How does this happen? Research suggests that the coronavirus can directly infect neural cells, said Dr. Jeffrey Cirillo, a professor of microbial pathogenesis and immunology at Texas A&M University. The virus most likely replicates inside the cells and affects how they function. This viral invasion could cause patients to “have a persistence of cognitive problems, or maybe they will have persistent seizures,” Dr. Koralnik said. In April, a 40-year-old Los Angeles woman with a headache, seizures and hallucinations was found to have the RNA from the coronavirus in her cerebrospinal fluid.
Another way the coronavirus can damage the nervous system is indirectly, through widespread inflammation caused by the body’s immune response. Inflammation “is bad for the brain, and we know that for a fact,” Dr. Fotuhi said. One of the leading theories in Alzheimer’s research is that inflammation drives the disease.
Brain inflammation can also spark the creation of blood clots. Studies suggest that clots occur in up to 30 percent of critically ill Covid patients. These clots can permeate the brain, causing it “to function at a lower level,” Dr. Fotuhi said. They can also lead to strokes that starve the brain of oxygen. Studies from China and Italy have suggested that as many as 5 percent of hospitalized patients with Covid experience strokes, though a more recent N.Y.U. study found the figure to be lower, at 1 percent, in hospitalized New York patients.
If the inflammation becomes so severe as to involve a “cytokine storm,” in which a patient’s body in effect turns on itself, the blood brain barrier can be breached, allowing more viruses and cytokines into the brain and ultimately killing brain cells. “It’s like the defense system is called to quiet a small riot in one neighborhood, and all of a sudden, the whole military is ticked off and they don’t know what’s going on, they just go bomb everything,” Dr. Fotuhi said.
A small number of patients with the coronavirus have gone on to develop Guillain-Barré syndrome, in which a person’s immune system attacks their own nerves, causing paralysis. Michele Hart, a 41-year-old psychotherapist in Colorado, is one of them.
She began experiencing electrical, shocklike pains in her body, numbness in her extremities and stabbing pains down the side of her face in April. She went to the E.R., worried she might have the coronavirus, but they sent her home, saying her neurological symptoms weren’t consistent with the infection. When her blood pressure skyrocketed a few days later, she returned to the ER and this time was given a coronavirus test that came back positive. She was also diagnosed with Guillain-Barré syndrome.
In addition to persistent memory problems and dizziness, she still struggles with nerve pain. “I have pins and needles and shooting nerve pain constantly, as well as burning sensations in my skin,” she told me.