CSF pathways: a review

The Role of Circulating Tight Junction Proteins in Evaluating Blood Brain Barrier Disruption following Intracranial Hemorrhage

Brain injury after intracranial hemorrhage (ICH) results in significant morbidity and mortality. Blood brain barrier (BBB) disruption is a hallmark of ICH-induced brain injury; however, data mirroring BBB disruption in human ICH are scarce. The aim of this study was to assess the significance of circulating biomarkers in evaluating BBB disruption after ICH. Twenty-two patients with ICH were recruited in this study. Concentrations of the tight junction proteins (TJs) Claudin-5 (CLDN5), Occludin (OCLN), and zonula occludens 1 (ZO-1) and vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) were measured by using enzyme-linked immunosorbent assay in serum and cerebrospinal fluid (CSF) samples obtained from patients with ICH. The white blood cell (WBC) count in blood and CSF, albumin (ALB) levels in the CSF (ALBCSF), and the BBB ratio were significantly higher in the ICH than in controls (p < 0.05). Significantly higher levels of CLDN5, OCLN, ZO-1, MMP-9, and VEGF in CSF were observed in the ICH group; these biomarkers were also positively associated with BBB ratio (p < 0.05). Our data revealed that circulating TJs could be considered the potential biomarkers reflecting the integrity of the BBB in ICH.

Cerebrospinal fluid proteomics in multiple sclerosis

Multiple sclerosis (MS) is an immune mediated chronic inflammatory disease of the central nervous system usually initiated during young adulthood, affecting approximately 2.5 million people worldwide. There is currently no cure for MS, but disease modifying treatment has become increasingly more effective, especially when started in the first phase of the disease. The disease course and prognosis are often unpredictable and it can be challenging to determine an early diagnosis. The detection of novel biomarkers to understand more of the disease mechanism, facilitate early diagnosis, predict disease progression, and find treatment targets would be very attractive. Over the last decade there has been an increasing effort toward finding such biomarker candidates. One promising strategy has been to use state-of-the-art quantitative proteomics approaches to compare the cerebrospinal fluid (CSF) proteome between MS and control patients or between different subgroups of MS. In this review we summarize and discuss the status of CSF proteomics in MS, including the latest findings with a focus on the last five years. This article is part of a Special Issue entitled: Neuroproteomics: Applications in Neuroscience and Neurology.

The chaperone protein clusterin may serve as a cerebrospinal fluid biomarker for chronic spinal cord disorders in the dog

Chronic spinal cord dysfunction occurs in dogs as a consequence of diverse aetiologies, including long-standing spinal cord compression and insidious neurodegenerative conditions. One such neurodegenerative condition is canine degenerative myelopathy (DM), which clinically is a challenge to differentiate from other chronic spinal cord conditions. Although the clinical diagnosis of DM can be strengthened by the identification of the Sod1 mutations that are observed in affected dogs, genetic analysis alone is insufficient to provide a definitive diagnosis. There is a requirement to identify biomarkers that can differentiate conditions with a similar clinical presentation, thus facilitating patient diagnostic and management strategies. A comparison of the cerebrospinal fluid (CSF) protein gel electrophoresis profile between idiopathic epilepsy (IE) and DM identified a protein band that was more prominent in DM. This band was subsequently found to contain a multifunctional protein clusterin (apolipoprotein J) that is protective against endoplasmic reticulum (ER) stress-mediated apoptosis, oxidative stress, and also serves as an extracellular chaperone influencing protein aggregation. Western blot analysis of CSF clusterin confirmed elevated levels in DM compared to IE (p < 0.05). Analysis of spinal cord tissue from DM and control material found that clusterin expression was evident in neurons and that the clusterin mRNA levels from tissue extracts were elevated in DM compared to the control. The plasma clusterin levels was comparable between these groups. However, a comparison of clusterin CSF levels in a number of neurological conditions found that clusterin was elevated in both DM and chronic intervertebral disc disease (cIVDD) but not in meningoencephalitis and IE. These findings indicate that clusterin may potentially serve as a marker for chronic spinal cord disease in the dog; however, additional markers are required to differentiate DM from a concurrent condition such as cIVDD.

Miniaturized passive hydrogel check valve for hydrocephalus treatment

Improvements in cerebrospinal fluid (CSF) draining techniques for treatment of hydrocephalus are urgently sought after to substitute for current CSF shunts that are plagued by high failure rates. The passive check valve aims to restore near natural CSF draining operations while mitigating possible failure mechanisms caused by finite leakage or low resilience that frequently constrain practical implementation of miniaturized valves. A simple hydrogel diaphragm structures core passive valve operations and enforce valve sealing properties to substantially lower reverse flow leakage. Experimental measurements demonstrate realization of targeted cracking pressures (PT ≈ 20-110 mmH2O) and operation at -800 <; ΔP <; 600 mmH2O without observable degradation or leakage.

