Scientific American 1/21/21
“I realized that some of the words didn’t feel right in my mouth, you know?” he says. They felt jumbled, stuck inside. Thornton had suddenly developed a severe stutter for the first time in his life. “I got my voice back, but it broke my mouth,” he says. After relaying the story over several minutes, Thornton sighs heavily with exhaustion. The thought of going back to teaching with his stutter, “that was terrifying,” he says.
In November Thornton still struggled with low energy, chest pain and headaches. And “sometimes my heart rate [would] just decide that we’re being chased by a tiger out of nowhere,” he adds. His stutter only worsened by that time, Thornton says, and he worried that it reflected some more insidious condition in his brain, despite doctors’ insistence that the speech disruption was simply a product of stress.
A growing body of evidence warns that the legacy of the pandemic does not necessarily disappear when the novel coronavirus, or SARS-CoV-2, is cleared from the body. Among the millions of people who have survived respiratory complications from COVID-19, many still live with lingering symptoms in the wake of even a mild case of the disease. Neurological symptoms, ranging from fatigue to brain fog to loss of smell, persist after the virus is gone from the body.
An early survey of 153 COVID-19 patients in the U.K. and a more recent preprint study of people hospitalized with the disease in Italy both found that about a third had neurological symptoms of some kind. Other estimates have trended even higher. “There’s a really wide spectrum of [neurological] manifestations of COVID,” says Thomas Pollak, a neuropsychiatrist at King’s College London and a co-author of the U.K. study. “Some are totally devastating, like stroke or encephalitis, and some are much more subtle.” Increasingly common symptoms include fatigue and memory problems—and, at times, new cases of psychosis or mania.
Some neurological manifestations of post-COVID, such as stuttering, are more bizarre than others. But Houston’s Thornton is not the only one afflicted. Soo-Eun Chang, a neuroscientist at the University of Michigan, is among the few researchers investigating stutter. “While stress and anxiety are not the cause of stutter, they do exacerbate it,” Chang says, and that is true for Thornton. But she says the origins of the disorder lie in complex circuits of the brain that coordinate the millions of neuronal connections needed for human speech.
While most people develop this disruption of speech when they learn to talk, around age two, neurogenic stutter can arise after brain trauma, such as an injury. Chang says her colleagues in clinical practice have reported seeing an increase in cases of stuttering during the pandemic—mostly in people whose existing stutter worsened or whose childhood stutter returned.*
Having the virus, she says, could lead to conditions that disrupt speech. “Speech is one of the more complex movement behaviors that humans perform,” Chang says. “There are literally 100 muscles involved that have to coordinate on a millisecond time scale, so it’s a significant feat. And it depends on a well-functioning brain.” COVID’s inflammatory response could undermine the efficiency of these circuits. “An immune-mediated attack on synaptic connections could lead to a change in brain function,” she says.
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