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COVID-19 may primarily be a respiratory disease, but it’s clear that the virus can go on to strike critical organs beside the lungs. In some cases, the rest of the body, including the brain and almost every other part of the central nervous system, can also be affected. The neurological consequences — which can occur without other common COVID-19 symptoms like fever or chills, cough, fatigue, and shortness of breath — are quite broad, ranging from the serious (brain swelling and paralysis) to the less serious (headache or temporary loss of smell and taste).
COVID-19’s effects on the brain and nervous system seem fairly common, though numbers range widely. According to studies, the percentage of patients with neurological issues ranges from 7 percent to 67 percent.
Estimates by many experts are that at least half — and possibly as many as 80 percent — of patients seen in hospital COVID units have neurological symptoms. And one recent study published in the journal Neurology shows that their presence may indicate a more serious course of illness — even when lung problems aren’t severe. For instance, compared to a control group, patients with stroke were twice as likely to die (49 percent versus 24 percent) and those with confusion also had a significantly higher risk of death (40 percent versus 33 percent).
You don’t need to have a severe case of COVID-19 to experience neurological symptoms. Some occur, or are even more likely to occur, in milder cases of the disease — the type that 70 percent of people who contract COVID-19 develop — even before people develop any respiratory symptoms.
Neurologic issues don’t seem to discriminate age-wise, either. One study reported that nearly half of the people found to have “altered mental status” were younger than 60.
Symptoms of COVID-19 in the Brain and Nervous System
COVID-19 has a number of neurological manifestations, but a few “are exceedingly the most common,” says neurologist Deena Kuruvilla, MD, who co-authored a recent review article published in JAMA Neurology when she was an assistant professor of neurology at Yale School of Medicine. Luckily, they’re the least serious of those that can occur.
Loss of sense of smell (anosmia) and taste (ageusia)
This “olfactory dysfunction” is often the first — and sometimes only — symptom experienced by people infected with COVID-19. A study published in January in the Journal of Internal Medicine found that 86 percent of patients with mild cases of COVID experienced a blunting of their sense of taste and smell. These symptoms are more prevalent in mild cases than in moderate-to-critical forms, according to researchers. Over time, most people completely recover their sense of smell and taste.
In a recent case series of people with COVID-19, headache was a predominant complaint (along with fever, cough, sore throat, and breathlessness). “Prevalence varies in different reports, but headache can affect up to one-third of diagnosed patients,” says Dr. Kuruvilla, who is currently the Medical Director of the Westport Headache Institute in Westport, Connecticut.
Other Neurological Symptoms
Those symptoms are often just the tip of the neurological iceberg, however. Reports from around the world show a spectrum of brain-related issues that the coronavirus can cause, including:
- Loss of consciousness
- Memory loss
- Behavior changes
- Mood disturbances
- Loss of balance and muscle control
- Neuropathy (numbness in the extremities, usually the hands and feet)
- Stroke (blood clot in the brain)
- Cerebral hemorrhage (bleeding in the brain)
- Encephalitis (inflammation or swelling of the brain)
- Delirium (which involves confusion, impaired consciousness, disorientation, lack of attention, agitation, and other cognitive problems)
Often, these neurological symptoms are new, developing as a result of COVID-19. The journal Nature detailed the symptoms of psychosis in one woman in her mid-50s who saw lions and monkeys in her house and accused her husband of being an imposter.
Sometimes, though, COVID-19 can make preexisting neurological conditions worse, says Florian P. Thomas, MD, PhD, Founding Chair of Neurology and Chair of the Department of Neurology and Neuroscience Institute at Hackensack Meridian School of Medicine in Hackensack, New Jersey. Migraine and brain fog fall into both categories.
Generally, more serious neurological symptoms like dizziness, confusion, and paralysis tend to occur in people who are older, have preexisting conditions, such as kidney failure, liver failure, hypertension, diabetes, and obesity, and have had a stroke or seizure in the past, says David Altschul, MD, Chief of the Division of Cerebrovascular Neurosurgery and Surgical Director of the Montefiore Comprehensive Center for Stroke Care at Montefiore Medical Center in the Bronx, New York, in this video interview.
If you have some of these more serious neurologic symptoms of COVID-19, “it’s extremely important to go immediately to the hospital because these can be signs that you’re having a stroke and important testing is required that can only be done in the hospital,” says Dr. Altschul.
The Impact of Underlying Inflammatory Conditions on Brain Symptoms
Some of the neurological symptoms associated with COVID-19 are commonly experienced by people with inflammatory arthritis and other inflammatory or autoimmune conditions.
For instance, fatigue is a disabling symptom in chronic inflammatory conditions, including rheumatoid arthritis (RA), Sjögren’s syndrome, lupus, and multiple sclerosis. So are problems with memory, concentration, and slowed thinking — also termed cognitive dysfunction or brain fog.
