A novel human surrogate model of noninjurious sharp mechanical pain

Abstract

We propose a blade as a noninjurious nociceptive stimulus modeling sharp mechanical pain and yielding acute pain and hyperalgesia responses with closer proximity to incision-induced pain/hyperalgesia than punctate or blunt pressure mechanical pain models. Twenty-six healthy men and women were investigated to compare a small incision in the left forearm with noninvasive stimuli of different shapes and modalities to the right forearm. The magnitude and time course of incisional and blade-induced pain were assessed by numerical rating scales. Affective vs sensory components of pain experience were differentiated using a pain sensation questionnaire. The magnitude and time course of the axon reflex vasodilator response and of secondary hyperalgesia following a 7-second blade application were assessed. The maximum blade or incisional pain was similar (visual analogue scale [mean ± SD]: 32.9 ± 22.5 [blade] vs. 33.6 ± 29.8 [incision]), and both time courses matched closely in the first 10 seconds (paired t test; P = 0.5-1.0), whereas incision but not blade was followed by a second phase of pain, probably related to the tissue injury (decrease to half maximum pain 8 ± 2 vs. 33 ± 35 seconds; P < 0.01). Affective pain scores were significantly lower than sensory scores for all stimuli (P < 0.001). Comparing blade and incision, patterns of affective and sensory pain descriptors exhibited a remarkably similar pattern. Hence, we suggest the blade as novel model of sharp mechanical pain, which will be useful in investigating postoperative/mechanical pain and the role of self-injurious behavior in, eg, patients with borderline personality disorder.

Differential perception of sharp pain in patients with borderline personality disorder

“…Stimuli with bigger tip areas than pinpricks and sharp, but not skin‐piercing edges are needed to provide more spatial summation in exciting mainly A‐δ and C‐ fibre nociceptors (Slugg, Campbell, & Meyer, , Slugg, Meyer, & Campbell, ). When applied for 7 s in healthy subjects, this 4096 mN‐blade reached similar peak pain ratings as an incision—as a result of temporal summation during longer application; difference was only found in ratings for the late phase, most likely due to the release of cytokines triggering a “burning” sensation in incisional pain (Shabes et al, ).…”

“…After the diagnostic procedure conducted by clinically experienced interviewers, all patients included met the criteria for BPD according to the Diagnostic and Statistical Manual of Mental Disorders ( DSM, APA 2013) determined via the International Personality Disorder Examination ( IPDE ) (Loranger, ). A subsample of 22 female patients with BPD (mean age 30.45 ± 10.54 SD ) participated in this study and was compared to 20 female healthy controls who underwent the same testing protocol as described in “2.4 Experimental procedure” (Shabes et al, ) (comparison of healthy women to men; mean age 24.25 ± 4.68 SD ). Eleven i.e., 50% of the BPD patients represent a subsample of the patients with acute BPD who also took part in the study of Wills et al ().…”

“…Since in our previous study (Shabes et al, ) we found differential effects in different time windows following the incision or blade application, we separated the entire time course for the later analysis into shorter segments, accordingly. The first took 7 s (the duration of the actual incision until the scalpel or blade was withdrawn), the others 30 s each until the end of the pain experience.…”

“…However, one methodological problem for further analyses is the limitation to present a single incision stimulus during fMRI, where repetitive stimulation is required to increase signal strength for a more detailed examination of affected neuronal pain circuitries in BPD. Therefore, Shabes et al () established a non‐invasive surrogate model—the 0.1 × 4 mm non‐penetrating “blade” with a force of 4096 mN—offering a repeatable application of an incision‐like pain stimulus (Shabes et al, ).…”

“…We now examined the impact of tissue‐damage (“incision”) and application of the non‐invasive “blade” without specific stress induction regarding temporal pain aspects as well as subjective affective and sensory evaluations in detail in order to investigate whether there are differences in its processing within acute BPD patients and between patients and healthy controls. It was undertaken according to the experimental paradigm used for healthy participants before (Shabes et al, ) to test the following hypotheses: We expected the blade to be an adequate incision pain surrogate model in borderline patients with respect to intensity and quality. Patients with BPD differ from their healthy counterparts in lower pain ratings for different pain modalities. We expected to find reduced mechanical and thermal pain ratings within the same sample of BPD which was previously reported for separate patient groups for pinpricks (Magerl et al, ) and laser (Schmahl et al, ). Patients perceive and describe pain differently from their healthy counterparts—especially with respect to the sharp mechanical pain component, due to disturbances of affective and sensory processing with a) lower affective levels and b) less perception of the “sharp” component in BPD. …”