Cerebrospinal fluid neurochemistry in the myoclonic subtype of Alzheimer's disease

At the interface of sensory and motor dysfunctions and Alzheimer's disease

Recent evidence indicates that sensory and motor changes may precede the cognitive symptoms of Alzheimer's disease (AD) by several years and may signify increased risk of developing AD. Traditionally, sensory and motor dysfunctions in aging and AD have been studied separately. To ascertain the evidence supporting the relationship between age-related changes in sensory and motor systems and the development of AD and to facilitate communication between several disciplines, the National Institute on Aging held an exploratory workshop titled "Sensory and Motor Dysfunctions in Aging and AD." The scientific sessions of the workshop focused on age-related and neuropathologic changes in the olfactory, visual, auditory, and motor systems, followed by extensive discussion and hypothesis generation related to the possible links among sensory, cognitive, and motor domains in aging and AD. Based on the data presented and discussed at this workshop, it is clear that sensory and motor regions of the central nervous system are affected by AD pathology and that interventions targeting amelioration of sensory-motor deficits in AD may enhance patient function as AD progresses.

Abnormal neurotransmitter metabolite levels in Alzheimer patients with a delirium

BACKGROUND

Delirium is a complex neuropsychiatric syndrome with an acute onset and fluctuating course. Several studies have suggested the presence of disturbed cholinergic, dopaminergic and serotonergic pathways in delirium as well as in Alzheimer's disease. Abnormal concentrations of amino acids and of neurotransmitter metabolites have been found in plasma, platelets and cerebrospinal fluid of AD patients, and in plasma and CSF of patients with a delirium. The aim of this study was to investigate amino acid and neurotransmitter metabolite levels in plasma of AD patients with a concurrent delirium.

METHODS

In a case-control study of patients suffering from Alzheimer's disease (AD) with concurrent delirium, we investigated the contribution of delirium to some biochemical parameters in blood. We compared plasma amino acid and neurotransmitter metabolite levels of 17 delirious AD patients with those of 17 age- and gender-matched non-delirious AD patients and 29 age- and gender-matched controls.

RESULTS

Homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) levels were higher in delirious AD patients than in controls, but only HVA concentrations were higher in delirious AD patients than in non-delirious AD patients.

CONCLUSIONS

Our findings suggest that central dopaminergic and serotonergic turnover are increased in AD patients with delirium and that the high dopaminergic turnover might reflect the consequences of delirium.

Myoclonus and its disorders

This article defines myoclonus, describes the numerous causes of myoclonus, and summarizes various classification schemes. The electrodiagnostic characteristics and pathophysiology of this movement disorder are described. Treatment of the various forms of myoclonus is also discussed.

[Myoclonus in the adult: diagnostic approach]

Myoclonus, defined as shock-like involuntary movement, may be physiological or caused by a very wide variety of hereditary and acquired conditions. Because myoclonus can originate from different disorders and lesions affecting quite varied levels of the central and peripheral nervous systems, it represents from many points of view a diagnostic challenge. Moreover, new entities have been recently individualized, such as cortical tremor, which deserve renewed attention. The aim of this review is to propose a rationale for a diagnostic approach based on clinical and electrophysiological grounds. In this setting, we successively address 1) the clinical features allowing a positive diagnosis of myoclonus; 2) the clinical clues to the etiology; 3) the relevance of the clinical context to the diagnosis; and 4) the contribution of neurophysiology. Differentiating myoclonus from tics, spasm, chorea and dystonia can be difficult, and a careful reappraisal of clinical features allowing precise identification is presented. Moreover, the topographical distribution of myoclonus, the temporal pattern of muscle recruitment, the condition of occurrence and the rhythm of the event, may provide clinical clues relevant to the diagnosis. Myoclonus without associated epilepsy, myoclonus with epilepsy, myoclonus with encephalopathy, parkinsonism and/or dementia represent overlapping clinical categories, although they remain useful for the diagnostic approach. Using electrophysiology (including back-averaging EEG, MEG, SEP, C-reflex studies) to determine the origin of myoclonus may not allow us to focus on the underlying condition. Indeed, in many instances, the myoclonus is cortical in origin, but the pathology is found elsewhere.

