Global cognitive impairment should be taken into account in SPECT-neuropsychology correlations: the example of verbal memory in very mild Alzheimer's disease

Characteristic deterioration of ADAS-Jcog subscale scores and correlations with regional cerebral blood flow reductions in Alzheimer's disease

The Alzheimer Disease Assessment Scale (Japanese version) cognitive subscale (ADAS-Jcog) is composed of a number of subscale tasks. However, it is not clear which subscale tasks are most susceptible to impairment in Alzheimer's disease (AD) or what is the relationship between reduction in regional cerebral blood flow (rCBF) and decreased ADAS-Jcog scores. Subjects were 32 AD patients, aged 52-86 years. We examined the relationship between subscale tasks that showed marked score changes and brain regions that showed reduced rCBF over a 2-year period. rCBF was measured by single-photon emission computed tomography (SPECT) with technetium-99m ethyl cysteinate dimer (^99mTc-ECD), and the SPECT imaging data were analyzed with the easy Z-score imaging system (eZIS) and voxel-based stereotactic extraction estimation (vbSEE) methods. Total score of ADAS-Jcog deteriorated from 19.5 ± 7.0 to 35.7 ± 15.2 after 2 years. Subscale scores were significantly worse in all fields, particularly in orientation, word recall, remembering test instructions, commands, constructional praxis, and ideational praxis, in that order. Significant correlations were found between (1) word recall and commands and rCBF in the left middle temporal lobe, (2) naming objects/fingers and rCBF in the left temporal (middle, inferior) lobe, and (3) constructional and ideational praxis and rCBF in the right parietal (superior, inferior) lobe, temporal (superior, middle) lobe, angular gyrus, and cingulate gyrus. We identified the brain regions associated with specifically impaired subscales of ADAS-Jcog during progressive deterioration of AD over 2 years.

Verbal or Visual Memory Score and Regional Cerebral Blood Flow in Alzheimer Disease

Objective

Among many cognitive function deficits, memory impairment is an initial and cardinal symptom in Alzheimer disease (AD). In most cases, verbal and visual memory scores correlate highly, but in some cases the deficit of verbal or visual memory is very different from that of the other memory. In this study, we examined the neural substrates of verbal and visual memory in patients with AD.

Methods

One hundred eighty-eight consecutive patients with AD were recruited from outpatient units. Verbal and visual memory scores were evaluated using the Wechsler Memory Scale – revised. The patients underwent brain SPECT with ^99mTc-ethylcysteinate dimer.

Results

After removing the effects of age, sex, education, and Mini-Mental State Examination scores, correlation analysis showed a significant correlation of verbal memory scores to regional cerebral blood flow (rCBF) in the bilateral cingulate gyrus and left precuneus. Similarly, a significant correlation of visual memory scores to rCBF was found in the right precuneus and right cingulate gyrus.

Conclusion

The posterior medial cortices (PMC) are very important areas in episodic memory among patients with mild AD. Verbal memory is more closely related to the both sides of the PMC, while visual memory is more closely related to the right PMC.

Relationships between cognitive impairment on ADAS-cog and regional cerebral blood flow using SPECT in late-onset Alzheimer's disease

The aim of this study was to examine brain hypoperfusion and its relationship with cognitive dysfunction in late-onset Alzheimer's disease (AD). Forty patients with late-onset AD and not receiving acetylcholinesterase inhibitors were recruited from outpatient clinics. We examined cognitive function using the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) and brain perfusion using single-photon emission computed tomography, and analyzed classified gyrus level segments with three-dimensional stereotactic surface projection and the stereotactic extraction estimation method level 3. ADAS-cog subscales were grouped into three domains: language, memory, and praxis. Patients with late-onset AD showed an apparent reduction in regional cerebral blood flow (rCBF) with a z score >1.5 in the frontal, temporal, and limbic lobes, with lesser reduction in the parietal and occipital lobes. Although hypoperfusion in the orbital, rectal, and subcallosal gyri of the frontal lobe was prominent, rCBF in the inferior frontal gyrus of the frontal lobe was significantly correlated with ADAS-cog total and language and praxis subscale scores. The parahippocampal gyrus of the limbic lobe was also significantly correlated with the ADAS-cog total, language, and praxis subscale scores. Additionally, the cingulate of the limbic lobe was significantly related with ADAS-cog memory. In spite of lesser hypoperfusion, the posterior cingulate gyrus of the limbic lobe was significantly related with ADAS-cog total, language, and memory subscale scores. Further, each subdivision of ADAS-cog was found to be related with various brain regions.

