Low-pressure hydrocephalic state and viscoelastic alterations in the brain

Machine learning in prenatal MRI predicts postnatal ventricular abnormalities in fetuses with isolated ventriculomegaly

OBJECTIVES

To evaluate the intracranial structures and brain parenchyma radiomics surrounding the occipital horn of the lateral ventricle in normal fetuses (NFs) and fetuses with ventriculomegaly (FVs), as well as to predict postnatally enlarged lateral ventricle alterations in FVs.

METHODS

Between January 2014 and August 2023, 141 NFs and 101 FVs underwent 1.5 T balanced steady-state free precession (BSSFP), including 68 FVs with resolved lateral ventricles (FVM-resolved) and 33 FVs with stable lateral ventricles (FVM-stable). Demographic data and intracranial structures were analyzed. To predict the enlarged ventricle alterations of FVs postnatally, logistic regression models with 5-fold cross-validation were developed based on lateral ventricle morphology, blended-cortical or/and subcortical radiomics characteristics. Validation of the models' performance was conducted using the receiver operating characteristic curve (ROC), calibration curve, and decision curve analysis (DCA).

RESULTS

Significant alterations in cerebral structures were observed between NFs and FVs (p < 0.05), excluding the maximum frontal horn diameter (FD). However, there was no notable distinction between the FVM-resolved and FVM-stable groups (all p > 0.05). Based on subcortical-radiomics on the aberrant sides of FVs, this approach exhibited high efficacy in distinguishing NFs from FVs in the training/validation set, yielding an impressive AUC of 1/0.992. With an AUC value of 0.822/0.743 in the training/validation set, the Subcortical-radiomics model demonstrated its ability to predict lateral ventricle alterations in FVs, which had the greatest predictive advantages indicated by DCA.

CONCLUSIONS

Microstructural alterations in subcortical parenchyma associated with ventriculomegaly can serve as predictive indicators for postnatal lateral ventricle variations in FVs.

CLINICAL RELEVANCE STATEMENT

It is critical to gain pertinent information from a solitary fetal MRI to anticipate postnatal lateral ventricle alterations in fetuses with ventriculomegaly. This approach holds the potential to diminish the necessity for recurrent prenatal ultrasound or MRI examinations.

KEY POINTS

Fetal ventriculomegaly is a dynamic condition that affects postnatal neurodevelopment. Machine learning and subcortical-radiomics can predict postnatal alterations in the lateral ventricle. Machine learning, applied to single-fetal MRI, might reduce required antenatal testing.

Biomechanical instability of the brain-CSF interface in hydrocephalus

Hydrocephalus, characterized by progressive expansion of the CSF-filled ventricles (ventriculomegaly), is the most common reason for brain surgery. 'Communicating' (i.e. non-obstructive) hydrocephalus is classically attributed to a primary derangement in CSF homeostasis, such as choroid plexus-dependent CSF hypersecretion, impaired cilia-mediated CSF flow currents, or decreased CSF reabsorption via the arachnoid granulations or other pathways. Emerging data suggest that abnormal biomechanical properties of the brain parenchyma are an under-appreciated driver of ventriculomegaly in multiple forms of communicating hydrocephalus across the lifespan. We discuss recent evidence from human and animal studies that suggests impaired neurodevelopment in congenital hydrocephalus, neurodegeneration in elderly normal pressure hydrocephalus and, in all age groups, inflammation-related neural injury in post-infectious and post-haemorrhagic hydrocephalus, can result in loss of stiffness and viscoelasticity of the brain parenchyma. Abnormal brain biomechanics create barrier alterations at the brain-CSF interface that pathologically facilitates secondary enlargement of the ventricles, even at normal or low intracranial pressures. This 'brain-centric' paradigm has implications for the diagnosis, treatment and study of hydrocephalus from womb to tomb.

Low-/Negative-Pressure Hydrocephalus: To Understand the Formation Mechanism from the Perspective of Clinicians

Low-/negative-pressure hydrocephalus (LPH/NePH) is uncommon in clinical practice, and doctors are unfamiliar with it. LPH/NePH is frequently caused by other central nervous system diseases, and patients are frequently misdiagnosed with other types of hydrocephalus, resulting in delayed treatment. LPH/NePH therapy evolved to therapeutic measures based on "external ventricular drainage below atmospheric pressure" as the number of patients with LPH/NePH described in the literature has increased. However, the mechanism of LPH/NePH formation is unknown. Thus, understanding the process of LPH/NePH development is the most important step in improving diagnosis and treatment capability. Based on case reports of LPH/NePH, we reviewed theories of transcortical pressure difference, excessive cerebral venous drainage, brain viscoelastic changes, and porous elastic sponges.

Pathogenesis and management of low-pressure hydrocephalus: A narrative review

Patients diagnosed with low-pressure hydrocephalus typically present with enlarged ventricles and unusually low intracranial pressure, often measuring below 5 cmH2O or even below atmospheric pressure. This atypical presentation often leads to low recognition and diagnostic rates. The development of low-pressure hydrocephalus is believed to be associated with a decrease in the viscoelasticity of brain tissue or separation between the ventricular and subarachnoid spaces. Risk factors for low-pressure hydrocephalus include subarachnoid hemorrhage, aqueduct stenosis, prior cranial radiotherapy， ventricular shunting, and cerebrospinal fluid leaks. For potential low-pressure hydrocephalus, diagnostic criteria include neurological symptoms related to hydrocephalus, an Evans index >0.3 on imaging, ICP ≤ 5 cm H2O, symptom improvement with negative pressure drainage, and exclusion of ventriculomegaly caused by neurodegenerative diseases. The pathogenesis and pathophysiological features of low-pressure hydrocephalus differ significantly from other types of hydrocephalus, making it challenging to restore normal ventricular morphology through conventional drainage methods. The primary treatment options for low-pressure hydrocephalus involve negative pressure drainage and third ventriculostomy. With appropriate treatment, most patients can regain their previous neurological function. However, in most cases, permanent shunt surgery is still necessary. Low-pressure hydrocephalus is a rare condition with a high rate of underdiagnosis and mortality. Early identification and appropriate intervention are crucial in reducing complications and improving prognosis.

Cytotoxic Lesions of the Corpus Callosum Associated with Aneurysmal Subarachnoid Hemorrhage May Influence Shunt-Dependent Chronic Hydrocephalus

BACKGROUND

Cytotoxic lesions of the corpus callosum (CLOCCs) are occasionally associated with aneurysmal subarachnoid hemorrhage (aSAH). The effects of aSAH on clinical outcomes in such cases are unclear. The present study aimed to investigate the frequency and characteristics of CLOCCs associated with aSAH to ascertain the predictors of shunt-dependent chronic hydrocephalus (SDCH) after aSAH.

METHODS

We retrospectively investigated cases of aSAH treated by coil embolization. Patients were divided into those with and without CLOCCs. Between-group differences were evaluated, including clinical outcomes and the characteristics of both the patients and the aneurysms. Patients were divided into those with and without SDCH to identify predictive factors of SDCH after aSAH focusing on CLOCCs.

RESULTS

This single-center study included 196 patients with aSAH. All patients received coil embolization between April 2013 and March 2020. CLOCCs were detected in 38 (19.4%) patients. In the group with CLOCCs, male sex, poor severity grade at onset, acute hydrocephalus, SDCH (all P < 0.01), and Fisher group 3 or 4 (P = 0.04) were significantly more common than in the group without CLOCCs. Diabetes and CLOCCs were significant predictors of SDCH after aSAH in multivariate analysis (diabetes: P < 0.01, odds ratio: 6.73, 95% confidence interval: 1.61-28.09; CLOCCs: P < 0.01, odds ratio: 6.86, 95% confidence interval: 2.87-16.38).

CONCLUSIONS

CLOCCs and SDCH were common in patients with poor-grade aSAH, and CLOCCs were independent predictors of SDCH after aSAH. Meticulous follow-up is necessary to detect SDCH after aSAH, especially in patients with poor-grade aSAH and CLOCCs.

