A 58-year-old woman with COVID-19 developed encephalitis, resulting in tissue damage in the brain (arrows)N. Poyiadji et al., Radiology, (2020) doi.org/10.1148/radiol.2020201187
Another striking set of symptoms in COVID-19 patients centers on the brain and central nervous system. Frontera says neurologists are needed to assess 5% to 10% of coronavirus patients at her hospital. But she says that “is probably a gross underestimate” of the number whose brains are struggling, especially because many are sedated and on ventilators.
Frontera has seen patients with the brain inflammation encephalitis, with seizures, and with a “sympathetic storm,” a hyperreaction of the sympathetic nervous system that causes seizurelike symptoms and is most common after a traumatic brain injury. Some people with COVID-19 briefly lose consciousness. Others have strokes. Many report losing their sense of smell. And Frontera and others wonder whether in some cases, infection depresses the brain stem reflex that senses oxygen starvation. This is another explanation for anecdotal observations that some patients aren’t gasping for air, despite dangerously low blood oxygen levels.
ACE2 receptors are present in the neural cortex and brain stem, says Robert Stevens, an intensive care physician at Johns Hopkins Medicine. But it’s not known under what circumstances the virus penetrates the brain and interacts with these receptors. That said, the coronavirus behind the 2003 severe acute respiratory syndrome (SARS) epidemic—a close cousin of today’s culprit—could infiltrate neurons and sometimes caused encephalitis. On 3 April, a case study in the International Journal of Infectious Diseases, from a team in Japan, reported traces of new coronavirus in the cerebrospinal fluid of a COVID-19 patient who developed meningitis and encephalitis, suggesting it, too, can penetrate the central nervous system.
But other factors could be damaging the brain. For example, a cytokine storm could cause brain swelling, and the blood’s exaggerated tendency to clot could trigger strokes. The challenge now is to shift from conjecture to confidence, at a time when staff are focused on saving lives, and even neurologic assessments like inducing the gag reflex or transporting patients for brain scans risk spreading the virus.
Last month, Sherry Chou, a neurologist at the University of Pittsburgh Medical Center, began to organize a worldwide consortium that now includes 50 centers to draw neurological data from care patients already receive. The early goals are simple: Identify the prevalence of neurologic complications in hospitalized patients and document how they fare. Longer term, Chou and her colleagues hope to gather scans, lab tests, and other data to better understand the virus’ impact on the nervous system, including the brain.
Chou speculates about a possible invasion route: through the nose, then upward and through the olfactory bulb—explaining reports of a loss of smell—which connects to the brain. “It’s a nice sounding theory,” she says. “We really have to go and prove that.”
Most neurological symptoms “are reported from colleague to colleague by word of mouth,” Chou adds. “I don’t think anybody, and certainly not me, can say we’re experts.
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