Topography of Cortical Microbleeds in Alzheimer's Disease with and without Cerebral Amyloid Angiopathy: A Post-Mortem 7.0-Tesla MRI Study

Cortical microbleeds (CMBs) detected on T2*-weighted gradient-echo (GRE) magnetic resonance imaging (MRI) are considered as a possible hallmark of cerebral amyloid angiopathy (CAA). The present post-mortem 7.0-tesla MRI study investigates whether topographic differences exist in Alzheimer's brains without (AD) and with CAA (AD-CAA). The distribution of CMBs in thirty-two post-mortem brains, consisting of 12 AD, 8 AD-CAA and 12 controls, was mutually compared on T2*-GRE MRI of six coronal sections of a cerebral hemisphere. The mean numbers of CMBs were determined in twenty-two different gyri. As a whole there was a trend of more CMBs on GRE MRI in the prefrontal section of the AD, the AD-CAA as well as of the control brains. Compared to controls AD brains had significantly more CMBs in the superior frontal, the inferior temporal, the rectus and the cinguli gyrus, and in the insular cortex. In AD-CAA brains CMBs were increased in all gyri with exception of the medial parietal gyrus and the hippocampus. AD-CAA brains showed a highly significant increase of CMBs in the inferior parietal gyrus (p value: 0.001) and a significant increase in the precuneus and the cuneus (p value: 0.01) compared to the AD brains. The differences in topographic distribution of CMBs between AD and AD-CAA brains should be further investigated on MRI in clinically suspected patients.

Plasma antioxidants and brain glucose metabolism in elderly subjects with cognitive complaints

PURPOSE

The role of oxidative stress is increasingly recognized in cognitive disorders of the elderly, notably Alzheimer's disease (AD). In these subjects brain(18)F-FDG PET is regarded as a reliable biomarker of neurodegeneration. We hypothesized that oxidative stress could play a role in impairing brain glucose utilization in elderly subjects with increasing severity of cognitive disturbance.

METHODS

The study group comprised 85 subjects with cognitive disturbance of increasing degrees of severity including 23 subjects with subjective cognitive impairment (SCI), 28 patients with mild cognitive impairment and 34 patients with mild AD. In all subjects brain FDG PET was performed and plasma activities of extracellular superoxide dismutase (eSOD), catalase and glutathione peroxidase were measured. Voxel-based analysis (SPM8) was used to compare FDG PET between groups and to evaluate correlations between plasma antioxidants and glucose metabolism in the whole group of subjects, correcting for age and Mini-Mental State Examination score.

RESULTS

Brain glucose metabolism progressively decreased in the bilateral posterior temporoparietal and cingulate cortices across the three groups, from SCI to mild AD. eSOD activity was positively correlated with glucose metabolism in a large area of the left temporal lobe including the superior, middle and inferior temporal gyri and the fusiform gyrus.

CONCLUSION

These results suggest a role of oxidative stress in the impairment of glucose utilization in the left temporal lobe structures in elderly patients with cognitive abnormalities, including AD and conditions predisposing to AD. Further studies exploring the oxidative stress-energy metabolism axis are considered worthwhile in larger groups of these patients in order to identify pivotal pathophysiological mechanisms and innovative therapeutic opportunities.

Increased striatal dopamine (D2/D3) receptor availability and delusions in Alzheimer disease

OBJECTIVE

Dysfunction within corticostriatal dopaminergic neurocircuitry has been implicated in neuropsychiatric symptoms associated with Alzheimer disease (AD). This study aimed to test the hypothesis that the symptom domains delusions and apathy would be associated with striatal dopamine (D2) receptor function in AD.

METHODS

In vivo dopamine (D2/D3) receptor availability was determined with [(11)C]raclopride (RAC) PET in 23 patients with mild and moderate probable AD. Behavioral symptoms were measured using the Neuropsychiatric Inventory and the Apathy Inventory. Imaging data were analyzed using a region-of-interest approach. The potential confounding effects of age, sex, and disease stage were explored using a linear mixed model. Correlational and independent samples comparisons were used to examine the relationship between behavioral and binding potential (BP(ND)) measures.

