Optimal blood tau species for the detection of Alzheimer's disease neuropathology: an immunoprecipitation mass spectrometry and autopsy study

Plasma-to-autopsy studies are essential for validation of blood biomarkers and understanding their relation to Alzheimer's disease (AD) pathology. Few such studies have been done on phosphorylated tau (p-tau) and those that exist have made limited or no comparison of the different p-tau variants. This study is the first to use immunoprecipitation mass spectrometry (IP-MS) to compare the accuracy of eight different plasma tau species in predicting autopsy-confirmed AD. The sample included 123 participants (AD = 69, non-AD = 54) from the Boston University Alzheimer's disease Research Center who had an available ante-mortem plasma sample and donated their brain. Plasma samples proximate to death were analyzed by targeted IP-MS for six different tryptic phosphorylated (p-tau-181, 199, 202, 205, 217, 231), and two non-phosphorylated tau (195-205, 212-221) peptides. NIA-Reagan Institute criteria were used for the neuropathological diagnosis of AD. Binary logistic regressions tested the association between each plasma peptide and autopsy-confirmed AD status. Area under the receiver operating curve (AUC) statistics were generated using predicted probabilities from the logistic regression models. Odds Ratio (OR) was used to study associations between the different plasma tau species and CERAD and Braak classifications. All tau species were increased in AD compared to non-AD, but p-tau217, p-tau205 and p-tau231 showed the highest fold-changes. Plasma p-tau217 (AUC = 89.8), p-tau231 (AUC = 83.4), and p-tau205 (AUC = 81.3) all had excellent accuracy in discriminating AD from non-AD brain donors, even among those with CDR < 1). Furthermore, p-tau217, p-tau205 and p-tau231 showed the highest ORs with both CERAD (ORp-tau217 = 15.29, ORp-tau205 = 5.05 and ORp-tau231 = 3.86) and Braak staging (ORp-tau217 = 14.29, ORp-tau205 = 5.27 and ORp-tau231 = 4.02) but presented increased levels at different amyloid and tau stages determined by neuropathological examination. Our findings support plasma p-tau217 as the most promising p-tau species for detecting AD brain pathology. Plasma p-tau231 and p-tau205 may additionally function as markers for different stages of the disease.

Cross-sectional and longitudinal evaluation of plasma glial fibrillary acidic protein to detect and predict clinical syndromes of Alzheimer's disease

Introduction

This study examined plasma glial fibrillary acidic protein (GFAP) as a biomarker of cognitive impairment due to Alzheimer's disease (AD) with and against plasma neurofilament light chain (NfL), and phosphorylated tau (p-tau)181+231.

Methods

Plasma samples were analyzed using Simoa platform for 567 participants spanning the AD continuum. Cognitive diagnosis, neuropsychological testing, and dementia severity were examined for cross-sectional and longitudinal outcomes.

Results

Plasma GFAP discriminated AD dementia from normal cognition (adjusted mean difference = 0.90 standard deviation [SD]) and mild cognitive impairment (adjusted mean difference = 0.72 SD), and demonstrated superior discrimination compared to alternative plasma biomarkers. Higher GFAP was associated with worse dementia severity and worse performance on 11 of 12 neuropsychological tests. Longitudinally, GFAP predicted decline in memory, but did not predict conversion to mild cognitive impairment or dementia.

Discussion

Plasma GFAP was associated with clinical outcomes related to suspected AD and could be of assistance in a plasma biomarker panel to detect in vivo AD.

The Current of Consciousness: Neural Correlates and Clinical Aspects

PURPOSE OF REVIEW

In this review, we summarize the current understanding of consciousness including its neuroanatomic basis. We discuss major theories of consciousness, physical exam-based and electroencephalographic metrics used to stratify levels of consciousness, and tools used to shed light on the neural correlates of the conscious experience. Lastly, we review an expanded category of 'disorders of consciousness,' which includes disorders that impact either the level or experience of consciousness.

