Hydrocephalus: slit ventricles, shunt obstructions, and third ventricle shunts: a clinical study

Ventricular Shunts

Ventricular shunts are mechanical devices used in the treatment of hydrocephalus, by means of which cerebrospinal fluid (CSF) is diverted from the ventricles to other low-pressure body cavities. Over the last 50 years, mechanical shunting has become the cornerstone for the treatment of hydrocephalus with shunt valves evolving from simple differential valves to complex programmable valves. The chief complications of ventricular shunting include obstruction, infections, and overdrainage causing subdural hematomas and slit-ventricle syndrome. As the number of commercially available valve designs continues to grow, each new generation aims at reducing the likelihood of complications, especially those resulting from overdrainage. Several studies aimed at establishing the superiority of any valve design have been conducted. All have highlighted the advantages and shortcomings of most models without conclusively providing evidence for choosing one over another. As a result, choices still rest on individual and institutional preferences.

Zebrafish cerebrospinal fluid mediates cell survival through a retinoid signaling pathway

Cerebrospinal fluid (CSF) includes conserved factors whose function is largely unexplored. To assess the role of CSF during embryonic development, CSF was repeatedly drained from embryonic zebrafish brain ventricles soon after their inflation. Removal of CSF increased cell death in the diencephalon, indicating a survival function. Factors within the CSF are required for neuroepithelial cell survival as injected mouse CSF but not artificial CSF could prevent cell death after CSF depletion. Mass spectrometry analysis of the CSF identified retinol binding protein 4 (Rbp4), which transports retinol, the precursor to retinoic acid (RA). Consistent with a role for Rbp4 in cell survival, inhibition of Rbp4 or RA synthesis increased neuroepithelial cell death. Conversely, ventricle injection of exogenous human RBP4 plus retinol, or RA alone prevented cell death after CSF depletion. Zebrafish rbp4 is highly expressed in the yolk syncytial layer, suggesting Rbp4 protein and retinol/RA precursors can be transported into the CSF from the yolk. In accord with this suggestion, injection of human RBP4 protein into the yolk prevents neuroepithelial cell death in rbp4 loss‐of‐function embryos. Together, these data support the model that Rbp4 and RA precursors are present within the CSF and used for synthesis of RA, which promotes embryonic neuroepithelial survival. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 75–92, 2016

Imaging evaluation of CSF shunts

OBJECTIVE

The objective of this article is to describe an approach to imaging CSF shunts. Topics reviewed include the components and imaging appearances of the most common types of shunts and the utility of different imaging modalities for the evaluation of shunt failure. Complications discussed include mechanical failure, infection, ventricular loculation, overdrainage, and unique complications related to each shunt type.

CONCLUSION

This article reviews the imaging features of common CSF shunts and related complications with which radiologists should be familiar.

Perforation holes in ventricular catheters--is less more?

OBJECTIVE

Obstruction is a common cause of cerebrospinal fluid (CSF) shunt failure. Risk factors for proximal obstructive malfunction are suboptimal ventricular catheter positioning and slit-like ventricles. A new ventricular catheter design to decrease risk of obstruction was evaluated.

METHODS

A review of histopathological tissue investigation from occluded ventricular catheters (n = 70) was performed. A new ventricular catheter design was realized with six perforation holes. These catheters were compared to regular catheters (16 holes, Miethke, Aesculap) for flow characteristics using ink studies and flow velocity at hydrostatic pressure levels from 14 to 2 cmH(2)O in an experimental setup. The six-hole catheters were implanted in hydrocephalic patients with slit-like ventricles (n = 55). A follow-up was performed to evaluate the need of catheter revisions.

RESULTS

Histological evaluation showed that obstructive tissue involved 43-60% extraventricular tissue, including gliosis, connective and inflammatory cells. In flow characteristic studies, the 16-hole catheters showed that only proximal perforations are of functional relevance. For six-hole catheters, all perforations were shown to be relevant with remaining reserve capacity. Flow velocity however showed no significant differences between six and 16 perforations. The six-hole catheter was implanted in 55 patients with a mean follow-up period of 15 +/- 9 months. A total of 12 catheters were explanted, revealing an overall survival proportion of 77.4%.

CONCLUSION

In narrow ventricles, we assume that catheter perforations that are located also in the tissue might be a risk for CSF shunt obstruction. Fewer amounts of perforations in the catheters with equal flow features might decrease this risk when catheters can be implanted with adequate precision.

