Hyperalgesia and Central Sensitization in Subjects With Chronic Orofacial Pain: Analysis of Pain Thresholds and EEG Biomarkers

Abstract

Introduction: The presence of a temporomandibular disorder is one of the most frequent causes of orofacial pain (OFP). When pain continues beyond tissue healing time, it becomes chronic and may be caused, among other factors, by the sensitization of higher-order neurons. The aim of this study is to describe psychological characteristics of patients with chronic OFP, their peripheral pain threshold, and electroencephalography (EEG) recording, looking for possible signs of central sensitization (CS). Materials and methods: Twenty-four subjects with chronic OFP caused by temporomandibular disorder were evaluated using the Research Diagnostic Criteria for Temporomandibular Disorders Axis I and Axis II. Pain intensity, catastrophizing, and presence of CS were assessed through self-reported questionnaires. Pressure pain threshold (PPT) was recorded in facial and peripheral sites; EEG activity was recorded during open and closed eyes resting state and also during the pain threshold assessment. Pain thresholds and EEG recordings were compared with a cohort of pain-free age- and sex-matched healthy subjects. Results: Patients with chronic OFP showed a significant reduction in their pain threshold compared to healthy subjects in all sites assessed. Greater reduction in pain threshold was recorded in patients with more severe psychological symptoms. Decreased alpha and increased gamma activity was recorded in central and frontal regions of all subjects, although no significant differences were observed between groups. Discussion: A general reduction in PPT was recorded in people who suffer from chronic OFP. This result may be explained by sensitization of the central nervous system due to chronic pain conditions. Abnormal EEG activity was recorded during painful stimulation compared to the relaxed condition in both chronic OFP subjects and healthy controls.

Association of temporomandibular disorders with pain sensitivity: A cohort study

“…The present findings regarding the association of pain sensitivity with TMD may be linked to central sensitization (CS). This originates from alterations in neurons, nociceptive pathways and functions of the CNS, causing pain to be uncoupled from noxious stimuli (Baroni et al., 2020; Latremoliere & Woolf, 2009). CS can induce an exaggerated reaction to stimuli that would normally not lead to pain and has been reported to have a role in several conditions, including rheumatoid arthritis, osteoarthritis, TMD, fibromyalgia and neuropathic pain (Baroni et al., 2020; Woolf, 2011).…”

“…This originates from alterations in neurons, nociceptive pathways and functions of the CNS, causing pain to be uncoupled from noxious stimuli (Baroni et al., 2020; Latremoliere & Woolf, 2009). CS can induce an exaggerated reaction to stimuli that would normally not lead to pain and has been reported to have a role in several conditions, including rheumatoid arthritis, osteoarthritis, TMD, fibromyalgia and neuropathic pain (Baroni et al., 2020; Woolf, 2011). CS may sometimes be triggered by a peripheral injury or dysfunction, such as chronic TMD, with muscular/TMJ‐dysfunctions working as peripheral triggers.…”

Algometer Assessment of Pressure Pain Threshold After Onabotulinumtoxin-A and Physical Therapy Treatments in Patients With Chronic Migraine: An Observational Study

“…Clinically, alterations in descending pain inhibition manifest through widespread pressure hyperalgesia (2,6,7). Indeed, several studies identify lower pressure pain threshold (PPT) in the trigeminocervical complex and throughout the body in patients with chronic migraine with respect to that identified in the same muscles in healthy controls (8)(9)(10)(11). These studies also show lower PPT in female patients with respect to male patients, while no difference was observed between episodic and chronic forms, between migraine and tension-type headache, or between symptomatic and non-symptomatic sides.…”

The Effect of Spinal Muscle Fatigue and Psychosocial Factors on Pressure-Pain Threshold in Healthy Adults

“…Pain sensitivity can be assessed using the measurement of pressure-pain threshold (PPT). Tis is a simple quantitative sensory test of pain that is often used in research and clinical practice [1][2][3][4]. Te PPT is defned as the minimum pressure applied to anatomical site that results in an individual perceiving the mechanical stimulus as pain [5].…”