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I have thought for a long time that the phenomenon of referred itch (mitempfindung) might have relevance to acupuncture so I was delighted to see this paper. Silberstein has shown convincingly, albeit on a small number of cases, that the distribution of remote sensations in referred itch is remarkably similar to the location of certain paired channels in the traditional system.1 So what does this tell us?
First, it reinforces what we already knew: the existence of this curious phenomenon must indicate the presence of connections in the nervous system, peripheral or central (or both), that are at present unknown. Whether or not this is directly relevant to acupuncture, it lends plausibility to the claim that inserting needles in various sites may have wide-ranging effects on distant body areas or organs.
Second, it tends to show that the traditional grouping of the channels may not be fanciful or arbitrary but may reflect the propagation of sensations in response to stimuli, a phenomenon that may have been observed by ancient Chinese physicians.
While fascinating, this discovery raises more questions than it answers (a hallmark of good scientific research, of course!). Here are some that occur to me. (1) What about clinical relevance? I don't think there is much of that yet. As Silberstein tells us, there is no similarity between the location of referred itch sites and classic acupuncture points, so one cannot extrapolate from one to the other or, probably, use referred itch as a guide for where to insert needles. (2) Silberstein investigated pairs of channels, but is there any tendency for referred itch to follow individual channels? (3) It is tempting to speculate that acupuncturists may have been led to think of the channels by finding patients who experienced referred itch, but this is unlikely. Referred itch is a skin phenomenon, but acupuncture typically involves the insertion of needles below the skin to various depths.
Moxibustion, however, is a different matter. This form of treatment does use the skin. The earliest Chinese texts we know of are those found in the Mawangdui tombs, which were composed before 168 BCE and therefore antedate the Nei Jing. The mo described in these ancient texts are clearly the close forerunners of the jingmo of acupuncture, yet the astonishing thing is that the texts say nothing at all about acupuncture ‘points’ nor, indeed, about acupuncture; the treatment they describe is moxibustion. This casts doubt on the hitherto plausible suggestion that the points were described first and the channels later postulated to link them up. More probably the sequence of events was the reverse, or perhaps the channels and the points were arrived at separately and only united in description at a later stage.2
It seems likely that patients who exhibited referred itch would show similar patterns of sensation referral when having moxibustion. (This could easily be verified by experiment today). In that case, the early moxibustion practitioners could have described the channels and later acupuncturists could have adopted the same model even if needling did not, in fact, cause the same patterns of radiation.
Directions of future research
It would certainly be worthwhile repeating and expanding this study with larger numbers of subjects. Another possibility, to which practising acupuncturists could easily contribute, would be to investigate whether there is a link between referred itch and a good response to acupuncture. Silberstein quotes 20–25% as the approximate incidence of referred itch in the general population. This is not all that different from the incidence of strong reactors in the general population, although obviously that depends on where one draws the line between average and strong response. Conversely, is failure to respond to acupuncture also a marker for absence of the referred itch phenomenon?
Provenance and peer review Commissioned; internally peer reviewed.
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