Risk of Infection After Local Field Potential Recording from Externalized Deep Brain Stimulation Leads in Parkinson's Disease

Objective

Adaptive deep brain stimulation (aDBS) controlled by local field potentials (LFPs) is considered a promising treatment for advanced Parkinson's disease (PD). The clinical research investigating aDBS functioning is performed using external deep brain stimulation (DBS) systems that require LFP recording through the temporary externalization of DBS leads. Although research examining LFP was first undertaken more than 20 years ago, only a few studies concern lead externalization and LFP recording safety. In the present retrospective study, we assessed the risk of infection related to these procedures.

Methods

A total of 105 patients with PD who underwent DBS surgery and lead externalization at our hospital from 2002 to 2014 were included in the present study. The medical records were used to collect clinical data and information concerning surgical site infections. We assessed the infection incidence in our cohort and the risk of infection related to the LFP recording procedure.

Results

The incidence of infections in patients who underwent lead externalization was 2.8%, which was consistent with the postoperative infectious risk reported in the literature (Wilcoxon signed rank test; P > 0.05). Moreover, the LFP recording procedure did not significantly increase the infection risk (LFP recordings vs. no LFP recordings: 2.5% vs. 4.2%; Fisher exact test; P > 0.05).

Conclusions

DBS lead externalization and LFP recording are safe and do not increase the postoperative infection risk in patients with PD who undergo DBS surgery. Our retrospective study supported further clinical research in the field of LFP-based aDBS.

Introduction

Adaptive deep brain stimulation (aDBS) controlled by local field potentials (LFPs) is considered to be one of the most promising approaches to optimize clinical benefits and limit the side effects of deep brain stimulation (DBS).1, 2, 3, 4, 5 aDBS consists of a closed-loop system designed to measure and analyze a control variable reflecting the patient's clinical condition to change online stimulation settings and send them to an intelligent implanted stimulator. LFPs, a sum of presynaptic and postsynaptic activities arising from large neuronal populations, have been shown to be a reliable and stable correlate of the clinical status in patients with Parkinson's disease (PD).4, 6, 7 LFP clinical correlations provide the rationale for developing and implementing new DBS devices able to adapt stimulation parameters moment by moment to the individual patient's needs using LFPs as a control variable for feedback. Despite the promising preliminary results obtained in primates,⁸ only 3 studies1, 2, 5 have tested the efficacy of LFP-related aDBS in clinical practice. The studies are performed using external systems that require the temporary externalization of leads to allow LFP recording. For more than 20 years, both lead externalization and LFP recordings have been performed to assess clinical9, 10 and research7, 9, 11 activities in several centers. However, despite the wide and long-lasting application of these procedures, only a few results concern the safety of these procedures.10, 12

Theoretically, lead externalization might increase the wound and DBS system infections through several mechanisms, such as skin erosion and contamination from skin flora (ie, handling of the implants by the patient). Moreover, temporary lead externalization extends the time interval between leads and implantable pulse generator (IPG) placement, thereby increasing the risk of infection.10, 12, 13 To the best of our knowledge, only 2 studies have reported the infection rate in patients who underwent lead externalization without finding an increased risk.10, 14 However, in these studies, the investigators did not assess the risk of infections related to LFP recordings.

Our group has long been involved in neurophysiological and clinical research on LFPs; however, the rate of infection had never been assessed in our cohort of patients with DBS.

Although the postoperative incidence of infections varies between studies from 1.5% to 15%,12, 13, 15, 16, 17, 18, 19, 20, 21, 22, 23 infections are one of the most common and severe complications after DBS surgery.10, 24 The development of hardware-related infections represents a significant threat and might lead to severe complications and might often necessitate removal of the implant.20, 24, 25

Because the clinical research on aDBS controlled by LFPs is progressively spreading, and lead externalization is needed for testing aDBS external devices, it seems necessary to verify whether LFP recording may be considered safe in clinical practice. The present study was designed to assess the incidence of infections retrospectively in a cohort of patients who underwent lead externalization and the risk of infection related to LFP recording procedure.