892 Pain Intensity Is Characterized by Theta Band Dynamics and Opioid Pain Medication Effect at Gamma Band Dynamics Within the Human Subcortical Structures

Abstract

INTRODUCTION: Chronic pain is a multifaceted condition that involves processes of sensation, cognition, and emotion. Given its complexity, characterizing the dynamic changes in pain intensity for patients with chronic pain has remained a challenge. Several EEG studies have shown chronic pain patients to exhibit an increased theta and alpha band power, and acute pain to induce an increased gamma power. However, these do not inform the dynamical changes in pain fluctuations, and critically at the subcortical hubs that modulate the processes of sensation, cognition, and emotion. METHODS: The patients continuously rated their pain level for approximately 10 minutes, and we characterized the pain reduction that occurred spontaneously and that occurred via opioid pain medication. We used a novel method coined variance of auto-information (VAI), that would parameterize the stochasticity (i.e., randomness) of the theta and gamma bandpass filtered LFP. RESULTS: In all four patients, the theta VAI (randomness) was found to be lower as pain was relieved both spontaneously (p = 0.01) and via fentanyl (p = 0.03). The gamma VAI was higher when pain was relieved via fentanyl (p = 0.03). CONCLUSIONS: The results demonstrate characterizing pain intensity using the human neuronal oscillatory activity from the subcortical structures. We also introduce the VAI method that consistently characterize pain relief among chronic pain patients. These findings may help to identify biomarkers for pain intensity, and potentially guide stimulation targets for closed-loop neuromodulatory treatment.