Effects of insertion conditions on tissue strain and vascular damage during neuroprosthetic device insertion

Abstract

Long-term integration of neuroprosthetic devices is challenged by reactive responses that compromise the brain-device interface. The contribution of physical insertion parameters to immediate damage is not well described. We have developed an ex vivo preparation to capture real-time images of tissue deformation during device insertion using thick tissue slices from rat brains prepared with fluorescently labeled vasculature. Qualitative and quantitative assessments of damage were made for insertions using devices with different tip shapes inserted at different speeds. Direct damage to the vasculature included severing, rupturing and dragging, and was often observed several hundred micrometers from the insertion site. Slower insertions generally resulted in more vascular damage. Cortical surface features greatly affected insertion success; insertions attempted through pial blood vessels resulted in severe tissue compression. Automated image analysis techniques were developed to quantify tissue deformation and calculate mean effective strain. Quantitative measures demonstrated that, within the range of experimental conditions studied, faster insertion of sharp devices resulted in lower mean effective strain. Variability within each insertion condition indicates that multiple biological factors may influence insertion success. Multiple biological factors may contribute to tissue distortion, thus a wide variability was observed among insertions made under the same conditions.

FEF inactivation with improved optogenetic methods

“…Previous attempts to address one of these concerns have come at the expense of the other. Bundles of fibers illuminate larger volumes, but the increased penetration diameter leads to greater tissue and vascular damage, because the damage is proportional to fiber diameter (19,(44)(45)(46)(47)(48). Tapered glass fibers reduce penetration damage, but narrowly focus light to tiny illumination areas (<100 μm 2 ) (13,49).…”

State-of-the-art MEMS and microsystem tools for brain research

“…Important components of the adverse response have been studied, including insertion trauma [87][88][89] , the intrinsic foreign body response 90,91 , and straininduced damage from mechanical mismatch [92][93][94] . Long-term reliability is clearly more of a challenge in clinical applications than for neuroscience; nonetheless, tools for brain mapping should be designed to minimize disruption to the circuits being investigated.…”

“…The mean distance from the center of a neuron (somatic center) to the nearest microvasculature is only 15 μm (Ref. 95); thus, regional damage to the blood-brain barrier is unavoidably a function of size 88 . The intrinsic foreign body response is complex and intertwined with the issue of micromotion, which is related to mechanical factors such as the probe cross-sectional area, lattice or porous architecture, total surface area, and stiffness.…”

Implanted intracortical electrodes as chronic neural interfaces to the central nervous system

“…However, depending on the skill of the surgeon, among other factors, there may still be a resultant injury. Few in depth studies have been done about every type of system and surgical method, but from the available literature [71,72,73] it is clear that there is always tissue damage incurred during insertion of devices due to the invasive nature of the technique. Bjornsson et al [73] demonstrate a direct correlation between the amount of damage and the speed of insertion, again indicating that faster insertion results in less damage.…”

“…Few in depth studies have been done about every type of system and surgical method, but from the available literature [71,72,73] it is clear that there is always tissue damage incurred during insertion of devices due to the invasive nature of the technique. Bjornsson et al [73] demonstrate a direct correlation between the amount of damage and the speed of insertion, again indicating that faster insertion results in less damage. While seemingly no studies have yet been done on the effects of this damage on the typical function of the affected area of the brain, the resiliency of the brain suggests that alternative neural pathways can be used to compensate for minimal damage.…”