The rare covid-19 brain infection
Some patients who have recovered from the disease have neurological sequelae
BarcelonaUncharted territory. If one could somehow define how the SARS-CoV-2 coronavirus affects the brain, this would most likely be the most accurate definition. The only thing that is certain is this: in one way or another, covid-19 reaches the brain, most likely through the nervous system, and some of the symptoms seen in patients are consistent with those of neurodegenerative diseases or strokes. The loss of the senses of taste and smell is also known, and in the case of persistent covid-19 or in elderly patients, the clinical anxiety, mental agitation and even delirium, are not at all strange. Experts assume that there is neurological damage followed by psychiatric disorders. To what extent, however, no one dares to say so.
A wide range of symptoms
The range of symptoms that have been observed in patients affected by covid-19 and who have overcome it continues to grow. The main ones affect the respiratory and circulatory systems, in addition to the liver and kidneys. For this reason, it is not uncommon for stroke and brain damage to occur in susceptible patients. Even the appearance of anosmia, the loss of the ability to perceive odours, seems to be expected. In the time that has passed since the beginning of the pandemic - just ten months -, the coronavirus has been seen to reach the blood-brain barrier, which protects the brain. That's where the taste and smell nerve endings are. What is still unknown is what happens when the virus crosses this barrier and reaches the brain. A growing suspicion is that it invades neurons and absorbs oxygen from surrounding cells, which would cause its death, according to a study by Akiko Iwasaki of Yale University. Images of brain tissue and experimental micro-brains support this hypothesis.
"We know that it arrives and that in all probability there is neuronal damage", explains Arcadi Navarro, ICREA researcher specialized in Parkinson's and director of the Pasqual Maragall Foundation. "We are seeing that the disease is aggravated by the viral infection", he points out. Some studies point to cases of loss of myelin, the protective layer of nerves. Despite not having enough data or reference models yet, other neurodegenerative diseases such as Alzheimer's or various dementias also seem to be getting worse. Why? "We don't know the molecular causes", replies Navarro. But like all experts in this field, he does suspect that if many of the patients with covid-19 have symptoms similar to those of neurodegenerative diseases, it is most likely that there is also death of neurons and consequent loss of function. In this regard, he foresees that "in the years ahead we will see serious pathologies" derived from the viral infection.
There is more. In an undetermined number of covid-19 patients, clinical presentations that would fit with psychiatric disorders are observed. In a first stage, they were attributed to the effects of lockdown and long periods of hospitalization. This is true for some patients, which would explain the anxiety or mental agitation, for example. It is not so clear, however, when cases of delirium, headaches, confusion and memory loss are observed, which may indicate an alteration of molecular origin. Michael Zandi, from the Imperial College in London, believes that some patients would not have died from respiratory complications but brain infection. This has yet to be solved.
In any case, there are even further doubts. The main one has to do with what experts call clinical management of patients. And here we have to make distinctions. There are those who arrive without any previous pathologies, and it is after the covid-19 infection that they end up presenting neurological or mental alterations; there are those who presented symptoms or risk factors; and there are those who had previous serious pathologies.
The last situation is the one that seems clearest and the only one that is beginning to be documented. The previous pathology, if it is of a neurodegenerative nature, is aggravated. "It seems as if the neuronal damage were increasing", Navarro says. This could be the case with Parkinson's and some dementias, according to studies published since the summer. The main problem, however, is how to distinguish those who now have symptoms if they were previously undiagnosed. Without a diagnosis, it is impossible to know if they have worsened or if covid-19 has caused neurological pathologies. The question will remain unanswered for some time.