RESULTS

Mean [(11)C]RAC BP(ND) was higher in patients with delusions (n = 7; 5 men) than in patients without delusions (n = 16; 6 men) (p = 0.006). When women were excluded from the analysis, [(11)C]RAC BP(ND) was higher in men with delusions than in men without delusions (p = 0.05). Apathy measures showed no association with [(11)C]RAC BP(ND).

CONCLUSIONS

Striatal dopamine (D2/D3) receptor availability is increased in Alzheimer disease patients with delusions, to an extent comparable to that observed in drug-naive patients with schizophrenia. Whether this represents up-regulation of dopamine (D2) or possibly dopamine (D3) receptors and how this relates to responsivity of the striatal dopaminergic system merit further exploration.

Cerebral perfusion (HMPAO-SPECT) in patients with depression with cognitive impairment versus those with mild cognitive impairment and dementia of Alzheimer's type: a semiquantitative and automated evaluation

PURPOSE

Comparative evaluation of regional brain perfusion measured by HMPAO-SPECT of patients with mild cognitive impairment (MCI), dementia of Alzheimer's type (DAT) and depression with cognitive impairment (DCI).

METHODS

A total of 736 patients were investigated because of suspected cognitive dysfunction. After exclusion of patients with other forms of dementia than DAT or relevant accompanying disorders, SPECT data from 149 MCI, 131 DAT and 127 DCI patients, and 123 controls without any cognitive impairment, were analysed. Relative cerebral blood flow of 34 anatomical regions was assessed with automated analysis software (BRASS).

RESULTS

Calculation of global forebrain perfusion discriminated demented from nondemented patients. Compared to controls DCI patients showed hypoperfusion of the thalamus, lentiform nucleus and medial temporal cortex. MCI patients differed significantly from controls concerning perfusion in both hemispheric temporal and parietal areas, and in the (right hemispheric) posterior part of the cingulate gyrus. MCI and DCI patients differed in the parietal, temporal superior and right hemispheric cingulate gyrus posterior cortices. Global forebrain and regional perfusion was more extensively reduced in DAT patients and discriminated them from controls, and MCI and DCI patients. Frontal perfusion disturbance was only present in DAT patients.

CONCLUSION

Automated analysis of HMPAO-SPECT data from MCI patients showed significant perfusion deficits in regions also involved in DAT patients, but ROC analysis demonstrated only moderate sensitivity and specificity for differentiating DAT patients from controls and DCI patients. Frontal hypoperfusion seems to correspond with conversion from MCI to DAT. Finally, the results in DCI patients again raise the question of depression as an early symptom of neurodegeneration.

Regional cerebral blood flow correlates of visuospatial tasks in Alzheimer's disease

This study investigated the role of visuospatial tasks in identifying cognitive decline in patients with Alzheimer's disease (AD), by correlating neuropsychological performance with cerebral perfusion measures. There were 157 participants: 29 neurologically healthy controls (age: 70.3 +/- 6.6, MMSE > or = 27), 86 patients with mild AD (age: 69.18 +/- 8.28, MMSE > or = 21) and 42 patients moderate/severe AD (age: 68.86 +/- 10.69, MMSE 8-20). Single Photon Emission Computerized Tomography (SPECT) was used to derive regional perfusion ratios, and correlated using partial least squares (PLS) with neuropsychological test scores from the Benton Line Orientation (BLO) and the Rey-Osterrieth Complex Figure (RO). Cross-sectional analysis demonstrated that mean scores differed in accordance with disease status: control group (BLO 25.5, RO 33.3); mild AD (BLO 20.1, RO 25.5); moderate/severe AD (BLO 10.7, RO 16). Correlations were observed between BLO/RO and right parietal SPECT regions in the AD groups. Visuospatial performance, often undersampled in cognitive batteries for AD, is clearly impaired even in mild AD and correlates with functional deficits as indexed by cerebral perfusion ratios on SPECT implicating right hemisphere circuits. Furthermore, PLS reveals that usual spatial tasks probe a distributed brain network in both hemispheres including many areas targeted by early AD pathology.