The "microcephalic hydrocephalus" paradox as a paradigm of altered neural stem cell biology

Characterized by enlarged brain ventricles, hydrocephalus is a common neurological disorder classically attributed to a primary defect in cerebrospinal fluid (CSF) homeostasis. Microcephaly ("small head") and hydrocephalus are typically viewed as two mutually exclusive phenomenon, since hydrocephalus is thought of as a fluid "plumbing" disorder leading to CSF accumulation, ventricular dilatation, and resultant macrocephaly. However, some cases of hydrocephalus can be associated with microcephaly. Recent work in the genomics of congenital hydrocephalus (CH) and an improved understanding of the tropism of certain viruses such as Zika and cytomegalovirus are beginning to shed light into the paradox "microcephalic hydrocephalus" by defining prenatal neural stem cells (NSC) as the spatiotemporal "scene of the crime." In some forms of CH and viral brain infections, impaired fetal NSC proliferation leads to decreased neurogenesis, cortical hypoplasia and impaired biomechanical interactions at the CSF-brain interface that collectively engender ventriculomegaly despite an overall and often striking decrease in head circumference. The coexistence of microcephaly and hydrocephalus suggests that these two phenotypes may overlap more than previously appreciated. Continued study of both conditions may be unexpectedly fertile ground for providing new insights into human NSC biology and our understanding of neurodevelopmental disorders.

Clinical application of magnetic resonance elastography in pediatric neurological disorders

Magnetic resonance elastography is a relatively new, rapidly evolving quantitative magnetic resonance imaging technique which can be used for mapping the viscoelastic mechanical properties of soft tissues. MR elastography measurements are akin to manual palpation but with the advantages of both being quantitative and being useful for regions which are not available for palpation, such as the human brain. MR elastography is noninvasive, well tolerated, and complements standard radiological and histopathological studies by providing in vivo measurements that reflect tissue microstructural integrity. While brain MR elastography studies in adults are becoming frequent, published studies on the utility of MR elastography in children are sparse. In this review, we have summarized the major scientific principles and recent clinical applications of brain MR elastography in diagnostic neuroscience and discuss avenues for impact in assessing the pediatric brain.

"Floppy brain" in congenital hydrocephalus

Hydrocephalus is classically considered to be a disorder of altered cerebrospinal fluid (CSF) circulation, leading to the dilation of cerebral ventricles. Here, we report a clinical case of a patient who presented with fetal-onset hydrocephalus with diffusely reduced cortical and white matter volumes resulting from a genetic mutation in L1CAM, a well-known hydrocephalus disease gene involved in neuronal cell adhesion and axon development. After CSF was drained from the ventricle intraoperatively, the patient's cortical mantle collapsed and exhibited a "floppy" appearance on neuroimaging, suggesting an inability of the hydrocephalic brain to maintain its structural integrity. The case provides clinical support for altered brain biomechanical properties in human hydrocephalus and adds to the emerging hypothesis that altered brain development with secondary impact on brain structural stability may contribute to ventricular enlargement in some subsets of hydrocephalus.

Low- and Negative-Pressure Hydrocephalus: New Report of Six Cases and Literature Review

Low- or very-low-pressure hydrocephalus is a serious and rare phenomenon, which is becoming better known since it was first described in 1994 by Pang and Altschuler. Forced drainage at negative pressures can, in most cases, restore the ventricles to their original size, thus achieving neurological recovery. We present six new cases that suffered this syndrome from 2015 to 2020: two of them after medulloblastoma surgery; a third one as a consequence of a severe head trauma that required bifrontal craniectomy; another one after craniopharyngioma surgery; a fifth one with leptomeningeal glioneuronal tumor; and, finally, a patient carrier a shunt for normotensive hydrocephalus diagnosed ten years before. At the moment of development of this condition, four of them had mid-low-pressure cerebrospinal fluid (CSF) shunts. Four patients required cerebrospinal fluid (CSF) drainage at negative pressures oscillating from zero to -15 mmHg by external ventricular drainage until ventricular size normalized, followed by the placement of a new definitive low-pressure shunt, one of them to the right atrium. The duration of drainage in negative pressures through external ventricular drainage (EVD) ranged from 10 to 40 days with concomitant intracranial pressure monitoring at the neurointensive care unit. Approximately 200 cases of this syndrome have been described in the literature. The causes are varied and superimposable to those of high-pressure hydrocephalus. Neurological impairment is due to ventricular size and not to pressure values. Subzero drainage is still the most commonly used method, but other treatments have been described, such as neck wrapping, ventriculostomy of the third ventricle, and lumbar blood patches when associated with lumbar puncture. Its pathophysiology is not clear, although it seems to involve changes in the permeability and viscoelasticity of the brain parenchyma together with an imbalance in CSF circulation in the craniospinal subarachnoid space.

Case report: Levodopa-responsive parkinsonism with akinetic mutism after ventriculo-peritoneal shunt

Background

Parkinsonism and akinetic mutism (AM) following ventriculo-peritoneal shunt (VPS) without underdrainage used to be considered rare, but may be underdiagnosed in daily clinical practice. Although the pathophysiology is still unclear, in several case reports, the parkinsonism and AM after VPS shows responsiveness to dopaminergic treatment.

Case presentation

We report a 19-year-old male that presented with severe parkinsonism and AM after VPS. Meanwhile, ¹⁸F-FDG-PET showed a cortical and subcortical hypometabolism. Fortunately, levodopa dramatically improved patient's symptoms and brain hypometabolism. This report provides support for the possibility that dopamine deficiency inhibits brain metabolism, and further elucidates the pathogenesis of parkinsonism and AM.

Conclusion

This report highlights the presentation of a treatable parkinsonism and points out that Levodopa and/or dopamine agonist should be the first choice if the patients develop parkinson-like symptoms after VPS.

A neural stem cell paradigm of pediatric hydrocephalus

Pediatric hydrocephalus, the leading reason for brain surgery in children, is characterized by enlargement of the cerebral ventricles classically attributed to cerebrospinal fluid (CSF) overaccumulation. Neurosurgical shunting to reduce CSF volume is the default treatment that intends to reinstate normal CSF homeostasis, yet neurodevelopmental disability often persists in hydrocephalic children despite optimal surgical management. Here, we discuss recent human genetic and animal model studies that are shifting the view of pediatric hydrocephalus from an impaired fluid plumbing model to a new paradigm of dysregulated neural stem cell (NSC) fate. NSCs are neuroprogenitor cells that comprise the germinal neuroepithelium lining the prenatal brain ventricles. We propose that heterogenous defects in the development of these cells converge to disrupt cerebrocortical morphogenesis, leading to abnormal brain-CSF biomechanical interactions that facilitate passive pooling of CSF and secondary ventricular distention. A significant subset of pediatric hydrocephalus may thus in fact be due to a developmental brain malformation leading to secondary enlargement of the ventricles rather than a primary defect of CSF circulation. If hydrocephalus is indeed a neuroradiographic presentation of an inborn brain defect, it suggests the need to focus on optimizing neurodevelopment, rather than CSF diversion, as the primary treatment strategy for these children.

Solving a complex, rare, and challenging scenario in a normal pressure hydrocephalus with recurrent shunt dysfunction and multiple revisions - The opposing role of evolving low-pressure hydrocephalus and idiopathic raised intra-abdominal pressure

Background

Maintenance of pressure gradient within the intracranial chamber, shunt hardware, and the abdominal cavity plays a significant role in the optimal functioning of the ventriculo peritoneal shunt. We report a rare and a complex scenario in a patient with normal pressure hydrocephalus (NPH) who had recurrent and refractory ventricular peritoneal shunt dysfunction. Following a meticulous analysis, this was attributed to a very rare, and, first to be documented in the literature, a combination of an evolved very low pressure hydrocephalus (VLPH) system and asymptomatic raised intra-abdominal pressure (IAP).

