What are the Neurological and Psychiatric Impacts of Covid-19?

Prof. Jean-Christophe Corvol, neurologist at the Pitié-Salpêtrière Hospital and director of the Neuroscience Clinical Investigation Center of the Paris Brain Institute, has been conducting a study that seeks to better understand the neurological and psychiatric consequences of Covid-19. On the occasion of Brain Week, he talks about his research project Cohorte Covid.

In what context did you launch this clinical research study?

Jean-Christophe Corvol: During the first wave of Covid-19 in 2020, we were mobilized, as neurologists, to follow Covid patients hospitalized at the Pitié-Salpêtrière Hospital. Very quickly, the presence of neurological symptoms (loss of taste and smell, headaches) in these patients allowed us to detect the neurotropism of the virus, i.e. its ability to infect the nervous system.
With the support of the Paris Brain Institute and the AP-HP, and thanks to a donation from the Fédération Internationale de l'Automobile (FIA) and funding from the Fondation de France, we set up a study to identify all the neurological and psychiatric symptoms linked to Covid-19 in order to understand how the nervous system was affected by this disease.

What were the objectives of this study, and its methodology?

J.-C. C.: The objective was twofold. On the one hand, to describe, in all their complexity, the neurological and psychiatric symptoms that appeared after a SARS-Cov-2 infection. On the other hand, we wanted to see what the impact of Covid-19 was in patients who already had chronic neurological or psychiatric pathologies.
In order to have a global and standardized vision, the study brought together a wide range of experts from the medical-university department of neurosciences involved in the evaluation and management of neurological and psychiatric diseases: neurologists, rehabilitators, psychiatrists, neuro-imaging platforms, specialists in neuropathology, neurophysiology or anatomopathology.

What were the results of this study?

J.-C. C.: Between March and April 2020, more than 500 of the 2000 patients hospitalized for Covid-19 presented neurological manifestations. We observed a very wide range of symptoms, with attacks that can affect the central nervous system (brain, brain stem or spinal cord) as well as the peripheral nervous system (nerves, neuromuscular junctions, etc.). If taste and smell disorders were the most frequent (about 80%), 40% of the disorders concerned motor deficits, 35% cognitive disorders (memory disorders, attention disorders, etc.), 20% psychiatric disorders (anxiety, depression, delirium, hallucinations, etc.), 20% headaches.
In addition, 16% of the patients had a cerebral vascular accident (CVA) and 40% had encephalopathies (confusion, behavioral disorders, epileptic seizures, etc.) related to a central nervous system disorder. Many of the patients who were discharged from the intensive care unit suffered from post-awakening confusion, complications related to intubation, peripheral nerve damage due to the positioning adopted during the weeks of resuscitation, or psychiatric complications directly or indirectly related to the virus.

Have you been able to identify the causes and mechanisms of action related to the cerebral and neuronal complications of the virus?

J.-C. C.: Our imaging study demonstrated that most of the brain lesions were not directly related to the damage of the nervous system by the virus (less than 10%). And in the patients who underwent a lumbar puncture, we did not find any trace of the virus in the cerebrospinal fluid that bathes the brain and the nerves.
In the majority of cases, the causes of these brain lesions are vascular (stroke-type), due in particular to the ability of SARS-Cov-2 to form clots in the blood, or systemic or immune: by reacting against the virus, the immune system can lead to long-term neurological complications. In the end, there were very few complications directly related to an attack on the nervous system by the virus itself, such as encephalitis or myelitis.
Work is still in progress at the anatomopathological level to better understand the mechanisms of action of the virus on the different cells of the brain tissue.  

What impact did Covid-19 have in patients who already had neurodegenerative diseases?

We found that in most of them, the SARS-Cov-2 infection tended to worsen their symptoms in a transient and mostly reversible way. Many patients with Alzheimer's disease had confusion or delusions, and many patients with Parkinson's disease had worsening motor difficulties. However, about 15 days after the end of the infection, they generally returned to their previous state, although unfortunately, in some patients the infection helped them to reach a milestone in the evolution of their disease. In addition, infection-related mortality was generally higher in patients with advanced neurological disease.

What management do you suggest for the neurological and psychiatric complications caused by Covid-19?

J.-C. C.: The neurological symptoms that we have observed in patients respond to standard rehabilitation protocols and we have managed them in our departments. On the other hand, we still know very little about the long-term complications on the nervous system: patients can be apathetic, tired, anxious, have cognitive difficulties, headaches, abnormal movements persisting for months after the infection, without any neurological lesion being observed.
We now need to follow these patients over the longer term to understand what is happening and try to prevent complications.

What are your research perspectives related to the neurological consequences of Covid-19?

It is now clearly established that SARS-Cov-2 infection affects the nervous system. Now the question is whether the brain damage caused by the disease is reversible or will leave traces, or even be the basis for a neurodegenerative process in the longer term. It is therefore important that epidemiological work be carried out to find out whether people infected by the virus are at greater risk of developing a degenerative disease later on.
In addition, we have launched a national study on the immune and vaccine response to Covid in patients with multiple sclerosis treated with immunosuppressants. Initial results suggest that they do not obtain a sufficient immune response after vaccination and are therefore at a greater risk of developing severe forms of the disease.
We are also studying rare neurological forms in which the virus infection acts directly on the nervous system to see whether they are linked to particular genetic factors.