Structures and Rotational Barriers of a Diiodobinorsnoutane: Energetic Preference for Gauche Conformation.

The diiodobinorsnoutane, bi(5-iodopentacyclo[4.3.0.0(2,4).0(3,8).0(5,7)]non-4-yl) (5), exists in a sterically hindered gauche conformation rather than an anti or an averaged (freely rotating) C2v structure. Density functional theory (DFT) predictions place the gauche conformation 11 kcal/mol more stable than the anti conformation with a barrier of 17 kcal/mol connecting the minima. These are consistent with variable-temperature NMR (17.1 ± 0.8 kcal/mol) estimates and X-ray analysis. Predictions of the torsional profiles of the yet-unsynthesized bromo-, chloro-, and fluoro- analogues show a progressive lowering of the barriers.

TDP-43 mediates degeneration in a novel Drosophila model of disease caused by mutations in VCP/p97.

Inclusion body myopathy associated with Paget's disease of bone and frontotemporal dementia (IBMPFD) is a dominantly inherited degenerative disorder caused by mutations in the valosin-containing protein (VCP7) gene. VCP (p97 in mouse, TER94 in Drosophila melanogaster, and CDC48 in Saccharomyces cerevisiae) is a highly conserved AAA(+) (ATPases associated with multiple cellular activities) ATPase that regulates a wide array of cellular processes. The mechanism of IBMPFD pathogenesis is unknown. To elucidate the pathogenic mechanism, we developed and characterized a Drosophila model of IBMPFD (mutant-VCP-related degeneration). Based on genetic screening of this model, we identified three RNA-binding proteins that dominantly suppressed degeneration; one of these was TBPH, the Drosophila homolog of TAR (trans-activating response region) DNA-binding protein 43 (TDP-43). Here we demonstrate that VCP and TDP-43 interact genetically and that disease-causing mutations in VCP lead to redistribution of TDP-43 to the cytoplasm in vitro and in vivo, replicating the major pathology observed in IBMPFD and other TDP-43 proteinopathies. We also demonstrate that TDP-43 redistribution from the nucleus to the cytoplasm is sufficient to induce cytotoxicity. Furthermore, we determined that a pathogenic mutation in TDP-43 promotes redistribution to the cytoplasm and enhances the genetic interaction with VCP. Together, our results show that degeneration associated with VCP mutations is mediated in part by toxic gain of function of TDP-43 in the cytoplasm. We suggest that these findings are likely relevant to the pathogenic mechanism of a broad array of TDP-43 proteinopathies, including frontotemporal lobar degeneration and amyotrophic lateral sclerosis.

Neurodegenerative diseases: a decade of discoveries paves the way for therapeutic breakthroughs.

A wide variety of neurodegenerative diseases are characterized by the accumulation of intracellular or extracellular protein aggregates. More recently, the genetic identification of mutations in familial counterparts to the sporadic disorders, leading to the development of in vitro and in vivo model systems, has provided insights into disease pathogenesis. The effect of many of these mutations is the abnormal processing of misfolded proteins that overwhelms the quality-control systems of the cell, resulting in the deposition of protein aggregates in the nucleus, cytosol and/or extracellular space. Further understanding of mechanisms regulating protein processing and aggregation, as well as of the toxic effects of misfolded neurodegenerative disease proteins, will facilitate development of rationally designed therapies to treat and prevent these disorders.

Effect of tubing condensate on non-invasive positive pressure ventilators tested under simulated clinical conditions.

