The Value of Neuroimaging in Dementia Diagnosis

Alcohol Use Disorder and Dementia: A Review

PURPOSE

By 2040, 21.6% of Americans will be over age 65, and the population of those older than age 85 is estimated to reach 14.4 million. Although not causative, older age is a risk factor for dementia: every 5 years beyond age 65, the risk doubles; approximately one-third of those older than age 85 are diagnosed with dementia. As current alcohol consumption among older adults is significantly higher compared to previous generations, a pressing question is whether drinking alcohol increases the risk for Alzheimer's disease or other forms of dementia.

SEARCH METHODS

Databases explored included PubMed, Web of Science, and ScienceDirect. To accomplish this narrative review on the effects of alcohol consumption on dementia risk, the literature covered included clinical diagnoses, epidemiology, neuropsychology, postmortem pathology, neuroimaging and other biomarkers, and translational studies. Searches conducted between January 12 and August 1, 2023, included the following terms and combinations: "aging," "alcoholism," "alcohol use disorder (AUD)," "brain," "CNS," "dementia," "Wernicke," "Korsakoff," "Alzheimer," "vascular," "frontotemporal," "Lewy body," "clinical," "diagnosis," "epidemiology," "pathology," "autopsy," "postmortem," "histology," "cognitive," "motor," "neuropsychological," "magnetic resonance," "imaging," "PET," "ligand," "degeneration," "atrophy," "translational," "rodent," "rat," "mouse," "model," "amyloid," "neurofibrillary tangles," "α-synuclein," or "presenilin." When relevant, "species" (i.e., "humans" or "other animals") was selected as an additional filter. Review articles were avoided when possible.

SEARCH RESULTS

The two terms "alcoholism" and "aging" retrieved about 1,350 papers; adding phrases-for example, "postmortem" or "magnetic resonance"-limited the number to fewer than 100 papers. Using the traditional term, "alcoholism" with "dementia" resulted in 876 citations, but using the currently accepted term "alcohol use disorder (AUD)" with "dementia" produced only 87 papers. Similarly, whereas the terms "Alzheimer's" and "alcoholism" yielded 318 results, "Alzheimer's" and "alcohol use disorder (AUD)" returned only 40 citations. As pertinent postmortem pathology papers were published in the 1950s and recent animal models of Alzheimer's disease were created in the early 2000s, articles referenced span the years 1957 to 2024. In total, more than 5,000 articles were considered; about 400 are herein referenced.

DISCUSSION AND CONCLUSIONS

Chronic alcohol misuse accelerates brain aging and contributes to cognitive impairments, including those in the mnemonic domain. The consensus among studies from multiple disciplines, however, is that alcohol misuse can increase the risk for dementia, but not necessarily Alzheimer's disease. Key issues to consider include the reversibility of brain damage following abstinence from chronic alcohol misuse compared to the degenerative and progressive course of Alzheimer's disease, and the characteristic presence of protein inclusions in the brains of people with Alzheimer's disease, which are absent in the brains of those with AUD.

Genetic risk scores enhance the diagnostic value of plasma biomarkers of brain amyloidosis

Blood-based biomarkers offer strong potential to revolutionize diagnosis, trial enrolment and treatment monitoring in Alzheimer's disease (AD). However, further advances are needed before these biomarkers can achieve wider deployment beyond selective research studies and specialty memory clinics, including the development of frameworks for optimal interpretation of biomarker profiles. We hypothesized that integrating Alzheimer's disease genetic risk score (AD-GRS) data would enhance the diagnostic value of plasma AD biomarkers by better capturing extant disease heterogeneity. Analysing 962 individuals from a population-based sample, we observed that an AD-GRS was independently associated with amyloid PET levels (an early marker of AD pathophysiology) over and above APOE ε4 or plasma p-tau181, amyloid-β42/40, glial fibrillary acidic protein or neurofilament light chain. Among individuals with a high or moderately high plasma p-tau181, integrating AD-GRS data significantly improved classification accuracy of amyloid PET positivity, including the finding that the combination of a high AD-GRS and high plasma p-tau181 outperformed p-tau181 alone in classifying amyloid PET positivity (88% versus 68%; P = 0.001). A machine learning approach incorporating plasma biomarkers, demographics and the AD-GRS was highly accurate in predicting amyloid PET levels (90% training set; 89% test set) and Shapley value analyses (an explainer method based in cooperative game theory) indicated that the AD-GRS and plasma biomarkers had differential importance in explaining amyloid deposition across individuals. Polygenic risk for AD dementia appears to account for a unique portion of disease heterogeneity, which could non-invasively enhance the interpretation of blood-based AD biomarker profiles in the population.

