Leveraging the Effect of Block Width during Infrared Neural Inhibition to Reduce Peak Temperatures

Abstract

Chronic pain has a diverse set of causes and can manifest in many forms. Often times the pain becomes no longer a symptom but a disease itself, necessitating treatments which rely on direct control of neurons. Infrared neural inhibition (INI) is a spatially precise optical form of neural inhibition which does not require contact with the tissue nor the introduction of exogenous agents. INI is believed to function through neural heat block mechanisms, elicited by heating due to water’s absorption of infrared (IR) light. While a threshold temperature rise is required for INI, it is shown that the length of axon targeted (block width) plays a role in determining the temperature required for inhibition. This was confirmed by showing lower temperature rises when using two adjacent optical fibers as opposed to a single fiber for light delivery. Previous implementation of INI induces temperature rises safe for acute inhibition, but problematic for sustained use in the clinic. By leveraging the effect of block width, the application of IR light for INI can be optimized for minimal temperature rise increasing feasibility for its translation to the clinic for pain inhibition.