Case Description

A 72-year-old male presented with NPH syndrome, associated with recurrent shunt dysfunction. A thorough systematic evaluation, which included intracranial pressure monitoring and IAP monitoring, revealed the presence of VLPH and a concomitant elevated IAP that was asymptomatic. This unique situation required changes in surgical strategy, which included correction of VLPH state, insertion of the anti-siphon device, and the placement of the distal end of the shunt into the pleural cavity. This led to solving the "mystery" of recurrent shunt dysfunction in this complex scenario.

Conclusion

It is imperative to perform the pressure analysis of the intracranial chamber, shunt hardware, and even the abdominal cavity, especially, in every case of refractory shunt revisions. Possibilities of a rare cause such as VLPH or an asymptomatic raised IAP acting alone or in combination must be considered. Only then, the final cerebrospinal fluid diversion strategy should be decided.

Arterial Spin-Labeling Perfusion Metrics in Pediatric Posterior Fossa Tumor Surgery

BACKGROUND AND PURPOSE

Pediatric posterior fossa tumors often present with hydrocephalus; postoperatively, up to 25% of patients develop cerebellar mutism syndrome. Arterial spin-labeling is a noninvasive means of quantifying CBF and bolus arrival time. The aim of this study was to investigate how changes in perfusion metrics in children with posterior fossa tumors are modulated by cerebellar mutism syndrome and hydrocephalus requiring pre-resection CSF diversion.

MATERIALS AND METHODS

Forty-four patients were prospectively scanned at 3 time points (preoperatively, postoperatively, and at 3-month follow-up) with single- and multi-inflow time arterial spin-labeling sequences. Regional analyses of CBF and bolus arrival time were conducted using coregistered anatomic parcellations. ANOVA and multivariable, linear mixed-effects modeling analysis approaches were used. The study was registered at clinicaltrials.gov (NCT03471026).

RESULTS

CBF increased after tumor resection and at follow-up scanning (P = .045). Bolus arrival time decreased after tumor resection and at follow-up scanning (P = .018). Bolus arrival time was prolonged (P = .058) following the midline approach, compared with cerebellar hemispheric surgical approaches to posterior fossa tumors. Multivariable linear mixed-effects modeling showed that regional perfusion changes were more pronounced in the 6 children who presented with symptomatic obstructive hydrocephalus requiring pre-resection CSF diversion, with hydrocephalus lowering the baseline mean CBF by 20.5 (standard error, 6.27) mL/100g/min. Children diagnosed with cerebellar mutism syndrome (8/44, 18.2%) had significantly higher CBF at follow-up imaging than those who were not (P = .040), but no differences in pre- or postoperative perfusion parameters were seen.

CONCLUSIONS

Multi-inflow time arterial spin-labeling shows promise as a noninvasive tool to evaluate cerebral perfusion in the setting of pediatric obstructive hydrocephalus and demonstrates increased CBF following resolution of cerebellar mutism syndrome.

Treatment-responsive Holmes tremor in a child with low-pressure hydrocephalus: video case report and systematic review of the literature

OBJECTIVE

Holmes tremor (HT) is a rare and debilitating movement disorder comprising both rest and action tremor, and it is known for its resistance to treatment. Its most common causes include ischemic or hemorrhagic insults and trauma. Mechanistically, the combined rest and action tremor is thought to require a double lesion of both the dopaminergic nigrostriatal system and the dentatorubrothalamic pathways, often near the midbrain where both pathways converge. The aim of this study was to characterize HT as a presenting sign in cases of hydrocephalus and to discuss potential pathomechanisms, clinical presentations, and treatment options.

METHODS

MEDLINE and Web of Science were searched for cases of HT with hydrocephalus from database inception to August 2021, and these were compiled along with the authors' own unique case of treatment-responsive HT in a child with low-pressure obstructive hydrocephalus secondary to a tectal tumor. Patient characteristics, presenting signs/symptoms, potential precipitating factors, interventions, and patient outcomes were recorded.

RESULTS

Nine patients were identified including the authors' video case report. All patients had a triventriculomegaly pattern with at least a component of obstructive hydrocephalus, and 4 patients were identified as having low-pressure hydrocephalus. Parinaud's syndrome and bradykinesia were the most commonly associated signs. Levodopa and CSF diversion were the most commonly used and effective treatments for HT in this population. This review was not registered and did not receive any funding.

CONCLUSIONS

HT is a poorly understood and probably underrecognized presentation of hydrocephalus that is difficult to treat, limiting the strength of the evidence in this review. Treatment options include CSF diversion, antiparkinsonian agents, antiepileptic agents, deep brain stimulation, and MR-guided focused ultrasound, and aim toward the nigrostriatal and dentatorubrothalamic pathways hypothesized to be involved in its pathophysiology.

Brain ventricles as windows into brain development and disease

Dilation of the fluid-filled cerebral ventricles (ventriculomegaly) characterizes hydrocephalus and is frequently seen in autism and schizophrenia. Recent work suggests that the genomic study of congenital hydrocephalus may be unexpectedly fertile ground for revealing insights into neural stem cell regulation, human cerebrocortical development, and pathogenesis of neuropsychiatric disease.

Acute negative-pressure hydrocephalus: Management algorithm and value of early endoscopic ventriculostomy

INTRODUCTION

Acute negative-pressure hydrocephalus is an uncommon, underrecognized patology with a high morbidity and mortality. We propose an algorithm to facilitate the management of these patients, promoting the early diagnosis and the use of endoscopic third ventriculostomy as initial therapeutic option.

METHODS

We performed an observational retrospective study in which patients diagnosed with acute negative-pressure hydrocephalus were included. Patient age and symptoms, primary etiology of hydrocephalus, previous shunt, infection and surgical procedures, time from clinical deterioration to endoscopic procedure, definitive treatment and patient outcomes were recorded. Our management algortihm is exposed and justified.

RESULTS

We identified five patients with diagnosis of acute negative-pressure hydrcephalus. In four of them the management algorithm was applied and early diagnosis and endoscopic ventriculostomy were performed. We observed complete succes of the endoscopic procedure in two patients (50%); the other two required permanent shunt, nevertheless resolution of the low-pressure state was achieved. One patient died after systemic infection (20%), 80% of the patients experienced good outcome.

CONCLUSIONS

The early identification of a negative-pressure hydrocephalic state is essential to reduce complications. Application of a specific management algortihm and early endoscopic third ventriculostomy could be advantageous to achieve better outcomes.

Acute communicating hydrocephalus after intracranial arachnoid cyst decompression: A report of two cases

Background:

Arachnoid cysts (AC) may cause hydrocephalus and neurological symptoms, necessitating surgical intervention. Cyst drainage may result in postoperative complications, however, these interventions are not normally associated with the subsequent development of acute hydrocephalus. Herein, we present two unique cases of AC drainage with postoperative development of acute communicating hydrocephalus.

Case Description:

Case 1. A 75-year-old female presented with progressive headaches, cognitive decline, and questionable seizures. Her neurological examination was non-focal, but a head computed tomography scan (CT) identified a large right frontal AC with mass effect. She subsequently underwent craniotomy and decompression of the cyst. Postoperatively, her neurological examination deteriorated, and a head CT demonstrated new communicating hydrocephalus. The opening pressure was elevated upon placement of an external ventricular drain. Her hydrocephalus improved on follow-up imaging, but her neurological examination failed to improve, and she ultimately expired. Case 2. A 61-year-old female presented with headache and seizures attributed to a left parietal AC. She underwent open craniotomy for fenestration of the cyst into the Sylvian fissure. Postoperatively, her neurologic examination deteriorated, and she developed acute communicating hydrocephalus. She was initially managed with external ventricular drainage (EVD). The hydrocephalus resolved after several days, and the EVD was subsequently removed. Late follow-up imaging at 2 years showed that the regression of the AC was maintained.