RECENT FINDINGS

Recent studies have revealed many of the requisite EEG, ERP, and fMRI signals to predict aspects of the conscious experience. Neurological disorders that disrupt the reticular activating system can affect the level of consciousness, whereas cortical disorders from seizures and migraines to strokes and dementia may disrupt phenomenal consciousness. The recently introduced memory theory of consciousness provides a new explanation of phenomenal consciousness that may explain better than prior theories both experimental studies and the neurologist's clinical experience. Although the complete neurobiological basis of consciousness remains a mystery, recent advances have improved our understanding of the physiology underlying level of consciousness and phenomenal consciousness.

Ante-mortem plasma phosphorylated tau (181) predicts Alzheimer's disease neuropathology and regional tau at autopsy

Blood-based biomarkers such as tau phosphorylated at threonine 181 (phosphorylated-tau181) represent an accessible, cost-effective and scalable approach for the in vivo detection of Alzheimer's disease pathophysiology. Plasma-pathological correlation studies are needed to validate plasma phosphorylated-tau181 as an accurate and reliable biomarker of Alzheimer's disease neuropathological changes. This plasma-to-autopsy correlation study included participants from the Boston University Alzheimer's Disease Research Center who had a plasma sample analysed for phosphorylated-tau181 between 2008 and 2018 and donated their brain for neuropathological examination. Plasma phosphorelated-tau181 was measured with single molecule array technology. Of 103 participants, 62 (60.2%) had autopsy-confirmed Alzheimer's disease. Average time between blood draw and death was 5.6 years (standard deviation = 3.1 years). Multivariable analyses showed higher plasma phosphorylated-tau181 concentrations were associated with increased odds for having autopsy-confirmed Alzheimer's disease [AUC = 0.82, OR = 1.07, 95% CI = 1.03-1.11, P < 0.01; phosphorylated-tau standardized (z-transformed): OR = 2.98, 95% CI = 1.50-5.93, P < 0.01]. Higher plasma phosphorylated-tau181 levels were associated with increased odds for having a higher Braak stage (OR = 1.06, 95% CI = 1.02-1.09, P < 0.01) and more severe phosphorylated-tau across six cortical and subcortical brain regions (ORs = 1.03-1.06, P < 0.05). The association between plasma phosphorylated-tau181 and Alzheimer's disease was strongest in those who were demented at time of blood draw (OR = 1.25, 95%CI = 1.02-1.53), but an effect existed among the non-demented (OR = 1.05, 95% CI = 1.01-1.10). There was higher discrimination accuracy for Alzheimer's disease when blood draw occurred in years closer to death; however, higher plasma phosphorylated-tau181 levels were associated with Alzheimer's disease even when blood draw occurred >5 years from death. Ante-mortem plasma phosphorylated-tau181 concentrations were associated with Alzheimer's disease neuropathology and accurately differentiated brain donors with and without autopsy-confirmed Alzheimer's disease. These findings support plasma phosphorylated-tau181 as a scalable biomarker for the detection of Alzheimer's disease.

Distinguishing Between Genuine and Feigned Dementia Using Event-related Potentials

BACKGROUND

Individuals with probable Alzheimer disease (AD) may perform below cutoffs on traditional, memory-based performance validity tests. Previous studies have found success using event-related potentials (ERPs) to detect feigned neurocognitive impairment in younger populations.

OBJECTIVE

To evaluate the utility of an auditory oddball task in conjunction with the P3b peak amplitude to distinguish probable AD from simulated dementia.

METHOD

Twenty individuals with probable AD and 20 older healthy controls (HC) underwent an ERP auditory oddball protocol and the Test of Memory Malingering (TOMM). The HC were asked to perform honestly for one condition and to simulate dementia for the other. The individuals with probable AD were asked to perform honestly. The P3b peak amplitude and button press accuracy were collected from each participant and were analyzed to determine their effectiveness in detecting performance validity.

