Idiopathic cerebrospinal fluid overproduction: case-based review of the pathophysiological mechanism implied in the cerebrospinal fluid production

Risk factors and disease associations in people living with idiopathic intracranial hypertension

INTRODUCTION

Idiopathic intracranial hypertension is a neurological condition characterized by a raised intracranial pressure and papilledema, leading to chronic headaches and visual disturbances. By recognizing modifiable risk factors and deploying evidence-based interventions, healthcare providers have the potential to mitigate the burden of the disease and improve patient outcomes.

AREAS COVERED

It is well known that the condition occurs in predominantly pre-menopausal females who live with obesity particularly in the context of recent weight gain. This review discusses what risk factors may contribute to the metabolic underpinnings of cerebrospinal fluid dysregulation. There are a number of disease associations that are important to screen for as they can alter management.

EXPERT OPINION

There is emerging evidence to suggest that idiopathic intracranial hypertension is a systemic metabolic disease and it is unknown what are all the risk factors are that precipitate the condition. Targeting certain hardwired risk factors is unachievable. However, as recent weight gain has been identified as a predominant risk factor for the development of the disease and relapse, modification of body weight should be the primary aim of management. Insightful research into the involvement of the neuroendocrine axis driving cerebrospinal fluid dysregulation now has the potential for the development of therapeutic targets.

Patient-specific automated cerebrospinal fluid pressure control to augment spinal wound closure: a case series using the LiquoGuard®

OBJECTIVE

Spinal cerebrospinal fluid (CSF) leaks are common, and their management is heterogeneous. For high-flow leaks, numerous studies advocate for primary dural repair and CSF diversion. The LiquoGuard7® allows automated and precise pressure and volume control, and calculation of patient-specific CSF production rate (prCSF), which is hypothesized to be increased in the context of durotomies and CSF leaks.

METHODS

This single-centre illustrative case series included patients undergoing complex spinal surgery where: 1) a high flow intra-operative and/or post-operative CSF leak was expected and 2) lumbar CSF drainage was performed using a LiquoGuard7®. CSF diversion was tailored to prCSF for each patient, combined with layered spinal wound closure.

RESULTS

Three patients were included, with a variety of pathologies: T7/T8 disc prolapse, T8-T9 meningioma, and T4-T5 metastatic spinal cord compression. The first two patients underwent CSF diversion to prevent post-op CSF leak, whilst the third required this in response to post-op CSF leak. CSF hyperproduction was evident in all cases (mean >/=140ml/hr). With patient-specific CSF diversion regimes, no cases required further intervention for CSF fistulae repair (including for pleural CSF effusion), wound breakdown or infection.

CONCLUSIONS

Patient-specific cerebrospinal fluid drainage may be a useful tool in the management of high-flow intra-operative and post-operative CSF leaks during complex spinal surgery. These systems may reduce post-operative CSF leakage from the wound or into adjacent body cavities. Further larger studies are needed to evaluate the comparative benefits and cost-effectiveness of this approach.

Cerebrospinal fluid production rate in various pathological conditions: a preliminary study

INTRODUCTION

The cerebrospinal fluid (CSF) production rate in humans is not clearly defined but is estimated to be 18-24 ml/h (Trevisi et al Croat Med J 55(4):377-387 (24); Casey and Vries Childs Nerv Syst 5(5):332-334 (8)). A frequent clinical observation is that patients often drain higher volumes of CSF than can be explained by the assumed 'normal' CSF production rate (PRcsf). In the National Hospital for Neurology and Neurosurgery PRcsf was recorded in a variety of common neurosurgical pathologies using LiquoGuard7, an automated peristaltic pump that accurately controls CSF drainage and maintains a pre-set CSF pressure.

METHODS

A prospective observational study was performed from September 2021 onwards, on all patients in the National Hospital for Neurology and Neurosurgery who required CSF drainage as part of their ongoing treatment. The external drain was connected to a LiquoGuard7 pump (Möller Medical GmbH, Fulda, Germany), and the internal software of LiquoGuard7 was used to measure PRcsf. Statistical analysis used SPSS (version 25.0, IBM) by paired t test, comparing measured rates to hypothetical 'normal' CSF production rates calculated and published by Ekstedt (16-34ml/h) (Ekstedt J Neurol Neurosurg Psychiatry 41(4):345-353 (14)), assuming a similar distribution.

