COVID-19, the Brain, and the Future: Is Infection by the Novel Coronavirus a Harbinger of Neurodegeneration?

Exploring Cognitive Dysfunction in Long COVID Patients: Eye Movement Abnormalities and Frontal-Subcortical Circuits Implications via Eye-Tracking and Machine Learning

BACKGROUND

Cognitive dysfunction is regarded as one of the most severe aftereffects following coronavirus disease 2019 (COVID-19). Eye movements, controlled by various brain regions, including the dorsolateral prefrontal cortex and frontal-thalamic circuits, offer a potential metric for evaluating cognitive dysfunction. We aimed to examine the utility of eye movement measurements in identifying cognitive impairments in long COVID patients.

METHODS

We recruited 40 long COVID patients experiencing subjective cognitive complaints and 40 healthy controls and used a certified eye-tracking medical device to record saccades and antisaccades. Machine learning was applied to enhance the analysis of eye movement data.

RESULTS

Patients did not differ from the healthy controls regarding age, sex, and years of education. However, the patients' Montreal Cognitive Assessment total score was significantly lower than healthy controls. Most eye movement parameters were significantly worse in patients: the latencies, gain, and velocity of visually and memory-guided saccades, the number of correct memory saccades, the latencies and duration of reflexive saccades, and the number of errors in the antisaccade test. Machine learning permitted distinguishing between long COVID patients experiencing subjective cognitive complaints and healthy controls.

CONCLUSION

Our findings suggest impairments in frontal subcortical circuits in long COVID patients experiencing subjective cognitive complaints. Eye-tracking, combined with machine learning, offers a novel, efficient way to assess and monitor long COVID patients' cognitive dysfunctions, suggesting its utility in clinical settings for early detection and personalized treatment strategies. Further research is needed to determine the long-term implications of these findings and the reversibility of cognitive dysfunctions.

Three Patients With Chorea and Positive Voltage-Gated Potassium Channel Antibody: Is This the Link Between Hyperkinetic von Economo Disease and COVID-19?

Chorea, hemichorea, and other movement disorders have been reported after different pandemics since Constantin von Economo's time. In the current COVID-19 pandemic, numerous delayed neurological manifestations have been reported in the postinfectious or postvaccination periods. However, very few of these are movement disorders in nature; there are even fewer voltage-gated potassium channel (VGKC) antibody-related movement disorder cases in the literature. We encountered three patients with some COVID-19-related issues featuring both chorea and VGKC antibody. Modern medical science and technology may be able to further our understanding of the molecular basis of von Economo disease and reveal a possible link to COVID-19 along with the immunomodulation aspect of its treatment.

Parkinsonism associated with viral infection

There are several known causes of secondary parkinsonism, the most common being head trauma, stroke, medications, or infections. A growing body of evidence suggests that viral agents may trigger parkinsonian symptoms, but the exact pathological mechanisms are still unknown. In some cases, lesions or inflammatory processes in the basal ganglia or substantia nigra have been found to cause reversible or permanent impairment of the dopaminergic pathway, leading to the occurrence of extrapyramidal symptoms. This chapter reviews current data regarding the viral agents commonly associated with parkinsonism, such as Epstein Barr virus (EBV), hepatitis viruses, human immunodeficiency virus (HIV), herpes viruses, influenza virus, coxsackie virus, and Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2). We present possible risk factors, proposed pathophysiology mechanisms, published case reports, common associations, and prognosis in order to offer a concise overview of the viral spectrum involved in parkinsonism.

Perspective: cell death mechanisms and early diagnosis as precondition for disease modification in Parkinson's disease: are we on the right track?

INTRODUCTION

Current research paradigms on biomarkers for chronic neurodegenerative diseases, such as Parkinson's disease, focus on identification of reliable, easy-to-apply tools for diagnostic screening and progression assessment.

AREAS COVERED

This perspective discusses possible misconceptions of biomarker research in chronic neurodegeneration from a clinician's view based on a not systematic literature search. Multifactorial disease triggers, heterogeneity of symptom and their progression are main reasons for the still missing availability of biomarkers.

EXPERT OPINION

Onset of chronic neurodegenerative disease entities may probably result from a decompensated endogenous repair machinery in the central nervous system, for example the neogenin receptor associated repulsive guidance molecule pathway. Future clinical research is warranted on these repair structures and aim to identify markers for the imbalance between damage and repair, which hypothetically contributes to generation of disease. An assignment to a specific chronic neurodegenerative disease entity probably appears to be secondary. Decryption of probable molecular signals of an impaired repair potential will enable an earlier diagnosis, better monitoring of disease progress and of treatment response. This concept will hopefully provide better preconditions for prevention, cure or therapeutic beneficial disease modification. These unmet therapeutic needs may be achieved for example via antagonism of repulsive guidance molecule A.

Eye Movement Alterations in Post-COVID-19 Condition: A Proof-of-Concept Study

There is much evidence pointing out eye movement alterations in several neurological diseases. To the best of our knowledge, this is the first video-oculography study describing potential alterations of eye movements in the post-COVID-19 condition. Visually guided saccades, memory-guided saccades, and antisaccades in horizontal axis were measured. In all visual tests, the stimulus was deployed with a gap condition. The duration of the test was between 5 and 7 min per participant. A group of n=9 patients with the post-COVID-19 condition was included in this study. Values were compared with a group (n=9) of healthy volunteers whom the SARS-CoV-2 virus had not infected. Features such as centripetal and centrifugal latencies, success rates in memory saccades, antisaccades, and blinks were computed. We found that patients with the post-COVID-19 condition had eye movement alterations mainly in centripetal latency in visually guided saccades, the success rate in memory-guided saccade test, latency in antisaccades, and its standard deviation, which suggests the involvement of frontoparietal networks. Further work is required to understand these eye movements' alterations and their functional consequences.