The therapeutic potential of non-invasive brain stimulation for the treatment of Long-COVID-related cognitive fatigue

Multidisciplinary collaborative guidance on the assessment and treatment of patients with Long COVID: A compendium statement

BACKGROUND

In 2021, the American Academy of Physical Medicine and Rehabilitation established the Multi-Disciplinary Post-Acute Sequelae of SARS-CoV-2 Infection Collaborative to provide guidance from established Long COVID clinics for the evaluation and management of Long COVID. The collaborative previously published eight Long COVID consensus guidance statements using a primarily symptom-based approach. However, Long COVID symptoms most often do not occur in isolation.

AIMS

This compendium aims to equip clinicians with an efficient, up-to-date clinical resource for evaluating and managing adults experiencing Long COVID symptoms. The primary intended audience includes physiatrists, primary care physicians, and other clinicians who provide first-line assessment and management of Long COVID symptoms, especially in settings where subspecialty care is not readily available. This compendium provides a holistic framework for assessment and management, symptom-specific considerations, and updates on prevalence, health equity, disability considerations, pathophysiology, and emerging evidence regarding treatments under investigation. Because Long COVID closely resembles other infection-associated chronic conditions (IACCs) such as myalgic encephalomyelitis/chronic fatigue syndrome, the guidance in this compendium may also be helpful for clinicians managing these related conditions.

METHODS

Guidance in this compendium was developed by the collaborative's established modified Delphi approach. The collaborative is a multidisciplinary group whose members include physiatrists, primary care physicians, pulmonologists, cardiologists, psychiatrists, neuropsychologists, neurologists, occupational therapists, physical therapists, speech and language pathologists, patients, and government representatives. Over 40 Long COVID centers are represented in the collaborative.

RESULTS

Long COVID is defined by the National Academies of Sciences, Engineering, and Medicine as "an IACC that occurs after SARS-CoV-2 infection and is present for at least 3 months as a continuous, relapsing and remitting, or progressive disease state that affects one or more organ systems." The current global prevalence of Long COVID is estimated to be 6%. Higher prevalence has been identified among female gender, certain racial and ethnic groups, and individuals who live in nonurban areas. However, anyone can develop Long COVID after being infected with the SARS-CoV-2 virus. Long COVID can present as a wide variety of symptom clusters. The most common symptoms include exaggerated fatigue and diminished energy windows, postexertional malaise (PEM)/postexertional symptom exacerbation (PESE), cognitive impairment (brain fog), dysautonomia, pain/myalgias, and smell and taste alterations. Holistic assessment should include a traditional history, physical examination, and additional diagnostic testing, as indicated. A positive COVID-19 test during acute SARS-CoV-2 infection is not required to diagnose Long COVID, and currently, there is no single laboratory finding that is definitively diagnostic for confirming or ruling out the diagnosis of Long COVID. A basic laboratory assessment is recommended for all patients with possible Long COVID, and consideration for additional labs and diagnostic procedures is guided by the patient's specific symptoms. Current management strategies focus on symptom-based supportive care. Critical considerations include energy conservation strategies and addressing comorbidities and modifiable risk factors. Additionally, (1) it is essential to validate the patient's experience and provide reassurance that their symptoms are being taken seriously because many patients have had their symptoms dismissed by loved ones and clinicians; (2) physical activity recommendations must be carefully tailored to the patient's current activity tolerance because overly intense activity can trigger PEM/PESE and worsened muscle damage; and (3) treatment recommendations should be delivered with humility because there are many persistent unknowns related to Long COVID. To date, there are limited data to guide medication management specifically in the context of Long COVID. As such, medication use generally follows standard practice regarding indications and dosing, with extra attention to prioritize (1) patient preference via shared decision-making and (2) cautious use of medications that may improve some symptoms (eg, cognitive/attention impairment) but may worsen other symptoms (eg, PEM/PESE). Numerous clinical trials are investigating additional treatments. The return-to-work process for individuals with Long COVID can be challenging because symptoms can fluctuate, vary in nature, affect multiple functional areas (eg, physical and cognitive), and often manifest as an "invisible disability" that may not be readily acknowledged by employers or coworkers. Clinicians can help patients return to work by identifying suitable workplace accommodations and resources, providing necessary documentation, and recommending occupational or vocational therapy when needed. If these efforts are unsuccessful and work significantly worsens Long COVID symptoms or impedes recovery, applying for disability may be warranted. Long COVID is recognized as a potential disability under the Americans with Disabilities Act.

