Seon Young Ryu

Measurement of Precuneal and Hippocampal Volumes Using Magnetic Resonance Volumetry in Alzheimer's Disease

Background and Purpose Alzheimers disease (AD) is associated with structural alterations in the medial temporal lobe (MTL) and functional alterations in the posterior cortical region, especially in the early stages. However, it is unclear what mechanisms underlie these regional discrepancies or whether the posterior cortical hypometabolism reflects disconnection from the MTL lesion or is the result of local pathology. The precuneus, an area of the posteromedial cortex that is involved in the early stages of AD, has recently received a great deal of attention in functional neuroimaging studies. To assess the relationship between the precuneus and hippocampus in AD, we investigated the volumes of these two areas using a magnetic resonance volumetric method. Methods Twenty-three subjects with AD and 14 healthy age-matched controls underwent T1-weighted three-dimensional volumetric brain magnetic resonance imaging. Volumetric measurements were performed in the precuneus and hippocampus. Results Compared to controls, AD patients exhibited a significant reduction in total precuneal volume, which was more prominent on the right side, and significant bilateral reductions in hippocampal volume. No correlation was found between the total volumes of the precuneus and hippocampus in the AD group. Conclusions These results suggest that volumetric measurements of both the precuneus and hippocampus are useful radiological indices for the diagnosis of AD. Furthermore, the lack of correlation is attributable to local pathology rather than being a secondary consequence of MTL pathology.

Subjective memory complaints, depressive symptoms and instrumental activities of daily living in mild cognitive impairment.

BACKGROUND The diagnostic relevance of subjective memory complaints (SMCs) in mild cognitive impairment (MCI) remains to be unresolved. The aim of this study is to determine clinical correlates of SMCs in MCI. Furthermore, we examined whether there are the differences due to different aspects of complaints (i.e. prospective memory (PM) versus retrospective memory (RM) complaints). METHODS We examined the cross-sectional associations between SMCs and depressive symptoms, instrumental activities of daily living (IADL), and cognitive measures in sixty-six individuals with MCI (mean age: 65.7 ± 8.01 years). The criteria for MCI included SMCs, objective cognitive impairment, normal general cognitive function, largely intact functional activities, and absence of dementia. SMCs were assessed using the Prospective and Retrospective Memory Questionnaire (PRMQ), which contains 16 items describing everyday memory failure of both PM and RM. RESULTS SMC severity (i.e. PRMQ total score) was associated with stronger depressive symptoms and worse IADL performance. SMCs were not related to cognitive measures. For PM and RM subscores, both depressive symptoms and IADL were related to the PRMQ-PM and -RM scores. The main contributors to these PM and RM scores were depressive symptoms and IADL impairment, respectively. CONCLUSIONS This study suggests that SMCs are more associated with depressive symptoms and IADL problems than with cognitive performance in individuals with MCI. Furthermore, while PM and RM complaints are related to both depressive symptoms and IADL, the differences between these main contributors suggest that RM complaints based on IADL could be more associated with the organically driven pathological features of MCI.

Hippocampal and entorhinal structures in subjective memory impairment: a combined MRI volumetric and DTI study

BACKGROUND Subjective memory impairment (SMI) is common among older adults. Increasing evidence suggests that SMI is a risk factor for future cognitive decline, as well as for mild cognitive impairment and dementia. Medial temporal lobe structures, including the hippocampus and entorhinal cortex, are affected in the early stages of Alzheimers disease. The current study examined the gray matter (GM) volume and microstructural changes of hippocampal and entorhinal regions in individuals with SMI, compared with elderly control participants without memory complaints. METHODS A total of 45 participants (mean age: 70.31 ± 6.07 years) took part in the study, including 18 participants with SMI and 27 elderly controls without memory complaints. We compared the GM volume and diffusion tensor imaging (DTI) measures in the hippocampal and entorhinal regions between SMI and control groups. RESULTS Individuals with SMI had lower entorhinal cortical volumes than control participants, but no differences in hippocampal volume were found between groups. In addition, SMI patients exhibited DTI changes (lower fractional anisotropy (FA) and higher mean diffusivity in SMI) in the hippocampal body and entorhinal white matter compared with controls. Combining entorhinal cortical volume and FA in the hippocampal body improved the accuracy of classification between SMI and control groups. CONCLUSIONS These findings suggest that the entorhinal region exhibits macrostructural as well as microstructural changes in individuals with SMI, whereas the hippocampus exhibits only microstructural alterations.

