Tag: cognitive impairment

Reduced ATP-to-phosphocreatine ratios in neuropsychiatric post-COVID condition: Evidence from 31P magnetic resonance spectroscopy

Abstract:

Background: Post-COVID condition (PCCo) affects 5-10% of individuals following SARS-CoV-2 infection, with cognitive disturbances being a major feature. Central hypotheses regarding its pathophysiology include disturbed cell energy metabolism and oxidative stress pointing to mitochondrial dysfunction. However, brain energy metabolism remains unexplored.

Methods: We investigated cerebral high-energy phosphate metabolism in 27 PCCo patients and 23 fully recovered controls using whole-brain 31P-MRSI at 3T. ATP/PCr ratios were quantified throughout the brain and analyzed with voxel-based and regional statistics including correlations with neuropsychological performance (Montreal Cognitive Assessment and Trail Making Test Part B). Statistical analysis employed voxel-wise comparisons with age as covariate, followed by region-of-interest analysis of cingulate cortex subdivisions.

Results: PCCo patients showed a significant cluster of reduced ATP/PCr ratios centered on the cingulate cortex. Regional analysis revealed consistent reductions across anterior (ACC), mid- (MCC), and posterior (PCC) cingulate cortices. Lower ATP/PCr ratios in the ACC specifically correlated with poorer cognitive performance. Exploratory analyses revealed a trend toward higher intracellular pH in the MCC with significant negative correlation between pH and ATP/PCr observed only in patients, suggesting disease-specific alterations in pH regulation and bioenergetic homeostasis. Subgroup analysis showed similar metabolic alterations in PCCo patients meeting ME/CFS criteria.

Conclusions: Our study provides first in vivo evidence of impaired brain energy metabolism in PCCo, with anterior cingulate dysfunction directly linked to cognitive impairment. The observed pH-ATP/PCr relationship suggests broader disruption of cellular bioenergetic regulation. These findings support mitochondrial dysfunction as a key pathophysiological mechanism and may inform targeted therapeutic strategies.

Source: Weber-Fahr W, Dommke S, Sack M, Alzein N, Becker R, Demirakca T, Ende G, Schilling C. Reduced ATP-to-phosphocreatine ratios in neuropsychiatric post-COVID condition: Evidence from 31P magnetic resonance spectroscopy. Biol Psychiatry. 2026 Jan 10:S0006-3223(26)00021-1. doi: 10.1016/j.biopsych.2026.01.004. Epub ahead of print. PMID: 41525818.  https://www.biologicalpsychiatryjournal.com/article/S0006-3223(26)00021-1/fulltext (Full text)

Systemic increase of AMPA receptors associated with cognitive impairment of Long COVID

Abstract:

Long COVID primarily presents with persistent cognitive impairment (Cog-LC), imposing a substantial and lasting global burden. Even after the pandemic, there remains a critical global need for diagnostic and therapeutic strategies targeting Cog-LC. Nevertheless, the underlying neural mechanisms remain poorly understood. Given the central role of synapses in brain function, investigation of synaptic molecular changes may provide vital insights into Cog-LC pathophysiology.

In this study, we used [11C]K-2 PET to characterize the density of AMPA receptors (AMPARs) on the post-synaptic cell surface, which are crucial synaptic components in brain signalling. Statistical parametrical mapping was used to spatially normalize and apply independent t-test for a voxel-based comparison.

We selected patients with Cog-LC (n = 30) based on Repeatable Battery for the Assessment of Neuropsychological Status assessed persistent cognitive impairment and healthy controls (n = 80) with no diagnosed neuropsychiatric disorders. The primary objective was to compare [11C]K-2 standardized uptake value ratio with white matter (SUVRWM) as a reference region between patients with Cog-LC and healthy controls, and to define the regional extent of differences. The secondary objective was to examine associations between [11C]K-2 SUVRWM and plasma concentrations of cytokines or chemokines.

As an exploratory objective, we tested whether [11C]K-2 PET data could distinguish Cog-LC from healthy controls using a partial least squares based classification algorithm. A voxel-based comparison (P < 0.05, T > 1.66, one-tailed, false discovery rate control) and a volume of interests analysis (P < 0.05, Bonferroni multiple comparison) demonstrated that increased index of AMPAR density in large parts of the brains of patients with Cog-LC compared with that in healthy controls.

A voxel-based correlation analysis also showed the brain regions where [11C]K-2 SUVRWM correlated positively with plasma TNFSF12 and negatively with plasma CCL2 concentrations.

