Predicting amyloid status in corticobasal syndrome using modified clinical criteria, magnetic resonance imaging and fluorodeoxyglucose positron emission tomography

Introduction

Group comparisons demonstrate greater visuospatial and memory deficits and temporoparietal-predominant degeneration on neuroimaging in patients with corticobasal syndrome (CBS) found to have Alzheimer’s disease (AD) pathology versus those with underlying frontotemporal lobar degeneration (FTLD). The value of these features in predicting underlying AD pathology in individual patients is unknown. The goal of this study is to evaluate the utility of modified clinical criteria and visual interpretations of magnetic resonance imaging (MRI) and fluorodeoxyglucose positron emission tomography (FDG-PET) for predicting amyloid deposition (as a surrogate of Alzheimer’s disease neuropathology) in patients presenting with CBS.

Methods

In total, 25 patients meeting CBS core criteria underwent amyloid (Pittsburgh compound B; PIB) PET scans. Clinical records, MRI, and FDG scans were reviewed blinded to PIB results. Modified clinical criteria were used to classify CBS patients as temporoparietal variant CBS (tpvCBS) or frontal variant CBS (fvCBS). MRI and FDG-PET were classified based on the predominant atrophy/hypometabolism pattern (frontal or temporoparietal).

Results

A total of 9 out of 13 patients classified as tpvCBS were PIB+, compared to 2out of 12 patients classified as fvCBS (P < 0.01, sensitivity 82%, specificity 71% for PIB+ status). Visual MRI reads had 73% sensitivity and 46% specificity for PIB+ status with moderate intra-rater reliability (Cohen’s kappa = 0.42). Visual FDG reads had higher sensitivity (91%) for PIB+ status with perfect intra-rater reliability (kappa = 1.00), though specificity was low (50%). PIB results were confirmed in all 8 patients with available histopathology (3 PIB+ with confirmed AD, 5 PIB- with FTLD).

Conclusions

Splitting CBS patients into frontal or temporoparietal clinical variants can help predict the likelihood of underlying AD, but criteria require further refinement. Temporoparietal-predominant neuroimaging patterns are sensitive but not specific for AD.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-014-0093-y) contains supplementary material, which is available to authorized users.

Mammalian target of rapamycin pathway mutations cause hemimegalencephaly and focal cortical dysplasia

Focal malformations of cortical development, including focal cortical dysplasia (FCD) and hemimegalencephaly (HME), are important causes of intractable childhood epilepsy. Using targeted and exome sequencing on DNA from resected brain samples and nonbrain samples from 53 patients with FCD or HME, we identified pathogenic germline and mosaic mutations in multiple PI3K/AKT pathway genes in 9 patients, and a likely pathogenic variant in 1 additional patient. Our data confirm the association of DEPDC5 with sporadic FCD but also implicate this gene for the first time in HME. Our findings suggest that modulation of the mammalian target of rapamycin pathway may hold promise for malformation-associated epilepsy.

PARK10 is a major locus for sporadic neuropathologically confirmed Parkinson disease

OBJECTIVE

To minimize pathologic heterogeneity in genetic studies of Parkinson disease (PD), the Autopsy-Confirmed Parkinson Disease Genetics Consortium conducted a genome-wide association study using both patients with neuropathologically confirmed PD and controls.

METHODS

Four hundred eighty-four cases and 1,145 controls met neuropathologic diagnostic criteria, were genotyped, and then imputed to 3,922,209 variants for genome-wide association study analysis.

RESULTS

A small region on chromosome 1 was strongly associated with PD (rs10788972; p = 6.2 × 10(-8)). The association peak lies within and very close to the maximum linkage peaks of 2 prior positive linkage studies defining the PARK10 locus. We demonstrate that rs10788972 is in strong linkage disequilibrium with rs914722, the single nucleotide polymorphism defining the PARK10 haplotype previously shown to be significantly associated with age at onset in PD. The region containing the PARK10 locus was significantly reduced from 10.6 megabases to 100 kilobases and contains 4 known genes: TCEANC2, TMEM59, miR-4781, and LDLRAD1.

CONCLUSIONS

We confirm the association of a PARK10 haplotype with the risk of developing idiopathic PD. Furthermore, we significantly reduce the size of the PARK10 region. None of the candidate genes in the new PARK10 region have been previously implicated in the biology of PD, suggesting new areas of potential research. This study strongly suggests that reducing pathologic heterogeneity may enhance the application of genetic association studies to PD.

Relationship between hippocampal atrophy and neuropathology markers: a 7T MRI validation study of the EADC-ADNI Harmonized Hippocampal Segmentation Protocol

OBJECTIVE

The pathologic validation of European Alzheimer's Disease Consortium Alzheimer's Disease Neuroimaging Initiative Center Harmonized Hippocampal Segmentation Protocol (HarP).