Successful treatment of negative pressure hydrocephalus using timely titrated external ventricular drainage: a case series

OBJECTIVE

Negative-pressure hydrocephalus (NegPH) is a rare clinical entity characterised by enlarged ventricles and symptoms consistent with increased intracranial pressure (ICP) in the setting of negative ICP. Little has been published regarding appropriate treatment and outcomes of negative-pressure hydrocephalus patients, and no data have been published demonstrating successful therapy producing acceptable long-term outcomes. Here we present 8 cases successfully treated by titrated external ventricular drainage (TEVD), including drainage at negative (subatmospheric) pressure, and subsequent low-pressure ventriculoperitoneal shunting.

METHODS

A retrospective audit of all cases of negative-pressure hydrocephalus occurring at a university teaching hospital between 2006 and 2012 was undertaken. The clinical features of these cases, results of radiological investigations, treatment, and outcome were drawn from the patients' records.

RESULTS

Eight cases of NegPH were identified. All patients had at least one preceding intracranial procedure (mean number of procedures 3.0). All cases were treated using TEVD, titrated to produce between 5 and 15 mL per hour of CSF drainage, including drainage under subatmospheric pressure if this was required to maintain CSF flow. Mean delay from first negative ICP to TEVD was 1.8 days. All 8 patients demonstrated clinical improvement. TEVD resulted in improvement in Glasgow Coma Scale (mean increase 4.6, p=0.003), and increases in ICP (mean increase 8.5, p<0.001). Mean length of follow-up was 471.8 days. At follow-up, four patients had returned to pre-morbid functioning, three had a reduction in functioning attributable to their initial presentation (not NegPH), and one had died of unknown cause. Illustrative case descriptions are included.

CONCLUSIONS

Negative-pressure hydrocephalus is a rare but underrecognised syndrome that can be successfully treated by timely external ventricular drainage titrated to maintain CSF flow, and subsequent low-pressure ventriculoperitoneal shunting.

Dynamic quantitative intravital imaging of glioblastoma progression reveals a lack of correlation between tumor growth and blood vessel density

The spatiotemporal and longitudinal monitoring of cellular processes occurring in tumors is critical for oncological research. We focused on glioblastoma multiforme (GBM), an untreatable highly vascularized brain tumor whose progression is thought to critically depend on the oxygen and metabolites supplied by blood vessels. We optimized protocols for orthotopic GBM grafting in mice that were able to recapitulate the biophysical constraints normally governing tumor progression and were suitable for intravital multiphoton microscopy. We repeatedly imaged tumor cells and blood vessels during GBM development. We established methods for quantitative correlative analyses of dynamic imaging data over wide fields in order to cover the entire tumor. We searched whether correlations existed between blood vessel density, tumor cell density and proliferation in control tumors. Extensive vascular remodeling and the formation of new vessels accompanied U87 tumor cell growth, but no strong correlation was found between local cell density and the extent of local blood vessel density irrespective of the tumor area or time points. The technique moreover proves useful for comparative analysis of mice subjected either to Bevacizumab anti-angiogenic treatment that targets VEGF or to AMD3100, an antagonist of CXCR4 receptor. Bevacizumab treatment massively reduced tumoral vessel densities but only transiently reduced U87 tumor growth rate. Again, there was no correlation between local blood vessel density and local cell density. Moreover, Bev applied only prior to tumor implantation inhibited tumor growth to the same extent as post-grafting treatment. AMD3100 achieved a potent inhibition of tumor growth without significant reduction in blood vessel density. These results indicate that in the brain, in this model, tumor growth can be sustained without an increase in blood vessel density and suggest that GBM growth is rather governed by stromal properties.

"Compensated hyperosmolarity" of cerebrospinal fluid and the development of hydrocephalus

Acute osmolar loading of cerebrospinal fluid within one lateral ventricle of dogs was examined as a cause of water extraction from the bloodstream and an increase in intracranial pressure. We have shown that a certain amount of (3)H₂O from the bloodstream enters osmotically loaded cerebrospinal fluid significantly faster, hence causing a significant increase in intracranial pressure. The noted phenomenon in which intracranial pressure still significantly increases, but in which the hyperosmolarity of the cerebrospinal fluid is no longer present, was named "compensated hyperosmolarity". In the case of the sub-chronic application of hyperosmolar solutions into cat ventricles, we observed an increase in cerebrospinal fluid volume and a more pronounced development of hydrocephalus in the area of application, but without significant increase in intracranial pressure and without blockage of cerebrospinal fluid pathways. These results support the newly proposed hypothesis of cerebrospinal fluid hydrodynamics and the ability to develop new strategies for the treatment of cerebrospinal fluid-related diseases.

