CSF and clinical hallmarks of subcortical dementias: focus on DLB and PDD

Effects of Hydrogen Gas Inhalation on Community-Dwelling Adults of Various Ages: A Single-Arm, Open-Label, Prospective Clinical Trial

Molecular hydrogen (H₂) is a versatile therapeutic agent. H₂ gas inhalation is reportedly safe and has a positive impact on a range of illnesses, including Alzheimer's disease (AD). Herein, we investigated the effects of 4 weeks of H₂ gas inhalation on community-dwelling adults of various ages. Fifty-four participants, including those who dropped out (5%), were screened and enrolled. The selected participants were treated as a single group without randomization. We evaluated the association between total and differential white blood cell (WBC) counts and AD risk at individual levels after 4 weeks of H₂ gas inhalation treatment. The total and differential WBC counts were not adversely affected after H₂ gas inhalation, indicating that it was safe and well tolerated. Investigation of oxidative stress markers such as reactive oxygen species and nitric oxide showed that their levels decreased post-treatment. Furthermore, evaluation of dementia-related biomarkers, such as beta-site APP cleaving enzyme 1 (BACE-1), amyloid beta (Aβ), brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor A (VEGF-A), T-tau, monocyte chemotactic protein-1 (MCP-1), and inflammatory cytokines (interleukin-6), showed that their cognitive condition significantly improved after treatment, in most cases. Collectively, our results indicate that H₂ gas inhalation may be a good candidate for improving AD with cognitive dysfunction in community-dwelling adults of different ages.

Resting state activity and connectivity of the nucleus basalis of Meynert and globus pallidus in Lewy body dementia and Parkinson's disease dementia

Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) are two related diseases which can be difficult to distinguish. There is no objective biomarker which can reliably differentiate between them. The synergistic combination of electrophysiological and neuroimaging approaches is a powerful method for interrogation of functional brain networks in vivo. We recorded bilateral local field potentials (LFPs) from the nucleus basalis of Meynert (NBM) and the internal globus pallidus (GPi) with simultaneous cortical magnetoencephalography (MEG) in six PDD and five DLB patients undergoing surgery for deep brain stimulation (DBS) to look for differences in underlying resting-state network pathophysiology. In both patient groups we observed spectral peaks in the theta (2–8 Hz) band in both the NBM and the GPi. Furthermore, both the NBM and the GPi exhibited similar spatial and spectral patterns of coupling with the cortex in the two disease states. Specifically, we report two distinct coherent networks between the NBM/GPi and cortical regions: (1) a theta band (2–8 Hz) network linking the NBM/GPi to temporal cortical regions, and (2) a beta band (13–22 Hz) network coupling the NBM/GPi to sensorimotor areas. We also found differences between the two disease groups: oscillatory power in the low beta (13–22Hz) band was significantly higher in the globus pallidus in PDD patients compared to DLB, and coherence in the high beta (22–35Hz) band between the globus pallidus and lateral sensorimotor cortex was significantly higher in DLB patients compared to PDD. Overall, our findings reveal coherent networks of the NBM/GPi region that are common to both DLB and PDD. Although the neurophysiological differences between the two conditions in this study are confounded by systematic differences in DBS lead trajectories and motor symptom severity, they lend support to the hypothesis that DLB and PDD, though closely related, are distinguishable from a neurophysiological perspective.

FDG-PET and CSF biomarker accuracy in prediction of conversion to different dementias in a large multicentre MCI cohort

Background/aims

In this multicentre study in clinical settings, we assessed the accuracy of optimized procedures for FDG-PET brain metabolism and CSF classifications in predicting or excluding the conversion to Alzheimer's disease (AD) dementia and non-AD dementias.

Methods

We included 80 MCI subjects with neurological and neuropsychological assessments, FDG-PET scan and CSF measures at entry, all with clinical follow-up. FDG-PET data were analysed with a validated voxel-based SPM method. Resulting single-subject SPM maps were classified by five imaging experts according to the disease-specific patterns, as "typical-AD", "atypical-AD" (i.e. posterior cortical atrophy, asymmetric logopenic AD variant, frontal-AD variant), "non-AD" (i.e. behavioural variant FTD, corticobasal degeneration, semantic variant FTD; dementia with Lewy bodies) or "negative" patterns. To perform the statistical analyses, the individual patterns were grouped either as "AD dementia vs. non-AD dementia (all diseases)" or as "FTD vs. non-FTD (all diseases)". Aβ42, total and phosphorylated Tau CSF-levels were classified dichotomously, and using the Erlangen Score algorithm. Multivariate logistic models tested the prognostic accuracy of FDG-PET-SPM and CSF dichotomous classifications. Accuracy of Erlangen score and Erlangen Score aided by FDG-PET SPM classification was evaluated.

