Methodological Considerations for the Temporal Summation of Second Pain

Abstract

Temporal summation of second pain (TSSP) is a psychophysical indication of a central pain encoding mechanism, potentially enhanced in pathological pain conditions. Low frequency repetitive stimulation of unmyelinated (C) nociceptors results in a progressive increase of pain intensity when thermal stimulation intensity remains constant. However, when using different methods of nociceptive delivery to the skin, both regularity and rate of pain enhancement with repetition varies between experiments. Specifically, repetitive ramping up and down from a neutral to a painful temperature has produced weak and inconsistent pain summation. In contrast, repetitive contact of the skin with a preheated probe has generated substantial pain summation. In the present study, TSSP by the intermittent contact (IC) with a preheated thermode and constant contact, ramp and hold (CC) methods were compared during 10 iterations of stimulation of glabrous skin of the hand or hairy forearm skin, with an onset to onset interval of 3.3 sec and stimulus interval of 0.8 sec. Significantly greater TSSP was observed for IC stimulation at both sites (p < .001). Differential activation of myelinated and unmyelinated nociceptors by ramping and tapping may account for different rates of temporal summation of heat pain. Perspective This article presents direct evidence suggesting the constant contact, ramp and hold stimulus may underestimate the level of Temporal Summation of Second Pain. This evidence suggests the re-evaluation of stimulation techniques utilized for Temporal Summation tests, especially within clinical models.

Transcutaneous electrical nerve stimulation (TENS): towards the development of a clinic-friendly method for the evaluation of excitatory and inhibitory pain mechanisms

“…However, in the literature, temporal summation is often assessed using a pulsed (as opposed to a continuous) stimulation. 25 , 44 Some authors 25 , 45 (but not all 46 ) have proposed that a constant stimulation may actually be less effective than an intermittent stimulation in evoking temporal summation.…”

Pressure pain threshold and temporal summation in adults with episodic and persistent low back pain trajectories: a secondary analysis at baseline and after lumbar manipulation or sham

“…TS is a measure of how much the severity of a painful stimulus changes when the stimulus is repeated with three second intervals or less at a testing site [10]. Pain severity typically increases with repeated stimuli in healthy individuals [10], though responses are known to vary between individuals [11] and protocols [12]. TS is thought to assess the physiological phenomenon of wind-up, where dorsal horn neurons become increasingly excited in response to repeated noxious stimuli in a short time frame [10].…”

Altered pain modulation to noxious heat thermal stimuli in burning mouth syndrome

“…TS of electrical painful stimulation has been demonstrated (Arendt‐Nielsen et al., 1995; Staud, Craggs, Robinson, Perlstein, & Price, 2007), and intra‐epidermal electrical stimulation (IES) has been developed to selectively activate the C fibers (Inui et al., 2002). This is relevant as low‐frequency, repeated stimulation of C fibers may result in pain enhancement (Eckert, Vierck, & Simon, 2017).…”