White matter lesions impair frontal lobe function regardless of their location

Interacting effects of age and time of day on verbal fluency performance and intraindividual variability

We explored the effects of age and time of day (TOD) on verbal fluency ability with respect to performance level and intraindividual variability (IIV). Verbal fluency, which involves complex cognitive operations, was examined in 20 older (mean age = 72.8 years) and 20 younger (mean age = 24.2 years) adults with test start time alternating between morning and evening across four days. Older adults generated more words in the morning and younger adults more in the evening, corresponding with self-report peak TOD. Age by TOD interactions were also observed across fluency tasks on the number of switches among subcategory exemplars during word generation and on the IIV observed in switching behavior. Older adults exhibited greater variability in switching in the evening than in the morning, whereas younger adults showed the opposite pattern. These findings demonstrate that processes involving energization (initiating and sustaining) and attentional control may be particularly sensitive to age differences in TOD influences on cognition.

White matter hyperintensities among older adults are associated with futile increase in frontal activation and functional connectivity during spatial search

The mechanisms by which aging and other processes can affect the structure and function of brain networks are important to understanding normal age-related cognitive decline. Advancing age is known to be associated with various disease processes, including clinically asymptomatic vascular and inflammation processes that contribute to white matter structural alteration and potential injury. The effects of these processes on the function of distributed cognitive networks, however, are poorly understood. We hypothesized that the extent of magnetic resonance imaging white matter hyperintensities would be associated with visual attentional control in healthy aging, measured using a functional magnetic resonance imaging search task. We assessed cognitively healthy older adults with search tasks indexing processing speed and attentional control. Expanding upon previous research, older adults demonstrate activation across a frontal-parietal attentional control network. Further, greater white matter hyperintensity volume was associated with increased activation of a frontal network node independent of chronological age. Also consistent with previous research, greater white matter hyperintensity volume was associated with anatomically specific reductions in functional magnetic resonance imaging functional connectivity during search among attentional control regions. White matter hyperintensities may lead to subtle attentional network dysfunction, potentially through impaired frontal-parietal and frontal interhemispheric connectivity, suggesting that clinically silent white matter biomarkers of vascular and inflammatory injury can contribute to differences in search performance and brain function in aging, and likely contribute to advanced age-related impairments in cognitive control.

Lower urinary tract dysfunction in patients with brain lesions

Stroke and brain tumor are well-known brain diseases. The incidence of lower urinary tract dysfunction (LUTD) in these patients ranges from 14% to 53%, mostly overactive bladder (OAB), and is higher when the frontal cortex is involved. This presumably reflects damage at the prefrontal cortex, cingulate cortex, and other areas that regulate (mainly inhibit) the micturition reflex. White-matter disease (WMD) is a chronic, bilateral form of cerebrovascular disease, leading to a high prevalence of OAB (up to 90%). Since WMD is particularly common in the elderly, WMD may be one of the anatomic substrates for elderly OAB. Traumatic brain injury and normal-pressure hydrocephalus are rather diffuse brain diseases, which cause OAB with a prevalence rate of 60-95%. Recent neuroimaging studies have shown a relationship between LUTD and the frontal cortex in these diseases. Data on other brain diseases, particularly affecting deep brain structures, are limited. Small infarctions, tumors, or inflammatory diseases affecting the basal ganglia, hypothalamus, and cerebellum lead to mainly OAB. In contrast, similar diseases affecting the brainstem lead to either OAB or urinary retention. The latter reflects damage at the periaqueductal gray and the pontine micturition center that directly relay and modulate the micturition reflex. Urinary incontinence (UI) in brain disease can be divided into two types: neurogenic UI (due to OAB) and functional UI (immobility and loss of initiative/cognition). These two types of UI may occur together, but management differs significantly. Management of neurogenic UI includes anticholinergic drugs that do not penetrate the blood-brain barrier easily. Management of functional UI includes behavioral therapy (timed/prompted voiding with physical assistance and bladder/pelvic floor training) and drugs to treat gait as well as cognition that facilitate continence. These treatments will maximize the quality of life in patients with brain diseases.

The role of carotid intima-media thickness in predicting longitudinal cognitive function in an older adult cohort

BACKGROUND AND PURPOSE

Carotid atherosclerosis is a risk factor for cerebrovascular disease in older adults. Although age-related cognitive decline has been associated with cerebrovascular disease, not much is known about the consequences of carotid atherosclerosis on longitudinal cognitive function. This study examines the longitudinal relationship between atherosclerosis and cognition in a sample of non-demented older subjects using baseline measurements of carotid intima media thickness (CIMT) and annual cognitive measures of executive function (EXEC) and verbal memory (MEM).

METHODS

Baseline measurements included CIMT derived from B-mode carotid artery ultrasound, structural T1-weighted images of white matter hypointensities (WMH), white matter lesions (WML), and cerebral infarct. Hypertension, low-density lipoprotein (LDL), diabetes, and waist to hip ratios (WHR) were included as covariates in our models to control for cerebrovascular risks and central adiposity. Annual composite scores of EXEC and MEM functions were derived from item response theory. Linear mixed models were used to model longitudinal cognitive change.

RESULTS

A significant inverse relationship was found between baseline CIMT and annual EXEC score, but not annual MEM score. Subjects included in the highest 4th quartile of CIMT showed a rate of annual decline in EXEC score that was significant relative to subjects in lower quartile groups (p<0.01). The relationship between the 4th quartile of CIMT and annual EXEC score remained significant after independently adjusting for imaging measures of white matter injury and cerebral infarct.

CONCLUSIONS

Older adult subjects with the highest index of CIMT showed an annual decline in EXEC scores that was significant relative to subjects with lower quartile measurements of CIMT, independent of our measures of white matter injury and cerebral infarct. Our findings suggest that elevated measures of CIMT may mark an atherosclerotic state, resulting in a decline in executive function and not memory in non-demented older adults.

Pathogenesis and treatment of vascular cognitive impairment

SUMMARY 

Vascular cognitive impairment (VCI) defines a continuum of disorders ranging from mild cognitive impairment to full-blown dementia, attributable to cerebrovascular causes. Major morphological types – multi-infarct encephalopathy, strategic infarct type, subcortical arteriosclerotic leukoencephalopathy, multilacunar state, postischemic encephalopathy – result from systemic, cardiac and local large or small vessel disease. Cognitive decline is commonly caused by widespread small cerebrovascular lesions (CVLs) affecting regions/networks essential for cognition, memory and behavior. CVLs often coexist with Alzheimer-type and other pathologies, which interact in promoting dementia, but in many nondemented elderly individuals, mixed brain pathologies are also present. Due to the high variability of CVLs, no validated clinical and neuropathological criteria for VCI are available. Cholinesterase inhibitors and memantine produce small cognitive improvement but without essential effect. Antihypertensive treatment, cardiovascular control and lifestyle modifications reducing vascular risk factors are essential. Given its growing health, social and economic burden, prevention and treatment of VCI are a major challenge of neuroscience.

