Comparative analysis of explanted DBS electrodes.

Background: Hardware-related complications frequently occur in deep brain stimulation. Microscopy and spectroscopy techniques are effective methods for characterizing the morphological and chemical basis of malfunctioning DBS electrodes. A previous report by our team revealed the morphological and chemical alterations on a malfunctioning explanted electrode when it was compared to a new device. The aim of this preliminary study was to verify whether these morphological and chemical alterations in the materials were a direct result of the hardware malfunctioning or if the failure was correlated to a degradation process over time.

Methods: Two DBS electrodes were removed from two patients for reasons other than DBS system impairment and were analyzed by a scanning electron microscope and by an energy-dispersive X-ray spectroscopy. The results were compared to a malfunctioning device and to a new device, previously analyzed by our group.

Results: The analysis revealed that the wear of the polyurethane external part of all the electrodes was directly correlated with the duration of implantation period. Moreover, these alterations were independent from the electrodes functioning and from parameters used during therapy.

Conclusions: This is the first study done that demonstrates a time-related degradation in the external layer of DBS electrodes. The analyses of morphological and chemical properties of the implanted devices are relevant for predicting the possibility of hardware's impairment as well as to improve the bio-stability of DBS systems.