Quantification of myelin loss in frontal lobe white matter in vascular dementia, Alzheimer's disease, and dementia with Lewy bodies

Long-term incidence of depression and predictors of depressive symptoms in older stroke survivors

BACKGROUND

Depression is common and an important consequence of stroke but there is limited information on the longer-term relationship between these conditions.

AIMS

To identify the prevalence, incidence and predictors of depression in a secondary-care-based cohort of stroke survivors aged over 75 years, from 3 months to up to 10 years post-stroke.

METHOD

Depression was assessed annually by three methods: major depression by DSM-IV criteria, the self-rated Geriatric Depression Scale (GDS) and the observer-rated Cornell scale.

RESULTS

We found the highest rates, 31.7% baseline prevalence, of depressive symptoms with the GDS compared with 9.7% using the Cornell scale and 1.2% using DSM-IV criteria. Incidence rates were 36.9, 5.90 and 4.18 episodes per 100 person years respectively. Baseline GDS score was the most consistent predictor of depressive symptoms at all time points in both univariate and multivariate analyses. Other predictors included cognitive impairment, impaired activities of daily living and in the early period, vascular risk factor burden and dementia.

CONCLUSIONS

Our results emphasise the importance of psychiatric follow-up for those with early-onset post-stroke depression and long-term monitoring of mood in people who have had a stroke and remain at high risk of depression.

Axonal degeneration in Alzheimer's disease: when signaling abnormalities meet the axonal transport system

Alzheimer's disease (AD) is characterized by progressive, age-dependent degeneration of neurons in the central nervous system. A large body of evidence indicates that neurons affected in AD follow a dying-back pattern of degeneration, where abnormalities in synaptic function and axonal connectivity long precede somatic cell death. Mechanisms underlying dying-back degeneration of neurons in AD remain elusive but several have been proposed, including deficits in fast axonal transport (FAT). Accordingly, genetic evidence linked alterations in FAT to dying-back degeneration of neurons, and FAT defects have been widely documented in various AD models. In light of these findings, we discuss experimental evidence linking several AD-related pathogenic polypeptides to aberrant activation of signaling pathways involved in the phosphoregulation of microtubule-based motor proteins. While each pathway appears to affect FAT in a unique manner, in the context of AD, many of these pathways might work synergistically to compromise the delivery of molecular components critical for the maintenance and function of synapses and axons. Therapeutic approaches aimed at preventing FAT deficits by normalizing the activity of specific protein kinases may help prevent degeneration of vulnerable neurons in AD.

Brain microvascular accumulation and distribution of the NOTCH3 ectodomain and granular osmiophilic material in CADASIL

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), the most common form of familial brain arteriopathy, is associated with deposition of granular osmiophilic material (GOM). We used immunohistochemistry and immunogold electron microscopy (EM) to examine the distribution of GOM and NOTCH3 ectodomain (N3ECD) protein in microvasculature of brain gray matter and white matter in patients with CADASIL, non-CADASIL hereditary small-vessel disease and sporadic age-related degenerative disease, and comparable-age controls. We observed intense immunostaining patterns with 2 different anti-N3ECD antibodies in CADASIL but not in young and older controls or other small-vessel disease patients. In addition, CADASIL samples exhibited immunoreactivity in arterial walls and in most capillaries. Electron microscopy revealed profound and widespread extracellular distribution of 0.2- to 2-μm GOM deposits associated with meningeal vessels and perforating arteries and arterioles. Granular osmiophilic material was adjacent to capillaries even within white matter. Immunogold EM with antibody A1-1 to N3ECD revealed abundant particles in GOM within microvessels, vascular smooth muscle cell membranes, and perivascular cells. Granular osmiophilic material did not exhibit immunogold labeling for smooth muscle α-actin or collagen IV. These results showed the specificity of the antibodies and confirm the predominant localization of N3ECD within GOM deposits. The extensive distribution of N3ECD-GOM complexes within meninges, arteries, arterioles, and particularly capillaries in the brains of CADASIL patients suggests that NOTCH3 fragments are major components of GOM deposits, which may be eliminated via perivascular routes.

