Understanding the multidimensional mechanisms of hypnotic analgesia

Abstract

AbstractPain is a multidimensional sensory experience, mainly based upon a three factorial model: sensory‐discriminative, motivational‐affective and cognitive. Each dimension of the pain experience is subserved by discrete neuroanatomical pathways and is apparently coded at different levels and sites of the central nervous system. An increasing body of evidence has shown that hypnosis can be effective in the down‐modulation of the pain sensation in both acute and chronic pain states. In acute pain, the effect of hypnotic analgesia is specific, positively correlated with hypnotic responsiveness and unrelated to endogenous opioid mechanisms. The neural mechanisms underlying hypnotic states and responses to hypnotic suggestions of analgesia remain largely unknown.On a psychophysiological basis, the neo‐dissociation theory by Hilgard and Hilgard (1994) has provided a heuristic framework to explain some aspects and apparent paradoxes of hypnotic analgesia. On neurophysiological grounds, recent evidence has shed, at least, some light on the mystery of pain relief in hypnosis. It is likely that hypnotic suggestions of analgesia may modulate pain processing at multiple levels and sites within the central nervous system. At the peripheral level, hypnosis may modulate nociceptive input by down‐regulating A delta and C fibres stimulation and reducing sympathetic arousal. At a spinal level, sensory analgesia during hypnosis has been shown to be linearly related to a reduction of the nociceptive flexion (RIII) reflex, a polysynaptic spinal reflex. At supraspinal cortical level, neuroimaging and electrophysiological studies have shown that hypnotic suggestions of analgesia can modulate directly both sensory and affective dimensions of the pain perception (the affective being reduced significantly more than the sensory), thus confirming, at least partially, the neo‐dissociation theory. Moreover, highly hypnotizable subjects possess stronger attentional filtering abilities than do low hypnotizable subjects. This greater cognitive flexibility might result in better focusing and diverting attention from the nociceptive stimulus as well as better ignoring irrelevant stimuli in the environment. Cognitive control processes are associated with a ‘supervisory attentional system’, involving the frontotemporal limbic cortices.Multiple, hierarchical pain control systems during hypnotic suggestions of analgesia provide a new description of the neurobiological basis of hypnotic analgesia, demonstrating specific patterns of peripheral and central activation associated with the hypnotic state and with the processing of hypnotic suggestions. Copyright © 2003 British Society of Experimental and Clinical Hypnosis