Low intensity ultrasound for suppression of peripheral nerve activity

Abstract

Pain is commonly defined as “an unpleasant sensory and emotional experience that is associated with actual or potential tissue damage”, yet physiologically, pain is simply a high frequency or high intensity stimulus in the nervous system. Research has shown that pain can be lessened by electrically stimulation specific regions in the central or peripheral nervous system. Electrical stimulation of the nervous system emerged as a clinically approved stimulating modality. This modality was successful in reducing symptoms but caused the formation of scar tissue. Therefore, considering new modalities became necessary to replace electrical stimulation. Over the years, ultrasound technology gained a major role in diagnostics and therapeutics. The broad range of intensities and frequencies of ultrasound signals, and the ability of their beams to be focused to propagate deeply through tissues into small scale targets non-invasively, made ultrasound technology very interesting for healthcare applications. In this work, the interest is in low intensity low frequency ultrasound stimulation of the peripheral nervous system that neuromodulates the behavior of neural networks and decreases pain sensation. The aim of the project is to study the effect of ultrasound stimulation on certain pain pathways in the peripheral nervous system, namely the reflex arc. Ultrasound stimulation is applied via an immersible transducer targeting the sciatic nerve in the Sprague Dawley rat animal model. The stimulation showed a decrease in the activity of the gastrocnemius muscle controlled by the sciatic nerve, and thus reduction of pain sensation. The mechanism of action of this mechanical stimulation modality remains unknown which channels our focus on developing a mechanical model that incorporates ultrasound stimulation into the existing electrical model of Hodgkin and Huxley for neural excitation. Mechanical forces including mechanical tension induced due to ultrasound stimulation, mechanical tension due to membrane voltage va