METHODS

Temporal lobes of nine Alzheimer's disease (AD) and seven cognitively normal subjects were scanned post-mortem at 7 Tesla. Hippocampal volumes were obtained with HarP. Six-micrometer-thick hippocampal slices were stained for amyloid beta (Aβ), tau, and cresyl violet. Hippocampal subfields were manually traced. Neuronal counts, Aβ, and tau burden for each hippocampal subfield were obtained.

RESULTS

We found significant correlations between hippocampal volume and Braak and Braak staging (ρ = -0.75, P = .001), tau (ρ = -0.53, P = .034), Aβ burden (ρ = -0.61, P = .012), and neuronal count (ρ = 0.77, P < .001). Exploratory subfield-wise significant associations were found for Aβ in Cornu Ammonis (CA)1 (ρ = -0.58, P = .019) and subiculum (ρ = -0.75, P = .001), tau in CA2 (ρ = -0.59, P = .016), and CA3 (ρ = -0.5, P = .047), and neuronal count in CA1 (ρ = 0.55, P = .028), CA3 (ρ = 0.65, P = .006), and CA4 (ρ = 0.76, P = .001).

CONCLUSIONS

The observed associations provide pathological confirmation of hippocampal morphometry as a valid biomarker for AD and pathologic validation of HarP.

Molecular disorganization of axons adjacent to human lacunar infarcts

Cerebral microvascular disease predominantly affects brain white matter and deep grey matter, resulting in ischaemic damage that ranges from lacunar infarcts to white matter hyperintensities seen on magnetic resonance imaging. These lesions are common and result in both clinical stroke syndromes and accumulate over time, resulting in cognitive deficits and dementia. Magnetic resonance imaging studies suggest that these lesions progress over time, accumulate adjacent to prior lesions and have a penumbral region susceptible to further injury. The pathological correlates of this adjacent injury in surviving myelinated axons have not been previously defined. In this study, we sought to determine the molecular organization of axons in tissue adjacent to lacunar infarcts and in the regions surrounding microinfarcts, by determining critical elements in axonal function: the morphology and length of node of Ranvier segments and adjacent paranodal segments. We examined post-mortem brain tissue from six patients with lacunar infarcts and tissue from two patients with autosomal dominant retinal vasculopathy and cerebral leukoencephalopathy (previously known as hereditary endotheliopathy with retinopathy, nephropathy and stroke) who accumulate progressive white matter ischaemic lesions in the form of lacunar and microinfarcts. In axons adjacent to lacunar infarcts yet extending up to 150% of the infarct diameter away, both nodal and paranodal length increase by ∼20% and 80%, respectively, reflecting a loss of normal cell-cell adhesion and signalling between axons and oligodendrocytes. Using premorbid magnetic resonance images, brain regions from patients with retinal vasculopathy and cerebral leukoencephalopathy that harboured periventricular white matter hyperintensities were selected and the molecular organization of axons was determined within these regions. As in regions adjacent to lacunar infarcts, nodal and paranodal length in white matter of these patients is increased. Myelin basic protein and neurofilament immunolabelling demonstrates that axons in these adjacent regions have preserved axonal cytoskeleton organization and are generally myelinated. This indicates that the loss of normal axonal microdomain architecture results from disrupted axoglial signalling in white matter adjacent to lacunar and microinfarcts. The loss of the normal molecular organization of nodes and paranodes is associated with axonal degeneration and may lead to impaired conduction velocity across surviving axons after stroke. These findings demonstrate that the degree of white matter injury associated with cerebral microvascular disease extends well beyond what can be identified using imaging techniques and that an improved understanding of the neurobiology in these regions can drive new therapeutic strategies for this disease entity.

Pre-synaptic C-terminal truncated tau is released from cortical synapses in Alzheimer's disease

The microtubule-associated protein tau has primarily been associated with axonal location and function; however, recent work shows tau release from neurons and suggests an important role for tau in synaptic plasticity. In our study, we measured synaptic levels of total tau using synaptosomes prepared from cryopreserved human postmortem Alzheimer's disease (AD) and control samples. Flow cytometry data show that a majority of synaptic terminals are highly immunolabeled with the total tau antibody (HT7) in both AD and control samples. Immunoblots of synaptosomal fractions reveal increases in a 20 kDa tau fragment and in tau dimers in AD synapses, and terminal-specific antibodies show that in many synaptosome samples tau lacks a C-terminus. Flow cytometry experiments to quantify the extent of C-terminal truncation reveal that only 15-25% of synaptosomes are positive for intact C-terminal tau. Potassium-induced depolarization demonstrates release of tau and tau fragments from pre-synaptic terminals, with increased release from AD compared to control samples. This study indicates that tau is normally highly localized to synaptic terminals in cortex where it is well-positioned to affect synaptic plasticity. Tau cleavage may facilitate tau aggregation as well as tau secretion and propagation of tau pathology from the pre-synaptic compartment in AD. Results demonstrate the abundance of tau, mainly C-terminal truncated tau, in synaptic terminals in aged control and in Alzheimer's disease (AD) samples. Tau fragments and dimers/oligomers are prominent in AD synapses. Following depolarization, tau release is potentiated in AD nerve terminals compared to aged controls. We hypothesize (i) endosomal release of the different tau peptides from AD synapses, and (ii) together with phosphorylation, fragmentation of synaptic tau exacerbates tau aggregation, synaptic dysfunction, and the spread of tau pathology in AD. Aβ = amyloid-beta.

