893 Psychophysical Pain Encoding in the Cingulate Cortex Predicts Responsiveness of Electrical Stimulation

INTRODUCTION: The anterior cingulate cortex (ACC) plays an important role in pain's cognitive and emotional processing. Prior studies have used deep brain stimulation (DBS) to treat chronic pain, but results have been inconsistent. This may be due to network adaptation over time and variable causes of chronic pain. Identifying patient-specific pain network features may be necessary to determine patients' candidacy for DBS. METHODS: Four patients who underwent intracranial monitoring for epilepsy (stereo-electroencephalography) participated in a pain task. Subjects placed their hand on a device capable of eliciting thermal pain for five seconds and rated their pain. Current-controlled biphasic trains of electrical stimulation were applied to a random subset of trials for each subject. Thermal pain thresholds with and without electrical stimulation were determined. To evaluate whether patients had neural activity susceptible to modulation, generalized linear mixed-effects models assessed the relationship between broadband high-frequency local field potential amplitude within the cingulate cortex (HFA; 70-150 Hz) and the resulting psychophysical pain evaluations. RESULTS: The pain threshold for each patient was determined from the psychometric probability density function. Two patients had a higher pain threshold with stimulation than without, while the others had no difference. We also evaluated the relationship between neural activity and pain responses. We found that patients who responded to stimulation had specific time windows where high-frequency activity was associated with increased pain ratings. CONCLUSIONS: Stimulation of cingulate regions with increased pain-related neural activity was more effective at modulating pain perception than stimulating non-encoding regions. Personalized evaluation of neural activity biomarkers could help identify the best target for stimulation and predict its effectiveness in future studies evaluating DBS.