The overlap between vascular disease and Alzheimer's disease--lessons from pathology

Recent epidemiological and clinico-pathological data indicate considerable overlap between cerebrovascular disease (CVD) and Alzheimer's disease (AD) and suggest additive or synergistic effects of both pathologies on cognitive decline. The most frequent vascular pathologies in the aging brain and in AD are cerebral amyloid angiopathy and small vessel disease. Up to 84% of aged subjects show morphological substrates of CVD in addition to AD pathology. AD brains with minor CVD, similar to pure vascular dementia, show subcortical vascular lesions in about two-thirds, while in mixed type dementia (AD plus vascular dementia), multiple larger infarcts are more frequent. Small infarcts in patients with full-blown AD have no impact on cognitive decline but are overwhelmed by the severity of Alzheimer pathology, while in early stages of AD, cerebrovascular lesions may influence and promote cognitive impairment, lowering the threshold for clinically overt dementia. Further studies are warranted to elucidate the many hitherto unanswered questions regarding the overlap between CVD and AD as well as the impact of both CVD and AD pathologies on the development and progression of dementia.

The relationship of leukoaraiosis and the clinical severity of vascular Parkinsonism

Vascular Parkinsonism (VP) is referred to as secondary Parkinsonian syndrome. It occurs with lacunar state or sub-cortical white matter micro-angiopathy and is highly associated with vascular risk factors and leukoaraiosis, also known as cerebral white matter lesions (WML). This study aimed to assess the prevalence of different vascular risk factors and WML in patients with VP, and their impact on clinical features. Sixty-two consecutive VP patients (70.2 ± 9.2 years) were evaluated for clinical severity using the Unified Parkinson's Disease Rating Scale (UPDRS). WML was assessed and scored on fluid-attenuated inversion recovery T2-weighted (FLAIR) magnetic resonance imaging (MRI). Cerebro-vascular risk factors, WML severity, and the UPDRS for clinical disability were analyzed statistically. There were no associations between WML score and age, sex, hypertension, diabetes, previous stroke, cardiac disease, cigarette smoking, or serum levels of cholesterol and triglyceride. The WML score positively correlated with UPDRS part I (p = 0.035) and part III (p = 0.041) scores. After adjustments for age, gender, stroke history, and use of levodopa, the WML score was associated with the UPDRS total (p = 0.020), part I (p = 0.012), part II (p = 0.039), and part III (p = 0.019) scores. The severity of WML is not associated with conventional vascular risk factors in VP patients but is significantly correlated with the UPDRS total and all sub-scores, which suggests that disruption of the cortico-sub-cortical circuits may lead to impaired mentation, behavior and mood, activities of daily living, and motor performance in these patients.

Cognitive performance in orthostatic hypotension: findings from a nationally representative sample

OBJECTIVES

To compare the cognitive profile of a population representative sample with orthostatic hypotension (OH) with the profile of a sample without.

DESIGN

Cross-sectional analysis of a prospective nationally representative population study.

SETTING

The Irish Longitudinal Study on Ageing (TILDA).

PARTICIPANTS

TILDA participants (N = 5,936; mean age 63 ± 9, 54% female).

MEASUREMENTS

OH was defined as a drop of 20 mmHg or more in systolic blood pressure or of 10 mmHg or more in diastolic blood pressure on standing from a seated position. Cognitive performance was assessed using comprehensive cognitive tests measuring domains of global function, executive function, processing speed, attention, and memory, from which composite standardized scores were computed. Multivariate analysis controlling for potential confounders was performed to compare cognitive performance according to OH status.

RESULTS

Prevalence of OH was 6.1% (95% confidence interval = 5.4-6.7%). A significant negative association between OH status and global cognitive function (b = 0.21, P = .01) and memory (b = 0.26, P = .002) was found in women aged 65 and older after adjustment for demographic characteristics, mental health, cardiovascular disease, and medications (antihypertensive and antipsychotic), but other specific cognitive domains were not affected.

CONCLUSION

OH was associated with poorer global cognitive function and poorer memory, independent of potential confounders, in women in a large population-based sample of older adults. Longitudinal studies with concomitant assessment of cerebral perfusion are needed to determine causal relationships.

Structural imaging measures of brain aging

During the course of normal aging, biological changes occur in the brain that are associated with changes in cognitive ability. This review presents data from neuroimaging studies of primarily "normal" or healthy brain aging. As such, we focus on research in unimpaired or nondemented older adults, but also include findings from lifespan studies that include younger and middle aged individuals as well as from populations with prodromal or clinically symptomatic disease such as cerebrovascular or Alzheimer's disease. This review predominantly addresses structural MRI biomarkers, such as volumetric or thickness measures from anatomical images, and measures of white matter injury and integrity respectively from FLAIR or DTI, and includes complementary data from PET and cognitive or clinical testing as appropriate. The findings reveal highly consistent age-related differences in brain structure, particularly frontal lobe and medial temporal regions that are also accompanied by age-related differences in frontal and medial temporal lobe mediated cognitive abilities. Newer findings also suggest that degeneration of specific white matter tracts such as those passing through the genu and splenium of the corpus callosum may also be related to age-related differences in cognitive performance. Interpretation of these findings, however, must be tempered by the fact that comorbid diseases such as cerebrovascular and Alzheimer's disease also increase in prevalence with advancing age. As such, this review discusses challenges related to interpretation of current theories of cognitive aging in light of the common occurrence of these later-life diseases. Understanding the differences between "Normal" and "Healthy" brain aging and identifying potential modifiable risk factors for brain aging is critical to inform potential treatments to stall or reverse the effects of brain aging and possibly extend cognitive health for our aging society.

The cognitive neuropsychological phenotype of carriers of the FMR1 premutation

The fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder affecting a subset of carriers of the FMR1 (fragile X mental retardation 1) premutation. Penetrance and expression appear to be significantly higher in males than females. Although the most obvious aspect of the phenotype is the movement disorder that gives FXTAS its name, the disorder is also accompanied by progressive cognitive impairment. In this review, we address the cognitive neuropsychological and neurophysiological phenotype for males and females with FXTAS, and for male and female unaffected carriers. Despite differences in penetrance and expression, the cognitive features of the disorder appear similar for both genders, with impairment of executive functioning, working memory, and information processing the most prominent. Deficits in these functional systems may be largely responsible for impairment on other measures, including tests of general intelligence and declarative learning. FXTAS is to a large extent a white matter disease, and the cognitive phenotypes observed are consistent with what some have described as white matter dementia, in contrast to the impaired cortical functioning more characteristic of Alzheimer's disease and related disorders. Although some degree of impaired executive functioning appears to be ubiquitous among persons with FXTAS, the data suggest that only a subset of unaffected carriers of the premutation - both female and male - demonstrate such deficits, which typically are mild. The best-studied phenotype is that of males with FXTAS. The manifestations of cognitive impairment among asymptomatic male carriers, and among women with and without FXTAS, are less well understood, but have come under increased scrutiny.

