AURORA, Ill. — There is sobering evidence of Samantha Lewis’s struggle with long Covid on her bathroom mirror.Above the sink, she has posted a neon pink index card scrawled with nine steps (4. Wet brush 5. Toothpaste) reminding her how to brush and floss her teeth. It is one of many strategies Ms. Lewis, 34, has learned from “cognitive rehab,” an intensive therapy program for Covid-19 survivors whose lives have been upended by problems like brain fog, memory lapses, dizziness and debilitating fatigue.Nearly two years into the pandemic, advances have been made in treating Covid itself, but long Covid — a constellation of lingering health problems that some patients experience — remains little understood. Post-Covid clinics around the country are trying different approaches to help patients desperate for answers, but there is little data on outcomes so far, and doctors say it is too soon to know what might work, and for which patients.While some physical symptoms of long Covid, like shortness of breath or nausea, can be addressed with medication, cognitive issues are more challenging. Few drugs exist, and while some deficits can rebound with time, they can also be exacerbated by resuming activities too soon or intensively.Among items in the bathroom, Ms. Lewis keeps an index card reminding her how to brush her teeth and floss.Over several months, The New York Times visited Ms. Lewis, interviewed her doctors, attended her therapy sessions and read her medical records. Before she was infected with the coronavirus in October 2020, experiencing a modest initial illness that did not require hospitalization, she was successfully juggling a demanding, detail-oriented job while raising a child with autism and attention deficit hyperactivity disorder. But this summer, she scored 25 on a 30-point assessment, placing her in a pre-dementia category called mild cognitive impairment.“I can feel that things are off,” she told a neurologist at Northwestern Memorial Hospital’s Neuro Covid-19 Clinic in Chicago who evaluated her and recommended cognitive rehab. “I approach a red light, my brain knows that it’s red, but it’s not reacting to the rest of my body to put my foot on the brake. Do you understand how terrifying that is?”In July, she began throwing herself into several sessions a week at Shirley Ryan AbilityLab, a rehabilitation center that for years has helped patients with brain injuries, strokes and other conditions. It has so far treated about 600 Covid survivors. There, an occupational therapist, physical therapist and speech-language pathologist gave Ms. Lewis exercises to strengthen her memory, concentration, balance and endurance.At home, 40 miles west of Chicago, Ms. Lewis practices the memory and attention exercises with playing cards and a color-coded planner, and the balance exercises using a Post-it marked with an “X” affixed to her wall. Smart speakers throughout the tri-level townhouse broadcast reminders like, “Samantha, it is time to take a break for lunch” and “Get your butt ready for bed.”“These are things she legitimately needs,” Dr. Ashley Stoecker, her primary care physician, said.Ms. Lewis’s slowed reaction time during her struggle with long Covid kept her from driving on highways, and she once asked her 11-year-old daughter to monitor the rearview mirror so she could focus on the road.‘I feel so stupid’Studies estimate that 10 to 30 percent of coronavirus patients may develop long-term symptoms and post-Covid clinics are beginning to characterize the experience.One year after infection, 63 percent of 156 patients at Mount Sinai Health System’s post-Covid program reported cognitive problems like trouble with short-term memory and planning. Most reported ongoing brain fog, dizziness, headaches or fatigue, and many reported labored breathing or palpitations. Nearly half of 102 patients had stopped working full time.Of more than 1,000 patients from around the country evaluated by Northwestern’s neuro-Covid clinic, many were previously multitaskers with busy jobs, said Dr. Igor Koralnik, who heads the clinic and is Northwestern’s chief of neuro-infectious diseases and global neurology. In a report about the clinic’s first 100 patients, the average age was 43.“I was a little bit surprised with how young and functional our population was initially,” Dr. Joshua Cahan, a cognitive neurologist at Northwestern, said. But, he added, the cognitive symptoms have proved especially “noticeable to people who are having demanding lives.”Long Covid has affected everything for Ms. Lewis. Her slowed reaction time prevented her from driving on highways. She has occasionally pulled over to vomit from motion sickness and once asked her 11-year-old daughter, Mariah, to monitor the rearview mirror so she could focus on the road.Before Covid, Ms. Lewis was an avid roller skater with the roller derby nickname “Savage Siren”; after Covid, her balance became so unsteady, she used a walker and then a cane.Once an an avid roller skater, Ms. Lewis, left, shopping with her daughter, Mariah, has had to use a cane to help with her post-Covid balance issues.“She was so active before,” said Dr. Stoecker, who has witnessed lapses like the time Ms. Lewis left her wallet in Dr. Stoecker’s office.She had to sharply reduce her hours in her job as a director with an agency operating group homes and programs for adults with developmental disabilities and sometimes made mistakes like assigning three employees the same task.