A partial least squares model trained on the index of AMPAR density data demonstrated high diagnostic accuracy, achieving 100% sensitivity and 91.2% specificity. [11C]K-2 PET signal represents the index of AMPAR density on the post-synaptic neural cell surface, not on the glial cell surface.

A systemic increase in synaptic AMPARs across the brain may drive abnormal information processing in Cog-LC and, through excessive excitatory signalling, pose a risk of excitotoxic neuronal damage.

We derived the hypothesis that [11C]K-2 PET would be helpful in establishing a diagnostic framework for Cog-LC and that antagonists for cell surface AMPARs, such as perampanel, would be a potential therapeutic target. These hypotheses should be investigated in future large-scale clinical studies.

Source: Fujimoto Y, Abe H, Eiro T, Tsugawa S, Tanaka M, Hatano M, Nakajima W, Ichijo S, Arisawa T, Takada Y, Kimura K, Sano A, Hirahata K, Sasaki N, Kimura Y, Takahashi T. Systemic increase of AMPA receptors associated with cognitive impairment of long COVID. Brain Commun. 2025 Oct 1;7(5):fcaf337. doi: 10.1093/braincomms/fcaf337. PMID: 41036177; PMCID: PMC12483584. https://pmc.ncbi.nlm.nih.gov/articles/PMC12483584/ (Full text)

Exploration of Intersections and Divergences of Long COVID and Chronic Fatigue Syndrome

Abstract:

Background: Fatigue is the most common symptom of Long COVID (LC), defined by persistent or newly emerging symptoms that develop at least three months after an initial SARS-CoV-2 infection, in the absence of other identifiable cause. This study investigates the prevalence of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as a potential comorbidity of LC.

Methods: The study enrolled 37 adult controls with no documented SARS-CoV-2 infection and 32 individuals with a history of infection, categorized as LC-yes (with LC symptoms) and LC-no (without LC symptoms). ME/CFS diagnosis was based on the International Consensus Criteria (ICC).

Results: Among LC-yes cases, the most frequently reported symptoms included post-exertional malaise (PEM); neurosensory, perceptual, or motor disturbances; cognitive impairment; sleep disturbances; pain; impaired thermoregulation; and flu-like symptoms, all occurring significantly more than in the LC-no or control groups. All individuals in the LC-yes group reported PEM. ME/CFS was diagnosed in three LC-yes cases (18.8%), one LC-no case (6.7%), and four control subjects (10.8%), with no statistically significant differences observed among groups. Experiencing more than six symptoms during acute infection, such as fatigue, loss of taste or smell, headache, fever, cough, myalgia, sore throat, shortness of breath, rhinorrhea, and diarrhea, was associated with a twofold higher risk of developing LC.

Conclusion: A substantial proportion of LC-yes individuals experienced PEM; neurosensory, perceptual, or motor disturbances; cognitive impairment; and sleep disturbances, with rates significantly exceeding those in the LC-no and control groups. Nevertheless, only a minority of LC-yes cases (18.8%) satisfied criteria for the ME/CFS, and the prevalence did not significantly differ from LC-no and controls. These findings suggest that while many symptoms of LC overlap with those of ME/CFS, only a subset of LC cases meet established ME/CFS diagnostic criteria.

Source: Kouyoumdjian JA, Yamamoto LA, Graca CR. Exploration of Intersections and Divergences of Long COVID and Chronic Fatigue Syndrome. Cureus. 2025 Aug 20;17(8):e90607. doi: 10.7759/cureus.90607. PMID: 40978825; PMCID: PMC12448662. https://pmc.ncbi.nlm.nih.gov/articles/PMC12448662/ (Full text)

Abnormal Brain Activation Patterns in Patients With Post-Acute Sequelae of COVID-19 (PASC) During Recovery: A fNIRS Study

Abstract:

COVID-19 has increased the likelihood of cognitive impairment in patients with post-acute sequelae of COVID-19 (PASC). There is a lack of direct evidence regarding the working memory performance of mild patients during the recovery period. This study employed functional near-infrared spectroscopy (fNIRS) to construct a mixed effects model for PASC patients performing the N-back task, assessing brain activation levels and brain connectivity.

PASC patients exhibited abnormally low activation in the parietal lobe (β = −0.21) and abnormally high activation in the occipital lobe (β = 0.40). There was a significant reduction in brain connectivity within the frontal–parietal and frontal–occipital networks.