In Rasmussen encephalitis, hemichannels associated with microglial activation are linked to cortical pyramidal neuron coupling: a possible mechanism for cellular hyperexcitability

AIMS

Rasmussen encephalitis (RE) is a rare but devastating condition, mainly in children, characterized by sustained brain inflammation, atrophy of one cerebral hemisphere, epilepsy, and progressive cognitive deterioration. The etiology of RE-induced seizures associated with the inflammatory process remains unknown.

METHODS

Cortical tissue samples from children undergoing surgical resections for the treatment of RE (n = 16) and non-RE (n = 12) were compared using electrophysiological, morphological, and immunohistochemical techniques to examine neuronal properties and the relationship with microglial activation using the specific microglia/macrophage calcium-binding protein, IBA1 in conjunction with connexins and pannexin expression.

RESULTS

Compared with non-RE cases, pyramidal neurons from RE cases displayed increased cell capacitance and reduced input resistance. However, neuronal somatic areas were not increased in size. Instead, intracellular injection of biocytin led to increased dye coupling between neurons from RE cases. By Western blot, expression of IBA1 and pannexin was increased while connexin 32 was decreased in RE cases compared with non-RE cases. IBA1 immunostaining overlapped with pannexin and connexin 36 in RE cases.

CONCLUSIONS

In RE, these results support the notion that a possible mechanism for cellular hyperexcitability may be related to increased intercellular coupling from pannexin linked to increased microglial activation. Such findings suggest that a possible antiseizure treatment for RE may involve the use of gap junction blockers.

Aggressive Low-Grade Optic Nerve Glioma in Adults

Primary optic nerve gliomas are most commonly benign pilocytic astrocytomas (World Health Organization [WHO] Grade I) occurring in childhood and following an indolent course. Malignant optic gliomas occur in adulthood and follow an extremely aggressive course, with rapid infiltration of the chiasm, blindness, and death typically within months. A third category of optic glioma, occurring in adulthood, histopathologically benign (WHO Grade I-II) but following an aggressive course, has been rarely reported. The authors describe clinical and histopathologic features of clinically aggressive but histopathologically benign optic nerve gliomas of adulthood. Retrospective review of cases of biopsy-proven optic nerve glioma in the neuro-ophthalmology division of the Jules Stein Eye Institute from 1990 to 2011 was carried out. Cases following an aggressive course were selected for review of clinical, neuroradiologic, and histopathologic features. Three cases were selected for detailed study. Ages ranged from 31 to 45 years. All were initially diagnosed with optic nerve inflammation or benign neoplasm based on clinical and neuroradiologic features, but all suffered neuroradiologic extension and rapid deterioration of vision in the affected eye to no light perception over 3-8 weeks. Optic nerve biopsies were undertaken for the suspicion of malignancy. Features ranged from WHO Grade I (pilocytic astrocytoma, ganglioglioma) in two cases, to WHO Grade II in one case (diffuse astrocytoma, histopathologically benign, but associated with aggressive features such as high p53 [13-21%] and Ki-67 [40%]). The diffuse astrocytoma case subsequently developed extensive intracranial extension suspicious for malignant transformation. These findings indicate that benign optic nerve glioma in adults may be initially misdiagnosed as inflammation, be clinically aggressive, and require excision to prevent further intracranial involvement.

Effects of multiple genetic loci on age at onset in late-onset Alzheimer disease: a genome-wide association study

IMPORTANCE

Because APOE locus variants contribute to risk of late-onset Alzheimer disease (LOAD) and to differences in age at onset (AAO), it is important to know whether other established LOAD risk loci also affect AAO in affected participants.

OBJECTIVES

To investigate the effects of known Alzheimer disease risk loci in modifying AAO and to estimate their cumulative effect on AAO variation using data from genome-wide association studies in the Alzheimer Disease Genetics Consortium.

DESIGN, SETTING, AND PARTICIPANTS

The Alzheimer Disease Genetics Consortium comprises 14 case-control, prospective, and family-based data sets with data on 9162 participants of white race/ethnicity with Alzheimer disease occurring after age 60 years who also had complete AAO information, gathered between 1989 and 2011 at multiple sites by participating studies. Data on genotyped or imputed single-nucleotide polymorphisms most significantly associated with risk at 10 confirmed LOAD loci were examined in linear modeling of AAO, and individual data set results were combined using a random-effects, inverse variance-weighted meta-analysis approach to determine whether they contribute to variation in AAO. Aggregate effects of all risk loci on AAO were examined in a burden analysis using genotype scores weighted by risk effect sizes.

