Barrier dysfunction or drainage reduction: differentiating causes of CSF protein increase

Proteomic comparison between non-purified cerebrospinal fluid and cerebrospinal fluid-derived extracellular vesicles from patients with Alzheimer's, Parkinson's and Lewy body dementia

Dementia is a leading cause of death worldwide, with increasing prevalence as global life expectancy increases. The most common neurodegenerative disorders are Alzheimer's disease (AD), dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). With this study, we took an in-depth look at the proteome of the (non-purified) cerebrospinal fluid (CSF) and the CSF-derived extracellular vesicles (EVs) of AD, PD, PD-MCI (Parkinson's disease with mild cognitive impairment), PDD and DLB patients analysed by label-free mass spectrometry. This has led to the discovery of differentially expressed proteins that may be helpful for differential diagnosis. We observed a greater number of differentially expressed proteins in CSF-derived EV samples (N = 276) compared to non-purified CSF (N = 169), with minimal overlap between both datasets. This finding suggests that CSF-derived EV samples may be more suitable for the discovery phase of a biomarker study, due to the removal of more abundant proteins, resulting in a narrower dynamic range. As disease-specific markers, we selected a total of 39 biomarker candidates identified in non-purified CSF, and 37 biomarker candidates across the different diseases under investigation in the CSF-derived EV data. After further exploration and validation of these proteins, they can be used to further differentiate between the included dementias and may offer new avenues for research into more disease-specific pharmacological therapeutics.

Quantitative evaluation of the thickened dura mater impacting clinical signs in immune-mediated hypertrophic pachymeningitis

OBJECTIVE

This study evaluated the volume of thickened dura mater lesions and their impact on clinical findings in immune-mediated hypertrophic pachymeningitis (HP).

METHODS

The volume of contrast-enhanced dura mater on magnetic resonance imaging was evaluated using the imaging feature quantification system in 19 patients with immune-mediated HP, including 12 with antineutrophil cytoplasmic antibody-related, 4 with IgG4-related, and 3 with idiopathic HP, as well as 10 with multiple sclerosis (MS) as controls. The implications of HP volume on neurological manifestations and cerebrospinal fluid (CSF) laboratory markers were statistically analyzed in patients with immune-mediated HP.

RESULTS

The volumes of the contrast-enhanced dura mater in the convexity, cranial fossa, and tentorium cerebelli were significantly higher in patients with immune-mediated HP than in those with MS. Among patients with immune-mediated HP, those with cranial nerve (CN) VIII neuropathy had a significantly higher volume of the contrast-enhanced dura mater in the cranial fossa than those without CN VIII neuropathy. The volume of the contrast-enhanced dura mater in the tentorium cerebelli was positively correlated with CSF protein levels.

CONCLUSION

Quantification of the thickened dura mater is useful for elucidating the relationship with the clinical findings in immune-mediated HP. Thickened dura mater lesions in the cranial fossa may be implicated in the development of CN VIII neuropathy. The enlargement of HP lesions in the tentorium cerebelli can increase CSF protein levels.

Determining the Clinical Characteristics, Treatment Strategies, and Prognostic Factors for Mycoplasma pneumoniae Encephalitis in Children: A Multicenter Study in China

BACKGROUND AND PURPOSE

Most of the knowledge of Mycoplasma pneumonia (M. pneumoniae) encephalitis (MPE) in children is based on case reports or small case series. This study aimed to describe the clinical features and prognostic factors of MPE, and the efficacy of azithromycin with or without immunomodulatory therapy.

METHODS

The medical data of 87 patients with MPE from 3 medical centers in southwestern China over a 7-year period were reviewed.