Reduced glucose uptake and Aβ in brain regions with hyperintensities in connected white matter

Interstitial concentration of amyloid beta (Aß) is positively related to synaptic activity in animal experiments. In humans, Aß deposition in Alzheimer's disease overlaps with cortical regions highly active earlier in life. White matter lesions (WML) disrupt connections between gray matter (GM) regions which in turn changes their activation patterns. Here, we tested if WML are related to Aß accumulation (measured with PiB-PET) and glucose uptake (measured with FDG-PET) in connected GM. WML masks from 72 cognitively normal (age 61.7 ± 9.6 years, 71% women) individuals were obtained from T2-FLAIR. MRI and PET images were normalized into common space, segmented and parcellated into gray matter (GM) regions. The effects of WML on connected GM regions were assessed using the Change in Connectivity (ChaCo) score. Defined for each GM region, ChaCo is the percentage of WM tracts connecting to that region that pass through the WML mask. The regional relationship between ChaCo, glucose uptake and Aß was explored via linear regression. Subcortical regions of the bilateral caudate, putamen, calcarine, insula, thalamus and anterior cingulum had WM connections with the most lesions, followed by frontal, occipital, temporal, parietal and cerebellar regions. Regional analysis revealed that GM with more lesions in connecting WM and thus impaired connectivity had lower FDG-PET (r = 0.20, p<0.05 corrected) and lower PiB uptake (r = 0.28, p<0.05 corrected). Regional regression also revealed that both ChaCo (β = 0.045) and FDG-PET (β = 0.089) were significant predictors of PiB. In conclusion, brain regions with more lesions in connecting WM had lower glucose metabolism and lower Aß deposition.

Parental longevity is associated with cognition and brain ageing in middle-aged offspring

BACKGROUND

offspring of long-lived individuals have lower risk for dementia. We examined the relation between parental longevity and cognition and subclinical markers of brain ageing in community-dwelling adult offspring.

METHODS

offspring participants with both parents in the Framingham Heart Study, aged ≥55 years and dementia-free underwent baseline and repeat neuropsychological (NP) testing and brain magnetic resonance imaging (MRI). Parental longevity was defined as having at least one parent survive to age ≥85 years. To test the association between parental longevity and measures of cognition and brain volumes, we used multivariable linear and logistic regression adjusting for age, sex, education and time to NP testing or brain MRI.

RESULTS

of 728 offspring (mean age 66 years, 54% women), 407 (56%) had ≥1 parent achieve longevity. In cross-sectional analysis, parental longevity was associated with better scores on attention (beta 0.21 ± 0.08, P = 0.006) and a lower odds of extensive white matter hyperintensity on brain MRI (odds ratio 0.59, 95% CI: 0.38, 0.92, P = 0.019). The association with white matter hyperintensity was no longer significant in models adjusted for cardiovascular risk factors and disease. In longitudinal analysis (6.7 ± 1.7 years later), offspring with parental longevity had slower decline in attention (0.18 ± 0.08, P = 0.038), executive function (beta 0.19 ± 0.09, P = 0.031) and visual memory (beta -0.18 ± 0.08, P = 0.023), and less increase in temporal horn volume (beta -0.25 ± 0.09, P = 0.005). The associations persisted in fully adjusted models.

CONCLUSION

parental longevity is associated with better brain ageing in middle-aged offspring.

Extreme deep white matter hyperintensity volumes are associated with African American race

BACKGROUND

African Americans (AAs) have a higher prevalence of extreme ischemic white matter hyperintensities (WMHs) on magnetic resonance imaging (MRI) than do European Americans (EAs) based on the Cardiovascular Health Study (CHS) score. Ischemic white matter disease, limited to the deep white matter, may be biologically distinct from disease in other regions and may reflect a previously observed trend toward an increased risk of subcortical lacunar infarcts in AAs. We hypothesized that extreme deep WMH volume (DWMV) or periventricular volume (PV) may also have a higher prevalence in AAs. Thus, we studied extreme CHS scores and extreme DWMV and PV in a healthy population enriched for cardiovascular disease risk factors.

METHODS

We imaged the brains of 593 subjects who were first-degree relatives of probands with early onset coronary disease prior to 60 years of age. WMHs were manually delineated on 3-tesla cranial MRI by a trained radiology reader; the location and volume of lesions were characterized using automated software. DWMV and PV were measured directly with automated software, and the CHS score was determined by a neuroradiologist. Volumes were characterized as being in the upper 25% versus lower 75% of total lesion volume. Volumes in the upper versus the remaining quartiles were examined for AA versus EA race using multiple logistic regression (generalized estimating equations adjusted for family relatedness) and adjusted for major vascular disease risk factors including age ≥55 years versus <55, sex, current smoking, obesity, hypertension, diabetes and low-density lipoprotein >160 mg/dl.

RESULTS

Participants were 58% women and 37% AAs, with a mean age of 51.5 ± 11.0 years (range, 29-74 years). AAs had significantly higher odds of having extreme DWMVs (odds ratio, OR, 1.8; 95% confidence interval, CI, 1.2-2.9; p = 0.0076) independently of age, sex, hypertension and all other risk factors. AAs also had significantly higher odds of having extreme CHS scores ≥3 (OR, 1.3; 95% CI, 1.1-3.6; p = 0.025). Extreme PV was not significantly associated with AA race (OR, 1.3; 95% CI, 0.81-2.1; p = 0.26).

CONCLUSIONS

AAs from families with early-onset cardiovascular disease are more likely to have extreme DWMVs (a subclinical form of cerebrovascular disease) and an extreme CHS score, but not extreme PV, independently of age and other cardiovascular disease risk factors. These findings suggest that this AA population is at an increased risk for DWMV and may be at an increased risk for future subcortical stroke. Longitudinal studies are required to see if DWMV is predictive of symptomatic subcortical strokes in this population.

Prefrontal cortex and executive functions in healthy adults: a meta-analysis of structural neuroimaging studies

Lesion studies link the prefrontal cortex (PFC) to executive functions. However, the evidence from in vivo investigations in healthy people is mixed, and there are no quantitative estimates of the association strength. To examine the relationship between PFC volume and cortical thickness with executive cognition in healthy adults, we conducted a meta-analysis of studies that assessed executive functions and PFC volume (31 samples,) and PFC thickness (10 samples) in vivo, N=3272 participants. We found that larger PFC volume and greater PFC thickness were associated with better executive performance. Stronger associations between executive functions and PFC volume were linked to greater variance in the sample age but was unrelated to the mean age of a sample. Strength of association between cognitive and neuroanatomical indices depended on the executive task used in the study. PFC volume correlated stronger with Wisconsin Card Sorting Test than with digit backwards span, Trail Making Test and verbal fluency. Significant effect size was observed in lateral and medial but not orbital PFC. The results support the "bigger is better" hypothesis of brain-behavior relation in healthy adults and suggest different neural correlates across the neuropsychological tests used to assess executive functions.

