Deqi (needle sensation), is closely related to clinical therapeutic effect of acupuncture in the treatment of different clinical conditions. In the present paper, the authors summarized various components or concepts of Deqi mainly in the foreign studies collected from Pubmed database. At present, foreign researches about Deqi mainly include 1) the subjects' subjective qualitative and quantitative descriptions about Deqi, 2) correlation between acupuncture stimulation induced Deqi and clinical therapeutic effects, and 3) responses of different brain regions or the connectivity of brain network shown by functional magnetic resonance imaging (fMRI) during Deqi by needling different acupoints. According to the current commonly used 6 questionnaires, aching, tingling, numbness, heaviness, dull pain, throbbing, and deep pressure sensation are the most frequently seen components of Deqi of acupuncture stimulation. The factors influencing Deqi are psychological state, personal previous experience and cultural background. Regarding the degree of Deqi and clinical effects or outcomes, the conclusions are controversial.
Results: of fMRI analysis shows that in spite of extensive deactivation of the limbic system has been found in many studies, and the connectivity of the intrinsic brain functional networks is increased during acupuncture-induced Deqi, the significance of activation or deactivation of some brain regions remains unclear, and the related mechanisms need to be studied further. No matter activation or deactivation of different brain regions during Deqi, the most important issue is the relationship between Deqi and clinical therapeutic effects. Further studies are definitely needed.