RESULTS

MPE was found in children of all ages except for neonates. The most common neurological manifestations included consciousness disturbance (90%) and headache (87.4%), the most common extraneurological manifestations included fever (96.5%) and respiratory system involvement (94.3%); multisystem involvement (98.2%) and elevated C-reactive protein (CRP) (90.8%) were also prominent. M. pneumoniae was detected in cerebrospinal fluid (CSF) less often than in blood and respiratory tract secretions. Azithromycin with intravenous immunoglobulin or/and corticosteroid treatment can shorten the hospitalization duration and the clinical improvement process. Most patients (82.8%) received a favorable prognosis; serum lactate dehydrogenase (LDH) and CSF protein levels were higher in the poor-outcome group than in the good-outcome group (p<0.05). Neurological sequelae are likely to continue when the onset of this condition occurs during teenage years.

CONCLUSIONS

MPE generally presented with nonspecific clinical manifestations. In children with acute encephalitis accompanied by multi-system involvement and prominently elevated CRP, M. pneumoniae should be considered as a possible pathogen. Immunomodulating therapies should be recommended regardless of the duration of the prodromal period. High CSF protein level, blood LDH elevation, and higher age may be associated with an unfavorable outcome.

Viral anterior uveitis

Anterior uveitis has various causes, but the majority of cases are viral induced. The most common viral anterior uveitis etiology includes double-stranded DNA viruses of the Herpesviridae family, including Alpha herpes virinae (herpes simplex 1 and 2 and varicella zoster virus), Beta herpesvirinae (cytomegalovirus), and less frequently, Gamma herpesvirinae (Epstein-Barr virus). In the last few decades, a growing body of evidence has correlated Fuchs uveitis etiology to the rubella virus from the Matonaviridae family, which has a single-stranded RNA genome. The clinical presentation of each of these uveitis is hypertensive granulomatous anterior uveitis; however, the very slight differences between them, which often overlap, make differential diagnosis sometimes difficult. Therefore, diagnostic laboratory tests such as polymerase chain reaction and antibody index or Goldmann-Witmer coefficient analyses on the aqueous humor help to identify the etiology in doubtful cases and thus to plan targeted treatment.

Understanding the brain uptake and permeability of small molecules through the BBB: A technical overview

The brain is the most important organ in our body requiring its unique microenvironment. By the virtue of its function, the blood-brain barrier poses a significant hurdle in drug delivery for the treatment of neurological diseases. There are also different theories regarding how molecules are typically effluxed from the brain. In this review, we comprehensively discuss how the different pharmacokinetic techniques used for measuring brain uptake/permeability of small molecules have evolved with time. We also discuss the advantages and disadvantages associated with these different techniques as well as the importance to utilize the right method to properly assess CNS exposure to drug molecules. Even though very strong advances have been made we still have a long way to go to ensure a reduction in failures in central nervous system drug development programs.

An observational study investigating cytokine levels in the cerebrospinal fluid of patients with schizophrenia spectrum disorders

INTRODUCTION

The role of immunological mechanisms in the pathophysiology of mental disorders has been discussed with increasing frequency. In this context, especially schizophrenia has become the focus of attention after the discovery of autoimmune encephalitis, which might present with psychotic symptoms. Furthermore, multiple studies have identified associations between infections or autoimmune diseases and schizophreniform disorders. Cerebrospinal fluid (CSF) analysis plays a central role in identifying potential inflammatory processes in the central nervous system. Therefore, the rationale of this retrospective study was the analysis of different cytokines, including interleukin-8 (IL-8) levels, in the CSF of patients with schizophrenia spectrum disorders.

METHODS

The authors examined the CSF of 40 patients with schizophrenia spectrum disorders, in comparison to the CSF of a mentally healthy control group of 39 patients with idiopathic intracranial hypertension (IIH). Magnetic bead multiplexing immunoassay was used to retrospectively determine different cytokines in the participants' CSF.

RESULTS

Participants with schizophrenia spectrum disorders had significantly higher IL-8 levels in their CSF than controls (mean ± SD: 41.83 ± 17.50 pg/ml versus 21.40 ± 7.96 pg/ml; p < 0.001).