Prefrontal cortex and executive functions in healthy adults: a meta-analysis of structural neuroimaging studies

Lesion studies link the prefrontal cortex (PFC) to executive functions. However, the evidence from in vivo investigations in healthy people is mixed, and there are no quantitative estimates of the association strength. To examine the relationship between PFC volume and cortical thickness with executive cognition in healthy adults, we conducted a meta-analysis of studies that assessed executive functions and PFC volume (31 samples,) and PFC thickness (10 samples) in vivo, N=3272 participants. We found that larger PFC volume and greater PFC thickness were associated with better executive performance. Stronger associations between executive functions and PFC volume were linked to greater variance in the sample age but was unrelated to the mean age of a sample. Strength of association between cognitive and neuroanatomical indices depended on the executive task used in the study. PFC volume correlated stronger with Wisconsin Card Sorting Test than with digit backwards span, Trail Making Test and verbal fluency. Significant effect size was observed in lateral and medial but not orbital PFC. The results support the "bigger is better" hypothesis of brain-behavior relation in healthy adults and suggest different neural correlates across the neuropsychological tests used to assess executive functions.

The independent contributions of cognitive impairment and neuropsychiatric symptoms to everyday function in older adults

The everyday functional capacities of older adults are determined by multiple factors. The primary goal of the present study was to evaluate whether apathy and depression have unique influences on degree of functional impairment, independent of the effects of specific cognitive impairments. Participants included 344 older adults (199 normal, 87 with MCI, 58 with dementia). The Everyday Cognition (ECog) scales were used to measure both global and domain-specific functional abilities. Neuropsychiatric symptoms of depression and apathy were measured by the Neuropsychiatric Inventory (NPI), and specific neuropsychological domains measured included episodic memory and executive functioning. Results indicated that worse memory and executive function, as well as greater depression and apathy, were all independent and additive determinants of poorer functional abilities. Apathy had a slightly more restricted effect than the other variables across the specific functional domains assessed. Secondary analysis suggested that neuropsychiatric symptoms may be more strongly associated with everyday function within cognitively normal and MCI groups, while cognitive impairment is more strongly associated with everyday function in dementia. Thus, a somewhat different set of factors may be associated with functional status across various clinical groups.

Predictors for cortical gray matter volume in stroke patients with confluent white matter changes

BACKGROUND AND PURPOSE

Our previous study found that cortical gray matter (cGM) volume predicted vascular cognitive impairment independent of age-related white matter changes (WMC). We aimed to investigate predictors for cGM volume in ischemic stroke patients with confluent WMC.

METHODS

One-hundred post-stroke patients with confluent WMC were recruited into the study. All volumetric measures were standardized by intracranial volume as volume ratio. Univariate analyses and multivariate linear regression models were used to test relationship of cGM volume with basic demography, vascular risk factors, APOE status, WMC volume (periventricular and deep WMC), infarct measures (volume, number and location) and microbleed (number, presence and location).

RESULTS

After controlling for significant variables in the univariate analyses, multivariate linear regression models found that old age (β=-0.288, p=0.001), low triglyceride (β=0.194, p=0.027), periventricular WMC (PVWMC) (β=-0.392, p<0.001) and presence of thalamic microbleed (β=-0.197, p=0.041) were independently predictive of less cGM volume ratio.

CONCLUSIONS

Age, PVWMC and left thalamic microbleed predict less cGM volume.

Plasma Amylin and Cognition in Diabetes in the Absence and the Presence of Insulin Treatment

Background

Plasma amylin is positively associated with cognitive function in humans. Amylin treatment improves memory in Alzheimer’s mouse models. However, the relationship between plasma amylin, diabetes and cognition is not clear.

Objectives

In this study we examined the concentration of plasma amylin, its relationship with diabetes and cognition.

Material and Method

A cross-sectional, homebound elderly population with data of plasma amylin under fasting condition and cognitive measurements was used.

Results

We found that subjects with a long and chronic duration of diabetes were more likely to take insulin treatment and have reduced secretion of amylin. Compared to non-diabetics, diabetic subjects without insulin treatment had a higher concentration, but those with insulin treatment had a lower concentration, of plasma amylin [median (Q1, Q3): 20 (11.0, 36.2) vs. 25.2 (13.2, 50.6) vs. 15.0 (4.9, 33.8), p<0.0001]. In the whole sample vs. in the absence of diabetes, plasma amylin was positively associated with logical memory delayed recall (β= +0.61, SE=0.25, p=0.02 vs. β=+0.80, SE=0.33, p=0.02) and block design (β=+0.62, SE=0.24, p=0.009 vs. β=+0.93, SE=0.31, p=0.003), and negatively associated with Trailmaking A scores (β= −6.21, SE=1.55, p<0.0001 vs. β=−7.51, SE=1.95, p=0.0001) and Trailmaking B (β= −4.32, SE=2.13, p=0.04 vs. β= −5.86, SE=2.73, p=0.04). All these relationships disappeared in the presence of diabetes regardless the treatment.

Conclusion

This study suggests that secretion of amylin by pancreas compensates and then deteriorates depending on the duration of diabetes. Amylin’s activities for cognition are impaired in the presence of diabetes.

The pathobiology of vascular dementia

Vascular cognitive impairment defines alterations in cognition, ranging from subtle deficits to full-blown dementia, attributable to cerebrovascular causes. Often coexisting with Alzheimer's disease, mixed vascular and neurodegenerative dementia has emerged as the leading cause of age-related cognitive impairment. Central to the disease mechanism is the crucial role that cerebral blood vessels play in brain health, not only for the delivery of oxygen and nutrients, but also for the trophic signaling that inextricably links the well-being of neurons and glia to that of cerebrovascular cells. This review will examine how vascular damage disrupts these vital homeostatic interactions, focusing on the hemispheric white matter, a region at heightened risk for vascular damage, and on the interplay between vascular factors and Alzheimer's disease. Finally, preventative and therapeutic prospects will be examined, highlighting the importance of midlife vascular risk factor control in the prevention of late-life dementia.

Early detection of microstructural white matter changes associated with arterial pulsatility

Increased cerebral blood flow pulsatility is common in vascular dementia and is associated with macrostructural damage to cerebral white matter or leukoaraiosis (LA). In this study, we examine whether cerebral blood flow pulsatility is associated with macrostructural and microstructural changes in cerebral white matter in older adults with no or mild LA and no evidence of dementia. Diffusion Tensor Imaging was used to measure fractional anisotropy (FA), an index of the microstructural integrity of white matter, and radial diffusivity (RaD), a measure sensitive to the integrity of myelin. When controlling for age, increased arterial pulsation was associated with deterioration in both measures of white matter microstructure but not LA severity. A stepwise multiple linear regression model revealed that arterial pulsatility index was the strongest predictor of FA (R = 0.483, adjusted R (2) = 0.220), followed by LA severity, but not age. These findings suggest that arterial pulsatility may provide insight into age-related reduction in white matter FA. Specifically, increased arterial pulsatility may increase perivascular shear stress and lead to accumulation of damage to perivascular oligodendrocytes, resulting in microstructural changes in white matter and contributing to proliferation of LA over time. Changes in cerebral blood flow pulsatility may therefore provide a sensitive index of white matter health that could facilitate the early detection of risk for perivascular white matter damage and the assessment of the effectiveness of preventative treatment targeted at reducing pulsatility.