MAIN OUTCOMES AND MEASURES

Age at disease onset abstracted from medical records among participants with LOAD diagnosed per standard criteria.

RESULTS

Analysis confirmed the association of APOE with earlier AAO (P = 3.3 × 10(-96)), with associations in CR1 (rs6701713, P = 7.2 × 10(-4)), BIN1 (rs7561528, P = 4.8 × 10(-4)), and PICALM (rs561655, P = 2.2 × 10(-3)) reaching statistical significance (P < .005). Risk alleles individually reduced AAO by 3 to 6 months. Burden analyses demonstrated that APOE contributes to 3.7% of the variation in AAO (R(2) = 0.256) over baseline (R(2) = 0.221), whereas the other 9 loci together contribute to 2.2% of the variation (R(2) = 0.242).

CONCLUSIONS AND RELEVANCE

We confirmed an association of APOE (OMIM 107741) variants with AAO among affected participants with LOAD and observed novel associations of CR1 (OMIM 120620), BIN1 (OMIM 601248), and PICALM (OMIM 603025) with AAO. In contrast to earlier hypothetical modeling, we show that the combined effects of Alzheimer disease risk variants on AAO are on the scale of, but do not exceed, the APOE effect. While the aggregate effects of risk loci on AAO may be significant, additional genetic contributions to AAO are individually likely to be small.

Emerging concepts in Alzheimer's disease

Alzheimer's disease/senile dementia of the Alzheimer type (AD/SDAT) is the most common neuropathologic substrate of dementia. It is characterized by synapse loss (predominantly within neocortex) as well as deposition of certain distinctive lesions (the result of protein misfolding) throughout the brain. The latter include senile plaques, composed mainly of an amyloid (Aβ) core and a neuritic component; neurofibrillary tangles, composed predominantly of hyperphosphorylated tau; and cerebral amyloid angiopathy, a microangiopathy affecting both cerebral cortical capillaries and arterioles and resulting from Aβ deposition within their walls or (in the case of capillaries) immediately adjacent brain parenchyma. In this article, I discuss the hypothesized role these lesions play in causing cerebral dysfunction, as well as CSF and neuroimaging biomarkers (for dementia) that are especially relevant as immunotherapeutic approaches are being developed to remove Aβ from the brain parenchyma. In addition, I address the role of neuropathology in characterizing the sequelae of new AD/SDAT therapies and helping to validate CSF and neuroimaging biomarkers of disease. Comorbidity of AD/SDAT and various types of cerebrovascular disease is a major theme in dementia research, especially as cognitive impairment develops in the oldest old, who are especially vulnerable to ischemic and hemorrhagic brain lesions.

Clinical predictors of severe cerebral amyloid angiopathy and influence of APOE genotype in persons with pathologically verified Alzheimer disease

IMPORTANCE

Although cerebral amyloid angiopathy (CAA) has important clinical implications, our understanding of it and ability to diagnose it are limited.

OBJECTIVE

To determine pathological correlates and clinical factors identifiable during life that predict the presence of severe CAA in persons with pathologically confirmed Alzheimer disease (AD).

DESIGN, SETTING, AND PARTICIPANTS

We compared demographic and clinical variables at the earliest visit during life at which participants were found to have cognitive impairment and compared pathological variables between persons ultimately found to have no or severe CAA at autopsy using logistic regression. Analyses were repeated separately for carriers and noncarriers of the APOE ε4 allele. Data were obtained from the Uniform Data Set, which comprises longitudinal clinical assessments performed in the Alzheimer's Disease Centers funded by the National Institute on Aging. Participants included 193 persons with AD and severe CAA and 232 persons with AD and no CAA. All participants had cognitive impairment and met National Institute on Aging-Reagan Institute neuropathological criteria for AD.

MAIN OUTCOMES AND MEASURES

Prevalence of demographic characteristics and the APOE ε4 allele and odds ratios (ORs) of clinical variables for the prediction of severe CAA.

RESULTS

Persons with severe CAA compared with those without CAA were more likely to carry an APOE ε4 allele (64.9% vs 42.8%, respectively; P < .001), to be Hispanic (6.8% vs 1.3%, respectively; P = .003), to have had a transient ischemic attack (12.5% vs 6.1%, respectively; OR = 2.1; 95% CI, 1.0-4.4), and to have lower degrees of diffuse amyloid plaque pathology (mean [SD] Consortium to Establish a Registry for Alzheimer's Disease score, 1.2 [0.5] vs 1.4 [0.8], respectively; P = .01). Those with CAA compared with those without CAA more commonly had intracerebral hemorrhage (9.3% vs 3.5%, respectively; P = .01), cortical microinfarcts (20.7% vs 12.9%, respectively; P = .03), and subcortical leukoencephalopathy (20.5% vs 12.1%, respectively; P = .02). Noncarriers of the APOE ε4 allele with severe CAA compared with those without CAA had a higher prevalence of stroke (11.1% vs 3.9%, respectively; OR = 3.8; 95% CI, 1.0-14.6) and hypercholesterolemia (50.0% vs 32.7%, respectively; OR = 2.3; 95% CI, 1.1-4.7).

