Neurological symptoms are extremely common among COVID-19 patients sick enough to be hospitalized, a study published Monday finds.
The symptoms range from mild to severe, and can include headaches, dizziness and altered brain function, according to the study in the journal Annals of Clinical and Translational Neurology.
The findings highlight the wide-ranging effects the virus can have on the body. What's more, the study found that patients may continue to experience these symptoms long after they recover from the disease.
The news comes on the same day President Donald Trump left Walter Reed National Military Medical Center after being hospitalized for three days. His physicians have made no indication that the president has experienced any major neurological symptoms.
In the study, researchers at Northwestern Medicine looked back at the first 509 patients hospitalized within their network of 10 hospitals and medical centers in Chicago in March and April. Just over a quarter had been put on ventilators.
A majority of 509 patients — 82 percent — developed problems stemming from the nervous system. "That means 4 out of 5 hospitalized patients in our hospital system at the beginning of the pandemic had those neurologic problems," said Dr. Igor Koralnik, a co-author of the study and chief of neuro-infectious diseases and global neurology at Northwestern Medicine.
Muscle pain was reported by nearly 44.8 percent of patients, and 37.7 percent complained of headaches.
Just under a third of patients developed a more serious type of neurological problem: encephalopathy, or altered brain function.
Problems ranged from mild symptoms, such as difficulty with attention, short-term memory, concentration and multitasking abilities, "all the way to confusion, stupor and coma," Koralnik said. More severe brain function issues were more likely to occur in older patients over 65.
Others reported feeling dizzy, or lost their sense of taste or smell.
"This confirms that neurological manifestations are common, but often mild. That is important," Dr. Alejandro Rabinstein, a neurologist at the Mayo Clinic, said. "Many patients in the hospital with COVID will have muscle aches, will have loss of smell and taste. Those are reversible, and benign," Rabinstein was not involved with the new study.
It appears the symptoms were not a result of being hospitalized, which can occur after patients are treated in intensive care units, but rather the virus itself. Forty-two percent of the patients in the study had neurological problems when they first got sick.
Indeed, Koralnik said such problems could be the first signs of a coronavirus infection. People who all of a sudden cannot smell, without explanation, "should consider that as a sign of early COVID-19."
"They should be tested more rapidly and quarantine and trace their contacts to prevent further spread" of the virus," he added.
Future studies of hospitalized COVID-19 patients may reveal different impacts on the nervous system. This research focused on patients admitted to the hospital at the beginning of the pandemic, usually in dedicated COVID-19 wards without wide access to brain imaging. What's more, fewer than 6 percent of the patients in this study were seen by neurologists or neurosurgeons.
"Only nine months into the pandemic," the study authors wrote, "the long‐term effects of COVID‐19 on the nervous system remain uncertain."
Also unknown are the long-term effects of these symptoms. Koralnik and his colleagues will continue to follow patients after they get out of the hospital, including so-called long-haulers, who continue to experience symptoms, such as fever, fatigue and brain fog, months after recovering from the virus.
"It is important that people realize the magnitude of these problems," Koralnik, who also oversees the Northwestern Medicine Neuro COVID-19 research group, said. "We need to continue to do more research to try to find out why this is happening, especially the brain fog."
This article was originally published on NBCNews.com.