Mattias Haglund

Cerebral amyloid angiopathy, white matter lesions and Alzheimer encephalopathy - A histopathological assessment

To test the hypothesis that the cerebral amyloid angiopathy (CAA) of Alzheimer’s disease (AD) is quantitatively associated with white matter lesions (WML), the brains of 63 demented patients exhibiting varying degrees of Alzheimer encephalopathy (AE) were examined, along with those of 10 nondemented control cases. The ratio of amyloid-positive to amyloid-negative vessels in the leptomeninges of the frontal pole from each patient was calculated subsequent to microscopical examination, and the severity of WML was graded according to previously published criteria. In AD cases without a significant component of vascular dementia, the level of CAA was found to correlate with the degree of WML diagnosed and graded by neuropathology. Neither age nor severity of AE correlated significantly with WML. There may be several reasons for the conflicting results of this study vis-à-vis earlier investigations; the roles played by different methods of staining, CAA quantitation and patient subgroup selection are also discussed.

Locus ceruleus degeneration is ubiquitous in Alzheimer's disease: possible implications for diagnosis and treatment.

Degeneration of the locus ceruleus (LC) and decreased cortical levels of norepinephrine are common findings in Alzheimer’s disease (AD), but their significance is unknown. Because the noradrenergic system is accessible to pharmacological intervention, the role of LC degeneration and noradrenergic dysfunction in the pathogenesis and clinical manifestations of AD needs clarification. Hypothetically, loss of noradrenergic innervation could cause microvascular dysfunction and manifest as ischemia. The objectives of this study were to develop a scale for assessment of LC degeneration and to determine whether degeneration of the LC correlates quantitatively with either duration of clinical dementia, overall severity of AD pathology or with measures of ischemic non‐focal white matter disease (WMD) in AD. This report is a pathological follow‐up of a clinical longitudinal dementia study of 66 consecutive cases of AD without admixture of vascular dementia (VaD) from the Lund Longitudinal Dementia Study, neuropathologically diagnosed between 1990 and 1999. Ten cases of VaD were included for comparative purposes. No correlation between degree of LC degeneration and duration of dementia, AD or WMD severity was found. LC degeneration was significantly more severe in the AD group than in the VaD group. Even though LC degeneration was not associated with WMD or the severity of AD pathology in this AD material, we suggest that clinical studies on the consequences of noradrenergic dysfunction are warranted. Treatment augmenting noradrenergic signaling is available and safe. The marked difference in the level of LC degeneration between AD and VaD cases suggests that LC degeneration could be used as a diagnostic marker of AD.

Severe Cerebral Amyloid Angiopathy Characterizes an Underestimated Variant of Vascular Dementia.

Cerebral amyloid angiopathy (CAA) is a frequent finding on neuropathological examination of patients with Alzheimer’s disease (AD). A recent study from our laboratory showed that CAA also frequently occurred in vascular dementia with additional mild Alzheimer encephalopathy (VaD-ae, i.e. Alzheimer pathology that does not fulfill criteria for AD). Because CAA is associated with cerebral hemorrhages and infarctions, it is of significant interest to confirm or dismiss the hypothesis that CAA contributes clinically in the many patients that present with VaD-ae. Therefore, we examined entire temporal lobes of 11 VaD-ae cases and 11 age-matched AD cases with Aβ immunohistochemistry. Six of 11 VaD-ae cases had severe CAA, more extensive than in any AD case. There was a trend toward more cortical infarctions in this group, indicating that CAA in VaD may be of clinical importance and an underestimated cause of dementia.

White matter mapping in Alzheimer's disease: A neuropathological study

White matter disease (WMD) with pervasive non-focal subtotal tissue loss is frequently seen in Alzheimers disease (AD) upon neuropathological examination. Although WMD has varying effects on AD symptoms, accurate clinical detection is difficult due partly to scarcity of correlative structural imaging and histopathological studies. Neuropathological studies of WMD severity and distribution have been conducted earlier using semi-quantitative methods. A technique for quantifying WMD objectively in large white matter areas, based on optical density (OD) measurements on images of scanned whole-brain sections, was developed and was validated using conventional microscopic assessment. Altogether, 16 AD cases with concomitant WMD (AD-WMD) and 9 cases of AD without WMD (AD-only) were analysed. The OD values correlated significantly with the neuropathological severity of WMD and were significantly lower in AD-WMD than in AD-only in frontal, frontoparietal, temporal and parietal white matter but not in the occipital white matter, the frontal OD difference being greatest. Useful baseline information on WMD distribution in AD to relate to in vivo imaging results was obtained.

