Multi-modal Quantitative Sensory Testing in Patients with Unilateral Chronic Neck Pain: An Exploratory Study

Objectives: The main objective of this study was to evaluate the pattern of altered pain processing in patients with chronic idiopathic neck pain, with particular emphasis on the interaction between pain sensitivity and modulation. Methods: This cross-sectional study systematically evaluates patients with unilateral chronic idiopathic neck pain using a comprehensive, multi-modal quantitative sensory testing [QST] protocol. Only patients with unilateral idiopathic neck pain present without radicular symptoms for more than six months were invited to participate. The QST measurements consists of pressure pain threshold testing, thermal threshold testing, electrical pain threshold testing, wind-up response testing using electrical stimulation, and measurement of descending inhibitory modulation using the Conditioned Pain Modulation paradigm. For a control group, we randomly selected age-and gender-matched control values from our center database consisting of reference values of 118 pain-free healthy volunteers. Results: Eighteen patients with unilateral neck pain participated in this study. The control group was represented by previously stored data from 18 demographically matched pain-free individuals. When data from the non-painful side and the non-painful reference area of the patients were compared with data from the pain-free healthy volunteers, we found preliminary evidence of 1. ongoing descending tonic inhibition, 2. less effective inhibitory modulation in the trigeminal compared to the spinal sensory system, and 3. segmental sensitization over the chronic nociceptive source in the neck. Conclusions: Using our multi-modal QST battery which incorporates dynamic and static tests, we demonstrate a possibly on-going interaction between intact descending inhibitory modulation and segmental sensitization in patients with chronic idiopathic neck pain. This enables not only better insight into the underlying neurophysiology but may also provide a means to better evaluate treatment and management interventions.