RATIONALE: Water condensate in the humidifier tubing can affect bi-level ventilation by narrowing tube diameter and increasing airflow resistance. We investigated room temperature and tubing type as ways to reduce condensate and its effect on bi-level triggering and pressure delivery. In this bench study, the aim was to test the hypothesis that a relationship exists between room temperature and tubing condensate. METHODS: Using a patient simulator, a Res-med bi-level device was set to 18/8 cm H(2)O and run for 6 h at room temperatures of 16°C, 18°C and 20°C. The built-in humidifier was set to a low, medium or high setting while using unheated or insulated tubing or replaced with a humidifier using heated tubing. Humidifier output, condensate, mask pressure and triggering delay of the bi-level were measured at 1 and 6 h using an infrared hygrometer, metric weights, Honeywell pressure transducer and TSI pneumotach. RESULTS: When humidity output exceeded 17.5 mg H(2)O/L, inspiratory pressure fell by 2-15 cm H(2)O and triggering was delayed by 0.2-0.9 s. Heating the tubing avoided any such ventilatory effect whereas warmer room temperatures or insulating the tubing were of marginal benefit. CONCLUSIONS: Users of bi-level ventilators need to be aware of this problem and its solution. Bi-level humidifier tubing may need to be heated to ensure correct humidification, pressure delivery and triggering.

Palatability and Swallowability of Pimavanserin When Mixed with Selected Food Vehicles: An Exploratory Open-Label Crossover Study.

Dysphagia (difficulty swallowing) affects up to 13% of persons 65 years and older and 51% of older persons in nursing homes and can contribute to reduced adherence to oral medications. This was an exploratory, single-center, open-label, randomized, crossover study in healthy older adult participants. Primary objectives were evaluation of palatability (taste) and swallowability of the contents of pimavanserin 34 mg capsules mixed with selected soft foods or a liquid nutritional supplement. Secondary objectives included evaluation of additional palatability endpoints and ease of capsule manipulation for mixing. A total of 18 healthy, older adult participants (mean age 65 years) were included. Mean participant ratings for all food vehicles were "moderately like" to "neither like nor dislike" for palatability and "very easy" to "somewhat easy" for swallowability. Capsule manipulation to allow sprinkling of contents was rated "very easy" or "somewhat easy" by most participants. There were five treatment-emergent adverse events, all mild; two were deemed related to study treatment. The palatability and swallowability of pimavanserin was considered acceptable when administered with certain soft foods or a liquid nutritional supplement by the study participants.

Nosology of Parkinson's disease: looking for the way out of a quagmire.

The discovery of SNCA mutations pathogenic for autosomal-dominant Lewy body Parkinson's disease (PD) in 1997 heralded a revolution in understanding the molecular and genetic basis of PD. Indeed, it now is clear that Lewy body PD is one of many neurodegenerative parkinsonian disorders that result from nigrostriatal degeneration caused by diverse mechanisms. However, to capitalize on these new insights and facilitate efforts to improve the diagnosis and therapy of neurodegenerative movement disorders, it is timely to define a nosology for these diseases that is based on their genetic and molecular underpinnings, as proposed here.

TDP-43: a novel neurodegenerative proteinopathy.

Over the past decade, it has become clear that there is a significant overlap in the clinical spectrum of frontotemporal lobar degeneration and amyotrophic lateral sclerosis (ALS). The identification of TDP-43 as the major disease protein in the pathology of both frontotemporal lobar degeneration with ubiquitin inclusions and ALS provides the first molecular link for these diseases. Pathological TDP-43 is abnormally phosphorylated, ubiquitinated, and cleaved to generate carboxy-terminal fragments in affected brain regions. The normal nuclear expression of TDP-43 is also reduced leading to the hypothesis that sequestration of TDP-43 in pathological inclusions contributes to disease pathogenesis. Thus, TDP-43 is the newest member of the growing list of neurodegenerative proteinopathies, but unique in that it lacks features of brain amyloidosis.

Phosphorylation of S409/410 of TDP-43 is a consistent feature in all sporadic and familial forms of TDP-43 proteinopathies.

