The SARS-CoV-2 coronavirus attacks the respiratory system, but there is growing evidence that it also affects the nervous system. Several studies based on thousands of Spanish patients show that most of these individuals developed at least one neurological problem. This manifested itself in a wide range of symptoms, ranging from headaches to comatose states. In a percentage of cases, neurological conditions were even the principal cause of death. Although these symptoms have been attributed to the body’s excessive immune response to Covid-19, some research indicates that the virus is directly attacking the brain.
The Spanish Neurology Association (SEN) has collated the most recent studies carried out in Spain on the connection between the coronavirus, the brain and the entire nervous system. The research is varied; it includes investigations on how the virus changes a person’s sense of smell and taste, research on headaches in infected healthcare workers, and a study into strokes in 1,600 patients with Covid-19.
But the most significant piece of research is a registry called Albacovid, which studies the neurological conditions observed in 841 coronavirus patients in two hospitals in Albacete in the Spanish region of Castilla-La Mancha during the peak of the crisis in March. The results, published in the specialist journal Neurology a few weeks ago, show that 57% of these patients developed one or several neurological symptoms.
“The neurological spectrum is very wide,” says Tomás Segura, the head of neurology at the University Hospital of Albacete, which was one of the two medical centers to participate in the paper. According to Segura, who co-authored the study, the most common symptoms experienced by coronavirus patients were myalgia, headaches and dizziness. He points out that nearly 20% also presented disorders of consciousness, although these symptoms were concentrated among elderly patients. Another 20% of patients (they are not exclusive groups) developed neuropsychiatric problems such as insomnia, anxiety and psychosis. “Some of the symptoms, like myalgia, insomnia and headaches, had not been observed in previous studies,” adds Segura, who also teaches at the University of Castilla-La Mancha.
The range of symptoms does not end there. In a small but significant percentage of cases (between 1% and 5%), neurologists also detected myopathy (neuromuscular disease), dysautonomia (a dysfunction that affects the autonomic nervous system) and cerebrovascular diseases such as stroke. In less than 1% of cases, the researchers also observed convulsions, movement disorders and encephalitis in patients. In a dozen cases, the patient went into a coma. What’s more, neurological complications were the main cause of death in 4% of coronavirus victims, according to the study.
“The Albacovid registry indicates that neurological symptoms are more common in coronavirus hospital patients than was once thought,” says doctor José Miguel Lainez, the president of SEN. “Additionally, the fact that this registry has been made with the largest number of patients, compared with other studies carried out in other countries, leads us to believe that the data in this register are more accurate, at least in relation to the Spanish population.”
The most common symptoms experienced by coronavirus patients were myalgia, headaches and dizziness
Another large-scale study, this one with 909 coronavirus patients in Madrid, showed that 90% of cases simultaneously experienced changes to, or the loss of, the sense of smell and taste. In most of these cases, these changes were the only clinical expression of coronavirus or were accompanied by other minor symptoms. Other viral infections, like those caused by the flu, rhinovirus and human parainfluenza viruses, also cause these disorders, but this is attributed to the nasal condition caused by the infection. In the Madrid study, more than half of the patients did not experience any congestion. This means that the coronavirus may be directly acting against the central nervous system.
The most recent study was published last week in the prestigious journal Brain. This investigation, which featured the largest number of patients (1,683) and longest duration (50 days), was aimed at detecting and analyzing cerebrovascular disease in patients with Covid-19. According to the research, 23 of these patients (1.4% of cases) suffered a brain attack or stroke. What is relevant in this case is not the number of cases, which is also significant, but the quality of the data, which is based on neuroimaging and an analysis of the affected brain tissue. The evidence of these small episodes of generalized strokes is of concern to neurologists, because it could indicate that the coronavirus can enter the brain.
“The brain is characterized for being isolated from the bustle of the world. If there is a pathogen in the rest of the body, the blood-brain barrier stops it from entering,” explains Segura. This defense system allows oxygen-filled blood to reach the capillaries and even the neurons, but filters out toxins, bacteria and viruses that travel in the bloodstream. “The rupture of this barrier is an effect that we have not seen before,” he adds. For Segura, finding the endothelial cells (the thin layer of cells that line the interior surface of blood vessels) in the samples of analyzed brain tissue could indicate that the coronavirus has overcome the blood-brain barrier, and that the neurological problems have not been caused by weakness from the immune system’s response to Covid-19. According to Segura, the world is facing “a respiratory virus that is also neurotoxic.”
English version by Melissa Kitson.