RESULTS

The P3b peak amplitude remained stable regardless of behavioral condition in the HC group. When combined with the TOMM Trial 2 score, the P3b peak amplitude further improved the ability to correctly differentiate individuals with probable AD from HC simulating dementia with 100% sensitivity and 90% specificity.

CONCLUSION

The P3b peak amplitude was found to be an effective physiologic measure of cognitive impairment in individuals with probable AD compared with HC simulating dementia. When combined with the TOMM Trial 2 score, the P3b peak amplitude served as a promising performance validity measure for differentiating individuals with probable AD from HC simulating dementia.

Amyloid PET ordering practices in a memory disorders clinic

Introduction

This study assessed the ordering of amyloid positron emission tomography (PET) scans in a Veterans Affairs (VA) memory disorders clinic as part of routine clinical care, with possible implications for the extent to which ordering may occur outside of the VA in the future if covered by insurance.

Methods

Clinical features predictive of ordering amyloid PET scans were retrospectively assessed; the percentage of patients who met appropriate use criteria were evaluated.

Results

Among 565 veterans, 34.9% of received an amyloid PET scan and 98.0% of these were consistent with appropriate use criteria. Patients with a PET were younger and more likely to have an initial diagnosis of Alzheimer's disease (AD). Of patients without an amyloid PET scan ordered, 64.4% would have met appropriate use criteria for amyloid PET.

Discussion

The majority of scans ordered were consistent with appropriate use criteria and more patients were eligible than received a scan. The current study's findings that approximately one-third of patients in a memory disorders clinic received an amyloid PET scan has implications for memory disorders clinics inside and outside of the US Veterans Health Administration.

Impact of amyloid PET in the clinical care of veterans in a tertiary memory disorders clinic

Introduction

We aimed to characterize the clinical impact of amyloid PET (APET) in a veteran population with cognitive decline by comparing differences in management between those who did and did not have an APET.

Methods

This was a retrospective observational study. Poisson regressions and logistic regression were used for comparisons.

Results

Out of 565 veterans, 197 underwent APET; positivity rate was 36.55%. Having an APET was associated with longer follow-up, and increased diagnostic variability; it was not associated with number of additional studies, cholinesterase inhibitors prescription, or referrals to research. A positive APET was associated with less diagnostic variability, fewer additional tests, greater cholinesterase inhibitor prescriptions, and more research referrals.

Discussion

In a medically complex, real-world population, APET yielded lower positivity rates and was not associated with classical clinical utility variables when comparing patients with and without an APET. APET may be used more to "rule out" rather than to confirm Alzheimer's disease.

Highlights

Amyloid PET was associated with longer follow-up, and higher diagnostic variability.No association was seen with cholinesterase inhibitors prescription, or referrals to research.In complex patients, expected amyloid PET positivity rates are lower than previously described.Amyloid PETs were used to "rule out" AD than to confirm the diagnosis of AD.

Plasma p-tau181 shows stronger network association to Alzheimer's disease dementia than neurofilament light and total tau

INTRODUCTION

We examined the ability of plasma hyperphosphorylated tau (p-tau)181 to detect cognitive impairment due to Alzheimer's disease (AD) independently and in combination with plasma total tau (t-tau) and neurofilament light (NfL).

METHODS

Plasma samples were analyzed using the Simoa platform for 235 participants with normal cognition (NC), 181 with mild cognitive impairment due to AD (MCI), and 153 with AD dementia. Statistical approaches included multinomial regression and Gaussian graphical models (GGMs) to assess a network of plasma biomarkers, neuropsychological tests, and demographic variables.

RESULTS

Plasma p-tau181 discriminated AD dementia from NC, but not MCI, and correlated with dementia severity and worse neuropsychological test performance. Plasma NfL similarly discriminated diagnostic groups. Unlike plasma NfL or t-tau, p-tau181 had a direct association with cognitive diagnosis in a bootstrapped GGM.

DISCUSSION

These results support plasma p-tau181 for the detection of AD dementia and the use of blood-based biomarkers for optimal disease detection.