White matter hyperintensities are associated with visual search behavior independent of generalized slowing in aging

A fundamental controversy is whether cognitive decline with advancing age can be entirely explained by decreased processing speed, or whether specific neural changes can elicit cognitive decline, independent of slowing. These hypotheses are anchored by studies of healthy older individuals where age is presumed the sole influence. Unfortunately, advancing age is also associated with asymptomatic brain white matter injury. We hypothesized that differences in white matter injury extent, manifest by MRI white matter hyperintensities (WMH), mediate differences in visual attentional control in healthy aging, beyond processing speed differences. We tested young and cognitively healthy older adults on search tasks indexing speed and attentional control. Increasing age was associated with generally slowed performance. WMH were also associated with slowed search times independent of processing speed differences. Consistent with evidence attributing reduced network connectivity to WMH, these results conclusively demonstrate that clinically silent white matter injury contributes to slower search performance indicative of compromised cognitive control, independent of generalized slowing of processing speed.

Regional white matter hyperintensities: aging, Alzheimer's disease risk, and cognitive function

White matter hyperintensities (WMH) of presumed vascular origin, as seen on T2-weighted fluid attenuated inversion recovery magnetic resonance imaging, are known to increase with age and are elevated in Alzheimer's disease (AD). The cognitive implications of these common markers are not well understood. Previous research has primarily focused on global measures of WMH burden and broad localizations that contain multiple white matter tracts. The aims of this study were to determine the pattern of WMH accumulation with age, risk for AD, and the relationship with cognitive function utilizing a voxel-wise analysis capable of identifying specific white matter regions. A total of 349 participants underwent T1-weighted and high-resolution T2-weighted fluid attenuated inversion recovery magnetic resonance imaging and neuropsychological testing. Increasing age and lower cognitive speed and flexibility (a component of executive function), were both significantly associated with regional WMH throughout the brain. When age was controlled, lower cognitive speed and flexibility was independently associated with WMH in the superior corona radiata. Apolipoprotein E ε4 and parental family history of AD were not associated with higher burden of WMH. The results contribute to a larger body of literature suggesting that white matter measures are linked with processing speed, and illustrate the utility of voxel-wise analysis in understanding the effect of lesion location on cognitive function.

Is overactive bladder a brain disease? The pathophysiological role of cerebral white matter in the elderly

Small-vessel disease of the brain affecting the deep white matter characteristically manifests with neurological syndromes, such as vascular dementia and vascular parkinsonism. There is, however, compelling evidence to suggest that white matter disease can cause overactive bladder and incontinence, and in some patients these might be the initial manifestation. As white matter disease increases significantly with age, and preferentially affects the prefrontal deep white matter, white matter disease becomes an anatomical substrate in the brain etiology of overactive bladder. Treatment entails the management of small-vessel disease risk factors and anticholinergic drugs that do not easily penetrate the blood-brain barrier, to improve bladder control. In short, when caring for elderly overactive-bladder patients, we should look at both the brain and the bladder.

Characterization of a normal control group: are they healthy?

We examined the health of a control group (18-81years) in our aging study, which is similar to control groups used in other neuroimaging studies. The current study was motivated by our previous results showing that one third of the elder control group had moderate to severe white matter hyperintensities and/or cortical volume loss which correlated with poor performance on memory tasks. Therefore, we predicted that cardiovascular risk factors (e.g., hypertension, high cholesterol) within the control group would account for significant variance on working memory task performance. Fifty-five participants completed 4 verbal and spatial working memory tasks, neuropsychological exams, diffusion tensor imaging (DTI), and blood tests to assess vascular risk. In addition to using a repeated measures ANOVA design, a cluster analysis was applied to the vascular risk measures as a data reduction step to characterize relationships between conjoint risk factors. The cluster groupings were used to predict working memory performance. The results show that higher levels of systolic blood pressure were associated with: 1) poor spatial working memory accuracy; and 2) lower fractional anisotropy (FA) values in multiple brain regions. In contrast, higher levels of total cholesterol corresponded with increased accuracy in verbal working memory. An association between lower FA values and higher cholesterol levels were identified in different brain regions from those associated with systolic blood pressure. The conjoint risk analysis revealed that Risk Cluster Group 3 (the group with the greatest number of risk factors) displayed: 1) the poorest performance on the spatial working memory tasks; 2) the longest reaction times across both spatial and verbal memory tasks; and 3) the lowest FA values across widespread brain regions. Our results confirm that a considerable range of vascular risk factors are present in a typical control group, even in younger individuals, which have robust effects on brain anatomy and function. These results present a new challenge to neuroimaging studies both for defining a cohort from which to characterize 'normative' brain circuitry and for establishing a control group to compare with other clinical populations.

Cognitive and neuroimaging outcomes of different treatment regimens for primary CNS lymphoma

Evaluation of: Doolittle ND, Korfel A, Lubow MA et al. Long-term cognitive function, neuroimaging, and quality of life in primary CNS lymphoma. Neurology 81, 1–9 (2013). This study used a cross-sectional design to assess cognitive function, quality of life and structural brain imaging in primary CNS lymphoma survivors. In total, 80 patients treated with different high-dose methotrexate-based regimens with or without full-dose whole-brain radiotherapy were evaluated at a median of 5.5 years from diagnosis. Survivors treated with high-dose methotrexate-based chemotherapy and whole-brain radiotherapy had lower mean scores on tests of attention, executive function and motor speed, and had more white matter abnormalities on brain imaging in comparison to patients treated with high-dose methotrexate-based regimens without whole-brain radiotherapy. The strengths of the study include the comparisons across treatment modalities and the use of standardized assessment tools. The findings provide further evidence for the increased risk for delayed neurotoxicity following combined modality regimens.

Sleep disturbance correlates with white matter hyperintensity in patients with subcortical ischemic vascular dementia

BACKGROUND

Subcortical ischemic vascular dementia (SIVD) caused by small-artery disease, and hypoperfusion is a major cause of vascular cognitive impairment. Little is known about the relationship between sleep disturbance and white matter hyperintensity (WMH). We investigated the association between sleep disturbance and WMH, measured by magnetic resonance imaging (MRI), in patients with SIVD.

