Progression of Clinical Deterioration
and Pathological Changes in Patients
With Alzheimer Disease Evaluated
at Biopsy and Autopsy
Pier Luigi Di Patre, MD; Stephen L. Read, MD; Jeffrey L. Cummings, MD; Uwamie Tomiyasu, MD; Luiza M. Vartavarian, MS; Diana L. Secor, MS; Harry V. Vinters, MD
Objectives:To quantify the progression of senile plaques, neurofibrillary tangles, cerebral amyloid angi-opathy, and microglial activation in the cortex and white matter of patients with Alzheimer disease evaluated at both biopsy and subsequent autopsy and correlate these changes with the progression of neurologic impair-ment.
Setting:Academic referral center for patient with Alz-heimer disease.
Patients:Four patients meeting the clinical criteria for Alzheimer disease, enrolled in a pilot study for the evalu-ation of response to intracerebroventricular administra-tion of bethanechol chloride. The patients were fol-lowed up until death occurred and autopsy was performed. Results:All 4 patients had progressive deterioration from
the time of biopsy to autopsy (9-11 years). Pathological investigations showed a striking increase in the density of senile plaques and neurofibrillary tangles in 2 of 4 pa-tients from biopsy to autopsy, and a significant increase in microglial activation in 1 of 4 cases. Severity of cere-bral amyloid angiopathy varied significantly among pa-tients, 1 of whom displayed striking amyloid deposition with associated subcortical white matter atrophy. Conclusions:These unique data demonstrate that the progressive neurologic impairment in Alzheimer dis-ease is accompanied by a significant incrdis-ease in senile plaque and neurofibrillary tangle counts in the frontal cortex and, possibly in some patients, by increased mi-croglial cell activation. Cerebral amyloid angiopathy was associated with significant white matter disease. Arch Neurol. 1999;56:1254-1261
T
HE COGNITIVEdecline thatcharacterizes Alzheimer dis-ease (AD) is associated with the presence of numerous senile plaques (SPs) and neurofibrillary tangles (NFTs) within the neocortex, hippocampus, and some sub-cortical nuclei.1-4However, the temporal evolution of these pathological changes and their precise correlation with the progres-sion of intellectual impairment are unre-solved issues.5They have been addressed by several studies, most of which, owing to their cross-sectional design, were able to ob-tain pathological and clinical information at only 1 point in time.6-8The progression of pathological changes, and how these cor-relate with concomitant mental decline, was indirectly extrapolated from the available data, with all the difficulties inherent in such an approach. A solution to these difficul-ties is to carry out longitudinal studies in which concurrent pathological and clini-cal investigations are performed in
indi-vidual patients at 2 or more distinct time points, such as at biopsy and autopsy, so that information can be obtained about the extent and nature of the changes that have occurred in the interval between the neu-ropathological determinations. To the best of our knowledge, only 2 studies are avail-able in the English-language literature on the progression of AD changes from bi-opsy to autbi-opsy.9,10One of these studies9 reported on an examination of 5 patients, whose autopsy examination took place 3 to 7 years after biopsy, while the second study10followed up 4 patients for 21 to 47 months from biopsy to autopsy. In both studies, morphometric measurements of the density of cortical SPs and NFTs failed to show significant changes between biopsy and autopsy, while the patients mani-fested a marked progression of their cog-nitive deterioration during the period considered.
This study reports clinical and patho-logical observations on 4 patients with AD ORIGINAL CONTRIBUTION
who originally were enrolled in a therapeutic trial to test the effects of intracerebroventricular (ICV) administra-tion of the cholinergic agonist bethanechol.11Senile plaques and NFTs were assessed in a biopsy specimen taken from the right frontal cortex and, subsequently, in adjacent ar-eas of the cortex examined at autopsy 9 to 11 years after
the biopsy procedure. Also, the degree of cerebral amy-loid angiopathy and microglial cell density were studied by immunohistochemistry for Ab amyloid and CD68 (a marker for microglia and histiocytes). The progression of these changes will be described in conjunction with the time course of the cognitive and functional decline.
