**5. Imaging studies of acupuncture for the treatment of headaches**

Some recent reports have assessed the objective effects as well as the subjective effects of acupuncture in the treatment of headaches. Quirico et al. reported that acupuncture altered the cerebral blood flow [19]. The mean cerebral blood flow was changed by the acupoints.

Functional MRI (fMRI) is a form of objective imaging study. Recently, a study was performed to investigate brain dysfunction in patients with migraine and chronic tension‐type headache [20]. In the study of the pain‐induced activation of fMRI, migraine patients demonstrated specific brain activation in the interictal period in comparison with controls. The regions that were activated included the temporal pole, the parahippocampal gyrus, anterior cingulate cortex, lentiform nuclei, fusiform gyrus, subthalamic nucleus, hippocampus, middle cingulate cortex, somatosensory cortex, and the dorsolateral prefrontal cortex. Decreased activation was observed at the secondary somatosensory cortex, precentral gyrus, superior temporal gyrus, and the brainstem. The findings differed in the interictal, ictal, and preictal phases. Many fMRI studies have suggested the imbalance of the facilitation and inhibition of the pain signal conduction effect hypersensitivity in migraine.

In Japan, Yamaguchi et al. reported a change in the cerebral blood flow in migraine patients before and after acupuncture using arterial spin‐labeled MRI [21]. Before acupuncture, the cerebral blood flow in migraine patients was high in the occipital and right temporal lobes and low at the left temporal and parietal lobes in comparison with controls. After acupuncture, a specific increase was observed in the cerebral blood flow of the thalamus, hypothalamus, pars opercularis, and insula of migraine patients.

Li et al. treated patients with migraine without aura with standard acupuncture five times per week during a 4‐week period and examined the pain score and resting‐state fMRI [22]. Patients with migraine without aura were found to have decreased functional connectivity in the left precentral gyrus, postcentral gyrus, left supramarginal gyrus, and the lower left parietal lobe. Furthermore, they found that the decreases in these functions were improved by the acupunc‐ ture therapy.

We hypothesize that acupuncture affects not only peripheral circulation, but also central nervous function. However, few scientific studies have investigated the effects of acupuncture for headache by assessing cerebral function. In the future, an objective clinical study assessing the effect of acupuncture on headache should be conducted.