CONCLUSIONS AND RELEVANCE

Being Hispanic and having had a transient ischemic attack-like episode were predictors of CAA in persons with AD. Less diffuse parenchymal amyloid pathology in persons with severe CAA suggests a difference in β-amyloid trafficking.

Comorbidity in dementia: update of an ongoing autopsy study

OBJECTIVES

To examine systemic and central nervous system (CNS) comorbidities of individuals with dementia evaluated during general autopsy.

DESIGN

Retrospective cohort study.

SETTING

A large tertiary academic medical center in Los Angeles, California.

PARTICIPANTS

Individuals with clinically and neuropathologically diagnosed dementia who received complete autopsies (n = 86) and individuals with dementia who received partial (brain only) autopsies (n = 132).

MEASUREMENTS

Information on cause of death and systemic and CNS comorbidities was obtained from autopsy reports and clinical information as available from the medical records. Findings were tabulated with respect to type of dementia, semiquantitative assessment of the severity of cerebral amyloid angiopathy, semiquantitative assessment of the severity of cerebrovascular disease, and evidence of ischemic damage in the brain.

RESULTS

Of 218 subjects with dementia, 175 (80.3%) had Alzheimer's disease alone or in combination with other lesions that might contribute to cognitive impairment, such as cerebrovascular disease and diffuse Lewy body disease (DLBD), 14 (6.4%) had frontotemporal dementia, and seven (3.2%) had isolated DLBD. The most common cause of death in participants with dementia was pneumonia (n = 57, 66.3%), followed by cardiovascular disease (n = 14, 16.3%). Eighteen subjects (20.9%) had lung disease, and 16 (18.6%) had evidence of an old or recent myocardial infarction. Clinically undiagnosed neoplasms included colonic adenocarcinoma, metastatic pulmonary neuroendocrine carcinoma, meningioma, and Schwannoma.

CONCLUSION

Significant comorbidities were discovered at autopsy in individuals with dementia. Understanding the causes of death and associated comorbidities in individuals with various subtypes of dementia is important in the assessment of end-of-life care in these individuals.

Sympathetic nerve fibers in human cervical and thoracic vagus nerves

BACKGROUND

Vagus nerve stimulation (VNS) therapy has been used for chronic heart failure and is believed to improve imbalance of autonomic control by increasing parasympathetic activity. Although it is known that there is neural communication between the VN and the cervical sympathetic trunk, there are few data regarding the quantity and/or distribution of the sympathetic components within the vagus nerve (VN).

OBJECTIVE

To examine the sympathetic components within the human VN and correlate them with the presence of cardiac and neurologic diseases.

METHODS

We performed immunohistochemistry on 31 human cervical and thoracic VNs (total 104 VNs) from autopsies and reviewed the patients' records. We correlated the quantity of sympathetic nerve fibers within the VNs with cardiovascular and neurologic disease states.

RESULTS

All 104 VNs contain tyrosine hydroxylase (TH)-positive (sympathetic) nerve fibers; the mean TH-positive areas were 5.47% in the right cervical VN, 3.97% in the left cervical VN, 5.11% in the right thoracic VN, and 4.20% in the left thoracic VN. The distribution of TH-positive nerve fibers varied from case to case: central, peripheral, or scattered throughout nerve bundles. No statistically significant differences in nerve morphology were seen between diseases in which VNS is considered effective (depression and chronic heart failure) and other cardiovascular diseases or neurodegenerative disease.

CONCLUSION

Human VNs contain sympathetic nerve fibers. The sympathetic component within the VN could play a role in physiologic effects reported with VNS. The recognition of sympathetic nerve fibers in the VNs may lead to better understanding of the therapeutic mechanisms of VNS.

Neuropathologic correlates of trial-related instruments for Alzheimer's disease

To advance disease-modifying therapies, it is critical to understand the relationship between the neuropathological changes of Alzheimer's Disease (AD) and the clinical measures used in therapeutic trials. We reviewed neuropathologically proven cases of AD from the National Alzheimer's Coordinating Center (NACC) and examined correlations between neuropathological changes and clinical-trial related instruments collected as part of the Uniform Dataset (UDS). We explored the relationships between neurofibrillary tangles, neuritic plaques, and total pathology burden with immediate and delayed recall, Clinical Dementia Rating-Sum of Boxes, Functional Activity Questionnaire, Neuropsychiatric Inventory Questionnaire, and Mini-Mental State Examination scores. 169 patients in NACC database had appropriate neuropathological and clinical data. All instruments correlated highly with neuritic plaques, Braak staging, and total pathology. Correlation coefficients for the relationships were relatively modest, suggesting that the pathologic burden examined accounts for between 13 and 40% of the variance of each of the instruments assessed. We conclude that there is a strong correlation between clinical trial-related measures and neuropathology identified at autopsy in AD. The amount of variance explained by the pathology is limited and other factors, both disease- and measurement-related, contribute to the variability observed in clinical measurements.