PATIENTS AND METHODS
SUBJECTS
The subjects described in this article were originally part of a pilot dose-response study of ICV infusion of bethane-chol as previously described.11All of the patients were
men. Each had a thorough medical and neuropsychiatric evaluation prior to biopsy from a gyrus of the right pre-frontal cortex during placement of the ICV catheter; the clinical diagnosis of AD was confirmed pathologically using the criteria outlined by Khachaturian.12Autopsy
examination was subsequently performed on 4 patients (patients 1, 3, 4, and 5 using the numerical designation of the Bethanechol Trial11). Their characteristics are
summa-rized inTable 1. The period between biopsy and autopsy was 9 years for patients 1 and 5 and 11 years for patients 3 and 4. At the initial neuropsychiatric evaluation prior to biopsy, patients 1 and 5 scored 18 on the Mini-Mental State Examination (MMSE)13and were rated 1 on the
Clinical Dementia Rating Scale (CDRS)14; patients 3 and 4
scored 27 on the MMSE and and were rated 0.5 on the CDRS. Clinically, they met the National Institute of Neu-rological Disorders and Stroke–Alzheimer’s Disease and Related Disorders Association criteria for a diagnosis of probable AD15and Diagnostic and Statistical Manual of
Mental Disorders, Third Edition criteria for primary degen-erative dementia.16
TISSUE PROCESSING
Extensive articles17-20have already been published on the
biopsy findings of all patients in the Bethanechol Trial, in-cluding a detailed description of tissue processing and immunohistochemical procedures. Biopsy and autopsy ma-terials were fixed in 10% buffered formalin. After 1-cm-thick sections of brain had been obtained at autopsy, a sample of prefrontal cortex was removed in the immedi-ate vicinity of the biopsy site, but without including the biopsy scar. The brains were also processed for routine his-tology. Blocks were taken bilaterally from the frontal, tem-poral, parietal, and occipital cortex, basal ganglia, hippo-campus, diencephalon, and brainstem. Sections were stained using a modified Bielschowsky technique and hematoxylin-eosin; also, immunohistochemistry for Ab amyloid and CD68 was carried out using standard techniques, as pre-viously described.18
ASSESSMENT OF DENSITIES OF SPs AND NFTs
Counts of NFTs and SPs were performed on both biopsy and autopsy specimens by 2 investigators (P.L.D.P. and L.M.V.), without knowledge of which autopsy specimen matched which biopsy specimen. Using a graticule,
counting of SPs and NFTs was performed at magnifica-tion3200 on Bielschowsky-stained sections and the counts were expressed per square millimeter of tissue. In both biopsy and autopsy specimens, 5 to 6 cortical areas spanning the whole cortical thickness were selected so as to cover the entire depth of the cortex in the selected areas. Both sulcal depths and crests of gyri were included in these assessments in roughly equal numbers. The interobserver variability in SP and NFT counts was within a 5% to 10% range.
EVALUATION OF AMYLOID IMMUNOHISTO-CHEMISTRY AND MICROGLIAL DENSITY
Biopsy and autopsy sections immunostained with antibod-ies to Ab and CD68 were semiquantitatively evaluated for the presence of intraparenchymal and vascularb-amyloid deposition and microglial density. The frontal cortex from the autopsy of 2 age-matched subjects with no history of neurologic disease and 2 patients with AD (autopsy tissue only available) were used for comparison with the cases in this study. Density of CD68+microglia were graded as “low,”
“moderate,” or “high.” Ratings were based on consensus observations.
