Martin Sjöbeck

Alzheimer’s Disease and the Cerebellum: A Morphologic Study on Neuronal and Glial Changes

Structural manifestations of Alzheimer’s disease (AD) including neuronal loss were investigated in 12 cases of AD and in 10 healthy age-matched controls, with focus on the cerebellum. Linear Purkinje cell (PC) density was measured in the vermis and cerebellar hemispheres. Neurons were also counted in the inferior olivary nucleus. In vermis of the AD cases, the mean PC number was significantly lower (p = 0.019) than in the controls. The neurons in the inferior olive were similarly fewer, though not significantly (p = 0.13). Molecular layer gliosis and atrophy in the vermis was clearly severer in AD than in the controls. Features typical of cerebral Alzheimer encephalopathy (plaques, tangles and microvacuolization) were inconspicious. The structural cerebellar changes in the AD cases were thus neuronal loss, atrophy and gliosis, judged to represent the disease process, and with a main involvement in the vermis. This may be reflected in some of the symptoms and signs seen in AD, signs that are generally overlooked or judged to be of noncerebellar origin.

MRI with diffusion tensor imaging post-mortem at 3.0 T in a patient with frontotemporal dementia.

The formalin-fixed brain of a patient with clinically diagnosed frontotemporal dementia (FTD) was examined post-mortem using magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) at 3.0 T. Frontotemporal atrophy as well as bilateral frontal white matter abnormalities were seen. The white matter changes were slightly more extensive on DTI than on conventional MRI. Correlation with histopathology of the corresponding regions revealed typical frontal lobe degeneration of non-Alzheimer type, with mild frontotemporal degeneration in the outer cortical layers and a moderate frontal white matter gliosis with demyelination. Post-mortem MRI/DTI with histopathologic correlation will enhance our understanding of the basis of white matter changes observed in dementia patients and may improve the in vivo MRI/DTI diagnostic assessment in FTD.

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.

Glial levels determine severity of white matter disease in Alzheimer's disease: a neuropathological study of glial changes.

The morphological components of cerebral white matter disease (WMD) were studied in 17 cases of clinically diagnosed dementia and neuropathologically verified Alzheimers disease (AD) with concomitant WMD. The distribution of grey and white matter changes was evaluated and overall as well as regional severity was graded. Total glial numbers in frontal white matter were counted using a light microscope. Oligodendrocyte and astrocyte quantities as well as astrocytic reactivity were assessed from frontal and parietal lobe white matter using a computer assisted morphometric method. The AD–WMD group was compared with 10 nondemented age‐matched controls. Astrocyte/oligodendrocyte ratio (AOR) was calculated, total glial counts and AOR were compared with severity of WMD, and Alzheimer encephalopathy grade was subjectively assessed. Astrocytic numbers, AOR and astrocytic reactivity proved to be significantly higher in the demented group, whereas oligodendrocytic and total glial counts were significantly lower. Furthermore, AOR proved to be positively correlated with severity of WMD, whereas no association was found with Alzheimer encephalopathy. We conclude that WMD in dementia, for example, of the type seen in AD, can easily be detected, measured and graded quantitatively, with AOR being a significant indicator of the severity of changes. This could serve as a tool for differentiating white matter pathologies in dementia and may be the basis for recognition of the mildest white matter changes with new imaging methods, and enable potential clinical intervention.

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.

Diffusion tensor MRI post mortem demonstrated cerebral white matter pathology.

