Abstracts

Rationale: The NeuroPortTM (Cyberkinetics Neurotechnology Systems, Inc.) electrode system includes a grid of 96 silicon microelectrodes, allowing for chronic monitoring of local field potentials (LFP) or single-unit activity. The electrode is attached by a gold microwire to a connection “pedestal” which is fixed to the skull and externalized through the scalp. We describe our surgical experience with the short-term implantation of the NeuroPortTM electrode in a group of epileptic patients, undergoing craniotomy for subdural grids in pre-resection epilepsy monitoring, and suggest implications for the next generation of this device.Methods: Eight patients were implanted, six for semichronic recording and two for isolated intraoperative recording. Electrodes were placed per company specifications in cortex adjacent to the subdural electrode array. The pedestal was generally brought through the scalp in the incision line, although a separate stab incision was fashioned in some patients. Electrodes were removed intraoperatively during explantation of subdural electrodes; in three cases implanted cortex was isolated and processed for histopathological analysis.Results: Successful implantation was achieved in all patients. Some technical difficulty was encountered during implantation due to torsional memory of the wire. Robust LFP and single-unit recordings were obtained from all individuals; signals were durable throughout the monitoring period in most patients, although loss of signal was experienced in several patients due to fluid accumulation at the site of external pedestal connection. There were no neurological complications associated with either electrode implantation or prolonged monitoring. There was no clinically significant bleeding associated with electrode implantation, although subpial hemorrhage was noted at the time of implantation in several patients. There were no infections. Two patients developed post-resection complications with wound healing at the pedestal site, one of which requiring wound revision. Histopathologic examination demonstrated preserved neuronal architecture and minimal gliosis.Conclusions: Although clinically significant infection or CSF leak were not encountered, the large profile of the pedestal resulted in suboptimal wound healing in several patients. Also, the bulky cable connection to the pedestal was somewhat uncomfortable. We expect that this problem will be solved by conversion of the pedestal to a compact wire below the scalp utilizing an exiting electrode wire, similar to current subdural electrodes, or a wireless transmission system. Similarly, the moderate difficulty we encountered in manipulation of the gold wire connection could be eliminated by developing a wire without strong memory/torsion. However, our initial experience with the short-term use of the NeuroPortTM electrode suggests that the device can be used safely for short-term implantation in patients undergoing craniotomy for pre-resection epilepsy monitoring and that high quality recordings can be obtained.