Is Alzheimer's a disease of the white matter?

PURPOSE OF REVIEW

Alzheimer's disease has long been primarily considered a disease of gray matter. However, convergent evidence has suggested that white matter abnormalities are also important components of Alzheimer's disease. We undertook a review of the recent findings of Alzheimer's disease related white matter aberrations identified in patients with Alzheimer's disease and using in-vitro and in-vivo models, and discuss the potential causes of white matter damage in Alzheimer's disease. In doing so, we aim to provide a renewed insight into white matter changes in Alzheimer's disease and related dementias.

RECENT FINDINGS

Neuroimaging studies have found that patients with preclinical Alzheimer's disease have widespread white matter abnormalities at a stage similar to those reported in Alzheimer's disease, whereas gray matter structures were relatively intact. In addition, demyelination of the white matter is reported to occur prior to the presence of amyloid-β plaques and neurofibrillary tangles in the presymptomatic stages of Alzheimer's disease. Furthermore, in a mouse model of Alzheimer's disease, axonal disease due to impaired axonal transport was shown to precede and drive downstream production and aggregation of amyloid β peptides.

SUMMARY

White matter abnormalities not only represent an early neuropathological event in Alzheimer's disease but may also play an important role in the pathogenesis and diagnosis of Alzheimer's disease.

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.

Traumatic brain injury in young rats leads to progressive behavioral deficits coincident with altered tissue properties in adulthood

Traumatic brain injury (TBI) affects many infants and children, and results in enduring motor and cognitive impairments with accompanying changes in white matter tracts, yet few experimental studies in rodent juvenile models of TBI (jTBI) have examined the timeline and nature of these deficits, histologically and functionally. We used a single controlled cortical impact (CCI) injury to the parietal cortex of rats at post-natal day (P) 17 to evaluate behavioral alterations, injury volume, and morphological and molecular changes in gray and white matter, with accompanying measures of electrophysiological function. At 60 days post-injury (dpi), we found that jTBI animals displayed behavioral deficits in foot-fault and rotarod tests, along with a left turn bias throughout their early developmental stages and into adulthood. In addition, anxiety-like behaviors on the zero maze emerged in jTBI animals at 60 dpi. The final lesion constituted only ∼3% of brain volume, and morphological tissue changes were evaluated using MRI, as well as immunohistochemistry for neuronal nuclei (NeuN), myelin basic protein (MBP), neurofilament-200 (NF200), and oligodendrocytes (CNPase). White matter morphological changes were associated with a global increase in MBP immunostaining and reduced compound action potential amplitudes at 60 dpi. These results suggest that brain injury early in life can induce long-term white matter dysfunction, occurring in parallel with the delayed development and persistence of behavioral deficits, thus modeling clinical and longitudinal TBI observations.

Decreased oligodendrocyte nuclear diameter in Alzheimer's disease and Lewy body dementia

To better understand the pathogenesis of dementia, it is important to understand histopathologic changes in neurodegenerative diseases because they might highlight key aspects of the degenerative process. In this study, the nuclear diameter of neurons and oligodendrocytes in selected temporal lobe areas were determined in autopsy tissue sections from patients with Alzheimer's disease (AD), Lewy body dementia (LBD) and controls. Our morphometric studies targeted neurons in the CA4 region of the pyramidal cell layer of the hippocampus, neurons in the granular layer of the dentate gyrus and oligodendrocytes in parahippocampal white matter. Mean neuronal nuclear diameters were not different among the studied groups. However, our studies revealed a statistically significant reduction of mean oligodendrocyte nuclear diameter in AD and LBD relative to controls. The reduction of the mean nucleus diameter of oligodendrocytes in LBD was independent of the presence of associated AD pathology in LBD. These findings for the first time identify decreased oligodendrocyte nucleus diameter as a morphologic feature of AD and LBD and may lead to a better understanding of the role of oligodendrocytes in AD and LBD pathogenesis.