RESULTS

PRcsf was calculated in 164 patients. Suspected normal pressure hydrocephalus (n=41): PRcsf of 79ml/h±20SD (p<0.0001). Post-surgical CSF leak (n=26): PRcsf of 90ml/h±20SD (p<0.0001). Subarachnoid haemorrhage (n=34): PRcsf of 143ml/h±9SD (p<0.0001). Intracerebral haemorrhage (n=22): PRcsf of 137ml/h±20SD (p<0.0001). Spinal lesions (n=7): PRcsf of 130ml/h±20SD (p<0.0032). Pituitary adenomas (n=10): PRcsf of 29 ml/h±9SD (p<0.049). Idiopathic intracranial hypertension (n=15): PRcsf of 86ml/h±10SD (p<0.0001). Decompensated long-standing overt ventriculomegaly (n=4): PRcsf of 65ml/h±10SD (p<0.0001). Cerebral infection (n=5): PRcsf of 90ml/h±20SD (p<0.0001).

CONCLUSION

Net CSF production rate may be higher than expected in many conditions, as measured with new device LiquoGuard7 through the study of net flow rate, which may have implications for clinical decisions on CSF diversion. The conventional understanding of CSF production and circulation does not explain the findings of this study. More extensive studies are needed to validate this technique.

Cerebrospinal Fluid-Basic Concepts Review

Cerebrospinal fluid plays a crucial role in protecting the central nervous system (CNS) by providing mechanical support, acting as a shock absorber, and transporting nutrients and waste products. It is produced in the ventricles of the brain and circulates through the brain and spinal cord in a continuous flow. In the current review, we presented basic concepts related to cerebrospinal fluid history, cerebrospinal fluid production, circulation, and its main components, the role of the blood-brain barrier and the blood-cerebrospinal fluid barrier in the maintenance of cerebrospinal fluid homeostasis, and the utility of Albumin Quotient (Q_Alb) evaluation in the diagnosis of CNS diseases. We also discussed the collection of cerebrospinal fluid (type, number of tubes, and volume), time of transport to the laboratory, and storage conditions. Finally, we briefly presented the role of cerebrospinal fluid examination in CNS disease diagnosis of various etiologies and highlighted that research on identifying cerebrospinal fluid biomarkers indicating disease presence or severity, evaluating treatment effectiveness, and enabling understanding of pathogenesis and disease mechanisms is of great importance. Thus, in our opinion, research on cerebrospinal fluid is still necessary for both the improvement of CNS disease management and the discovery of new treatment options.

Comparison Between Ventricular and Spinal Infusion Tests in Suspected Normal Pressure Hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is an often-overlooked or misdiagnosed brain disorder characterized by overt ventriculomegaly and associated with gait disturbances, cognitive impairment, and urinary incontinence. If correctly diagnosed, it is considered the only form of dementia treatable with surgery, namely through a ventriculoperitoneal or ventriculoatrial shunt with programmable valves.Among the 856 spinal and ventricular infusion tests performed from 2001 to 2017 at our institution, we analyzed 106 cases selected for suspected normotensive hydrocephalus. In all cases, Intracranial Elastance Index (IEI) and outflow resistance (Rout) values were calculated: 52 of these patients underwent Spinal Katzman Test (SKT), and the remaining 54 underwent an intraventricular infusion test (IVKT). Of the 40 patients in the SKT group with pathological elastance (71%), 17 also had a Rout >12 mmHg and 23 a Rout <12 mmHg. Of the 50 patients in the IVKT group with pathological elastance (92%), 38 also had a Rout >12 mmHg and 12 a Rout <12 mmHg.IVKT and SKT to date represent two useful tools in the diagnosis of normal pressure hydrocephalus. Despite being more invasive, IVKT, including both the intracranial elastance index (IEI) and Rout analysis, could be considered more reliable than SKT and therefore could be reserved for the most controversial cases.