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

Increasing evidence suggests that olfactory impairment is associated with an increased risk of conversion from mild cognitive impairment (MCI) to Alzheimers disease. This study was to explore how olfactory identification relates to white matter (WM) integrity, using diffusion tensor imaging (DTI) in individuals with amnestic MCI. DTI was performed from nineteen individuals with amnestic MCI (mean age: 69.95 ± 8.20 years). Olfactory identification was assessed using the Cross‐Cultural Smell Identification Test (CC‐SIT), a widely used test for odor identification involving a scratch and sniff test of 12 micro‐encapsulated odorants. Cross‐sectional voxel‐wise analyses of relationships between CC‐SIT scores and DTI indices were performed using Tract‐Based Spatial Statistics. Higher CC‐SIT scores were associated with lower mean, axial and radial diffusivities in areas such as the body and splenium of corpus callosum, frontal WM (lateral orbitofrontal, caudal middle frontal, precentral, left superior frontal, and right pars opercularis), right superior longitudinal fasciculus, anterior and superior corona radiata, and internal and external capsules, while CC‐SIT scores were not significantly associated with fractional anisotropy across all MCI participants. In individuals with amnestic MCI, impaired olfactory identification is associated with alterations in WM integrity expressed as a lower diffusivities value. This cross‐sectional preliminary study suggests that olfactory impairment contributes to WM microstructural alterations in individuals with amnestic MCI.

WHITE MATTER INTEGRITY AND OLFACTORY FUNCTION IN MILD COGNITIVE IMPAIRMENT: PRELIMINARY STUDY

Background: Increasing evidence suggests that olfactory impairment is associated with an increased risk of conversion from mild cognitive impairment (MCI) to Alzheimer’s disease. To explore how olfactory performance relate to white matter (WM) integrity, diffusion tensor imaging (DTI) was acquired from individuals with mild cognitive impairment (MCI). Methods: DTI was performed from thirteen individuals with MCI (mean age: 68.31 6 8.83 years). Olfactory performance was assessed using the Brief Smell Identification Test (B-SIT). Cross-sectional voxel-wise analyses of relationships between B-SIT and DTI indices were performed using tract-based spatial statistics. Results: Higher B-SIT scores were associated with lower mean diffusivity (MD) in areas such as the body and splenium of corpus callosum, right posterior thalamic radiation, superior corona radiata, internal and external capsules, sagittal stratum, frontal WM, right precuneus WM, and right temporalWM, while B-SIT scores were not significantly associated with fractional anisotropy across all MCI participants. Conclusions:In individuals with MCI, lower olfactory identification is associated with alterations in WM integrity expressed as a lower MD value. These cross-sectional preliminary studies suggest that olfactory impairment contributes to WM microstructural alterations in individuals with MCI. To clarify our results, further investigations in larger samples are required.

WHITE MATTER INTEGRITY AND PROSPECTIVE MEMORY PERFORMANCE IN MILD COGNITIVE IMPAIRMENT: PRELIMINARY STUDY

Background: Prospective memory (PM) is the ability to remember to execute delayed intentions. Prior studies have demonstrated that PM is impaired in patients with mild cognitive impairment (MCI). However, whether prospective memory impairment would affect the neural health is unclear. Methods: In the current study, white matter (WM) integrity and self-reported PM measures were examined in 33 MCI patients (67.33 6 8.33 years). WM integrity was analysed by voxel-wise Tract-Based Spatial Statistics using diffusion tensor imaging. The PM scale from the Prospective and Retrospective Memory Questionnaire (PRMQ) was used to assess PM performance.Results:Worse PRMQ performancewas associated with fractional anisotropy (FA) reduction in several regions like left caudal middle frontal WM, left precentral and postcentral WM, left internal capsule, left corona radiata, left external capsule, and left superior longitudinal fasciculus, but was associated with FA increase in areas such as right fusiform WM, right lateral occipital WM, middle cerebellar peduncle, brainstem, and right cerebellar WM (uncorrected p < .05, controlling for age and education). In addition, more PM fails were associated with higher FA in several regions like right fusiform WM, right lateral occipital WM, right pericalcarine WM, and left cuneus WM (uncorrected p < .05, controlling for age and education). Conclusions: These cross-sectional findings showing the relationship between more PM fails and higher FA in several WM regions might suggest a compensatory mechanism in the MCI patients. However, these results should be confirmed in larger samples.