Characterizing the white matter hyperintensity penumbra with cerebral blood flow measures.

OBJECTIVE: White matter hyperintensities (WMHs) are common with age, grow over time, and are associated with cognitive and motor impairments. Mechanisms underlying WMH growth are unclear. We aimed to determine the presence and extent of decreased normal appearing white matter (NAWM) cerebral blood flow (CBF) surrounding WMHs to identify 'WM at risk', or the WMH CBF penumbra. We aimed to further validate cross-sectional finding by determining whether the baseline WMH penumbra CBF predicts the development of new WMHs at follow-up. METHODS: Sixty-one cognitively intact elderly subjects received 3 T MPRAGE, FLAIR, and pulsed arterial spin labeling (PASL). Twenty-four subjects returned for follow-up MRI. The inter-scan interval was 18 months. A NAWM layer mask, comprised of fifteen layers, 1 mm thick each surrounding WMHs, was generated for periventricular (PVWMH) and deep (DWMH) WMHs. Mean CBF for each layer was computed. New WMH and persistent NAWM voxels for each penumbra layer were defined from follow-up MRI. RESULTS: CBF in the area surrounding WMHs was significantly lower than the total brain NAWM, extending approximately 12 mm from both the established PVWMH and DWMH. Voxels with new WMH at follow-up had significantly lower baseline CBF than voxels that maintained NAWM, suggesting that baseline CBF can predict the development of new WMHs over time. CONCLUSIONS: A CBF penumbra exists surrounding WMHs, which is associated with future WMH expansion. ASL MRI can be used to monitor interventions to increase white matter blood flow for the prevention of further WM damage and its cognitive and motor consequences.

Nutrient biomarker patterns, cognitive function, and MRI measures of brain aging.

OBJECTIVE: To examine the cross-sectional relationship between nutrient status and psychometric and imaging indices of brain health in dementia-free elders. METHODS: Thirty plasma biomarkers of diet were assayed in the Oregon Brain Aging Study cohort (n = 104). Principal component analysis constructed nutrient biomarker patterns (NBPs) and regression models assessed the relationship of these with cognitive and MRI outcomes. RESULTS: Mean age was 87 ± 10 years and 62% of subjects were female. Two NBPs associated with more favorable cognitive and MRI measures: one high in plasma vitamins B (B1, B2, B6, folate, and B12), C, D, and E, and another high in plasma marine ω-3 fatty acids. A third pattern characterized by high trans fat was associated with less favorable cognitive function and less total cerebral brain volume. Depression attenuated the relationship between the marine ω-3 pattern and white matter hyperintensity volume. CONCLUSION: Distinct nutrient biomarker patterns detected in plasma are interpretable and account for a significant degree of variance in both cognitive function and brain volume. Objective and multivariate approaches to the study of nutrition in brain health warrant further study. These findings should be confirmed in a separate population.

Impact of white matter hyperintensity volume progression on rate of cognitive and motor decline.

BACKGROUND: White matter hyperintensity (WMH) change on brain MRI is observed with increased frequency in the elderly and has been independently associated with neurologic decline. The degree to which the location and rate of volume increase in WMH affects other structural brain changes along with cognitive and motor performance over time may determine subsequent degrees of risk for dementia and other syndromes of aging. METHODS: One hundred four cognitively intact men and women followed longitudinally for up to 13 years underwent at least three MRIs with corresponding annual cognitive and neurologic assessments. Brain volume, ventricular CSF (vCSF), and total periventricular (PV) and subcortical WMH volumes were measured. Progression of MRI volumes was examined in relation to rates of cognitive, motor, and cerebral volume change based on slopes of outcomes. RESULTS: Higher initial total and PV WMH volume was associated with total WMH, PV WMH, and vCSF progression, and with increased time and number of steps to walk 30 feet. Progression of PV WMH volume was associated with increased time to walk 30 feet. Progression of subcortical WMH volume was associated with decreased performance on logical memory testing and increased rate of vCSF volume change. CONCLUSION: Increased total and periventricular (PV) white matter hyperintensity (WMH) burden and progression of PV WMH burden are associated with decreased gait performance over time, while progression of subcortical WMH volume is associated with memory decline in cognitively intact elderly. Greater progression of WMH burden is associated with an increased risk of memory and gait dysfunction, and thus should not be considered a benign process.

Trajectories of brain loss in aging and the development of cognitive impairment.

BACKGROUND: The use of volumetric MRI as a biomarker for assessing transitions to dementia presumes that more rapid brain loss marks the clinical transition from benign aging to mild cognitive impairment (MCI). The trajectory of this volume loss relative to the timing of the clinical transition to dementia has not been established. METHODS: The authors annually evaluated 79 healthy elderly subjects for up to 15 consecutive years with standardized clinical examinations and volumetric brain MRI assessments of ventricular volume. During the study period, 37 subjects developed MCI. A mixed effects model with a change point modeled the pattern of brain volume loss in healthy aging compared with subjects diagnosed with MCI. RESULTS: The brain loss trajectory of subjects developing MCI during follow-up differed from healthy aging in a two-phase process. First, the annual rate of expansion of ventricular volume decreased with age; however, the annual rates of expansion were greater in those who developed cognitive impairment during follow-up compared with those who did not. Further, subjects who developed MCI had an acceleration of ventricular volume expansion approximately 2.3 years prior to clinical diagnosis of MCI. CONCLUSIONS: Ventricular expansion is faster in those developing mild cognitive impairment years prior to clinical symptoms, and eventually a more rapid expansion occurs approximately 24 months prior to the emergence of clinical symptoms. These differential rates of preclinical atrophy suggest that there are specific windows for optimal timing of introduction of dementia prevention therapies in the future.