Deconstructing the functional neuroanatomy of the choroid plexus: an ontogenetic perspective for studying neurodevelopmental and neuropsychiatric disorders

The choroid plexus (CP) is a delicate and highly vascularized structure in the brain comprised of a dense network of fenestrated capillary loops that help in the synthesis, secretion and circulation of cerebrospinal fluid (CSF). This unique neuroanatomical structure is comprised of arachnoid villi stemming from frond-like surface projections-that protrude into the lumen of the four cerebral ventricles-providing a key source of nutrients to the brain parenchyma in addition to serving as a 'sink' for central nervous system metabolic waste. In fact, the functions of the CP are often described as being analogous to those of the liver and kidney. Beyond forming a barrier/interface between the blood and CSF compartments, the CP has been identified as a modulator of leukocyte trafficking, inflammation, cognition, circadian rhythm and the gut brain-axis. In recent years, advances in molecular biology techniques and neuroimaging along with the use of sophisticated animal models have played an integral role in shaping our understanding of how the CP-CSF system changes in relation to the maturation of neural circuits during critical periods of brain development. In this article we provide an ontogenetic perspective of the CP and review the experimental evidence implicating this structure in the pathophysiology of neurodevelopmental and neuropsychiatric disorders.

Elevated CSF inflammatory markers in patients with idiopathic normal pressure hydrocephalus do not promote NKCC1 hyperactivity in rat choroid plexus

BACKGROUND

Idiopathic normal pressure hydrocephalus (iNPH) is a potentially reversible neurological condition of unresolved etiology characterized by a clinical triad of symptoms; gait disturbances, urinary incontinence, and cognitive deterioration. In the present study, we aimed to elucidate the molecular coupling between inflammatory markers and development of iNPH and determine whether inflammation-induced hyperactivity of the choroidal Na⁺/K⁺/2Cl^- cotransporter (NKCC1) that is involved in cerebrospinal fluid (CSF) secretion could contribute to the iNPH pathogenesis.

METHODS

Lumbar CSF samples from 20 iNPH patients (10 with clinical improvement upon CSF shunting, 10 without clinical improvement) and 20 elderly control subjects were analyzed with the novel proximity extension assay technique for presence of 92 different inflammatory markers. RNA-sequencing was employed to delineate choroidal abundance of the receptors for the inflammatory markers found elevated in the CSF from iNPH patients. The ability of the elevated inflammatory markers to modulate choroidal NKCC1 activity was determined by addition of combinations of rat version of these in ex vivo experiments on rat choroid plexus.

RESULTS

11 inflammatory markers were significantly elevated in the CSF from iNPH patients compared to elderly control subjects: CCL28, CCL23, CCL3, OPG, CXCL1, IL-18, IL-8, OSM, 4E-BP1, CXCL6, and Flt3L. One inflammatory marker, CDCP1, was significantly decreased in iNPH patients compared to control subjects. None of the inflammatory markers differed significantly when comparing iNPH patients with and without clinical improvement upon CSF shunting. All receptors for the elevated inflammatory markers were expressed in the rat and human choroid plexus, except CCR4 and CXCR1, which were absent from the rat choroid plexus. None of the elevated inflammatory markers found in the CSF from iNPH patients modulated the choroidal NKCC1 activity in ex vivo experiments on rat choroid plexus.

CONCLUSION

The CSF from iNPH patients contains elevated levels of a subset of inflammatory markers. Although the corresponding inflammatory receptors are, in general, expressed in the choroid plexus of rats and humans, their activation did not modulate the NKCC1-mediated fraction of choroidal CSF secretion ex vivo. The molecular mechanisms underlying ventriculomegaly in iNPH, and the possible connection to inflammation, therefore remains to be elucidated.

Craniosynostosis and hydrocephalus: relevance and treatment modalities

INTRODUCTION

Hydrocephalus is variously associated to syndromic craniosynostosis (CS), while it is randomly encountered in monosutural CS. Pathogenesis is still debated and reliable criteria for the diagnosis of overt hydrocephalus are lacking. Additionally, optimal treatment is controversial since it should balance the need to relieve intracranial hypertension and the risk of recurrence favored by lowering intracranial pressure.

METHODS

A thorough review of the literature has been performed. Accordingly, pathogenic theories, diagnostic issues, and treatment options on hydrocephalus presenting in the context of CS are discussed.

