Q26 - Performance Assessment of Hydrocephalus Shunt Valves: Flow Rate Testing and Error Analysis

Saturday, October 11, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

Samantha Sedillo

Undergraduate Researcher
The University of Tennessee Knoxville
Arvada, Colorado, United States

Co-Author(s)

Dylan Fuentala

Undergraduate Researcher
The University of Tennessee Knoxville
Memphis, Tennessee, United States
ST

Stephanie TerMaath

Associate Professor
The University of Tennessee Knoxville, United States
Bryan C. Good, PhD

Assistant Professor
University of Tennessee
Knoxville, Tennessee, United States

Introduction: : Hydrocephalus is a complex neurological disorder characterized by the accumulation of cerebrospinal fluid (CSF) within the cerebral ventricles, resulting in elevated intracranial pressure (ICP) that can cause irreversible neurological damage, physical and cognitive impairment, and, in severe cases, death. With a global prevalence estimated between 1–1.5%, hydrocephalus affects individuals across the lifespan, including nearly 400,000 new diagnoses annually. Congenital hydrocephalus, present in approximately 1 in 500 live births, represents the most common indication for pediatric neurosurgery, while acquired forms arise secondary to trauma, hemorrhage, neoplasms, or infections. Diagnosis typically involves neuroimaging (MRI or CT), CSF pressure monitoring, and, in some cases, genetic or metabolic evaluation. The primary treatment is the implantation of a ventricular shunt to divert excess CSF to another body cavity; however, shunt systems are associated with significant long term failure rates. Approximately 85% of pediatric patients undergo at least one revision surgery, and 5% require ten or more; in adults, revision rates exceed 20%.
To better understand the fluid mechanics of shunt valve failure, this study will investigate the functional performance of both new and explanted ventricular shunt valves under controlled laboratory conditions simulating physiological pressure environments. Flow rates will be measured and benchmarked against manufacturer specifications to evaluate valve reliability and identify deviations indicative of functional deterioration. By elucidating valve behaviors under both nominal and compromised conditions, this research aims to inform strategies for optimizing shunt design and reducing the incidence of surgical revisions.

Materials and

Methods: : This study tested the performance of new and explanted (failed shunts surgically removed from a hydrocephalus patient) valves of two different types (Figure 1): Codman-Hakim Programmable Valve (Integra) and Strata II (Medtronic). Both valves allow for noninvasive adjustment of their opening pressure, enabling personalized CSF drainage. Initial testing was done at the default factory settings, Level 100 for Codman-Hakim and Level 1.0 for Strata II, representing typical clinical use. After baseline data were collected, the valves were reprogrammed to match the pressure settings of the explanted patient valves (Level 120 and 2.0 for the Codman-Hakim and Strata II, respectively).
In addition to the commercial shunt valves, the experimental setup (Figure 2) included a water-filled reservoir on an adjustable stand, a ruler for measuring water height (to simulate ICP), a Medtronic proximal ventricular catheter, fluid collection beaker, and a digital scale connected to a computer for data collection. As water flowed through the valve, the digital scale recorded the weight in real time, allowing for precise measurement of flow rate. This setup enabled comparisons of valve performance under different pressure conditions to identify any deviations from expected behavior and assess reliability after implantation.

Results, Conclusions, and Discussions:: Both new shunt valves (Codman-Hakim and Strata II) demonstrated performance consistent with manufacturer specifications for pressure and flow regulation. The new Strata II valve at the 1.0 setting was tested under pressure conditions ranging from 35 to 55 mmH₂O, with measured flow rates between approximately 9.96 and 66.77 mL/hr (Figure 3). At the 2.0 setting, tested across ICPs of 105 to 125 mmH₂O, flow rates ranged from 10.90 to 18.88 mL/hr (Figure 4). Similarly, the new Codman-Hakim valve at the 100 setting (104–164 mmH₂O) (Figure 5) produced flow rates from 3.62 to 104.53 mL/hr, while at the 120 setting (124–184 mmH₂O) flow rates ranged from 5.27 to 40.54 mL/hr (Figure 6).
In contrast, the explanted (ex vivo) valves exhibited reduced flow rates and more variable performance under the same ICP conditions. The explanted Strata II valve at the 2.0 setting (Figure 7) produced flow rates between 2.83 and 28.42 mL/hr, while the explanted Codman-Hakim valve at the 120 setting ranged from 7.10 to 11.49 mL/hr (Figure 8). The increased variability and lower flow rates in the explanted valves suggest functional degradation over time, likely due to mechanical fatigue, protein buildup, or structural wear. The observed decline in flow consistency in explanted valves reinforces the need for improved long-term shunt designs to reduce failure rates and surgical revisions in hydrocephalus patients. The experiments confirmed that the new programmable shunt valves function correctly under controlled pressure conditions simulated in the laboratory setup. This supports the reliability of the devices at the point of initial implantation and suggests that manufacturer data accurately reflects real-world performance under model conditions. In contrast, the explanted (ex vivo) valves showed noticeable deviations in flow behavior. This study highlights the importance of continued innovation in valve design. Improving material durability and overall mechanical reliability could lead to longer lasting devices that maintain consistent performance in vivo. While new shunt valves are reliable at the time of implantation, long term use can lead to performance decline.

Acknowledgements and/or References (Optional): :