CONCLUSION

To contribute to the overall health and well-being for all patients, Long COVID care should be delivered in a holistic manner that acknowledges challenges faced by the patient and uncertainties in the field. For more detailed information on assessment and management of specific Long COVID symptoms, readers can reference the collaborative's symptom-specific consensus guidance statements.

Unraveling brain fog in post-COVID syndrome: Relationship between subjective cognitive complaints and cognitive function, fatigue, and neuropsychiatric symptoms

BACKGROUND AND PURPOSE

"Brain fog" is a frequent and disabling symptom that can occur after SARS-CoV-2 infection. However, its clinical characteristics and the relationships among brain fog and objective cognitive function, fatigue, and neuropsychiatric symptoms (depression, anxiety) are still unclear. In this study, we aimed to examine the characteristics of brain fog and to understand how fatigue, cognitive performance, and neuropsychiatric symptoms and the mutual relationships among these variables influence subjective cognitive complaints.

METHODS

A total of 170 patients with cognitive complaints in the context of post-COVID syndrome were evaluated using a comprehensive neuropsychological protocol. The FLEI scale was used to characterize subjective cognitive complaints. Correlation analysis, regression machine-learning algorithms, and mediation analysis were calculated.

RESULTS

Cognitive complaints were mainly attention and episodic memory symptoms, while executive functions (planning) issues were less often reported. The FLEI scale, a mental ability questionnaire, showed high correlations with a fatigue scale and moderate correlations with the Stroop test, and anxiety and depressive symptoms. Random forest algorithms showed an R2 value of 0.409 for the prediction of FLEI score, with several cognitive tests, fatigue and depression being the best variables used in the prediction. Mediation analysis showed that fatigue was the main mediator between objective and subjective cognition, while the effect of depression was indirect and mediated through fatigue.

CONCLUSIONS

Brain fog associated with COVID-19 is mainly characterized by attention and episodic memory, and fatigue, which is the main mediator between objective and subjective cognition. Our findings contribute to understanding the pathophysiology of brain fog and emphasize the need to unravel the main mechanisms underlying brain fog, considering several aspects.

Vagal nerve stimulation for the management of long COVID symptoms

This review investigates the therapeutic potential of vagal nerve stimulation (VNS) in managing long COVID, a condition marked by persistent symptoms following acute SARS-CoV-2 infection. Long COVID manifests as ongoing fatigue, cognitive impairment, and autonomic dysfunction, hypothesized to arise from sustained inflammatory and neurological dysregulation. The vagus nerve, central to modulating systemic inflammation and autonomic homeostasis, represents a promising therapeutic target for symptom alleviation through VNS. A comprehensive literature search was conducted across PubMed, Scopus, and Web of Science to identify studies evaluating VNS in the context of long COVID. Preliminary evidence from small-scale pilot studies suggests VNS may attenuate systemic inflammation through activation of the cholinergic anti-inflammatory pathway (CAP), thus restoring autonomic balance and ameliorating symptoms such as fatigue, cognitive dysfunction, and anxiety. In targeting the inflammatory cascade that underlies both acute COVID-19 pathophysiology and its prolonged sequelae, VNS holds potential as an innovative intervention for persistent post-viral symptoms. While these initial findings indicate promise, current data remain limited in scope and robustness, underscoring the need for larger, controlled trials to validate the efficacy and mechanisms of VNS in long COVID management. Establishing a clearer understanding of VNS's impact on inflammation and autonomic regulation in this context is crucial to inform clinical guidelines and therapeutic strategies for long COVID, potentially offering a targeted approach for mitigating this disabling condition.

