[Long COVID : neurological aspects]. / Covid long : aspects neurologiques.

The study of post-COVID-19 symptomatology revealed a first wave of post-acute (persistence of symptoms less than 3 months) neurocognitive symptoms. However, some of these symptoms worsened, while others improved. To our knowledge, these symptoms may persist for up to 1 to 2 years after infection. The intensity, variability and persistence of neurocognitive symptoms may rise the hypotheses of accelerated neurodegenerative processes, as well as neuropsychiatric and/or genetic vulnerabilities that are still poorly understood. Moreover, the multi-organ manifestations of post-COVID-19 symptoms remind us of the importance of promoting an interdisciplinary perspective at both clinical and fundamental levels. Finally, many social and economic issues parallel to the neuropathological consequences remain to be investigated.

L'étude de la symptomatologie post-Covid-19 a permis de mettre en évidence une première vague de symptômes neurocognitifs postaigus (persistance des symptômes inférieurs à 3 mois). Certains se sont aggravés, tandis que d'autres se sont améliorés. Ils peuvent perdurer jusqu'à 1 à 2 ans après l'infection. L'intensité, la variabilité et la persistance des symptômes neurocognitifs pourraient suggérer des hypothèses d'accélération de processus neurodégénératifs et des vulnérabilités neuropsychiatriques et/ou génétiques encore mal comprises. De plus, les manifestations multi-organiques des symptômes post-Covid-19 nous rappellent l'importance de promouvoir une perspective multidisciplinaire sur les plans clinique et fondamental. Finalement, de nombreuses questions sociales et économiques parallèles aux conséquences neuropathologiques restent à investiguer.

[Post-COVID-19 neuropsychological syndrome]. / Syndrome post-Covid-19 neuropsychologique.

Recent observations suggest the persistence of neurological and neuropsychological symptoms in the long-term following SARS-CoV-2 infection. Currently described within the post-COVID-19 syndrome. The objective of this article is to discuss recent epidemiological data and data from neuroimaging studies. Finally, a discussion is proposed regarding recent suggestions regarding the existence of distinct phenotypes of post-COVID-19 syndrome.

De récentes observations suggèrent la persistance de symptômes neurologiques et neuropsychologiques à long terme suite à une infection par le SARS-CoV-2, actuellement décrit au sein du syndrome post-Covid-19. L'objectif de cet article est d'aborder les récentes données épidémiologiques et les données provenant d'études en neuro-imagerie. Finalement, une discussion est proposée quant aux récentes suggestions concernant l'existence de phénotypes distincts au sein du syndrome post-Covid-19.

Brain functional connectivity alterations associated with neuropsychological performance 6-9 months following SARS-CoV-2 infection.

Neuropsychological deficits and brain damage following SARS-CoV-2 infection are not well understood. Then, 116 patients, with either severe, moderate, or mild disease in the acute phase underwent neuropsychological and olfactory tests, as well as completed psychiatric and respiratory questionnaires at 223 ± 42 days postinfection. Additionally, a subgroup of 50 patients underwent functional magnetic resonance imaging. Patients in the severe group displayed poorer verbal episodic memory performances, and moderate patients had reduced mental flexibility. Neuroimaging revealed patterns of hypofunctional and hyperfunctional connectivities in severe patients, while only hyperconnectivity patterns were observed for moderate. The default mode, somatosensory, dorsal attention, subcortical, and cerebellar networks were implicated. Partial least squares correlations analysis confirmed specific association between memory, executive functions performances and brain functional connectivity. The severity of the infection in the acute phase is a predictor of neuropsychological performance 6-9 months following SARS-CoV-2 infection. SARS-CoV-2 infection causes long-term memory and executive dysfunctions, related to large-scale functional brain connectivity alterations.

Cognitive Deficits in the Acute Phase of COVID-19: A Review and Meta-Analysis.

This meta-analysis was conducted to quantify the risk of patients exhibiting cognitive deficits in the acute phase of COVID-19 at the time of the first variants (i.e., before the vaccine) and quantify the potential vulnerability of older patients and those who experienced more severe respiratory symptoms. To this end, we searched the LitCovid and EMBASE platforms for articles, including preprints, and included all studies (n = 48) that featured a measurement of cognition, which encompassed 2233 cases of COVID-19. Of these, 28 studies reported scores on global cognitive efficiency scales administered in the acute phase of COVID-19 (up to 3 months after infection). We were able to perform a meta-analysis of proportions on 24 articles (Npatients = 943), and a logistic regression on 18 articles (Npatients = 518). The meta-analysis for proportion indicated that 52.31% of patients with COVID-19 exhibited cognitive deficits in the acute phase. This high percentage, however, has to be interpreted taking in consideration the fact that the majority of patients were hospitalized, and some presented neurological complications, such as encephalopathy. A bootstrap procedure with random resampling revealed that an age of 59 was the threshold at which one would be more prone to present cognitive deficits. However, the severity of respiratory symptoms did not influence the scores on a global cognitive efficiency scale. Overall, our results indicated that neuropsychological deficits were a major consequence of the acute phase of the first forms of COVID-19.

Functional connectivity underlying cognitive and psychiatric symptoms in post-COVID-19 syndrome: is anosognosia a key determinant?

Lack of awareness of cognitive impairment (i.e. anosognosia) could be a key factor for distinguishing between neuropsychological post-COVID-19 condition phenotypes. In this context, the 2-fold aim of the present study was to (i) establish the prevalence of anosognosia for memory impairment, according to the severity of the infection in the acute phase and (ii) determine whether anosognosic patients with post-COVID syndrome have a different cognitive and psychiatric profile from nosognosic patients, with associated differences in brain functional connectivity. A battery of neuropsychological, psychiatric, olfactory, dyspnoea, fatigue and quality-of-life tests was administered 227.07 ± 42.69 days post-SARS-CoV-2 infection to 102 patients (mean age: 56.35 years, 65 men, no history of neurological, psychiatric, neuro-oncological or neurodevelopmental disorder prior to infection) who had experienced either a mild (not hospitalized; n = 45), moderate (conventional hospitalization; n = 34) or severe (hospitalization with intensive care unit stay and mechanical ventilation; n = 23) presentation in the acute phase. Patients were first divided into two groups according to the presence or absence of anosognosia for memory deficits (26 anosognosic patients and 76 nosognosic patients). Of these, 49 patients underwent an MRI. Structural images were visually analysed, and statistical intergroup analyses were then performed on behavioural and functional connectivity measures. Only 15.6% of patients who presented mild disease displayed anosognosia for memory dysfunction, compared with 32.4% of patients with moderate presentation and 34.8% of patients with severe disease. Compared with nosognosic patients, those with anosognosia for memory dysfunction performed significantly more poorly on objective cognitive and olfactory measures. By contrast, they gave significantly more positive subjective assessments of their quality of life, psychiatric status and fatigue. Interestingly, the proportion of patients exhibiting a lack of consciousness of olfactory deficits was significantly higher in the anosognosic group. Functional connectivity analyses revealed a significant decrease in connectivity, in the anosognosic group as compared with the nosognosic group, within and between the following networks: the left default mode, the bilateral somatosensory motor, the right executive control, the right salient ventral attention and the bilateral dorsal attention networks, as well as the right Lobules IV and V of the cerebellum. Lack of awareness of cognitive disorders and, to a broader extent, impairment of the self-monitoring brain system, may be a key factor for distinguishing between the clinical phenotypes of post-COVID syndrome with neuropsychological deficits.