On their own, these inflammatory conditions can also increase the risk for developing neurological symptoms. The risk of stroke is higher in most rheumatic diseases compared to that of the general population, particularly over the age of 50. RA and lupus increase the risk of stroke by up to 100 percent relative to the general population.
The takeaway: It’s important to be mindful of your symptoms and report any new or worsening symptoms to your health care provider. They can advise you on what to do next based on your medical history.
For instance, given the reports of loss of smell and taste presenting as early symptoms of COVID-19, dedicated testing for the loss of smell and taste — which can occur with diseases like Parkinson’s and MS, as well as obesity, diabetes, and high blood pressure, all of which are comorbidities of chronic inflammatory conditions — may offer the potential for early detection of COVID-19 infection, says Dr. Kuruvilla.
How COVID-19 Impacts the Brain
How COVID-19 affects the brain is an active area of research, but there are several ways it’s believed to act:
“The virus that causes COVID-19 can penetrate the brain and entire nervous system through a very specific receptor,” Dr. Kuruvilla explains. This receptor, the angiotensin-converting enzyme 2, is very similar to receptors in the lungs that have served as gateways for the coronavirus to attack cells there. The altered sense of smell and/or taste that people with COVID-19 often experience is thought to result from the virus spreading to the brain through the nose.
More worrisome is a new study that found that the virus is able to infect neurons (brain cells) and then use the machinery of these cells to replicate. This can lead to a decreased blood supply that can potentially disrupt the brain’s oxygen supply, causing localized tissue damage and cell death that may be associated with some of the neurologic symptoms that appear with COVID-19. Even by itself, low oxygen levels can negatively affect brain tissue and lead to confusion, coma, or permanent brain damage.
Immune system overreaction
The immune system normally reacts to a virus by making cytokines, proteins that help coordinate the body’s response against infection by triggering inflammation. The cytokines kill cells in order to keep the virus from replicating. Though this is a good thing in terms of combatting COVID-19, the release of cytokines is one pathway that is thought to trigger sensory neurons that can cause head pain, including that which often accompanies migraine.
And sometimes the immune system doesn’t turn off once the virus is controlled. Instead, it kicks into overdrive, releasing uncontrolled levels of cytokines that cause an intense and widespread inflammatory response. Known as a cytokine storm, this “hyperinflammation” can cause more damage than the virus itself, seriously harming or even proving fatal to patients.
COVID-19-related encephalitis, or inflammation of the brain, is an example of this type excessive mobilization of the immune system, in which the body mistakenly attacks its own brain tissue.
Persistent inflammation can is also believed to trigger an acute episode of delirium, which “is sometimes connected to people not noticing how sick they really are,” says Dr. Thomas. Delirium is being recognized as a common symptom of COVID-19, particularly in older patients, where it may be the first or only sign of illness, but in younger folks as well. Over time, it can cause neurons and brain cells to deteriorate, leading to cognitive damage.
“COVID results in a lot of inflammation, including in blood vessels and in sticky blood cells,” Dr. Thomas explains. The blood’s exaggerated tendency to clog could block or narrow arteries leading to the brain, triggering a stroke, an interruption of the blood supply to the brain.
Strokes occur rarely in COVID-19 cases — in about 2 to 3 percent of people infected — and mostly in people who are critically ill. That said, research is showing an increased association between COVID-19 and stroke in younger people (under the age of 50) without typical risk factors, at times with only mild respiratory symptoms. This may have to do with the ability of the coronavirus to attack the endothelial cells that line the blood vessels, causing inflammation that can raise the risk for blood clots. The endothelial system is more biologically active in younger patients, and the combination of hyperactive endothelial and blood-clotting systems puts these patients at major risk for developing blood clots, according to Johns Hopkins.
“A COVID-19 infection has expectations of being a severe disease, so it’s a major traumatic event, especially if a patient needs to stay in the hospitalized and doesn’t have loved ones nearby to comfort them,” Omar Danoun, MD, a neurologist with Henry Ford Health System in Detroit, Michigan, explained in a recent interview.
This experience, he says, can cause post-traumatic stress disorder. “The symptoms we see in these COVID-19 patients are similar to those we see in PTSD survivors — they have confusion, memory loss, anxiety, or depression.”
What This Means If You Have a Chronic Illness That Affects the Brain
People with chronic conditions that affect the brain report significant worsening of their condition — in both severity and frequency — if they contract COVID-19.
“SARS-CoV-2 launches a robust cytokine inflammatory response within the body, worsening conditions that are affected by inflammation, such as migraine, arthritis, and fibromyalgia,” says Dr. Kuruvilla. The symptoms in these conditions worsen due to this inflammatory storm, making pain difficult to treat. The use of nerve pain medications can be helpful in these cases, whether they are caused or worsened by COVID-19, she says.