Prevention of ventricular catheter obstruction and slit ventricle syndrome by the prophylactic use of the Integra antisiphon device in shunt therapy for pediatric hypertensive hydrocephalus: a 25-year follow-up study

OBJECT

This 25-year follow-up study was performed on 120 children with hypertensive hydrocephalus to evaluate the influence of the early prophylactic implantation of the Integra antisiphon device (ASD, Integra Neurosciences Ltd.) on the rate of proximal shunt obstructions and the frequency of symptomatic slit ventricle syndrome (SVS). The adaptability of the ASD to growth, proper positioning of the ASD as a necessity for its successful performance, and the 3 phases of SVS development are discussed.

METHOD

Since 1978, the ASD has consistently been implanted either at the time of primary shunt insertion (66 neonates, mean follow-up 11 years) or during revisions of preexisting shunts (54 children, mean follow-up 11.8 years). The complication rate among the 54 children before ASD implantation (mean follow-up 8.3 years) was compared with that among all 120 patients once an ASD had been inserted. Shunt complications were documented as ventricular catheter, distal catheter, and infectious complications.

RESULTS

The study revealed a significant long-term reduction in ventricular catheter obstructions and hospitalizations due to intermittent intracranial hypertension symptoms (symptomatic SVS) after both primary and secondary ASD implantation. Data in the study suggest that the high rate of ventricular catheter obstruction in pediatric shunt therapy is caused by hydrostatic suction induced by differential-pressure valve shunts during mobilization of the patient and that the development of a SVS can be traced back to this constant suction, which causes chronic CSF overdrainage and ventricular noncompliance. Recurrent ventricular catheter obstruction and SVS can be prevented by prophylactic supplementation of every shunt system with an ASD.

CONCLUSIONS

To inhibit chronic hydrostatic suction, to prevent overdrainage and proximal shunt obstruction, and to avoid SVS and thus improve the patient's quality of life, the prophylactic implantation of an ASD in every pediatric hydrocephalus shunt is recommended.

Pediatric gravitational shunts: initial results from a prospective study

OBJECT

The authors' goal in this paper was to evaluate prospectively the efficacy and safety of a new pediatric gravitational shunt to determine whether it warrants inclusion in a randomized, controlled trial with other shunts.

METHODS

A total of 55 children between the ages of 0 and 6 years (median age 0.5 years, average age 4+/-6 years) underwent primary shunt implantation; all received the Miethke Paedi-GAV. The follow-up period ranged between 12 and 77 months (mean 47+/-21 months). The primary end point of the study was the first shunt failure necessitating revision. The 1- and 2-year shunt survival rates were 75 and 68%, respectively. The average failure-free shunt survival duration was 1423 +/- 641 days. Based on imaging findings, no slitlike ventricles occurred. The complication rate was 33%, and the median time to shunt failure was 45 days. Underdrainage occurred in one child (1.8%) and overdrainage in two children (3.6%).

CONCLUSIONS

These preliminary results prove the Miethke Paedi-GAV to be a safe and effective pediatric shunt worthy of inclusion in a randomized comparison with other shunts in the pediatric population.

Shunts vs endoscopic third ventriculostomy in infants: are there different types and/or rates of complications? A review

INTRODUCTION

The decision-making process when we compare endoscopic third ventriculostomy (ETV) with shunts as surgical options for the treatment of hydrocephalus in infants is conditioned by the incidence of specific and shared complications of the two surgical procedures.

REVIEW

Our literature review shows that the advantages of ETV in terms of complications are almost all related to two factors: (a) the avoidance of a foreign body implantation and (b) the establishment of a 'physiological' cerebrospinal fluid (CSF) circulation. Both these kinds of achievements are particularly important in infants because of the relative high rate of some intraoperative (i.e. abdominal) and late (secondary craniosynostosis, slit-ventricle syndrome) shunt complications in this specific subset of patients. On the other side, the main factor which is claimed against ETV is the relatively high risk of immediate mortality and neurological complications. Clinical manifestations of neurological structure damage seem to be more frequent in infants, probably due to the more relevant effect of parenchymal and vascular damage in this age group; however, both the immediate mortality and neurological damage risk of ETV procedures should be weighted against the long-term mortality and the late neurological damage which is not infrequently described as a consequence of shunt malfunction and proximal shunt revision procedures. Infections are possible in both ETV and extrathecal CSF procedures, especially in infants. However, the incidence of infective complications is significantly lower in case of ETV (1-5% vs 1-20%). Moreover, different from shunting procedures, infections in children with third ventriculostomy have a more benign course, being generally controlled by antibiotic treatment alone.