Transgenic expression of intraneuronal Aβ42 but not Aβ40 leads to cellular Aβ lesions, degeneration, and functional impairment without typical Alzheimer's disease pathology

An early role of amyloid-β peptide (Aβ) aggregation in Alzheimer's disease pathogenesis is well established. However, the contribution of intracellular or extracellular forms of Aβ to the neurodegenerative process is a subject of considerable debate. We here describe transgenic mice expressing Aβ1-40 (APP47) and Aβ1-42 (APP48) with a cleaved signal sequence to insert both peptides during synthesis into the endoplasmic reticulum. Although lower in transgene mRNA, APP48 mice reach a higher brain Aβ concentration. The reduced solubility and increased aggregation of Aβ1-42 may impair its degradation. APP48 mice develop intracellular Aβ lesions in dendrites and lysosomes. The hippocampal neuron number is reduced already at young age. The brain weight decreases during aging in conjunction with severe white matter atrophy. The mice show a motor impairment. Only very few Aβ1-40 lesions are found in APP47 mice. Neither APP47 nor APP48 nor the bigenic mice develop extracellular amyloid plaques. While intracellular membrane expression of Aβ1-42 in APP48 mice does not lead to the AD-typical lesions, Aβ aggregates develop within cells accompanied by considerable neurodegeneration.

Cerebral hypoperfusion accelerates cerebral amyloid angiopathy and promotes cortical microinfarcts

Cortical microinfarcts (CMIs) observed in brains of patients with Alzheimer’s disease tend to be located close to vessels afflicted with cerebral amyloid angiopathy (CAA). CMIs in Alzheimer’s disease are preferentially distributed in the arterial borderzone, an area most vulnerable to hypoperfusion. However, the causal association between CAA and CMIs remains to be elucidated. This study consists of two parts: (1) an observational study using postmortem human brains (n = 31) to determine the association between CAA and CMIs, and (2) an experimental study to determine whether hypoperfusion worsens CAA and induces CMIs in a CAA mouse model. In postmortem human brains, the density of CMIs was 0.113/cm² in mild, 0.584/cm² in moderate, and 4.370/cm² in severe CAA groups with a positive linear correlation (r = 0.6736, p < 0.0001). Multivariate analysis revealed that, among seven variables (age, disease, senile plaques, neurofibrillary tangles, CAA, atherosclerosis and white matter damage), only the severity of CAA was a significant multivariate predictor of CMIs (p = 0.0022). Consistent with the data from human brains, CAA model mice following chronic cerebral hypoperfusion due to bilateral common carotid artery stenosis induced with 0.18-mm diameter microcoils showed accelerated deposition of leptomeningeal amyloid β (Aβ) with a subset of them developing microinfarcts. In contrast, the CAA mice without hypoperfusion exhibited very few leptomeningeal Aβ depositions and no microinfarcts by 32 weeks of age. Following 12 weeks of hypoperfusion, cerebral blood flow decreased by 26% in CAA mice and by 15% in wild-type mice, suggesting impaired microvascular function due to perivascular Aβ accumulation after hypoperfusion. Our results suggest that cerebral hypoperfusion accelerates CAA, and thus promotes CMIs.

Staging and natural history of cerebrovascular pathology in dementia

OBJECTIVE

Most pathologic studies indicate that significant vascular changes are found in the majority of elderly persons, either alone or in association with neurodegenerative processes such as Alzheimer disease (AD) or dementia with Lewy bodies (DLB). Cumulative burden of cerebrovascular lesions can explain cognitive decline described as vascular cognitive impairment, but because there is a lack of consensus in the best way to quantify vascular pathology, the relationship between cognitive decline and cerebrovascular disease remains uncertain. We developed a rating scheme for cerebrovascular lesions using postmortem brains from patients with dementia from 2 European tertiary care memory clinics.

