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

Abstract

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.

The Relationship between Nociceptive Detection Thresholds and Pressure- and Electrical Pain Thresholds: An Explorative Study in Rheumatoid Arthritis Patients

“…As compared to age-and sex matched HC, in RA patients we observed higher NDTs to both single-and double pulse stimuli, and lower slopes to SP stimuli. Other studies in patient groups with the same method have been able to make similar observations, yet with a lower slope in response to both the single-and double pulse stimuli [17,18]. While more research is required to understand these differences, factors which are known to contribute differentially to the SP slope as compared to the DP slope, are the peripheral-and central sensitivity of the nociceptive function [10], as well as the internal criterion [26].…”

“…This is in contrast to PT measurements, which -upon strictly following a test protocol -are widely thought to predominantly reflect characteristics of nociceptive (dis)function that are relevant for the development and maintenance of chronic pain syndromes [22]. In multiple studies which have evaluated NDTs, interesting and relevant results using pain models [11][12][13][14][15]23] or patient groups [16][17][18][19]24] are obtained, but few studies have yet evaluated factors affecting the NDT outcomes. One factor which is well-known to affect the outcomes of NDT measurements, is the electrocutaneous interface [25].…”

“…NDTs have been evaluated and often also shown effects in multiple studies in which human pain models are used, such as capcaisin [11], lidocaine [12], sleep deprivation [13], a cold pressor test (CPT) [14] and high frequency stimulation (HFS) [15]. Lately, NDTs have also been successfully evaluated in a clinical setting such as in patients with small fiber neuropathy [16], (painful) diabetic neuropathy [17], failed back surgery syndrome [18], or neuropathic pain [19], whereby often higher NDTs were observed in the patient groups. These findings indicate that NDTs can measure characteristics of the nociceptive system, of which it is at present unknown to what extent these characteristics are relevant for the development and maintenance of chronic pain syndromes.…”

“…Correlation coefficients made bold are statistically significant with a p<0.0001. Sup = Supraspinatus; Epi = Epicondyle 18,24],. suggest that NDT outcomes are also sensitive to changes in central nociceptive functioning.…”

Exploring Psychophysical and Neurophysiological Responses to Intra-Epidermal Electrical Stimuli in Patients With Persistent Spinal Pain Syndrome Type 2 with a Spinal Cord Stimulator

“…Previous laboratory experiments used IES of the dorsum of the hands (i.e., C7 dermatome) in healthy subjects [14,15]. Hence, clinical feasibility studies explored NDT-EP phenomena using IES performed on (non-painful) hands of patients (e.g., with PSPS-T2), which showed altered task performance compared to pain-free controls [16,17]. However, it is uncertain whether altered detection task performance in patients was related to nociceptive dysfunction.…”