A quantitative study of tau pathology in 11 cases of chronic traumatic encephalopathy

AIMS

To quantify tau pathology of chronic traumatic encephalopathy (CTE) and investigate influence of dot-like lesions (DL), brain region, comorbidity and sporting career length.

METHODS

Densities of neurofibrillary tangles (NFT), astrocytic tangles (AT), DL, oligodendroglial inclusions (GI), neuropil threads (NT), vacuoles, neurons and enlarged neurons (EN) were measured in tau-immunoreactive sections of upper cortical laminae of frontal and temporal lobes, hippocampus (HC), amygdala and substantia nigra (SN) in 11 cases of CTE.

RESULTS

DL were a consistent finding in CTE. Densities of NFT, NT and DL were greatest in sectors CA1 and CA2 of the HC. Densities of AT were lower than NFT, small numbers of GI were recorded in temporal lobe and low densities of vacuoles and EN were consistently present. β-Amyloid-containing neuritic plaques (NP) also occurred at low density. Densities of NFT, NT, DL and AT were greater in sulci than gyri, while vacuole density was greater in gyri. Principal components analysis (PCA) suggested that sporting career length and densities of NFT in entorhinal cortex, NT in CA2 and SN and vacuolation in the DG were significant sources of variation among cases.

CONCLUSION

DL are frequent in CTE suggesting affinity with argyrophilic grain disease (AGD) and Parkinson's disease dementia (PD-Dem). Densities of AT in all regions and NT/DL in sectors CA2/4 were consistent features of CTE. The 11 cases are neuropathologically heterogeneous which may result from genetic diversity, and variation in anatomical pathways subjected to trauma.

APOE, vascular pathology, and the AD brain

OBJECTIVE

To use neuropathologic data to examine the association between APOE genotype and cerebrovascular lesions commonly found in Alzheimer disease (AD), as well as neuritic senile plaque (SP) and neurofibrillary tangle (NFT) burden.

METHODS

The sample comprised brains from 96 men and 3 women who fulfilled NIA-Reagan criteria for intermediate to high likelihood of AD. Region-specific and global measures of gross cerebrovascular disease, arteriolosclerosis, white matter lesions, microinfarcts, amyloid angiopathy, neuritic SP, and NFT burden were compared among those who had at least one APOE-epsilon4 vs those who did not. Pairwise rank-order correlations between measures were calculated. The association between APOE epsilon4 status and measures of vascular and AD pathology, adjusting for age at death, sex, brain weight, and Braak stage, were evaluated.

RESULTS

APOE-epsilon4 was not associated with gross cerebrovascular pathology. Compared to those who were negative, brains from epsilon4 individuals had a greater degree of small vessel arteriolosclerosis (p = 0.04) and perivascular macrophage infiltration (p = 0.06), but not other markers of small vessel disease or white matter myelin loss. Microinfarcts in the deep nuclei were associated with epsilon4 (p = 0.009), whereas cortical and subcortical microinfarcts were not. There was a trend toward association between APOE genotype and amyloid angiopathy (p = 0.08), and epsilon4 was associated with neuritic SP burden, but not NFT.

CONCLUSION

APOE-epsilon4 is associated with small vessel arteriolosclerosis, microinfarcts of the deep nuclei, neuritic senile plaque density, and amyloid angiopathy in patients with autopsy-proven Alzheimer disease (AD). These results suggest a role for epsilon4 in some of the microvascular changes commonly found in AD and are consistent with a potential amyloidogenic role for epsilon4.

Differential circadian rhythm disturbances in men with Alzheimer disease and frontotemporal degeneration

BACKGROUND

Caregiver exhaustion is a frequent consequence of sleep disturbance and rest-activity rhythm disruption that occurs in dementia. This exhaustion is the causal factor most frequently cited by caregivers in making the decision to institutionalize patients with dementia. Recent studies have implicated dysfunction of the circadian pacemaker in the etiology of these disturbances in dementia.

METHODS

We studied the activity and core-body temperature rhythms in a cohort of 38 male patients with a clinical diagnosis of probable Alzheimer disease (AD) approximately 2 years before death. These patients were later given a confirmed diagnosis of AD (n = 23), frontotemporal degeneration (FTD) (n = 9), or diffuse Lewy body disease (DLB) with mixed AD or FTD pathologies (n = 6) after autopsy and neuropathological examination. Physiological rhythms of patients with AD and FTD were then compared with a group of normal, elderly men (n = 8) from the community.