METHODS

A total of 135 brains with a neuropathologic diagnosis of vascular dementia (VaD) (n = 26), AD + VaD (n = 39), DLB + VaD (n = 21), AD + DLB + VaD (n = 9), AD (n = 19), and DLB (n = 21) were investigated in this study. Cerebrovascular lesions were rated on large sections from the hippocampus, the temporal lobe, the frontal lobe, and basal ganglia.

RESULTS

In patients with dementia, vessel wall modifications such as arteriolosclerosis or amyloid angiopathy are the most common and presumably the earliest changes. Modifications in perivascular spaces and myelin loss are the next most common. Lacunar or regional infarcts may occur as a consequence of an independent process or in the final phase of small vessel diseases.

CONCLUSION

A staging system based on this conceptual model of cerebrovascular pathology could enable the neuropathologic quantification of the cerebrovascular burden in dementia. Further studies are needed to determine whether this system can be used in large-scale studies to understand clinical-cerebrovascular pathologic correlations.

Long term incidence of dementia, predictors of mortality and pathological diagnosis in older stroke survivors

Greater understanding of the risk factors and mechanisms of incident dementia in stroke survivors is needed for prevention and management. There is limited information on the long-term consequences and forms of incident dementia in older stroke survivors. We recruited 355 patients aged >75 years from hospital-based stroke registers into a longitudinal study 3 months after stroke. At baseline none of the patients had dementia. Patients were genotyped for apolipoprotein E and assessed annually for cognition and development of incident dementia over up to 8 years of follow-up. The effect of baseline vascular risk factors upon incidence of dementia and mortality were estimated by Cox proportional regression analyses adjusted for age and gender. Standard neuropathological examination was performed to diagnose the first 50 cases that came to autopsy. We found that the median survival from the date of the index stroke was 6.72 years (95% confidence intervals: 6.38–7.05). During the follow-up of a mean time of 3.79 years, 23.9% of subjects were known to have developed dementia and 76.1% remained alive without dementia or died without dementia. The incidence of delayed dementia was calculated to be 6.32 cases per 100 person years whereas that for death or dementia was 8.62. Univariate and multivariate regression analyses showed that the most robust predictors of dementia included low (1.5 standard deviations below age-matched control group) baseline Cambridge Cognitive Examination executive function and memory scores, Geriatric Depression Scale score and three or more cardiovascular risk factors. Autopsy findings suggested that remarkably ≥75% of the demented stroke survivors met the current criteria for vascular dementia. Demented subjects tended to exhibit marginally greater neurofibrillary pathology including tauopathy and Lewy bodies and microinfarcts than non-demented survivors. Despite initial improvements in cognition following stroke in older stroke survivors, risk of progression to delayed dementia after stroke is substantial, but is related to the presence of vascular risk factors. Careful monitoring and treatment of modifiable vascular risk factors may be of benefit in preventing post-stroke dementia in the general population.

Suitability of the Montreal cognitive assessment versus the mini-mental state examination in detecting vascular cognitive impairment

The Mini-Mental State Examination (MMSE) has been criticized as being an insufficient screening test for patients with vascular cognitive impairment because of its insensitivity to visuospatial and executive functional deficits. The Montreal Cognitive Assessment (MoCA) was designed to be more sensitive to such deficits, and thus may be a superior screening instrument for vascular cognitive impairment. Twelve patients with extensive leukoaraiosis detected on magnetic resonance imaging (average age, 76.0 ± 8.7 years) underwent neurologic and cognitive testing, including MMSE and the Japanese version of the MoCA (MoCA-J). Accepted cutoff scores of <27 for the MMSE and <26 for the MoCA-J were taken to indicate cognitive impairment. Z-scores were calculated to evaluate the discriminating ability of individual MMSE and MoCA-J subtest scores. Although there was a strong correlation between the total MMSE and total MoCA-J scores (r = 0.90; P < .0001), MMSE scores were skewed toward the higher end of the range (range, 18-30; median, 28), whereas MoCA-J scores were normally distributed (range, 9-28; median, 21). Of the 7 patients with an unimpaired MMSE score, 6 (86%) had an impaired MoCA-J score. Z-scores were >5 for 4 MMSE subtests (orientation, registration, naming, and language) but for only 1 MoCA-J subtest (naming). The MoCA-J better discriminated cognitive status in subjects with extensive leukoaraiosis. Our findings suggest that the MoCA-J is more sensitive than the MMSE in screening for cognitive impairment in patients with subcortical vascular cognitive impairment.

