Tactile Precision Remains Intact When Acute Neck Pain Is Induced

Abstract

A growing body of evidence suggests that chronic pain is associated with perceptual changes, such as impaired tactile acuity and laterality judgements. A recent study on low back pain showed that tactile acuity was decreased immediately after acute pain induction. Biologically, acute pain should lead to enhanced rather than disruptive changes in tactile acuity to meaningfully respond to potentially damaging nociceptive stimuli. In this double-blinded experiment, 30 healthy volunteers attended 3 experimental sessions (injection, sham injection, and control condition) separated by 1 week each, to investigate the effect of acute nociception on tactile precision and laterality judgements. In the real injection condition, acute pain was induced by hypertonic saline solution injected into the mid portion of the trapezius muscle. Tactile acuity (2-point discrimination and an estimation task) and laterality judgements were measured before and during pain perception. In the sham condition, the injection was mimicked by a sham procedure (without piercing the skin), and in the control condition no intervention took place. Results showed that tactile acuity remained intact (P = .92), indicating that experimentally induced neck pain did not affect tactile precision. The time needed to complete the laterality judgement task improved over time in all conditions, reflecting a learning effect (P = .05). We conclude that acute neck pain does not result in perceptual distortions, possibly reflecting a higher protection demand for the neck, a body region in close anatomic proximity to neural centers responsible for vital functions. These data-in the context of existing evidence-indicates that tactile acuity may respond differently to noxious stimulation in different anatomic regions. PERSPECTIVE: In this study, a sensory adaptation to acute neck pain was investigated. It was found that experimental neck pain did not elicit changes in the sensory axis, leaving tactile acuity intact in otherwise healthy participants. These data support site-specific sensory adaptation to pain.

Keywords: Two-point discrimination; experimental pain; nocebo effect; sensory dissociation; tactile acuity; touch-gate.