Ventriculoperitoneal shunt of continuous flow vs valvular shunt for treatment of hydrocephalus in adults

BACKGROUND

Shunting for hydrocephalus is the neurosurgical procedure most frequently associated with long-term complications. We developed an alternative to valvular shunts based on a simple shunt procedure whose functioning depends on a peritoneal catheter with a highly precise cross-sectional internal diameter of 0.51 mm. Preliminary studies have shown that the shunt of continuous flow (SCF) is superior to valvular shunts for the treatment of hydrocephalus in adults. Here, we show the long-term performance of the SCF in adult patients with hydrocephalus secondary to a comprehensive variety of neurological disorders.

METHODS

In a 5-year period, ventriculoperitoneal shunting was performed on 307 patients with hydrocephalus; 114 of them were treated with the SCF and 193 controls were treated with a conventional valvular shunt. Patients were followed from 1 to 5 years after surgery; endpoint observation was considered at surgical reintervention because of shunt failure.

RESULTS

At the end of the observation period (44 +/- 17 months), the failure rate of the shunting device was 14% for the SCF and 46% for controls (P < .0002). Shunt endurance was 88% in patients with SCF and 60% in controls. Along the study, signs of overdrainage developed in 40% of patients treated with valvular shunt, but they were not observed in patients with SCF.

CONCLUSIONS

The design of the SCF was calculated according to the mean rates of cerebrospinal fluid production; it takes simultaneous advantage of the intraventricular pressure and the siphon effect and complies with the principle of uninterrupted flow, maintaining a fair equilibrium that prevents under- and overdrainage. The SCF is a simple, inexpensive, and effective treatment for hydrocephalus in adults.

Continuous-flow shunt for treatment of hydrocephalus due to lesions of the posterior fossa

OBJECT

Management of hydrocephalus caused by expansive lesions of the posterior fossa is complicated by two main drawbacks of shunt devices: sudden decompression and overdrainage. The ventriculoperitoneal (VP) continuous-flow (CF) shunt is characterized by a peritoneal catheter with an internal diameter of 0.51 mm that promotes continuous drainage of cerebrospinal fluid (CSF) at its production rate. The authors have previously demonstrated in adult patients with hydrocephalus that sudden decompression and overdrainage are absent when this shunt is used; here they report the findings of a prospective study in which the goal was to test the performance of this shunt in patients with severe hydrocephalus due to lesions of the posterior fossa.

METHODS

During a 5-year period, 103 patients with severe hydrocephalus caused by lesions of the posterior fossa were treated by placement of a VP shunt. In 53 of these patients (control group) a shunt and valve system was surgically implanted and in 50 patients a CF shunt was implanted. All patients were followed up for a minimum of 2 years after surgery. Shunt revision or change was necessary in 21 patients (40%) with conventional shunts and in four patients (8%) with the CF shunt (p < 0.003). Signs of overdrainage were observed in 18 patients (34%) in the control group, four of whom had ascending transtentorial herniation; this complication was not seen in patients with the CF shunt.

CONCLUSIONS

The CF shunt had a low rate of dysfunction and an absence of complications caused by overdrainage, which were frequently associated with the control shunts. The hydrodynamic properties of the CF shunt make it effective, even in severe cases of hydrocephalus caused by lesions of the posterior fossa.

Treatment of hydrocephalus in adults by placement of an open ventricular shunt

OBJECT

Ventricular shunt placement is the neurosurgical procedure most frequently associated with complications. Over the years, it has been a growing concern that the performance of most shunting devices does not conform to physiological parameters. An open ventriculoperitoneal (VP) bypass with a peritoneal catheter for which the cross-sectional internal diameter was 0.51 mm as a distinctive element for flow resistance was evaluated for use in the treatment of adult patients with hydrocephalus.

METHODS

During a 2-year period, open shunts were surgically implanted in 54 adults with hydrocephalus; conventional shunts were implanted in 80 matched controls. Periodic evaluations were performed using neuroimaging studies and measures of clinical status. All patients were followed from 12 to 36 months. 18.5 +/- 4 months for patients with the open shunt and 19.1 +/- 8.1 months for controls (mean +/- standard deviation). The device continued to function in 50 patients with the open shunt (93%) and in 49 controls (61%: p < 0.001). The Evans index in patients with the open shunt was 0.33 +/- 0.09 throughout the follow up. No cases of infection, overdrainage, or slit ventricles were observed: the index in controls was 0.28 +/- 0.08; 60% of them developed slit ventricles. During the follow-up period occlusion occurred in four patients with the open shunt (7%) and in 31 controls (39%: p < 0.001).