White matter myelin loss in the brains of aged dogs

The significance of cerebral white matter (WM) demyelination in the cognitive decline of elderly humans is disputed. Cognitive decline also occurs in aged dogs, although the age-related changes that occur in the canine cerebral WM are yet to be studied, particularly with regard to their relevance to the WM alterations of elderly humans. The present study revealed age-dependent myelin loss in the frontal lobe WM of canine brains. The accumulation of ceroid-lipofuscin-laden phagocytes was observed in the perivascular spaces of the WM and was correlated with the decrease in myelination. Also, myelin basic protein was detected in some of the vacuoles of these phagocytes. In the WM, beta-amyloid (Aβ) was deposited focally in capillary walls, and colocalized with apolipoprotein E (Apo E). Note that the dog is homozygous for Apo E4, which genotype is related to capillary CAA in humans. These findings indicate that WM demyelination occurs in aged dogs as well as in aged humans, hence WM alterations may account for age-related behavioral changes of the dog. In conclusion, dogs are useful for chronological studies of age-related WM changes.

Longitudinal magnetization transfer imaging in mild to severe Alzheimer disease

BACKGROUND AND PURPOSE

MTI has been proposed as a sensitive technique for studying microstructural brain tissue changes in patients with AD, but the course of these changes over time is largely unknown. We therefore used a placebo-controlled study of memantine to follow the evolution of tissue damage in AD by means of MTR measurements and investigated how MTR changes were related to brain atrophy and cognition.

MATERIALS AND METHODS

Twenty-eight patients (76.5 ± 5.8 years) with mild to moderate AD underwent MTI, brain volume measurements, and cognitive testing at baseline and after 6 and 12 months. Nineteen healthy individuals (73.3 ± 3.2 years) served as controls. MTI was performed with a 2-minute protocol that was optimized for an enhanced MT effect and reduced motion sensitivity. Global and regional MTR measurements served as correlations with brain volumes and the MMSE score.

RESULTS

AD patients had significantly lower global MTR values than controls, and showed a consistent and significant MTR reduction in all regions investigated over a period of 12 months. These MTR changes were paralleled by a brain tissue loss of 2.2% per year. Associations between MTR and cognition were found for the hippocampus, putamen, and thalamus, and were more pronounced in the left hemisphere.

CONCLUSIONS

MTI in AD allows the assessment of ongoing global and regional brain damage independent of atrophy, and therefore appears to be a valuable marker for disease-related tissue changes.

Selective white matter abnormalities in a novel rat model of vascular dementia

Rats subjected to bilateral common carotid artery (CCA) occlusion or 2-vessel occlusion (2VO) have been used as animal models of subcortical ischemic vascular dementia. However, this model possesses an inherent limitation in that cerebral blood flow (CBF) drops too sharply and substantially after ligation of CCAs. To circumvent such hypoxic-ischemic conditions, we tested implantation of the ameroid constrictor device on bilateral CCAs of male Wistar-Kyoto rats and more precisely replicated chronic cerebral hypoperfusion by gradual narrowing of the CCAs (2-vessel gradual occlusion; 2VGO). The acute cerebral blood flow reduction and resultant inflammatory responses observed in the 2VO rats were eliminated in the 2VGO rats. Thus, chronic cerebral hypoperfusion was segregated, and induced selective white matter changes with relatively preserved neurovascular coupling and substantially less metabolic and histological derangements in the gray matter including the hippocampus. This led to significant spatial working memory impairment of a magnitude similar to the 2VO rats at 28 days postoperation. The 2VGO model may more closely mimic cognitive impairment subsequent to selective white matter damage.

