Senile dementia and healthy aging: a longitudinal CT study

Evaluation of total cerebral blood flow volume in cerebral atrophy

The goal of our study is to determine total cerebral blood flow volume (tCBFV) via extracranial Doppler ultrasound and to investigate its value in the differential diagnosis of dementia. Twenty-eight outpatients with cerebral atrophy confirmed by cranial computed tomography were enrolled into the study. Nine patients with Alzheimer's disease (AD) and nine patients with vascular dementia (VaD) based on neuropsychologic test and imaging findings, as well as 10 neurologically normal elderly subjects underwent Doppler sonographic examination of extracranial internal carotid artery (ICA) and vertebral artery (VA). Angle corrected time averaged flow velocity and cross-sectional areas of vessels have been measured. Flow volumes and tCBFV have been calculated. The measures of tCBFV, anterior CBFV (aCBFV), right CBFV (rCBFV) and right ICA flow volume were significantly lower in patients with dementia. The amounts of tCBFV, aCBFV, rCBFV and right ICA flow volume have been found to be low in AD and VaD patients compared with normal elderly group. Of all parameters measured for AD and VaD, no significant difference was found except Mini-Mental State Examination (MMSE) scores. To the best of our knowledge, this is the first reporting the CBF measurements using Doppler ultrasound of extracranial ICA and VA in the differential diagnosis of dementia in cerebral atrophy. The tCBFV, aCBFV, rCBFV and right ICA flow volumes and MMSE scores are significant in the diagnosis of dementia, whereas only MMSE scores are significant in the differential diagnosis of AD and VaD.

Rates of hippocampal atrophy correlate with change in clinical status in aging and AD

BACKGROUND

The cognitive continuum in the elderly population can be conceptually divided into those who are functioning normally (control subjects), those with a mild cognitive impairment (MCI), and those with probable AD.

OBJECTIVES

To test the hypothesis that the annualized rates of hippocampal atrophy differ as a function of both baseline and change in clinical group membership (control, MCI, or AD).

METHODS

The authors identified 129 subjects from the Mayo Clinic AD Research Center/AD Patient Registry who met established criteria for normal control subjects, MCI, or probable AD, both at entry and at the time of a subsequent clinical follow-up evaluation 3 +/- 1 years later. Each subject underwent an MRI examination of the head at the time of the initial assessment and at follow-up clinical assessment; the annualized percentage change in hippocampal volume was computed. Subjects who were classified as controls or patients with MCI at baseline could either remain cognitively stable or could decline to a lower functioning group over the period of observation.

RESULTS

The annualized rates of hippocampal volume loss for each of the three initial clinical groups decreased progressively in the following order: AD > MC > control. Within the control and MCI groups, those who declined had a significantly greater rate of volume loss than those who remained clinically stable. The mean annualized rates of hippocampal atrophy by follow-up clinical group were: control-stable 1.73%, control-decliner 2.81%, MCI-stable 2.55%, MCI-decliner 3.69%, AD 3. 5%.

CONCLUSION

Rates of hippocampal atrophy match both baseline cognitive status and the change in cognitive status over time in elderly persons who lie along the cognitive continuum from normal to MCI to AD.

Does an increase in sulcal or ventricular fluid predict where brain tissue is lost?

Quantitative volumes of cerebrospinal fluid (CSF) and brain tissue were measured on magnetic resonance images (MRIs) of 287 individuals from 5 diagnostic groups: Alzheimer's disease (AD), chronic alcoholics (ALC), individuals positive for human immunodeficiency virus (HIV), schizophrenia subjects (SZ), and normal comparison subjects (NC) older than 50 years of age. Within each group, mean volumes were calculated for ventricular CSF, cortical (sulcal) CSF, cortical gray matter, total white matter, basal ganglia gray matter, and thalamic gray matter. Correlations of CSF measures with brain tissue measures were determined, and multiple regression analyses were performed to try and predict volume of gray matter or white matter region from volume of CSF compartment. Results indicated the following: 1. Enlarged cortical fluid volume significantly predicts cortical gray matter deficits for subjects with AD and those who are ALC and SZ but not for subjects with HIV or NC. 2. Enlarged cortical fluid volume also significantly predicts white matter deficits in all five groups. 3. Enlarged ventricular fluid volume significantly predicts basal ganglia deficits in AD, HIV, and NC but not in SZ or ALC. 4. Enlarged ventricular volume has no predictive value for thalamic volume for any of the groups. This study supports the clinical practice of predicting brain tissue volume loss from CSF enlargement but not for all brain regions in all diagnoses.