RESULTS

The association of hydrocephalus to simple CS is considered a fortuitous event. Its treatment is usually driven by the etiology and clinical relevance of hydrocephalus, favoring treatment before surgical correction to reduce CSF-related complications. On the other side, pathogenesis of hydrocephalus in the context of syndromic CS has been mainly related to factors that are secondary to the synostostic process, such as craniocerebral disproportion and venous hypertension. Hydrocephalus complicates 12-15% of syndromic CS, though its incidence is more relevant in FGFR2-related CS and raises up to 88% in Pfeiffer syndrome. Overt hydrocephalus should be properly differentiated by non-tense ventriculomegaly that is more frequent in Apert syndrome. Since intracranial hypertension is constant in syndromic CS even in the absence of active hydrocephalus, radiological monitoring of ventricular size along with intracranial pressure monitoring is essential. Active hydrocephalus occurs more frequently in infants, though stable ventriculomegaly may evolve into overt hydrocephalus after cranial expansion. If hydrocephalus is not clinically prominent, cranial expansion should be favored as first surgical step. Although posterior cranial expansion may address posterior cranial fossa constriction and stabilize ventricular dilation, effectiveness in long-term control of hydrocephalus is not clear. ETV is an effective treatment option, though success rate is affected by the presence of brain malformations and patient age. Extrathecal CSF shunting should be used as last resource due to the increased risk of complications in this context.

CONCLUSIONS

The pathogenesis of hydrocephalus complicating syndromic CS should be further investigated. Concomitantly, the definition of reliable diagnostic criteria is advocated in order to promptly and properly identify active hydrocephalus. Finally, treatment algorithm should refine the best timing and treatment options aiming to relieve intracranial hypertension on one side and reduce the risk of restenosis on the other side.

Transcranial ultrasonography as a reliable instrument for the measurement of the cerebral ventricles in rats with experimental hydrocephalus: a pilot study

PURPOSES

Demonstrate that transcranial ultrasonography (TUS) scanning is viable and useful as a diagnostic method in experimental hydrocephalus, as well as to compare measurements of cerebral and ventricular width obtained from TUS scans of hydrocephalic rats with post-mortem anatomical specimens, aiming for the development of accurate criteria to establish ventricular enlargement and progression of hydrocephalus subsequently.

METHODS

Thirty-five male Wistar rats were used. Following hydrocephalus induction, they underwent a transcranial ultrasound scan to measure cerebral and ventricular dimensions, in the fourth and 21 post-induction days. By the end of the experiments, measurements obtained from TUS scans were compared with actual values as seen in the post-mortem specimens of each animal.

RESULTS

Ventricular dilation could be clearly visualized in hydrocephalic animals. We performed intraclass correlation coefficient and linear regression analyses that have demonstrated a precise correlation between measurements of TUS scans and post-mortem specimens; we have found a similarity of 0,95 for the cerebral diameter and 0,97 for ventricular width.

CONCLUSIONS

Transcranial ultrasonography is a useful and reliable diagnostic tool for experimental hydrocephalus; also, it can be used to assess the progression of ventriculomegaly in animal models of hydrocephalus.

Strengths and weaknesses of frontal versus occipital ventriculoperitoneal shunt placement: A systematic review

Excessive accumulation of cerebrospinal fluid within the brain ventricles is called hydrocephalus, which results in increased intracranial pressure preventing brain growth or causing damage to intracranial structures due to raised intracranial pressure. One of the most common treatment options for this pathology includes the placement of a ventriculoperitoneal shunt to drain the excess fluid. The location of catheterization is traditionally considered as an important factor affecting shunt survival. In this study, we aimed to systematically review all available documents to determine the advantage and superiority of frontal or occipital shunt entry points as the two main approaches. A database search was performed in PubMed, Scopus, Embase, Web of Science, Medline, Ovid, and Google Scholar using "ventriculoperitoneal", "shunt placement", and "hydrocephalus" as the main key terms. Resultant articles were screened for relevancy based on predefined inclusion and exclusion criteria by two authors independently. After excluding irrelevant documents, the data of 11 related articles consisting of 3947 patients were extracted and qualitative data synthesis and pooled analysis were performed. The results of the included studies showed that although the outcomes of a higher percentage of the total review population were in favor of frontal shunt placement, there was no significant superiority for neither of these two approaches after pooled analysis of available failure rates. Findings have shown that each approach has benefits and drawbacks, and there may be other factors such as age and valve design besides the position of shunt placement that may affect the survival rate. Also, the accuracy of shunt placement as an independent factor affects the failure rate and can be improved with various image-guidance methods to minimize shunt failure.

Ventriculoperitoneal Shunt-Associated Ascites: A Case Report

A ventriculoperitoneal shunt is a commonly performed procedure that is used to relieve the increased intracranial pressure in patients with hydrocephalus. VP shunt placement is an invasive procedure and carries many complications. Besides common complications like infections or mechanical obstruction, VP shunt has been found to be associated with the development of ascites in some patients. VP shunt-associated ascites is a very rare complication and only a few cases have been reported in the literature, most of which were in the pediatric population, while adult VP shunt-associated ascites was even rarer.