Amyloid-β positron emission tomography imaging probes: a critical review

The rapidly rising prevalence and cost of Alzheimer's disease in recent decades has made the imaging of amyloid-β deposits the focus of intense research. Several amyloid imaging probes with purported specificity for amyloid-β plaques are currently at various stages of FDA approval. However, a number of factors appear to preclude these probes from clinical utilization. As the available "amyloid specific" positron emission tomography imaging probes have failed to demonstrate diagnostic value and have shown limited utility for monitoring therapeutic interventions in humans, a debate on their significance has emerged. The aim of this review is to identify and discuss critically the scientific issues contributing to the extensive inconsistencies reported in the literature on their purported in vivo amyloid specificity and potential utilization in patients.

Creutzfeldt-Jakob disease with mixed transcortical aphasia: insights into echolalia

Aphasia is a common manifestation of Creutzfeldt-Jakob disease (CJD), and investigation of the linguistic disorders of CJD patients may provide insights into the neurobiological mechanisms of language and aphasia. We report an autopsy-confirmed case of CJD in which the presenting symptom was change in language abilities. The patient ultimately evidenced mixed transcortical aphasia (MTA) with echolalia. Disruption of frontal-subcortical circuits with environmental dependency accounts for the symptoms in MTA, including intact repetition and echolalia. Observation in this patient and a review of the literature suggest that frontal-subcortical circuit dysfunction may contribute to the syndrome of echolalia. This hypothesis offers an alternative explanation to "isolation" of the speech area as the cause of MTA.

Abstract T P79: Molecular Disorganization of Axons Adjacent to Subcortical Stroke in Hereditary Endotheliopathy With Retinopathy, Nephropathy, and Stroke; an Imaging to Molecular Neuropathology Correlation

White matter stroke secondary to microvascular injury is common yet the molecular changes that accompany ischemic damage to white matter are poorly understood. MRI imaging studies suggest that abnormalities exist within the white matter adjacent to lacunar infarcts and this may lead to infarct progression through a functional disruption of adjacent axons. Hereditary subcortical stroke syndromes provide a unique opportunity to study the molecular mechanisms of cerebral microvascular disease and its effect on white matter. Here, we examined two autopsy cases of hereditary endotheliopathy with retinopathy, nephropathy and stroke (HERNS) syndrome with severe microvascular ischemic disease in the cerebral white matter to determine the molecular organization of myelin and axons within the cerebral white matter adjacent to lacunar infarcts in these patients. MRI imaging was used to identify regions of prior lacunar infarction or FLAIR hyperintensity. Serial paraffin-embedded sections within these regions were immunolabeled for markers of nodes of Ranvier and paranodes as well as neurofilaments and myelin basic protein and compared to normal-appearing white matter and non-diseased controls. Compared to controls, HERNS cases demonstrate lengthening of paranodes and disrupted nodal staining patterns consistent with a loss of normal axon-oligodendrocyte molecular interactions. These abnormalities of axonal microdomains are present beyond the region of infarction suggested by MRI and H&E sections and occur in areas of FLAIR hyperintensity without frank lacunar infarction. These results indicate there is a peri-infarct in white matter stroke marked by molecular disruption of axons surrounding the infarct that may serve as a new therapeutic target for this currently untreatable form of ischemic stroke.

Neuropathologic analysis of hematomas evacuated from patients with spontaneous intracerebral hemorrhage

Spontaneous intracerebral hemorrhage (ICH) is a devastating cause of morbidity and mortality. Intraparenchymal hematomas are often surgically evacuated. This generates fragments of perihematoma brain tissue that may elucidate their etiology. The goal of this study is to analyze the value of these specimens in providing a possible etiology for spontaneous ICH as well as the utility of using immunohistochemical markers to identify amyloid angiopathy. Surgically resected hematomas from 20 individuals with spontaneous ICH were examined with light microscopy. Hemorrhage locations included 11 lobar and nine basal ganglia hemorrhages. Aβ immunohistochemistry and Congo red stains were used to confirm the presence of amyloid angiopathy, when this was suspected. Evidence of cerebral amyloid angiopathy (CAA) was observed in eight of the 20 specimens, each of which came from lobar locations. Immunohistochemistry confirmed CAA in the brain fragments from these eight individuals. Patients with immunohistochemically confirmed CAA were older than patients without CAA, and more likely to have lobar hemorrhages (OR 3.0 and 3.7, respectively). Evidence of CAA was not found in any of the basal ganglia specimens. One specimen showed evidence of CAA-associated angiitis, with formation of a microaneurysm in an inflamed segment of a CAA-affected arteriole, surrounded by acute hemorrhage. In another specimen, Aβ immunohistochemistry showed the presence of senile plaques suggesting concomitant Alzheimer's disease (AD) changes. Surgically evacuated hematomas from patients with spontaneous ICH should be carefully examined, paying special attention to any fragments of included brain parenchyma. These fragments can provide evidence of the etiology of the hemorrhage. Markers such as Aβ 1-40 can help to identify underlying CAA, and should be utilized when microangiopathy is suspected. Given the association of (Aβ) CAA with AD, careful examination of entrapped brain fragments may also provide evidence of AD in a given patient.

