Brain COVID-19 (coronavirus)

Understanding COVID-19 long haulers

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Months after being infected with COVID-19, some patients continue to experience symptoms that are persistent, debilitating and seemingly unexplainable. This growing number of people are often referred to as COVID long-haulers or having long COVID, but little is known about what’s causing their chronic symptoms.

Dr. Matthew Burke, a cognitive neurologist and associate scientist at Sunnybrook and assistant professor at the Temerty Faculty of Medicine at the University of Toronto, shines a light on the neuropsychiatry of long COVID in a recently published commentary in The Lancet Infectious Diseases.

As a strong advocate for the border-zones between neurology and psychiatry and complex brain-body interactions, Dr. Burke says highlighting long COVID is an opportunity to better understand and research chronic unexplained medical symptoms.

What symptoms do COVID long haulers experience?

Dr. Burke: Symptoms of long COVID can include fatigue, difficulty concentrating, mood disruptions, headaches, sleep disturbances, dizziness, shortness of breath and a variety of other neurologic and physical symptoms. Some patients have described “brain fog,” a non-medical term that has been used during the pandemic when patients feel sluggish or are not able to think clearly. These symptoms are being reported by patients even with mild COVID-19 that did not require hospitalization or medical attention, sometimes long after they test negative for COVID-19. Unfortunately, for most of these symptoms, currently there are no objective findings or test results to aid in the diagnosis, which can be challenging for both patients and health-care providers.

What might explain these lingering symptoms?

Dr. Burke: There are two general possibilities that researchers are currently exploring. The first is that COVID-19 may trigger post-infectious processes that generate persisting symptoms in a unique way that we haven’t encountered before. While we generally like to have simple and unifying explanations in medicine, there have been unique aspects of COVID-19’s interaction with the brain and body and further research is needed to evaluate this possibility.

Alternatively, COVID-19 long-haulers may fit into the category of mysterious “unexplained” chronic symptoms (post-infection or not) and could operate via similar mechanisms. This group of patients already represented a relatively large segment of medicine (pre-pandemic) and proposed mechanisms to explain symptoms in this field is very controversial. At one end of this debate, there are purely “physiological” theories, and on the other end purely “psychological.” However, recent neuropsychiatry models suggest that there is not always a clear-cut explanation, that it is likely a more complex spectrum. For example, pre-existing genetic and psychosocial factors may result in dysfunction of brain or brain–body circuits that then interact with a potential triggering event (ie. infection). It is also critical to understand that there may be different sub-groups of patients with prolonged symptoms after COVID-19 with differing mechanisms between groups.

The most important thing we can do right now is continue to study long COVID without assumptions to better understand why these symptoms are being triggered.

Are these symptoms unique to COVID-19?

Dr. Burke: The clusters of symptoms reported by long-haulers are not unique or specific to long COVID and are common in many of the patients I see with medically unexplained symptoms or functional disorders. Some patients will similarly experience symptoms after an infection like COVID-19, while others report other potential triggers (such as a relatively mild injury) and for some, there are no identifiable triggers at all.

Unfortunately, this segment has been a blind spot for medicine and inadequate management and care pathways often leads to patients seeking multiple secondary opinions and unnecessary investigations, leaving them frustrated and putting strain on health-care resources.

What should patients do if they are experiencing symptoms of long COVID?

Dr. Burke: Talk to your health-care team about the symptoms you’re experiencing and how they can best be managed. It’s important for health-care professionals to listen and validate patients’ experiences, even when diagnostic testing may not reveal any abnormalities.

COVID-19 is still a new disease and we’re learning more about its impact on the body each day. Similarly, the brain is complicated and these disorders could be linked to some of the most poorly understood parts of it. It will take some time before we fully understand long COVID, but I’m hopeful that continued research will provide valuable new insights for this broader field and help patients who are searching for answers.

Read the commentary in The Lancet Infectious Diseases

About the author

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Samantha Sexton

Samantha is a Communications Advisor at Sunnybrook Research Institute.

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