Rate of medial temporal lobe atrophy in typical aging and Alzheimer's disease

OBJECTIVES

To determine the annual rates of volumetric change of the hippocampus and temporal horn in cognitively normal elderly control subjects and individually matched patients with AD, and to test the hypothesis that these rates were different.

BACKGROUND

Cross-sectional studies consistently reveal cerebral atrophy in elderly nondemented subjects compared with healthy young adults, and greater atrophy in patients with AD relative to elderly control subjects. However, rates of atrophy are estimated most accurately by performing serial measurements in the same individuals.

METHODS

MRI-based volumetric measurements of the hippocampi and temporal horns were performed in 24 cognitively normal subjects aged 70 to 89 years who were individually matched with respect to gender and age with 24 patients with AD. Each subject underwent an MRI protocol twice, separated by 12 months or more.

RESULTS

The mean annual rate of hippocampal volume loss among control subjects was -1.55+/-1.38% and the temporal horns increased in volume by 6.15+/-7.69% per year. These rates were significantly greater among AD patients: hippocampus, -3.98+/-1.92% per year, p < 0.001; temporal horn, 14.16+/-8.47% per year, p = 0.002.

CONCLUSION

A statistically significant yearly decline in hippocampal volume and an increase in temporal horn volume was identified in elderly control subjects who represent typical aging individuals. These rates were approximately 2.5 times greater in patients with AD than in individually age- and gender-matched control subjects.

Neuroimaging of the aging brain

Age-related white matter injury has been recognized increasingly with the improvement of brain imaging technology. Arteriosclerosis and venous collagenosis, which occur with aging, result in a spectrum of white matter changes that range from periventricular to subcortical and deep white matter hyperintensities best seen on T2 weighted magnetic resonance imaging. These white matter changes are associated not only with aging, but with hypertension and silent infarctions. Loss of brain volume and accumulation of iron in putamen occur with normal, healthy aging. This article discusses the imaging appearance of healthy aging and pathological correlates of similar appearing alterations. The imaging findings of the most common neurodegenerative disorders, Alzheimer's and Parkinson's disease, are highlighted.

Interpretation variability of 18FDG-positron emission tomography studies in dementia

RATIONALE AND OBJECTIVES

Functional imaging studies such as 18F-fluoro-18-labeled-deoxyglucose-positron emission tomography (18FDG-PET) are being used increasingly in the evaluation of patients with dementia. The authors evaluate inter- and intraobserver interpretation agreement in a diverse group of patients with clinically diagnosed dementia and subjective memory complaints, as well as two healthy control subjects.

METHODS

Ninety-six patients with clinical diagnoses of probable Alzheimer's disease (n = 18), possible Alzheimer's disease (n = 33), dementia (n = 26), and mild memory impairment (n = 17), as well as two healthy control subjects were studied using 18FDG-PET. Three observers graded all studies for regional 18FDG uptake in the temporal, parietal, and frontal regions bilaterally. The studies also were interpreted for the presence of bilateral temporoparietal hypometabolism, which typically is present in Alzheimer's disease. The kappa statistic was used to determine intra- and interobserver agreement for regional 18FDG uptake and bilateral temporoparietal hypometabolism.

RESULTS

There was excellent intraobserver (kappa = .56, P < 0.0005) and interobserver (kappa = .51, P < 0.0005) interpretation agreement for bilateral temporoparietal hypometabolism. There also was excellent intraobserver (kappa = .61, P < 0.000) and interobserver (kappa = .55, P < 0.000) interpretation agreement of regional 18FDG uptake. Interobserver agreement was extremely high in those patients who were considered clinically to have possible (kappa = .42, P < 0.001) or probable (kappa = .42, P < 0.01) Alzheimer's disease.

CONCLUSIONS

Results confirm that bilateral temporoparietal hypometabolism is the metabolic abnormality associated with the diagnosis of probable Alzheimer's disease. Furthermore, intra- and interobserver agreement of visual interpretation of 18FDG-PET images indicates that 18FDG-PET is acceptable as an imaging technique in the clinical evaluation of the dementia patient.

Longitudinal cognitive, electroencephalographic and morphological brain changes in ageing and Alzheimer's disease

BACKGROUND

The natural course of cognitive performance, electrophysiological alterations and brain atrophy in ageing and Alzheimer's disease (AD) has been investigated in numerous studies, but only few attempts have been made to examine the relationship between clinical, electroencephalographic (EEG) and morphological changes with quantitative methods prospectively over longer periods of time.