ASSESSMENT OF APOE GENOTYPE
Genomic DNA was extracted from the paraffin sections of the brains available at autopsy, according to a procedure described previously.21Briefly, paraffin sections were treated
with xylene to dissolve the paraffin. The tissue was then centrifuged, treated with 100% ethanol, and digested with proteinase K (final concentration, 200 mg/mL) in a buffer containing 50-mmol/L Tris (pH 8.5), 1-mmol/L EDTA, 0.5% to 1.0% sodium dodecyl sulfate, and 0.1-mmol/L sodium chloride at 55oC for 3 hours. Proteinase K was inactivated
by heating the tubes for 30 minutes at 95oC. The
superna-tant was treated with 5-mol/L of potassium acetate and sub-sequently with 7.5-mol/L ammonium acetate and 100% etha-nol for at least 2 hours at –80oC. The DNA pellet was
resuspended in Tris-EDTA (pH 7.8), and absorbance was measured in a spectrophotometer of 260 and 280 nm. Poly-merase chain reaction amplification and APOE-restriction isotyping were carried out following the method of Hix-son and Vernier.22
STATISTICAL ANALYSIS
RESULTS
PROGRESSION OF COGNITIVE AND FUNCTIONAL DETERIORATION
At enrollment and biopsy, all 4 patients had retired but were living at home with a spouse, with some degree of independence in activities of daily living. Detailed neu-ropsychologic testing (S.L.R., unpublished data) con-firmed cognitive deficits in short- and long-term memory, language, ability to copy drawings, problem solving, and sequential thinking. As a benchmark, enrollment MMSE was 27 for patients 3 and 4 and 18 for patients 1 and 5 (Table 1). Postoperative complications included menin-gitis and seizures in patient 1, hemorrhage with mild paresis and seizures in patient 5. Patients 3 and 4 had uncomplicated postoperative courses.
Assessment of the immediate (2-year) postopera-tive period demonstrated a differential response to ICV bethanechol. Patients 3 and 5 had a positive response that was confirmed by a second trial of dose variation.23These patients were able to return home for 4 and 5 years, re-spectively, before long-term care was required. Patients 1 and 4 had poor overall response dominated by depres-sion due to bethanechol.24
By 2 years after operation, the dementia had re-sumed a monotonic progressive course in all patients that continued relentlessly until death. All required nursing home care in their last years. Mini-Mental State Exami-nation declined to zero prior to death in all 4 patients and all were dependent for personal activities of daily liv-ing. Although duration of postoperative survival was simi-lar, the rate of decline was more rapid in patients 3 and 4 compared with patients 1 and 5.
GROSS PATHOLOGY AT AUTOPSY
In all the patients’ brains, no evidence of acute intracra-nial hemorrhage, traumatic injury, or meningeal inflam-mation was identified. Atherosclerotic changes of branches of the circle of Willis were insignificant. No recent or re-mote infarcts were found, the only regions of encepha-lomalacia being at the biopsy site. The substantia nigra and locus ceruleus were normally pigmented.
In patient 1, evidence of mild cortical atrophy was present, most prominent in the frontal lobes, hippo-campi, and parahippocampal gyri. On coronal sections, a catheter tract was seen at 3 cm from the frontal pole, surrounded by an area of encephalomalacia of gray and white matter (Figure 1, A). The brain of patient 3 was also affected by extremely advanced cortical atrophy. The tip of the indwelling catheter was surrounded by a cavi-tary lesion measuring 2 cm in greatest diameter. Sam-pling of the cortex for SP and NFT counting was per-formed as close as possible to the site of the catheter but at a sufficient distance to exclude the area of gliosis sur-rounding the biopsy cavity. The brain of patient 4 dis-played the most advanced degree of cerebral atrophy, as-sociated with striking ventricular dilatation (Figure 1, B) and shrinkage of the subcortical white matter. In this brain, the catheter had previously been removed, and no evidence of a catheter track could be appreciated on gross or microscopic examination. In patient 5, severe diffuse cortical atrophy was present, with extreme narrowing of the gyri, approaching the appearance of “knife-edge at-rophy” in some regions. An indwelling catheter was iden-tified, with surrounding mild encephalomalacia and yel-low-orange discoloration, suggestive of blood pigment deposition (Figure 1, C).
