The list of symptoms that can strike long COVID sufferers has just gotten a little longer, and a little more mysterious: Researchers are reporting a case of "face blindness" related to the syndrome.
The condition, known medically as prosopagnosia, causes a very specific impairment: trouble discerning one face from another. Even the once-familiar face of a loved one might as well be a stranger's.
Typically, face blindness arises from damage to the brain's face-processing network, after a head injury or stroke, for example, said Marie-Luise Kieseler, a researcher at the Dartmouth College Social Perception Lab in Hanover, N.H.
Now she and colleague Brad Duchaine have identified the first case of face blindness linked to long-haul COVID.
Reporting in the journal Cortex, they describe the case of Annie, a 28-year-old who contracted COVID in March 2020. She had a fairly rough time, hit by a high fever, shortness of breath, diarrhea and coughing spells that were so bad at times that she fainted from lack of oxygen.
After three weeks, Annie finally felt well enough to go back to work (from home). But several weeks later, she began to notice feelings of disorientation, and that "something was off" with her ability to perceive faces.
Things came to a head when, in June 2020, she met her family for dinner for the first time since falling ill. On arriving at the restaurant, she walked right past them because she didn't recognize them.
Annie said that when her father called out, she turned to the familiar voice, only to see a face she didn't know.
As Annie described it: "It was as if my dad's voice came out of a stranger's face."
Eventually, Annie was evaluated by the Dartmouth team, who had her perform a series of standard tests to get to the bottom of things.
It turned out that Annie performed well to "flawlessly" on certain tests, including ones that asked her to learn and remember images of cars and landscapes, as well as voice recordings. Where she ran into trouble was face recognition.
One test, for example, presents people with images of six male faces to commit to memory. They then have to discriminate those learned faces from images of unfamiliar ones. On average, test-takers get it right about 80% of the time. Annie, however, was correct 56% of the time.
It all pointed to a particular deficit in face memory processing, Kieseler said.
Faces were not Annie's only challenge, however. She also had difficulty navigating once-familiar places, too -- becoming confused at the grocery store and having no idea where she parked her car, for example. (She's now reliant the Google map pin function to keep track of her car.)
Navigation problems, Kieseler said, are known to commonly co-occur with face blindness -- probably because certain brain areas critical to processing faces and "scenes" are close together. (Annie's navigation issues do not seem to be visual, researchers said. Instead, it seems to be an issue of accessing her "cognitive map" -- which helps people figure out where another place is, relative to where they are.)
Dr. William Schaffner is a professor at Vanderbilt University Medical Center in Nashville, Tenn., and a spokesman for the Infectious Diseases Society of America.
He said the case adds to the list of neurological symptoms known to plague many people with long COVID -- ranging from loss of taste and smell, to problems with memory and attention, to chronic pain.
One of the big questions, though, is why a respiratory infection becomes a persistent neurological issue for some people -- including young people who had mild bouts of COVID.
Broadly speaking, many researchers believe it's related to an aberrant activation of the immune system. For reasons that are unclear, Schaffner said, "there seems to be a chronic, smoldering inflammatory response" that persists long after the initial infection.
Regarding face blindness, it's not clear how common (or rare) it might be. The Dartmouth researchers conducted a survey of 86 people who had contracted COVID -- 32 of whom had fully recovered, and 54 who'd had long COVID symptoms for at least 12 weeks.
No one in the long COVID group reported symptoms of face blindness, Kieseler said. But navigation problems were common: one-third said they sometimes got lost when traveling, and almost half said once-familiar streets now seemed foreign. Few said they had those issues pre-COVID.
"This really can interfere with daily life," Kieseler said. "If you're getting lost on the way to the grocery store, that's a big problem."
Another looming question: How often do such neurological issues improve or resolve?
Face blindness, Kieseler said, has no cure at present. Instead, people learn to compensate. Annie, for example, relies on voices to identify people she knows.
According to Schaffner, some other neurological manifestations of long COVID, like loss of taste and smell, often seem to get better. He recommended that people with lingering symptoms in the weeks to months after a COVID infection talk to their primary care doctor.
Those with more severe symptoms, like debilitating fatigue and persistent memory and thinking problems, may be able to access a long COVID clinic -- which many larger U.S. medical centers now have, Schaffner said.
Kieseler said that people who think they have face blindness, or other perception impairments, related to long COVID are welcome to contact the research team through their website faceblind.org.
Dartmouth College has more on prosopagnosia, or face blindness.
SOURCES: Marie-Luise Kieseler, MSc, PhD student, psychological and brain sciences, member, Social Perception Lab, Dartmouth College, Hanover, N.H.; William Schaffner, MD, professor, medicine and preventive medicine, Vanderbilt University Medical Center, Nashville, Tenn.; Cortex, March 9, 2023, online