Lessons from a mouse model characterizing features of vascular cognitive impairment with white matter changes

With the demographic shift in age in advanced countries inexorably set to progress in the 21st century, dementia will become one of the most important health problems worldwide. Vascular cognitive impairment is the second most common type of dementia after Alzheimer's disease and is frequently responsible for the cognitive decline of the elderly. It is characterized by cerebrovascular white matter changes; thus, in order to investigate the underlying mechanisms involved in white matter changes, a mouse model of chronic cerebral hypoperfusion has been developed, which involves the narrowing of the bilateral common carotid arteries with newly designed microcoils. The purpose of this paper is to provide a comprehensive summary of the achievements made with the model that shows good reproducibility of the white matter changes characterized by blood-brain barrier disruption, glial activation, oxidative stress, and oligodendrocyte loss following chronic cerebral hypoperfusion. Detailed characterization of this model may help to decipher the substrates associated with impaired memory and move toward a more integrated therapy of vascular cognitive impairment.

The alterations of oligodendrocyte, myelin in corpus callosum, and cognitive dysfunction following chronic cerebral ischemia in rats

Although the white matter lesions, so called leuko-araiosis, often seen in elderly people have been gaining attention due to their association with cognitive dysfunction (CD) and high risk of incident stroke, the pathological significance of these lesions still remains controversial. Therefore, in the present study, we investigated the alterations in oligodendrocytes (OLG), including oligodendrocytes progenitor cells (OPCs), myelin, and CD following chronic cerebral ischemia in rats. SD rats were subjected to bilateral common carotid artery occlusion. Immunohistochemical staining was performed at 2, 4, 6, 8, and 12weeks after the induction of ischemia with anti-NG2 (OPCs), anti-GST-π (OLG), and anti-MBP antibodies in paramedian corpus callosum (CC). CD was assessed by the Morris water maze test. There was a significant decrease in the number of GST-π positive cells at 2weeks after the start of ischemia compared with that seen in the sham group. There was a significant increase of the number of NG2 positive cells at 4weeks in the ischemia group compared with the sham group. In the ischemic group, the amount of MBP was observed to have decreased significantly at each time point compared with the sham group. CD was observed in the ischemic group than that in the sham group at all time points. Our results indicate that remyelination is strongly correlated with the recovery of cognitive dysfunction following chronic cerebral ischemia.

Quadriplegia recovery after hemi-section and transplant model of spinal cord at the level of C5 and C6

A spinal cord hemi-section with a homologous transplant of medullar tissue at the level of C5-C6 and preservation of the anterior spinal artery was used to evaluate the histological characteristics such as quantity and quality of axons, myelin index and blood vessels after quadriplegia recovery. Vascular changes after spinal injury results in severe endothelial damage, axonal edema, neuronal necrosis and demyelinization as well as cysts and infarction. Preservation of the anterior spinal artery has demonstrated clinical recuperation; therefore, in addition to the lesion we included a homologous transplant to visualize changes at a cellular level. Two groups of dogs (hemi-section and transplant) went through a traumatic spinal cord hemi-section of 50% at the level of C5-C6. The transplant group formed by animals which simultaneously had 4 mm of spinal cord removed and the equal amount substituted from a donor animal at the level of C5-C6 corresponding to the half right side; both preserving the anterior spinal artery. Histological evaluation of all groups took place at days 3 (acute) and 28 (chronic) post-operation. Changes of degeneration and axonal regeneration were found in the hemi-section and transplant groups at acute and chronic time, as well as same quadriplegia recovery at chronic time in the hemi-section and transplant groups which closely related to mechanisms which participate in regeneration and functional recuperation due to the preservation of the anterior spinal artery and presence of new blood vessels.