Accumulation of hyperphosphorylated, ubiquitinated and N-terminally truncated TAR DNA-binding protein (TDP-43) is the pathological hallmark lesion in most familial and sporadic forms of FTLD-U and ALS, which can be subsumed as TDP-43 proteinopathies. In order to get more insight into the role of abnormal phosphorylation in the disease process, the identification of specific phosphorylation sites and the generation of phosphorylation-specific antibodies are mandatory. Here, we developed and characterized novel rat monoclonal antibodies (1D3 and 7A9) raised against phosphorylated S409/410 of TDP-43. These antibodies were used to study the presence of S409/410 phosphorylation by immunohistochemistry and biochemical analysis in a large series of 64 FTLD-U cases with or without motor neuron disease including familial cases with mutations in progranulin (n = 5), valosin-containing protein (n = 4) and linkage to chromosome 9p (n = 4), 18 ALS cases as well as other neurodegenerative diseases with concomitant TDP-43 pathology (n = 5). Our data demonstrate that phosphorylation of S409/410 of TDP-43 is a highly consistent feature in pathologic inclusions in the whole spectrum of sporadic and familial forms of TDP-43 proteinopathies. Physiological nuclear TDP-43 was not detectable with these mAbs by immunohistochemistry and by immunoblot analyses. While the accumulation of phosphorylated C-terminal fragments was a robust finding in the cortical brain regions of FTLD-U and ALS, usually being much more abundant than the phosphorylated full-length TDP-43 band, spinal cord samples revealed a predominance of full-length TDP-43 over C-terminal fragments. This argues for a distinct TDP-43 species composition in inclusions in cortical versus spinal cord cells. Overall, these mAbs are powerful tools for the highly specific detection of disease-associated abnormal TDP-43 species and will be extremely useful for the neuropathological routine diagnostics of TDP-43 proteinopathies and for the investigation of emerging cellular and animal models for TDP-43 proteinopathies.

Safety, Tolerability, and Pharmacokinetics of the ß-Site Amyloid Precursor Protein-Cleaving Enzyme 1 Inhibitor Verubecestat (MK-8931) in Healthy Elderly Male and Female Subjects.

ß-site amyloid precursor protein-cleaving enzyme 1 (BACE1) is required for the production of ß-amyloid peptides, which are implicated in the etiology of Alzheimer's disease. The safety and pharmacokinetics of the BACE1 inhibitor verubecestat have previously been studied in young adults aged 19-45 years. In this randomized, placebo-controlled, phase I study (protocol MK-8931-006), we investigated the safety, tolerability, and pharmacokinetics of a single dose (100 mg) or multiple doses (30, 80, and 120 mg) once daily for 28 days of verubecestat in healthy elderly subjects. Safety end points were assessed at baseline and during the duration of the study period and indicated that verubecestat was generally well tolerated. Verubecestat pharmacokinetics were similar between healthy elderly male and female subjects and similar to those reported in healthy young males in previous studies. These data supported subsequent studies to assess the potential efficacy of verubecestat in subjects with Alzheimer's disease.

Pharmacokinetics and Pharmacodynamics of the BACE1 Inhibitor Verubecestat (MK-8931) in Healthy Japanese Adults: A Randomized, Placebo-Controlled Study.

ß-site amyloid precursor protein cleaving enzyme 1 (BACE1) is required for the production of ß-amyloid (Aß) peptides and is considered a potential treatment target for Alzheimer's disease (AD). To support Japan's participation in the global clinical development program, we characterized the safety, pharmacokinetics (PKs), and pharmacodynamics of the BACE1 inhibitor verubecestat (MK-8931) in 24 healthy Japanese adults in a two-part, single-center, randomized, placebo-controlled phase I trial (protocol MK-8931-007) and compared the results with historical data from non-Japanese subjects. Both single (20, 100, and 450 mg) and multiple (80 and 150 mg once daily for 14 days) doses of verubecestat were well tolerated. Verubecestat's PK profile was similar in Japanese and non-Japanese subjects. Verubecestat also reduced mean cerebrospinal fluid concentrations of the Aß proteins Aß40, Aß42, and soluble ß fragment of amyloid precursor protein; the level of reduction was comparable between Japanese and non-Japanese subjects. These results support the continued global development of verubecestat as a potential disease-modifying agent for Japanese and non-Japanese subjects who are at risk for developing AD.

