Peripheral nerves connect and relay information between the central nervous system and its target organs. Small arteries traverse the epineurium and are responsible for supplying blood to the axons and cells within the nerves. Constriction or damage to these vessels can reduce perfusion leading to ischemic insults. Peripheral nerve electrostimulation has been approved for the treatment of epilepsy, depression and migraines, and is also being studied for the treatment of rheumatoid arthritis, Crohn’s disease, polycystic ovary syndrome, and type II diabetes. While the safety and efficacy of currently approved medical devices is well established, next generation devices may require novel stimulation parameters that pose additional risks. Therefore it is important to develop new methods to assess stimulation-induced nerve injury. To that end, we have begun to explore optical imaging based biomarkers, including optical coherence tomography angiography (OCT-A) to quantify changes in vascular morphology and blood flow during stimulation. We imaged the rat sciatic nerve in vivo with a 1300 nm OCT-A system. A 3-D printed nerve stabilizer with embedded platinum disc electrode was used to align the nerve for imaging during electrostimulation. Electrostimulation at either 40 or 400 µC/cm2 was applied for 1 hour. Images were acquired before, during and after stimulation. With higher electrostimulation parameters, blood vessels close to electrode site showed constriction. Immunohistochemical assessment was performed to correlate nerve injury to observed vascular changes. Optical imaging biomarkers have the potential to help assess the safety of novel electrodes and electrostimulation paradigms.
Srikanth Vasudevan, Ahhyun S. Nam, Benjamin J. Vakoc, and Daniel X. Hammer, "Optical coherence tomography angiography based biomarkers to assess the safety of peripheral nerve electrostimulation (Conference Presentation)," Proc. SPIE 10481, Neural Imaging and Sensing 2018, 1048115 (Presented at SPIE BiOS: January 31, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2291646.5751486722001.
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