Dept. of Neurological Science - University of Liverpool

Functional Magnetic Resonance Imaging (FMRI) - Study into the Use of Mental Imagery to Relieve Phantom Limb Pain

Phantom limb pain is a common problem for people following amputation of a limb. It can be resistant to simple painkilling techniques and many people with phantom limb pain face a lifetime of suffering. Some people may benefit from TENS or surgical implants to the spinal cord or brain, but even these techniques may not give good pain relief. The pain may be constant and disabling and often the person perceives the limb to be held in a cramped, uncomfortable position.

Researchers have shown that when a limb is amputated it may lead to changes in the cortex of the brain, resulting in abnormal firing of neurones or nerve cells. These changes have been shown to be more common in people who suffer from phantom pain. It is possible to illustrate these changes using an imaging technique called functional Magnetic Resonance Imagery (fMRI) to show which areas of the brain have become reorganised as a result of amputation. It has been suggested that phantom pain may result because of a mismatch between motor commands being sent to the absent limb by the brain, without any sensory feedback from the limb to confirm that a motor command has been carried out. There has already been a significant amount of work carried out at the Pain Research Institute using fMRI to study models of pain.

This study aims to investigate whether using mental imagery techniques such as meditation may help a person with phantom pain. Meditation has been used at the Walton Centre for several years to help people with chronic pain to learn to relax and distract themselves from their pain. Some people with phantom pain has found that during meditation they are able to "move" the phantom arm into a comfortable relaxed position, thus relieving their pain. People recruited on to the study will be taught to meditate and "move" their phantom arm. They will be scanned prior to meditation training to determine the extent of changes on the surface of the brain. Following meditation and imagery training they will enter the scanner again, and "move" the arm during scanning so that any further changes on the brain's surface may be detected. Any cerebral changes will be linked to the amount of pain relief the recruit may have experienced as result of learning meditation.

We are currently recruiting up to 20 people who have lost an arm above the wrist, who suffer from phantom pain and are willing to learn to meditate. We hope that this study will help us to learn more about the mechanisms of phantom pain and other pain conditions, and also to study how the brain responds to meditation and mental imagery.

Functional Magnetic Resonance Imaging (FMRI)

The Pain Research Institute is currently involved with several projects examining the neurophysiological response to pain. One particular method used for studying the brain's response to pain, is fMRI. This technique, developed in the early 1990s, may be used to visualise increases in regional blood flow to parts of the brain in response to various stimuli (e.g. auditory, visual, mechanical, noxious etc.). We have been using painful thermal stimuli to demonstrate which brain regions are responsible for painful sensations, and are developing techniques to investigate various clinical pain conditions (e.g. low back pain, phantom limb pain, central post-stroke pain etc.), which may provide insight into how the brain interprets pain signals following injury.

The precise details of how fMRI works are beyond the scope of this page but a useful introduction by Dr Peter Jezzard, FMRIB, University of Oxford can be found here.

In addition, the Cambridge Brain Imaging Unit has useful links to fMRI resources around the world.

To date we have scanned 2 cohorts of healthy subjects: the first study investigated laterality of the brain response to thermal pain delivered to the right and left hand and the effect of distraction on the patterns of brain activity observed. This work has been presented at two international conferences and the British Pain Society meeting in York (2001), and is currently under review at a prestigious neuroimaging journal. Data from the second study is now being analysed and will be reported as soon as we have the results. In addition to studying healthy subjects were are also performing studies on patients with a variety of neuropathic pain conditions, ranging from phantom limb pain to central post stroke pain.

Information on the variety of different clinical pain conditions that affect patients can be found in the Chronic Pain section of this website. Alternatively The American Pain Foundation also has some good pain information on their website.

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Recalling Past Pain Experience Activates the Cortical Pain Matrix

Neuropathic Pain

The Pain Research Institute has a particular interest in neuropathic pain and this is reflected in several ongoing research studies. We are attempting to correlate pain symptoms, sensory abnormalities (using quantitative sensory testing) and intra-epidermal nerve fibre density in a heterogenous cohort of neuropathic pain patients with central and peripheral aetiologies.

A similar project is examining the relationships between trigeminal pain symptoms, sensory findings, nerve fibre density and cutaneous blood flow.

Healthy volunteers are being recruited for another study evaluating the acute effects of capsaicin on the skin.

DOWNLOAD POSTER:
Quantitative Sensory Testing (QST) and Intra-Epidermal Nerve Fibre Assessment in Neuropathic Pain - A Pathophysiological Study.