The relationship between localized subarachnoid inflammation and parenchymal pathophysiology after spinal cord injury

Subarachnoid inflammation following spinal cord injury (SCI) can lead to the formation of localized subarachnoid scarring and the development of post-traumatic syringomyelia (PTS). While PTS is a devastating complication of SCI, its relative rarity (occurring symptomatically in about 5% of clinical cases), and lack of fundamental physiological insights, have led us to examine an animal model of traumatic SCI with induced arachnoiditis. We hypothesized that arachnoiditis associated with SCI would potentiate early parenchymal pathophysiology. To test this theory, we examined early spatial pathophysiology in four groups: (1) sham (non-injured controls), (2) arachnoiditis (intrathecal injection of kaolin), (3) SCI (35-g clip contusion/compression injury), and (4) PTS (intrathecal kaolin+SCI). Overall, there was greater parenchymal inflammation and scarring in the PTS group relative to the SCI group. This was demonstrated by significant increases in cytokine (IL-1α and IL-1β) and chemokine (MCP-1, GRO/KC, and MIP-1α) production, MPO activity, blood-spinal cord barrier (BSCB) permeability, and MMP-9 activity. However, parenchymal inflammatory mediator production (acute IL-1α and IL-1β, subacute chemokines), BSCB permeability, and fibrous scarring in the PTS group were larger than the sum of the SCI group and arachnoiditis group combined, suggesting that arachnoiditis does indeed potentiate parenchymal pathophysiology. Accordingly, these findings suggest that the development of arachnoiditis associated with SCI can lead to an exacerbation of the parenchymal injury, potentially impacting the outcome of this devastating condition.

Reassessing cerebrospinal fluid (CSF) hydrodynamics: a literature review presenting a novel hypothesis for CSF physiology

The traditional model of cerebrospinal fluid (CSF) hydrodynamics is being increasingly challenged in view of recent scientific evidences. The established model presumes that CSF is primarily produced in the choroid plexuses (CP), then flows from the ventricles to the subarachnoid spaces, and is mainly reabsorbed into arachnoid villi (AV). This model is seemingly based on faulty research and misinterpretations. This literature review presents numerous evidence for a new hypothesis of CSF physiology, namely, CSF is produced and reabsorbed throughout the entire CSF-Interstitial fluid (IF) functional unit. IF and CSF are mainly formed and reabsorbed across the walls of CNS blood capillaries. CP, AV and lymphatics become minor sites for CSF hydrodynamics. The lymphatics may play a more significant role in CSF absorption when CSF-IF pressure increases. The consequences of this complete reformulation of CSF hydrodynamics may influence applications in research, publications, including osteopathic manual treatments.

[Post-dural puncture headache and blood-patch: theoretical and practical approach]

OBJECTIVE

To review the current research and formulate a rational approach to the physiopathology, cause and treatment of post-dural puncture headache (PDPH).

DATA SOURCES

Articles published to December 2011 were obtained through a search of Medline for the MeSh terms "epidural blood-patch" and "post-dural puncture headache".

STUDY SELECTION

Six hundred and eighty-two pertinent studies were included and 200 were analysed.

DATA SYNTHESIS

Resulting of a dural tap after spinal anaesthesia or diagnostic lumbar puncture or as a complication of epidural anaesthesia, PDPH occurs when an excessive leak of cerebrospinal fluid leads to intracranial hypotension associated to a resultant cerebral vasodilatation. Reduction in cerebrospinal fluid volume in upright position may cause traction of the intracranial structure and stretching of vessels. Typically postural, headache may be associated to nausea, photophobia, tinnitus or arm pain and changes in hearing acuity. In severe cases, there may be cranial nerve dysfunction and nerve palsies secondary to traction on those nerves. The Epidural Blood-Patch (EBP) is considered as the "gold standard" in the treatment of PDHP because it induces a prolonged elevation of subarachnoid and epidural pressures, whereas such elevation is transient with saline or dextran. EBP should be performed within 24-48hours of onset of headache; the optimum volume of epidural blood appears to be 15-20mL. Severe complications following EBP are exceptional. The use of echography may be safety puncture. The optimum timing of epidural blood-patch, the resort of repeating procedure if the symptomatology does not disappear, the alternative to the conventional medical treatment need to be determined by future clinical trial.

