Deep brain stimulation hardware complications: The role of electrode impedance and current measurements.
Farris S, Vitek J, Giroux ML. (2008), Deep brain stimulation hardware complications: The role of electrode impedance and current measurements. , Mov Disord. 2008 Jan 9 [Epub ahead of print]
The authors of this study began by discussing the improvement of motor symptoms from DBS. However, as we know, this procedure may undergo changes in the level of motor control across time. They discussed that there may be various reasons that DBS changes in efficacy across time, including the hardware of the device itself. In a related finding by these authors, they looked at 466 patients across 7 years and found a rate of 8.1% of those patients had changes in their motor functioning as a direct result of hardware problems (e.g. battery failure, problems with the wires, or misplaced electrodes). They discussed the role of hardware complications as being very important as more and more people are undergoing this procedure and sadly there is little guidance from the manufacturers in regard to technical manuals and there are no strict clinical guidelines to follow in regard to hardware/patient management. The goal of their current study was to follow 4 patients that had hardware complications and how they were best managed for long term efficacy of DBS. The authors went into a great deal of specific stimulator settings (we refer the reader back to the original article for specifics as it is beneficial to read the entire article for related information past the scope of this review) and findings for each patient including a kink in a lead wire, wire fracture, internal wire abnormality, and gap in the wire insulation. It is notable that the patients had their DBS for less than 5 years and after finding hardware problems were treated by either stimulator parameter changes or surgery with resultant returned improvement in their motor symptoms. The authors noted that there are various reasons why a PWP may undergo changes in symptoms related to their PD (e.g. disease progression, hardware failures, medication changes, comorbid illnesses, etc.) but when their patients experienced an acute change in “significant tremor” they found hardware issues best explained these changes. They also noted that it is important to carefully look at the pattern of change in patients, including were there any preceding events that may have caused change (e.g. battery replacement, falls, etc.), what is the time course (e.g. acute or gradual), are the symptoms unilateral or bilateral, do the symptoms change with head or body positioning, is there an unusually short length of time before battery replacement (e.g. short in the wires), and what specific symptoms are increasing (e.g. tremor, paresthesia, surge sensations, etc.). The authors concluded that there should be various clinical protocols in place for medical management of PWP. As there are limited resources in this area for clinicians, the authors whom provide a great deal of patient care for PWPs, provided a “clinical pathway for DBS hardware monitoring” in an attempt to improve the medical management for other clinicians that may be struggling with similar hardware issues with their patients as well.