Report of three cases of Alzheimer's disease with focal motor symptoms: clinical correlates of neuroimaging findings

We report clinical and neuroimaging findings for three patients suffering from Alzheimer's disease (AD) with focal motor symptoms. These patients initially showed cognitive deficits and subsequently featured myoclonus and awkward movements in the unilateral upper limb while progressing to paresis. Paresis was noted in the unilateral upper limb. All patients held the unilateral arm flexed at the wrist and elbow, closely adducted to the body and the hand fisted and pronated. No signs of cerebellar ataxia, sensory disturbance or long tract signs were observed, nor any of the initial non-cognitive behavioural changes typical of frontotemporal dementia. EEGs of these patients showed marked slowing of basic activity without epileptic discharges. MRIs showed progressive brain atrophy in the contralateral frontoparietal lobes as well as the hippocampal formation. Cases 2 and 3 featured extensive long T2 lesions on MRI. 99mTc-HMPAO-SPECT revealed blood flow hypoperfusion in the corresponding regions. The cerebellum and brain stem showed neither morphological abnormalities nor blood flow hypoperfusion. On the basis of these clinical and neuroimaging observations, the focal motor symptoms were attributed to contralateral frontoparietal cortical atrophy with or without white matter lesion.

Premutation female carriers of fragile X syndrome: a pilot study on brain anatomy and metabolism

OBJECTIVE

It was thought that premutation carriers of fragile X syndrome (FraX) have no neurobiological abnormalities, but there have been no quantitative studies of brain morphometry and metabolism. Thus the authors investigated brain structure and metabolism in premutation carriers of FraX.

METHOD

Eight normal IQ, healthy female permutation FraX carriers aged 39 +/- 9 years (mean +/- SD) and 32 age-sex-handedness-matched controls (39 +/- 10 years) were studied; in vivo brain morphometry was measured using volumetric magnetic resonances imaging, and regional cerebral metabolic rates for glucose were measured using positron emission tomography and (18F)-2-fluoro-2-deoxy-D-glucose.

RESULTS

Compared with controls, FraX premutation carriers had a significant (1) decrease in volume of whole brain, and caudate and thalamic nuclei bilaterally; (2) increase in volume of hippocampus and peripheral CSF bilaterally, and third ventricle; (3) relative hypometabolism of right parietal, temporal, and occipital association areas; (4) bilateral relative hypermetabolism of hippocampus; (5) relative hypermetabolism of left cerebellum; and (6) difference in right-left asymmetry of the Wernicke and Broca language areas.

CONCLUSIONS

Premutation carriers of FraX, as defined by analysis of peripheral lymphocytes, have abnormalities in brain anatomy and metabolism. The biological basis for this is unknown, but most likely it includes tissue heterogeneity for mutation status. The findings may be of relevance to people counseling families with FraX and to understanding other neuropsychiatric disorders which are associated with expansion of triplet repeats and genetic anticipation.

Decreased monoamine metabolites in frontotemporal dementia and Alzheimer's disease

The concentrations of the monoamine metabolites homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (HMPG) in the cerebrospinal fluid (CSF) of patients with clinical frontotemporal dementia (FTD; n = 30), early onset Alzheimer's disease (EAD; n = 33), late onset Alzheimer's disease (LAD, n = 27) and normal controls (n = 31) were determined using HPLC. ANCOVA showed no significant effect of neuroleptic medication, extrapyramidal signs, myoclonia or gender on the CSF levels of the monoamine metabolites. Homovanillic acid was significantly reduced in all diagnostic groups (FTD, p = 0.0002; EAD, p = 0.016; LAD, p = 0.013). 5-Hydroxyindoleacetic acid was significantly reduced in EAD (p = 0.013) and in LAD (p = 0.0014), and HMPG was reduced in LAD only (p = 0.020). HMPG was significantly higher in FTD compared to EAD (p = 0.0005) and LAD (p = 0.0003). CSF-5-HIAA was significantly reduced in patients with antidepressant medication (p = 0.006). ANCOVA within the FTD group showed no significant effect of neuroleptic or antidepressant medication, extrapyramidal signs, myoclonia, gender or FTD subtype on the CSF levels of the monoamine metabolites. The results suggest that CSF-HMPG might differentiate FTD from EAD and LAD, but not from normals.

Volumes of medial temporal lobe structures in patients with Alzheimer's disease and mild cognitive impairment (and in healthy controls)

BACKGROUND

The clinical diagnosis of Alzheimer's disease (AD) can be difficult to make in early stages of disease. Structural neuroimaging offers a potential tool in the clinical diagnosis of AD with mild cognitive impairment. Postmortem studies indicate that early neuropathology in AD occurs in medial temporal lobe limbic structures. Magnetic resonance imaging (MRI) studies that assessed these volumes in mildly impaired AD patients remain inconclusive.