Practical utility of amyloid and FDG-PET in an academic dementia center

OBJECTIVE

To evaluate the effect of amyloid imaging on clinical decision making.

METHODS

We conducted a retrospective analysis of 140 cognitively impaired patients (mean age 65.0 years, 46% primary β-amyloid (Aβ) diagnosis, mean Mini-Mental State Examination 22.3) who underwent amyloid (Pittsburgh compound B [PiB]) PET as part of observational research studies and were evaluated clinically before and after the scan. One hundred thirty-four concurrently underwent fluorodeoxyglucose (FDG)-PET. We assessed for changes between the pre- and post-PET clinical diagnosis (from Aβ to non-Aβ diagnosis or vice versa) and Alzheimer disease treatment plan. The association between PiB/FDG results and changes in management was evaluated using χ(2) and multivariate logistic regression. Postmortem diagnosis was available for 24 patients (17%).

RESULTS

Concordance between scan results and baseline diagnosis was high (PiB 84%, FDG 82%). The primary diagnosis changed after PET in 13/140 patients (9%) overall but in 5/13 (38%) patients considered pre-PET diagnostic dilemmas. When examined independently, discordant PiB and discordant FDG were both associated with diagnostic change (unadjusted p < 0.0001). However, when examined together in a multivariate logistic regression, only discordant PiB remained significant (adjusted p = 0.00013). Changes in treatment were associated with discordant PiB in patients with non-Aβ diagnoses (adjusted p = 0.028), while FDG had no effect on therapy. Both PiB (96%) and FDG (91%) showed high agreement with autopsy diagnosis.

CONCLUSIONS

PET had a moderate effect on clinical outcomes. Discordant PiB had a greater effect than discordant FDG, and influence on diagnosis was greater than on treatment. Prospective studies are needed to better characterize the clinical role of amyloid PET.

Pacemaker GABA synaptic activity may contribute to network synchronization in pediatric cortical dysplasia

Spontaneous pacemaker γ-aminobutyric acid (GABA) receptor-mediated synaptic activity (PGA) occurs in a subset of tissue samples from pediatric epilepsy surgery patients. In the present study, based on single-cell electrophysiological recordings from 120 cases, we describe the etiologies, cell types, and primary electrophysiological features of PGA. Cells displaying PGA occurred more frequently in the areas of greatest anatomical abnormality in cases of focal cortical dysplasia (CD), often associated with hemimegalencephaly (HME), and only rarely in non-CD etiologies. PGA was characterized by rhythmic synaptic events (5-10Hz) and was observed in normal-like, dysmorphic cytomegalic, and immature pyramidal neurons. PGA was action potential-dependent, mediated by GABAA receptors, and unaffected by antagonism of glutamate receptors. We propose that PGA is a unique electrophysiological characteristic associated with CD and HME. It could represent an abnormal signal that may contribute to epileptogenesis in malformed postnatal cortex by facilitating pyramidal neuron synchrony.

Cerebral atherosclerosis is associated with cystic infarcts and microinfarcts but not Alzheimer pathologic changes

BACKGROUND AND PURPOSE

Some studies have reported associations between intracranial atherosclerosis and Alzheimer disease pathology. We aimed to correlate severity of cerebral atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy with neurofibrillary tangles, neuritic plaques, and cerebral infarcts.

METHODS

This autopsy study (n=163) was drawn from a longitudinal study of subcortical ischemic vascular disease, Alzheimer disease, and normal aging. Multivariable logistic regression models were used to test associations among the 3 forms of cerebrovascular disease and the presence of ischemic and neurodegenerative brain lesions. Apolipoprotein E genotype was included as a covariate in these multivariable models.

