Combining Psychophysical and EEG Biomarkers for Improved Observation of Altered Nociceptive Processing in Failed Back Surgery Syndrome

Diagnosis and stratification of chronic pain patients is difficult due to a lack of sensitive biomarkers for altered nociceptive and pain processing. Recent developments enabled to preferentially stimulate epidermal nerve fibers and simultaneously quantify the psychophysical detection probability and neurophysiological EEG responses. In this work, we study whether using one or a combination of both outcome measures could aid in the observation of altered nociceptive processing in chronic pain. A set of features was extracted from data from a total of 66 measurements on 16 failed back surgery syndrome patients and 17 healthy controls. We assessed how well each feature discriminates both groups. Subsequently, we used a random forest classifier to study whether psychophysical features, EEG features or a combination can improve the classification accuracy. It was found that a classification accuracy of 0.77 can be achieved with psychophysical features, while a classification accuracy of 0.65 was achieved using only EEG features.Clinical Relevance-This study shows which combined features of nociceptive detection behavior and evoked EEG responses are most sensitive and specific to altered nociception in failed back surgery syndrome.