METHOD

Fifty-five patients with clinically diagnosed AD and 66 healthy elderly controls were examined biannually using a cognitive test (CAMCOG), EEG band power and volumetric estimates of brain atrophy.

RESULTS

On average cognitive performance deteriorated by 28 points on the CAMCOG in the AD group, the alpha/theta ratio decreased by 0.2, and the proportion of intracranial cerebrospinal fluid volume increased by 3.5% during a 2-year period. Similar changes were observed after a second 2-year interval. A multiple regression model demonstrated a significant influence of age on cognition and atrophy and a significant influence of the estimated duration of symptoms on cognition, alpha/theta ratio and brain atrophy at the initial examination. Cognitive performance at the first examination exerted significant effects on the performance and also on brain atrophy at re-examination after 2 or 4 years, whereas the EEG and neuroimaging findings at the previous examination were exclusively related to the corresponding findings at the follow-up examinations. In the control group no significant cognitive, EEG and morphological changes were observed after 2 and 4 years.

CONCLUSION

After 2 consecutive follow-up periods, we were able to verify significant deteriorations of cognition accompanied by neurophysiological and neuroradiological changes in AD, but not in normal ageing. In clinically diagnosed AD, cognitive performance at the followup examination could not be predicted by the previous alpha/theta ratio or by the previous degree of global brain atrophy, whereas the cognitive test score determined not only performance, but also structural findings at follow-up. Performance on cognitive tests appears to be a more sensitive indicator of the degenerative process than EEG band-power and morphological changes in manifest AD. Neuroimaging, neurophysiology and genetic risk markers may be more important for the early differential diagnosis than for the prediction of the course of illness.

Diagnostic testing and dementia

The prevalence of dementia is expected to increase markedly as our population ages. Although only a minority of cases currently are found to have treatable causes, the personal and financial costs of misdiagnosis are great. Furthermore, progress in developing effective therapy hinges on accurate diagnosis. This article reviews the current state of diagnostic testing in the diagnosis of dementia.

Prospective CT confirms differences between vascular and Alzheimer's dementia

BACKGROUND AND PURPOSE

Cognitive test performances were correlated prospectively with changes in cerebral CT measurements of atrophy, infarct volume, ventricular enlargement, local tissue density, and local perfusion to contrast annual rates of changes among patients with ischemic vascular dementia (IVD) or dementia of the Alzheimer type (DAT).

METHODS

The cerebral atrophic index (ATI; ratio of cerebrospinal fluid or infarcted brain to intracranial volume), infarct volume ratio, ventricular volume ratio (VVR; ventricular volume/intracranial volume), cortical and subcortical gray and white matter local perfusion (local cerebral blood flow [LCBF]), and local Hounsfield unit (HU) density were measured concurrently and compared longitudinally with Cognitive Capacity Screening Examinations (CCSE) scores among 24 treated IVD (age, 68.2 +/- 9.7 years; follow-up, 42 +/- 27 months) and 24 DAT patients (age, 74.2 +/- 6.2 years; follow-up, 30 +/- 19 months).

RESULTS

IVD annual changes were as follows: CCSE, +1.2 +/- 5.9; ATI, +2.1%/y; VVR, +3.2%/y; and LCBF in the subcortical basal ganglia, -0.74 mL.100 g-1.min-1.y-1 (-1.8%/y). DAT annual changes were as follows: CCSE, -1.8/y; ATI, +8.1%/y; VVR, +9.6%/y; cortical LCBF, -2.0 mL.100 g-1.min-1.y-1 (-5.2%/y); LCBF in the basal ganglia, -3.0 mL.100 g-1.min-1.y-1 (-6.7%/y); white matter LCBF, -0.75 mL.100 g-1.min-1.y-1 (-4.1%/y); and all cortical tissue densities, -0.83 HU/y (-2.1%/y). In IVD, multiple regression analyses correlated cognitive changes directly with (1) recurrent silent infarctions and (2) bidirectional changes of perfusions within frontal white matter, thalamus, and internal capsules. In DAT, cognitive declines correlated with cerebral atrophy and cortical hypoperfusion related to frontotemporal and parietal cortical polioaraiosis (decreased gray matter tissue densities).