Conclusion:

Acute development of hydrocephalus is a potential complication of intracranial AC fenestration. A better understanding of intracranial cerebrospinal fluid flow dynamics may better inform as to the underlying cause of this complication.

Brain stiffness following recovery in a patient with an episode of low-pressure hydrocephalus: case report

The authors describe a follow-up to a case of a 19-year-old female with shunted aqueductal stenosis who presented with low-pressure hydrocephalus during a shunt malfunction. Shortly after management with CSF drainage at negative pressure, a magnetic resonance elastography scan was performed and revealed very low brain stiffness (high compliance). Here we present the case of the same patient seen 2 years later, now 21 years old, who again received a magnetic resonance elastography scan after receiving treatment for another shunt malfunction, this time with high intracranial pressure. This scan revealed recovery of brain stiffness to a near normal value for the patients' age. This observation suggests the low brain stiffness observed during the low-pressure hydrocephalus event is reversible. The authors discuss these findings in relation to biomechanical hypotheses of low-pressure hydrocephalus.

Acute low-pressure hydrocephalus: a case series and systematic review of 195 patients

OBJECTIVE

Acute low-pressure hydrocephalus (ALPH) is characterized by clinical manifestations of an apparent raised intracranial pressure (ICP) and ventriculomegaly despite measured ICP that is below the expected range (i.e., typically ≤ 5 cm H2O). ALPH is often refractory to standard hydrocephalus intervention protocols and the ICP paradox commonly leads to delayed diagnosis. The aim of this study was to characterize ALPH and develop an algorithm to facilitate diagnosis and management for patients with ALPH.

METHODS

EMBASE, MEDLINE, and Google Scholar databases were searched for ALPH cases from its first description in 1994 until 2019. Cases that met inclusion criteria were pooled with cases managed at the authors' institution. Patient characteristics, presenting signs/symptoms, precipitating factors, temporizing interventions, definitive treatment, and patient outcomes were recorded.

RESULTS

There were 195 patients identified, with 42 local and 153 from the literature review (53 pediatric patients and 142 adults). Decreased level of consciousness was the predominant clinical sign. The most common etiologies of hydrocephalus were neoplasm and hemorrhage. While the majority of ALPH occurred spontaneously, 39% of pediatric patients had previously undergone a lumbar puncture. Prior to ALPH diagnosis, 92% of pediatric and 39% of adult patients had a ventricular shunt in situ. The most common temporizing intervention was subatmospheric CSF drainage. The majority of patients underwent a shunt insertion/revision or endoscopic third ventriculostomy as definitive ALPH treatment. Although the mortality rate was 11%, 83% of pediatric and 49% of adult patients returned to their pre-ALPH neurological functional status after definitive treatment. Outcomes were related to both the severity of the underlying neurosurgical disease causing the hydrocephalus and the efficacy of ALPH treatment.

CONCLUSIONS

ALPH is an underrecognized variant phenotype of hydrocephalus that is associated with multiple etiologies and can be challenging to treat as it frequently does not initially respond to standard strategies of CSF shunting. With early recognition, ALPH can be effectively managed. A management algorithm is provided as a guide for this purpose.

Surgical techniques in the management of supratentorial pediatric brain tumors: 10 years' experience at a tertiary care center in the Middle East

Background:

The goal of this retrospective study is to present the first epidemiological data on pediatric supratentorial central nervous system (CNS) tumors in Lebanon and to review the various surgical management strategies used.

Methods:

We conducted a retrospective case series of all pediatric patients who presented with a supratentorial CNS tumor and underwent surgery at our institution between 2006 and 2016. We collected and analyzed demographic characteristics, tumor location, clinical manifestations, histopathology, and surgical management strategies and outcome, and discussed them after dividing the tumors as per location and in view of published literature.

Results:

Ninety-nine children were studied with a male-to-female ratio of 2.3:1 and a mean age of 8.5 years. The most common location was convexity (44%) and included low-grade and high-grade glial tumors, along with other miscellaneous lesions. The next location was sellar/diencephalic (34%), including craniopharyngiomas, hypothalamic/optic pathway/thalamic gliomas, hamartomas, and pituitary/Rathke’s cyst, where there was notable use of endoscopic techniques (21%). Tumors in the pineal region (13%) were tectal gliomas, germ cell tumors, and pineoblastomas and were mostly treated endoscopically. The last group was lateral intraventricular tumors (8%) and was mostly choroid plexus lesions and ependymomas. Overall, the surgical objective was achieved in 95% with mild/moderate complications in 17%.

Conclusion:

A variety of pathologies may affect the pediatric population in the supratentorial region. Different surgical strategies, including microsurgical and endoscopic techniques, may be employed to remove, debulk, or biopsy these tumors depending on their location, suspected diagnosis, prognosis, and the need for treatment of possible associated hydrocephalus.

Low-pressure CSF shunt malfunction without preceding lumbar puncture treated by epidural blood patch: report of 2 cases

Low-pressure CSF shunt malfunction is a poorly understood complication of hydrocephalus affecting patients of all ages. Treatment commonly requires external drainage of CSF to subatmospheric pressures for days to weeks in an intensive care setting. The current communication describes the repurposing of an established therapeutic technique, epidural blood patch, for successful initial management in 2 cases of low-pressure shunt malfunction in the absence of a recognized spinal CSF fistula. This technique may shorten length of stay and obviate potential morbidity in the management of what is otherwise a vexatious clinical problem.

Negative-pressure hydrocephalus in the course of a complex postoperative intracranial pressure disturbance: illustrative case

BACKGROUND

Negative-pressure hydrocephalus (NePH) is a rare clinical entity that presents on the background of ventriculomegaly with atypical symptoms. Its diagnosis is difficult, and some patients experience several shunt revisions until the proper solution is found.

OBSERVATIONS

The authors present a patient who developed acute deterioration due to iatrogenic NePH after surgery for a vertebral artery thrombosed giant aneurysm. The deterioration occurred after the insertion of a lumbar drain by which the authors intended to reduce a postoperative subcutaneous cerebrospinal fluid (CSF) collection. The drainage created an unexpected negative-pressure gradient in the CSF spaces, which resulted in NePH. Interventions, such as extraventricular drainage and blood patch, corrected the negative transmantle pressure and stabilized the patient’s condition.

LESSONS

Because the pathophysiology of NePH is theoretically considered to be caused by negative transmantle pressure, the intervention should be performed in order to deal with the coexistence of obstruction in the CSF pathways and a CSF leak. A blood patch would be an effective option in treating the CSF leak when the site of leakage is certain. This is the first case in which a blood patch was effectively applied in the treatment for NePH with a favorable outcome without any permanent CSF diversion.

Pneumocephalus in subthalamic deep brain stimulation for Parkinson's disease: a comparison of two different surgical techniques considering factors conditioning brain shift and target precision

BACKGROUND

Precise placement of electrodes in deep brain stimulation (DBS) may be influenced by brain shift caused by cerebrospinal fluid leaking or air inflow. We compared accuracy and treatment outcomes between a standard technique and one aiming at reducing brain shift.

METHODS

We retrospectively reviewed 46 patients (92 targets) treated with bilateral subthalamic-DBS for Parkinson's disease. The patients were divided into two groups: group A surgery was performed in supine position with standard burr hole, dural opening, fibrin glue and gelfoam plugging. Group B patients were operated in a semi-sitting position with direct dural puncture to reduce CSF loss. We analysed target deviation on head CT performed immediately after surgery and at 1 month merged with preoperative MRI planning. We recorded pneumocephalus volume, brain atrophy and target correction by intraoperative neurophysiology (ION).

RESULTS

In group A, the mean pneumocephalus volume was 10.55 cm³, mean brain volume 1116 cm³, mean target deviation 1.09 mm and ION corrected 70% of targets. In group B, mean pneumocephalus was 7.60 cm³ (p = 0.3048), mean brain volume 1132 cm³ (p = 0.6526), mean target deviation 0.64 mm (p = 0.0074) and ION corrected 50% of targets (p = 0.4886). Most leads' deviations realigned to the planned target after pneumocephalus reabsorbtion suggesting a deviation caused by displacement of anatomical structures due to brain shift. Definitive lead position was always decided with ION.

