Publications by authors named "Oezguer A Onur"

Background And Objectives: Apraxia is a frequently observed symptom in Alzheimer disease (AD), but the causal pathomechanism underlying this dysfunction is not well understood. Previous studies have demonstrated associations between various cognitive dysfunctions in AD and cortical tau deposition in specific brain areas, suggesting a causal relationship. Thus, we hypothesized that specific regional patterns of tau pathology in praxis-related brain regions may be associated with apraxic deficits in AD.

View Article and Find Full Text PDF

Background: Misfolding and aggregation of amyloid β (Aβ), along with neurofibrillary tangles consisting of aggregated Tau species, are pathological hallmarks of Alzheimer's disease (AD) onset and progression. In this study, we hypothesized the clearance of Aβ aggregates from the brain and body into the gut.

Methods: To investigate this, we used surface-based fluorescence intensity distribution analysis (sFIDA) to determine the Aβ aggregate concentrations in feces from 26 AD patients and 31 healthy controls (HC).

View Article and Find Full Text PDF
Article Synopsis
  • - Germany's healthcare system faces significant challenges in identifying Alzheimer's disease patients eligible for new amyloid-targeting therapies, with projected wait times up to 50 months for specialist visits and PET scans from 2024 to 2043.
  • - Patients with social health insurance are expected to endure longer wait times compared to those with private insurance, with peak delays reaching 76 months for social insurance patients and 40 months for private insurance patients.
  • - Implementing a blood test as part of the diagnostic process could significantly reduce wait times to under 24 months, highlighting the urgent need for effective triage measures to improve patient access to potentially life-changing treatments.
View Article and Find Full Text PDF

Some people infected with SARS-CoV-2 report persisting symptoms following acute infection. If these persist for over three months, they are classified as post-COVID-19 syndrome (PCS). Although PCS is frequently reported, detailed longitudinal neuropsychological characterization remains scarce.

View Article and Find Full Text PDF

Background And Objectives: In light of limited intensive care capacities and a lack of accurate prognostic tools to advise caregivers and family members responsibly, this study aims to determine whether automated cerebral CT (CCT) analysis allows prognostication after out-of-hospital cardiac arrest.

Methods: In this monocentric, retrospective cohort study, a supervised machine learning classifier based on an elastic net regularized logistic regression model for gray matter alterations on nonenhanced CCT obtained after cardiac arrest was trained using 10-fold cross-validation and tested on a hold-out sample (random split 75%/25%) for outcome prediction. Following the literature, a favorable outcome was defined as a cerebral performance category of 1-2 and a poor outcome of 3-5.

View Article and Find Full Text PDF

Objectives: Apraxia is a core feature of Alzheimer's disease, but the pathomechanism of this characteristic symptom is not well understood. Here, we systematically investigated apraxia profiles in a well-defined group of patients with Alzheimer's disease (AD; N=32) who additionally underwent PET imaging with the second-generation tau PET tracer [18F]PI-2620. We hypothesized that specific patterns of tau pathology might be related to apraxic deficits.

View Article and Find Full Text PDF

Rationale & Objective: Hyponatremia is the most common electrolyte disorder and is associated with significant morbidity and mortality. This study investigated neurocognitive impairment, brain volume, and alterations in magnetic resonance imaging (MRI)-based measures of cerebral function in patients before and after treatment for hyponatremia.

Study Design: Prospective cohort study.

View Article and Find Full Text PDF

Introduction: In clinical practice, differentiating between age-related gray matter (GM) atrophy and neurodegeneration-related atrophy at early disease stages, such as mild cognitive impairment (MCI), remains challenging. We hypothesized that fined-grained adjustment for age effects and using amyloid-negative reference subjects could increase classification accuracy.

Methods: T1-weighted magnetic resonance imaging (MRI) data of 131 cognitively normal (CN) individuals and 91 patients with MCI from the Alzheimer's disease neuroimaging initiative (ADNI) characterized concerning amyloid status, as well as 19 CN individuals and 19 MCI patients from an independent validation sample were segmented, spatially normalized and analyzed in the framework of voxel-based morphometry (VBM).

View Article and Find Full Text PDF

Background: Due to the increasing prevalence of Alzheimer's disease (AD) and the limited efficacy of pharmacological treatment, the interest in non-pharmacological interventions, e.g., cognitive stimulation therapy (CST), to improve cognitive dysfunction and the quality of life of AD patients are on a steady rise.

View Article and Find Full Text PDF

Literature proposes five distinct cognitive strategies for wayfinding decisions at intersections. Our study investigates whether those strategies rely on a generalized decision-making process, on two frame-specific processes-one in an egocentric and the other in an allocentric spatial reference frame, and/or on five strategy-specific processes. Participants took six trips along a prescribed route through five virtual mazes, each designed for decision-making by a particular strategy.

View Article and Find Full Text PDF

Objective: Elevated cortisol levels have been frequently reported in Alzheimer's disease (AD) and linked to brain atrophy, especially of the hippocampus. Besides, high cortisol levels have been shown to impair memory performance and increase the risk of developing AD in healthy individuals. We investigated the associations between serum cortisol levels, hippocampal volume, gray matter volume and memory performance in healthy aging and AD.