METHODS

Using MRI, we measured volumes of left and right hippocampus, amygdala, and anterior and posterior parahippocampal gyrus (PHG) in 13 AD patients with mild cognitive impairment, defined as > or = 20 on the Mini-Mental State Exam, and in 21 healthy age- and sex-matched controls.

RESULTS

The AD patients had smaller medial temporal lobe volumes, except for the right anterior PHG. Discriminant function analysis using MRI volumes produced 94% correct group classification.

CONCLUSIONS

These results show that in mildly impaired AD patients atrophy is present in medial temporal lobe structures; that MRI volumes of the anterior PHG, which contains entorhinal cortex, are reduced, but the amygdala and hippocampal volumes show greater reduction; and that discriminant function analysis using all volumes as predictors can correctly classify a high proportion of individuals.

A PET study of Turner's syndrome: effects of sex steroids and the X chromosome on brain

Women with Turner's syndrome (TS) allow us to study the neurobiological associates of cognitive and behavioral abnormalities because they lack one/part of one X chromosome, and endogenous estrogen. We studied 13 healthy controls (mean age +/- SD, 28 +/- 6 years) and 16 TS subjects (mean age +/- SD, 26 +/- 6 years). We measured cognitive abilities using neuropsychological tests, and cerebral metabolic rates for glucose with positron emission tomography. Compared to controls, TS subjects had significant absolute hypermetabolism in most brain areas; however, normalized metabolism was significantly lower in TS subjects than controls in the insula and association neocortices bilaterally, and there were significant differences in functional metabolic associations of brain region pairs originating in occipital cortex bilaterally, and within the right hemisphere. There were significant correlations between right-left cognitive and metabolic asymmetries in the TS group. Also, within TS a preliminary analysis demonstrated "X chromosome dosage" effects in language ability and left temporal metabolism, asymmetry of right-left test scores, and parietal metabolism. We hypothesize that within TS: i) generalized brain hypermetabolism reflects global abnormalities in neuron packing; ii) neuronal abnormalities occur in association neocortex that differ in nature or extent from whole brain and are associated with significant differences in normalized metabolism; iii) cognitive deficits are related to brain metabolic abnormalities; and iv) social-behavioral problems may be related to abnormalities of brain metabolism. Moreover, in human brain the X chromosome involved in development of the association neocortices.

Cerebrospinal fluid 5-hydroxyindoleacetic acid and homovanillic acid in the pediatric opsoclonus-myoclonus syndrome

To study the purported role of central monoamine disturbances in the pathophysiology of the opsoclonus-myoclonus syndrome, the serotonin metabolite 5-hydroxyindoleacetic acid and the dopamine metabolite homovanillic acid were measured in cerebrospinal fluid samples from 27 affected children and 47 age- and gender-matched control subjects by high-pressure liquid chromatography with electrochemical detection. 5-Hydroxyindoleacetic acid and homovanillic acid concentrations in the cerebrospinal fluid were approximately 30 to 40% lower in opsoclonus-myoclonus patients compared to control subjects, and the normal inverse correlation between age and monoamine metabolite concentrations in the cerebrospinal fluid of control subjects was not found in opsoclonus-myoclonus patients. Patients with the lowest values were less than 4 years old, and a subgroup had extremely low levels, but differences in older children were not significant. Cerebrospinal fluid levels of 5-hydroxyindoleacetic acid and homovanillic acid were more positively correlated in control subjects than in opsoclonus-myoclonus patients. None of the patients exhibited high levels of monoamine metabolites. Homovanillic acid levels were slightly lower in the cerebrospinal fluid of patients receiving corticotropin or steroids at the time of lumbar puncture. Clinical variables that could be excluded were paraneoplastic etiology, anesthetic for lumbar puncture, syndrome duration, age at onset, gender, response to steroids, length of time until initiation of corticotropin or steroids, presence of seizures, opsoclonus, and functional impairment. These data suggest a disturbance and possible altered ontogeny of serotonin or dopamine neurotransmission in a subpopulation of children with opsoclonus-myoclonus with low cerebrospinal fluid levels of 5-hydroxyindoleacetic acid and homovanillic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Volumetric magnetic resonance imaging in men with dementia of the Alzheimer type: correlations with disease severity