RESULTS

Alzheimer patients showed increased nocturnal activity and a significant phase-delay in their rhythms of core-body temperature and activity compared with patients with FTD and controls. The activity rhythm of FTD patients was highly fragmented and phase-advanced in comparison with controls and apparently uncoupled from the rhythm of core-body temperature.

CONCLUSIONS

Patients with AD and patients with FTD show different disturbances in their rhythms of activity and temperature compared with each other and with normal elderly patients.

MPTP induces alpha-synuclein aggregation in the substantia nigra of baboons

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity reproduces many of the features of Parkinson's disease (PD). alpha-Synuclein has been identified as a prominent component of the Lewy body (LB), the pathological hallmark of PD. MPTP-treated primates have been reported to develop intraneuronal inclusions but not true Lewy bodies. We administered MPTP to baboons and used a monoclonal alpha-synuclein antibody to define the relationship between neuronal degeneration and alpha-synuclein immunoreactivity in the substantia nigra. MPTP-induced neuronal degeneration was associated with the redistribution of alpha-synuclein from its normal synaptic location to aggregates in degenerating neuronal cell bodies. alpha-Synuclein aggregation induced by MPTP models the early stages of Lewy body formation and may be a fundamental step in the evolution of neuronal degeneration in PD.

Enhanced inhibition of free radical-induced deoxyribose breakdown by Alzheimer brain homogenates

The ability of homogenates from Alzheimer and control brains to inhibit formation of thiobarbituric acid reactive products (TBAR) induced by free radicals was compared. The assay for TBAR was modified by adding 1% sodium dodecyl sulfate (SDS) to prevent chromogen adsorption by biological matrices, and by extending the incubation time. The inhibitory activities required smaller equivalents of Alzheimer brain homogenates than control homogenates. Similar inhibitory activities were seen in homogenates from amygdala, temporal cortex and cerebellum. The inhibitory activities were similar in brain homogenates from individuals with different apolipoprotein E status. These results indicate that Alzheimer brain tissue has either increased content of free radical scavengers or is more sensitive to free radical attack than control brains.

Near-infrared fluorescence spectroscopy detects Alzheimer's disease in vitro

The purpose of this study was to investigate whether near-infrared (NIR) fluorescence spectroscopy could be used to detect Alzheimer's disease (AD) by brain tissue autofluorescence. Unfixed temporal cortex specimens from AD cases and age-matched, non-AD controls were frozen at autopsy and then thawed just prior to spectral measurement. Spectra of intrinsic tissue fluorescence induced by 647 nm light were recorded from 650 to 850 nm. We used principal component analysis of the tissue spectra from 17 AD cases and 5 non-AD control cases in a calibration study to establish a diagnostic algorithm. Retrospectively applied to the calibration set, the algorithm correctly classified 23 of 24 specimens. In a prospective study of 19 specimens from 5 AD brains and 2 non-AD control brains, 3 of the 4 control specimens and all AD specimens were correctly diagnosed. Both the excitation light used and the measured brain tissue autofluorescence are at NIR wavelengths that can propagate through skull and overlying tissue. Therefore, our results demonstrate an optical spectroscopic technique that carries direct molecular level information about disease. This is the first step toward a clinical tool that has the potential to be applied to the noninvasive diagnosis of AD in living patients.

Brain banking: basic science methods

The fundamental objectives of a brain bank are to document precisely the gross anatomical and histological findings, to establish accurate neuropathological diagnoses using well-defined criteria and standardized dissection techniques, and to serve as a source of fresh, fixed, and deep-frozen brain tissue. The brain tissue is optimally prepared and stored to provide high-quality research material that is suitable for a wide variety of investigations. A computerized database is used to classify all clinical and pathological diagnoses, neuropathological data, cause of death, postmortem interval, associated chronic diseases, and storage conditions of the tissue. Tissue availability and distribution is monitored and quality assurance is provided regarding tissue acquisition, processing, storage, and diagnosis. These functions facilitate clinicopathological correlative studies, neurochemical, molecular biological, immunohistochemical, quantitative and in vitro studies. Furthermore, the use of standardized tissue methods promotes multicenter collaborations.

