Brain Imaging for Pain
Chronic pain leads to changes in the central nervous system that are often maladaptive – they make pain worse rather than lessen it.
In collaboration with the Walton Centre, University of Liverpool and University of Cambridge, we have used functional MRI to explore these changes in several groups of pain patients, e.g. people with chronic lower back pain, phantom limb pain, and pain following spinal cord injury. We have confirmed the presence of both structural and functional cerebral changes which, while modest, are associated with clinical features.
Working with the Department of Psychological Sciences at the University of Liverpool, we have used structural MRI in patients with fibromyalgia with similar results. Structural changes with reduced grey matter are seen in the brainstem, sensory and motor cortices, and insula. Conversely, functional changes – usually increased activation – are found in several areas, including those that form the ‘emotional brain’. We have found similar results using other measures of functional brain activity, such as EEG. Our ultimate aim is to use these discoveries to help improve treatments for chronic pain (for example, spinal cord stimulation, non-invasive brain stimulation, or cognitive-behavioural treatments).
Our particular interest has been the assessment of corticospinal representation maps in the primary motor cortex of patients with chronic pain. In patients with neuropathic pain, these frequently increase in size with the centre of gravity shifting anteriorly and/or laterally. This appears to be significant enough to be taken into account for treatment (e.g. motor cortex stimulation) but may also represent a biomarker that has clinical significance.
Cortical Stimulation for Chronic Pain
Much of our brain imaging research requires fine control over the sensory and pain experience of the participants who take part in the research. To achieve this, we currently have access to range of devices for tactile and pain stimulation, including a Medoc thermal stimulator, pneumatic pressure stimulators, a vibro-tactile stimulator, electrical and laser stimulators. Some of these devices are suitable for use in an MRI scanner.
Some of our current brain imaging projects include:
* Investigating the brain mechanisms by which spinal cord stimulation reduces chronic pain (funded by the Medical Research Council)
* Developing new mathematical models of brain plasticity affecting fibromyalgia and arthritis (funded by Versus Arthritis)