Infection with COVID‐19 is no longer a public emergency: But what about degenerative dementia?

Abstract

Although no longer considered a public health threat, post‐COVID cognitive syndrome continues to impact on a considerable proportion of individuals who were infected with COVID‐19. Recent studies have also suggested that COVID may be represent a critical risk factor for the development of Alzheimer's disease (AD). We compared 17 COVID patients with 20 controls and evaluated the effects of COVID‐19 on general cognitive performance, hippocampal volume, and connections using structural and seed‐based connectivity analysis. We showed that COVID patients exhibited considerably worse cognitive functioning and increased hippocampal connectivity supported by the strong correlation between hippocampal connectivity and cognitive scores. Our findings of higher hippocampal connectivity with no observable hippocampal morphological changes even in mild COVID cases may be represent evidence of a prestructural compensatory mechanism for stimulating additional neuronal resources to combat cognitive dysfunction as recently shown for the prodromal stages of degenerative cognitive disorders. Our findings may be also important in light of recent data showing that other viral infections as well as COVID may constitute a critical risk factor for the development of AD. To our knowledge, this is the first study that investigated network differences in COVID patients, with a particular focus on compensatory hippocampal connectivity.

On the merits and potential of advanced neuroimaging techniques in COVID-19: A scoping review

“…Reduced connectivity between the right head of hippocampus and regions of the dorsal attention network was observed in non-hospitalized patients with long-COVID compared to healthy controls approximately eleven months after the infection ( Díez-Cirarda et al, 2023 ). In contrast, another study reported enhanced connectivity between subfields of the hippocampus and other regions of the (para)limbic network in recovered COVID-19 patients ( Yulug et al, 2023 ).…”

The functional role of the pulvinar in discriminating between objective and subjective cognitive impairment in major depressive disorder

“…Furthermore, previous cognition studies of depressive patients have primarily focused on alterations in the hippocampus, amygdala, and cingulate gyrus, without considering functional alterations in other critical subcortical structures, such as the thalamus, and especially the pulvinar 14 . Such alterations may indicate a critical dynamic phase associated with subtle pathophysiological changes occurring before the manifestation of structural changes 15–17 . From that perspective, functional connectivity analysis is a valuable method for examining voxel‐wise functional magnetic resonance imaging (MRI) signals and that identifies functionally related brain areas and distributed networks.…”

“… 14 Such alterations may indicate a critical dynamic phase associated with subtle pathophysiological changes occurring before the manifestation of structural changes. 15 , 16 , 17 From that perspective, functional connectivity analysis is a valuable method for examining voxel‐wise functional magnetic resonance imaging (MRI) signals and that identifies functionally related brain areas and distributed networks. This therefore justifies an investigation of the differences between amnestic and other depressed individuals.…”

Patients Recovering from COVID-19 who Presented Anosmia During their Acute Episode have Behavioral, Functional, and Structural Brain Alterations

“…1,2 However, research has failed to find a specific marker of neuroinflammation, 67 or structural alterations were not found in other samples. 48,62 As with functional alterations, the severity of the acute episode and the presence of persistent symptoms are more closely related to structural alterations, primarily in white matter integrity. 66,68…”

“…Most studies investigating functional brain activity in patients recovered from COVID-19 have been conducted using resting-state methods. Alterations in signal properties and functional connectivity have been found in COVID-19 patients, 55,56 and have been associated with hospitalization, 57 and persistent symptoms such as headaches, 58 persistent olfactory dysfunction 48,59,60 and other behavioral markers such as working memory performance, 61,62 anxiety, 63 psychotic-like experiences in adolescents, 64 and post-traumatic stress symptoms. 65 Also, some studies found no functional alteration in recovered COVID-19 patients.…”