The neurotoxicity of amyloid beta protein in aged primates

Amyloid beta protein deposition is a universal feature of Alzheimer's disease brain. To investigate the effects of amyloid beta protein in aged primates, intracerebral microinjections of solubilized amyloid beta (A beta (1-40)) and control peptides were made into the frontal cortex of 7 primates under stereotactic guidance. Control injections consisted of vehicle alone, a 37 amino acid non toxic peptide (A37), scrambled peptide (CA4), and reverse peptide (A beta (40-1)). Amyloid beta peptide produced dose-dependent cortical lesions that were significantly larger than those produced by vehicle or by isomolar control peptides (3.28 and 2.20 fold larger respectively) (p = < 0.005). In 5 aged primates, the cortex surrounding the amyloid beta lesions contained argyrophilic, thioflavine S fluorescent, Alz 50 and ubiquitin immunoreactive neurons and perikarya. The number of Alz 50 immunoreactive neurons surrounding the amyloid beta injections was significantly greater (mean 127 +/- 39) than the number found surrounding reverse peptide injections (mean 20 +/- 13) and other control peptides (mean 0.8 +/- 0.3) (p < 0.05). Neuronal and neuritic alterations were not found adjacent to the amyloid beta peptide lesions in young monkeys and control injections produced insignificant Alz 50 neuronal positivity. These findings suggest that amyloid beta peptide is neurotoxic in primate brain and that the cytoskeletal response to amyloid beta protein is specific and age-related.

Allele epsilon 4 of apolipoprotein E shows a dose effect on age at onset of Pick disease

Pick disease is a rare progressive dementing illness characterized by severe atrophy of the frontal and temporal lobes. Clinically, Pick disease may be difficult to distinguish from Alzheimer disease (AD). The fact that Pick disease is often familial, and the evidence suggesting that the epsilon 4 allele of apolipoprotein E (ApoE) is a risk factor for AD and possibly other dementias, prompted us to study ApoE isoforms in Pick disease. ApoE genotypes were evaluated in an autopsy series of 21 AD and 12 Pick cases and compared with published data for a large group of adults participating in the Framingham Study. The distributions of ApoE genotypes in the AD and Pick patients and the controls were significantly different from one another. The frequency of epsilon 4 was 50.0, 20.0, and 13.6% in these respective groups. Linear regression analysis showed that the number of epsilon 4 alleles was inversely related to age at onset of Pick disease (P < 0.03) and accounted for 40% of the variation in age at onset. These results suggest that epsilon 4 may be a susceptibility factor for dementia and not specifically for AD. Experiments using a monoclonal antibody against ApoE suggest that neurons and Pick bodies are immunoreactive with ApoE. The dose effect of the epsilon 4 allele on age at onset of dementias other than AD and the association of ApoE immunoreactivity with neurons and Pick bodies support a broader role for ApoE in the pathogenesis of neuronal degeneration through interactions with the neuronal cytoskeleton.

An improved approach to prepare human brains for research

We describe two protocols for preparing human brains collected for research and diagnosis. In both protocols, one half brain is processed for research and the other for neuropathological evaluation. Clinical, neuropathological and tissue mRNA retention data are used for sample categorization. In protocol 1, coronal, whole hemisphere slices cut at standardized landmarks are frozen with a cooling device at -90 degrees C, which yields discrete anatomical structures. In selected instances, small blocks of brain are frozen at -160 degrees C in liquid nitrogen vapor. Cooling device or liquid nitrogen vapor frozen samples are suitable for in situ hybridization, protein blotting or immunohistochemistry. Morphological freezing artifacts are minimal. In protocol 2, one half brain is frozen en bloc on dry ice; this tissue is suitable for regional evaluation of gene expression or neurochemistry. Morphological freezing artifacts are severe. In both protocols, the other half brain is fixed in formalin prior to sectioning and diagnostic evaluation. The standardized selection of paraffin blocks from each brain allows precise diagnoses to be established, including identification of dangerous infectious processes; moreover, it makes it possible to produce a set of uniformly selected blocks and slides for comparative studies. These protocols lead to standardized tissue preparation for research and reduce variables impairing interpretation and comparison of data.

