A simple method of investigating implanted neurostimulator faults

Aim of Investigation: Measurement of the skin stimulus artefact produced by implanted devices is an essential technique in the non-invasive determination of neurostimulator faults. This paper describes an implant tester designed to provide a quick and simple method of measuring stimulus artefacts at the skin and assesses its performance in diagnosing faults in 17 implanted systems.

Method: The implant tester consisted of a small differential pre-amplifier with a built-in array of three electrodes, suitable for recording from the skin. The output from the implant tester can be connected directly to an oscilloscope for measurement of the stimulus artefact.
17 patients referred due to unsatisfactory stimulation following implantation of a neurostimulating device have been investigated using the implant tester. The investigation procedure will be described in detail.

Results: Of the 17 patients tested, the diagnosis of the fault made with the implant tester proved correct on clinical follow-up in 9 cases, incorrect in 1 case and 7 diagnosis have yet to be followed-up. The most common faults were receiver failure (3) and inadequate electrode position (2).

Conclusion: The implant tester has proved to be a reliable tool in diagnosing stimulator faults and has indicated a suitable clinical action to be taken.