A comparison between tau and amyloid-β cerebrospinal fluid biomarkers in chronic traumatic encephalopathy and Alzheimer disease

BACKGROUND

Cerebrospinal fluid (CSF) tau and beta-amyloid levels in chronic traumatic encephalopathy (CTE), a disease which can be clinically indistinguishable from Alzheimer's disease (AD), are largely unknown. We examined postmortem CSF analytes among participants with autopsy confirmed CTE and AD.

METHODS

In this cross-sectional study 192 participants from the Boston University AD Research Center, VA-BU-CLF Center, and Framingham Heart Study (FHS) had post-mortem CSF collected at autopsy. Participants were divided into pathological groups based on AD and CTE criteria, with 61 CTE participants (18 low, 43 high stage), 79 AD participants (23 low, 56 intermediate to high), 11 participants with CTE combined with AD, and 41 participants lacking both CTE and AD neuropathology. The Meso Scale Discovery immunoassay system was utilized to measure amyloid-beta (Aβ1-40, Aβ1-42), total tau (t-tau), and phosphorylated tau (p-tau181 and p-tau231). CSF analytes were then compared across the pathological groups: no CTE/no AD (control), Low CTE, Low AD, High CTE, Intermediate/High AD, and AD+CTE.

RESULTS

Among the Low disease state groups, the Low CTE group had significantly higher levels of p-tau231 versus the control group and compared to the Low AD group. The Low CTE group was also found to have significantly lower levels of Aβ1-42 compared to the control group. The high CTE group had higher levels of p-tau231 and lower levels of Aβ1-42 compared to Intermediate/High AD group.

CONCLUSIONS

Importantly, p-tau231 and Aβ1-42 were predictors of diagnosis of CTE vs. control and CTE vs. AD. Increased CSF p-tau231 is a promising potentially sensitive biomarker of CTE, and CSF Aβ1-42 needs further investigation in CTE.

Associations between misinformation around COVID‐19 pandemic, severity of social isolation, and cognitive impairment

Background

In the past year, new research has focused on the degree of misinformation regarding the COVID‐19 pandemic in younger and older adults. However, no study has assessed how social isolation and cognitive status influence misinformation regarding the COVID‐19 pandemic. For this reason, we sought to investigate the differences in misinformation on the current pandemic in older individuals with and without cognitive impairment and social isolation in Boston, MA (United States) and Chieti (Italy).

Method

Data has been obtained from 49 subjects from the Boston cohort and 138 from the Italian cohort. Both healthy older adults and individuals diagnosed with Mild Cognitive Impairment (MCI) or Alzheimer’s Disease (AD) Dementia were included. Cognitive status was assessed with a telephone administered neuropsychological battery and blind MoCA. Social isolation was evaluated with the Lubben social isolation scale and misinformation with a COVID‐19 Misinformation Questionnaire. Associations between these variables were assessed using Pearson correlation and binary logistic regression.

Result

35 participants in our sample (26%) met the cutoff for social isolation. 95 subjects (70%) were cognitively impaired. Subjects that were at a higher risk of being socially isolated were more cognitively impaired (r=0.43, N=181, p<.001). Also, they were less likely to know the correct age group that is most affected by the pandemic (b =0.06; p <0.05) and were less likely to feel informed about protective measures that should be taken to avoid contracting COVID‐19 (r=0.24, N=181, p<.001). Subjects that were more cognitively impaired were more likely to think that the COVID‐19 was a bioweapon developed by a government or terrorist organization (b =0.15; p <.001) and were more likely to incorrectly think that a person could not be COVID‐19 positive and be asymptomatic (b =0.17; p <.01). More analysis will be completed once recruitment is completed.

Conclusion

Social isolation and cognitive impairment were associated with a higher degree of misinformation about COVID‐19 and less information about protective measures against infection, making patients with these characteristics a vulnerable population during the current pandemic.