Marked changes in mitochondrial DNA deletion levels in Alzheimer brains

Levels of the common 4977 nucleotide pair (np) mitochondrial DNA (mtDNA) deletion (mtDNA4977) were quantitated in the cortex, putamen, and cerebellum of patients with Alzheimer disease (AD) and compared to age-matched controls. Although cerebellum deletion levels were comparably low in AD patients and controls of all ages, cortical deletion levels were clearly different. The levels of mtDNA deletions in control brains started low, but rose markedly after age 75, while those of AD patients started high and declined to low levels by age 80. Choosing age 75 to arbitrarily delineate between younger and older subjects, younger patients had 15 times more mtDNA deletions than younger controls, while older patients had one-fifth the deletion level of older controls. Younger AD patients also had fourfold more deletions than older AD patients. These results support the hypothesis that OXPHOS defects resulting from somatic mtDNA mutations may play a role in AD pathophysiology.

Morphometric image analysis of neuropil threads in Alzheimer's disease

Neuropil threads were quantitated in the neuropil (excluding senile plaques) of the superior frontal gyrus of 6 late stage patients with Alzheimer's disease (AD) and 6 age-matched control subjects using tau immunocytochemistry and computerized morphometric image analysis. The mean percent of the area of the neuropil occupied by neuropil threads was 10.6 for AD and 0.19 for controls (p < 1 x 10(-10)). The mean length of neuropil threads in AD was 21.9 mu compared with 19.7 mu for controls (p < 1 x 10(-10)). The mean area of neuropil threads was 25.3 mu 2 for AD and 21.3 mu 2 for controls (p < 1 x 10(-10)). In AD, the threads were most prominent in mid cortex (lamina 2 and 3) and least prominent in the lower cortex (lamina 5 and 6). Neuropil threads appear to lead to severe disorganization of intracortical and corticocortical connectivity and probably play a role in the cognitive failure in AD.

Inter- and intra-rater reliability of the pressure threshold meter in measurement of myofascial trigger point sensitivity

This study was designed to establish the intra-rater and inter-rater reliability of measurements of trigger point sensitivity using a commercially available pressure threshold meter. Fifty healthy adult volunteers (25 men and 25 women, aged 20 to 51 years) underwent repeated pressure threshold readings from two separate trigger point locations in the trapezius muscle, TP2 (left) and TP3 (right) by two independent examiners. Pressure threshold readings, using a 1.0 kg/s application, were done alternately by each experimenter. Measurements from each trigger point were completed 5 minutes apart. Intraclass correlation coefficients (ICC) revealed the inter-rater reliability to be high for both the first (ICC = 0.82) and second trial (ICC = 0.90) of TP2 and for the first (ICC = 0.86) and second trial (ICC = 0.92) of TP3. Intra-rater reliabilities for TP3 (ICC = 0.91) were higher than for TP2 (ICC1 = 0.80; (ICC2 = 0.83). These results show that the pressure threshold meter is highly reliable in measuring trigger point sensitivity, between and within experimenters, and may be useful in the diagnosis and monitoring of treatment of myofascial pain syndrome.

Patterns of neuronal degeneration in the motor cortex of amyotrophic lateral sclerosis patients

We examined patterns of neuronal degeneration in the motor cortex of amyotrophic lateral sclerosis (ALS) patients using traditional cell stains and several histochemical markers including neurofilament, parvalbumin, NADPH-diaphorase, ubiquitin, Alz-50 and tau. Three grades of ALS (mild, moderate, severe) were defined based on the extent of Betz cell depletion. Non-phosphorylated neurofilament immunoreactive cortical pyramidal neurons and non-pyramidal parvalbumin local circuit neurons were significantly depleted in all grades of ALS. In contrast, NADPH-diaphorase neurons and Alz-50-positive neurons were quantitatively preserved despite reduced NADPH-diaphorase cellular staining and dendritic pruning. The density of ubiquitin-positive structures in the middle and deep layers of the motor cortex was increased in all cases. Axonal tau immunoreactivity was not altered. These histochemical results suggest that cortical degeneration in ALS is distinctive from other neurodegenerative diseases affecting cerebral cortex. Unlike Huntington's disease, both pyramidal and local cortical neurons are affected in ALS; unlike Alzheimer's disease, alteration of the neuronal cytoskeleton is not prominent. The unique pattern of neuronal degeneration found in ALS motor cortex is consistent with non-N-methyl-D-aspartate glutamate receptor-mediated cytotoxicity.

