Thursday, December 2, 2010

Acupuncture Alters Pain Sensations in the Brain

Conference NotesAcupuncture for pain relief has been studied extensively, but only recently using brain imaging. A new investigation has found that acupuncture reduces activation in several brain areas involved in the perception and processing of pain, as well as sparking a placebo-like analgesic response.

Using functional magnetic resonance imaging (fMRI), researchers in Germany captured pictures of the brain while patients experienced a pain stimulus, both during acupuncture and without acupuncture, to determine acupuncture's effects on how the brain processes pain [Theysohn et al. 2010]. Study results were presented November 30, 2010 at the annual meeting of the Radiological Society of North America (RSNA).

In the study, 18 healthy volunteers first underwent fMRI while a painful electrical stimulus (8 on a 10 point scale) was applied to their left ankles. Then, acupuncture needles were placed at 3 locations on the right side — between the toes, below the knee, and near the thumb — and fMRI was repeated while the painful stimulus was again directed at the left ankle. The researchers compared the images and data obtained from the fMRI sessions with and without acupuncture (fMRI provides real-time visualizations of blood flow changes in response to brain activity).

According to lead researcher Nina Theysohn, MD, from the Department of Diagnostic and Interventional Radiology and Neuroradiology at University Hospital in Essen, Germany, “Activation of brain areas involved in pain perception was significantly reduced or modulated under acupuncture.” Furthermore, acupuncture affected brain activation in areas governing a patient’s expectations of pain, similar to a placebo analgesic response.

Specifically, acupuncture reduced activation in key areas of the cortex and limbic regions that sense and process painful stimuli. At the same time, activation in brain regions governing expectation of pain — such as the primary somatosensory cortex, frontal cortex, and insula — was modulated, which reduced cognitive pain perception in ways that have been previously associated with a placebo effect. In essence, subjects may have thought that acupuncture would reduce the pain and their brains responded accordingly.

“Acupuncture is supposed to act through at least two mechanisms — nonspecific expectancy-based effects and specific modulation of the incoming pain signal,” Theysohn observed. “Our findings support that both these nonspecific and specific mechanisms exist, suggesting that acupuncture can help relieve pain. Functional MRI gives us the opportunity to directly observe areas of the brain that are activated during pain perception and see the variances that occur with acupuncture.”

COMMENTARY: This was a small study, as is typical of most neuroimaging investigations, and it involved an acute pain experience in healthy subjects who knew the stimulus would be only temporary. It will be important to further this line of research by imaging acupuncture effects in chronic pain conditions, in which brain structure and functionality may have been altered over time by protracted pain. Can acupuncture restore more normal brain function for controlling pain?

Meanwhile, this study by Theysohn and colleagues is a good demonstration that acupuncture, with needles applied in peripheral locations remote from the pain-generating site, does affect activity in central brain structures associated with the perception and processing of pain signals. Furthermore, there seems to be a cognitively-moderated placebo-effect component that can be measured in key brain centers, and this is probably an integral contributor to the pain relief afforded by acupuncture.

REFERENCE: Theysohn N, Choi K-E, Gizewski E, et al. Influence of Acupuncture on Pain Modulation during Electrical Stimulation: An fMRI Study. Program and abstracts of the annual meeting of the Radiological Society of North America (RSNA), November 30, 2010, Chicago, IL. Session SSJ8-05 [abstract here and press release here].