Using magnetic resonance imaging (MRI), we measured the volumes of various brain structures and cerebrospinal fluid (CSF) in 19 men with dementia of the Alzheimer type (DAT) and 18 healthy age-matched control men. The mean (+/- S.D) Mini-Mental State exam score (MMSE) of the DAT men was 16 +/- 7; 9 were mildly (MMSE > 20), 5 moderately (MMSE 10-20), and 5 severely (MMSE < 10) demented. Brain and CSF volumes were normalized as a percent of the traced intracranial volume to control for the relation of volumes of cerebral structures to head size, and analyzed statistically. The whole group of DAT subjects had significantly smaller mean cerebral brain matter and temporal lobe volumes (p < 0.05), and significantly larger mean ventricular and temporal lobe peripheral CSF volumes than did controls. Mean volumes of the subcortical nuclei did not differ significantly between groups, and mean volume of temporal lobe brain matter decreased significantly more than whole brain, suggesting regional loss of brain matter in DAT. Mildly demented DAT patients had significantly smaller mean cerebral brain matter and temporal lobe volumes and significantly larger volumes of lateral ventricles, and of temporal lobe peripheral CSF, than did controls. Neuropsychological measures of disease severity in DAT patients were significantly (p < 0.05) and appropriately correlated to volumes of cerebral brain matter and right lateral ventricle. These results suggest that in DAT: (i) significant brain atrophy is present early in the disease process, (ii) brain atrophy correlates with severity of cognitive impairment, and (iii) there is greater involvement of the telencephalic association system than whole brain, and there is relative sparing of the caudate, lenticular and thalamic nuclei.

Plasma and cerebrospinal fluid neurochemical pattern in Menkes disease

Menkes disease is a neurodegenerative disorder of copper metabolism. Because the enzyme dopamine-beta-hydroxylase requires copper to catalyze the conversion of dopamine to norepinephrine, we reasoned that patients with Menkes disease would have a neurochemical pattern similar to that seen in patients with congenital absence of dopamine-beta-hydroxylase, i.e., high levels of dopamine, the dopamine metabolite dihydroxyphenylacetic acid (DOPAC), and the catecholamine precursor dihydroxyphenylalanine (DOPA), and low levels of norepinephrine and its neuronal metabolite dihydroxyphenylglycol (DHPG). We measured plasma and cerebrospinal fluid (CSF) levels of catechols in 10 patients ranging in age from 9 days to 27 months. In contrast to patients with congenital absence of dopamine-beta-hydroxylase, norepinephrine levels were normal in plasma of 4 Menkes patients and in CSF of all 10 patients. However, the ratios of DOPA:DHPG and DOPAC:DHPG in plasma and CSF of Menkes patients were invariably increased beyond the ranges of control values. These neurochemical findings indicate partial deficiency of dopamine-beta-hydroxylase in Menkes patients, with compensatory increases in catecholamine biosynthesis in sympathetic nerves and in the brain. Increased tyrosine hydroxylation and increased exocytotic release of norepinephrine may be responsible for preservation of plasma and CSF norepinephrine levels in Menkes patients. The abnormal neurochemical pattern, including high ratios of DOPA:DHPG and DOPAC:DHPG, may serve as a biochemical marker for Menkes disease and provide a baseline against which the influence of proposed therapies can be judged.

Changes in acetylcholinesterase and butyrylcholinesterase in Alzheimer's disease resemble embryonic development--a study of molecular forms

The pattern of molecular forms of acetylcholinesterase (AChE, EC 3.1.1.7) and butyrylcholinesterase (BChE, EC 3.1.1.8) separated by density gradient centrifugation was investigated in the brain and cerebrospinal fluid in Alzheimer's disease (AD), in human embryonic brain and in rat brain after experimental cholinergic deafferentation of the cerebral cortex. While a selective loss of the AChE G4 form was a rather constant finding in AD, a small but significant increase of G1 for both AChE and BChE was found in the most severely affected cases. Both in normal human brain and in AD a significant relationship could be established between the AChE G4/G1 ratio in different brain regions and the activity of choline acetyltransferase (ChAT). A similar decrease of the AChE G4 form as observed in AD can be induced in rat by experimental cholinergic deafferentation of the cerebral cortex. The increase in G1 of both AChE and BChE in different brain regions in AD is quantitatively related to the local density of neuritic plaques which are histochemically reactive for both enzymes. In human embryonic brain, a high abundance of G1 and a low G4/G1 ratio for both AChE and BChE was found resembling the pattern observed in AD. Furthermore, both in embryonic brain and in AD AChE shows no substrate inhibition which is a constant feature of the enzyme in the adult human brain. It is, therefore, concluded that the degeneration of the cholinergic cortical afferentation in AD as reflected by a decrease of AChE G4 is accompanied by the process of a neuritic sprouting response involved in plaque formation which is probably associated with the expression of a developmental form of the enzyme.