“My whole field is developmental disabilities,” Ms. Lewis said. “You hate to be the person that’s like, ‘I need something too.’”Especially difficult is feeling less able to support Mariah. “I’m her person,” Ms. Lewis said, lamenting that ringing and buzzing in her ears makes sounds so painful she sometimes has to ask Mariah, who loves to talk, to be quiet.“My cognitive stuff is a little broken,” she told Mariah. “We’re both in repair.”Mariah replied: “That’s hard because you’re not supposed to be broken.”In September, she drove Mariah to autism therapy on the wrong day.“I feel so stupid,” Ms. Lewis exclaimed.“You’re not stupid, Mom,” Mariah said. “Your brain’s just hurt a little bit and it will get better.”Beginning therapyA cognitive rehab exercise with Melissa Purvis, right, a speech-language pathologist at Shirley Ryan AbilityLab in Burr Ridge.“Repeat this sentence: ‘The restaurant is on the top floor of the Bank of America building on 12th,’” Melissa Purvis, a speech-language pathologist, instructed Ms. Lewis in late July, soon after she started cognitive rehab.“The restaurant is on the 12th floor of the Bank of America building,” Ms. Lewis said.Ms. Purvis asked her to repeat six numbers: 4, 7, 1, 9, 2, 6.“4, 7, 2, 5, 6,” Ms. Lewis replied.She took overly long to complete a maze. “The lines all started to blur together,” she said.Out of 10 tests, Ms. Purvis reported, “There were five different areas in here where you’re definitely working below where you should be.”Ms. Lewis’s fiancé at the time, James Moylan (they recently married), was skeptical initially. “Are we in kindergarten? Is this the best they can come up with?” he said.“But now,” he added, “it makes sense.”Medication and supplements that Ms. Lewis takes to try to address some of her post-Covid symptoms. What causes post-Covid neurological symptoms is unclear. Theories include inflammation and overactive immune responses. Brain scans and other tests frequently show nothing amiss.“Oftentimes, doctors will have told them, ‘You look fine, this is made up in your head, forget about it,’” said Dr. Elliot Roth, an attending physician at the AbilityLab’s Brain Innovation Center and chairman of physical medicine and rehabilitation at Northwestern.Some scientists think specific factors could predispose people to long-term symptoms. Forty-two percent of the Northwestern clinic’s first 100 patients previously had depression or anxiety, though such patients might simply be more comfortable seeking neurological treatment, doctors said. Other pre-existing conditions included autoimmune diseases and headaches.Ms. Lewis experienced depression as a teenager, was briefly diagnosed with bipolar disorder in college and has since been intermittently treated for depression and anxiety, although she wasn’t taking psychiatric medication before Covid and hasn’t needed it since, she and Dr. Stoecker said.Her few pre-Covid medications, she said, were for tension headaches and hypothyroidism. Her history also included occasional asthma and possibly an underlying autoimmune condition, psoriatic arthritis, which was diagnosed after Covid, Dr. Stoecker said.Searching for helpPreparing dinner at home in Aurora, Ill., with Mariah. “I’m her person,” Ms. Lewis said.Two weeks after testing positive and isolating at home, Ms. Lewis tried returning to work, but lasted only two hours. A scan of her lungs found haziness and constricted airways.One month post-infection, she had to nap by noon every day and was so dizzy that things spun when she stood or walked. Once, she fainted while putting away groceries, hitting her head on the microwave and kitchen counter. Mariah said she asked, “Are you OK?” three times, becoming tearful, before Ms. Lewis opened her eyes.Two days later, a hospital found no brain injury, she said, but a doctor there suggested she see several specialists, saying her symptoms resembled those of some of his hospital’s nurses who had struggled with long Covid for months.Soon after, a pulmonologist mentioned Northwestern’s clinic and Ms. Lewis scheduled the first available appointment, in late March. While waiting, she visited a local neurologist who suggested she just “try harder,” she said.A cardiologist detected rapid heart rate. She was diagnosed with a type of dysautonomia called POTS, which can involve dizziness. She saw a gastroenterologist for diarrhea and nausea, and a rheumatologist for arthritis-related knee problems. But neurological problems agonized her the most. Accustomed to cooking meals from scratch, including lunches for co-workers, she couldn’t follow recipes. “I was the person that fed everyone and now I struggle to figure out what I can feed myself,” she said.She forgot to pay several bills and couldn’t remember why she had entered a room.One of several pink cards with reminders that Ms. Lewis has posted in her home.Such lapses were “really, really strange” for someone typically so responsible she seemed to do “the job of 12 people,” Mr. Moylan said. “It was almost like she was drunk.”When her neuro-Covid clinic appointment came, “it was very relieving to finally feel validated,” Ms. Lewis said. Dr. Koralnik prescribed a medication for fatigue, amantadine, which she finds helpful, calling it “zoom-zoom pills.”On the cognitive assessment he administered, she scored “significantly lower than average” in processing speed, attention and executive function, he said, and barely average in the remaining category, working memory.The results were “crushing,” she said.Dr. Cahan, then on leave, did an in-depth follow-up when he returned in June.On those tests, Ms. Lewis said, she called a camel a “desert llama” and when asked to count backward from 100 by seven, “I say 93 and I’m just stuck.”The Coronavirus Pandemic: Key Things to KnowCard 1 of 5The Omicron variant.