RESULTS

Cerebral atherosclerosis was positively associated with microinfarcts (odds ratio [OR], 2.3; 95% confidence interval [CI], 1.2-4.4) and cystic infarcts (OR, 2.0; 95% CI, 1.0-4.2) but not Alzheimer disease pathology. Arteriolosclerosis showed a positive correlation with lacunar infarcts (OR, 2.0; 95% CI, 1.0-4.2) but not Alzheimer disease pathology. Cerebral amyloid angiopathy was inversely associated with lacunar infarcts (OR, 0.6; 95% CI, 0.41-1.1), but positively associated with Braak and Braak stage (OR, 1.5; 95% CI, 1.1-2.1) and Consortium to Establish a Registry for Alzheimer Disease plaque score (OR, 1.5; 95% CI, 1.1-2.2).

CONCLUSIONS

Microinfarcts, which have been correlated with severity of cognitive impairment, were most strongly associated with atherosclerosis. Possible pathogenetic mechanisms include artery-to-artery emboli, especially microemboli that may include atheroemboli or platelet-fibrin emboli. Arteriolosclerosis was positively, whereas cerebral amyloid angiopathy was negatively correlated with lacunar infarcts, which might prove helpful in clinical differentiation of arteriolosclerotic from cerebral amyloid angiopathy-related vascular brain injury.

Mitochondria and vascular lesions as a central target for the development of Alzheimer's disease and Alzheimer disease-like pathology in transgenic mice

Accumulating evidence strongly suggests that the AD brain is characterized by impairments in energy metabolism, and vascular hypoperfusion, whereby oxidative stress appears to be an especially important contributor to neuronal death and development of AD pathology. We hypothesized that mitochondria play a key role in the generation of reactive oxygen species, resulting in oxidative damage to neuronal cell bodies, as well as other cellular compartments in the AD brain. All of these changes have been found to accompany AD pathology. In this review we have outlined recent evidence from the literature and our own original studies concerning the role of mitochondrial abnormalities and vascular damage in the pathogenesis of AD and AD-like pathology in transgenic mice (as a model for human AD). We examined ultrastructural features of vascular lesions and mitochondria from vascular wall cells in human AD brain biopsies, in human short post-mortem brain tissues and in yeast artificial chromosome (YAC) and C57B6/SJL transgenic positive (Tg+) mice overexpressing amyloid beta precursor protein (A beta PP). In situ hybridization using mitochondrial DNA (mtDNA) probes for human wild type, 5kb deleted and mouse mtDNA was performed along with immunocytochemistry using antibodies against amyloid beta precursor protein (A beta PP), 8-hydroxy-2'-guanosine (8OHG) and cytochrome C oxidase (COX) were studied at the electron microscopic levels. There was a higher degree of amyloid deposition in the vascular walls of the human AD, YAC and C57B6/SJL Tg(+) mice compared to aged-matched controls. In addition, vessels with more severe lesions showed immunopositive staining for APP and possessed large, lipid-laden vacuoles in the cytoplasm of endothelial cells (EC). Significantly more mitochondrial abnormalities were seen in human AD, YAC and C57B6/SJL Tg(+) mouse microvessels where lesions occurred. In situ hybridization using wild and chimera (5 kB) mtDNA probes revealed positive signals in damaged mitochondria from the vascular endothelium and in perivascular cells of lesioned microvessels close to regions of large amyloid deposition. These features were absent in undamaged regions of human AD tissues, YAC and C57B6/SJL Tg(+) mouse tissues and in aged-matched control subjects. In addition, vessels with atherosclerotic lesions revealed endothelium and perivascular cells possessing clusters of wild and deleted mtDNA positive probes. These mtDNA deletions were accompanied by increased amounts of immunoreactive APP, 8OHG and COX in the same cellular compartment. Our observations first time demonstrate that vascular wall cells, especially their mitochondria, appear to be a central target for oxidative stress induced damage.

A shift in microglial β-amyloid binding in Alzheimer's disease is associated with cerebral amyloid angiopathy

Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA) are two common pathologies associated with β-amyloid (Aβ) accumulation and inflammation in the brain; neither is well understood. The objective of this study was to evaluate human post-mortem brains from AD subjects with purely parenchymal pathology, and those with concomitant CAA (and age-matched controls) for differential expression of microglia-associated Aβ ligands thought to mediate Aβ clearance and the association of these receptors with complement activation. Homogenates of brain parenchyma and enriched microvessel fractions from occipital cortex were probed for levels of C3b, membrane attack complex (MAC), CD11b and α-2-macroglobulin and immunoprecipitation was used to immunoprecipitate (IP) CD11b complexed with C3b and Aβ. Both C3b and MAC were significantly increased in CAA compared to AD-only and controls and IP showed significantly increased CD11b/C3b complexes with Aβ in AD/CAA subjects. Confocal microscopy was used to visualize these interactions. MAC was remarkably associated with CAA-affected blood vessels compared to AD-only and control vessels. These findings are consistent with an Aβ clearance mechanism via microglial CD11b that delivers Aβ and C3b to blood vessels in AD/CAA, which leads to Aβ deposition and propagation of complement to the cytolytic MAC, possibly leading to vascular fragility.