Neurochemical markers in the cerebrospinal fluid of patients with Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis and normal controls

Several neurotransmitter markers were investigated in the cerebrospinal fluid (CSF) from patients with Alzheimer's disease (AD) (n = 27), Parkinson's disease (PD) (n = 35) and ALS (n = 26) and from control subjects (n = 34) to compare the possible alterations in the biochemical profiles of these different neurodegenerative diseases. The main proportion of the patients represented an early phase of the illness at the time of the diagnosis. Correlations of the degree of dementia and the stage of the disease with CSF measures were evaluated. The CSF levels of somatostatin like-immunoreactivity (SLI) were significantly reduced in AD patients when compared with those of normals and ALS patients. The CSF concentrations of homovanillic acid (HVA) were significantly decreased for PD patients and the decrease focused on the non-demented patients. A trend of decreasing HVA values towards the most advanced stage of Parkinson's disease assessed by Webster's scale was also displayed. The content of 3-methoxy-4-hydroxyphenylglycol (MHPG) in the CSF was higher for ALS patients than for other groups. The lowest 5-hydroxy-indoleacetic acid (5HIAA) levels were observed in the PD group and the lowest acetylcholinesterase (AChE) activities were found in the PD patients with the most severe disease. Changes in CSF measures were too subtle to be beneficial for diagnostic purposes, but adequate for reflecting the different neurochemical profiles of these three degenerative neurological disorders.

Somatostatin in Alzheimer's disease and depression

Somatostatin (somatotropin release-inhibiting factor, SRIF) was originally discovered (1) during the purification of growth hormone-releasing factor from rat hypothalamus and was subsequently isolated and characterized (2) in 1972 from ovine hypothalamus. Since its initial characterization, SRIF has been shown to fulfill criteria for a neurotransmitter and to directly modulate neuronal activity as well as acting as an inhibitory factor regulating endocrine and exocrine secretion. Alterations in cerebrospinal fluid (CSF) concentrations of SRIF have been reported in several diseases exhibiting prominent cognitive dysfunction, including Alzheimer's disease (AD), major depression, Huntington's chorea, multiple sclerosis, schizophrenia and Parkinson's disease, while evidence for regional brain tissue concentration deficits in SRIF are more specific for AD. This mini-review will focus on the studies reporting alterations in CSF and postmortem tissue concentrations of SRIF in AD and depression.

Analysis of monoamines in the cerebrospinal fluid of Chinese patients with Alzheimer's disease

We have established HPLC assay conditions that could measure the levels of 14 monoamines and their metabolites simultaneously. Monoamine levels in cerebrospinal fluids of 12 Chinese patients with Alzheimer's disease were compared with those in samples from patients with benign prostate hyperplasia. Of the 14 monoamines and metabolites, only three were found to be present in all samples. Although the levels of 5-hydroxy-3-indoleacetic acid (HIAA) and homovanillic acid (HVA) in cerebrospinal fluid of patients with Alzheimer's disease were lower, and the levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) higher, as compared to control patients, no significant differences were found between these two groups.

Cerebrospinal fluid markers of Alzheimer's disease

OBJECTIVE

To review studies on cerebrospinal fluid (CSF) in patients with Alzheimer's disease (AD) in order to answer the question whether CSF contains a specific marker which can be used to support a clinical diagnosis of AD.

DATA SOURCES

Studies identified through an English-language literature search using MEDLINE (1966 to 1990) and a review of bibliographies of relevant articles.

STUDY SELECTION

All studies on CSF in AD patients were selected. Double publications on the same original data were not included. Otherwise, no particular selection was made.

DATA EXTRACTION

The diagnostic utility of more than 60 substances, including CSF measures related to classical neurotransmitters, (neuro)peptides, proteins, amino acids, purines, trace elements, and constituents of senile plaques and neurofibrillary tangles, is evaluated. Clinical epidemiological criteria for deciding on the usefulness of new diagnostic methods are emphasized in this analysis.

DATA SYNTHESIS

Concentrations of some CSF constituents are consistently found to be significantly changed in AD. However, overlap with data of control populations and methodological shortcomings in study design, limit the diagnostic value of all CSF measurements reviewed.

