Sudden failure of dual channel pulse generators

We report a series of four sudden hardware failures in dual channel pulse generators implanted for chronic stimulation of the subthalamic nucleus in the treatment of Parkinson's disease. In all cases, a sudden and severe deterioration of the patient's neurological condition occurred with symptoms similar to those present before surgery. In all cases, destructive analysis of the generator revealed a fracture of the wire bonds connecting the battery to the hybrid (electronic) part of the pulse generator. This fracture led to repeated Power On Resets, bringing the parameter settings back to default (factory settings). As a cause, we propose that relative movements between the hybrid and the battery led to low cycle fatigue fractures due to insufficient stiffness of the device. That three of four failures occurred when the implant was in the infracostal region makes it likely that the fractures depend on the mechanical stress applied to the device. The efficacy of the therapy resumed immediately after device replacement. As a corrective measure, the manufacturer has added epoxy between both components, increasing significantly the stiffness of the device.