The patient in this case is a 32-year-old female who presented with ascites of unclear etiology. She had a history of VP shunt placement shortly after birth due to central nervous system (CNS) malformation (agenesis of the corpus callosum). Liver pathology, infection, and malignancy were ruled out as potential causes, and ascites was determined to be due to VP shunt drainage.

The exact mechanism of development of ascites in these patients is not fully understood and needs to be investigated further to optimize preventative and therapeutic options.

Complex Management of Hydrocephalus Secondary To Choroid Plexus Hyperplasia

BACKGROUND

Hyperplasia of the choroid plexus represents a rare cause of communicating hydrocephalus in children. Recent work has associated such disease with genetic abnormalities (such as perturbations in chromosome 9). Given such extensive cerebrospinal fluid (CSF) overproduction, patients with choroid plexus hyperplasia often fail CSF diversion and therefore require adjuvant interventions.

CASE DESCRIPTION

We present the case of a male infant with a ventriculoperitoneal shunt and radiographic choroid hyperplasia who presented to our institution with a massive abdominal hydrocele caused by an inability to absorb the significant amount of CSF drainage into the abdomen.

CONCLUSION

The child was treated with an endoscopic third ventriculostomy and choroid plexus coagulation; however, he still required CSF diversion via a ventriculoatrial shunt. A genetic workup showed tetraploidy of chromosome 9. We discuss criteria for selection of treatment strategies, including endoscopic third ventriculostomy with choroid plexus coagulation and/or CSF diversion, that may prevent the need for re-operation in select patients with hydrocephalus due to choroid plexus hyperplasia.

Familial Intracranial Hypertension in 2 Brothers With PTEN Mutation: Expansion of the Phenotypic Spectrum

PTEN (Phosphatase and Tensin Homolog on chromosome TEN) encodes a vastly expressed tumor suppressor protein that antagonizes the PI3 K signaling pathway and alters the MTOR pathway. Mutations in PTEN have been described in association with a number of syndromes including PTEN hamartoma-tumor syndrome, macrocephaly/autism, and juvenile polyposis of infancy. Although there is a wide variability in the clinical and radiologic presentations of PTEN-related phenotypes, the most consistent features include macrocephaly and increased tumorigenesis. Intracranial hypertension may be idiopathic or secondary to multiple etiologies. We describe 2 siblings harboring a PTEN mutation who presented with macrocephaly and intracranial hypertension. Repeat brain MRIs were normal in both. Acetazolamide treatment normalized intracranial pressure, but several trials of medication tapering led to recurrence of intracranial hypertension symptoms. The clinical presentation of our patients expands the PTEN-related phenotypes. We discuss the possible pathophysiology in view of PTEN function.

An Electrical Model of Hydrocephalus Shunt Incorporating the CSF Dynamics

The accumulation of cerebrospinal fluid (CSF) in brain ventricles and subarachnoid space is known as hydrocephalus. Hydrocephalus is a result of disturbances in the secretion or absorption process of CSF. A hydrocephalus shunt is an effective method for the treatment of hydrocephalus. In this paper, at first, the procedures of secretion, circulation, and absorption of CSF are studied and subsequently, the mathematical relations governing the pressures in different interacting compartments of the brain are considered. A mechanical-electrical model is suggested based on the brain physiology and blood circulation. In the proposed model, hydrocephalus is modeled with an incremental resistance (Ro) and hydrocephalus shunt, which is a low resistance path to drain the accumulated CSF in the brain ventricles, is modeled with a resistance in series with a diode. At the end, the simulation results are shown. The simulation results can be used to predict the shunt efficiency in reducing CSF pressure and before a real shunt implementation surgery is carried out in a patient's body.