Results

The multivariate logistic model identified FDG-PET "AD" SPM classification (Expβ = 19.35, 95% C.I. 4.8-77.8, p < 0.001) and CSF Aβ42 (Expβ = 6.5, 95% C.I. 1.64-25.43, p < 0.05) as the best predictors of conversion from MCI to AD dementia. The "FTD" SPM pattern significantly predicted conversion to FTD dementias at follow-up (Expβ = 14, 95% C.I. 3.1-63, p < 0.001). Overall, FDG-PET-SPM classification was the most accurate biomarker, able to correctly differentiate either the MCI subjects who converted to AD or FTD dementias, and those who remained stable or reverted to normal cognition (Expβ = 17.9, 95% C.I. 4.55-70.46, p < 0.001).

Conclusions

Our results support the relevant role of FDG-PET-SPM classification in predicting progression to different dementia conditions in prodromal MCI phase, and in the exclusion of progression, outperforming CSF biomarkers.

Homovanillic acid in CSF of mild stage Parkinson's disease patients correlates with motor impairment

In Parkinson's disease (PD), several efforts have been spent in order to find biochemical parameters able to identify the progression of the pathological processes at the basis of the disease. It is already known that advanced PD patients manifesting dyskinesia are featured by the high homovanillic acid (HVA)/dopamine (DA) ratio, suggesting the increased turnover of DA in these patients. Less clear is whether similar changes affect mild and moderate stages of the disease (between 1 and 2.5 of Hoehn & Yahr -H&Y- stage). Hence, here we tested whether cerebrospinal fluid (CSF) concentrations of DA and its major metabolites, either 3,4-dihydroxyphenylacetic acid (DOPAC) or HVA, correlate with motor performance in mild and moderate PD patients. CSF samples were collected after 2 days of anti-PD drugs washout, via lumbar puncture (LP) performed 130 min following administration of oral levodopa (LD) dose (200 mg). LP timing was determined in light of our previous tests clarifying that 2 h after oral LD administration CSF DA concentration reaches a plateau, which was un-respective of PD stage or duration. DA, DOPAC and HVA were assayed by high performance liquid chromatography in a group of 19 patients, distributed in two groups on the basis of the H&Y stage with a cut-off of 1.5. In these PD patients, HVA was correlated with DOPAC (R = 0,56, p < 0,01) and both HVA and DOPAC CSF levels increased in parallel with the motor impairment. More importantly, HVA correlated with motor impairment measured by the Unified Parkinson's Disease Score -III (UPDRS) (R = 0.61; p < 0.0001). The present findings showed the early alteration of the DA pre-synaptic machinery, as documented by the progressive increase of CSF HVA concentrations, which also correlated with PD motor impairment. Therefore, we suggest the potential use of measuring the CSF HVA level as a possible biomarker of PD stage changes in order to monitor the effectiveness of PD-modifying pharmacological therapies.

Cerebrospinal fluid biomarkers in Alzheimer's disease: Diagnostic accuracy and prediction of dementia

INTRODUCTION

Guidelines for the use of cerebrospinal fluid (CSF) biomarkers in the diagnosis of Alzheimer's disease (AD) establish that each laboratory must use internally qualified cutoff values. We determined the concentrations of biomarkers that discriminate cases from controls and combinations that predict the progression to dementia in a Brazilian cohort.

METHODS

Concentrations of amyloid-beta peptide (Aβ1-42), total tau (T-tau), and (181)Thr-phosphorylated-tau (P-tau) were determined in CSF samples from 184 older adults (68 mild cognitive impairment, 41 AD, 34 non-AD cognitive impairment, and 41 controls) by the INNO-BIA AlzBio3 assay.

RESULTS

Cutoff values discriminating AD from controls are as follows: Aβ1-42: 416.0 pg/mL (sensitivity [SE]: 83%, specificity (SP): 70%); T-tau: 76.7 pg/mL (SE: 82%, SP: 67%); P-tau: 36.1 pg/mL (SE: 83%, SP: 49%); Aβ1-42/P-tau <9.53 (SE: 88%, SP: 78%); and Aβ1-42/T-tau <4.13 (SE: 80%; SP: 80%). Combining values Aβ1-42 <416.5 pg/mL and Aβ1-42/P-tau <9.5 best predicted the conversion in 2 years (Cox regression: hazard ratio 7.24 [2.09-25.06], P = .002, SE: 74%, Sp: 73%).

DISCUSSION

Our findings are in line with most of the available evidence in this field; yet, our cutoff values are different from those derived from other laboratories.