Differential deposition of amyloid beta peptides in cerebral amyloid angiopathy associated with Alzheimer's disease and vascular dementia.

Cerebral amyloid angiopathy (CAA) caused by deposition of amyloid β (Aβ) peptides in the cerebrovasculature, involves degeneration of normal vascular components and increases the risk of infarction and cerebral hemorrhage. Accumulating evidence suggests that sporadic CAA is also a significant contributor to cognitive decline and dementia in the elderly. However, the mechanisms by which CAA arises are poorly understood. While neuronal sources of Aβ peptides are sufficient to cause CAA in transgenic mice overexpressing the amyloid precursor protein, there is reason to believe that in aging man, vascular disease modulates the disease process. To better understand CAA mechanisms in dementia, we assessed the frontal cortex of 62 consecutive cases of Alzheimer’s disease (AD), vascular dementia (VaD), and mixed dementia (MD) using immunohistochemistry with antibodies to Aβ, smooth muscle actin and the carboxyl-terminal peptides to detect Aβ(40) and Aβ(42). While vascular Aβ deposition was invariably associated with smooth muscle degeneration as indicated by absence of smooth muscle cell actin reactivity, VaD/MD cases exhibited markedly more vascular Aβ(42) deposits and smooth muscle actin loss compared to AD cases with similar degrees of CAA and Aβ(40) deposition. This suggests that distinct mechanisms are responsible for the differential deposition of Aβ in CAA associated with AD and that associated with ischemic/cerebrovascular disease. It is plausible that experimental studies on the effects of cerebrovascular disease on Aβ production and elimination will yield important clues on the pathogenesis of CAA.

Brain tissue microarrays in dementia research: White matter microvascular pathology in Alzheimer's disease

Tissue microarrays (TMA) consist of up to 1000 cylindrical tissue cores from different donor paraffin blocks relocated into one recipient block, allowing for efficient histopathological studies by fluorescence in situ hybridization, RNA in situ hybridization or immunohistochemistry. On the background of the increasing interest of the TMA technique in cancer research and the suggestion of its application also in studies of non‐neoplastic intracranial disorders, the technique was applied to pathologic white matter in AD brains. Eight cases with AD and concomitant white matter pathology were neuropathologically diagnosed on whole brain coronal slides. The TMA technique was used to grade severity of white matter pathology and to quantify small vessels with traditional staining and immunohistochemical markers. These measurements were compared with the whole brain neuropathological assessment. The technique produced good results with preserved tissue structures as confirmed by the whole brain evaluation. Severity of white matter pathology evaluated on the TMA cores correlated negatively with small vessel quantities, and statistically significant differences in vessel quantities paralleled different grades of white matter pathology. It is concluded that the TMA technique could be further utilized in studies of dementing disorders, and may have its advantages in large, clinically well‐characterized materials (e.g. in quantitative mapping of white matter changes).

A methodological study of locus coeruleus degeneration in dementing disorders.

BACKGROUND Degeneration of the locus coeruleus (LC) of the brain stem is a recognized phenomenon in Alzheimers disease (AD), in dementia with Lewy bodies (DLB), and in Parkinsons disease with dementia (PDD). Prior studies have suggested that LC degeneration can be used to differentiate various dementing disorders histologically, but the paucity of methodological data may hamper systematic research on this nucleus. PURPOSE The purpose of this study was to evaluate various approaches to quantifying LC degeneration in dementing disorders, and to inform future decisions regarding the most appropriate method for diagnostics and research. METHODS 105 LCs from brains of demented individuals with AD, DLB/PDD, vascular dementia (VaD), mixed dementia (AD+VaD), or frontotemporal lobar degeneration (FTLD) were examined, and the extent of LC degeneration was assessed using macroscopic evaluation, cell counting, and two degeneration scales. Scores were compared across diagnostic categories; diagnostic utility and intra- and interobserver reliability were assessed. RESULTS AD and DLB/PDD were associated with greater LC damage using either assessment method, significantly different from VaD and FTLD. Macroscopic appearance was informative, but cell counting was more sensitive and specific. The degeneration scales did not add significant diagnostic value over cell counting and were associated with greater observer variability. CONCLUSIONS The LC degenerates in certain dementia subtypes, especially in AD and DLB/PDD. Macroscopic assessment of the LC postmortem can be used to differentiate between disorders associated with degeneration (AD, DLB/PDD) or sparing (VaD) of the LC, but counting LC cells in a representative pontine section is the most appropriate method by which to assess LC degeneration.