Beliefs about the COVID‐19 pandemic, trust in government, and vaccine intention in older adults with cognitive impairment in the United States and Italy

Background

The degree and spread of misinformation regarding the COVID‐19 pandemic has been prolific, influencing individuals of all ages. We examined belief in misinformation in older individuals with and without cognitive impairment in Boston, MA (United States) and Chieti (Italy). The purpose of this investigation was to compare the two cohorts on specific misconceptions, trust in media and government, perceived risk regarding COVID‐19, and their relation to COVID‐19 vaccine hesitancy and intention.

Method

Forty‐seven subjects from the U.S. (mean age = 75.4, SD = 9.4) and 134 subjects from Italy (mean age = 72.2, SD = 7.7) were administered a telephone neuropsychological battery and MoCA. One hundred twenty‐two individuals (67.4%) met the cutoff for cognitive impairment. Individuals answered a COVID‐19 Misinformation Questionnaire and Perceived Risk Scale. A Vaccine Hesitancy Scale was administered 4‐6 months after the initial assessment. Comparisons were made between the two cohorts using binary logistic regression, controlling for age, education, and cognitive status (i.e., MoCA).

Results

Individuals in the Italian cohort demonstrated greater perceived risk of contracting COVID‐19 and also greater trust in the government as a source of information. A large proportion of the sample (N=160; 88.4%) rated the media as not at all trustworthy. Greater cognitive impairment was predictive of misconception endorsement. Further, individuals in the U.S. cohort were approximately four times as likely as individuals in the Italian cohort to believe that that COVID‐19 was a bioweapon developed by a government or terrorist organization. Trust indices were not related to misconception belief. Examination of vaccine hesitancy, and confirmation of the preliminary analyses, will be undertaken following completed recruitment and testing.

Conclusion

When individuals hold knowledge that is incorrect, the consequences can be manifold. From our preliminary analyses, we found that trust in government was not related to misconception endorsement; however, differences emerged between the U.S. and Italian cohorts. This examination provides a broad, cultural context to complex health beliefs, with specific implications for health behaviors such as vaccine intention, for individuals with and without cognitive impairment.

Impact of C-Reactive Protein on Cognition and Alzheimer Disease Biomarkers in Homozygous APOE ɛ4 Carriers

BACKGROUND AND OBJECTIVES

Previous research has shown that elevated blood C-reactive protein (CRP) is associated with increased Alzheimer disease (AD) risk only in APOE ε4 allele carriers; the objective of this study was to examine the interactive effects of plasma CRP and APOE genotype on cognition and AD biomarkers.

METHODS

Data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) study were analyzed, including APOE genotype; plasma CRP concentrations; diagnostic status (i.e., mild cognitive impairment and dementia due to AD); Mini-Mental State Examination (MMSE) and Clinical Dementia Rating Dementia Staging Instrument scores; CSF concentrations of β-amyloid peptide (Aβ42), total tau (t-Tau) and phosphorylated tau (p-Tau); and amyloid (AV45) PET imaging. Multivariable regression analyses tested the associations between plasma CRP and APOE on cognitive and biomarker outcomes.

RESULTS

Among 566 ADNI participants, 274 (48.4%) had no, 222 (39.2%) had 1, and 70 (12.4%) had 2 APOE ε4 alleles. Among only participants who had 2 APOE ε4 alleles, elevated CRP was associated with lower MMSE score at baseline (β [95% confidence interval] -0.52 [-1.01, -0.12]) and 12-month follow-up (β -1.09 [-1.88, -0.17]) after adjustment for sex, age, and education. The interaction of 2 APOE ε4 alleles and elevated plasma CRP was associated with increased CSF levels of t-Tau (β = 11.21, SE 3.37, p < 0.001) and p-Tau (β = +2.74, SE 1.14, p < 0.01). Among those who had no APOE ε4 alleles, elevated CRP was associated with decreased CSF t-Tau and p-Tau. These effects were stronger at the 12-month follow-up.

