The COVID-19 pandemic has had a significant impact on the health and wellbeing of millions of people worldwide. One concerning aspect of the disease is its effects on the brain and nervous system. There is growing evidence that COVID-19 can cause neurological complications in some patients, both in the short and long term.
In this article, we will look at the key questions around how COVID affects the brain:
What are the neurological symptoms of COVID-19?
Many COVID-19 patients experience neurological symptoms including headache, dizziness, loss of taste and smell, and tingling or numbness in the extremities. More severe symptoms have also been reported, like stroke, seizures, confusion and delirium, muscle weakness, and problems with movement and coordination.
A study published in The Lancet Psychiatry analyzed neurological manifestations in 125 COVID-19 patients in Wuhan, China. It found that 36% had some type of neurological symptom, with dizziness and headache being most common. Severe symptoms like impaired consciousness were rare but did occur.
Loss of taste and smell is now recognized as a common COVID symptom that persists long after initial infection in some people. This is thought to be caused by the virus damaging cells in the olfactory epithelium, which plays a key role in transmitting smells from the nose to the brain.
How does COVID cause neurological damage?
There are a few ways COVID-19 can potentially cause neurological dysfunction:
- Inflammation – The virus triggers an inflammatory response and cytokine storm, which may damage nerve tissues.
- Hypoxia – Low oxygen levels, often due to respiratory complications, damages neurons and brain cells.
- Blood clots – Clotting disorders lead to strokes and other problems with blood supply.
- Direct viral infection – The virus may be able to infect nerve cells in some cases.
The SARS-CoV-2 virus is known to bind to ACE2 receptors, which are present in neurons and glial cells in the brain and central nervous system. Autopsy studies have found evidence of viral particles and inflammation in brain tissue of COVID-19 patients.
What types of neurological conditions are linked to COVID?
Some of the key neurological complications reported:
Stroke
Multiple studies show an increased risk of ischemic and hemorrhagic stroke in COVID-19 patients. A meta-analysis found stroke risk was over 7 times higher compared to non-COVID influenza patients. Large vessel occlusion strokes also appear to be more common, leading to worse outcomes.
Delirium and encephalopathy
Delirium is an acute decline in mental functioning marked by inattention and confusion. Encephalopathy refers to broader conditions affecting brain function. Both have been frequently observed during COVID, especially in severely ill patients requiring ICU care. Hypoxia and inflammation are likely drivers in many cases.
Guillain-Barré syndrome
This rare disorder causes progressive paralysis as the immune system attacks peripheral nerves. Small case studies have linked Guillain-Barré syndrome to COVID-19, though the connection requires more research. It is thought previous viral infections can trigger the syndrome in some people.
Seizures and epilepsy
Seizures have been observed in a subset COVID-19 patients, in some cases manifesting as the initial symptom. COVID also appears capable of exacerbating underlying seizure disorders. Fever and metabolic disturbances may play a role in lowering seizure threshold.
Neurological symptoms and long COVID
For some people, neurological symptoms persist for months after initial COVID infection, as part of the long-term complications known as “long COVID.”
Surveys of long COVID patients consistently show neurological and cognitive symptoms are among the most commonly reported. These include:
- Headaches
- Dizziness
- Loss of taste/smell
- Tingling and numbness
- Impaired concentration, focus and memory
- Difficulty finding words
- Brain fog
Smaller studies using advanced MRI imaging have found brain volume loss, microstructural changes and functional connectivity changes in the brains of some recovering COVID patients. The cause and long-term implications of these changes is still being investigated.
Are neurological problems more likely with severe COVID?
Yes, the risk of neurological complications appears higher in patients with more severe COVID disease.
One study found that over 80% of COVID-19 patients who developed encephalopathy were critically ill requiring intensive care. Patients with severe respiratory disease are at higher risk of hypoxia, blood clots and cytokine storm, which likely drive neurological damage.
However, mild and moderate COVID has also been linked to neurological manifestations. More research is needed, but even less severe disease seems capable of injuring nerve tissue and passing the blood-brain barrier in some cases.
How is COVID-related brain damage treated?
There are no specific treatments for neurological complications of COVID-19. Management focuses on:
- Supportive care – Controlling symptoms, managing pain, preventing secondary infections.
- Treating underlying issues – Improving oxygenation, correcting coagulation disorders, regulating immune response.
- Standard care for the neurological disorder – Such as thrombolytics for ischemic stroke, anti-seizure medicines for seizures.
- Rehabilitation – Physical, occupational and speech therapy for those recovering from stroke or other brain injury.
Identifying and mitigating potential neurological damage early in the course of COVID-19 is important to improve outcomes. More research is urgently needed on how to best prevent and treat neurological complications.
What are the long-term consequences?
The long-term consequences of COVID-related neurological injury are still unknown.
Some key concerns include:
- Lasting cognitive deficits or disabilities – Especially in those who suffered strokes, delirium or hypoxic brain injury during severe COVID.
- Increased risk of neurodegenerative disease – There are concerns viral infections may accelerate cognitive decline.
- Chronic headaches, dizziness, sensory issues – Already observed in many long COVID patients.
- Post-traumatic stress disorder and mental health issues – Both as a result of the neurological impacts of the virus and the trauma of severe illness.
However, the brain also demonstrates remarkable plasticity and ability to heal and adapt. Milder neurological manifestations like loss of smell often resolve spontaneously over weeks to months.
Careful longitudinal study of recovered COVID patients will be needed to understand long-term outcomes. Some experts expect the burden of neurological disease will likely rise in the post-pandemic world.
Key takeaways
- Headaches, dizziness, loss of smell and altered mental status are common neurological symptoms of COVID-19.
- Severe complications like stroke, seizures and encephalopathy are rarer but do occur.
- Inflammation, hypoxia, blood clots and viral infection can all potentially injure the brain and nerves.
- Cognitive and sensory problems are among the most common lingering symptoms in long COVID.
- Those with mild COVID can also experience neurological effects, though risk is higher with severe disease.
- It is unclear if COVID-19 leads to lasting neurological damage and increased neurodegenerative risk.
- More research is urgently needed to understand, prevent and treat neurological complications.
Conclusion
COVID-19 is proving capable of causing acute neurological injury in some patients, as well as longer-lasting sensory, cognitive and mental health effects. However, our understanding of its impacts on the brain and nervous system are still in the early stages. With the pandemic still raging globally, there needs to be much more focus on investigating how SARS-CoV-2 affects neurological function, finding optimal treatments, and carefully monitoring recovered patients for any long-term consequences. A multidisciplinary approach combining expertise from neurologists, psychiatrists and infectious disease specialists will be essential. COVID-19 may represent the beginning of a significant new intersection between infectious diseases and neuroscience.