man wearing face covering / Getty Images

Even Mild Cases Can Cause “COVID-19 Fog”

When COVID-19 patients started inundating New York City hospitals in March, Columbia neurologists were ready, thanks to some advanced preparation.

“When we saw what was happening in China and Italy, we figured we were next. We love New York because it is a dense, global hub, but that was also its Achilles heel,” says Anna Nordvig, MD, a neurologist and postdoctoral clinical and research fellow at Columbia University Vagelos College of Physicians and Surgeons who specializes in cognition and behavior. 

Nordvig quickly organized a group of Columbia neurologists to review what was known about the neurological effects of other coronaviruses to get an idea of what might be coming their way, while the Department of Neurology at VP&S and NewYork-Presbyterian Hospital overhauled itself to serve the expected influx of patients.

The review also alerted the neurologists to watch out for lingering neurological and psychiatric issues in all patients, including those whose symptoms were mild and never required medical attention.

CUIMC News spoke with Nordvig about the patients she is now seeing in the Memory Clinic in the Department of Neurology.

How common is it for COVID-19 patients to experience persistent neurological symptoms?

There are few more pressing questions that neurologists and psychiatrists worldwide must answer, but it may not be easy.

COVID-19 manifests with many different symptoms. Some may escape detection. It may be hard to distinguish what was caused by the virus and what was caused by the hospitalization. Patients may not even think to mention certain symptoms to their doctor. To understand the prevalence of persistent neurological symptoms, we need to cast a wide net. Patients and their primary doctors can help this effort.

Over the past two months in New York City, we’ve seen a trickle of patients who have symptoms that are more serious and persistent compared to, say, the typical brain fog after a sleepless night. Some of these patients are quite young, in their 30s.

We’re not seeing a deluge of patients, but I worry that the people we’re seeing are those most attuned to the latest developments about the disease. Some people may just be waiting for their symptoms to pass and not getting the help that could alleviate some of their issues.

Initially, we learned from our Chinese colleagues that, among patients who were hospitalized, about a third had acute neurological symptoms. The epicenters that were hit first—Asia, Europe, the U.S. coasts—are all following their patients for persistent symptoms, and we anticipate results soon. 

What kinds of symptoms are people having?

In our clinics and in case reports worldwide, patients report fatigue, inattention, poor concentration, difficulty working long hours, difficulty getting out of bed, a “brain fog.” This is similar to what small studies reported in survivors from the first SARS virus. Some also have more specific thinking and behavior problems—they forget the names of people they know well, they can’t follow along during business conversations, prioritizing and planning is suddenly difficult, they are inexplicably anxious and sleep poorly. 

Similar to the first SARS virus, patients are experiencing unusual sensory symptoms. Everyone has heard about the loss of smell and taste in COVID-19 and other viruses; we’re also seeing changes in appetite, lightheadedness, body discomfort, and new or worsened headaches that don’t always respond to traditional pain relievers.

These are young and middle-aged people who were previously thriving. Now they are having profound changes in the way they think and feel. They’re worried about their careers, if this persists. 

The good news is that most of the patients we’re seeing are getting better.

If someone suspects they’re having neurological effects after recovering from the infection, what should they do?

A gradual, significant change in the way you're thinking or in your mood is concerning and should be evaluated in an outpatient clinic. Telemedicine might be more accessible to some. 

The patient should keep a diary and present that diary of symptoms to their practitioner. In the diary, try to be clear when each symptom started, when and how often it is happening, how severe it is, and anything else you’re going through. Other conditions besides COVID-19 are still happening and it’s possible some other medical condition could explain the symptoms. 

Practitioners should pay attention to that initial intake form patients fill out before an appointment. If a lot of boxes are checked for things like fatigue, inattention, memory, disorientation, anxiety, sensory symptoms, insomnia, lightheadedness, appetite, dizziness, smell, taste, and headaches, we ask...are these things new post-COVID-19? Can they be explained by something else, or perhaps not?

The patients coming to our memory clinic are often trying to find physicians who have seen this before and are working to explain it. They didn’t go to the hospital when they had COVID-19, and they don’t have other long-term effects, so they are surprised to have these neurological symptoms.

The most common thing I hear from patients is, “I’m so glad to know that someone has heard of this.”

Do we know what’s causing these changes?

I think many people have heard about the severe inflammatory response and cytokine storm in COVID-19. What this means practically is that COVID-19 symptoms are not just caused directly by the virus alone.

In hospitalized COVID-19 patients, the effects of systemic inflammation on the brain seem more profound compared to other common infections that we see, like the flu. The level of inflammatory markers in the blood were often really severe. 

I'm not yet convinced that the virus invades the brain’s neurons or its other cells. I think it’s more likely that this vast, systemic inflammation affects many organs including the brain and the immune system within the brain. This changes the way the brain signals. Columbia neuropathologists recently led a report on a patient with inflammatory changes in the brain during his COVID-19 infection. This is a hint—that these changes may be occurring even without a true infection of the brain cells themselves. 

Studying the downstream effect of inflammation, in the body and in the brain, may lead us to the answer.

Can this virus cause lasting changes to the brain?

Probably. In SARS and MERS—two other serious diseases caused by coronaviruses—there were some longer term complications. For example, a few years after recovering from SARS, over 40% of patients reported active psychiatric illness and 40% complained of chronic fatigue.

But most SARS and MERS patients were hospitalized. We’ve never had the chance—until now—to study what happens with people who only experience mild symptoms. 

With a much larger population of affected people, we now have a great opportunity and responsibility to see if and how a virus can cause long-term neurological problems. COVID-19 could be a model of how acute neuroinflammation can have persistent effects on the brain. 

Thanks to an NIH grant in our Alzheimer’s Disease Research Center, we will be studying the possible mechanisms, especially in minorities historically underrepresented in scientific research. The free study is open to COVID-19 survivors age 65 and older, and patients will have the chance to learn about their own cognitive function post-COVID-19 while they contribute to science.

Contact for more information about the study.