Hippocampal alterations after SARS-CoV-2 infection: A systematic review.

SARS-CoV-2 infection produces a wide range of symptoms. Some of the structural changes caused by the virus in the nervous system are found in the medial temporal lobe, and several neuropsychological sequelae of COVID-19 are related to the function of the hippocampus. The main objective of the systematic review is to update and further analyze the existing evidence of hippocampal and related cortices' structural and functional alterations due to SARS-CoV-2 infection. Both clinical and preclinical studies that used different methodologies to explore the effects of this disease at different stages and grades of severity were considered, besides exploring related cognitive and emotional symptomatology. A total of 24 studies were identified by searching in SCOPUS, Web Of Science (WOS), PubMed, and PsycInfo databases up to October 3rd, 2022. Thirteen studies were performed in clinical human samples, 9 included preclinical animal models, 3 were performed post-mortem, and 1 included both post-mortem and preclinical samples. Alterations in the hippocampus were detected in the acute stage and after several months of infection. Clinical studies revealed alterations in hippocampal connectivity and metabolism. Memory alterations correlated with altered metabolic profiles or changes in grey matter volumes. Hippocampal human postmortem and animal studies observed alterations in neurogenesis, dendrites, and immune response, besides high apoptosis and neuroinflammation. Preclinical studies reported the viral load in the hippocampus. Olfactory dysfunction was associated with alterations in brain functionality. Several clinical studies revealed cognitive complaints, neuropsychological alterations, and depressive and anxious symptomatology.

Cognitive impairment in young adults with post COVID-19 syndrome.

In this study, we aimed to examine different cognitive domains in a large sample of patients with post COVID-19 syndrome. Two hundred and fourteen patients, 85.04% women, ranged 26 to 64 years (mean = 47.48 years) took part in this investigation. Patients' processing speed, attention, executive functions and various language modalities were examined online using a comprehensive task protocol designed for this research. Alteration in some of the tasks was observed in 85% of the participants, being the attention and executive functions tests the ones that show the highest percentage of patients with severe impairment. Positive correlations were observed between the age of the participants in almost all the tasks assessed, implying better performance and milder impairment with increasing age. In the comparisons of patients according to age, the oldest patients were found to maintain their cognitive functions relatively preserved, with only a mild impairment in attention and speed processing, while the youngest showed the most marked and heterogeneous cognitive impairment. These results confirm the subjective complaints in patients with post COVID-19 syndrome and, thanks to the large sample size, allow us to observe the effect of patient age on performance, an effect never reported before in patients with these characteristics.