A study by the Harvard Medical School and Boston Children’s Hospital published recently in Nature reveals a possible new approach for the treatment of neuropathic pain.
Lead researcher, Professor Clifford Woolf, explained “We know that mental activities of the higher brain—cognition, memory, fear, anxiety—can cause you to feel more or less pain. Now we’ve confirmed a physiological pathway that may be responsible for the extent of the pain. We have identified a volume control in the brain for pain. Now we need to learn how to switch it off.”
Neuropathic pain is caused by damage or disease affecting part of the nervous system called the somatosensory system. The recent study has demonstrated that a small group of neurons in the brain’s somatosensory cortex (the part of the brain where the nerve signals from this system are processed) can influence sensitivity and thereby amplify the sensation of pain; ie a volume control.
What the researchers have also discovered is that the areas of the nervous system responsible for touch and pain are usually separated from one another. However, nerve injury can result in that barrier being lost. When this ‘short circuit’ happens, a feedback loop is created involving those ‘volume control’ neurons in the somatosensory cortex. The result is that otherwise harmless touch sensations are amplified into pain.
What can be done?
Researchers say that their ultimate goal is to turn down the volume control by breaking the feedback loop. They believe this may be possible through drug therapy or even electro-stimulation of the brain. Electro-stimulation has been used in the past to treat neuropathic pain, but results have at best proved variable. The answer may well be the more accurate targeting of the electro-stimulation to particular groups of neurons.
Whilst there remains much to do, the better understanding now achieved of the physiological processes involved will help considerably in focusing the further research.