Catecholamine-Based Treatment in AD Patients: Expectations and Delusions

In Alzheimer disease, the gap between excellence of diagnostics and efficacy of therapy is wide. Despite sophisticated imaging and biochemical markers, the efficacy of available therapeutic options is limited. Here we examine the possibility that assessment of endogenous catecholamine levels in cerebrospinal fluid (CSF) may fuel new therapeutic strategies. In reviewing the available literature, we consider the effects of levodopa, monoamine oxidase inhibitors, and noradrenaline (NE) modulators, showing disparate results. We present a preliminary assessment of CSF concentrations of dopamine (DA) and NE, determined by HPLC, in a small dementia cohort of either Alzheimer’s disease (AD) or frontotemporal dementia patients, compared to control subjects. Our data reveal detectable levels of DA, NE in CSF, though we found no significant alterations in the dementia population as a whole. AD patients exhibit a small impairment of the DA axis and a larger increase of NE concentration, likely to represent a compensatory mechanism. While waiting for preventive strategies, a pragmatic approach to AD may re-evaluate catecholamine modulation, possibly stratified to dementia subtypes, as part of the therapeutic armamentarium.

Serotonin impairment in CSF of PD patients, without an apparent clinical counterpart

In Parkinson's disease (PD), several studies have detected an impaired serotonin (5-HT) pathway, likely affecting both motor and non-motor domains. However, the precise impact of 5-HT impairment is far from established. Here, we have used a HPLC chromatographic method, in a homogenous cohort (n = 35) of non fluctuating, non dyskinetic PD patients, to assess the concentration of 5-HT and its metabolite 5-HIAA in peripheral cerebrospinal fluid (CSF) obtained from lumbar puncture (LP). LP was performed following three days of therapy withdrawal, in order to vanish the effects of prolonged released dopamine agonists (DA), and in absence of any serotonergic agent. The PD patient group showed a significantly reduced CSF level of both 5-HT and 5-HIAA compared to either age-matched control subjects (n = 18), or Alzheimer's disease patients (n = 20). However, no correlation emerged between 5-HT/5-HIAA concentrations and UPDRS-III (r = −0.12), disease duration (r = −0.1), age (r = −0.27) and MMSE (r = 0.11). Intriguingly, low CSF 5-HT levels did not differ for gender or for motor phenotype (in terms of non-tremor dominant subtype and tremor dominant subtype). Further, low CSF 5-HT levels did not correlate with the presence of depression, apathy or sleep disturbance. Our findings support the contention that 5-HT impairment is a cardinal feature of stable PD, probably representing a hallmark of diffuse Lewy bodies deposition in the brainstem. However, clinical relevance remains uncertain. Given these findings, an add-on therapy with serotonergic agents seems questionable in PD patients, or should be individually tailored, unless severe depression is present.

The spectrum of cognitive impairment in Lewy body diseases

Cognitive impairment represents an important and often defining component of the clinical syndromes of Lewy body disorders: Parkinson's disease and dementia with Lewy bodies. The spectrum of cognitive deficits in these Lewy body diseases encompasses a broad range of clinical features, severity of impairment, and timing of presentation. It is now recognized that cognitive dysfunction occurs not only in more advanced Parkinson's disease but also in early, untreated patients and even in those patients with pre-motor syndromes, such as rapid eye movement behavior disorder and hyposmia. In recent years, the concept of mild cognitive impairment as a transitional or pre-dementia state in Parkinson's disease has emerged. This has led to much research regarding the diagnosis, prognosis, and underlying neurobiology of mild cognitive impairment in Parkinson's disease, but has also raised questions regarding the usefulness of this concept and its application in clinical and research settings. In addition, the conundrum of whether Parkinson's disease dementia and dementia with Lewy bodies represent the same or different entities remains unresolved. Although these disorders overlap in many aspects of their presentations and pathophysiology, they differ in other elements, such as timing of cognitive, behavioral, and motor symptoms; medication responses; and neuropathological contributions. This article examines the spectrum and evolution of cognitive impairment in Lewy body disorders and debates these controversial issues in the field using point-counterpoint approaches.

Altered serum IgG levels to α-synuclein in dementia with Lewy bodies and Alzheimer's disease

Natural self-reactive antibodies in the peripheral blood may play a considerable role in the control of potentially toxic proteins that may otherwise accumulate in the aging brain. The significance of serum antibodies reactive against α-synuclein is not well known. We explored serum IgG levels to monomeric α-synuclein in dementia with Lewy bodies (DLB) and Alzheimer’s disease (AD) with a novel and validated highly sensitive ELISA assay. Antibody levels revealed stark differences in patients compared to healthy subjects and were dependent on diagnosis, disease duration and age. Anti-α-synuclein IgG levels were increased in both patient groups, but in early DLB to a much greater extent than in AD. Increased antibody levels were most evident in younger patients, while with advanced age relatively low levels were observed, similar to healthy individuals, exhibiting stable antibody levels independent of age. Our data show the presence of differentially altered IgG levels against α-synuclein in DLB and AD, which may relate to a disturbed α-synuclein homeostasis triggered by the disease process. These observations may foster the development of novel, possibly preclinical biomarkers and immunotherapeutic strategies that target α-synuclein in neurodegenerative disease.