CONCLUSION

The main finding of this study is the presence of significantly higher IL-8 concentrations in the CSF of patients with schizophrenia spectrum disorders when compared to the control group. This supports the hypothesis that immunological processes may be involved in the pathophysiology of a subgroup of patients with schizophrenia spectrum disorders. However, the study's results are limited by the retrospective design, methodological aspects, and the control group with IIH.

Blood-cerebrospinal fluid (CSF) barrier dysfunction means reduced CSF flow not barrier leakage - conclusions from CSF protein data

BACKGROUND

Increased concentrations of serum proteins in cerebrospinal fluid (CSF) are interpreted as blood-CSF barrier dysfunction. Frequently used interpretations such as barrier leakage, disruption or breakdown contradict CSF protein data, which suggest a reduced CSF flow rate as the cause.

RESULTS

Even the severest barrier dysfunctions do not change the molecular size-dependent selectivity or the interindividual variation of the protein transfer across barriers. Serum protein concentrations in lumbar CSF increase with hyperbolic functions, but the levels of proteins that do not pass the barrier remain constant (brain proteins) or increase linearly (leptomeningal proteins). All CSF protein dynamics above and below a lumbar blockade can also be explained, independent of their barrier passage, by a reduced caudally directed flow. Local accumulation of gadolinium in multiple sclerosis (MS) is now understood as due to reduced bulk flow elimination by interstitial fluid (ISF). Nonlinear change of the steady state in barrier dysfunction and along normal rostro-caudal gradients supports the diffusion/flow model and contradicts obstructions of diffusion pathways. Regardless of the cause of the disease, pathophysiological flow blockages are found in bacterial meningitis, leukemia, meningeal carcinomatosis, Guillain-Barré syndrome, MS and experimental allergic encephalomyelitis. In humans, the fortyfold higher albumin concentrations in early fetal development decrease later with maturation of the arachnoid villi, i.e., with beginning CSF outflow, which contradicts a relevant outflow to the lymphatic system. Respiration- and heartbeat-dependent oscillations do not disturb net direction of CSF flow.

CONCLUSION

Blood-CSF and blood-brain barrier dysfunctions are an expression of reduced CSF or ISF flow rate.

Cerebrospinal Fluid Findings of 36 Adult Patients with Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder characterized by difficulties with social interaction, repetitive behavior, and additional features, such as special interests. Its precise etiology is unclear. Recently, immunological mechanisms, such as maternal autoantibodies/infections, have increasingly been the subject of discussion. Cerebrospinal fluid (CSF) investigations play a decisive role in the detection of immunological processes in the brain. This study therefore retrospectively analyzed the CSF findings of adult patients with ASD. CSF basic measures (white blood cell count, total protein, albumin quotient, immunoglobulin G (IgG) index, and oligoclonal bands) and various antineuronal antibody findings of 36 adult patients with ASD, who had received lumbar puncture, were compared with an earlier described mentally healthy control group of 39 patients with idiopathic intracranial hypertension. CSF protein concentrations and albumin quotients of patients with ASD were significantly higher as compared to controls (age corrected: p = 0.003 and p = 0.004, respectively); 17% of the patients with ASD showed increased albumin quotients. After correction for age and gender, the group effect for total protein remained significant (p = 0.041) and showed a tendency for albumin quotient (p = 0.079). In the CSF of two ASD patients, an intrathecal synthesis of anti-glutamate decarboxylase 65 (GAD65) antibodies was found. In total, more of the ASD patients (44%) presented abnormal findings in CSF basic diagnostics compared to controls (18%; p = 0.013). A subgroup of the patients with adult ASD showed indication of a blood-brain barrier dysfunction, and two patients displayed an intrathecal synthesis of anti-GAD65 antibodies; thus, the role of these antibodies in patients with ASD should be further investigated. The results of the study are limited by its retrospective and open design. The group differences in blood-brain barrier markers could be influenced by a different gender distribution between ASD patients and controls.