DENSITY OF SPs
Figure 2shows the densities of SPs at biopsy and au-topsy for all cases. We found a marked, statistically sig-nificant increase of SP density in patients 3, 4, and 5, with counts at autopsy being 2.5, 3.0, and 8.4 times, respec-tively, those at biopsy. In patient 1, no significant change in SP density was detected. The increase in SP counts ap-peared to result from an increase in all types of plaques, including diffuse, neuritic, and amyloid plaques with no recognizable predominance for any of these subtypes (for nomenclature and definition of plaque types, see Dick-inson25). Specifically, neuritic plaques and diffuse plaques were present in approximately equal numbers (50% each type), and this ratio did not vary significantly from bi-opsy to autbi-opsy. No preferential laminar involvement was appreciated in changes of SP densities. When all cases
A
C
B
Figure 1.Gross photographs of selected coronal slices of cerebral hemispheres from patients 1 (A), 4 (B), and 5 (C). In brains of patients 1 and 5, small cavitating lesions are evident at the catheter insertion site (arrows). The brain from patient 4 shows striking ventricular dilatation and white matter shrinkage.
Table 1. Patients’ Clinical Parameters*
Parameters
Patients
1 3 4 5
Family history of AD No Yes No Yes
Age, y
At diagnosis 54 49 52 59
At biopsy 62 53 55 63
At death 71 64 66 72
Follow-up from biopsy to death, y 9 11 11 9
MMSE at biopsy 18 27 27 18
MMSE close to death 0 0 0 0
CDRS at biopsy 1 0.5 0.5 1
were considered together, analysis of variance showed a statistically significant difference between SP counts at biopsy and those at autopsy.
DENSITY OF NFTs
As indicated inFigure 3, NFT counts showed, from bi-opsy to autbi-opsy, a marked, statistically significant in-crease in patients 1 and 5, a mild increment (close to sta-tistical significance, P = .05) in patient 3, and an apparent decrease (not reaching statistical significance) in pa-tient 4. The autopsy NFT densities increased 5.5, 1.6, and 4.7 times in patients 1, 3, and 5, respectively, and de-creased by a factor of 0.7 in patient 3. The inde-creased num-bers of NFTs were attributable to a uniform increase in density throughout all layers, with no apparent prefer-ential laminar involvement. Analysis of variance indi-cated a statistically significant difference between bi-opsy and autbi-opsy NFT counts when all cases were considered together.
TOPOGRAPHY OF SPs AND NFTs AT AUTOPSY Figure 4shows the relative densities of SPs and NFTs in different neocortical regions of 2 patients assessed at autopsy (1 and 5). A remarkable topographic variability in the distribution of these lesions is evident.
IMMUNOSTAINING FOR Ab AMYLOID AND CD68
As previously reported, biopsy tissue displayed varying amounts of amyloid deposition within intraparenchy-mal and leptomeningeal vessel walls.17,18Patient 4, in par-ticular, displayed a severe degree of cerebral amyloid an-giopathy, which was especially prominent in cerebral arteries and arterioles, but marked within capillaries as well (Figure 5, A). Autopsy sections of patient 4 re-vealed amounts of vascular amyloid comparable with those in the biopsy specimen, without apparent changes in ex-tent or pattern of amyloid deposition. The white matter displayed marked thinning and pallor, due to loss of axons and myelin, with concomitant widespread astrogliosis (Figure 5, B). In all other cases, modest amyloid depo-sition was demonstrated in the microvasculature of both biopsy and autopsy sections, with no appreciable changes from biopsy to autopsy.
