Olfactory identification and white matter integrity in amnestic mild cognitive impairment: A preliminary study

Ryu, Seon Young; Lee, Dong Chang; Lee, Sang Bong; Kim, Tae Woo; Lee, Taek Jun; Yang, Po Song; Chung, Sung Woo; Chung, Young-An; Jang, Kyung-Sool

doi:10.1002/ima.22198

Cited by 3 publications

(7 citation statements)

References 43 publications

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“…One study found that total volume of white matter hyperintensities was not associated with UPSIT scores among those with MCI and cognitively normal participants, 19 and another found that gray matter changes were more prominent compared to white matter changes among AD participants 36 . In contrast, three studies found that olfactory identification scores were associated with white matter alterations among those with MCI and AD 21,34,35 …”

Section: Resultsmentioning

confidence: 98%

“…Among case series (n = 4) with no control groups, 21,23,30,35 two studies found that hippocampal atrophy was associated with olfactory dysfunction 21,23 …”

Section: Resultsmentioning

confidence: 99%

“…White matter changes were reported in 6 (25%) of 24 studies 17,19,21,34–36 . One study used an MRI‐based automated classification schema for identifying aMCI using white‐matter alterations assessed with diffusion tensor imaging (DTI).…”

Section: Resultsmentioning

confidence: 99%

“…10 Lastly, one study, which included participants with AD, Parkinson Disease with dementia (PDD), and normal controls, found that the AD group showed lower gray matter volume in the hippocampus compared to the PDD group. 18 Hippocampal Volume-Case Series Among case series (n = 4) with no control groups, 21,23,30,35 two studies found that hippocampal atrophy was associated with olfactory dysfunction. 21,23 Other Brain Structure Volumes Five (21%) of 24 studies reported on the relationship between amygdala volume and cognitive or olfactory performance.…”

Section: Hippocampal Volumementioning

confidence: 99%

“…White matter changes were reported in 6 (25%) of 24 studies. 17,19,21,[34][35][36] One study used an MRI-based automated classification schema for identifying aMCI using white-matter alterations assessed with diffusion tensor imaging (DTI). Using this technique, the study found that changes in the lateral ventricles, splenium of the corpus callosum, and crus of the fornix best discriminated aMCI from normal controls.…”

Section: White Matter Changesmentioning

confidence: 99%

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Magnetic Resonance Imaging Findings Among Individuals With Olfactory and Cognitive Impairment

Hura

Roxbury

et al. 2021

The Laryngoscope

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Objectives: The underlying mechanism of the association between olfactory impairment and dementia may be explained by neurodegenerative changes detected on magnetic resonance imaging (MRI). The purpose of this systematic review is to describe neurodegenerative changes on MRI in patients with olfactory impairment and mild cognitive impairment (MCI) or dementia.Study design: Systematic review. Methods: A literature search encompassing PubMed, Embase, Cochrane Library, Web of Science, Scopus, and Google Scholar for studies with MRI and olfactory testing among participants diagnosed with MCI or dementia was performed. Sample size, study design, cognitive impairment type, olfactory testing, and MRI findings were abstracted. Two investigators independently reviewed all articles.Results: The search yielded 556 nonduplicate abstracts, from which 86 articles were reviewed and 24 were included. Seventeen (71%) of 24 studies reported hippocampal volume findings, with 14 studies reporting a relationship between hippocampal volume and olfactory performance. Two (50%) of four prospective studies reported the potential utility of baseline hippocampal volume as a marker of dementia conversion from MCI. Five (21%) of 24 studies reporting olfactory functional MRI (fMRI) findings highlighted the utility of olfactory fMRI to identify individuals in the early stages of cognitive decline.Conclusion: Current evidence suggests hippocampal volume correlates with olfactory performance in individuals with cognitive impairment, and that olfactory fMRI may improve early detection of AD. However, the predictive utility of these imaging markers is limited in prospective studies. MRI may be a useful modality for selecting patients at high risk of future cognitive decline for enrollment in early treatment trials.