CONCLUSIONS

The modified DBS technique significantly reduced errors of electrode placement, though such difference was clinically irrelevant. ION corrected a high amount of trajectories in both groups (70% vs 50%). The choice of either strategy is acceptable.

Acute negative-pressure hydrocephalus: Management algorithm and value of early endoscopic ventriculostomy

INTRODUCTION

Acute negative-pressure hydrocephalus is an uncommon, underrecognized patology with a high morbidity and mortality. We propose an algorithm to facilitate the management of these patients, promoting the early diagnosis and the use of endoscopic third ventriculostomy as initial therapeutic option.

MATERIAL AND METHODS

We performed an observational retrospective study in which patients diagnosed with acute negative-pressure hydrocephalus were included. Patient age and symptoms, primary etiology of hydrocephalus, previous shunt, infection and surgical procedures, time from clinical deterioration to endoscopic procedure, definitive treatment and patient outcomes were recorded. Our management algortihm is exposed and justified.

RESULTS

We identified 5patients with diagnosis of acute negative-pressure hydrcephalus. In 4 of them the management algorithm was applied and early diagnosis and endoscopic ventriculostomy were performed. We observed complete succes of the endoscopic procedure in 2 patients (50%); the other 2required permanent shunt, nevertheless resolution of the low-pressure state was achieved. One patient died after systemic infection (20%), 80% of the patients experienced good outcome.

CONCLUSIONS

The early identification of a negative-pressure hydrocephalic state is essential to reduce complications. Application of a specific management algortihm and early endoscopic third ventriculostomy could be advantageous to achieve better outcomes.

Ultra-low-pressure hydrocephalic state in NPH: benefits of therapeutic siphoning with adjustable antigravity valves

BACKGROUND

Idiopathic normal-pressure hydrocephalus (NPH) is a condition of the elderly treated by ventriculoperitoneal shunt (VP) insertion. A subset of NPH patients respond only temporarily to shunt insertion despite low valve opening pressure. This study aims to describe our experience of patients who benefit from further CSF drainage by adding adjustable antigravity valves and draining CSF at ultra-low pressure.

METHODS

Single-centre retrospective case series of patients undergoing shunt valve revision from an adjustable differential pressure valve with fixed antigravity unit to a system incorporating an adjustable gravitational valve (Miethke proSA). Patients were screened from a database of NPH patients undergoing CSF diversion over 10 consecutive years (April 2008-April 2018). Clinical records were retrospectively reviewed for interventions and clinical outcomes.

RESULTS

Nineteen (10F:9M) patients underwent elective VP shunt revision to a system incorporating an adjustable gravitational valve. Mean age 77.1 ± 7.1 years (mean ± SD). Eleven patients (58%) showed significant improvement in walking speed following shunt revision. Fourteen patients/carers (74%) reported subjective improvements in symptoms following shunt revision.

CONCLUSIONS

Patients presenting symptoms relapse following VP shunting may represent a group of patients with ultra-low-pressure hydrocephalus, for whom further CSF drainage may lead to an improvement in symptoms. These cases may benefit from shunt revision with an adjustable gravitational valve, adjustment of which can lead to controlled siphoning of CSF and drain CSF despite ultra-low CSF pressure.

Low-Pressure Hydrocephalus and Shunt Malfunction Following a Lumbar Puncture in an Adult Reversed by an Epidural Blood Patch

Background

Low-pressure hydrocephalus (LPH) is a relatively rare condition, and its presentation is similar to the classically seen high-pressure hydrocephalus, with headaches, cranial nerve dysfunction, ataxia, and disturbances of consciousness. Cerebral cerebrospinal fluid loss in the presence of altered brain viscoelastic properties has previously been suggested as the pathophysiologic process leading to ventriculomegaly, despite low or negative intracranial pressures and patent shunts. More recently, cerebral venous overdrainage has been proposed as a possible explanation in the pathogenesis of LPH, although its connection to lumbar punctures in patients with shunts has not been contemplated yet. The effectiveness of epidural blood patch in the management of post-lumbar puncture LPH has been shown in children but has not been reported in adults.

Case Description

Herein we detail 2 episodes of shunt malfunction in a 30-year-old female patient with a history of hydrocephalus related to a posterior fossa tumor diagnosed during childhood. In both instances, imaging studies demonstrated ventricular dilation along with perimedullary cistern enlargement and brainstem distortion, which occurred following a lumbar puncture despite a patent shunt. A lumbar blood patch was effective in both episodes, enabling resolution of the ventriculomegaly and a good outcome.

Conclusions

A blood patch can be efficient in adults with post-lumbar puncture LPH. Some symptoms may be explained by brainstem compression caused by enlarged cerebrospinal fluid spaces at the skull base. The role of cerebral venous overdrainage in the setting of post-lumbar puncture LPH is further supported.

Shunt Treatment for Coccidioidomycosis-Related Hydrocephalus: A Single-Center Series

OBJECTIVE

Coccidioidomycosis is a fungal infection endemic to the southwestern United States. Hydrocephalus can develop after intracranial dissemination, and management of this disease entity is difficult. We present our institutional experience with shunting coccidioidomycosis-related hydrocephalus.

METHODS

A cohort of patients with coccidioidomycosis-related hydrocephalus undergoing an intracranial shunt placement were retrospectively identified over a 24-year period. Demographics and treatment characteristics were obtained from the electronic medical record.

RESULTS

Thirty patients undergoing 83 procedures were identified, with a median follow-up of 19.4 months. The average age of the cohort was 43 years at the time of initial shunt placement. Most patients (66.7%) had ≥1 shunt failure, and the average number of revisions required was 2.6 for patients who had shunt failure. The average shunt valve pressure threshold required was 5.5 cm H₂O, and patients who harbored the disease for a longer period (>7 months) had a lower pressure setting for initial shunt valves. Shunts without an antisiphon component were more likely to be failure free on multivariate analysis (odds ratio, 9.2; 95% confidence interval, 2.4-35.7). Death was associated with a longer diagnosis-to-shunt time interval, and patients having been diagnosed with intracranial disease for more than 10 months before shunt placement had significantly higher rates of death on follow-up.

CONCLUSIONS

Patients with coccidioidomycosis-related hydrocephalus typically have normal to low pressure setting requirements, high shunt failure rates, prolonged hospitalizations, and mortality. In this disease context, shunt valves without an antisiphon component are associated with lower shunt failure rates.

Development and Calculation of a Computer Model and Modern Distributed Algorithms for Dispersed Systems Aggregation

In this work, an attempt has been made to eliminate the contradiction of the Smoluchowski equation, using modern distributed algorithms for creating calculation algorithm and implementation a program for building a more perfect model by changing the type of the kinetic equation of aggregation taking into account the relaxation times. On the basis of the applied Mathcad package, there is a developed computer model for calculating the aggregation of dispersed systems. The obtained system of differential equations of the second order is solved by the Runge-Kutt method. The authors are presetting the initial conditions of the calculation. A subsequent analysis was made of the obtained non-local equations and the study of the behavior of solutions of different orders. Also, this research can be aimed at the generalization of the proposed approach for the analysis of aggregation processes in heterogeneous dispersed systems, involving the creation of aggregation models, taking into account both time and space non-locality.

