Infant hydrocephalus: what valve first?

Does Valve Design Affect the Tensile Strength of Ventriculoperitoneal Shunts?

BACKGROUND AND OBJECTIVES

The most common treatment for hydrocephalus is ventriculoperitoneal (VP) shunting, which is problematic as shunts are prone to failure. Shunt disconnections account for a minority (8%-15%) of VP shunt failures but could be reduced through better shunt design. A better understanding of the mechanical properties of VP shunts would help explain why shunt disconnections occur. The objective of this study was to determine if the tensile properties of VP shunts differ by design.

METHODS

Linear tensile testing was conducted on 5 different valve designs (Codman Certas Plus Programmable Valve, Medtronic Delta, Integra Orbis Sigma Valve II, Medtronic PS Medical, Medtronic Strata Adjustable Valve) at both the proximal and distal ends to determine the maximum load which could be applied to different shunt designs. Each valve was progressively subjected to increasing force until the catheter disconnected from the valve, the catheter fractured, or our maximum testing limits were reached.

RESULTS

Catheters disconnected or fractured during testing with all valves. The maximum load resisted during tensile testing for similar locations in all valve designs were found to be statistically similar to one another. Only the PS Medical and Orbis Sigma II valves showed an increased maximum load at the distal end compared with the proximal end within the same device.

CONCLUSION

No single valve design was superior at preventing disconnections in VP shunts. Shunt disconnections remain a concerning problem as VP shunts are the gold standard for combating hydrocephalus.

The Evolution of Ventriculoperitoneal Shunt Valves and Why They Fail

This article reviews the historical progression of ventriculoperitoneal shunt valve designs with the goal of providing an understanding of their functionality and failure mechanisms. While shunting is the predominant treatment for hydrocephalus, the statistics of overall shunt failure remain high, and valve failure is responsible for a significant percentage of revision surgeries. Therefore, this review spans valve evolution from an engineering perspective with an emphasis on discussing potential failure mechanisms and patient-specific valve selection. Information is provided on the importance of valves in hydrocephalus treatment with discussion on each class of valves and their advantages and shortcomings. Substantial development over decades has significantly improved valve functionality, and ongoing research continues to provide more robust valves and shunt systems for hydrocephalus management.

Nonadjustable state of programmable shunt valve: obstruction of middle cranial fossa arachnoid cyst-peritoneal shunt

BACKGROUND

A nonadjustable state of the programmable shunt valve is a rare phenomenon. This case report aims to explore the cause of pressure adjustment dysfunction in a programmable shunt valve in a middle cranial fossa arachnoid cyst-peritoneal shunt patient and to underscore this dysfunction as an indicator of shunt valve obstruction.

CASE PRESENTATION

A child with a ruptured giant arachnoid cyst in the left middle cranial fossa presented with acute intracranial hypertension following head trauma. The initial cysto-peritoneal shunt surgery rapidly alleviated symptoms, including headaches, vomiting, and left cranial nerve palsy, stabilizing the clinical condition. However, between 20 and 24 months after the initial shunt surgery, the patient developed intermittent shunt dysfunction, experiencing recurrent headaches and vomiting, during which the programmable valve's pressure setting had become fixed and was no longer adjustable. A second surgery was then performed to remove the existing shunt, excise the fibrotic cyst wall, fenestrate the basal cistern, and establish temporary subdural drainage. During this operation, extensive fibrosis of the cyst wall in the subdural space was discovered, forming a tough and hypertrophic fibrotic membrane that encased the cerebral hemispheres. This fibrotic material nearly filled the shunt valve chamber, causing valve obstruction and immobilizing the pressure control rod, resulting in pressure adjustment dysfunction. As the patient could not maintain stability without continuous drainage, a third surgery was ultimately necessary to place a subdural-peritoneal shunt. Five years of follow-up revealed no significant clinical symptoms, and the patient has maintained a normal life.

CONCLUSION

Shunt valve obstruction is an underestimated cause of shunt system failure, with no current definitive method for early diagnosis. Fibrotic deposition is a primary mechanism underlying shunt valve obstruction. Pressure adjustment dysfunction in a programmable shunt valve serves as a reliable indicator of shunt valve obstruction. Further research should prioritize the treatment and prevention of shunt valve obstructions to improve outcomes in neurosurgical practice.

Hydrocephalus in prematurity: does valve choice make a difference?

PURPOSE

Extremely premature neonates diagnosed with post-haemorrhagic hydrocephalus (PHH) are recognised to have particularly poor outcomes. This study assessed the impact of a number of variables on outcomes in this cohort, in particular the choice of shunt valve mechanism.

METHODS

Electronic case notes were retrospectively reviewed of all premature neonates admitted to our centre for management of hydrocephalus between 2012 and 2021. Data included (i) gestational age, (ii) birth weight, (iii) hydrocephalus aetiology, (iv) surgical intervention, (v) shunt system, (vi) 'surgical burden' and (vii) wound failure and infection rate. Data was handled in Microsoft Excel and statistical analysis performed in SPSS v27.0 RESULTS: N = 53 premature hydrocephalic patients were identified (n = 28 (52.8%) female). Median gestational age at birth was 27 weeks (range: 23-36 + 6 weeks), with n = 35 extremely preterm patients and median birth weight of 1.9 kg (range: 0.8-3.6 kg). Total n = 99 programmable valves were implanted (n = 28 (28.3%) de novo, n = 71 (71.2%) revisions); n = 28 (28.3%) underwent n ≥ 1 pressure alterations, after which n = 21 (75%) patients had symptoms improve. In n = 8 patients exchanged from fixed to programmable valves, a mean reduction of 1.9 revisions per patient after exchange was observed (95%CI: 0.36-3.39, p = 0.02). Mean overall shunt survival was 39.5 weeks (95%CI: 30.6-48.5); 33.2 weeks (95%CI: 25.2-41.1) in programmable valves and 35.1 weeks (95%CI: 19.5-50.6) in fixed pressure (p = 0.22) with 12-month survival rates of 25.7% and 24.7%, respectively (p = 0.22). Shorter de novo shunt survival was associated with higher operation count overall (Pearson's R: - 0.54, 95%CI: - 0.72 to - 0.29, p < 0.01). Wound failure, gestational age and birth weight were significantly associated with shorter de novo shunt survival in a Cox regression proportional hazards model; gestational age had the greatest impact on shunt survival (Exp(B): 0.71, 95%CI: 0.63-0.81, p < 0.01).

