Design of a validation sensor for pressure monitoring of implantable cuff electrodes for neurostimulation

Details

Supervisors

Doguet, Pascal ; Ronsse, Renaud

Faculty

Ecole polytechnique de Louvain

Degree label

Master [120] : ingénieur civil biomédical

Abstract

Neurostimulation through electrodes is a powerful technique which can help patients suffering from different diseases: epilepsy, chronic pain, headaches, etc. For instance in some cases of chronic epilepsy, the vagus nerve is stimulated electrically which helps the management of seizures. An example of neurostimulation is the case of Peripheral Nerve Stimulation, where electrodes have to be placed on peripheral nerves and they are normally kept in place thanks to a cuff. Spiral cuffs, studied in this thesis, are small sheets of silicon curled in a spiral which are wrapped around the peripheral nerve by the neurosurgeon during the implant surgery. The cuff electrode-nerve interface needs to fulfil many biocompatibility requirements; one of these specifications is ensuring that the cuff pressure exerted on the nerve does not strangle the nerve. Studies show that above a certain pressure, set between 20 and 30mmHg, cuffs irreversibly damage the nerve around which they are applied. As the applied pressure strongly depends on the cuff design, there is great need of a tool, i.e. a pressure sensor, capable of measuring the pressure exerted by different cuffs. In particular, this tool should be able to compare different designs and find which damage the nerve less, by evaluating the pressure applied on it. The instrument would therefore be used in the validation phase of the design of a cuff. The main objective of this thesis is to identify the requirements that the pressure sensor should fulfil, design a solution, manufacture it and calibrate it using known pressures. A second objective is to characterise different cuffs, some of which are manufactured by us and others bought from CorTec and then test them on the newly developed pressure sensor. Finally, the pressure sensor should detect whether a certain cuff is able to adjust its grip on the nerve, once this has increased its diameter due to inflammation. In other words the pressure sensor should have the ability to increase the nerve diameter so that the self-sizing cuff adaptability can be tested. The present thesis includes extensive experimental work and all experiments were performed within Synergia Medical.