Choroidal artery embolization in the management of cerebrospinal fluid overproduction: case report and review of the literature

Diffuse villous hyperplasia of the choroid plexus (DVHCP) is a rare cause of communicating hydrocephalus. DVHCP may be diagnosed radiographically and through histological evaluation. It may be associated with genetic abnormalities, particularly involving chromosome 9. Due to CSF overproduction, patients with DVHCP often fail management with shunting alone and may require adjuvant interventions. The authors present the case of a child with partial trisomy 9p and delayed diagnosis of hydrocephalus with radiographic evidence of DVHCP who was successfully managed with ventriculoperitoneal shunt (VPS) placement, adjuvant bilateral endoscopic choroid plexus coagulation (CPC), and the novel application of anterior choroidal artery embolization. In addition, a systematic MEDLINE search was conducted using the keywords "diffuse villous hyperplasia," "choroid plexus hypertrophy," and "idiopathic cerebrospinal fluid overproduction." Clinicopathological characteristics and outcomes of the present case were reviewed and compared to those in the literature.A 14-month-old girl with partial trisomy 9p presented with macrocephaly and radiographic evidence of communicating hydrocephalus and DVHCP. Ventriculoperitoneal shunting resulted in distal failure due to inadequate CSF absorption, and ventriculoatrial shunt (VAS) placement was not possible due to multiple cardiac anomalies. Daily CSF production was reduced via endoscopic third ventriculostomy and bilateral CPC, followed by distal choroidal artery embolization, enabling VPS re-internalization. The embolization was complicated by radiographic evidence of an iatrogenic cerebral infarct, but this was clinically occult. Thirty-two additional cases of communicating hydrocephalus due to DVHCP are reported in the literature: 27 pediatric, 3 adult, and 2 postmortem. Genetic abnormalities were noted in 14, with 7 (50%) involving chromosome 9. Twelve patients underwent plexectomy (9 bilateral, 2 unilateral, 1 partial), and 10 underwent CPC (4 bilateral, 3 unilateral, and 3 unspecified), with or without shunting. Eight patients were successfully managed with shunting alone (6 VASs, 2 VPSs), and none underwent arterial embolization.DVHCP is a rare cause of communicating hydrocephalus that may be associated with genetic abnormalities. A thorough review of the literature highlights diagnostic criteria and interventional options involved in managing this cause of CSF overproduction. The present case demonstrates that angiographic confirmation of prominent choroidal arteries may contribute to the diagnosis DVHCP. In addition, embolization of the distal choroidal arteries may be considered as a potential adjuvant treatment in patients for whom conventional treatments have failed or are not feasible.

Thinking outside the shunt-sterile CSF malabsorption in pilocytic astrocytomas: case series and review of the literature

INTRODUCTION

Ventriculoperitoneal (VP) shunt insertion is the most common cerebrospinal fluid (CSF) diversionary procedure used for the treatment of chronic hydrocephalus. Sterile CSF ascites is a rare complication of VP shunt insertion. This can arise from either an overproduction of CSF or inadequate filtration of CSF at the level of the peritoneum. By either mechanism, the development of CSF ascites requires an intact VP shunt.

OBJECTIVE

The authors discuss two paediatric cases diagnosed with suprasellar pilocytic astrocytomas treated with platinum-based chemotherapy, who subsequently developed sterile CSF ascites. We review the literature with regard to CSF malabsorption and discuss it as a contributing factor to shunt malfunction.

CONCLUSION

CSF malabsorption with resultant ascites is a rare complication of VP shunting with many etiologies. Two common predisposing factors included the use of platinum-based chemotherapeutic agents, as well as the specific neuropathology. Further analysis of these two entities is needed in order to elucidate their role in contributing to the development of CSF ascites in this patient cohort.

Experimental Spinal Stenosis in Cats: New Insight in Mechanisms of Hydrocephalus Development

In our new experimental model of cervical stenosis without inflammation we have tested hypothesis that cranio-spinal communication impairment could lead to hydrocephalus development. Spinal and cranial cerebrospinal fluid (CSF) space separation was obtained with positioning of plastic semiring in epidural space at C2 level in cats. Brain ventricles planimetry, and CSF pressure recording in lateral ventricle (LV) and lumbar subarachnoid space (LSS) were performed in acute and subchronic experiments. In all experiments opening CSF pressures were normal. However, in acute experiments, an infusion of artificial CSF into the LV led to increase of CSF pressure and significant gradient pressure development between LV and LSS due to limited pressure transmission. After 3 or 6 weeks spinal cord atrophy was observed at the site of cervical stenosis, and pressure transmission from LV to LSS was improved as a consequence of spinal tissue atrophy. Planimetry of both the coronal brain slices and the ventricles' surface showed that control ventricular surface was 0.6 ± 0.1% (n = 5), and 1.6 ± 0.2% (n = 4) in animals with subchronic cervical stenosis (P < 0.002). These results support the mentioned hypothesis claiming that CSF volume cranio-spinal displacement impairment could start pathophysiological processes leading to development of hydrocephalus.