Technical analysis of dual channel pulse generators used in deep brain stimulation; a safety evaluation.

Background: A sudden failure of implantable pulse generators (IPG) occurred in 15 out of 143 units during the last 4 years in our patients. This corresponds to a failure rate of 10.5%. In all cases, the connection between the causes of battery and electronic circuit was found defective in the destructive analysis. In order to better understand the failure causes we proceeded to an analysis of explanted IPGs which had reached their normal life span due to depletion of the battery.
Method: A functional test and an intensive destructive analysis were carried out in 14 units. The internal parts of the IPG were inspected by light and electron microscopy.
Findings: Deformations of the connection between battery and electronic circuit could be found in 12 out of 14 IPGs. The epoxy bonds, which achieve the mechanical fixation between the two contact areas of the bond wires, were found separated in 86%. Additionally, in six out of 14 devices the bond wires were either found lifted or with cracks as a sign of material fatigue.
Conclusion: Based on these results we conclude that the IPGs of the affected series did have a technical weak spot. We presume that this issue appears systematically and not randomly or triggered by an unusual action of the patient.