Brain Imaging of Alzheimer Dementia Patients and Elderly Controls with 18F-MK-6240, a PET Tracer Targeting Neurofibrillary Tangles.

18F-MK-6240 (18F-labeled 6-(fluoro)-3-(1H-pyrrolo[2,3-c]pyridin-1-yl)isoquinolin-5-amine) is a highly selective, subnanomolar-affinity PET tracer for imaging neurofibrillary tangles (NFTs). Plasma kinetics, brain uptake, and preliminary quantitative analysis of 18F-MK-6240 in healthy elderly (HE) subjects, subjects with clinically probable Alzheimer disease (AD), and subjects with amnestic mild cognitive impairment were characterized in a study that is, to our knowledge, the first to be performed on humans. Methods: Dynamic PET scans of up to 150 min were performed on 4 cognitively normal HE subjects, 4 AD subjects, and 2 amnestic mild cognitive impairment subjects after a bolus injection of 152-169 MBq of 18F-MK-6240 to evaluate tracer kinetics and distribution in brain. Regional SUV ratio (SUVR) and distribution volume ratio were determined using the cerebellar cortex as a reference region. Total distribution volume was assessed by compartmental modeling using radiometabolite-corrected input function in a subgroup of 6 subjects. Results:18F-MK-6240 had rapid brain uptake with a peak SUV of 3-5, followed by a uniformly quick washout from all brain regions in HE subjects; slower clearance was observed in regions commonly associated with NFT deposition in AD subjects. In AD subjects, SUVR between 60 and 90 min after injection was high (approximately 2-4) in regions associated with NFT deposition, whereas in HE subjects, SUVR was approximately 1 across all brain regions, suggesting high tracer selectivity for binding NFTs in vivo. 18F-MK-6240 total distribution volume was approximately 2- to 3-fold higher in neocortical and medial temporal brain regions of AD subjects than in HE subjects and stabilized by 60 min in both groups. Distribution volume ratio estimated by the Logan reference tissue model or compartmental modeling correlated well (R2 > 0.9) to SUVR from 60 to 90 min for AD subjects. Conclusion:18F-MK-6240 exhibited favorable kinetics and high binding levels to brain regions with a plausible pattern for NFT deposition in AD subjects. In comparison, negligible tracer binding was observed in HE subjects. This pilot study suggests that simplified ratio methods such as SUVR can be used to quantify NFT binding. These results support further clinical development of 18F-MK-6240 for potential application in longitudinal studies.

Concomitant TAR-DNA-binding protein 43 pathology is present in Alzheimer disease and corticobasal degeneration but not in other tauopathies.

Pathologic TAR-DNA-binding protein 43 (TDP-43) is a disease protein in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) and amyotrophic lateral sclerosis. We studied the presence, frequency, and distribution of TDP-43 pathology by immunohistochemistry and biochemistry in a series of clinically well-characterized tauopathy patient brains, including 182 Alzheimer disease (AD), 39 corticobasal degeneration, 77 progressive supranuclear palsy, and 12 Pick disease cases and investigated the clinical impact of concomitant TDP-43 pathology in these cases. TAR-DNA-binding protein 43 pathology was found in 25.8% of AD cases. It was restricted to the dentate gyrus and entorhinal cortex in approximately 75% of cases; approximately 25% showed more widespread TDP-43 pathology in frontal and temporal cortices, resembling the FTLD-U subtype associated with progranulin mutations. TAR-DNA-binding protein 43 pathology in AD was associated with significantly longer disease duration, but there was no association with the clinical presentation (148 cases diagnosed as AD and 34 cases diagnosed as frontotemporal lobar degeneration). Progressive supranuclear palsy and Pick disease cases showed no TDP-43 inclusions and no biochemical alterations of TDP-43. There was, however, a unique, predominantly glial TDP-43 pathology with staining of astrocytic plaque-like structures and coiled bodies in 15.4% of corticobasal degeneration cases; this was associated with biochemical TDP-43 changes similar to those in FTLD-U. These findings provide further insight into the burden and clinical significance of TDP-43 pathology in disorders other than FTLD-U and amyotrophic lateral sclerosis.