Microglia and a functional type I IFN pathway are required to counter HSV-1-driven brain lateral ventricle enlargement and encephalitis

HSV-1 is the leading cause of sporadic viral encephalitis, with mortality rates approaching 30% despite treatment with the antiviral drug of choice, acyclovir. Permanent neurologic deficits are common in patients that survive, but the mechanism leading to this pathology is poorly understood, impeding clinical advancements in treatment to reduce CNS morbidity. Using magnetic resonance imaging and type I IFN receptor-deficient mouse chimeras, we demonstrate HSV-1 gains access to the murine brain stem and subsequently brain ependymal cells, leading to enlargement of the cerebral lateral ventricle and infection of the brain parenchyma. A similar enlargement in the lateral ventricles is found in a subpopulation of herpes simplex encephalitic patients. Associated with encephalitis is an increase in CXCL1 and CXCL10 levels in the cerebral spinal fluid, TNF-α expression in the ependymal region, and the influx of neutrophils of encephalitic mouse brains. Reduction in lateral ventricle enlargement using anti-secretory factor peptide 16 reduces mortality significantly in HSV-1-infected mice without any effect on expression of inflammatory mediators, infiltration of leukocytes, or changes in viral titer. Microglial cells but not infiltrating leukocytes or other resident glial cells or neurons are the principal source of resistance in the CNS during the first 5 d postinfection through a Toll/IL-1R domain-containing adapter inducing IFN-β-dependent, type I IFN pathway. Our results implicate lateral ventricle enlargement as a major cause of mortality in mice and speculate such an event transpires in a subpopulation of human HSV encephalitic patients.

Syrinx fluid transport: modeling pressure-wave-induced flux across the spinal pial membrane

Syrinxes are fluid-filled cavities of the spinal cord that characterize syringomyelia, a disease involving neurological damage. Their formation and expansion is poorly understood, which has hindered successful treatment. Syrinx cavities are hydraulically connected with the spinal subarachnoid space (SSS) enveloping the spinal cord via the cord interstitium and the network of perivascular spaces (PVSs), which surround blood vessels penetrating the pial membrane that is adherent to the cord surface. Since the spinal canal supports pressure wave propagation, it has been hypothesized that wave-induced fluid exchange across the pial membrane may play a role in syrinx filling. To investigate this conjecture a pair of one-dimensional (1-d) analytical models were developed from classical elastic tube theory coupled with Darcy's law for either perivascular or interstitial flow. The results show that transpial flux serves as a mechanism for damping pressure waves by alleviating hoop stress in the pial membrane. The timescale ratio over which viscous and inertial forces compete was explicitly determined, which predicts that dilated PVS, SSS flow obstructions, and a stiffer and thicker pial membrane-all associated with syringomyelia-will increase transpial flux and retard wave travel. It was also revealed that the propagation of a pressure wave is aided by a less-permeable pial membrane and, in contrast, by a more-permeable spinal cord. This is the first modeling of the spinal canal to include both pressure-wave propagation along the spinal axis and a pathway for fluid to enter and leave the cord, which provides an analytical foundation from which to approach the full poroelastic problem.

Increased CSF osmolarity reversibly induces hydrocephalus in the normal rat brain

BACKGROUND

Hydrocephalus is a central nervous system (CNS) disorder characterized by the abnormal accumulation of cerebrospinal fluid (CSF) in cerebral ventricles, resulting in their dilatation and associated brain tissue injury. The pathogenesis of hydrocephalus remains unclear; however, recent reports suggest the possible involvement of abnormal osmotic gradients. Here we explore the kinetics associated with manipulating CSF osmolarity on ventricle volume (VV) in the normal rat brain.

METHODS

CSF was made hyper-osmotic by introducing 10KD dextran into the lateral ventricle, either by acute injection at different concentrations or by chronic infusion at a single concentration. The induction and withdrawal kinetics of dextran infusion on VV were explored in both contexts.

RESULTS

Acute intraventricular injection of dextran caused a rapid increase in VV which completely reversed within 24 hours. These kinetics are seemingly independent of CSF osmolarity across a range spanning an order of magnitude; however, the magnitude of the transient increase in VV was proportional to CSF osmolarity. By contrast, continuous intraventricular infusion of dextran at a relatively low concentration caused a more gradual increase in VV which was very slow to reverse when infusion was suspended after five days.

CONCLUSION

We conclude that hyperosmolar CSF is sufficient to produce a proportional degree of hydrocephalus in the normal rat brain, and that this phenomenon exhibits hysteresis if CSF hyperosmolarity is persistent. Thus pathologically-induced increases in CSF osmolarity may be similarly associated with certain forms of clinical hydrocephalus. An improved understanding of this phenomenon and its kinetics may facilitate the development of novel therapies for the treatment of clinical hydrocephalus.