Similarly, CD68 immunoreactive microglial cells were present in both biopsy and autopsy material in vari-able densities.Table 2shows the results of a semiquan-titative assessment of microglial density in the biopsy and autopsy samples, subjectively graded as low, moderate,
60 40 50 30 20 10 0 1 3 4 5 Patients SPs/mm 2 Biopsy Autopsy
Figure 2.Bar graph illustrating senile plaque (SP) mean counts (SD) at biopsy and autopsy for patients 1, 3, 4, and 5. The t test showed a statistically significant difference between biopsy and autopsy counts for patients 3 ( P,.001), 4 ( P,.001), and 5 ( P,.005). 40 30 20 10 5 15 25 35 0 1 3 4 5 Patients NFT s/mm 2 Biopsy Autopsy
Figure 3.Bar graph illustrating neurofibrillary tangle (NFT) mean counts (SD) at biopsy and autopsy for patients 1, 3, 4, and 5. The t test showed a statistically significant difference between biopsy and autopsy counts for patients 1 ( P,.05) and 5 ( P,.005). P values for patients 3 and 4 are .08 and .05, respectively. 30 20 10 5 15 25 0
Frontal Right Temporal Left Temporal Right Occipital Right Patient 1 Lesions/mm 2 Senile Plaques Neurofibrillary Tangles Senile Plaques Neurofibrillary Tangles 60 40 20 10 30 50 0
Frontal Left Frontal Right Temporal Left Temporal Right Occipital Right Neocortical Regions
Patient 5
Lesions/mm
2
or high, in the cortex and subcortical white matter. In general, the density of microglial cells in autopsy mate-rial was approximately similar to that seen in the corre-sponding biopsy material, except in patient 5, where mi-croglial density increased significantly from biopsy to autopsy (Figure 6), in both gray and white matter. Com-paring white matter with gray matter within the same case, we observed that microglial cell densities were consis-tently much higher in the white matter than in the cor-tex, both at biopsy and at autopsy. Microglial cells showed a monotonous and even distribution throughout the white matter, while in the neocortex they were diffusely dis-persed, but with occasional focal clustering (presum-ably around senile plaques). Frontal lobe samples de-rived from the autopsy of 2 neurologically intact subjects showed low microglial densities in both gray and white matter, with only rare microglial cells showing scanty cy-toplasm and short processes. The frontal cortex and white matter of 2 controls with AD had moderately increased microglial densities that were approximately compa-rable with those of the cases in our study. However, mi-croglial cell density in patient 5 was noticeably higher than all other AD cases (Figure 6).
APOE AND PRESENILIN GENOTYPING APOE genotypes could be determined on patients 1 and 3 only. Both these cases had a 3/4 APOE genotype. Also, a blood sample from patient 3 was analyzed by the
Ge-netics Project of the University of Washington Alzhei-mer’s Disease Research Center, Seattle (T. Bird, MD, G. Schellenberg, MD, 1998) and revealed a missense mu-tation in the presenilin-1 gene (R269H).
COMMENT
The present investigation was aimed at studying the pro-gression of AD changes, eg, SPs and NFTs, in 4 patients whose brains were examined at autopsy and who had pre-viously undergone a biopsy procedure 9 to 11 years be-fore death. These patients afforded the rare opportunity to conduct a longitudinal study to help clarify the still ob-scure issue of the temporal evolution of pathological changes in AD. All our patients showed a consistent and marked decline in their cognitive functions throughout the period between biopsy and autopsy, as indicated by their func-tional ability and MMSE scores, which declined from 18 (in patients 1 and 5) and 27 (for patients 3 and 4) to 0 by the time they died. Concomitantly, a marked, statistically significant increment in the density of SPs in the right fron-tal cortex was revealed, with counts at autopsy reaching levels from from 2.5 up to 8.4 times those recorded in the biopsy specimens for 3 of the patients (patients 3, 4, and 5), while they remained unaltered in patient 1. Similarly, autopsy NFT densities showed a marked statistically sig-nificant increase in patients 1, 3, and 5 (1.6-5.5 times those at biopsy); in patient 4, the autopsy NFT counts were lower than in the biopsy but not to a statistically significant de-gree. No apparent correlation was noted between the pres-ence of a family history (in patients 2 and 5) and evolu-tion of Alzheimer changes from biopsy to autopsy. Tis-sue shrinkage due to brain atrophy may have contributed to an apparent increase in NFT and SP densities but not to the extent observed in this study. The effect of catheter insertion seems unlikely to have played a role in produc-ing or acceleratproduc-ing progression of AD changes, but no data are available in the literature to demonstrate that focal trauma may have an effect on SP and NFT development at sites distant from the lesion itself.