In vivo neurotoxicity of beta-amyloid [beta(1-40)] and the beta(25-35) fragment

We examined the histological changes produced by injections of beta-amyloid [beta(1-40)], and control peptides in rat and monkey cerebral cortex. beta(25-35) injections were also studied in rat cortex. Standard immunoperoxidase procedures were used to detect the distribution of tau, MAP2, beta(1-40) and ALZ 50 immunoreactivity. All injections produced localized necrosis at the injection site surrounded by a zone of neuronal loss and gliosis. In rat cortex, lesions produced by solubilized beta(1-40) and beta(25-35) in water were generally larger than those produced by control peptides. Tau and ALZ 50 antibodies labeled neurites and diffusely positive perikarya around beta(1-40) injections, whereas MAP2 staining was reduced, paralleling the distribution of neuronal loss and gliosis. In aged primate cortex, beta(1-40) lesion size was dose dependent. Hyalinized, ALZ 50 positive neurons, and abnormal neurites were prominent around the injection site. Although beta-amyloid is acutely neurotoxic in both rat and monkey cerebral cortex, neuronal degeneration in the primate more closely resembles that found in AD.

Neuritic pathology and dementia in Alzheimer's disease

Previous studies of Alzheimer's disease (AD) have correlated the severity of dementia with either the number of senile plaques or neurofibrillary tangles. We used antibodies raised against amyloid beta/A4 protein of senile plaque cores and tau protein as well as thioflavine S and the Campbell-Switzer modification of the Hicks silver method to examine the hippocampal formation and five neocortical regions from 22 nondemented elderly control subjects and 34 demented patients with cerebral senile plaques and neurofibrillary tangles, without complicating disease processes. Ten control subjects (46%) had no beta/A4 protein deposition. Twelve control subjects (54%) had widespread beta/A4 protein deposition but no neocortical neuritic pathology. Of the 34 patients with AD-type changes, 27 (79%) had widespread senile plaques and neurofibrillary tangles, while 7 (21%) had neocortical senile plaques with few neurofibrillary tangles. All demented patients had widespread beta/A4 protein deposition and neocortical tau-immunoreactive, Hicks silver-positive dystrophic neurites. The neurites were found both free in the neuropil as well as surrounding senile plaques. Quantitative analysis showed that dystrophic neurites were significantly increased in patients with AD compared with control subjects and the number of dystrophic neurites and neurofibrillary tangles correlated with the clinical severity of dementia. Widespread cerebral beta/A4 protein deposition may be necessary but by itself is insufficient for the development of dementia in AD.

Peduncular hallucinosis associated with isolated infarction of the substantia nigra pars reticulata

We report the clinicopathological study of an 83-year-old man who abruptly developed complex visual hallucinations, disordered sleep, and mild cognitive impairment that persisted until his death 6 months later. Postmortem neuropathological examination including serial sections through the diencephalon, midbrain, and pons disclosed isolated bilateral infarcts confined to the medial substantia nigra pars reticulata. The findings suggest that destruction of the pars reticulata may be the essential feature to the development of peduncular hallucinosis.

Paraneoplastic limbic encephalitis: neuropsychiatric presentation

Limbic encephalitis as a distinct clinicopathological entity is becoming increasingly familiar to neurologists. However, despite its classical clinical presentation of mental status changes and behavioral abnormalities, the disorder is not well known in the psychiatric literature and premortem diagnosis is rare. We recently participated in the care of a patient who spent two months on a psychiatric service and in whom a medical disorder was consistently suspected but not confirmed until autopsy revealed paraneoplastic limbic encephalitis and two primary systemic malignancies. A detailed neuropsychiatric description of this clinical entity is provided from presentation to autopsy with review of the literature.