Clinical studies in familial VCP myopathy associated with Paget disease of bone and frontotemporal dementia.

Inclusion body myopathy with Paget disease of the bone (PDB) and/or frontotemporal dementia (IBMPFD, OMIM 167320), is a progressive autosomal dominant disorder caused by mutations in the Valousin-containing protein (VCP, p97 or CDC48) gene. IBMPFD can be difficult to diagnose. We assembled data on a large set of families to illustrate the number and type of misdiagnoses that occurred. Clinical analysis of 49 affected individuals in nine families indicated that 42 (87%) of individuals had muscle disease. The majority were erroneously diagnosed with limb girdle muscular dystrophy (LGMD), facioscapular muscular dystrophy, peroneal muscular dystrophy, late adult onset distal myopathy, spinal muscular atrophy, scapuloperoneal muscular dystrophy, or amyotrophic lateral sclerosis (ALS) among others. Muscle biopsies showed rimmed vacuoles characteristic of an inclusion body myopathy in 7 of 18 patients (39%), however, inclusion body myopathy was correctly diagnosed among individuals in only families 5 and 15. Frontotemporal dementia (FTD) was diagnosed in 13 individuals (27%) at a mean age of 57 years (range 48.9-60.2 years); however, several individuals had been diagnosed with Alzheimer disease. Histopathological examination of brains of three affected individuals revealed a pattern of ubiquitin positive neuronal intranuclear inclusions and dystrophic neurites. These families expand the clinical phenotype in IBMPFD, a complex disorder caused by mutations in VCP. The presence of PDB in 28 (57%) individuals suggests that measuring serum alkaline phosphatase (ALP) activity may be a useful screen for IBMPFD in patients with myopathy.

Role for Akt3/protein kinase Bgamma in attainment of normal brain size.

Studies of Drosophila and mammals have revealed the importance of insulin signaling through phosphatidylinositol 3-kinase and the serine/threonine kinase Akt/protein kinase B for the regulation of cell, organ, and organismal growth. In mammals, three highly conserved proteins, Akt1, Akt2, and Akt3, comprise the Akt family, of which the first two are required for normal growth and metabolism, respectively. Here we address the function of Akt3. Like Akt1, Akt3 is not required for the maintenance of normal carbohydrate metabolism but is essential for the attainment of normal organ size. However, in contrast to Akt1-/- mice, which display a proportional decrease in the sizes of all organs, Akt3-/- mice present a selective 20% decrease in brain size. Moreover, although Akt1- and Akt3-deficient brains are reduced in size to approximately the same degree, the absence of Akt1 leads to a reduction in cell number, whereas the lack of Akt3 results in smaller and fewer cells. Finally, mammalian target of rapamycin signaling is attenuated in the brains of Akt3-/- but not Akt1-/- mice, suggesting that differential regulation of this pathway contributes to an isoform-specific regulation of cell growth.

Impaired glutamate transport in a mouse model of tau pathology in astrocytes.