METHODS

Patients with SIVD recruited from our outpatient clinic completed the Sleep Disturbance Symptom Questionnaire (SDSQ) and Geriatric Depression Scale-short form (GDS-S) and underwent brain MRI. Total SDSQ scores were calculated by summing frequency ratings of the instrument's 20 items. We graded WMH on brain MR images using a visual rating scale ranging from 0 (barely detectable) to 9 (extensive changes).

RESULTS

We enrolled 72 patients (31 men, 41 women; mean age, 75.9 ± 7.9 years) with SIVD. The SDSQ scores were positively correlated with WMH grading (r = .337, P = .001) and tended to be associated with higher GDS-S scores (r = .268, P = .022). Patients with diabetes mellitus tended to display higher mean WMH severity than those without diabetes (4.2 vs 3.3, P = .022). After controlling for confounding factors, the multivariate regression model showed that WMH severity was significantly associated with sleep disturbance (P = .002).

CONCLUSIONS

This study showed that manifestations of sleep disturbance were significantly associated with WMH severity, with most symptoms related to daytime hypersomnolence. Disruption of the frontal-subcortical neuronal circuit might play a role in sleep disturbance in patients with SIVD.

Altered pattern of spontaneous brain activity in the patients with end-stage renal disease: a resting-state functional MRI study with regional homogeneity analysis

PURPOSE

To investigate the pattern of spontaneous neural activity in patients with end-stage renal disease (ESRD) with and without neurocognitive dysfunction using resting-state functional magnetic resonance imaging (rs-fMRI) with a regional homogeneity (ReHo) algorithm.

MATERIALS AND METHODS

rs-fMRI data were acquired in 36 ESRD patients (minimal nephro-encephalopathy [MNE], n = 19, 13 male, 37±12.07 years; non-nephro-encephalopathy [non-NE], n = 17, 11 male, 38±12.13 years) and 20 healthy controls (13 male, 7 female, 36±10.27 years). Neuropsychological (number connection test type A [NCT-A], digit symbol test [DST]) and laboratory tests were performed in all patients. The Kendall's coefficient of concordance (KCC) was used to measure the regional homogeneity for each subject. The regional homogeneity maps were compared using ANOVA tests among MNE, non-NE, and healthy control groups and post hoc t -tests between each pair in a voxel-wise way. A multiple regression analysis was performed to evaluate the relationships between ReHo index and NCT-A, DST scores, serum creatinine and urea levels, disease and dialysis duration.

RESULTS

Compared with healthy controls, both MNE and non-NE patients showed decreased ReHo in the multiple areas of bilateral frontal, parietal and temporal lobes. Compared with the non-NE, MNE patients showed decreased ReHo in the right inferior parietal lobe (IPL), medial frontal cortex (MFC) and left precuneus (PCu). The NCT-A scores and serum urea levels of ESRD patients negatively correlated with ReHo values in the frontal and parietal lobes, while DST scores positively correlated with ReHo values in the bilateral PCC/precuneus, MFC and inferior parietal lobe (IPL) (all P<0.05, AlphaSim corrected). No significant correlations were found between any regional ReHo values and disease duration, dialysis duration and serum creatinine values in ESRD patients (all P>0.05, AlphaSim corrected).

CONCLUSION

Diffused decreased ReHo values were found in both MNE and non-NE patients. The progressively decreased ReHo in the default mode network (DMN), frontal and parietal lobes might be trait-related in MNE. The ReHo analysis may be potentially valuable for elucidating neurocognitive abnormalities of ESRD patients and detecting the development from non-NE to MNE.

Dissociable effects of Alzheimer disease and white matter hyperintensities on brain metabolism

IMPORTANCE

Cerebrovascular disease and Alzheimer disease (AD) frequently co-occur and seem to act through different pathways in producing dementia.

OBJECTIVE

To examine cerebrovascular disease and AD markers in relation to brain glucose metabolism in patients with mild cognitive impairment.

DESIGN AND SETTING

Cohort study among the Alzheimer Disease Neuroimaging Initiative clinical sites in the United States and Canada.

PARTICIPANTS

Two hundred three patients having amnestic mild cognitive impairment (74 of whom converted to AD) with serial imaging during a 3-year follow-up period.

MAIN OUTCOMES AND MEASURES

Quantified white matter hyperintensities (WMHs) represented cerebrovascular disease, and cerebrospinal fluid β-amyloid represented AD pathology. Brain glucose metabolism in temporoparietal and frontal brain regions was measured using positron emission tomography with fluorodeoxyglucose F18.

RESULTS

In converters, greater WMHs were associated with decreased frontal metabolism (-0.048; 95% CI, -0.067 to -0.029) but not temporoparietal metabolism (0.010; 95% CI, -0.010 to 0.030). Greater cerebrospinal fluid β-amyloid (per 10-pg/mL increase) was associated with increased temporoparietal metabolism (0.005; 95% CI, 0.000-0.010) but not frontal metabolism (0.002; 95% CI, -0.004 to 0.007) in the same patients. In nonconverters, similar relationships were observed except for a positive association of greater WMHs with increased temporoparietal metabolism (0.051; 95% CI, 0.027-0.076).

CONCLUSIONS AND RELEVANCE

The dissociation of WMHs and cerebrospinal fluid β-amyloid in relation to regional glucose metabolism suggests that these pathologic conditions operate through different and independent pathways in AD that reflect dysfunction in different brain systems. The positive association of greater WMHs with temporoparietal metabolism suggests that these pathologic processes do not co-occur in nonconverters.

Executive dysfunctions in migraine with and without aura: what is the role of white matter lesions?

OBJECTIVE/BACKGROUND

Executive dysfunctions and white matter lesions on magnetic resonance imaging have been reported in migraine. The aim of this study was to determine whether any correlation between these 2 variables exists.

MATERIALS AND METHODS

Forty-four subjects affected by migraine with or without aura were compared with 16 healthy subjects. A battery of neuropsychological tests assessing executive functions was administered to all subjects. Number and total volume of white matter lesions were assessed in the whole brain and in the frontal lobe.

RESULTS

The performances of both groups of migraineurs, with and without aura, were significantly worse when compared with controls on Boston Scanning Test. Moreover, we found lower performances compared with controls respectively on Frontal Assessment Battery in patients with migraine with aura and on Controlled Oral Word Association Test in patients with migraine without aura. Nineteen patients (43.2%) and one control subject (6.2%) had white matter lesions. We did not find any significant correlation between white matter lesions load and neuropsychological performances.

CONCLUSIONS

On the basis of our results, white matter lesions load on magnetic resonance imaging do not seem to contribute to neuropsychological performances deficit in migraineurs.

White matter hyperintensities, exercise, and improvement in gait speed: does type of gait rehabilitation matter?

OBJECTIVES

To examine whether white matter hyperintensities (WMHs) on brain magnetic resonance imaging (MRI) in tracts in older adults with mobility impairment are linked to outcomes of gait rehabilitation interventions.

DESIGN

Twelve-week randomized controlled single-blind trial.

SETTING

University-based mobility research laboratory.