Sirs: Cerebral white matter changes are a challenge to investigators of dementia, because of their high prevalence and alleged clinical importance in the dementing disease process. Findings of ischemic and other white matter alterations on neuroimaging and in neuropathology are difficult to match adequately. The new MR technique, diffusion tensor imaging (DTI) has the potential to become a powerful tool for the detection of anisotropy-related alterations in tissues, including subtle and diffuse white matter changes in the aged [3] and the demented. A DTI study of ischemic leukoaraiosis in demented patients demonstrated abnormal diffusion pleomorphism, possibly reflecting true morphological tissue damage, i. e. tract disarrangement, in areas on conventional MRI of so-called normalappearing white matter at some distance from white matter lesions [4]. Furthermore, impaired frontal white matter integrity measured by DTI fractional anisotropy (FA) values was reported in individuals with Alzheimer’s disease [1]. These findings match those of other studies attesting to histopathological frontal white matter pathology in cases with Alzheimer’s disease [6]. Data such as these remain to be correlated with DTI, conventional MRI and neuropathological followup in the same group of individuals. The aim of this study was primarily to demonstrate the feasibility of post mortem DTI examination of human cerebral white matter and secondly to correlate the diffusion values obtained with the results from neuropathological assessments. The results were compared with the findings on conventional MRI. The brains from two individuals with dementia and neuroradiologically observed white matter disease during life were selected for post mortem DTI. The brains were fixed in 6 % formaldehyde for 6 weeks prior to the DTI investigation. They were rinsed and placed in a water container for the MR examination. Special care was taken to eliminate air-cavities and bubbles within the ventricles and on the surface of the brain. All scanning was performed at room temperature (approximately 23°C). Imaging was performed in a Siemens Magnetom Allegra 3.0 Tesla scanner. Conventional imaging protocols with T1-weighted and T2-weighted spin echo, T2-weighted fluid attenuation inversion recovery and three dimensional (3D) T1-weighted magnetization prepared rapid gradient echo sequences were used. Full brain coverage was obtained for the 2D sequences by scanning 22 slices with a slice thickness of 6 mm and was also obtained for the 3D sequence. A diffusion imaging protocol based on a segmented EPI pulse sequence with diffusion-encoding performed in six different directions, according to the dual gradient method (xz, -xz, yz, y-z, xy and -xy) [5], and two diffusion sensitivities (b-values 0 and 1000 s/mm2) were used. Slice positioning was similar to that of the conventional protocols, but with the long scan time required for DTI, a limited number of slices were positioned according to the areas of interest identified on the MR images. Five and seven slices were obtained for the two brains, respectively. The total scan time for one repetition of one slice was 1 minute and 20 seconds, using an echo time of 72 ms and a repetition time 1000 ms, respectively. Postprocessing of diffusion images was carried out using a home-developed diffusion-analyse program based on interactive data language (IDL, ©Research Systems, Inc) allowing pixel-wise calculation of the mean apparent diffusion coefficient (ADC) and the fractional anisotropy (FA) index [3]. Evaluation of the calculated ADC and FA maps were performed using regions of interest (ROIs) positioned in areas of suspected pathology and in areas of normal appearance. The brains were re-immersed in formaldehyde solution and were shortly thereafter cut in 1-cm thick whole brain coronal slices, which were paraffin-embedded, sectioned and stained for the detection of pathological alterations, in particular within the white matter, for which Luxol Fast Blue myelin staining with Cresyl violet counterstaining was used. A histopathological analysis of the entire brains was performed, with particular focus on type and degree of white matter changes. In 15 central regions of interest, the white matter was graded as microscopically normal, or as exhibiting mild, moderate or severe histopathology (Fig. 1), according to quantitative scales and qualitative alteration profiles regularly assessed in the department [2, 6]. DTI investigation of the two brains revealed in one case patchy and in the other diffuse-confluent white matter alterations, reflecting lacunar infarcts with perifocal gradient pathology vis-à-vis an adLETTER TO THE EDITORS

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.

Alzheimer's disease (AD) and executive dysfunction. A case-control study on the significance of frontal white matter changes detected by diffusion tensor imaging (DTI).

White matter (WM) changes are frequently seen on structural imaging in AD but the clinical relevance of these changes is uncertain. Frontal WM pathology is often observed upon neuropathological examination in AD. Since frontal cortical/sub-cortical pathology is known to relate to executive dysfunction, the aim was to elucidate if frontal WM changes in AD correlated with executive dysfunction. In all, 15 AD patients and 15 age-matched control cases were investigated in the study, which covered conventional magnetic resonance imaging (MRI), DTI, neuropsychiatric and neuropsychological examinations. Reduced performance on neuropsychological testing of executive function correlated significantly with an increasing degree of frontal WM changes detected by DTI in the AD group, while no such correlation was observed for the controls. Conventional semi-quantitative MRI assessment did not correlate with results on neuropsychological testing of executive function in any of the groups. The structural correlate to certain dimensions of executive dysfunction in AD patients could be related to changes in the deep frontal WM. DTI appears to be more sensitive in the detection of clinically significant WM alterations than conventional semi-quantitative MRI.

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).

Long-Term Follow-Up in Depressed Patients Treated With Electroconvulsive Therapy.

Design: Our aim was to study the long-term effects of electroconvulsive therapy (ECT) in depression. A total of 55 patients were followed-up 20 to 24 years after an ECT series; 13 patients were still alive, and 10 agreed to participate in the study. All 55 patients had been investigated with clinical and neuropsychological assessment and with neurophysiological measurements and with regional cerebral blood flow (rCBF) and EEG before the first ECT, 6 months later, and after approximately 1 year. These investigations were repeated in the 10 patients. Results: Before the original ECT series, all patients had suffered from severe mood disorder. At follow-up, the 10 patients showed no clear signs of mood disorder or cognitive impairment. There was a slightly subnormal performance in working memory and in verbal as well as visual episodic memory on all 3 occasions after the ECT series. The rCBF measurement showed a significant average CBF decrease from the first to the last measurement. There was, moreover, a significant rCBF decrease in frontal areas at the last measurement compared with the 3 previous assessments. Conclusion: All ten patients followed-up 20 to 24 years after an ECT series were mentally healthy and thus besides a moderate visual memory dysfunction, no severe side effects were observed with clinical and neuroimaging techniques.