Filamentous tau inclusions in neurons and glia are neuropathological hallmarks of tauopathies. The discovery of microtubule-associated protein tau gene mutations that are pathogenic for a heterogenous group of neurodegenerative disorders, called frontotemporal dementia and parkinsonism linked to chromosome-17 (FTDP-17), directly implicate tau abnormalities in the onset/progression of disease. Although the role of tau pathology in neurons in disease pathogenesis is well accepted, the contribution of glial pathology is essentially unknown. We recently generated a transgenic (Tg) mouse model of tau pathology in astrocytes by expressing the human tau protein under the control of the glial fibrillary acidic protein (GFAP) promoter. Both wild-type and FTDP-17 mutant GFAP/tau Tg animals manifest an age-dependent accumulation of tau inclusions in astrocytes that resembles the pathology observed in human tauopathies. We further demonstrate that both strains of Tg mice manifest compromised motor function that correlates with altered expression of the glial glutamate-aspartate transporter and occurs before the development of tau pathology. Subsequently, the Tg mice manifest additional deficits in neuromuscular strength that correlates with reduced expression of glutamate transporter-1 (GLT-1) and occurs concurrent with tau inclusion pathology. Reduced GLT-1 expression was associated with a progressive decrease in sodium-dependent glutamate transport capacity. Reductions in GLT-1 expression were also observed in corticobasal degeneration, a tauopathy with prominent pathology in astrocytes. Less robust changes were observed in Alzheimer's disease in which neuronal tau pathology predominates. Thus, these Tg mice recapitulate features of astrocytic pathology observed in tauopathies and implicate a role for altered astrocyte function in the pathogenesis of these disorders.

TDP-43 in the ubiquitin pathology of frontotemporal dementia with VCP gene mutations.

Frontotemporal dementia with inclusion body myopathy and Paget disease of bone is a rare, autosomal-dominant disorder caused by mutations in the gene valosin-containing protein (VCP). The CNS pathology is characterized by a novel pattern of ubiquitin pathology distinct from sporadic and familial frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) without VCP mutations. TAR DNA binding protein 43 (TDP-43) was recently identified as a major disease protein in the ubiquitin-positive inclusions of sporadic and familial FTLD-U. To determine whether the ubiquitin pathology associated with mutations in VCP is characterized by the accumulation of TDP-43, we analyzed TDP-43 in the CNS pathology of five patients with VCP gene mutations. Accumulations of TDP-43 colocalized with ubiquitin pathology in inclusion body myopathy and Paget disease of bone, including both intranuclear inclusions and dystrophic neurites. Similar to FTLD-U, phosphorylated TDP-43 was detected only in insoluble brain extracts from affected brain regions. Identification of TDP-43, but not VCP, within ubiquitin-positive inclusions supports the hypothesis that VCP gene mutations lead to a dominant negative loss or alteration of VCP function culminating in impaired degradation of TDP-43. TDP-43 is a common pathologic substrate linking a variety of distinct patterns of FTLD-U pathology caused by different genetic alterations.

Clinical, genetic, and pathologic characteristics of patients with frontotemporal dementia and progranulin mutations.

BACKGROUND: Patients with frontotemporal dementia due to mutation of progranulin may have a distinct phenotype. OBJECTIVE: To identify distinct clinical and pathologic features of patients with frontotemporal dementia who have mutations of progranulin (GRN). DESIGN: Retrospective clinical-pathologic study. SETTING: Academic medical center. PATIENTS: Twenty-eight patients with frontotemporal dementia, including 9 with GRN mutations (4 autopsy cases and 5 with only clinical information) and 19 with the identical pathologic diagnosis--frontotemporal lobar degeneration with ubiquitin-positive and tau-negative inclusions (FTLD-U)--and no GRN mutations. MAIN OUTCOME MEASURES: Demographic, symptom, neuropsychological, and autopsy characteristics. RESULTS: Patients with and without a GRN mutation have similar demographic features, although family history is significantly more common in patients with frontotemporal dementia and a GRN mutation. Both patient groups have frequent social and personality complaints. Neuropsychological evaluation reveals a significant recognition memory deficit in patients with a GRN mutation but a significant language deficit only in patients without a GRN mutation. At autopsy, the semiquantitative burden of ubiquitin abnormality is relatively modest in both groups of patients. CONCLUSION: Patients with a GRN mutation differ clinically from those with the same pathologic diagnosis but no GRN mutation.

TDP-43 pathologic lesions and clinical phenotype in frontotemporal lobar degeneration with ubiquitin-positive inclusions.