PARTICIPANTS

Ambulatory adults aged 65 and older with mobility impairment.

INTERVENTION

A conventional gait intervention focusing on walking, endurance, balance, and strength (WEBS, n = 21) and a task-oriented intervention focused on timing and coordination of gait (TC, n = 23).

MEASUREMENTS

Self-paced gait speed was measured over an instrumented walkway before and after the intervention, and WMH and brain volumes were quantified on preintervention brain MRI using an automated segmentation process. A white matter tract atlas was overlaid on the segmented images to measure tract WMH volumes, and WMH volumes were normalized to total brain volume. Aggregate WMH volumes in all white matter tracts and individual WMH volumes in specific longitudinal tracts (superior longitudinal fasciculus, inferior longitudinal fasciculus, and fronto-occipital fasciculus) and the cingulum were measured.

RESULTS

Gait speed gains in the TC group were of the same magnitude, independent of WMH volume measures in all except the cingulum, but in the WEBS group, gain in gait speed was smaller with greater overall tract WMH volumes (P < .001) and with greater WMH volume in the three longitudinal tracts (P < .001 to .02).

CONCLUSION

Gains in gait speed with two types of gait rehabilitation are associated with individual differences in WMHs. Task-oriented therapy that targets timing and coordination of gait may particularly benefit older adults with WMHs in brain tracts that influence gait and cognition.

Pathology and pathogenesis of vascular cognitive impairment-a critical update

Vascular cognitive impairment (VCI) [vascular cognitive disorder (VCD), vascular dementia] describes a continuum of cognitive disorders ranging from mild cognitive impairment (MCI) to dementia, in which vascular brain injury involving regions important for memory, cognition and behavior plays an important role. Clinical diagnostic criteria show moderate sensitivity (ca 50%) and variable specificity (range 64-98%). In Western clinical series, VaD is suggested in 8-10% of cognitively impaired elderly subjects. Its prevalence in autopsy series varies from 0.03 to 58%, with means of 8 to 15% (in Japan 22-35%). Major types of sporadic VaD are multi-infarct encephalopathy, small vessel and strategic infarct type dementias, subcortical arteriosclerotic leukoencephalopathy (SAE) (Binswanger), multilacunar state, mixed cortico-subcortical type, granular cortical atrophy (rare), postischemic encephalopathy, and a mixture of cerebrovascular lesions (CVLs). They result from systemic, cardiac and local large or small vessel disease (SVD); their pathogenesis is multifactorial. Hereditary forms of VaD caused by gene mutations are rare. Cognitive decline is commonly associated with widespread small ischemic vascular lesions involving subcortical brain areas (basal ganglia and hemispheral white matter). The lesions affect neuronal networks involved in cognition, memory, and behavior (thalamo-cortical, striato-subfrontal, cortico-subcortical, limbic systems). CVLs often coexist with Alzheimer-type lesions and other pathologies; 25-80% of elderly demented show mixed pathologies. The lesion pattern of "pure" VaD differs from that in mixed dementia (AD + CVLs) suggesting different pathogenesis of both phenotypes. Minor CVLs, except for severe amyloid angiopathy, appear not essential for cognitive impairment in full-blown AD, while both mild AD-type pathology and SVD may interact synergistically in promoting dementia. However, in a large percentage of non-demented elderly individuals, both AD-related and vascular brain pathologies have been reported. Despite recent suggestions for staging and grading CVLs in specific brain areas, due to the high variability of CVLs associated with cognitive impairment, no validated neuropathological criteria are currently available for VaD and mixed dementia. Further clinico-pathological studies and harmonization of neuropathological procedures are needed to validate the diagnostic criteria for VaD and mixed dementia in order to clarify the impact of CVLs and other coexistent pathologies on cognitive impairment as a basis for further successful therapeutic options.

Vulnerable neural systems and the borderland of brain aging and neurodegeneration

Brain aging is characterized by considerable heterogeneity, including varying degrees of dysfunction in specific brain systems, notably a medial temporal lobe memory system and a frontostriatal executive system. These same systems are also affected by neurodegenerative diseases. Recent work using techniques for presymptomatic detection of disease in cognitively normal older people has shown that some of the late life alterations in cognition, neural structure, and function attributed to aging probably reflect early neurodegeneration. However, it has become clear that these same brain systems are also vulnerable to aging in the absence of even subtle disease. Thus, fundamental systemic limitations appear to confer vulnerability of these neural systems to a variety of insults, including those recognized as typical disease and those that are attributed to age. By focusing on the fundamental causes of neural system vulnerability, the prevention or treatment of a wide range of late-life neural dysfunction might be possible.

The human frontal lobes and frontal network systems: an evolutionary, clinical, and treatment perspective

Frontal lobe syndromes, better termed as frontal network systems, are relatively unique in that they may manifest from almost any brain region, due to their widespread connectivity. The understandings of the manifold expressions seen clinically are helped by considering evolutionary origins, the contribution of the state-dependent ascending monoaminergic neurotransmitter systems, and cerebral connectivity. Hence, the so-called networktopathies may be a better term for the syndromes encountered clinically. An increasing array of metric tests are becoming available that complement that long standing history of qualitative bedside assessments pioneered by Alexander Luria, for example. An understanding of the vast panoply of frontal systems' syndromes has been pivotal in understanding and diagnosing the most common dementia syndrome under the age of 60, for example, frontotemporal lobe degeneration. New treatment options are also progressively becoming available, with recent evidence of dopaminergic augmentation, for example, being helpful in traumatic brain injury. The latter include not only psychopharmacological options but also device-based therapies including mirror visual feedback therapy.

Impairment of executive cognitive control in type 2 diabetes, and its effects on health-related behavior and use of health services

We evaluated whether, among persons with type 2 diabetes: (1) impaired executive cognitive functioning (ECF) is more common than among people without diabetes; (2) ECF is associated with the capacity to engage in instrumental health-related behaviors; and (3) worse ECF is associated with increased health services utilization. A population-based sample of 1,063 older people was interviewed regarding medical history and health services utilization; participants were administered the Mini Mental State Exam and the Behavioral Dyscontrol Scale, a measure of ECF. Participants with diabetes performed more poorly on cognitive measures than those without diabetes. Among those with diabetes, lower ECF was associated with more outpatient care and with ever having been in a nursing home. Impaired behavioral self-regulation may affect the capacity to engage in behaviors that could improve clinical status, resulting in greater health services use. The findings suggest the possibility of a positive feedback loop, with ECF deficits adversely affecting adherence, in turn leading to greater cognitive impairment-an issue for future research.