The B-lymphocyte chemokine CXCL13 in the cerebrospinal fluid of children with Lyme neuroborreliosis: associations with clinical and laboratory variables

Background: The B-lymphocyte chemokine CXCL13 is increasingly considered as a useful early phase diagnostic marker of Lyme neuroborreliosis (LNB). However, the large variation in level of CXCL13 in the cerebrospinal fluid (CSF) observed in LNB patients is still unexplained. We aimed to identify factors associated with the level of CXCL13 in children with LNB, possibly improving the interpretation of CXCL13 as a diagnostic marker of LNB. Methods: Children with confirmed and probable LNB were included in a prospective study on CXCL13 in CSF as a diagnostic marker of LNB. The variables age, sex, facial nerve palsy, generalized inflammation symptoms (fever, headache, neck-stiffness and/or fatigue), duration of symptoms, Borrelia antibodies in CSF, Borrelia antibody index (AI), CSF white blood cells (WBC), CSF protein and detection of the genospecies Borrelia garinii by PCR were included in simple and multivariable regression analyses to study the associations with the CXCL13 level. Results: We included 53 children with confirmed and 17 children with probable LNB. CXCL13 levels in CSF were positively associated with WBC, protein and Borrelia antibodies in CSF in both simple and multivariable analyses. We did not find any associations between CXCL13 and age, sex, clinical symptoms, duration of symptoms, AI or the detection of Borrelia garinii. Conclusions: High levels of CSF CXCL13 are present in the early phase of LNB and correlate with the level of CSF WBC and protein. Our results indicate that CSF CXCL13 in children evaluated for LNB can be interpreted independently of clinical features or duration of symptoms.

Determining the clinical characteristics and prognostic factors for the outcomes of Japanese encephalitis in adults: A multicenter study from southern Taiwan

BACKGROUND

In Southeast Asia, Japanese encephalitis (JE) is an important cause of viral encephalitis which may cause severe neurological sequelae. JE affects mostly children; therefore, clinical presentations and prognosis of adult JE patients are seldom addressed. This study aimed to describe the clinical characteristics and prognostic factors for the outcome of adult JE patients.

METHODS

Medical records of adult JE patients with acute encephalitis syndrome during 2001-2018 from five medical centers in southern Taiwan were reviewed. Clinical characteristics, brain images, and prognostic factors for outcomes were analyzed. Patients were divided into the good outcome (GO) group and poor outcome (PO) group according to their Glasgow Coma Scale (GCS) scores (GCS >8 vs. ≤ 8) at discharge.

RESULTS

Sixty-eight patients (men, 61.8%; median age, 50 years) were included. Summer is the epidemic season, and the number of cases peaked in June. The most common symptoms at initial presentation were altered consciousness and fever (both 94.1%), followed by headache (51.4%). The most commonly involved brain regions were thalamus (55.7%) and basal ganglion (37.7%). The median GCS score at nadir was 8, and the median time from onset to nadir was five days. Fifty-two patients were included in the GO group, while 16 were included in the PO group. On multivariate analysis, flaccidity, rigidity, and elevated CSF protein level were identified as independent prognostic factors for PO.

CONCLUSION

Initial clinical presentations of abnormal muscle tone including flaccidity, rigidity and high CSF protein levels are independent prognostic factors for PO in adult JE patients.

Clearance of cerebrospinal fluid from the sacral spine through lymphatic vessels

Using a tracer-based approach with near-infrared fluorescence and magnetic resonance imaging in mice, the authors establish the concept of a cranial-to-caudal circulation of cerebrospinal fluid within the spinal column, with clearance to lymphatic vessels at the sacral terminus.