CONCLUSIONS

The daily cerebrospinal fluid (CSF) drainage through the open VP shunt is close to 500 ml of uninterrupted flow propelled by the hydrokinetic force generated by the combination of ventricular pressure and siphoning effect. It complies with hydrokinetic parameters imposed by a bypass connection between the ventricular and peritoneal cavities as well as with the physiological archetype of continuous flow and drainage according to CSF production. The open shunt is simple, inexpensive, and an effective treatment for hydrocephalus in adults.

Subtemporal decompression: the treatment of noncompliant ventricle syndrome

OBJECTIVE

To explore the effects of subtemporal decompression (STD) on the frequency of shunt revision and attendances with symptoms of raised intracranial pressure secondary to slit ventricle syndrome and slit ventricle-like syndrome. A renaming of these syndromes as noncompliant ventricle syndrome is suggested.

METHOD

A retrospective review of the notes of all patients at our institution having STD from 1984 to 1997 was conducted.

RESULTS

Twenty-eight patients underwent STD (age range, 4-31 yr). Thirty-two STD procedures were performed. The mean follow-up duration after STD was 5.3 years (range, 0-12 yr). The number of shunt revisions before STD was 128 (mean, 4.6 revisions; range, 0-30 revisions) and after STD was 28 (mean, 1.0 revision; range, 0-7 revisions). The number of attendances before STD was 213 (mean, 6.7 attendances; range, 1-31 attendances) and after STD was 57 (mean, 1.8 attendances; range, 0-10 attendances). Among 15 patients for whom there was sufficient clinical data, 7 revisions were required during the 3 years before STD and 22 during the 3 years after STD. There were 53 admissions during the 3 years before STD and 11 during the 3 years after STD.

CONCLUSION

Although the overall incidence of shunt revision decreases, there is an early increase in the frequency of revision after STD. The number of admissions of patients with raised intracranial pressure symptoms reduces after STD, and we think that this is a more important factor in the consideration of this procedure than the number of recent revisions. We explore these arguments in this article.

Targeted studies as a learning tool in outcomes assessment

Authors discuss the need for increased analytical skills in the current medical environment and suggest a method which combines the use of targeted studies and Internet communication as part of graduate medical education. Advantages of such a program include involvement of the private sector in clinical outcome studies, improvements in the design of clinical studies and publications and the early development of skills in interpreting and evaluating literature. A further goal would be the development of an understanding of the principles underlying, to the extent that it is possible, unbiased assessment of one's own clinical practices.

Ventricular shunt removal: the ultimate treatment of the slit ventricle syndrome

OBJECT

The aim of this study was to assess the effectiveness of an algorithm used to evaluate and prescribe treatment for patients having slit ventricle syndrome (SVS).

METHODS

All patients included in this protocol underwent fiberoptic intracranial pressure monitoring after removal or externalization of their ventricular shunt systems. A significant number of patients did not need extracranial cerebrospinal fluid (CSF) diversion and tolerated removal of their shunt systems without requiring further intervention. Patients who demonstrated a need for CSF drainage underwent an endoscopic third ventriculostomy, regardless of the putative cause of their hydrocephalus. Sixteen (72.7%) of 22 patients experienced resolution of or significant improvement in their SVS complaints after their inclusion in the protocol. Concomitantly, 14 (64%) of 22 patients were no longer shunt dependent after a mean follow-up period of 21.4 months.

CONCLUSIONS

A significant number of patients debilitated by SVS may experience improvement in their symptoms and undergo shunt removal according to this protocol, improving their quality of life and simplifying their medical follow up.

Differences between ventricular and lumbar cerebrospinal fluid in hydrocephalus secondary to cysticercosis

We studied ventricular and lumbar cerebrospinal fluid (CSF) in 16 patients with hydrocephalus secondary to meningeal cysticercosis, and samples were taken at the time of the surgical implantation of a ventricular shunt. All lumbar CSF samples revealed raised cell counts (mean, 72 +/- 28/mm3) and protein counts (mean, 78 +/- 12 mg/dl), as well as positive immune reactions to cysticerci antigens. In contrast, 50% of the ventricular CSF samples exhibited cell and protein counts within normal limits and five showed negative immune reactions to cysticerci antigens. Ample differences between ventricular and lumbar CSF were also observed in the contents of glucose and immunoglobulins G, A, and M. The biochemical and immunological composition of the CSF varied greatly along the cerebrospinal axis in patients with chronic arachnoiditis caused by cysticercosis. Our findings further support the premise of the subarachnoid space as an immunologically active substratum and provide information to explain the frequent occlusion of ventricular shunts in patients with hydrocephalus secondary to inflammatory disorders of the subarachnoid space.