Hippocampal neurons predisposed to neurofibrillary tangle formation are enriched in type II calcium/calmodulin-dependent protein kinase

The microtubule-associated phosphoprotein, tau, is an integral component of paired helical filaments in Alzheimer neurofibrillary tangles (NFT). The mechanism of NFT formation is unknown but aberrant phosphorylation of tau may be contributory. Calcium/calmodulin-dependent protein kinase type II (CaM kinase II), the most abundant kinase in the brain, phosphorylates tau in vitro. We found CaM kinase II immunoreactivity concentrated in human hippocampal pyramidal neurons of CA1 and the subiculum. In Alzheimer's disease (AD) staining intensity of CA1 and subicular neurons is strikingly increased despite NFT formation and neuronal depletion. Enhanced CaM kinase II activity, possibly a result of deafferentation, may contribute to phosphorylation of tau protein leading to NFT deposition and neuronal death in AD.

Microtubular reorganization and dendritic growth response in Alzheimer's disease

Cytoskeletal disruption is a key pathological feature of Alzheimer's disease (AD). We used refined immunocytochemical techniques to define the range of abnormalities affecting the microtubule system in AD hippocampus. Minimal tau and tubulin immunoreactivity was granular and accumulated in otherwise normal neuronal perikarya. As tau-reactive neurofibrillary tangles formed, granular tau and tubulin staining diminished, and ubiquitin reactivity developed. In regions of high neurofibrillary tangle density, microtubule-associated protein 2 (MAP2) histochemical features of remaining nontangled neurons included apical dendritic degeneration with proliferation of basal dendrites. In addition to perisomatic dendritic proliferation, there was massive sprouting of tau-immunoreactive distal dystrophic neurites. Sprouting proximal dendrites and dystrophic neurites often demonstrated growth-cone-like lamellipodia and filopodia. Degeneration of the perisomatic proliferating dendrites was characterized by the accumulation of fibrillar tau immunoreactivity. The colocalization of MAP2 and tau in growth structures recapitulated their codistribution in developing neurites. The data suggest that extensive plasticity and growth response occur in tandem with neuronal degeneration in AD, and that reorganization of the cytoskeletal microtubule system may underlie these proliferative changes.

Embolism of cerebral tissue to lungs: report of two cases and review of the literature

Two patients with head injury and pulmonary emboli of brain tissue are described. Both patients developed persistent bleeding with elevations of prothrombin time, partial thromboplastin time, and decreased platelet counts. Postmortem examination identified multiple skull fractures, subdural and subarachnoid blood, cortical tears, and intraparenchymal hemorrhages. Lacerations of dural venous sinuses were documented in each case. Multiple pulmonary arteries contained plugs of cerebral tissue, including fragments of cerebral and cerebellar cortex, and white matter. The literature concerning brain tissue emboli is reviewed. In neonates, three patients who survived longer than 1 hour were found to have evidence of persistent hemorrhage. Among both children and adults, our two cases are the only ones reported with associated clotting abnormalities. Brain tissue embolism in neonates occurs after difficult vaginal deliveries, often in conjunction with the use of forceps. Tears of the tentorium cerebelli or falx cerebri have been documented at postmortem examination in the majority of these cases. By contrast, brain tissue embolism in children and adults occurs in association with severe closed or penetrating head injury. In several cases, as in the two reported here, postmortem examination has demonstrated a large cerebral venous defect as the probable site of entry of brain tissue into the systemic circulation.

Central pontine myelinolysis in severely burned patients: relationship to serum hyperosmolality

The rapid correction or over-correction of hyponatremia is believed by many to be the crucial factor in the causation of central pontine myelinolysis (CPM). Over a 17-year period we found CPM in 10 (7%) of the 139 burn patients examined postmortem but in only 10 (0.28%) of the 3,528 patients in the general autopsy population (p less than 0.001). Each of the burn patients with CPM had suffered a prolonged, nonterminal episode of extreme serum hyperosmolality, whereas most burn patients without CPM had not suffered such an episode. The histologic age of the lesions correlated with the duration of time between the hyperosmolar episode and death. Hypernatremia, hyperglycemia, and azotemia, alone or combined, accounted for the hyperosmolality. No single electrolyte or metabolic derangement was essential, as in at least one burn patient with CPM the serum sodium, glucose, or blood urea nitrogen was normal during the hyperosmolar episode. Hyponatremia was not present in any burn patient with CPM. We conclude that severely burned patients, like alcoholics, are especially susceptible to CPM, and that in burn patients with CPM there is a striking association with serum hyperosmolality. The data also suggest that the rapid correction of hyponatremia exerts its effects by causing an osmotic shift and not because of any specific property of the sodium ion.