CONCLUSIONS

In IVD, recurrent strokes were not observed clinically during risk factor control, and antiplatelet therapy and cognitive impairments improved or stabilized. In DAT, cognitive performance relentlessly declined. Ischemic pathogenesis for vascular dementia is supported by the following: (1) cognitive declines correlate directly with recurrent "silent" strokes, and (2) bidirectional cognitive changes correlate directly with frontal white matter, thalamic, and internal capsular perfusional changes.

Cognitive declines correlate with decreased cortical volume and perfusion in dementia of Alzheimer type

Cerebral CT changes are correlated with cognitive declines among 18 patients with probable dementia of Alzheimer type (DAT) (7 men, 11 women, mean age 75.4 years) and are compared for control purposes with similar measures among 18 age-matched normal volunteers (8 men, 10 women, mean age 73.7 years). Mean follow-up intervals are 28.6 months for DAT and 27.0 months for controls. For DAT, annual rates for ventricular volume enlargement are +9.2% and for cortical atrophy are -2.1%. Annual reductions in regional cerebral perfusions per 100 g brain/min, are: total cortex -1.1 ml, frontal -1.2 ml, temporal and parietal -0.9 ml, basal ganglia -1.6 ml, thalamus -2.5 ml, total white matter -0.6 ml, frontal white matter -0.7 ml. At entry evaluation, compared to normals, DAT patients had reduced CT densities in white matter, but not in cortex. Nevertheless, cortical CT densities declined progressively at annual rates of -0.72 Hounsfield units (HU), but remained constant in white matter. Annual point score declines for Cognitive Capacity Screening Examinations were -2.0 and for Mini Mental State: -2.8. Controls showed no cognitive change. Multiple regression analyses correlate cognitive declines with: (1) reductions in perfusion within parietal cortex (p = 0.015), (2) decreases in cortical volume (p = 0.019), and (3) decreases in HU within subcortical gray matter (p = 0.007).

Reliability of in vivo volume measures of hippocampus and other brain structures using MRI

Volume reductions of the hippocampus are associated with Alzheimer's disease, schizophrenia, and epilepsy. We used clinically available MRI methods (2D acquisition; inversion recovery and calculated T2 images; 3 mm contiguous slices) that optimize image contrast, quality, and resolution and standardized positioning protocols to maximize the in vivo accuracy (test-retest reliability) of brain volume measurements in volunteers who were scanned two or three times. Volunteers were scanned in the same MRI instrument (intrascanner reliability) as well as in two different instruments (interscanner reliability). A single rater obtained brain volume measures of seven contiguous slices centered on the anterior commissure. The in vivo intrascanner reliability for measures of anterior hippocampus and ventricular volumes was very good, with reliability coefficients [intraclass r (rxx)] ranging between .855 and .997, and a median coefficient of variation (CV) of 6.4%. Reliability was good for amygdala (rxx of .740 and .764) and for total frontal and temporal lobe volumes and white matter volume measures (rxx ranging between .640 and .823, median coefficient of variation was 3.2%). Overall, interscanner reliability was also good. We discuss the implications of our results relative to the possible clinical utility of hippocampal quantification and the feasibility of prospective studies aimed at quantifying progressive neurodegeneration.

A clinicopathological study of CT scans in Alzheimer's disease

OBJECTIVE

To investigate the accuracy of cranial computerized tomography (CT) scans in distinguishing patients with Alzheimer's disease from those with other dementing conditions.

DESIGN

Retrospective clinicopathological correlation with pre-mortem CT scans.

SETTING

Urban and rural hospitals and nursing homes in the Upper Midwest.

PATIENTS

All 507 patients had clinical dementia diagnosed as Alzheimer's disease during life and the subsequent referral of their brains to a dementia brain bank. Of these, 375 patients had had CT scans as part of the diagnostic work-up for dementia.

MAIN OUTCOME MEASURES

The presence of neuropathological evidence of Alzheimer's disease and the specific findings on CT scans.

RESULTS

Of the 375 patients evaluated with a CT, 28% were misdiagnosed (lacked neuropathological evidence of Alzheimer's disease); of the 132 patients evaluated without a CT scan, only 18% were misdiagnosed (P less than 0.05). The degree of atrophy and other CT findings were similar in the correctly diagnosed and misdiagnosed groups except for increased ventricular size in the correctly diagnosed patients (P less than 0.05).

CONCLUSION

Although CT scans do not usually contribute to the recognition of Alzheimer's disease, the presence of ventricular enlargement may help distinguish Alzheimer's disease from other dementias.