Techniques for pneumocephalus and brain shift reduction in DBS surgery: a review of the literature

Deep brain stimulation has become an established therapeutic choice to manage the symptoms of medically refractory Parkinson's disease. Its efficacy is highly dependent on the accuracy of electrodes' positioning in the correct anatomical target. During DBS procedure, the opening of the dura mater induces the displacement of neural structures. This effect mainly depends on the loss of the physiological negative intracranial pressure, air inflow, and loss of cerebrospinal fluid. Several studies concentrated on correcting surgical techniques for DBS electrodes' positioning in order to reduce pneumocephalus which may result in therapeutic failure. The authors focused in particular on reducing the brain air window and maintaining the pressure gradient between intra- and extracranial compartments. A significant reduction of pneumocephalus and brain shift was obtained by excluding the opening of the subarachnoid space, by covering the dura mater opening with tissue sealant and by reducing the intracranial pressure in general anesthesia. Smaller burr hole diameters were not statistically relevant for reducing air inflow and displacement of anatomical targets. The review of the literature showed that conserving a physiological intra-extracranial pressure gradient plays a fundamental role in avoiding pneumocephalus and consequent displacement of brain structures, which improves surgical accuracy and DBS long-term results.

Obstruction of Ventriculoperitoneal Shunt After Myelography-Report of a Unique Case and Its Treatment

BACKGROUND

Myelography, frequently supplanted by noninvasive, efficient magnetic resonance imaging, remains a useful technique when evaluating the spinal canal in nerve root avulsion, radiation therapy treatment planning, cerebrospinal fluid (CSF) loculation, and CSF leak. Myelography is achieved through a lumbar puncture and instillation of nonionic, water-soluble intrathecal iohexol (Omnipaque, GE Healthcare, Marlborough, Massachusetts, USA) contrast. The aim of the study was to highlight a possible complication of obstruction of a shunt valve due to an increased viscosity of the CSF after intrathecal Omnipaque contrast administration during myelography.

CASE DESCRIPTION

The authors report a case of myelography that resulted in obstruction of a ventriculoperitoneal (VP) shunt. A 23-year-old female with significant medical history of neurofibromatosis type I, obstructive hydrocephalus, anterior cervical diskectomy and fusion, and VP shunt placement underwent diagnostic computed tomography after myelography with Omnipaque contrast to assess possible CSF loculation and cord impingement from her cervical instrumentation. The patient experienced somnolence after myelography from obstruction of the VP shunt, with marked ventriculomegaly demonstrated by computed tomography of the head. A shunt tap and shunt pumping regimen resulted in resolution of the obstruction and hydrocephalus, with return to neurologic baseline.

CONCLUSIONS

This is a recent case of VP shunt obstruction after myelography, of which previous cases reported are decades old. A shunt pumping regimen may be a nonoperative, effective mean for similar mechanical obstructions of VP shunts for restoration of flow and patency of the shunt system in these patients. We encourage physicians to consider the possibility of shunt obstruction after diagnostic myelography. Caution and close observation should be considered in patients undergoing myelography with a programmable VP shunt.

Intraoperative measurement of intraventricular pressure in dogs with communicating internal hydrocephalus

Collapse of the lateral cerebral ventricles after ventriculo-peritoneal drainage is a fatal complication in dogs with internal hydrocephalus. It occurs due to excessive outflow of cerebrospinal fluid into the peritoneal cavity (overshunting). In most shunt systems, one-way valves with different pressure settings regulate flow into the distal catheter to avoid overshunting. The rationale for the choice of an appropriate opening pressure is a setting at the upper limit of normal intracranial pressure in dogs. However, physiological intraventricular pressure in normal dogs vary between 5 and 12 mm Hg. Furthermore, we hypothesise that intraventricular pressure in hydrocephalic dogs might differ from pressure in normal dogs and we also consider that normotensive hydrocephalus exists in dogs, as in humans. In order to evaluate intraventricular pressure in hydrocephalic dogs, twenty-three client owned dogs with newly diagnosed communicating internal hydrocephalus were examined before implantation of a ventriculo-peritoneal shunt using a single use piezo-resistive strain-gauge sensor (MicroSensor ICP probe). Ventricular volume and brain volume were measured before surgery, based on magnetic resonance images. Total ventricular volume was calculated and expressed in relation to the total volume of the brain, including the cerebrum, cerebellum, and brainstem (ventricle-brain index). Multiple logistic regression analysis was performed to assess the influence of the covariates "age", "gender", "duration of clinical signs", "body weight", and "ventricle-brain index" on intraventricular pressure. The mean cerebrospinal fluid pressure in the hydrocephalic dogs was 8.8 mm Hg (standard deviation 4.22), ranging from 3-18 mm Hg. The covariates "age", (P = 0.782), "gender" (P = 0.162), "body weight", (P = 0.065), or ventricle-brain index (P = 0.27)" were not correlated with intraventricular pressure. The duration of clinical signs before surgery, however, was correlated with intraventricular pressure (P< 0.0001). Dogs with internal hydrocephalus do not necessarily have increased intraventricular pressure. Normotensive communicating hydrocephalus exists in dogs.

Diagnosis and Management for Secondary Low- or Negative-Pressure Hydrocephalus and a New Hydrocephalus Classification Based on Ventricular Pressure

BACKGROUND

Low-pressure hydrocephalus (LPH) and negative-pressure hydrocephalus (NegPH), secondary to traumatic brain injury, cerebral hemorrhage, tumor resection, and central nervous system (CNS) infection in adults, are seldom reported. They have not been recognized enough pathophysiologically in previous clinical practice. They used to have poor prognosis, and routine shunt surgery has unsatisfactory outcomes. The current classifications of hydrocephalus do not provide proper guidance for clinical practice, especially for LPH and NegPH.

METHODS

Thirty-nine cases of LPH and NegPH were included from January 2013 to March 2018. Clinical features and image characteristics were reviewed. The prognosis of these patients were evaluated by Glasgow Outcome Scale-Extended (GOS-E) within 3 months after external ventricular drainage or ventriculoperitoneal (VP) shunt accepted. Management strategies were discussed in detail.

RESULTS

Ventricular pressure was lower than 70 mm H₂O in all 39 patients, and the lowest value was -10 cm H₂O. About an average of 3.5 operations were completed for every patient. Eighteen cases had CNS infection. Eight patients died. Besides 2 patients lost to follow-up, all patients had a poor prognosis with an average GOS-E score of 2.7. For the 29 surviving patients, the time interval from onset to last VP shunt achieved was 31-3880 days, with an average of 376 days.

CONCLUSIONS

Both LPH and NegPH used to have poor prognosis. However, a good prognosis can be achieved by proper management with a further understanding of the pathophysiology. A new classification for hydrocephalus was proposed according to ventricular pressure, which is necessary and reasonable.

Hemangioblastomatosis-associated negative-pressure hydrocephalus managed with improvised shunt

Low-pressure hydrocephalus (LPH) is a rare clinical diagnosis, characterized by neurologic decline and ventriculomegaly that persists despite normal to low intracranial pressure. LPH is typically managed by negative-pressure drainage via ventriculostomy, followed by low-resistance shunt insertion. We present the case of a middle-aged man with a history of hemangioblastomatosis who had spontaneous subarachnoid hemorrhage. He was treated with a ventriculoperitoneal shunt and then underwent resection of a Meckel's cave hemangioblastoma and whole brain irradiation. One month later, he presented to us with worsening symptoms and hydrocephalus despite shunt interrogations and revisions revealing no malfunction. Ventriculostomy drainage at negative-pressure was required for resolution of symptoms and ventriculomegaly, leading us to a diagnosis of LPH. This was successfully treated using an improvised ultra-low pressure valveless ventriculoperitoneal shunt, with maintained resolution of LPH for over one year. The system was created by ligating the distal slit valve end of a peritoneal catheter to prevent reflux and allow sub-zero pressure drainage by siphoning.

