablet screens. Even those dots of light from chargers and the smoke alarm are better covered up. If noise is a problem, consider ear plugs or a white noise machine. Do what you can to control the temperature. Research shows that people sleep best in a cool room, from 60 to 68 degrees. And we know it’s a challenge, but stop looking at screens a few hours before bedtime. It really makes a difference.

Set a sleep schedule. Be realistic. If you can, match it to your natural preferences for sleeping and waking. Known as chronotypes, these are ingrained sleep-wake cycles that contribute to whether you’re a morning person or a night owl. Include a transitional wind-down time, a personal ritual that signals to your body that the waking day is over. Read a book, do some stretches, give yourself a scalp massage.

Daily exercise can contribute to better sleep. So do meditation and yoga. Many people swear by slow, deep breathing as an effective transition from wakefulness to drowsiness and then sleep. As we mentioned earlier, caffeine and alcohol can interfere with both the quantity and quality of your sleep, so it’s important to stop intake later in the day. Your goal in all of this is consistency, including on weekends. And please be patient -- it can take a few weeks to begin to see results.

(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.)