BACKGROUND: TDP-43 is a major ubiquitinated disease protein in the pathologic condition of frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U). OBJECTIVE: To investigate the demographic, clinical, and neuropsychological features associated with subtypes of FTLD-U with TDP-43 inclusions (FTLD-U/TDP-43). DESIGN: Retrospective clinical-pathologic study. SETTING: Academic medical center. Patients Twenty-three patients with histopathologically proven FTLD-U. MAIN OUTCOME MEASURES: Demographic, symptom, neuropsychological, and autopsy characteristics. RESULTS: There are notably different clinical and neuropsychological patterns of impairment in FTLD-U subtypes. Patients with FTLD-U/TDP-43 characterized by numerous neuronal intracytoplasmic inclusions have shorter survival; patients with FTLD-U/TDP-43 featuring numerous neurites have difficulty with object naming; and patients with FTLD-U/TDP-43 in whom neuronal intranuclear inclusions are present have substantial executive deficits. There are also different anatomical distributions of ubiquitin pathologic features in FTLD-U subgroups, consistent with their cognitive deficits. CONCLUSION: Distinct TDP-43 profiles may affect clinical phenotypes differentially in patients with FTLD-U.

Distinct antemortem profiles in patients with pathologically defined frontotemporal dementia.

BACKGROUND: Clinical-pathologic studies are crucial to understanding brain-behavior relations and improving diagnostic accuracy in neurodegenerative diseases. OBJECTIVE: To establish clinical, neuropsychological, and imaging features of clinically diagnosed patients with frontotemporal dementia (FTD) that help discriminate between pathologically determined tau-positive FTD, tau-negative FTD, and frontal-variant Alzheimer disease. DESIGN: Retrospective clinical-pathologic survey. SETTING: Academic medical center. Patients Sixty-one participants with the clinical diagnosis of a frontotemporal spectrum disorder who underwent a neuropsychological evaluation and had an autopsy-confirmed disease. MAIN OUTCOME MEASURES: Neuropsychological performance and high-resolution structural magnetic resonance imaging (MRI). RESULTS: Distinguishing features of patients with tau-positive FTD include visual perceptual-spatial difficulty and an extrapyramidal disorder significantly more often than other patients, significant cortical atrophy in the frontal and parietal regions as evidenced on MRI, and the burden of pathology is greatest in the frontal and parietal regions. Patients with tau-negative FTD are distinguished by their greater difficulties with social, language, and verbally mediated executive functions, significant cortical atrophy in the frontal and temporal regions as evidenced on MRI, and significant frontal and temporal pathology. Patients with Alzheimer disease at autopsy have significantly impaired delayed recall during episodic memory testing; atrophy that involves temporal areas, including the hippocampus, as evidenced on MRI; and widely distributed pathology including the medial temporal structures. A discriminant function analysis grouped patients on the basis of clinical and neuropsychological features with 87.5% accuracy. CONCLUSION: Clinical, neuropsychological, and imaging profiles can contribute to accurate antemortem diagnosis in FTD.

Multiple comorbid neuropathologies in the setting of Alzheimer's disease neuropathology and implications for drug development.

Dementia is often characterized as being caused by one of several major diseases, such as Alzheimer's disease (AD), cerebrovascular disease, Lewy body disease, or a frontotemporal degeneration. Failure to acknowledge that more than one entity may be present precludes attempts to understand interactive relationships. The clinicopathological studies of dementia demonstrate that multiple pathologic processes often coexist. How overlapping pathologic findings affect the diagnosis and treatment of clinical AD and other dementia phenotypes was the topic taken up by the Alzheimer's Association's Research Roundtable in October 2014. This review will cover the neuropathologic basis of dementia, provide clinical perspectives on multiple pathologies, and discuss therapeutics and biomarkers targeting overlapping pathologies and how these issues impact clinical trials.High prevalence of multiple pathologic findings among individuals with clinical diagnosis of AD suggests that new treatment strategies may be needed to effectively treat AD and other dementing illnesses.