Confirmatory factor analysis of the Neuropsychological Assessment Battery of the LADIS study: a longitudinal analysis

Age-related white matter changes have been associated with cognitive functioning, even though their role is not fully understood. This work aimed to test a 3-factor model of the neuropsychological assessment battery and evaluate how the model fit the data longitudinally. Confirmatory factor analysis (CFA) was used to investigate the dimensions of a structured set of neuropsychological tests administered to a multicenter, international sample of independent older adults (LADIS study). Six hundred and thirty-eight older adults completed baseline neuropsychological, clinical, functional and motor assessments, which were repeated each year for a 3-year follow-up. CFA provided support for a 3-factor model. These factors involve the dimensions of executive functions, memory functions, and speed and motor control abilities. Performance decreased in most neuropsychological measures. Results showed that executive functioning, memory and speed of motor abilities are valid latent variables of neuropsychological performance among older adults, and that this structure is relatively consistent longitudinally, even though performance decreases with time.

Association of gray matter atrophy with age, β-amyloid, and cognition in aging

Both cognitive aging and β-amyloid (Aβ) deposition, a pathological hallmark of Alzheimer's disease, are associated with structural and cognitive changes in cognitively normal older people. To examine independent effects of age and Aβ deposition on cognition and brain structure in aging, 83 cognitively normal older adults underwent structural magnetic resonance imaging scans and neuropsychological tests and were classified as negative (PIB-) or positive (PIB+) for Aβ deposition using the radiotracer Pittsburgh compound B (PIB). Weighted composite discriminant scores represented subjects' cognition. Older adults showed age-related gray matter (GM) atrophy across the whole brain regardless of Aβ deposition. Amyloid burden within PIB+ subjects, however, was associated with GM atrophy in the frontal, parietal, and temporal cortices. Associations between cognition and volume in PIB- subjects were primarily seen throughout frontal regions and the striatum, while, in PIB+ subjects, these associations were seen in orbital-frontal and hippocampal regions. Furthermore, in PIB- subjects, cognition was related to putaminal volume, but not to hippocampus, while, in PIB+ subjects, cognition was related to hippocampal volume, but not to putamen. These findings highlight differential age and Aβ effects on brain structure, indicating effects of age and Aβ that operate somewhat independently to affect frontostriatal and medial temporal brain systems.

White matter hyperintensities in Parkinson's disease: do they explain the disparity between the postural instability gait difficulty and tremor dominant subtypes?

Background

Brain white matter hyperintensities (WMHs) commonly observed on brain imaging of older adults are associated with balance and gait impairment and have also been linked to cognitive deficits. Parkinson’s disease (PD) is traditionally sub-classified into the postural instability gait difficulty (PIGD) sub-type, and the tremor dominant (TD) sub-type. Considering the known association between WMHs and axial symptoms like gait disturbances and postural instability, one can hypothesize that WMHs might contribute to the disparate clinical sub-types of patients with PD.

Methods

110 patients with PD underwent a clinical evaluation and a 3T MRI exam. Based on the Unified Parkinson Disease Rating Scale, the patients were classified into motor sub-types, i.e., TD or PIGD, and scores reflecting PIGD and TD symptoms were computed. We compared white matter burden using three previously validated methods: one using a semi-quantitative visual rating scale in specific brain regions and two automated methods.

Results

Overall, MRI data were obtained in 104 patients. The mean WMHs scores and the percent of subjects with lesions in specific brain regions were similar in the two subtypes, p = 0.678. The PIGD and the TD scores did not differ even when comparing patients with a relatively high burden of WMHs to patients with a relatively low burden. Across most of the brain regions, mild to moderate correlations between WMHs and age were found (r = 0.23 to 0.41; p<0.021). Conversely, no significant correlations were found between WMHs and the PIGD score or disease duration. In addition, depressive symptoms and cerebro-vascular risk factors were similar among the two subtypes.

Conclusions

In contrast to what has been reported previously among older adults, the present study could not demonstrate any association between WMHs and the PIGD or TD motor sub-types in patients with PD.

Clinical, imaging, and pathological heterogeneity of the Alzheimer's disease syndrome

With increasing knowledge of clinical in vivo biomarkers and the pathological intricacies of Alzheimer's disease (AD), nosology is evolving. Harmonized consensus criteria that emphasize prototypic illness continue to develop to achieve diagnostic clarity for treatment decisions and clinical trials. However, it is clear that AD is clinically heterogeneous in presentation and progression, demonstrating variable topographic distributions of atrophy and hypometabolism/hypoperfusion. AD furthermore often keeps company with other conditions that may further nuance clinical expression, such as synucleinopathy exacerbating executive and visuospatial dysfunction and vascular pathologies (particularly small vessel disease that is increasingly ubiquitous with human aging) accentuating frontal-dysexecutive symptomatology. That some of these atypical clinical patterns recur may imply the existence of distinct AD variants. For example, focal temporal lobe dysfunction is associated with a pure amnestic syndrome, very slow decline, with atrophy and neurofibrillary tangles limited largely to the medial temporal region including the entorhinal cortex. Left parietal atrophy and/or hypometabolism/hypoperfusion are associated with language symptoms, younger age of onset, and faster rate of decline - a potential 'language variant' of AD. Conversely, the same pattern but predominantly affecting the right parietal lobe is associated with a similar syndrome but with visuospatial symptoms replacing impaired language function. Finally, the extremely rare frontal variant is associated with executive dysfunction out of keeping with degree of memory decline and may have prominent behavioural symptoms. Genotypic differences may underlie some of these subtypes; for example, absence of apolipoprotein E e4 is often associated with atypicality in younger onset AD. Understanding the mechanisms behind this variability merits further investigation, informed by recent advances in imaging techniques, biomarker assays, and quantitative pathological methods, in conjunction with standardized clinical, functional, neuropsychological and neurobehavioral evaluations. Such an understanding is needed to facilitate 'personalized AD medicine', and eventually allow for clinical trials targeting specific AD subtypes. Although the focus legitimately remains on prototypic illness, continuing efforts to develop disease-modifying therapies should not exclude the rarer AD subtypes and common comorbid presentations, as is currently often the case. Only by treating them as well can we address the full burden of this devastating dementia syndrome.

Cerebral white matter hyperintensities in the prediction of cognitive decline and incident dementia

Cerebral white matter hyperintensities (WMH), detected in vivo with magnetic resonance imaging (MRI), are commonly used to assess cerebrovascular burden in cognitive impairment. However, the association between WMH and cognition is not consistent across the literature. The present review examines evidence from published longitudinal studies. We reviewed the PubMed data base from January 1990 to March 2013 and included studies investigating the association of WMH with (1) the risk of dementia in the general population, (2) the risk of conversion to dementia in the mild cognitive impairment (MCI) population, and (3) cognitive decline in the general population. WMH were associated with all types of dementia in the general population, but not in MCI patients. Results are discrepant for global decline. WMH appear to be early predictors of the risk of dementia, but this association appears to be modulated by cognitive reserve, age and the spatial distribution of lesions. There are, however, some limits in the use of WMH as a marker of vascular burden. In addition to their ischaemic origin, WMH may be the result of co-occurring morbidity. Further research is needed to elucidate to what extent WMH actually reflect vascular risk to evaluate the likely efficacy of interventions specifically targeting WMH reduction.