These findings suggest that PASC patients experience impaired fronto-parietal network connectivity, rely more on the visual cortex to compensate for executive function deficits, and use this as a compensatory mechanism to reduce overall cerebral blood oxygenation. This study provides evidence of altered brain activation patterns in PASC patients during the recovery period due to cognitive impairment.

Source: Y. Ran, S. Wu, S. Liu, et al., “ Abnormal Brain Activation Patterns in Patients With Post-Acute Sequelae of COVID-19 (PASC) During Recovery: A fNIRS Study,” Journal of Biophotonics (2025): e202500206, https://doi.org/10.1002/jbio.202500206. https://onlinelibrary.wiley.com/doi/epdf/10.1002/jbio.202500206

Comparative Study Between Cognitive Phenotypes of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Multiple Sclerosis

Abstract:

Objective: Cognitive impairments are one of the most common and disabling symptoms associated with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Here, we address the possibility of a specific cognitive profile inherent to ME/CFS. Due to the occurrence of cognitive deficits, fatigue, and pain in both pathologies, multiple sclerosis (MS) is a relevant comparison model. For this purpose, we carried out a comparative study between cognitive profiles of patients with ME/CFS and patients suffering from MS.

Methods: In total, 40 ME/CFS and 40 MS patients were included. A complete screening of all cognitive functions was carried out through an extensive battery of tests routinely used in clinical practice.

Results: ME/CFS and MS patients showed deficits in episodic memory retrieval, visual selective attention and reading speed. ME/CFS patients also elicited a lower level of performance than MS patients regarding consolidation. For both groups, levels of performance on these cognitive tests did not correlate with levels of fatigue, pain, and depression.

Conclusions: This study highlighted both similarities and differences in the cognitive profiles of ME/CFS and MS patients. While both groups exhibited deficits in episodic memory retrieval, visual selective attention, and reading speed, ME/CFS patients showed distinct impairment in consolidation processes. These cognitive deficits were not correlated with fatigue, pain, or depression, reinforcing the hypothesis of intrinsic cognitive dysfunction in ME/CFS. These findings define a specific cognitive phenotype for ME/CFS, which could improve diagnostic accuracy and therapeutic strategies. Future research, particularly in functional imaging, may elucidate the neurobiological mechanisms underlying these impairments.

Source: Aoun Sebaiti M, Oubaya N, Gounden Y, Samson C, Lechapt E, Wahab A, Creange A, Hainselin M, Authier FJ. Comparative Study Between Cognitive Phenotypes of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome and Multiple Sclerosis. Diagnostics (Basel). 2025 Feb 17;15(4):487. doi: 10.3390/diagnostics15040487. PMID: 40002638. https://www.mdpi.com/2075-4418/15/4/487 (Full text)

Cerebral microstructural alterations in Post-COVID-condition are related to cognitive impairment, olfactory dysfunction and fatigue

Abstract:

After contracting COVID-19, a substantial number of individuals develop a Post-COVID-Condition, marked by neurologic symptoms such as cognitive deficits, olfactory dysfunction, and fatigue. Despite this, biomarkers and pathophysiological understandings of this condition remain limited. Employing magnetic resonance imaging, we conduct a comparative analysis of cerebral microstructure among patients with Post-COVID-Condition, healthy controls, and individuals that contracted COVID-19 without long-term symptoms.

We reveal widespread alterations in cerebral microstructure, attributed to a shift in volume from neuronal compartments to free fluid, associated with the severity of the initial infection. Correlating these alterations with cognition, olfaction, and fatigue unveils distinct affected networks, which are in close anatomical-functional relationship with the respective symptoms.

Source: Hosp JA, Reisert M, Dressing A, Götz V, Kellner E, Mast H, Arndt S, Waller CF, Wagner D, Rieg S, Urbach H, Weiller C, Schröter N, Rau A. Cerebral microstructural alterations in Post-COVID-condition are related to cognitive impairment, olfactory dysfunction and fatigue. Nat Commun. 2024 May 18;15(1):4256. doi: 10.1038/s41467-024-48651-0. PMID: 38762609; PMCID: PMC11102465. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11102465/ (Full text)

Blood–brain barrier disruption and sustained systemic inflammation in individuals with long COVID-associated cognitive impairment

Abstract:

Vascular disruption has been implicated in coronavirus disease 2019 (COVID-19) pathogenesis and may predispose to the neurological sequelae associated with long COVID, yet it is unclear how blood–brain barrier (BBB) function is affected in these conditions. Here we show that BBB disruption is evident during acute infection and in patients with long COVID with cognitive impairment, commonly referred to as brain fog.