Clinicoradiologic and Neuropathologic Evaluation of Corticobasal Syndrome

BACKGROUND AND OBJECTIVES

Corticobasal syndrome (CBS) is a clinical phenotype characterized by asymmetric parkinsonism, rigidity, myoclonus, and apraxia. Originally believed secondary to corticobasal degeneration (CBD), mounting clinicopathologic studies have revealed heterogenous neuropathologies. The objectives of this study were to determine the pathologic heterogeneity of CBS, the clinicoradiologic findings associated with different underlying pathologies causing CBS, and the positive predictive value (PPV) of current diagnostic criteria for CBD among patients with a CBS.

METHODS

Clinical data, brain MRI, and neuropathologic data of patients followed at Mayo Clinic and diagnosed with CBS antemortem were reviewed according to neuropathology category at autopsy.

RESULTS

The cohort consisted of 113 patients with CBS, 61 (54%) female patients. Mean ± SD disease duration was 7 ± 3.7 years; mean ± SD age at death was 70.5 ± 9.1 years. The primary neuropathologic diagnoses were 43 (38%) CBD, 27 (24%) progressive supranuclear palsy (PSP), 17 (15%) Alzheimer disease (AD), 10 (9%) frontotemporal lobar degeneration (FTLD) with TAR DNA-binding protein 43 (TDP) inclusions, 7 (6%) diffuse Lewy body disease (DLBD)/AD, and 9 (8%) with other diagnoses. Patients with CBS-AD or CBS-DLBD/AD were youngest at death (median [interquartile range]: 64 [13], 64 [11] years) while CBS-PSP were oldest (77 [12.5] years, p = 0.024). Patients with CBS-DLBD/AD had the longest disease duration (9 [6] years), while CBS-other had the shortest (3 [4.25] years, p = 0.04). Posterior cortical signs and myoclonus were more characteristic of patients with CBS-AD and patients with CBS-DLBD/AD. Patients with CBS-DLBD/AD displayed more features of Lewy body dementia. Voxel-based morphometry revealed widespread cortical gray matter loss characteristic of CBS-AD, while CBS-CBD and CBS-PSP predominantly involved premotor regions with greater amount of white matter loss. Patients with CBS-DLBD/AD showed atrophy in a focal parieto-occipital region, and patients with CBS-FTLD-TDP had predominant prefrontal cortical loss. Patients with CBS-PSP had the lowest midbrain/pons ratio (p = 0.012). Of 67 cases meeting clinical criteria for possible CBD at presentation, 27 were pathology-proven CBD, yielding a PPV of 40%.

DISCUSSION

A variety of neurodegenerative disorders can be identified in patients with CBS, but clinical and regional imaging differences aid in predicting underlying neuropathology. PPV analysis of the current CBD diagnostic criteria revealed suboptimal performance. Biomarkers adequately sensitive and specific for CBD are needed.

Improvement of brain perfusion in patients with chronic brain ischemia at epidural spinal cord electrical stimulation

Objective

Increasing life expectancy and aging of the population is accompanied by a steady increase in the number of elderly patients with chronic cerebral ischemia and age-related cognitive impairment associated with cerebral hypoperfusion and microangiopathy. The aim of this study was to identify long-term changes in cerebral blood flow (CBF) in patients with chronic cerebral ischemia at the epidural electrical stimulation of the spinal cord (SCS).

Materials and methods

Changes in cerebral blood flow were studied according to CT perfusion in 59 patients (aged 55–78 years) with vertebrogenic pain syndromes and chronic cerebral ischemia during epidural electrical stimulation of the spinal cord at the cervical (C3–C5) and lower thoracic (Th9–Th10) levels.

Results

In all patients, on the 5th day of trial SCS, an increase in cerebral blood flow by from 58.6 ± 1.13 ml/100 ml/min to 64.8 ± 1.21 ml/100 ml/min (p < 0.01) with stimulation at the Th9-Th10 level and from 58.8 ± 1.12 ml/100 ml/min to 68.2 ± 1.42 ml/100 ml/min (p < 0, 01) with stimulation at the C3-C5 level. These changes in brain perfusion were preserved during the follow-up examination 1 year after the implantation of chronic SCS system. The greatest increase in CBF was registered in the frontotemporal regions, subcortical structures and white matter of the brain. Changes in cerebral perfusion did not correlate with the degree of reduction in the severity of the accompanying pain syndrome. The change in CBF in the control group (32 patients) in all periods was not statistically significant.

Conclusion

Our results show that SCS is accompanied by a persistent improvement in brain perfusion, which may be potentially useful for developing methods for reducing age-related vascular disorders in the elderly.