Long COVID patients' brain activation is suppressed during walking and severer symptoms lead to stronger suppression

This research aims to study the factors contributing to Long COVID and its effects on motor and cognitive brain regions using population surveys and brain imaging. The goal is to provide new insights into the neurological effects of the illness and establish a basis for addressing neuropsychiatric symptoms associated with Long COVID. Study 1 used a cross-sectional design to collect data on demographic characteristics and factors related to Long COVID symptoms in 551 participants. In Study 2, subjects with Long COVID and SARS-CoV-2 uninfected individuals underwent fNIRS monitoring while performing various tasks. Study 1 found that gender, age, BMI, Days since the first SARS-CoV-2 infection, and Symptoms at first onset influenced Long COVID performance. Study 2 demonstrated that individuals in the SARS-CoV-2 uninfected group exhibited greater activation of cognitive function-related brain regions than those in the Long COVID group while performing a level walking task. Furthermore, individuals in the Long COVID group without functional impairment displayed higher activation of brain regions associated with motor function during a weight-bearing walking task than those with functional impairment. Among individuals with Long COVID, those with mild symptoms at onset exhibited increased activation of brain regions linked to motor and cognitive function relative to those with moderate symptoms at onset. Individuals with Long COVID exhibited decreased activation in brain regions associated with cognitive and motor function compared to SARS-CoV-2 uninfected individuals. Moreover, those with more severe initial symptoms or functional impairment displayed heightened inhibition in these brain regions.

Associations Between Brain Morphology, Inflammatory Markers, and Symptoms of Fatigue, Depression, or Anxiety in Active and Remitted Crohn's Disease

BACKGROUND

Fatigue and psychosocial impairments are highly prevalent in IBD, particularly during active disease. Disturbed brain-gut interactions may contribute to these symptoms. This study examined associations between brain structure, faecal calprotectin, and symptoms of fatigue, depression, and anxiety in persons with Crohn's disease [CD] in different disease states.

METHODS

In this prospective observational study, n = 109 participants [n = 67 persons with CD, n = 42 healthy controls] underwent cranial magnetic resonance imaging, provided stool samples for analysis of faecal calprotectin, and completed questionnaires to assess symptoms of fatigue, depression, and anxiety. We analysed differences in grey matter volume [GMV] between patients and controls, and associations between regional GMV alterations, neuropsychiatric symptoms, and faecal calprotectin.

RESULTS

Symptoms of fatigue, depression, and anxiety were increased in patients with CD compared with controls, with highest scores in active CD. Patients exhibited regionally reduced GMV in cortical and subcortical sensorimotor regions, occipitotemporal and medial frontal areas. Regional GMV differences showed a significant negative association with fatigue, but not with depression or anxiety. Subgroup analyses revealed symptom-GMV associations for fatigue in remitted but not in active CD, whereas fatigue was positively associated with faecal calprotectin in active but not in remitted disease.

CONCLUSION

Our findings support disturbed brain-gut interactions in CD which may be particularly relevant for fatigue during remitted disease. Reduced GMV in the precentral gyrus and other sensorimotor areas could reflect key contributions to fatigue pathophysiology in CD. A sensorimotor model of fatigue in CD could also pave the way for novel treatment approaches.

Slow-Paced Breathing Intervention in Healthcare Workers Affected by Long COVID: Effects on Systemic and Dysfunctional Breathing Symptoms, Manual Dexterity and HRV

BACKGROUND

Many COVID-19 survivors still experience long-term effects of an acute infection, most often characterised by neurological, cognitive and psychiatric sequelae. The treatment of this condition is challenging, and many hypotheses have been proposed. Non-invasive vagus nerve stimulation using slow-paced breathing (SPB) could stimulate both central nervous system areas and parasympathetic autonomic pathways, leading to neuromodulation and a reduction in inflammation. The aim of the present study was to evaluate physical, cognitive, emotional symptoms, executive functions and autonomic cardiac modulation after one month of at-home slow breathing intervention.

