To get a handle on questions like this, the neuroscientist Owen is working with University of Toronto researchers to survey 50,000 coronavirus patients with lingering neurological symptoms to determine who might be most at risk and what the long-term effects are.

They’re using a series of self-reported questionnaires and brain games done online. Other studies, looking at symptoms more broadly in fewer people and with more detail, are just beginning elsewhere as well.

Many patients have been sharing their experiences in a Facebook group called “Survivor Corps” that today counts more than 96,000 members.

Diana Berrent founded the group after contracting Covid-19 in March. Since then, she’s partnered with Lambert to survey its members. The symptom list they gathered was pages long, including difficulty concentrating or focusing, anxiety, memory problems, heart palpitations, blurry vision and neuropathy in feet and hands.

With researchers just starting to study Covid-19’s long-term consequences, reliable numbers are hard to come by. A recent federal study found that about 35% of people who tested positive for Covid-19 were still experiencing symptoms two to three weeks later, including many young adults.

While patients 50 and older had the highest risk of long-lasting problems, more than a quarter of those under age 35 had continuing symptoms, including many who had no previous health problems.

Italian Study
Meanwhile, a survey of 143 patients who had been hospitalized for Covid-19 in Italy found that two months later only 12.6% were completely symptom-free, and more than half said they still had three or more ongoing symptoms.

There’s no doubt that coronavirus infection can cause nerve complications. One early study from Wuhan, China, found that 36% of patients had neurologic symptoms ranging from headache to impaired consciousness.

Since then, researchers have reported a variety of strange neurologic syndromes, ranging from Miller Fisher syndrome, a nerve disease that can paralyze eye muscles, to acute disseminated encephalomyelitis, a nerve-lining inflammation that can resemble multiple sclerosis flareups, to autoimmune encephalitis, and inflammation of the brain’s temporal lobes, which can cause confusion and hallucinations.

But with case reports just emerging, it’s been hard to prove cause and effect.

Even when people clear the virus and test negative, they “can feel out of sorts for weeks and weeks,” almost similar to chronic fatigue syndrome, said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, during a Facebook live interview on July 16th. But it may take a year or more to understand whether the virus produces truly long-lasting complications, he said.

There are logical reasons why people who were hospitalized could have residual neurologic effects lasting for months. These patients may have been so sick that organ failure limited oxygen flow to the brain, said Igor Koralnik, who is chief of neuro-infectious disease at Northwestern Medicine and leads its neurology-focused Covid clinic. Blood clots in the brain or widespread inflammation could also impact brain function, he said.