Headache, mental fog and dizziness are some of the symptoms caused by the coronavirus. Most patients do well, but some alarmist studies suggest that the infection could trigger Alzheimer’s or Parkinson’s disease in the future. At present, there is no data to confirm these hypotheses.
Veronica Fuentes 29/1/2022 08:00 CEST
Headaches, weakness and nerve problems occur in some individuals during the onset of covid-19. / Adobe Stock
Although SARS-CoV-2 is usually considered a respiratory virus, acute infection can also affect many different organ systems, including the brain. Since the onset of the pandemic, a wide range of neurological complications with lasting repercussions have been observed and reported in up to 36.4% of patients. However, much remains to be studied.
Science magazine has put the issue back on the table with the publication of a paper – by Serena Spudich of Yale University School of Medicine and Avindra Nath of the National Institute of Neurological Disorders and Stroke (one of the prestigious US NIH) – that reviews various research published so far on the neurological symptoms of covid-19 and the possible mechanisms that cause them.
According to their summary, most people who experience these neurological manifestations that remain after the disease are under the age of 50 and were healthy and active prior to infection.
“In some individuals, stroke, confusion, headaches, weakness and nerve problems occur during the onset of covid-19,” Spudich tells SINC. “Months after recovery, some patients have difficulty thinking, abnormal skin sensations, constant headaches and other neurological symptoms.
“Even those with mild initial illness manifest a wide range of persistent neurological and psychiatric manifestations, so millions of people who have recovered from coronavirus are at risk of these conditions,” adds Nath.
Most patients do well
Some of the studies compiled by the two authors suggest that covid-19 infection may trigger the future development of neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease. However, there is no data to support the alarmism.
This is what José Miguel Láinez, president of the Spanish Neurology Society (SEN), points out. “What appears in postcovid syndrome is mainly headache and what is known as mental fog (memory loss, confusion); also dizziness and smell problems. The fact that there are no structural lesions of the brain – no apparent parenchymal lesions – is positive, suggesting that there are unlikely to be major long-term consequences.
In fact, most of these patients do well. “When so many people are affected, there could be a certain genetic context that facilitates some kind of neurodegenerative disease; it cannot be ruled out. But from there to thinking of an epidemic, there is no basis for it,” he stresses.
When so many people are affected, there could be some genetic context that facilitates some kind of neurodegenerative disease; it cannot be ruled out. But from there to thinking of an epidemic, there are no grounds for it.
José Miguel Láinez, President of the SEN
One of the reasons behind these fatal forecasts is, according to Raquel Sánchez-Valle, head of the Neurology Service at the Hospital Clínic in Barcelona, that “postmortem brain findings are magnified. The subjects who died from covid are not comparable to what can happen in a patient who overcomes the acute phase of the disease and subsequently develops (or not) persistent covid”.
Moreover, according to Láinez, “there are no major lesions in the autopsy studies either. There are viral particles and some inflammatory reactions, although there is practically no direct invasion of the virus. It is true that there are some small changes, although they do not seem to be massive.
“Longitudinal studies with biological markers are needed, and that is what we are already doing at the Clínic de Barcelona,” says Sánchez-Valle. “We have recruited about 50 subjects with postcoital cognitive problems. We will soon be able to finalise the research and have the results.
Need for long-term studies
The authors of the Science study stress the urgent need to understand the pathophysiology of these disorders and develop therapies to address them. “Nervous system complications pose a public health challenge in terms of rehabilitation and recovery, as well as workforce disruption due to loss of functional capacity,” they write.
For this reason, there are numerous projects studying covid in the long term. One of them is being developed at the Memory Unit of the Hospital Sant Pau. “Persistent covid is a post-viral syndrome, as we have seen in other infections such as mononucleosis caused by Epstein-Bar virus or cytomegalovirus,” Alberto Lleó Bisa, its director, tells SINC.
There are currently numerous projects studying covid in the long term. One of these is being carried out at the Memory Unit of the Hospital Sant Pau.
“The symptoms are very non-specific and are reminiscent of chronic fatigue syndrome. All the tests are normal and there is no specific treatment at present, so insomnia, anxiety, etc. are treated symptomatically,” continues Lleó Bisa, who published an article on the subject last December.
The specialist points out that they can also occur in cases after mild covid and the symptoms can last for weeks or months: “And given that it affects so many people, it could have a significant functional and occupational impact”.
However, Láinez argues that “so far it does not seem that there will be serious consequences, although obviously we cannot let our guard down and more studies are needed. The so-called long covid is somewhat similar to fibromyalgia, which has also been associated with viruses. We need to continue researching and monitoring these patients to see how they evolve.
On possible mechanisms leading to these neurological symptoms, Spudich and Nath’s paper lists vascular and immune dysfunction – such as non-specific neuroinflammation and anti-neural autoimmune dysregulation – and possible viral infection in the central nervous system.
“Evidence to date suggests that the main cause of neurological symptoms in the acute phase of covid-19 is related to the body’s immune response to SARS-CoV-2, including general activation of the immune system and more specific attack on the brain and other nerve cells, termed autoimmune responses,” the authors announce.
It is important to note that these complications are not related to the virus being active, but are a sequela probably related to the inflammation caused by the virus in the acute phase.
Alberto Lleó Bisa, director of the Memory Unit
“It is likely that injury to small blood vessels caused by clotting problems and inflammation also plays a role in some cases,” they add. “We need to investigate whether the long-term neurological and psychiatric symptoms that persist in some people after recovery are related to the persistence of these immune and vascular abnormalities, or arise from other causes.
As Lleó Bisa points out, “it is important to note that this is not a case of the virus being active, but a sequela probably related to the inflammation caused by the virus in the acute phase”.
How can this knowledge improve treatment for SARS-CoV-2? “To date, specific treatments for the neurological complications of covid-19 are uncertain. Patients with signs of stroke are usually treated with drugs to prevent blood clotting or the clumping of platelets in blood vessels to prevent further episodes,” Spudich tells SINC.
Research is now investigating whether treatments aimed at reducing inflammatory and autoimmune effects on the nervous system may benefit people with neurological and psychiatric complications of covid-19.
And patients with confusion, nerve problems and headaches are often treated to control pain until symptoms improve, as Nath completes.
Serena Spudich, Avindra Nath. Nervous system consequences of COVID-19. Science DOI 10.1126/science.abm2052