Using dynamic contrast-enhanced magnetic resonance imaging, we show BBB disruption in patients with long COVID-associated brain fog. Transcriptomic analysis of peripheral blood mononuclear cells revealed dysregulation of the coagulation system and a dampened adaptive immune response in individuals with brain fog.

Accordingly, peripheral blood mononuclear cells showed increased adhesion to human brain endothelial cells in vitro, while exposure of brain endothelial cells to serum from patients with long COVID induced expression of inflammatory markers.

Together, our data suggest that sustained systemic inflammation and persistent localized BBB dysfunction is a key feature of long COVID-associated brain fog.

Source: Greene C, Connolly R, Brennan D, Laffan A, O’Keeffe E, Zaporojan L, O’Callaghan J, Thomson B, Connolly E, Argue R, Martin-Loeches I, Long A, Cheallaigh CN, Conlon N, Doherty CP, Campbell M. Blood-brain barrier disruption and sustained systemic inflammation in individuals with long COVID-associated cognitive impairment. Nat Neurosci. 2024 Mar;27(3):421-432. doi: 10.1038/s41593-024-01576-9. Epub 2024 Feb 22. PMID: 38388736; PMCID: PMC10917679. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10917679/ (Full text)

Cognitive domains affected post-COVID-19; a systematic review and meta-analysis

Abstract:

Background and purpose: This review aims to characterize the pattern of post-COVID-19 cognitive impairment, allowing better prediction of impact on daily function to inform clinical management and rehabilitation.

Methods: A systematic review and meta-analysis of neurocognitive sequelae following COVID-19 was conducted, following PRISMA-S guidelines. Studies were included if they reported domain-specific cognitive assessment in patients with COVID-19 at >4 weeks post-infection. Studies were deemed high-quality if they had >40 participants, utilized healthy controls, had low attrition rates and mitigated for confounders.

Results: Five of the seven primary Diagnostic and Statistical Manual of Mental Disorders (DSM-5) cognitive domains were assessed by enough high-quality studies to facilitate meta-analysis. Medium effect sizes indicating impairment in patients post-COVID-19 versus controls were seen across executive function (standardised mean difference (SMD) -0.45), learning and memory (SMD -0.55), complex attention (SMD -0.54) and language (SMD -0.54), with perceptual motor function appearing to be impacted to a greater degree (SMD -0.70). A narrative synthesis of the 56 low-quality studies also suggested no obvious pattern of impairment.

Conclusions: This review found moderate impairments across multiple domains of cognition in patients post-COVID-19, with no specific pattern. The reported literature was significantly heterogeneous, with a wide variety of cognitive tasks, small sample sizes and disparate initial disease severities limiting interpretability. The finding of consistent impairment across a range of cognitive tasks suggests broad, as opposed to domain-specific, brain dysfunction. Future studies should utilize a harmonized test battery to facilitate inter-study comparisons, whilst also accounting for the interactions between COVID-19, neurological sequelae and mental health, the interplay between which might explain cognitive impairment.

Source: Fanshawe JB, Sargent BF, Badenoch JB, Saini A, Watson CJ, Pokrovskaya A, Aniwattanapong D, Conti I, Nye C, Burchill E, Hussain ZU, Said K, Kuhoga E, Tharmaratnam K, Pendered S, Mbwele B, Taquet M, Wood GK, Rogers JP, Hampshire A, Carson A, David AS, Michael BD, Nicholson TR, Paddick SM, Leek CE. Cognitive domains affected post-COVID-19; a systematic review and meta-analysis. Eur J Neurol. 2024 Feb 20:e16181. doi: 10.1111/ene.16181. Epub ahead of print. PMID: 38375608. https://onlinelibrary.wiley.com/doi/10.1111/ene.16181 (Full text)

Impact of sleep disruption on cognitive function in patients with postacute sequelae of SARS-CoV-2 infection: initial findings from a Neuro-COVID-19 clinic

Abstract:

