MRI, SPECT Reveal Mechanisms: Your Brain on Acupuncture

ORLANDO—The Taoist concepts underlying acupuncture may seem ethereal by Western biomedical standards, but the neurophysiologic effects of this modality are proving to be quite concrete.

MRI and SPECT imaging techniques are opening windows onto the neurologic effects of acupuncture. Two studies presented at the annual meeting of the American Academy of Medical Acupuncture show that the technique produces clear, consistent, and measurable brain changes.

"Two thousand years of traditional Chinese medicine cannot be wrong," said Wen-Ching Liu, PhD, of the Functional Imaging Laboratory, University of Medicine and Dentistry of New Jersey. Dr. Liu presented functional MRI studies involving six subjects, one woman and five men, who underwent acupuncture needle insertion at the Ho Ku (Large Intestine 4) point, located on the dorsal aspect of the hand, between the base of the thumb and the first finger.

Weng-Ching Liu, PhD, Functional Imaging Laboratory, University of Medicine and Dentistry of New Jersey.

This point is frequently used for symptom relief and analgesia in the treatment of headaches, sinus congestion, and other common, minor conditions.

Dr. Liu and his colleagues used blood oxygen level dependent (BOLD) MRI to evaluate brain activity over a series of on-off intervals in which the needle was inserted, then removed, and reinserted, with 2 minute breaks between periods. Each patient underwent five on-off cycles over a period of 30 minutes.

This imaging method can detect increases or decreases in blood flow as small as 1%. The net effect of the acupuncture was determined by calculating blood flow increases or decreases—markers of regional neural activity—during the "on" versus "off" periods.

All six patients, five of whom had never had acupuncture before, showed similar patterns of increased activity in the thalamus, putamen, amygdala, cingulate gyrus, parahippocampal gyrus, and caudate regions when the Ho Ku point was stimulated. "There was lots of activation," Dr. Liu remarked.

The investigators observed a definite, almost stepwise sequence of increasing followed by declining activity over the five "on" periods.

BOLD MRI taken during a series of acupuncture needle insertions at the Ho Ku point near the thumb, reveals a progressive bilateral increase and subsequent decrease of blood floow in key pain-mediating regions of the midbrain. Image courtesy of Wen-Ching Liu, PhD, Functional Imaging Laboratory, University of Medicine & Dentistry of New Jersey.

The initial stimulation produced relatively little effect. The second round produced increases in the putamen, temporal gyrus and thalamus. Activity seemed to peak during the third stimulation. Dr. Liu noted that at peak—20 minutes into the sequence—there was a stunning 5,067% total increase in brain activity, the MRI image looking like Times Square on a Saturday night.

By the fourth round, the activity began to subside in most of the brain regions, and by the fifth, the images looked nearly the same as at baseline, despite continued stimulation of the Ho Ku point. "This subsiding of the peak was unexpected. We are not sure what it means," Dr. Liu said.

In general, the patterns of increased midbrain activation in this study are consistent with other conventional studies of analgesia, he added. They are also consistent with acupuncture research conducted at the University of Pennsylvania.

Dr. Patrick Lariccia, of the University's Department of Rehabilitative Medicine, reviewed a series of SPECT studies led by Dr. Abbas Alavi, at the University's Department of Nuclear Medicine. This series involved five chronic pain patients treated with acupuncture who underwent SPECT imaging at baseline, and 10–25 minutes after placement of the needles by Dr. Lariccia.

All subjects had pain refractory to conventional medical therapy including NSAID medications, narcotics, tricyclic analgesics, and corticosteroid injections. They all had past positive responses to acupuncture.

In each case, Dr. Lariccia used combinations of treatment points that had previously relieved the pain; these included points both close to and distant from the focus of the pain. "We loaded the odds in our favor. If there were physiologic effects, we should be able to see it."

The second SPECT scan was taken only after the patient reported experiencing analgesia, and the needles were left in place during the imaging procedure.

At baseline, all five subjects showed marked asymmetry of thalamic blood flow. This, said Dr. Lariccia, is a hallmark of chronic pain syndromes. Three subjects had greater blood flow on the right side, while two had greater flow on the left.

He noted that laterality of flow distribution could not be easily correlated with laterality of experienced pain, since most patients had bilateral or diffuse pain.

The pattern changed dramatically after acupuncture analgesia. The investigators observed restoration of thalamic blood flow symmetry in all five cases. They also saw increased brainstem activity in four of the five subjects. There were no changes in the basal ganglia or other key neurologic structures.

Dr. Patrick Lariccia, Department of Rehabilitative Medicine, University of Pennsylvania.

Dr. Lariccia said thalamic and brainstem changes are not surprising—these are the key regions of activity for enkephalins and endorphins in the descending inhibitory pain pathway. Many investigators have posited that endorphin-mediated processes underlie acupuncture analgesia.

Imaging studies like these provide a Western physiologic complement to the more poetic descriptions of acupuncture's effects in the traditional Chinese literature, and they can go a long way in convincing skeptics that the treatment "does something real." But Dr. Lariccia urged the medical community to take a more proactive, less suspicious attitude toward this modality.

"We know it is safe, and we know it is useful. Should we be waiting around to find the 'true' mechanism before we use something that can relieve the suffering of our patients?"

THE REDUX: Functional neuroimaging of patients receiving acupuncture shows increased neural activity in the putamen, thalamus, and temporal gyrus consistent with endorphin and enkephalin-mediated pain inhibition. Chronic pain patients typically show asymmetry of thalamic blood flow which can be reversed with acupuncture.

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