Comparison of anti-siphon devices—how do they affect CSF dynamics in supine and upright posture?
Three different types of anti-siphon devices (ASDs) have been developed to counteract siphoning-induced overdrainage in upright posture. However, it is not known how the different ASDs affect CSF dynamics under the complex pressure environment seen in clinic due to postural changes. We investigated which ASDs can avoid overdrainage in upright posture best without leading to CSF accumulation.
Three shunts each of the types Codman Hakim with SiphonGuard (flow-regulated), Miethke miniNAV with proSA (gravitational), and Medtronic Delta (membrane controlled) were tested. The shunts were compared on a novel in vitro setup that actively emulates the physiology of a shunted patient. This testing method allows determining the CSF drainage rates, resulting CSF volume, and intracranial pressure in the supine, sitting, and standing posture.
The flow-regulated ASDs avoided increased drainage by closing their primary flow path when drainage exceeded 1.39 ± 0.42 mL/min. However, with intraperitoneal pressure increased in standing posture, we observed reopening of the ASD in 3 out of 18 experiment repetitions. The adjustable gravitational ASDs allow independent opening pressures in horizontal and vertical orientation, but they did not provide constant drainage in upright posture (0.37 ± 0.03 mL/min and 0.26 ± 0.03 mL/min in sitting and standing posture, respectively). Consequently, adaptation to the individual patient is critical. The membrane-controlled ASDs stopped drainage in upright posture. This eliminates the risk of overdrainage, but leads to CSF accumulation up to the volume observed without shunting when the patient is upright.
While all tested ASDs reduced overdrainage, their actual performance will depend on a patient’s specific needs because of the large variation in the way the ASDs influence CSF dynamics: while the flow-regulated shunts provide continuous drainage in upright posture, the gravitational ASDs allow and require additional adaptation, and the membrane-controlled ASDs show robust siphon prevention by a total stop of drainage.
KeywordsAnimal testing alternatives Anti-siphon device Cerebrospinal fluid shunt In vitro Overdrainage Posture
Compliance with ethical standards
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no personal or institutional conflict of interest.
The Swiss Academy of Engineering Sciences provided financial support through the grant 2014–080, the 3R Research Foundation provided financial support through the grant 140–14, and the Swiss National Science Foundation provided financial support through NCCR Kidney.CH. The tested shunts were provided by the respective manufacturers.
The sponsors had no role in the design or conduct of this research.
- 3.Bergsneider M, Yang I, Hu X, McArthur DL, Cook SW, Boscardin WJ (2004) Relationship between valve opening pressure, body position, and intracranial pressure in normal pressure hydrocephalus: paradigm for selection of programmable valve pressure setting. Neurosurgery 55(4):851–859CrossRefPubMedGoogle Scholar
- 13.Freimann FB, Kimura T, Stockhammer F, Schulz M, Rohde V, Thomale UW (2014) In vitro performance and principles of anti-siphoning devices. Acta Neurochir 156(11):2191–2199Google Scholar
- 15.Gehlen M, Kurtcuoglu V, Schmid Daners M (2017) Is posture-related craniospinal compliance shift caused by jugular vein collapse? A theoretical analysis. Fluids and Barriers of the CNS 14(1)Google Scholar
- 20.Qvarlander S (2013) Analysis of ICP pulsatility and CSF dynamics: the pulsatility curve and effects of postural changes, with implications for idiopathic normal pressure hydrocephalus. PhD thesisGoogle Scholar
- 21.Qvarlander S, Lundkvist B, Koskinen L-OD, Malm J, Eklund A (2013) Pulsatility in CSF dynamics: pathophysiology of idiopathic normal pressure hydrocephalus. J Neurol Neurosurg Psychiatry 84(7):735–741Google Scholar
- 22.Qvarlander S, Sundstrom N, Malm J, Eklund A (2013) Postural effects on intracranial pressure: modeling and clinical evaluation. J Appl Physiol 115(10):1474–1480Google Scholar
- 23.United States. National Aeronautics and Space Administration (1995) Man-systems integration standards. Number Bd. 3 in NASA-STD. National Aeronautics and Space AdministrationGoogle Scholar