Background & Aims
Hyperpathia is defined by IASP as “A painful syndrome characterized by an abnormally painful reaction to a stimulus, especially a repetitive stimulus, as well as an increased threshold” .. The literature is sparse, and definitions are inconsistent focusing on either a steep stimulus-response curve or pain upon repetitive stimulation, and detection or pain thresholds (1). Hyperpathia is thus a poorly defined grouping of symptoms and signs, inconsistently including e.g. raised detection or pain threshold, delay, summation, explosive pain, aftersensation, hyperalgesia, and dysesthesia. Patrick Wall noted in 1984 that “we have to explain why these characteristics are grouped together” (2) and we still have not clearly defined the syndrome or related it to pathophysiological mechanisms Our objective was to identify clusters and characteristics of sensory signs previously included in the definition of hyperpathia in a heterogeneous population of patients with peripheral neuropathic pain.
Methods
Patients with peripheral neuropathic from two randomized controlled trials were included. Patients underwent a full quantitative sensory testing (QST) and a repetitive pinprick (RP) test, in which patients reported pain intensity every 10 seconds to 2Hz repetitive pinprick stimuli during 1 minute and until pain had ceased. Patients were grouped into four clusters based on results from the stimulus-response (SR) function of the QST, which assesses pain to seven pinprick stimuli of different intensities, and four clusters based on their RP-testing. The grouping was based on pain ratings, change in pain ratings, and for RP also aftersensations. The SR and RP clusters were compared and compared to other QST outcomes. Two clusters, cluster SR-A and RP-1 were defined as to best match the current definition of hyperpathia.
Results
We included 124 patients . SR-A were comprised of 11 patients, and from RP-clustering, RP-1 included 16 patients. Preliminary results show that despite a steep stimulus-response function in SRA and high pain scores and large increase in pain score to repetitive stimuli and aftersensations in RP1 there were no (n = 1) overlap and neither group were characterized by sensory loss but rather sensory gain. Data are being analyzed and will be presented at the conference.
Conclusions
Hyperpathia with hyperalgesia and increased thresholds seem rare in peripheral neuropathic pain. Final data are being analyzed and will be presented at the conference.
References
1. Helme RD, Finnerup NB, Jensen TS. Hyperpathia: “to be or not to be: that is the question”. Pain. 2018;159(6):1005-9.
2. Wall PD. The Hyperpathic Syndrome: A Challenge to Specificity Theory. In: von Euler C, Franzén O, Lindblom U, Ottoson D, editors. Somatosensory Mechanisms: Proceedings of an International Symposium held at The Wenner-Gren Center, Stockholm, June 8–10, 1983. Boston, MA: Springer US; 1984. p. 327-37.