The effects of intrathecal injection of a hyaluronan-based hydrogel on inflammation, scarring and neurobehavioural outcomes in a rat model of severe spinal cord injury associated with arachnoiditis

Traumatic spinal cord injury (SCI) comprises a heterogeneous condition caused by a complex array of mechanical forces that damage the spinal cord - making each case somewhat unique. In addition to parenchymal injury, a subset of patients experience severe inflammation in the subarachnoid space or arachnoiditis, which can lead to the development of fluid-filled cavities/syringes, a condition called post-traumatic syringomyelia (PTS). Currently, there are no therapeutic means to address this devastating complication in patients and furthermore once PTS is diagnosed, treatment is often prone to failure. We hypothesized that reducing subarachnoid inflammation using a novel bioengineered strategy would improve outcome in a rodent model of PTS. A hydrogel of hyaluronan and methyl cellulose (HAMC) was injected into the subarachnoid space 24 h post PTS injury in rats. Intrathecal injection of HAMC reduced the extent of fibrosis and inflammation in the subarachnoid space. Furthermore, HAMC promoted improved neurobehavioural recovery, enhanced axonal conduction and reduced the extent of the lesion as assessed by MRI and histomorphometric assessment. These findings were additionally associated with a reduction in the post-traumatic parenchymal fibrous scar formation as evidenced by reduced CSPG deposition and reduced IL-1α cytokine levels. Our data suggest that HAMC is capable of modulating inflammation and scarring events, leading to improved functional recovery following severe SCI associated with arachnoiditis.

Cerebrospinal fluid BACE1 activity and brain amyloid load in Alzheimer's disease

The secretase BACE1 is fundamentally involved in the development of cerebral amyloid pathology in Alzheimer's disease (AD). It has not been studied so far to what extent BACE1 activity in cerebrospinal fluid (CSF) mirrors in vivo amyloid load in AD. We explored associations between CSF BACE1 activity and fibrillar amyloid pathology as measured by carbon-11-labelled Pittsburgh Compound B positron emission tomography ([¹¹C]PIB PET). [¹¹C]PIB and CSF studies were performed in 31 patients with AD. Voxel-based linear regression analysis revealed significant associations between CSF BACE1 activity and [¹¹C]PIB tracer uptake in the bilateral parahippocampal region, the thalamus, and the pons. Our study provides evidence for a brain region-specific correlation between CSF BACE1 activity and in-vivo fibrillar amyloid pathology in AD. Associations were found in areas close to the brain ventricles, which may have important implications for the use of BACE1 in CSF as a marker for AD pathology and for antiamyloid treatment monitoring.

Dependence of cerebrospinal fluid pressure and volume on the changes in serum osmolarity in cats

OBJECTIVES

To study the effect of blood osmolarity on cerebrospinal fluid (CSF) volume and CSF pressure in cats.

METHODS

Three types of methods were used on anesthetized cats. The first, ventriculo-cisternal perfusion (12.96 μL/min) before and after i.v. application of 20% mannitol; the second, measuring the outflow of CSF by cisternal free drainage; and the third, measuring CSF pressure in the ventricles of an intact CSF system, with the second and third method being performed before and after the i.p. application of a hypo-osmolar substance (distilled water).

RESULTS

In the first group, the application of 20% mannitol led to a significantly reduced (p < 0.005) outflow volume (from 12.60 ± 0.29 to 0.94 ± 0.09 μL/min). In the second group, the outflow CSF volume significantly increased (p < 0.001) after the application of distilled water (from 18.8 ± 0.3 to 28.2 ± 0.7 μL/min). In the third group, after the application of distilled water, the CSF pressure also significantly increased (p < 0.05; from 8.3 ± 0.8 to 16.1 ± 0.14 cm H(2)O).

CONCLUSION

We conclude that changes in serum osmolarity change the CSF volume because of the osmotic gradient between the blood and all of the CSF compartments, and also that the change in CSF pressure is closely associated with changes in CSF volume.

Amelioration of caudal thoracic syringohydromyelia following surgical management of an adjacent arachnoid cyst

A nine-year-old male, neutered, pug was presented for investigation of progressive ambulatory paraparesis and pelvic limb ataxia of three months' duration. Magnetic resonance imaging was suggestive of caudal thoracic syringohydromyelia with an adjacent intradural arachnoid cyst. The cyst was marsupialised following dorsal laminectomy. Neurological status had improved 10 weeks following surgery when repeat magnetic resonance imaging revealed reduced spinal cord compression both as a result of resolution of the cyst and reduction in size of the syringohydromyelia. At 17 months following surgery, the dog showed further improvements in neurological status, exhibiting mild pelvic limb ataxia and proprioceptive deficits. Improved cerebrospinal fluid flow following surgery may have played a role in the improvement in both conditions. The presence of syringohydromyelia in this context does not preclude a favourable clinical outcome following surgical management.