DISCUSSION

CRP released during peripheral inflammation could be a mediator in APOE ε4-related AD neurodegeneration and serve as a drug target for AD.

Head Injury Exposure in Veterans Presenting to Memory Disorders Clinic: An Observational Study of Clinical Characteristics and Relationship of Event-Related Potentials and Imaging Markers

Objective: Traumatic brain injury (TBI) and repetitive head impacts (RHI) related to blasts or contact sports are commonly reported among military service members. However, the clinical implications of remote TBI and RHI in veterans remains a challenge when evaluating older veterans at risk of neurodegenerative conditions including Alzheimer's disease (AD) and Chronic Traumatic Encephalopathy (CTE). This study aimed to test the hypothesis that veterans in a memory disorders clinic with remote head injury would be more likely to have neurodegenerative clinical diagnoses, increased rates of amyloid PET positivity, higher prevalence of cavum septum pellucidi/vergae, and alterations in event-related potential (ERP) middle latency auditory evoked potentials (MLAEPs) and long latency ERP responses compared to those without head injuries. Methods: Older veterans aged 50-100 were recruited from a memory disorders clinic at VA Boston Healthcare system with a history of head injury (n = 72) and without head injury history (n = 52). Patients were classified as reporting prior head injury including TBI and/or RHI exposure based on self-report and chart review. Participants underwent MRI to determine presence/absence of cavum and an ERP auditory oddball protocol. Results: The head injury group was equally likely to have a positive amyloid PET compared to the non-head injury group. Additionally, the head injury group were less likely to have a diagnosis of a neurodegenerative condition than those without head injury. P200 target amplitude and MLAEP amplitudes for standard and target tones were decreased in the head injury group compared to the non-head injury group while P3b amplitude did not differ. Conclusions: Veterans with reported remote head injury evaluated in a memory disorders clinic were not more likely to have a neurodegenerative diagnosis or imaging markers of neurodegeneration than those without head injury. Decreased P200 target and MLAEP target and standard tone amplitudes in the head injury group may be relevant as potential diagnostic markers of remote head injury.

Chronic Traumatic Encephalopathy

PURPOSE OF REVIEW

This article provides a discussion on the current state of knowledge of chronic traumatic encephalopathy (CTE), with an emphasis on clinical features and emerging biomarkers of the condition.

RECENT FINDINGS

The results of several large brain bank case series among subjects with a history of contact sports or repetitive head trauma have indicated that a high frequency of CTE may exist in this population. However, the true prevalence of CTE among individuals with a history of head trauma remains unknown, given that individuals who experienced cognitive, behavioral, and mood symptoms during life are more likely to have their brains donated for autopsy at death and epidemiologic studies of the condition are lacking. Neuropathologic consensus criteria have been published. Research-based clinical criteria have been proposed and are beginning to be applied, but the definitive diagnosis of CTE in a living patient remains impossible without effective biomarkers for the condition, which is an active area of study.

SUMMARY

The field of CTE research is rapidly growing and parallels many of the advances seen for other neurodegenerative conditions, such as Alzheimer disease decades ago.

Lifetime exposure to ultraviolet radiation and the risk of multiple sclerosis in the US radiologic technologists cohort study

BACKGROUND

Low exposure to ultraviolet radiation (UVR) from sunlight may be a risk factor for developing multiple sclerosis (MS). Possible pathways may be related to effects on immune system function or vitamin D insufficiency, as UVR plays a role in the production of the active form of vitamin D in the body.

OBJECTIVE

This study examined whether lower levels of residential UVR exposure from sunlight were associated with increased MS risk in a cohort of radiologic technologists.

METHODS

Participants in the third and fourth surveys of the US Radiologic Technologists (USRT) Cohort Study eligible (N = 39,801) for analysis provided complete residential histories and reported MS diagnoses. MS-specialized neurologists conducted medical record reviews and confirmed 148 cases. Residential locations throughout life were matched to satellite data from NASA's Total Ozone Mapping Spectrometer (TOMS) project to estimate UVR dose.

