Electrode dysfunctions in patients with deep brain stimulation: a clinical retrospective study

Electrode fractures are known hardware problems in patients with deep brain stimulation (DBS) and require surgical revision. Short circuits, loose connections or disconnections of only single contacts of the common quadripolar stimulation electrodes are more subtle dysfunctions and can result in decreased efficacy of DBS. Measuring the impedances of electrodes helps detect such technical dysfunctions. This study evaluates the frequency and clinical implications of abnormal impedance measurements. We retrospectively analyzed findings of systematic impedance checks in 591 consecutive patients with DBS for various movement disorders treated in our DBS center between 2005 and 2010. A technical dysfunction was found in 36 out of 1,142 electrodes (3.2%). Short circuits (22 electrodes) were more frequent than disconnections of single contacts (8 electrodes) or loose contacts (6 electrodes). Moreover, after 109 replacements of impulse generators another 16 electrodes revealed technical dysfunctions, again with short circuits (9 electrodes) exceeding disconnections of single contacts (5 electrodes) and loose contacts (2 electrodes). Most of the short circuits occurred immediately after surgical interventions. In contrast, among dysfunctions occurring later during long-term DBS, disconnections and loose contacts prevailed. Surgical revision was performed in 4 of the overall 52 electrodes with dysfunctions, whereas in the other electrodes adjustment of stimulation parameters resulted in stable and satisfying symptom control. Technical dysfunctions of stimulation electrodes or extension leads are rare but important sources of unsatisfying DBS efficacy. In the majority of cases DBS programming or reprogramming allows avoiding surgical revision.