METHODS

6655 healthcare workers (HCWs) were contacted via a company email in November 2022, of which N = 58 HCWs were enrolled as long COVID (cases) and N = 53 HCWs as controls. A baseline comparison of the two groups was performed. Subsequently each case was instructed on how to perform a resonant SPB using visual heart rate variability (HRV) biofeedback. They were then given a mobile video tutorial breathing protocol and asked to perform it three times a day (morning, early afternoon and before sleep). N = 33 cases completed the FU. At T0 and T1, each subject underwent COVID-related, psychosomatic and dysfunctional breathing questionnaires coupled with heart rate variability and manual dexterity assessments.

RESULTS

After one month of home intervention, an overall improvement in long-COVID symptoms was observed: confusion/cognitive impairment, chest pain, asthenia, headache and dizziness decreased significantly, while only a small increase in manual dexterity was found, and no relevant changes in cardiac parasympathetic modulation were observed.

Research evidence on the management of the cognitive impairment component of the post-COVID condition: a qualitative systematic review

BACKGROUND

Cognitive impairment (CI) is one of the most prevalent and burdensome consequences of COVID-19 infection, which can persist up to months or even years after remission of the infection. Current guidelines on post-COVID CI are based on available knowledge on treatments used for improving CI in other conditions. The current review aims to provide an updated overview of the existing evidence on the efficacy of treatments for post-COVID CI.

METHODS

A systematic literature search was conducted for studies published up to December 2023 using three databases (PubMed-Scopus-ProQuest). Controlled and noncontrolled trials, cohort studies, case series, and reports testing interventions on subjects with CI following COVID-19 infection were included.

RESULTS

After screening 7790 articles, 29 studies were included. Multidisciplinary approaches, particularly those combining cognitive remediation interventions, physical exercise, and dietary and sleep support, may improve CI and address the different needs of individuals with post-COVID-19 condition. Cognitive remediation interventions can provide a safe, cost-effective option and may be tailored to deficits in specific cognitive domains. Noninvasive brain stimulation techniques and hyperbaric oxygen therapy showed mixed and preliminary results. Evidence for other interventions, including pharmacological ones, remains sparse. Challenges in interpreting existing evidence include heterogeneity in study designs, assessment tools, and recruitment criteria; lack of long-term follow-up; and under-characterization of samples in relation to confounding factors.

CONCLUSIONS

Further research, grounded on shared definitions of the post-COVID condition and on the accurate assessment of COVID-related CI, in well-defined study samples and with longer follow-ups, is crucial to address this significant unmet need.

Anodal tDCS over the motor cortex improves pain but not physical function in chronic chikungunya arthritis: Randomized controlled trial

BACKGROUND

Chikungunya virus (CHIKV) is a globally prevalent pathogen, with outbreaks occurring in tropical regions. Chronic pain is the main symptom reported and is associated with decreased mobility and disability. Transcranial direct current stimulation (tDCS) is emerging as a new therapeutic tool for chronic arthralgia.

OBJECTIVE

To evaluate the effectiveness of 10 consecutive sessions of anodal tDCS on pain (primary outcome) in participants with chronic CHIKV arthralgia. Secondary outcomes included functional status, quality of life, and mood.

METHODS

In this randomized, double-blind, placebo-controlled trial, 30 participants with chronic CHIKV arthralgia were randomly assigned to receive either active (n = 15) or sham (n = 15) tDCS. The active group received 10 consecutive sessions of tDCS over M1 using the C3/Fp2 montage (2 mA for 20 min). Visual analog scale of pain (VAS), health assessment questionnaire (HAQ), short-form 36 health survey (SF-36), pain catastrophizing scale, Hamilton anxiety scale (HAS), timed up and go (TUG) test, lumbar dynamometry, 30-s arm curl and 2-min step test were assessed at baseline, day 10 and at 2 follow-up visits.

