Impedance Changes Indicate Proximal Ventriculoperitoneal Shunt Obstruction <italic>In Vitro</italic>

Abstract

Extracranial cerebrospinal fluid (CSF) shunt obstruction is one of the most important problems in hydrocephalus patient management. Despite ongoing research into better shunt design, robust and reliable detection of shunt malfunction remains elusive. The authors present a novel method of correlating degree of tissue ingrowth into ventricular CSF drainage catheters with internal electrical impedance. The impedance based sensor is able to continuously monitor shunt patency using intraluminal electrodes. Prototype obstruction sensors were fabricated for in-vitro analysis of cellular ingrowth into a shunt under static and dynamic flow conditions. Primary astrocyte cell lines and C6 glioma cells were allowed to proliferate up to 7 days within a shunt catheter and the impedance waveform was observed. During cell ingrowth a significant change in the peak-to-peak voltage signal as well as the root-mean-square voltage level was observed, allowing the impedance sensor to potentially anticipate shunt malfunction long before it affects fluid drainage. Finite element modeling was employed to demonstrate that the electrical signal used to monitor tissue ingrowth is contained inside the catheter lumen and does not endanger tissue surrounding the shunt. These results may herald the development of "next generation" shunt technology that allows prediction of malfunction before it affects patient outcome.

Enhanced intrathecal drug dispersion achieved by high volume injection and natural micromixing

“…Complex flow and mixing patterns observable are absent in idealized annular models lacking spinal microanatomy [3], [26], [27], thus failing to boost the effective dispersion of IT injected tracers as this is the case when microanatomical features are present (see Appendix B). The results of this study provide further evidence for the significant impact of microanatomical features on the spatial and temporal dispersion patterns of IT administered solutes shown previously [11].…”

“…Deformable fluid-filled spaces in the present bench test analog of the human CNS are fully enclosed between the soft dura/parenchyma surfaces and a distensible vascular interface (cranium vault with distensible vascular balloon) without leaving open system boundaries. The proposed configuration approximates the anatomy and fluid structure interaction dynamics of the spinal SAS, so we have confidence that it reproduces the complex geometry induced CSF mixing patterns that were reported in previous work using direct numerical simulation of spinal CSF flow [11]. The CNS model also incorporates microanatomical features of a spinal cord, epidural space and peripheral nerve root bundles, especially, which are critical geometric aspects implicated with enhanced mixing of fluid layers in the spinal SAS leading to accelerated drug dispersion.…”

“…Localized and interspersed eddies were observed in the flow directly upstream and downstream of cylindrical peripheral nerve root bundles suspended in the flow (see video in supplementary information). Moreover, trabeculae can substantially enhance this effect as reported in [11].…”

“…In this paper, we will present parametric studies of IT infusion experiments in a subject-specific anatomically accurate 3D printed transparent replica of the human spinal subarachnoid spaces (SAS) with natural CSF pulsations within the physiological range of spinal fluid amplitude and frequency [11]. High-speed video recording enabled accurate observation of spatiotemporal dispersion patterns of tracers during high-volume IT injection and subsequently in the post infusion phase due to natural CSF oscillations.…”

Piezoresistor-Embedded Multifunctional Magnetic Microactuators for Implantable Self-Clearing Catheter

“…Several groups proposed novel impedance-based sensors to monitor catheter obstruction [13], [14]. Similar impedance-based sensing may be used to determine whether the microactuator cleared the catheter obstruction.…”