Feasibility of endovascular stent-electrode array for minimally invasive high-fidelity chronic recordings of cortical neural activity

© 2016 Dr. Thomas James OxleyHigh-fidelity intracranial electrode arrays for recording and stimulating brain activity have facilitated major advances in the treatment of neurological conditions over the last decade. Traditional arrays require direct implantation into the brain via open craniotomy, which can lead to inflammatory tissue responses that may disrupt or reduce the ability to detect neural activity. Inspired by the long-term stability of devices implanted into blood vessels, including the artificial cardiac pacemaker, there is a need to develop minimally invasive approaches that avoid brain trauma. The variability in size and position of human superficial veins lying on cortical surface, internal lumen size and position in relation to motor and sensory cortex was assessed in 50 human MRI brain scans. The sheep brain was similarly mapped to establish a generalisable large animal model also using MRI brain scans. A technique to achieve access to the cerebral veins was then developed in a sheep model for cerebral venography using commercially available catheters. A novel self-expanding, nitinol stent was used as a scaffold to fabricate a platinum electrode array system that could be delivered through a telescoping catheter system and deposited immediately adjacent to motor area. Brain signal was recorded over a chronic time period involving resting EEG, somatosensory evoked potentials and endogenous modulations of cortical activity utilising volatile anaesthesia. This body of work has, for the first time, demonstrated the feasibility of chronically recording brain activity from within a vein in an animal model. A stent-electrode array (stentrode) capable of being implanted into a superficial cortical vein overlying motor cortex via catheter angiography was demonstrated to be robust in deployment. The stentrode incorporated into the vein wall within three weeks and demonstrated stable neural recordings in freely moving animals for up to 28 days. Complex impedance spectroscopy measurements demonstrated low frequency changes occurring over the first 6 days. Stentrodes implanted for 30 days demonstrated superior ability to detect cortical physiological modulations induced by volatile anaesthesia when compared to stentrodes implanted at Day 1. Spectral content and noise floor of vascular electrocorticography were comparable to that of an epidural array implanted via craniotomy. The stentrode may have wide ranging applications for the long-term treatment of neurological conditions. In particular, the access to the motor and sensory areas from cortical veins and sinuses lend its use to brain-machine interface systems for robotic motor prostheses. Other applications may include telemetry in epilepsy and deep brain stimulation