The pathways of circulation and clearance of cerebrospinal fluid (CSF) in the spine have yet to be elucidated. We have recently shown with dynamic in vivo imaging that routes of outflow of CSF in mice occur along cranial nerves to extracranial lymphatic vessels. Here, we use near-infrared and magnetic resonance imaging to demonstrate the flow of CSF tracers within the spinal column and reveal the major spinal pathways for outflow to lymphatic vessels in mice. We found that after intraventricular injection, a spread of CSF tracers occurs within both the central canal and the spinal subarachnoid space toward the caudal end of the spine. Outflow of CSF tracers from the spinal subarachnoid space occurred predominantly from intravertebral regions of the sacral spine to lymphatic vessels, leading to sacral and iliac LNs. Clearance of CSF from the spine to lymphatic vessels may have significance for many conditions, including multiple sclerosis and spinal cord injury.

[Pathological changes in human brain biopsies from patients with idiopathic normal pressure hydrocephalus]

AIM

To analyze specific changes in brain tissue of patients with idiopathic normal pressure hydrocephalus at cellular and subcellular levels.

MATERIAL AND METHODS

Brain biopsies from 32 patients with idiopathic normal pressure hydrocephalus were investigated by light and electron microscopy. Biopsies were made in 3 points (the cortex, subcortical and periventricular white matter during ventricular catheter positioning).

RESULTS

A number of pathological features of idiopathic normal pressure hydrocephalus were identified. Most frequent were the exhaustion of brain tissue, enlargement of perivascular spaces, aseptic necrosis, and amyloid and Lewy body's formation.

CONCLUSION

The changes in brain tissue of patients with idiopathic normal pressure hydrocephalus transform our views on its mechanisms. It becomes clear that idiopathic normal pressure hydrocephalus is part of common neurodegenerative process that has characteristic features affecting clinical manifestations of the disease.

Elimination of substances from the brain parenchyma: efflux via perivascular pathways and via the blood-brain barrier

This review considers efflux of substances from brain parenchyma quantified as values of clearances (CL, stated in µL g-1 min-1). Total clearance of a substance is the sum of clearance values for all available routes including perivascular pathways and the blood-brain barrier. Perivascular efflux contributes to the clearance of all water-soluble substances. Substances leaving via the perivascular routes may enter cerebrospinal fluid (CSF) or lymph. These routes are also involved in entry to the parenchyma from CSF. However, evidence demonstrating net fluid flow inwards along arteries and then outwards along veins (the glymphatic hypothesis) is still lacking. CLperivascular, that via perivascular routes, has been measured by following the fate of exogenously applied labelled tracer amounts of sucrose, inulin or serum albumin, which are not metabolized or eliminated across the blood-brain barrier. With these substances values of total CL ≅ 1 have been measured. Substances that are eliminated at least partly by other routes, i.e. across the blood-brain barrier, have higher total CL values. Substances crossing the blood-brain barrier may do so by passive, non-specific means with CLblood-brain barrier values ranging from < 0.01 for inulin to > 1000 for water and CO2. CLblood-brain barrier values for many small solutes are predictable from their oil/water partition and molecular weight. Transporters specific for glucose, lactate and many polar substrates facilitate efflux across the blood-brain barrier producing CLblood-brain barrier values > 50. The principal route for movement of Na+ and Cl- ions across the blood-brain barrier is probably paracellular through tight junctions between the brain endothelial cells producing CLblood-brain barrier values ~ 1. There are large fluxes of amino acids into and out of the brain across the blood-brain barrier but only small net fluxes have been observed suggesting substantial reuse of essential amino acids and α-ketoacids within the brain. Amyloid-β efflux, which is measurably faster than efflux of inulin, is primarily across the blood-brain barrier. Amyloid-β also leaves the brain parenchyma via perivascular efflux and this may be important as the route by which amyloid-β reaches arterial walls resulting in cerebral amyloid angiopathy.

Progress in brain barriers and brain fluid research in 2017

The past year, 2017, has seen many important papers published in the fields covered by Fluids and Barriers of the CNS. This article from the Editors highlights some.