RESULTS

There was a significant interaction between group and time on pain (p = 0.03; effect size 95 % CI 0.9 (-1.67 to -0.16), with a significant time interaction (p = 0.0001). There was no interaction between time and group for the 2-minute step test (p = 0.18), but the groups differed significantly at day 10 (p = 0.01), first follow-up (p = 0.01) and second follow-up (p = 0.03). HAQ and SF-36 improved but not significantly. There was no significant improvement in mental health, and physical tests.

CONCLUSION

tDCS appears to be a promising intervention for reducing pain in participants with chronic CHIKV arthralgia, although further research is needed to confirm these findings and explore potential long-term benefits.

TRIAL REGISTRATION

Brazilian Registry of Clinical Trials (ReBEC): RBR-245rh7.

Decoding Post-Viral Fatigue: The Basal Ganglia's Complex Role in Long-COVID

Long-COVID afflicts millions with relentless fatigue, disrupting daily life. The objective of this narrative review is to synthesize current evidence on the role of the basal ganglia in long-COVID fatigue, discuss potential mechanisms, and highlight promising therapeutic interventions. A comprehensive literature search was conducted using PubMed, Scopus, and Web of Science databases. Mounting evidence from PET, MRI, and functional connectivity data reveals basal ganglia disturbances in long-COVID exhaustion, including inflammation, metabolic disruption, volume changes, and network alterations focused on striatal dopamine circuitry regulating motivation. Theories suggest inflammation-induced signaling disturbances could impede effort/reward valuation, disrupt cortical-subcortical motivational pathways, or diminish excitatory input to arousal centers, attenuating drive initiation. Recent therapeutic pilots targeting basal ganglia abnormalities show provisional efficacy. However, heterogeneous outcomes, inconsistent metrics, and perceived versus objective fatigue discrepancies temper insights. Despite the growing research, gaps remain in understanding the precise pathways linking basal ganglia dysfunction to fatigue and validating treatment efficacy. Further research is needed to advance understanding of the basal ganglia's contribution to long-COVID neurological sequelae and offer hope for improving function across the expanding affected population.

Artificial Intelligence's Transformative Role in Illuminating Brain Function in Long COVID Patients Using PET/FDG

Cutting-edge brain imaging techniques, particularly positron emission tomography with Fluorodeoxyglucose (PET/FDG), are being used in conjunction with Artificial Intelligence (AI) to shed light on the neurological symptoms associated with Long COVID. AI, particularly deep learning algorithms such as convolutional neural networks (CNN) and generative adversarial networks (GAN), plays a transformative role in analyzing PET scans, identifying subtle metabolic changes, and offering a more comprehensive understanding of Long COVID's impact on the brain. It aids in early detection of abnormal brain metabolism patterns, enabling personalized treatment plans. Moreover, AI assists in predicting the progression of neurological symptoms, refining patient care, and accelerating Long COVID research. It can uncover new insights, identify biomarkers, and streamline drug discovery. Additionally, the application of AI extends to non-invasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS), which have shown promise in alleviating Long COVID symptoms. AI can optimize treatment protocols by analyzing neuroimaging data, predicting individual responses, and automating adjustments in real time. While the potential benefits are vast, ethical considerations and data privacy must be rigorously addressed. The synergy of AI and PET scans in Long COVID research offers hope in understanding and mitigating the complexities of this condition.

Mitochondrial oxidative stress, mitochondrial ROS storms in long COVID pathogenesis

Significance

This review discusses the coronavirus disease 2019 (COVID-19) pathophysiology in the context of diabetes and intracellular reactions by COVID-19, including mitochondrial oxidative stress storms, mitochondrial ROS storms, and long COVID.

Recent advances

The long COVID is suffered in ~10% of the COVID-19 patients. Even the virus does not exist, the patients suffer the long COVID for even over a year, This disease could be a mitochondria dysregulation disease.

Critical issues

Patients who recover from COVID-19 can develop new or persistent symptoms of multi-organ complications lasting weeks or months, called long COVID. The underlying mechanisms involved in the long COVID is still unclear. Once the symptoms of long COVID persist, they cause significant damage, leading to numerous, persistent symptoms.