Brain volumes in Guam dementia vs Parkinson dementia complex vs aging Chamorro adults.

We sought to determine if Chamorro individuals with a family history of Guam dementia (GD) or Parkinson dementia complex (PDC) exhibit presymptomatic brain MRI changes. Sixty-six Chamorro subjects had neurocognitive assessment and volumetric MRI. MRI brain volumes differed between diagnostic groups (GD, PDC, control) and according to family history. Chamorros with a family history of PDC or dementia may have increased brain atrophy, suggesting a hereditary susceptibility to neurodegenerative disorders.

Cortical excitability and age-related volumetric MRI changes.

OBJECTIVE: Normative data on transcranial magnetic stimulation (TMS)-derived measures of cortical excitability in the elderly is sparse. Nevertheless, elderly subjects are included as controls in studies utilizing TMS to investigate disease states. Age-associated increased ventricular cerebrospinal fluid CSF (vCSF) and white matter hyperintensity (WMH) MRI volumes have uncertain significance in non-demented elderly. Information regarding cortical excitability in neurologically intact elderly would augment our understanding of the pathophysiology of aging and assist in the interpretation of TMS studies involving elderly subjects. METHODS: Twenty-four healthy elderly subjects underwent TMS testing to determine outcomes of resting motor threshold (RMT) cortical silent period (cSP) and central motor conduction time for examination in relation to WMH, vCSF, and CNS volumes. RESULTS: Increased vCSF and WMH volumes were associated with decreased right and left hemisphere RMT. Smaller CNS volumes were associated with decreased right hemisphere RMT and shorted cSP. CONCLUSIONS: Commonly observed age-associated MRI changes are associated with findings consistent with increased cortical excitability. SIGNIFICANCE: Age-related MRI findings likely reflect changes at a cellular level, and may influence cognitive and motor integrity in the elderly. Future TMS studies investigating cortical excitability may wish to consider neuroimaging markers of neurodegeneration prior to enrolling elderly subjects as controls.

Changes in premorbid brain volume predict Alzheimer's disease pathology.

OBJECTIVE: To assess whether changes in antemortem MRI brain volume measurements are valid predictors of subsequent Alzheimer disease (AD) pathology. METHODS: Thirty-nine subjects, 15 nondemented and 24 with cognitive impairment, were followed until death. Regional postmortem measures of senile plaque (SP) and neurofibrillary tangle (NFT) severity were examined in relationship to cross-sectional and longitudinal volumetric measurements obtained from antemortem MRI. RESULTS: Total brain volume change over time was related to the accumulation of cortical NFT. The rate of ventricular CSF volume increase was related to both cortical NFT and SP. The last hippocampal volume prior to death was related to hippocampal NFT burden; the rate of hippocampal volume atrophy was not related to hippocampal NFT pathology. These significant relationships continue to exist when all nondemented subjects are excluded from analysis. In subjects with cognitive impairment, the best predictor of cortical NFT and SP is the rate of ventricular volume increase. Excluding subjects with long duration between MRI and death did not appreciably alter results. CONCLUSIONS: MRI volumes measured over time are valid biomarkers of pathologic progression of AD across a range of antemortem clinical states. The rate of ventricular volume enlargement can be used to monitor disease progression or response to treatment in future clinical trials that are targeted at NFT and SP pathology.

Natural history of cognitive decline in the old old.

OBJECTIVE: To prospectively examine the occurrence and outcome of cognitive decline in healthy, community-dwelling elders. METHODS: Ninety-five elders (mean age 84 years) who at entry had no cognitive impairment were followed for up to 13 years. Cognitive decline was defined as obtaining either a Clinical Dementia Rating (CDR) = 0.5 or Mini-Mental State Examination (MMSE) score < 24 on two examinations. RESULTS: Three outcomes of aging were determined: intact cognition, persistent cognitive decline without progression to dementia, and dementia. Whereas 49% remained cognitively intact, 51% developed cognitive decline. Mean follow-up to first CDR 0.5 was 3.8 years and age at conversion was 90.0 years. Those who remained cognitively intact had better memory at entry and were less likely to have APOE4 than those who developed cognitive decline. Of the 48 participants with cognitive decline, 27 (56%) developed dementia (CDR > or =1) a mean of 2.8 years later. Participants with cognitive decline who progressed to dementia had poorer confrontation naming at the time of their first CDR 0.5 than those with persistent cognitive decline who did not progress during follow-up. CONCLUSION: The old old are at high risk for developing cognitive decline but many will not progress to dementia in the next 2 to 3 years or even beyond. These findings are important for understanding the prognosis of cognitive decline and for the design of treatment trials for AD. APOE genotype is a risk factor for cognitive decline.