What are the mechanisms of action of auriculotherapy, auricular acupuncture or auricular neuromodulation?

The mechanism of auriculotherapy is based on the triptic sensitization - reflex loop - somatotopia

Auriculotherapy is based on three clinical observations that anyone can replicate.

First, body pain (“somatic”) is associated with hypersensitivity in a delimited (“circumscribed”) area of the auricle or concha. This hypersensitivity is called “allodynia” in medical language. This circumscribed area on the ear is called “point” in auriculotherapy and auricular acupuncture, or “zone” in auricular neuromodulation.

Second, the stimulation of the sensitized area generates a therapeutic action. This observation is obvious in the case of acute pain and is not specific to the ear. The repulsive already knew this practice and, under the pretext of “putting a nerve back in place”, exerted painful stimulation on a sensitized area. Today's osteopaths no longer put the nerves back in place, but use techniques called “cutaneous” or “neurocutaneous”, the best known being palp-rolling. On the ear, it's the same thing!

Third: the distribution of these hypersensitive areas follows a particular topographic organization, like a map. This organization is called “somatotopia.” Thus, certain areas of the body will be expressed on certain areas of the ear. Everyone has the image of the “inverted fetus” in mind, but this representation is misleading and leads to false reasoning. The reality is a bit more complex.

Ear stimulation leads to a parasympathetic response

The stimulation of certain areas of the ear generates a parasympathetic response. Among these areas, the most studied was the upper hemiconcus, which is 100% innervated by the vagus nerve (Peuker et al 2002, Butt et al 2019). More surprisingly, but observed in animals only, auricular stimulation also induces a... sympathetic response (Strack et al, 1990). Thanks to functional MRI, we know that the stimulation of different areas on the ear generates different responses (Yakunina et al, 2017). Notably, all information first passes through two relays: the nucleus of the solitary tract and the locus coeruleus. Then, activation or inhibition of certain brain areas (nuclei or areas of interest) is observed. Thus, the stimulation of the auricular pavilions induces a modulation of certain neural networks, hence the term “auricular neuromodulation”. Unfortunately, very few stimulation areas have been studied, and the stimulation paradigm imposed by functional MRI does not quite correspond to current practice.

‍