CONCLUSION

Hydrocephalus is especially challenging in extreme prematurity, with a shorter de novo shunt survival associated with higher number of future revisions. Programmable valves provide flexibility with regard to pressure setting, with the potential for fewer shunt revisions in this complex cohort.

Optimization of number and range of shunt valve performance levels in infant hydrocephalus: a machine learning analysis

Shunt surgery is the main treatment modality for hydrocephalus, the leading cause of brain surgery in children. The efficacy of shunt surgery, particularly in infant hydrocephalus, continues to present serious challenges in achieving improved outcomes. The crucial role of correct adjustments of valve performance levels in shunt outcomes has been underscored. However, there are discrepancies in the performance levels of valves from different companies. This study aims to address this concern by optimizing both the number and range of valve performance levels for infant hydrocephalus, aiming for improved shunt surgery outcomes. We conducted a single-center cohort study encompassing infant hydrocephalus cases that underwent initial shunt surgery without subsequent failure or unimproved outcomes. An unsupervised hierarchical machine learning method was utilized for clustering and reporting the valve drainage pressure values for all patients within each identified cluster. The optimal number of clusters corresponds to the number of valve performance levels, with the valve drainage pressure ranges within each cluster indicating the pressure range for each performance level. Comparisons based on the Silhouette coefficient between 3-7 clusters revealed that this coefficient for the 4-cluster (4-performance level) was at least 28.3% higher than that of other cluster formations in terms of intra-cluster similarity. The Davies-Bouldin index for the 4-performance level was at least 37.2% lower than that of other configurations in terms of inter-cluster dissimilarity. Cluster stability, indicated by a Jaccard index of 71% for the 4-performance level valve, validated the robustness, reliability, and repeatability of our findings. Our suggested optimized drainage pressure ranges for each performance level (1.5-5.0, 5.0-9.0, 9.0-15.0, and 15.0-18.0 cm H2O) may potentially assist neurosurgeons in improving clinical outcomes for patients with shunted infantile hydrocephalus.

Development of shunt valves used for treating hydrocephalus: comparison with endoscopy treatment

The pathophysiology of hydrocephalus is not clearly defined. Thus, treatment will remain empirical until a fuller understanding of the various forms of hydrocephalus is achieved. Valve-controlled shunting has been the mainstay of therapy since the late 1950s. Initially, shunting occurred from the ventricular system to the atrium. In the 1970s, VA shunts were replaced by ventriculoperitoneal shunts as the primary location for the distal end. Multiple types of one-way valve systems have been developed in the pursuit of draining the appropriate amount of CSF that avoids either overdrainage or underdrainage while preserving normal brain development and cognition. These valves are reviewed and compared as to their function. Other locations for the distal end of the shunting system are reviewed to include pleural space and gallbladder. The lumbar subarachnoid space as the proximal location for a shunt is also reviewed. The only other surgical alternative for treating hydrocephalus is endoscopic third ventriculostomy. Since 2000, approximately 50% of children with hydrocephalus have been shown to be candidates for ETV. The benefits are the lack of need for an artificial shunt system and thus lower rates of infection and over time fewer reoperations. Future progress is dependent on improved shunt valve systems that are affordable worldwide and ready availability of ETV in developing countries. Anatomic and molecular causes of hydrocephalus need to be defined so that medications or genetic modifications become available for potential cure of hydrocephalus.

Recognizing and managing hydrocephalus in children

ABSTRACT

Hydrocephalus is one of the most common indications for pediatric neurosurgical intervention and is associated with the need for lifelong monitoring. All clinicians should be familiar with the complications that may arise throughout life in these patients so that they can provide timely intervention. This article focuses on the assessment of hydrocephalus, the appropriate diagnostic workup and differential diagnoses, and evidence-based surgical treatments and associated outcomes.

The survival time of the ventriculo-peritoneal-shunt in children with hydrocephalus is dependent on the type of valve implanted

PURPOSE

Despite constantly improving developments in ventriculo-peritoneal shunt systems, most patients with hydrocephalus require revision or replacement at some point of time. Therefore, this study aimed to analyse parameters that are associated with shunt dysfunction.

METHODS

In this retrospective study, we included 81 patients aged 0-17 who were treated at our institution. Demographic data, etiology of the hydrocephalus, type of valve implanted, reason for any revision procedures, any complications and survival time of the ventriculo-peritoneal shunts were detected. Statistical analysis was performed using SPSS. The significance level was set at p ≤ 0.05.

RESULTS

Over a mean study period of 18 years, we analyzed 226 valves subjected to 146 revision operations in 81 patients. The etiology of the hydrocephalus (p = 0.874) and the age of the child at the time of VP shunt implantation (p = 0.308) did not have any impact on the shunt survival time. However, the type of the valve significantly changed the survival time of the shunt (p = 0.030). Pressure differential valves presented a longer survival time than gravitational valves.

CONCLUSION

The majority of patients in this study needed at least one replacement of the initial shunt system. Pressure differential valves may be beneficial for the survival time of the shunt system.