Importance of Frontal Horn Ratio and Optimal CSF Drainage in the Treatment of Very Low-Pressure Hydrocephalus

Introduction  Unlike low-pressure hydrocephalus, very low pressure hydrocephalus (VLPH) is a rarely reported clinical entity previously described to be associated with poor outcomes and to be possibly refractory to treatment with continued cerebrospinal fluid (CSF) drainage at subatmospheric pressures. ^{1, 2} We present four cases of VLPH following resection of suprasellar lesions and hypothesize that untreatable patients can be identified early, thereby avoiding futile prolonged external ventricular drainage in ICU. Methods  We performed a retrospective chart review of four cases of VLPH encountered between 2007 and 2015 in two different institutions and practices and tried to identify factors contributing to successful treatment. We hypothesized that normalization of frontal horn ratio (FHR), optimization of volume of CSF drained, and avoidance of fluid shifts would contribute to improved Glasgow Coma Score (GCS). We examined fluid shifts by studying net fluids shifts and serum levels of sodium, urea, and creatinine. We used Pearson and Spearman correlations to identify measures that would correlate with improved GCS. Results  Our study reveals that improving GCS is positively correlated with decreased FHR and increased CSF drainage within an optimal range. The most important determinant of good outcome is retention of brain viscoelasticity as evidenced by restoration and maintenance of good GCS score despite fluctuations in FHR. Conclusion  Futile prolonged subatmospheric drainage can be avoided by declining to continue treatment in patients who have permanently altered brain compliance secondary to unsealed CSF leaks, irremediable ventriculitis, and who are therefore unable to sustain an improved neurologic examination.

Diagnosis, Classification, and Management of Fourth Ventriculomegaly in Adults: Report of 9 Cases and Literature Review

OBJECTIVE

An enlarged fourth ventricle, otherwise known as fourth ventriculomegaly (4th VM), has been reported previously in the pediatric population, yet literature on adults is scant. We report our experience with 4th VM in adults over an 11-year period and review the literature.

MATERIALS AND METHODS

This was a retrospective chart review of adult patients with the diagnosis of 4th VM admitted to the intensive care unit in a tertiary care center.

RESULTS

Nine patients were identified with 4th VM. Most presented with symptoms in the posterior fossa. Five cases were related to previous shunting and the underlying neurosurgical diseases, and average time interval to develop symptoms was 5.3 years. We divided our cases into primary, acquired, and degenerative based on the pathophysiology involved. Treatments included extended subzero cerebrospinal fluid diversion using a frontal external ventricular drain followed by low-pressure shunt revision, endoscopic third ventriculostomy, suboccipital decompression, and fourth ventricular catheter placement. Literature review identified additional published cases, and there were no reports of a formal classification scheme or treatment algorithm.

CONCLUSIONS

This case series illustrates a narrow spectrum of etiologies associated with 4th VM in adults. We propose a simple classification scheme dividing 4th VM into 3 categories: primary, acquired, and degenerative. We recommend a stepwise treatment approach starting with extended subzero cerebrospinal fluid diversion followed by shunting for symptomatic primary and acquired 4th VM. Lower success rates and greater morbidity are associated with rescue procedures such as fourth ventricle drainage catheters, endoscopic third ventriculostomies, and skull base decompression.

Early variations of laboratory parameters predicting shunt-dependent hydrocephalus after subarachnoid hemorrhage

Background and purpose

Hydrocephalus is a frequent complication following subarachnoid hemorrhage. Few studies investigated the association between laboratory parameters and shunt-dependent hydrocephalus. This study aimed to investigate the variations of laboratory parameters after subarachnoid hemorrhage. We also attempted to identify predictive laboratory parameters for shunt-dependent hydrocephalus.

Methods

Multiple imputation was performed to fill the missing laboratory data using Bayesian methods in SPSS. We used univariate and multivariate Cox regression analyses to calculate hazard ratios for shunt-dependent hydrocephalus based on clinical and laboratory factors. The area under the receiver operating characteristic curve was used to determine the laboratory risk values predicting shunt-dependent hydrocephalus.

Results

We included 181 participants with a mean age of 54.4 years. Higher sodium (hazard ratio, 1.53; 95% confidence interval, 1.13–2.07; p = 0.005), lower potassium, and higher glucose levels were associated with higher shunt-dependent hydrocephalus. The receiver operating characteristic curve analysis showed that the areas under the curve of sodium, potassium, and glucose were 0.649 (cutoff value, 142.75 mEq/L), 0.609 (cutoff value, 3.04 mmol/L), and 0.664 (cutoff value, 140.51 mg/dL), respectively.

Conclusions

Despite the exploratory nature of this study, we found that higher sodium, lower potassium, and higher glucose levels were predictive values for shunt-dependent hydrocephalus from postoperative day (POD) 1 to POD 12–16 after subarachnoid hemorrhage. Strict correction of electrolyte imbalance seems necessary to reduce shunt-dependent hydrocephalus. Further large studies are warranted to confirm our findings.

Low-pressure Hydrocephalus in Children: A Case Series and Review of the Literature

Background

Low-pressure hydrocephalus (LPH) is a rare phenomenon characterized by a clinical picture consistent with elevated intracranial pressure (ICP) and ventricular enlargement, but also a well-functioning shunt and low or negative ICP.

Objective

To report our experience in evaluating this challenging problem.

Methods

Patients with LPH were identified from several sources, including institutional procedural databases and personal case logs. Electronic medical records were reviewed to collect demographic, clinical, surgical, and radiographic data to determine the presence of LPH. Each patient's clinical course, including presentation, management, and outcome, is reported.

Results

Thirty instances of LPH were identified in 29 patients. Eleven cases (37.9%) of LPH were after lumbar puncture (LP), and 19 cases (62.1%) occurred without any preceding spinal procedure. Among the post-LP patients, conservative measures alone were successful in 3 cases (27%); lumbar blood patch was successful in 2 cases (18%); and 6 cases (55%) required external cerebrospinal fluid (CSF) drainage. Of the spontaneous cases, 5 patients did not receive the full spectrum of treatment because of terminal prognosis. Of the remaining 14 patients, 11 (78.6%) required external CSF drainage. Post-LP patients required fewer days of external CSF drainage (median, 4 [range, 0-12] vs median, 11 [range, 0-90]) and had a shorter hospital stay (median, 2 [range, 2-16] vs median, 8 [range, 0-26]).

Conclusion

This study represents the largest series of LPH. Although its pathophysiology remains a mystery, there are a variety of management options. Multiple procedures and a protracted hospital stay are often required to successfully treat LPH.

Low-Pressure Hydrocephalus: A Case Report and Review of the Literature

BACKGROUND

The entity of low-pressure hydrocephalus remains poorly understood and thoroughly debated. Symptomatic improvement accompanied by decrease in ventricular size after prolonged subatmospheric drainage has been well documented, and this method has been considered the criterion standard of management. Few studies have examined alternative treatment options, either to avoid the risks associated with prolonged external ventricular drainage or because of the failure of traditional methods.

OBJECTIVES

This study compiled and examined reported cases of low-pressure hydrocephalus in an attempt to provide an up-to-date summary of the condition.

METHODS

A literature search was conducted by use of Ovid Medline and PubMed filtered for the past 25 years with specific key terms, inclusion criteria, and exclusion criteria. Selected case studies and case series were then compared, and statistical analysis was performed where appropriate.

RESULTS

Over 25 years, 17 articles met our criteria. In addition to our case, 90 cases of LPH were reported. Magnetic resonance elastography (MRE) has proved to be an effective means of studying the viscoelastic properties of the brain. Endoscopic third ventriculostomy (ETV) appears to be a strong alternative, or additional, treatment.

CONCLUSION

MRE may prove to be effective in studying LPH because of its ability to quantify viscoelastic properties in response to therapy. Additionally, ETV should be considered in cases of LPH, although there is little evidence in the current literature to support its use. There are suggestions that it may lead to fewer shunt-dependent patients. Future studies are needed because there are few documented examples.