CONCLUSIONS

None of the CSF constituents studied so far can be used in support of the diagnosis of AD. However, increased knowledge concerning macromolecular abnormalities in amyloid containing plaques and neurofibrillary tangles makes the outlook for a diagnostic test for AD on CSF promising.

Molecular biology and transgenetics of prion diseases

Considerable progress has been made deciphering the role of an abnormal isoform of the prion protein (PrP) in scrapie of animals and Gerstmann-Sträussler syndrome (GSS) of humans. Some transgenic (Tg) mouse (Mo) lines that carry and express a Syrian hamster (Ha) PrP gene developed scrapie 75 d after inoculation with Ha prions; non-Tg mice failed to show symptoms after greater than 500 d. Brains of these infected Tg(HaPrP) mice featured protease-resistant HaPrPSc, amyloid plaques characteristic for Ha scrapie, and 10(9) ID50 units of Ha-specific prions upon bioassay. Studies on Syrian, Armenian, and Chinese hamsters suggest that the domain of the PrP molecule between codons 100 and 120 controls both the length of the incubation time and the deposition of PrP in amyloid plaques. Ataxic GSS in families shows genetic linkage to a mutation in the PrP gene, leading to the substitution of Leu for Pro at codon 102. Discovery of a point mutation in the Prp gene from humans with GSS established that GSS is unique among human diseases--it is both genetic and infectious. These results have revised thinking about sporadic Creutzfeldt-Jakob disease, suggesting it may arise from a somatic mutation. These findings combined with those from many other studies assert that PrPSc is a component of the transmissible particle, and the PrP amino acid sequence controls the neuropathology and species specificity of prion infectivity. The precise mechanism of PrPSc formation remains to be established. Attempts to demonstrate a scrapie-specific nucleic acid within highly purified preparations of prions have been unrewarding to date. Whether transmissible prions are composed only of PrPSc molecules or do they also contain a second component such as small polynucleotide remains uncertain.

Laminar distribution of neuron degeneration in posterior cingulate cortex in Alzheimer's disease

The laminar distribution of neuron losses in posterior cingulate cortex were evaluated in 25 clinically and neuropathologically diagnosed cases of dementia of the Alzheimer type (DAT). The layer of maximal neuron loss in area 23a for each DAT case was determined by comparison with mean neuron densities for each layer of 17 neurologically intact control cases. The DAT cases were separated into five classes: class 1, 12% of all DAT cases, no or less than 40% neuron loss in any layer; class 2, 24%, maximal neuron losses in layers II or III; class 3, 28%, losses mainly in layer IV; class 4, 12%, losses mainly in layers V or VI; class 5, 24%, severe losses in all layers. An analysis of large and small neurons showed that in class 2 there was an equal loss of both in layer IIIa--b, in class 3 mostly small neurons were lost in layer IV, in class 4 mostly large neurons were lost in layers III, IV and V, while in class 5 there was no selectivity. The age of disease onset and length of the disease were the same for all classes, although classes 4 and 5 tended to have an earlier onset. No measures of thioflavin S-stained neuritic plaque (NP) or neurofibrillary tangle (NFT) density discriminated among these classes. In 64% of all DAT cases there was a progressive shift in NFT from ventral area 30 where most were in layer II to areas 23a--b where there was a balance between those in superficial and deep layers to dorsal area 23c where most were in layers V and VI.(ABSTRACT TRUNCATED AT 250 WORDS)

Genetic linkage studies suggest that Alzheimer's disease is not a single homogeneous disorder

Alzheimer's disease, a fatal neurodegenerative disorder of unknown aetiology, is usually considered to be a single disorder because of the general uniformity of the disease phenotype. Two recent genetic linkage studies revealed co-segregation of familial Alzheimer disease with the D21S1/S11 and D21S16 loci on chromosome 21. But two other studies, one of predominantly multiplex kindreds with a late age-of-onset, the other of a cadre of kindreds with a unique Volga German ethnic origin, found absence of linkage at least to D21S1/S11. So far it has not been possible to discern whether these conflicting reports reflect aetiological heterogeneity, differences in methods of pedigree selection, effects of confounding variables in the analysis (for example, diagnostic errors, assortative matings), or true non-replication. To resolve this issue, we have now examined the inheritance of five polymorphic DNA markers from the proximal long arm of chromosome 21 in a large unselected series of pedigrees with familial Alzheimer's disease. Our data suggest that Alzheimer's disease is not a single entity, but rather results from genetic defects on chromosome 21 and from other genetic or nongenetic factors.