RESULTS

Findings indicate that MS risk increased as average lifetime levels of UVR exposures in winter decreased. The effects were consistent across age groups <40 years. There was little indication that low exposures during summer or at older ages were related to MS risk.

CONCLUSION

Our findings are consistent with the hypothesis that UVR exposure reduces MS risk and may ultimately suggest prevention strategies.

Late Positive Component Event-related Potential Amplitude Predicts Long-term Classroom-based Learning

It is difficult to predict whether newly learned information will be retrievable in the future. A biomarker of long-lasting learning, capable of predicting an individual's future ability to retrieve a particular memory, could positively influence teaching and educational methods. ERPs were investigated as a potential biomarker of long-lasting learning. Prior ERP studies have supported a dual-process model of recognition memory that categorizes recollection and familiarity as distinct memorial processes with distinct ERP correlates. The late positive component is thought to underlie conscious recollection and the frontal N400 signal is thought to reflect familiarity [Yonelinas, A. P. Components of episodic memory: The contribution of recollection and familiarity. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences, 356, 1363-1374, 2001]. Here we show that the magnitude of the late positive component, soon after initial learning, is predictive of subsequent recollection of anatomical terms among medical students 6 months later.

Psychosis in Spinocerebellar Ataxias: a Case Series and Study of Tyrosine Hydroxylase in Substantia Nigra

Spinocerebellar ataxias are a genetically heterogeneous group of degenerative diseases typically characterized by progressive ataxia and to various degrees, neuropathy, amyotrophy, and ocular abnormalities. There is increasing evidence for non-motor manifestations associated with cerebellar syndromes including cognitive and psychiatric features. We studied a retrospective clinical case series of eight subjects with spinocerebellar ataxias (SCAs) 2, 3, 7, and 17, all displaying features of psychosis, and also measured tyrosine hydroxylase (TH) staining of the substantia nigra (SN) at autopsy, among four of the subjects. We hypothesized that increased dopamine production in the SN may underlie the pathophysiology of psychosis in SCAs, given evidence of increased dopamine production in the SN in schizophrenia, as measured by TH staining. We analyzed differences in TH staining between the SCA psychosis cohort (n = 4), a heterogeneous ataxic cohort without psychosis (n = 22), and non-diseased age- and sex-matched control group (n = 12). SCA subjects with psychosis did not differ significantly in TH staining versus ataxic cases without psychosis. There was, however, increased TH staining in the ataxic cohort with and without psychosis (n = 26), compared to non-diseased controls (n = 12). Psychotic features were similar across subjects, with the presence of delusions, paranoia, and auditory hallucinations. Our findings are preliminary because of small numbers of subjects and variable neuropathology; however, they suggest that psychosis is a clinical feature of SCAs and may be under-recognized. While the underlying pathophysiology remains to be fully established, it may be related to extra-cerebellar pathology, including a possible propensity for increased dopamine activity in the SN.

Related B cell clones that populate the CSF and CNS of patients with multiple sclerosis produce CSF immunoglobulin

We investigated the overlap shared between the immunoglobulin (Ig) proteome of the cerebrospinal fluid (CSF) and the B cell Ig-transcriptome of CSF and the central nervous system (CNS) tissue of three patients with multiple sclerosis. We determined the IgG-proteomes of CSF by mass spectrometry, and compared them to the IgG-transcriptomes from CSF and brain lesions, which were analyzed by cDNA cloning. Characteristic peptides that were identified in the CSF-proteome could also be detected in the transcriptomes of both, brain lesions and CSF, providing evidence for a strong overlap of the IgG repertoires in brain lesions and in the CSF.

In vivo proton magnetic resonance spectroscopy reveals region specific metabolic responses to SIV infection in the macaque brain

BACKGROUND

In vivo proton magnetic resonance spectroscopy (1H-MRS) studies of HIV-infected humans have demonstrated significant metabolic abnormalities that vary by brain region, but the causes are poorly understood. Metabolic changes in the frontal cortex, basal ganglia and white matter in 18 SIV-infected macaques were investigated using MRS during the first month of infection.

