Left hippocampal volume loss in Alzheimer's disease is reflected in performance on odor identification: A structural MRI study

Abstract

The very high sensitivity and specificity of odor identification tasks in discriminating between Alzheimer's patients and normals suggests that they reflect the presence of underlying neuropathology. Significant neuropathological changes are seen in areas critical to processing olfactory information, even in the early stages of Alzheimer's disease (AD). The current study was designed to investigate whether performance on olfactory tasks (odor threshold and odor identification) was related to volumetric MRI measures of mesial temporal areas central to olfactory information processing and important in the neuropathology of AD. Participants were 8 male and 5 female patients with probable AD, and 10 male and 12 female normal age-matched controls, diagnosed at the UCSD Alzheimer's Disease Research Center. The study investigated correlations between volumetric measures of hippocampus, the parahippocampal gyrus and the amygdala, and the psychophysical measures of olfactory function. Robust relationships were observed between mesial temporal lobe volumes and olfactory functional measures. The finding of a strong relationship between left hippocampal volume and performance on the odor identification task (r 5 .85) is compatible with a left-hemisphere superiority for verbally mediated olfactory tasks. The findings suggest a neural substrate for the breakdown in functional performance on verbally mediated odor identification tasks in Alzheimer's disease and suggest the utility of quantitative MRI measures and psychophysical performance in the assessment of AD. These results support the potential clinical utility of inclusion of odor identification tests in diagnostic batteries for detecting AD. (JINS, 2003, 9, 459-471.)

Odor Identification and Regional Gray Matter Atrophy in Patients with Alzheimer’s Disease, Parkinson’s Disease, and the Healthy Elderly: A Cross-Sectional Structural MRI Study

“…Second, findings in AD patients were mostly in line with previous reports about which regions are involved in olfactory information processing [12][13][14][15]20]. We showed significantly decreased odor identification performance and associated atrophy of the bilateral orbitofrontal cortices, which are consistently described as either primary or secondary olfactory areas.…”

Odor Identification and Regional Gray Matter Atrophy in Patients with Alzheimer’s Disease, Parkinson’s Disease, and the Healthy Elderly: A Cross-Sectional Structural MRI Study

“…Second, findings in AD patients were mostly in line with previous reports about which regions are involved in olfactory information processing [12][13][14][15]20]. We showed significantly decreased odor identification performance and associated atrophy of the bilateral orbitofrontal cortices, which are consistently described as either primary or secondary olfactory areas.…”

The relationship between cerebral Alzheimer's disease pathology and odour identification in old age

“…[34][35][36] Our results show this association in people without dementia, consistent with studies showing reduced activation of central olfactory areas, including entorhinal cortex and hippocampus, during olfactory processing in older compared with younger people. 37 38 Together, these data support the value of olfactory assessment for early detection of Alzheimer's disease.…”

The Neuroanatomic Correlates of Olfactory Identification Impairment in Healthy Older Adults and in Persons with Mild Cognitive Impairment

“…Our findings correspond with prior work demonstrating olfactory abnormalities in MCI and AD, including loss of myelinated axons in the olfactory tracts, olfactory bulb and olfactory cortex atrophy, and reduced functional activation in primary olfactory regions during olfactory stimulation [13, 37–40]. Olfactory impairment in MCI and AD has also been linked with reduced amygdala, ERC, and hippocampal volumes [9, 41–44]. Prestia and colleagues [45] examined longitudinal patterns of neurodegeneration using VBM and ROI analyses in CN and MCI.…”

Odor Identification and Regional Gray Matter Atrophy in Patients with Alzheimer’s Disease, Parkinson’s Disease, and the Healthy Elderly: A Cross-Sectional Structural MRI Study

“…Second, findings in AD patients were mostly in line with previous reports about which regions are involved in olfactory information processing [12][13][14][15]20]. We showed significantly decreased odor identification performance and associated atrophy of the bilateral orbitofrontal cortices, which are consistently described as either primary or secondary olfactory areas.…”

The relationship between cerebral Alzheimer's disease pathology and odour identification in old age

“…[34][35][36] Our results show this association in people without dementia, consistent with studies showing reduced activation of central olfactory areas, including entorhinal cortex and hippocampus, during olfactory processing in older compared with younger people. 37 38 Together, these data support the value of olfactory assessment for early detection of Alzheimer's disease.…”

The Neuroanatomic Correlates of Olfactory Identification Impairment in Healthy Older Adults and in Persons with Mild Cognitive Impairment

“…Our findings correspond with prior work demonstrating olfactory abnormalities in MCI and AD, including loss of myelinated axons in the olfactory tracts, olfactory bulb and olfactory cortex atrophy, and reduced functional activation in primary olfactory regions during olfactory stimulation [13, 37–40]. Olfactory impairment in MCI and AD has also been linked with reduced amygdala, ERC, and hippocampal volumes [9, 41–44]. Prestia and colleagues [45] examined longitudinal patterns of neurodegeneration using VBM and ROI analyses in CN and MCI.…”

Odor Identification and Regional Gray Matter Atrophy in Patients with Alzheimer’s Disease, Parkinson’s Disease, and the Healthy Elderly: A Cross-Sectional Structural MRI Study

“…Second, findings in AD patients were mostly in line with previous reports about which regions are involved in olfactory information processing [12][13][14][15]20]. We showed significantly decreased odor identification performance and associated atrophy of the bilateral orbitofrontal cortices, which are consistently described as either primary or secondary olfactory areas.…”

The relationship between cerebral Alzheimer's disease pathology and odour identification in old age

“…[34][35][36] Our results show this association in people without dementia, consistent with studies showing reduced activation of central olfactory areas, including entorhinal cortex and hippocampus, during olfactory processing in older compared with younger people. 37 38 Together, these data support the value of olfactory assessment for early detection of Alzheimer's disease.…”

The Neuroanatomic Correlates of Olfactory Identification Impairment in Healthy Older Adults and in Persons with Mild Cognitive Impairment

“…Our findings correspond with prior work demonstrating olfactory abnormalities in MCI and AD, including loss of myelinated axons in the olfactory tracts, olfactory bulb and olfactory cortex atrophy, and reduced functional activation in primary olfactory regions during olfactory stimulation [13, 37–40]. Olfactory impairment in MCI and AD has also been linked with reduced amygdala, ERC, and hippocampal volumes [9, 41–44]. Prestia and colleagues [45] examined longitudinal patterns of neurodegeneration using VBM and ROI analyses in CN and MCI.…”