Low pressure hydrocephalus: clinical manifestations, radiological characteristics, and treatment

Low pressure hydrocephalus (LPH) is a rare type of hydrocephalus with low intracranial pressure and ventriculomegaly. The recognition of LPH is important, and the treatment is difficult and very complicated. An understanding of how to drain cerebrospinal fluid when the intracranial pressure is lower than the opening pressure of the value represents a critical issue. Seven patients who suffered from the pain of hydrocephalus syndrome and were diagnosed with LPH were retrospectively reviewed. A ventricle peritoneal shunt was applied to all patients, and the valve system was adjusted to the lowest pressure; however, the clinical manifestations of hydrocephalus in five of seven patients did not improve over one week. Intermittent pressing of the valve in combination with the maintenance of a semi-reclined position were subsequently implemented. The symptoms of hydrocephalus began to improve from three days to two months following the initiation of intermittent valve pressing in combination with the maintenance of a semi-reclined position. At the twelve months follow up, six of seven patients (85.7%) showed good recovery to minimal disability. Intermittent valve pressing in combination with a semi-reclined position is an effective and easy method to drain cerebrospinal fluid when the intracranial pressure (ICP) is lower than the opening pressure of the value and improve hydrocephalus symptoms.

Negative-Pressure Hydrocephalus: A Case Report on Successful Treatment Under Intracranial Pressure Monitoring with Bilateral Ventriculoperitoneal Shunts

BACKGROUND

Negative-pressure hydrocephalus (NegPH), a very rare condition of unknown etiology and optimal treatment, usually presents postneurosurgery with clinical and imaging features of hydrocephalus, but with negative cerebrospinal fluid pressure.

CASE DESCRIPTION

We describe a NegPH case of -3 mm Hg intracranial pressure that was successfully treated to achieve 5 mm Hg under continuous intracranial pressure monitoring with horizontal positioning, head down and legs elevated to 10°-15°, neck wrapping for controlled venous drainage, chest and abdomen bandages, infusion of 5% dextrose fluid to lower plasma osmolarity (Na⁺, 130-135 mmol/L), daily cerebrospinal fluid drainage >200 mL, and arterial blood gas partial pressure of carbon dioxide >40 mm Hg.

Cerebral venous overdrainage: an under-recognized complication of cerebrospinal fluid diversion

Understanding the altered physiology following cerebrospinal fluid (CSF) diversion in the setting of adult hydrocephalus is important for optimizing patient care and avoiding complications. There is mounting evidence that the cerebral venous system plays a major role in intracranial pressure (ICP) dynamics especially when one takes into account the effects of postural changes, atmospheric pressure, and gravity on the craniospinal axis as a whole. An evolved mechanism acting at the cortical bridging veins, known as the “Starling resistor,” prevents overdrainage of cranial venous blood with upright positioning. This protective mechanism can become nonfunctional after CSF diversion, which can result in posture-related cerebral venous overdrainage through the cranial venous outflow tracts, leading to pathological states. This review article summarizes the relevant anatomical and physiological bases of the relationship between the craniospinal venous and CSF compartments and surveys complications that may be explained by the cerebral venous overdrainage phenomenon. It is hoped that this article adds a new dimension to our therapeutic methods, stimulates further research into this field, and ultimately improves our care of these patients.

The cerebral venous system and the postural regulation of intracranial pressure: implications in the management of patients with cerebrospinal fluid diversion

Loss of cerebrospinal fluid (CSF) occurs commonly in daily neurosurgical practice. Understanding the altered physiology following CSF loss is important for optimization of patient care and avoidance of complications. There is overwhelming evidence now that the cerebral venous system plays a major role in intracranial pressure (ICP) dynamics especially when one takes into account the effects of postural changes, atmospheric pressure, and gravity on the craniospinal axis as a whole. The CSF and cerebral venous compartments are tightly coupled in two important ways. CSF is resorbed into the venous system, and there is also an evolved mechanism that prevents overdrainage of venous blood with upright positioning known as the Starling resistor. With loss of CSF pressure, this protective mechanism could become nonfunctional which may result in posture-related venous overdrainage through the cranial venous outflow tracts leading to pathologic states. This review article summarizes the relevant anatomic and physiologic basis of the relationship between the craniospinal venous and CSF compartments in the setting of CSF diversion. It is hoped that this article improves our understanding of ICP dynamics after CSF loss, adds a new dimension to our therapeutic methods, stimulates further research into this field, and ultimately improves our care of these patients.

Endoscopic third ventriculostomy as adjunctive therapy in the treatment of low-pressure hydrocephalus in adults

Background:

Treatment of low-pressure hydrocephalus (LPH) may require prolonged external ventricular drainage (EVD) at sub-zero pressures to reverse ventriculomegaly. Endoscopic third ventriculostomy (ETV) has been used in the treatment of noncommunicating hydrocephalus; however, indications for ETV are expanding.

Methods:

Patients with the diagnosis of LPH as defined by the Pang and Altschuler criteria who underwent sub-zero drainage treatment over an 8-year period were included. Patients were divided into two cohorts based on whether or not ETV was employed during their treatment. Time from EVD placement to internalization of shunt was recorded for both groups; time from ETV to placement of shunt was recorded for the patients undergoing ETV.

Results:

Sixteen adult patients with LPH were managed with sub-zero drainage method. Ten (62.5%) patients did not undergo ETV and the average time from first ventriculostomy to shunting was 73 days (range 14–257 days). Six (37.5%) patients underwent ETV during the course of their treatment; average time from initial ventriculostomy to shunt was 114 days (range 0–236 days) (P = 0.16). Time from development of LPH to ETV ranged from 28 days to 6.5 months. In the ETV group, of the 4 patients who underwent shunting, the average time to shunting following ETV was 15.25 days.

Conclusions:

ETV can be used successfully in the management of refractory LPH to decrease the duration of EVD.

Changes in Rat Brain Tissue Microstructure and Stiffness during the Development of Experimental Obstructive Hydrocephalus

Understanding neural injury in hydrocephalus and how the brain changes during the course of the disease in-vivo remain unclear. This study describes brain deformation, microstructural and mechanical properties changes during obstructive hydrocephalus development in a rat model using multimodal magnetic resonance (MR) imaging. Hydrocephalus was induced in eight Sprague-Dawley rats (4 weeks old) by injecting a kaolin suspension into the cisterna magna. Six sham-injected rats were used as controls. MR imaging (9.4T, Bruker) was performed 1 day before, and at 3, 7 and 16 days post injection. T2-weighted MR images were collected to quantify brain deformation. MR elastography was used to measure brain stiffness, and diffusion tensor imaging (DTI) was conducted to observe brain tissue microstructure. Results showed that the enlargement of the ventricular system was associated with a decrease in the cortical gray matter thickness and caudate-putamen cross-sectional area (P < 0.001, for both), an alteration of the corpus callosum and periventricular white matter microstructure (CC+PVWM) and rearrangement of the cortical gray matter microstructure (P < 0.001, for both), while compression without gross microstructural alteration was evident in the caudate-putamen and ventral internal capsule (P < 0.001, for both). During hydrocephalus development, increased space between the white matter tracts was observed in the CC+PVWM (P < 0.001), while a decrease in space was observed for the ventral internal capsule (P < 0.001). For the cortical gray matter, an increase in extracellular tissue water was significantly associated with a decrease in tissue stiffness (P = 0.001). To conclude, this study characterizes the temporal changes in tissue microstructure, water content and stiffness in different brain regions and their association with ventricular enlargement. In summary, whilst diffusion changes were larger and statistically significant for majority of the brain regions studied, the changes in mechanical properties were modest. Moreover, the effect of ventricular enlargement is not limited to the CC+PVWM and ventral internal capsule, the extent of microstructural changes vary between brain regions, and there is regional and temporal variation in brain tissue stiffness during hydrocephalus development.

Magnetic Resonance Elastography Demonstrating Low Brain Stiffness in a Patient with Low-Pressure Hydrocephalus: Case Report

The authors describe the case of a 19-year-old female with shunted aqueductal stenosis who presented with low-pressure hydrocephalus that responded to negative pressure drainage. A magnetic resonance elastography scan performed 3 weeks later demonstrated very low brain tissue stiffness (high brain tissue compliance). An analysis of the importance of this finding in understanding this rare condition is discussed.