RESULTS

Changes in the N-acetylaspartate (NAA), choline (Cho), myo-inositol (MI), creatine (Cr) and glutamine/glutamate (Glx) resonances were quantified both in absolute terms and relative to the creatine resonance. Most abnormalities were observed at the time of peak viremia, 2 weeks post infection (wpi). At that time point, significant decreases in NAA and NAA/Cr, reflecting neuronal injury, were observed only in the frontal cortex. Cr was significantly elevated only in the white matter. Changes in Cho and Cho/Cr were similar across the brain regions, increasing at 2 wpi, and falling below baseline levels at 4 wpi. MI and MI/Cr levels were increased across all brain regions.

CONCLUSION

These data best support the hypothesis that different brain regions have variable intrinsic vulnerabilities to neuronal injury caused by the AIDS virus.

Automatic repositioning of MRSI voxels in longitudinal studies: impact on reproducibility of metabolite concentration measurements

PURPOSE

To study an automatic repositioning method to reduce variability in longitudinal MRSI exams based on a priori image registration. Longitudinal proton MR spectroscopic imaging ((1)H MRSI) exams to study the effects of disease or treatment are becoming increasingly common. However, one source of variability in such exams arises from imperfect relocalization of the MRSI grid in the follow-up exams.

MATERIALS AND METHODS

Six healthy subjects were each scanned three times during the course of 1 day. In each follow-up exam a manually placed MRSI grid was acquired in addition to the automatically repositioned MRSI grid. Then coefficients of variance between baseline and follow-up scans were calculated for N-acetylaspartate, creatine, and choline. In addition, the overall MRSI grid overlap and individual voxel overlaps were also calculated for both the visually and automatically repositioned voxels.

RESULTS

Streamlined workflow, reduced variability of metabolite concentration measurements, and increased voxel overlaps are noted when this automatic repositioning procedure is compared to the visual MRSI grid repositioning approach.

CONCLUSION

Our results suggest that this approach is able to improve reproducibility in longitudinal MRS exams.

Botulinum toxin type a inhibits calcitonin gene-related peptide release from isolated rat bladder

PURPOSE

Increasing evidence suggests that sensory nerve dysfunction may underlie several urological disorders, including interstitial cystitis and sensory urgency. We determined the effect of botulinum toxin type A (Allergan, Irvine, California) on baseline and chemically evoked release of the sensory neuropeptide, calcitonin gene-related peptide in an isolated bladder preparation.

MATERIALS AND METHODS

Whole rat bladders were incubated in a series of tissue baths containing physiological salt solution. Following bladder equilibration in PSS sequential incubation was performed and this sample was used to measure baseline CGRP release. To evoke CGRP release tissue was subsequently incubated in PSS containing capsaicin (30 nM) and adenosine triphosphate (10 microM). To measure the effect of BTX-A on baseline and evoked CGRP release bladders were incubated for 6 hours in an organ bath containing BTX-A (50 microM) or vehicle prior to bladder equilibration. CGRP release was determined by radioimmunoassay.

RESULTS

Mean baseline release of CGRP +/- SEM was 346 +/- 44 pg/gm. Adenosine triphosphate/capsaicin application increased CGRP release by 75% over baseline (606 +/- 98 pg/gm, p < 0.005). BTX-A application resulted in a 19% decrease in baseline release of CGRP, although this difference did not achieve statistical significance. BTX-A application significantly decreased evoked CGRP by 62% vs control (606 +/- 98 vs 229 +/- 21 pg/gm, p < 0.005).

CONCLUSIONS

BTX-A application inhibits the evoked release of CGRP from afferent nerve terminals in isolated rat bladder. This finding suggests a potential clinical benefit of BTX-A for the treatment of interstitial cystitis or sensory urgency.