View Article and Find Full Text PDF

Background: A fraction of patients with asymptomatic to mild/moderate acute COVID-19 disease report cognitive deficits as part of the post-COVID-19 syndrome. This study aimed to assess the neuropsychological profile of these patients.

Methods: Assessment at baseline (three months or more following acute COVID-19) of a monocentric prospective cohort of patients with post-COVID-19 syndrome.

View Article and Find Full Text PDF

Dementias are expensive diseases: the net annual cost in European healthcare is about € 28.000 per case with a strong stage dependency, of which medical care accounts for about 19%. Diagnostic costs, on the other hand, account for only a small proportion of the total costs.

View Article and Find Full Text PDF

Aging is associated with memory decline and progressive disabilities in the activities of daily living. These deficits have a significant impact on the quality of life of the aging population and lead to a tremendous burden on societies and health care systems. Understanding the mechanisms underlying aging-related memory decline is likely to inform the development of compensatory strategies promoting independence in old age.

View Article and Find Full Text PDF

Acute aortic dissection is rare but life-threatening. The symptoms depend on the localization and reduced perfusion of the downstream organs or limbs and are therefore variable. Neurological symptoms may occur that do not immediately lead to a diagnosis and thus delay the necessary therapy.

View Article and Find Full Text PDF

Introduction: Several recent research studies show high performance of blood biomarkers to identify Alzheimer's disease also in the pre-dementia mild cognitive impairment (MCI) stage, but data from the routine clinical care memory clinic setting are needed.

Methods: We examined plasma samples of 144 memory clinic patients, including dementia of Alzheimer type (DAT, n = 54), MCI (n = 57), and subjective cognitive decline (SCD, n = 33), who either presented as self-referrals or were referred by general practitioners or neurologists or psychiatrists. The plasma biomarkers, amyloid-beta42 (Aß42), amyloid-beta40 (Aß40), phospho-Tau181 (pTau181), total-tau (tTau), and neurofilament light (NFL), as well as different ratios, were measured using the ultrasensitive single molecule array (Simoa) immunoassay technology.

View Article and Find Full Text PDF

Due to the increasing number of cases of Alzheimer's disease and the relatively moderate success with the available symptomatic and causal pharmacological therapies, there is a considerable need to explore non-pharmacological treatment options. In the field of non-invasive brain stimulation (NIBS), various methods have been investigated, particularly transcranial magnetic stimulation and transcranial electrical stimulation. In addition, deep brain stimulation (DBS) is currently being researched as an innovative method for targeted neuromodulation.

View Article and Find Full Text PDF

Background And Objectives: In 2020, a wide range of hygiene measures was implemented to mitigate infections caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In consequence, pulmonary infections due to other respiratory pathogens also decreased. Here, we evaluated the number of bacterial and viral meningitis and encephalitis cases during the coronavirus disease 2019 (COVID-19) pandemic.

View Article and Find Full Text PDF

We aimed to evaluate the current management of status epilepticus (SE) in intensive care units (ICUs) in Germany, depending on the different hospital levels of care and the ICU specialty. We performed a nationwide web-based anonymized survey, including all German ICUs registered with the German Society for Neurointensive and Emergency Care (Deutsche Gesellschaft für Neurointensiv- und Notfallmedizin; DGNI). The response rate was 83/232 (36%).

View Article and Find Full Text PDF

Deep brain stimulation (DBS) is a neurosurgical treatment with a growing range of indications. The number of clinical studies is expanding because of DBS for new indications and efforts to improve DBS for existing indications. To date, various methods have been used to perform DBS studies.

View Article and Find Full Text PDF

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) profoundly impacts hemostasis and microvasculature. In the light of the dilemma between thromboembolic and hemorrhagic complications, in the present paper, we systematically investigate the prevalence, mortality, radiological subtypes, and clinical characteristics of intracranial hemorrhage (ICH) in coronavirus disease (COVID-19) patients.

Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we performed a systematic review of the literature by screening the PubMed database and included patients diagnosed with COVID-19 and concomitant ICH.

View Article and Find Full Text PDF

Background: Early and severe neuronal loss in the cholinergic basal forebrain is observed in Alzheimer's disease (AD). To date, cholinomimetics play a central role in the symptomatic treatment of AD dementia. Although basic research indicates that a cholinergic deficit is present in AD before dementia, the efficacy of cholinomimetics in mild cognitive impairment (MCI) remains controversial.

View Article and Find Full Text PDF
Article Synopsis
  • - The study aimed to investigate if SARS-CoV-2 causes a lasting infection in the central nervous system after COVID-19 by analyzing cerebrospinal fluid (CSF) samples. - Researchers collected CSF from patients at various intervals post-COVID-19 (1-30 days, 31-90 days, and over 90 days) and found no SARS-CoV-2 RNA present in any of the samples. - The absence of both the virus and specific antibodies in CSF suggests that a persistent central nervous system infection is unlikely to contribute to neurological or neuropsychiatric issues in post-COVID-19 patients.
View Article and Find Full Text PDF

Background: Social cognition (SC) is a core criterion for neurocognitive disorders. However, findings in patients with amnestic mild cognitive impairment (aMCI) and dementia of the Alzheimer type (DAT) are inconsistent.

Objective: We report assessments of emotion recognition (ER), affective and cognitive theory of mind (ToM) in young (YC) and older controls (OC) compared to aMCI and DAT.

View Article and Find Full Text PDF