Development of hydrocephalus and classical hypothesis of cerebrospinal fluid hydrodynamics: facts and illusions

According to the classical hypothesis of the cerebrospinal fluid (CSF) hydrodynamics, CSF is produced inside the brain ventricles, than it circulates like a slow river toward the cortical subarachnoid space, and finally it is absorbed into the venous sinuses. Some pathological conditions, primarily hydrocephalus, have also been interpreted based on this hypothesis. The development of hydrocephalus is explained as an imbalance between CSF formation and absorption, where more CSF is formed than is absorbed, which results in an abnormal increase in the CSF volume inside the cranial CSF spaces. It is believed that the reason for the imbalance is the obstruction of the CSF pathways between the site of CSF formation and the site of its absorption, which diminishes or prevents CSF outflow from the cranium. In spite of the general acceptance of the classical hypothesis, there are a considerable number of experimental results that do not support such a hypothesis and the generally accepted pathophysiology of hydrocephalus. A recently proposed new working hypothesis suggests that osmotic and hydrostatic forces at the central nervous system microvessels are crucial for the regulation of interstial fluid and CSF volume which constitute a functional unit. Based on that hypothesis, the generally accepted mechanisms of hydrocephalus development are not plausible. Therefore, the recent understanding of the correlation between CSF physiology and the development of hydrocephalus has been thoroughly presented, analyzed and evaluated, and new insights into hydrocephalus etiopathology have been proposed, which are in accordance with the experimental data and the new working hypothesis.

Symptomatic increased intracranial pressure due to arachnoid cysts

Intracranial arachnoid cysts are typically benign lesions, but rarely, they may cause signs and symptoms relating to increased intracranial pressure. We report 4 pediatric patients with arachnoid cysts who received successful surgical treatment after failing to respond to conservative medical therapies. After undergoing a shunting procedure, each patient experienced improvement in symptoms, resolution of optic disc swelling, and reduction or elimination of medications necessary to manage the condition. These cases illustrate the potential for arachnoid cysts to outstrip compensatory mechanisms and cause signs and symptoms requiring definitive surgical intervention.

A lumped-parameter model of the cerebrospinal system for investigating arterial-driven flow in posttraumatic syringomyelia

Fluid transport in syringomyelia has remained enigmatic ever since the disease was first identified some three centuries ago. However, accumulating evidence in the last decade from animal studies implicates arterial pulsations in syrinx formation. In particular, it has been suggested that a phase difference between the pressure pulse in the spinal subarachnoid space and the perivascular spaces, due to a pathologically disturbed cerebrospinal fluid (CSF) or blood supply, could result in a net influx of CSF into the spinal cord (SC). A lumped-parameter model is developed of the cerebrospinal system to investigate this conjecture. It is found that although this phase-lag mechanism may operate, it requires the SC to have an intrinsic storage capacity due to the collapsibility of the contained venous reservoir. This net flux is associated with a higher mean pressure in the SC than the SSS which is maintained in the periodic steady state. According to our simulations the mechanical perturbations of arachnoiditis exacerbate the phase-lag effect, which may be partially alleviated by the presence of a posttraumatic syrinx and more completely by a syringo-subarachnoid shunt.

The expression of twisted gastrulation in postnatal mouse brain and functional implications

Twisted gastrulation (TWSG1), an extracellular regulator of bone morphogenetic protein (BMP) signaling, is critical for embryonic brain development. Mice deficient in TWSG1 have abnormal forebrain development manifesting as holoprosencephaly. The expression and potential roles of TWSG1 in postnatal brain development are less well understood. We show that Twsg1 is expressed in the adult mouse brain in the choroid plexus (CP), hippocampus, and other regions, with the strongest expression observed in CP. TWSG1 was also detected in a human fetal brain at mid-gestation, with highest levels in the epithelium of CP. Bmp1, Bmp2, Bmp4-Bmp7 as well as BmprIA and BmprII, but not BmprIB, were expressed in CP. BMP antagonists Chordin (Chrd) and Noggin were not detected in CP, however Chrd-like 1 and brain-specific Chrd-like (Brorin) were expressed. Electrophysiological study of synaptic plasticity revealed normal paired-pulse facilitation and long-term potentiation in the CA1 region of hippocampus in Twsg1(-/-) mice. Among the homozygous mutants that survive beyond the first 2 weeks, the prevalence of hydrocephalus was 4.3%, compared to 1.5% in a wild type colony (P=0.0133) between 3 and 10 weeks of life. We detected a high level of BMP signaling in CP in wild type adult mice that was 17-fold higher than in the hippocampus (P=0.005). In contrast, transforming growth factor beta (TGFbeta) signaling was predominant in the hippocampus. Both BMP signaling and the expression of BMP downstream targets Msx1 and Msx2 were reduced in CP in Twsg1(-/-) mice. In summary, we show that Twsg1 is expressed in the adult mouse and human fetal CP. We also show that BMP is a branch of TGFbeta superfamily that is dominant in CP. This presents an interesting avenue for future research in light of the novel roles of CP in neural progenitor differentiation and neuronal repair, especially since TWSG1 appears to be the main regulator of BMP present in CP.