Future directions

A comprehensive map of the stages and pathogenetic mechanisms related to long COVID and effective drugs to treat and prevent it are required, which will aid the development of future long COVID treatments and symptom relief.

The Hidden Impact of Covid-19 on Memory: Disclosing Subjective Complaints

Objective

A significant body of research has suggested that the contraction of SARS-CoV-2 may cause memory impairment, even in the months following recovery. In this regard, studies suggest that COVID-19 predominantly targets structures and cortices within the temporal lobe, and the hippocampus, a critical brain structure for memory and spatial navigation.The purpose of this study was to investigate the potential impact of the COVID-19 pandemic on subjective memory complaints, which represent an individual's perception of subtle changes in memory in the absence of an objective memory impairment.

Method

to explore how the COVID-19 pandemic may affect subjective memory complaints, we incorporated ad hoc self-reported measures of subjective memory complaints, the "Subjective Memory Complaints Questionnaire" (SMCQ) and the "Prospective and Retrospective Memory Questionnaire" (PRMQ), in our cross-sectional study. Both measures referred to two periods: the pre-pandemic period (T0) and the moment of survey administration (T1) (December 28th, 2021, to February 6th, 2022).

Results

207 Italian participants accessed the survey, out of which 189 participants were included in the final sample. The majority of the participants were females, and their age ranged from 55 to 65 years. The study revealed a significant increase in the total PRMQ score at T1 compared to T0 (p = 0.02). However, no significant differences were found between PRMQ and SMCQ scores of COVID-19-negative individuals and those who tested positive for COVID-19 in the last 12 months from the date of completing the survey. McNemar's test showed a statistically significant increase in the score of item 1 ("Do you think that you have a memory problem?" (p = 0.016) and item 10 ("Do you lose objects more often than you did previously") (0.019) of the SMCQ, while for the PRMQ, significant increases were found in several individual items.

Conclusions

our study suggests that subjective memory complaints increased during the pandemic, potentially due to the compound effects of stress and social isolation, rather than solely due to COVID-19 infection. Although a marginal association between COVID-19 and reported prospective memory issues was detected, further investigation is warranted to understand its persistent effects.

Brain State-Dependent Non-Invasive Neurostimulation with EEG Feedback: Achievements and Prospects (Review)

Non-invasive brain stimulation with electroencephalogram (EEG) feedback is an intensively developing and promising area of neurophysiology. The review considers the literature data over the past 5 years on the achievements and promising directions for the further development of this research line. Modern data on the developed approaches to the practical use of various types of brain state-dependent adaptive neurostimulation with EEG feedback were analyzed. The main attention is paid to the studies using non-invasive magnetic and electrical stimulation, as well as acoustic and audiovisual stimulation. The paper considers the possibilities and prospects for using these technologies in clinical medicine. The results of the authors' own research are presented.

Sequelae of long COVID, known and unknown: A review of updated information

Over three years have passed since the COVID-19 pandemic started. The dangerousness and impact of COVID-19 should definitely not be ignored or underestimated. Other than the symptoms of acute infection, the long-term symptoms associated with SARS-CoV-2 infection, which are referred to here as "sequelae of long COVID (LC)", are also a conspicuous global public health concern. Although such sequelae were well-documented, the understanding of and insights regarding LC-related sequelae remain inadequate due to the limitations of previous studies (the follow-up, methodological flaws, heterogeneity among studies, etc.). Notably, robust evidence regarding diagnosis and treatment of certain LC sequelae remain insufficient and has been a stumbling block to better management of these patients. This awkward situation motivated us to conduct this review. Here, we comprehensively reviewed the updated information, particularly focusing on clinical issues. We attempt to provide the latest information regarding LC-related sequelae by systematically reviewing the involvement of main organ systems. We also propose paths for future exploration based on available knowledge and the authors' clinical experience. We believe that these take-home messages will be helpful to gain insights into LC and ultimately benefit clinical practice in treating LC-related sequelae.