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Section: Resultsmentioning

confidence: 98%

“…Among case series (n = 4) with no control groups, 21,23,30,35 two studies found that hippocampal atrophy was associated with olfactory dysfunction 21,23 …”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Hippocampal Volumementioning

confidence: 99%

Section: White Matter Changesmentioning

confidence: 99%

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Magnetic Resonance Imaging Findings Among Individuals With Olfactory and Cognitive Impairment

Hura

Roxbury

et al. 2021

The Laryngoscope

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Association of Olfaction and Microstructural Integrity of Brain Tissue in Community-Dwelling Adults

et al. 2023

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Objectives: Research on olfaction and brain neuropathology may help understand brain regions associated with normal olfaction and dementia pathophysiology. To identify early regional brain structures affected in poor olfaction, we examined cross-sectional associations of microstructural integrity of the brain with olfaction in the Atherosclerosis Risk in Communities Neurocognitive Study. Methods: Participants were selected from a prospective cohort study of community-dwelling adults; selection criteria included: evidence of cognitive impairment, participation in a previous MRI study, and a random sample of cognitively normal participants. Microstructural integrity was measured by two diffusion tensor imaging (DTI) measures, fractional anisotropy (FA) and mean diffusivity (MD), and olfaction by a 12-item odor-identification test at the same visit. Higher FA and MD values indicate better and worse microstructural integrity, respectively, and higher odor-identification scores indicate better olfaction. We used brain region-specific linear regression models to examine associations between DTI measures and olfaction, adjusting for potential confounders. Results: Among 1,418 participants (mean age: 76±5years, 41% male, 21% Black race, 59% with normal cognition), the mean olfaction score was 9±2.3. Relevant to olfaction, higher MD in the medial temporal lobe (MTL) regions, namely, the hippocampus (β: -0.79 (95%CI: -0.94, -0.65) units lower olfaction score per SD higher MD), amygdala, entorhinal area, and some white matter (WM) tracts connecting to these regions, was associated with olfaction. We also observed associations with MD and WM FA in multiple atlas regions that were not previously implicated in olfaction. The associations between MD and olfaction were particularly stronger in the MTL regions among individuals with mild cognitive impairment (MCI) compared to those with normal cognition (e.g., βhippocampus: -0.75 (95%CI: -1.02, -0.49) and -0.44 (95%CI: -0.63, -0.26) for MCI and normal cognition, respectively, p-interaction=0.004). Conclusions: Neuronal microstructural integrity in multiple brain regions, in particular the MTL (the regions known to be affected in early Alzheimer’s), is associated with odor-identification ability. Differential associations in the MTL regions among cognitively normal individuals compared to those with MCI may reflect the earlier vs. later effects of the dementia pathogenesis. It is likely that some of the associated regions may not have any functional relevance to olfaction.

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Cognitive impairment, neurodegenerative disorders, and olfactory impairment: A literature review

Kovalová,

Gottfriedová,

Mrázková

et al. 2024

Otolaryngol Pol

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Introduction: The early detection and diagnosis of dementia are of key importance in treatment, slowing disease progression, or suppressing symptoms. The possible role of changes in the sense of smell is considered with regard to potential markers for early detection of Alzheimer’s disease (AD). Materials and methods: A literature search was conducted using the electronic databases PubMed, Scopus, and Web of Science between May 30, 2022 and August 2, 2022. The term “dementia” was searched with keyword combinations related to olfaction. Results: A total of 1,288 records were identified through the database search. Of these articles, 49 were ultimately included in the analysis. The results showed the potential role of changes in the sense of smell as potential biomarkers for early detection of AD. Multiple studies have shown that olfactory impairment may be observed in patients with AD, PD, MCI, or other types of dementia. Even though smell tests are able to detect olfactory loss caused by neurodegenerative diseases, they cannot reliably distinguish between certain diseases. Conclusions: In individuals with cognitive impairment or neurodegenerative diseases, olfactory assessment has repeatedly been reported to be used for early diagnosis, but not for differential diagnosis.

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Olfactory identification and white matter integrity in amnestic mild cognitive impairment: A preliminary study

Cited by 3 publications

References 43 publications

Magnetic Resonance Imaging Findings Among Individuals With Olfactory and Cognitive Impairment

Magnetic Resonance Imaging Findings Among Individuals With Olfactory and Cognitive Impairment

Association of Olfaction and Microstructural Integrity of Brain Tissue in Community-Dwelling Adults

Cognitive impairment, neurodegenerative disorders, and olfactory impairment: A literature review

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