Evaluation by Fluid/Structure-Interaction Spinal-Cord Simulation of the Effects of Subarachnoid-Space Stenosis on an Adjacent Syrinx

A finite-element numerical model was constructed of the spinal cord, pia mater, filum terminale, cerebrospinal fluid in the spinal subarachnoid space (SSS), and dura mater. The cord was hollowed out by a thoracic syrinx of length 140 mm, and the SSS included a stenosis of length 30 mm opposite this syrinx. The stenosis severity was varied from 0% to 90% by area. Pressure pulse excitation was applied to the model either at the cranial end of the SSS, simulating the effect of cranial arterial pulsation, or externally to the abdominal dura mater, simulating the effect of cough. A very short pulse was used to examine wave propagation; a pulse emulating cardiac systole was used to examine the effects of fluid displacement. Additionally, repetitive sinusoidal excitation was applied cranially. Bulk fluid flow past the stenosis gave rise to prominent longitudinal pressure dissociation (“suck”) in the SSS adjacent to the syrinx. However, this did not proportionally increase the longitudinal motion of fluid in the syrinx. The inertia of the fluid in the SSS, together with the compliance of this space, gave a resonance capable of being excited constructively or destructively by cardiac or coughing impulses. The main effect of mild stenosis was to lower the frequency of this resonance; severe stenosis damped out to-and-fro motions after the end of the applied excitation. Syrinx fluid motion indicated the fluid momentum and thus the pressure developed when the fluid was stopped by the end of the syrinx; however, the tearing stress in the local cord material depended also on the instantaneous local SSS pressure and was therefore not well predicted by syrinx fluid motion. Stenosis was also shown to give rise to a one-way valve effect causing raised SSS pressure caudally and slight average cord displacement cranially. The investigation showed that previous qualitative predictions of the effects of suck neglected factors that reduced the extent of the resulting syrinx fluid motion and of the cord tearing stress, which ultimately determines whether the syrinx lengthens.

Detection of Meningeosis neoplastica by real-time quantitation of telomerase activity

BACKGROUND

Analysis of cerebrospinal fluid (CSF) to discriminate between benign and malignant conditions is of fundamental importance for the physician and the patient because of the differential therapeutic options and resulting morbidity and mortality. Most human tumours demonstrate increased telomerase activity (TA). Recent technical advances in the detection of TA allow for sensitive and specific detection within 4 h. Thus, the detection of TA is suitable for routine clinical testing.

METHODS

This study examines TA in cellular proteins in CSF from 111 patients compared to cytomorphological and laboratory examination.

RESULTS

A positive result for TA in cellular proteins of CSF was correlated significantly with Meningeosis neoplastica, but not with non-malignant conditions. Telomerase was not detected in CSF supernatant, despite positive results in cellular proteins from identical patients. Furthermore, a 48-h time delay during the pre-analytic processing is not critical for detection of TA detection in native CSF when stored at room temperature.

CONCLUSIONS

We conclude that TA is a promising marker for the detection of Meningeosis neoplastica and warrants further study.

Spinal arteriovenous malformation associated with syringomyelia

The authors describe 4 cases of syringomyelia-associated spinal cord arteriovenous malformation (AVM). All cases were managed with embolization of the AVM. Treatments were aimed to stabilize the AVM itself and not directed toward the syrinx. In 3 of the 4 cases the syringomyelia resolved after treatment. Reports concerning AVM as a cause of syringomyelia is very scarce and lacks posttreatment clinical information. In light of the clinical course and imaging findings, the authors propose a theory that venous hypertension in the spinal cord is the trigger for the development of syringomyelia, which may reverse after AVM treatment.

Hydrocephalus caused by a venous varix

INTRODUCTION

Vascular malformations are uncommon causes of aqueductal obstruction. To our concern, only one case of hydrocephalus caused by a venous varix draining an unruptured arteriovenous malformation has been described in the literature.