Introduction: Fatigue, brain fog, and sleep disturbance are among the most common symptoms of postacute sequelae of SARS-CoV-2 infection (PASC). We sought to determine the impact of sleep disruption on cognition and quality of life in patients with neurologic manifestations of PASC (Neuro-PASC).
Methods: Thirty-nine patients were recruited from Neuro-COVID-19 clinic. Mean age was 48.1 years, 71.8% were female, and 82% were never hospitalized for COVID-19. Patients were evaluated via clinical assessment, quality-of-life measures in domains of cognitive function, fatigue, sleep disturbance, anxiety, and depression, NIH Toolbox cognitive tests, and 7 days of wrist actigraphy.
Results: The median number of neurologic symptoms attributed to PASC was 6, with brain fog being the most common in 89.7%. Regarding non-neurologic symptoms, 94.9% complained of fatigue and 74.4% of insomnia. Patients reported significant impairment in all quality-of-life domains and performed worse in a task of attention compared to a normative US population. Actigraphy showed Neuro-PASC patients had lower sleep efficiency, longer sleep latency (both p < 0.001), and later sleep midpoint (p = 0.039) compared to 71 age-matched healthy controls with no PASC history. Self-reported cognitive symptoms correlated with the severity of fatigue (p < 0.001), anxiety (p = 0.05), and depression (p < 0.01). Objective evidence of sleep disruption measured by wakefulness after sleep onset, sleep efficiency, and latency were associated with decreased performance in attention and processing speed.
Conclusion: Prospective studies including larger populations of patients are needed to fully determine the interplay of sleep disruption on the cognitive function and quality of life of patients with PASC.

Source: Kathryn J Reid, Louis T Ingram, Millenia Jimenez, Zachary S Orban, Sabra M Abbott, Daniela Grimaldi, Kristen L Knutson, Phyllis C Zee, Igor J Koralnik, Mathew B Maas, Impact of sleep disruption on cognitive function in patients with postacute sequelae of SARS-CoV-2 infection: initial findings from a Neuro-COVID-19 clinic, SLEEP Advances, Volume 5, Issue 1, 2024, zpae002, https://doi.org/10.1093/sleepadvances/zpae002 https://academic.oup.com/sleepadvances/article/5/1/zpae002/7517273 (Full text)

Impact of sleep disruption on cognitive function in patients with post-acute sequelae of SARS-CoV-2 infection: Initial findings from a Neuro-COVID-19 clinic

Abstract:

Introduction: Fatigue, brain fog and sleep disturbance are among the most common symptoms of post-acute sequelae of SARS-CoV-2 infection (PASC). We sought to determine the impact of sleep disruption on cognition and quality-of-life in patients with neurologic manifestations of PASC (Neuro-PASC).

Methods: Thirty-nine patients were recruited from Neuro-COVID-19 clinic. Mean age was 48.1 years, 71.8% were female, and 82% were never hospitalized for COVID-19. Patients were evaluated via clinical assessment, quality-of-life measures in domains of cognitive function, fatigue, sleep disturbance, anxiety, and depression, NIH toolbox cognitive tests, and 7 days of wrist actigraphy.

Results: The median number of neurologic symptoms attributed to PASC was 6, with brain fog being the most common in 89.7%. Regarding non-neurologic symptoms, 94.9% complained of fatigue and 74.4% of insomnia. Patients reported significant impairment in all quality-of-life domains and performed worse in a task of attention compared to a normative US population. Actigraphy showed Neuro-PASC patients had lower sleep efficiency, longer sleep latency (both p<0.001) and later sleep midpoint (p=0.039) compared to 71 age-matched healthy controls with no PASC history. Self-reported cognitive symptoms correlated with severity of fatigue (p<0.001), anxiety (p=0.05), and depression (p<0.01). Objective evidence of sleep disruption measured by wakefulness after sleep onset, sleep efficiency and latency were associated with decreased performance in attention and processing speed.

Conclusion: Prospective studies including larger populations of patients are needed to fully determine the interplay of sleep disruption on the cognitive function and quality of life of patients with PASC.

Source: Kathryn J Reid, Louis T Ingram, Millenia Jimenez, Zachary S Orban, Sabra M Abbott, Daniela Grimaldi, Kristen L Knutson, Phyllis C Zee, Igor J Koralnik, Mathew B Maas, Impact of sleep disruption on cognitive function in patients with post-acute sequelae of SARS-CoV-2 infection: Initial findings from a Neuro-COVID-19 clinic, SLEEP Advances, 2024;, zpae002, https://doi.org/10.1093/sleepadvances/zpae002 https://academic.oup.com/sleepadvances/advance-article/doi/10.1093/sleepadvances/zpae002/7517273 (Full text available as PDF file)