Clinicopathologic investigations have suggested that the severity of the intellectual impairment in patients with AD is correlated with the burden of underlying pathological Table 2. Semiquantitative Assessment of Microglial Density
in Biopsy and Autopsy Sections Immunostained for CD68 Patient Procedure Frontal Cortex White Matter
1 Biopsy Low Moderate
Autopsy Low High
3 Biopsy Moderate Moderate
Autopsy Moderate Moderate
4 Biopsy Low Low
Autopsy Low Low
5 Biopsy Low Low
Autopsy High High
A B
A B
C D
E F
G
markers, ie, SPs and NFTS.3,4,6-8If this is true, worsening of memory function in an individual patient should be ac-companied by a concomitant increase in the numbers of SPs and NFTs. Such a view is in good agreement with the results of the present study, which shows that 4 patients with AD displayed a marked progression in the severity of neuropathological changes during the 9 to 11 years be-tween biopsy and autopsy. Two previous studies,9,10 ap-parently similar to ours in design and patients, reached different conclusions, as no significant progression of AD changes was seen in patients who showed progressive men-tal decline in the period from biopsy to autopsy. This dis-crepancy can probably be explained by examining in more detail the individual patients investigated in those stud-ies. In the investigation by Mann et al,9the study group consisted of 5 patients, of whom 2 had frontal and 3 tem-poral biopsies. Available data indicate that there are marked interindividual differences in the regional brain distribu-tion of AD pathology,6,8as well as in the apparent pro-gression of lesions in the frontal vs temporal lobes. It seems appropriate, therefore, to compare our patients (whose pathological analysis was carried out in the frontal cor-tex) exclusively with the subjects in whom biopsy and au-topsy data were obtained from the frontal cortex. In these patients, the time interval between biopsy and autopsy was only 3 years, as compared with 9 to 11 years in our cases. Similarly, the study by Bennett et al10examined SP and NFT densities in the frontal cortex of patients who were followed up for only 21 to 47 months from biopsy to au-topsy. The difference in length of follow-up seems the most probable reason for the discrepant results between our study and those of Mann and colleagues and Bennett et al. In addition, the relatively short period from biopsy to death in the patients of the previous studies suggests that they underwent biopsy at more advanced stages of disease com-pared with our patients. It is plausible that in the most ad-vanced stages of AD a “ceiling effect” may occur, when intellectual deterioration begins to gradually decelerate and the underlying pathological changes also cease to progress. The patient in the study by Bennett and colleagues who was followed up for the longest time (47 months) mani-fested a statistically significant increase in the density of NFTs. Thus, the groups of patients presented by the other investigators may have failed to show any progression of pathological changes possibly because they were exam-ined in the “end stage” of the disease, in which no further numerical increment of SP and NFT densities become ap-parent. Discrepancies between degree of neurologic im-pairment and counts of associated SPs and NFTs may also have other explanations.