Frontal lobe white matter hyperintensities and neurofibrillary pathology in the oldest old

BACKGROUND

Current studies suggest an interaction between vascular mechanisms and neurodegenerative processes that leads to late-onset Alzheimer disease (AD). We tested whether AD pathology was associated with white matter hyperintensities (WMH) or cerebral infarcts in the oldest old individuals.

METHODS

Brains from 132 subjects over 85 years old, who came to autopsy from the Vantaa 85+ population-based cohort, were scanned by postmortem MRI and examined for neuropathologic changes. Coronal images were analyzed to determine the degree of frontal and parietal periventricular WMH (PVWMH) and deep WMH (DWMH) and cerebral infarcts. Neuropathologic variables included Consortium to Establish a Registry for Alzheimer's Disease scores for neuritic plaques and Braak staging among subjects in 5 groups: normal aging (NA), borderline with insufficient AD pathology, AD, AD plus other pathology, and other primary degenerative diseases.

RESULTS

Frontal DWMH were detected in >50% of the sample. Both frontal PVWMH and DWMH were significantly more extensive in the AD group compared to the NA group or the NA and borderline groups combined. Frontal PVWMH and DWMH were also associated with increased Braak staging (p = 0.03) and the neuritic plaque load (p = 0.01). Further analysis revealed there were a greater number of cerebral infarcts associated with frontal DWMH (p = 0.03) but not with frontal PVWMH.

CONCLUSIONS

Our study showed an association between neurofibrillary pathology and frontal PVWMH and DWMH (rather than parietal), as a surrogate of small vessel disease, particularly in very old community-dwelling individuals.

The overlap between neurodegenerative and vascular factors in the pathogenesis of dementia

There is increasing evidence that cerebrovascular dysfunction plays a role not only in vascular causes of cognitive impairment but also in Alzheimer's disease (AD). Vascular risk factors and AD impair the structure and function of cerebral blood vessels and associated cells (neurovascular unit), effects mediated by vascular oxidative stress and inflammation. Injury to the neurovascular unit alters cerebral blood flow regulation, depletes vascular reserves, disrupts the blood-brain barrier, and reduces the brain's repair potential, effects that amplify the brain dysfunction and damage exerted by incident ischemia and coexisting neurodegeneration. Clinical-pathological studies support the notion that vascular lesions aggravate the deleterious effects of AD pathology by reducing the threshold for cognitive impairment and accelerating the pace of the dementia. In the absence of mechanism-based approaches to counteract cognitive dysfunction, targeting vascular risk factors and improving cerebrovascular health offers the opportunity to mitigate the impact of one of the most disabling human afflictions.

Focal demyelination in Alzheimer's disease and transgenic mouse models

We have investigated alterations in myelin associated with Abeta plaques, a major pathological hallmark of Alzheimer's disease (AD), in human tissue and relevant transgenic mice models. Using quantitative morphological techniques, we determined that fibrillar Abeta pathology in the grey matter of the neocortex was associated with focal demyelination in human presenilin-1 familial, sporadic and preclinical AD cases, as well as in two mouse transgenic models of AD, compared with age-matched control tissue. This demyelination was most pronounced at the core of Abeta plaques. Furthermore, we found a focal loss of oligodendrocytes in sporadic and preclinical AD cases associated with Abeta plaque cores. In human and transgenic mice alike, plaque-free neocortical regions showed no significant demyelination or oligodendrocyte loss compared with controls. Dystrophic neurites associated with the plaques were also demyelinated. We suggest that such plaque-associated focal demyelination of the cortical grey matter might impair cortical processing, and may also be associated with aberrant axonal sprouting that underlies dystrophic neurite formation.