Hypno-Analgesia and Acupuncture Analgesia: a Neurophysiological Reality?

The effects of hypnosis, acupuncture and analgesic drugs on the subjective experience of pain and on objective neurophysiological parameters were investigated. Pain was produced by brief electric stimuli on the wrist. Pain challengers were: hypnosis (induced by two different video tapes), acupuncture (at specific and unspecific loci, with and without electrical stimulation of the needles), morphine and ketamine. Evaluation of clinical parameters included the subjective experience of pain intensity, blood pressure, pulse, temperature, psychosomatic symptoms and side effects. Neurophysiological parameters consisted of the quantitatively analyzed EEG and somatosensory evoked potential (SEP). Pain was significantly reduced by hypnosis, morphine and ketamine, but not during the control session. Of the four acupuncture techniques, only electro-acupuncture at specific loci significantly decreased pain. The EEG changes during hypnosis were dependent on the wording of the suggestion and were characterized by an increase of slow and a decrease of fast waves. Acupuncture induced just the opposite changes, which were most significant when needles were inserted at traditional specific sites and stimulated electrically. The evoked potential findings suggested that ketamine attenuates pain in the thalamocortical pathways, while hypnosis, acupuncture and morphine induce analgesia at the later CNS stage of stimulus processing. Finally some clinical-neurophysiological correlations were explored.