Pathological alterations other than SPs and NFTs have been shown to develop in AD brains and parallel the se-verity of the clinical picture. At least 3 additional patho-physiologic processes have been proposed to play a key role in the pathogenesis of AD: (1) Loss of synapses in AD fron-tal cortex has been well documented by synaptophysin im-munoreactivity and ultrastructural analysis and shown to be correlated with the degree of cognitive deficit.26-28(2) Inflammatory mechanisms and microglial cell activation may also participate in the pathophysiology of AD and pos-sibly exert detrimental effects clinically.29,30Microglial cell density evaluated in our samples by CD68
immunohisto-chemistry shows that activation of microglial cells varies significantly from subject to subject and may also mani-fest a considerable increase with time (such as in patient 5, increasing from “low” levels at biopsy to “high” levels at autopsy). Surprisingly, microglial cell density in the white matter was remarkably higher than that in the neocortex in all cases, suggesting that inflammatory responses in-volving the white matter may be more prominent than those in the gray matter and obviously not directly related to the development of the pathological features considered to be most characteristic of AD. (3) Cerebral amyloid angiopa-thy (CAA) is an additional, fundamental pathological pro-cess of AD, which may contribute to brain damage by mechanisms not yet entirely clarified, but possibly includ-ing ischemia.31With respect to degree of CAA, the pre-sent cases displayed a remarkable heterogeneity, with pa-tient 4 showing the most severe and widespread vascular deposition of amyloid and also the most striking degree of brain atrophy (especially white matter) by the time of death. Previous investigations performed on the same subjects32 showed that the levels of amyloid precursor protein in the cerebrospinal fluid were negatively correlated with the bur-den of amyloid deposition within brain, being 20 times lower in patient 4 (with the most severe CAA) than in the re-maining 3 patients. Other investigators have reported simi-lar findings.33These data suggest that levels of soluble Ab amyloid and amyloid precursor protein are inversely cor-related with amyloid burden in the cerebral vessels and may be used as a useful marker for diagnostic purposes and as a measurement of clinical progression of AD.33
Alzheimer disease pathological markers develop in vul-nerable brain regions in an uneven manner and at a vari-able rate. Indeed, cross-sectional studies indicate that the spreading of pathological alterations in AD does not appear in different brain regions at the same time but tends to be-gin in certain areas (namely, entorhinal cortex and hippo-campal formation), subsequently spreading to other areas as the disease advances.6Obviously, counting SPs and NFTs in a small sample of frontal cortex may not be sufficient to account for the progression of cognitive deterioration.
Finally, progression of cognitive impairment may not be exclusively correlated with increasing SP and NFT densities or with numerical changes of other variables but may also depend on the specific brain regions af-fected. Involvement of subcortical nuclei crucial to memory functions, such as cholinergic forebrain nu-clei, contributes importantly to cognitive impairment.34 These nonplaque or tangle changes may help to account for the absence of any increase of SP density in patient 1 and of NFT density in patient 4 of our study, despite in-creasing cognitive impairment.
forma-tion, microglial cell activation and CAA may be addi-tional pathogenetic factors whose role in the progres-sion of AD neurologic impairment is important but still not clearly defined. It is also apparent that the relation-ship between progression of pathological changes and clinical deterioration is rather loose, possibly because nei-ther SP nor NFTs represent the brain fundamental mor-phologic change underlying AD. Based on the available data, therefore, it is plausible that AD may result from a mosaic of pathological changes that vary from patient to patient in intensity and distribution, and whose variabil-ity may account, ultimately, for the dissimilarities in clini-cal picture seen among patients with this disease. Accepted for publication September 10, 1998.
This work was supported by US Public Health Ser-vice, Washington, DC, grants P01 NS 12435, P30 AG 10123, and the Sidell-Kagan Foundation, Los Angeles, Calif. The original Bethanechol Trial was supported by the John Doug-las French Foundation for Alzheimer’s Research and the Vet-erans Affairs Medical Center, West Los Angeles.
The views expressed do not necessarily reflect the views of the Veterans Affairs or the US government.
Carol Appleton prepared the illustrations; Zhen Zhen Wang, MD, assisted with immunohistochemical study of CAA; and Lynn A. Fairbanks, PhD, assisted with the sta-tistical analysis. APOE genotyping was carried out by the Alzheimer’s Disease Center Genetics Core of University of California, Los Angeles.
This study would not have been possible without the extraordinary commitment of the Bethanechol Trial patients and, especially, their wives and families.
Reprints and corresponding author: Pier Luigi Di Pa-tre, MD, Department of Pathology and Laboratory Medi-cine, University of California, Los Angeles, Medical Cen-ter, CHS 18-170, Los Angeles, CA 90095-1732 (e-mail: [email protected]).
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