Other specifics on the impact of COVID-19 on various underlying chronic conditions:
- Depression: People report feeling more down and helpless after becoming sick.
- Multiple sclerosis: Recovery from COVID-19 for those with this autoimmune disease has been slower, says Dr. Kuruvilla.
- Parkinson’s disease: It’s very common for PD symptoms to worsen when people develop another disease. For instance, people with Parkinson’s who develop COVID-19 may find it more difficult than normal to walk.
Neurological symptoms of varying types can occur with any severity of COVID-19, says Dr. Thomas. “I personally know four people who suffered altered sense of smell and taste as the only manifestations,” he says. “On the other hand, we see COVID-related stroke more in people who are quite sick.”
He hasn’t yet seen COVID-related manifestations in people who had no neurological problems during the acute infection, but developed them later. “But given how much we have learned in the past months about this condition, I would not be surprised to see such patients in the future,” he says.
Many people, in particular those with mild symptoms who never get admitted to a hospital, recover quite rapidly and completely from COVID-19, says Dr. Thomas. Others, known as “long-haulers,” may experience fatigue, sadness, and memory problems that can persist.
Studies have found that at least half of people who recover from COVID-19 continue to suffer from neurological symptoms for months after.
How to Stay Safe and Protect Yourself
Even if the rate of vaccinating people increases, it may still be a while before you get to roll up your sleeve — and even then, it could take months for the spread to slow. In the meantime, it’s important to take extra precautions, especially if you suffer from underlying conditions that can put you at greater risk of developing COVID-19 and associated brain symptoms. Here’s what to do:
Protect yourself from getting COVID-19
Avoiding contact with COVID-19 is key to safeguarding your health. It’s important to do all the things you’ve likely already been doing (or should have been doing) to reduce the chance of getting or spreading the virus:
- Get a COVID-19 vaccine when it is available to you
- Wear a mask that covers your nose and mouth. This will protect yourself as well as others.
- Practice social distancing. For now, experts say you should assume that everyone you encounter in your daily life could be infected with the coronavirus — as many as half of the people who test positive for the virus have no symptoms and, according to new research, more than half of transmission comes from asymptomatic people. This makes it very important to stay at home if possible — avoid gatherings and non-essential trips — and to keep at least six feet apart (about two arms’ length) from people who aren’t in your household in both indoor and outdoor spaces.
- Wash your hands frequently with soap and water for at least 20 seconds or use hand sanitizer with at least 60 percent alcohol.
Get a flu shot
The flu can make you more susceptible to infection by other pathogens, including COVID-19. “In fact, a lot of the deaths of the 1918 flu pandemic were probably from staphylococcal pneumonia as a superinfection on top of influenze pneumonia,” George Rutherford, MD, an epidemiologist at University of California San Francisco, said in this recent article.
Flu vaccination is a particularly important prevention tool for those with underlying health conditions who are already susceptible to both the flu and COVID-19. The best time to get a flu shot is early in the flu season, but it’s never too late — flu activity peaks between December and February, but activity can last as late as May, according to the CDC.
Be aware of warning signs for COVID-19
You may be familiar with the respiratory/flu-like symptoms of COVID-19, including fever, cough, fatigue, and shortness of breath. As well, pay attention to potential neurological symptoms.
Any change in headaches, new headaches, or new continuous severe types of headaches should prompt patients to reach out to their doctors to consider a COVID-19 diagnosis, Dr. Kuruvilla advises. Any new symptom of loss of smell or taste should also be warning signs for the disease. “These three symptoms are the most frequent neurological manifestations and should prompt an immediate medical evaluation,” she says. “Early detection of neurological deficits may lead to improved clinical outcomes.” It can also help prevent further transmission of the disease.
Adopt or maintain good health habits
“It’s always essential to control blood pressure, diabetes, and any other underlying health issues you may have,” advises Dr. Danoun. “Avoid smoking and alcohol, eat a healthy diet, get enough rest.” If you do contract COVID-19, all of these things will create a nourishing environment for your body to recover.
Prioritizing sleep is of particular importance, as too little shuteye may weaken your defenses against a virus. As you await your chance to receive the COVID-19 vaccine, it’s helpful to know that sleep can also optimize your immune system’s response to a vaccine, in part because it’s a great stress reducer — and stress can hamper the body’s immune response. One study found that the flu vaccine appears to be more effective — responses are quicker, more robust, and longer lasting — in people who get a sufficient duration of sleep for the two nights prior to receiving the shot, and other studies have made similar findings in response to other vaccines.
Finally, speak to your health care provider about which vitamin supplementation is important for you, Dr. Kuruvilla suggests. Some studies, though certainly not all, have shown that low vitamin D levels can leave you more vulnerable to COVID-19 and result in more severe disease.
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