CASE REPORT

We report the case of a 70-year-old woman presenting with progressive cognitive impairment, gait disturbance and urinary incontinence. Magnetic resonance imaging and magnetic resonance angiography revealed a large venous varix draining an unruptured arteriovenous malformation causing hydrocephalus.

CONCLUSION

Although uncommon, it is necessary to consider the presence of a vascular malformation in adults who presented with signs of aqueductal obstruction.

Anatomy and development of the meninges: implications for subdural collections and CSF circulation

The dura is traditionally viewed as a supportive fibrous covering of the brain containing the dural venous sinuses but otherwise devoid of vessels and lacking any specific function. However, review of the embryology and anatomy reveals the dura to be a complex, vascularized and innervated structure, not a simple fibrous covering. The dura contains an inner vascular plexus that is larger in the infant than in the adult, and this plexus likely plays a role in CSF absorption. This role could be particularly important in the infant whose arachnoid granulations are not completely developed. Although subdural hemorrhage is frequently traumatic, there are nontraumatic conditions associated with subdural hemorrhage, and the inner dural plexus is a likely source of bleeding in these nontraumatic circumstances. This review outlines the development and age-specific vascularity of the dura and offers an alternative perspective on the role of the dura in homeostasis of the central nervous system.

Monitoring the amyloid beta-peptide in vivo--caveat emptor

As a wave of 'disease modifying' (DM) therapies for Alzheimer's disease (AD) progresses towards the later stages of clinical development, an evaluation of our ability to measure relevant pharmacodynamic effects of such therapies is warranted. Reducing accumulation of amyloid beta (Abeta)-peptide in the brain parenchyma is the primary objective of most current DM approaches. Although a number of methods are available to measure Abeta in blood, cerebrospinal fluid (CSF) and the cerebrum, putative DM-induced changes in the levels of the peptides may not be fully captured, and the reasons for any such changes are not fully understood. Additional candidate biofluid (tau and isoprostanes) and imaging (MRI, FDG-PET) measures may provide alternative supporting evidence of drug activity and subsequent clinical efficacy in patient populations.

Evidence for reduced lymphatic CSF absorption in the H-Tx rat hydrocephalus model

Background

There is mounting evidence that spinal fluid absorption takes place not only at the arachnoid villi, but also at several extracranial sites, which might serve as a reserve mechanism for, or be primarily involved in the absorption of CSF in hydrocephalus.

Methods

We compared the nasal lymphatic pathway in congenital Hydrocephalus-Texas (H-Tx) rats in unaffected and affected hydrocephalic (HC) siblings with that of control Sprague Dawley (SD) rat pups. The animals were examined after immediate post mortem injection of Evan's blue dye into the cisterna magna at 6 and 10 days of age. The specimens were evaluated for amount of dye penetration into the nasal passages.

Results

We found more dye visualization in the olfactory regions of control SD (14/16 at P6, 14/16 at P10) and unaffected H-Tx (13/17 at P6, 13/16 at P10) compared with HC animals (0/14 at P6, 3/15 at P10). This difference was more pronounced at 10 days of age. The dye was not visualized in the cervical lymph nodes or venous channels in these acute experiments.

Conclusion

The results of this study suggest that nasal lymphatic cerebrospinal fluid absorption is reduced in the H-Tx rat hydrocephalus model.

The peptide AF-16 abolishes sickness and death at experimental encephalitis by reducing increase of intracranial pressure

Elevated intracranial pressure (ICP) is strongly aggravating the injury at brain inflammation, resulting in persistent neurological and psychiatric malfunctions. There is no efficient pharmacological treatment to achieve beneficial ICP reduction. Here, the peptide AF-16, comprising the amino terminal part of the endogenous protein Antisecretory Factor (AF), was used to suppress the raised ICP in experimental herpes simplex encephalitis (HSE) in rats. Intranasal instillation of the peptide AF-16 counteracted the ICP elevation and the prevalence of ICP spikes, abrogated the neurological morbidity, and abolished the mortality in a dose-dependent manner. AF-16, 25 microg twice daily intranasally, rescued all animals with HSE and abrogated neurological malfunction. In contrast, only 10% of the rats survived if treated with the vehicle. A single intranasal dose of 25 microg AF-16 to a rat displaying overt HSE symptoms reduced the ICP to normal levels within an hour. No effects on viral replication or antigen distribution were demonstrable. Thus, AF-16 abolished the prevalence of sickness signs, ICP elevation, neurological malfunctions and completely prevented deaths. We advocate use of AF-16 for suppression of elevated ICP.