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Charles Berde, MD, PhD, executive director and founder of Children's Hospital Boston's Pediatric Pain Rehabilitation Center, is exploring a new way of thinking about reflex sympathetic dystrophy (RSD), a rare neurological condition that causes debilitating pain, swelling and hypersensitivity, usually starting in a limb. The concept moves away from the notion that pain is simply the result of nerves from an injured area sending signals to the brain. Instead, it suggests that when pain persists, the problem could be occurring in the brain itself, where nerves that originally carried signals from an injured body part may continue to fire. He likens RSD to a phenomenon commonly experienced by amputees known as phantom limb syndrome, in which physical sensations (from a nagging itch to serious pain) are still felt from the missing limb, as strongly as if it were still there.
"The idea is that the brain's pain map is maintained by an influx of perceptions from the senses and emotions, and they're all closely linked," Berde says. When the perception of pain gets crossed with visual or auditory perceptions—or emotions like fear and anxiety—it can greatly exacerbate the experience of pain. This helps explain why aggressive physical therapy and psychotherapy help adjust the pain signals in the brain: Moving—and seeing yourself able to move—sends visual cues to the brain that can help correct the misperception of pain. Berde sometimes uses a technique that's helped patients with phantom limb syndrome. A patient places her affected limb in a mirrored box so that her opposite, unaffected limb now appears to be in the position of the painful, affected limb. Seeing herself freely able to move the limb through this optical illusion sends visual feedback to the brain that's so fast-acting that relief can be immediate. "It gives patients the feeling of the limb moving in a proper way, which tricks the brain by helping it remember how to move the limb successfully," says Berde.
Children's doctors are conducting other research in hopes of better understanding RSD and other chronic pain conditions. Researchers in the departments of Radiology and Anesthesiology have recently supported a new initiative in pain imaging in children at Children's Waltham facility. The program, among the first pediatric program of its kind in the country, is led by David Borsook, MD, PhD, and Lino Becerra, PhD. The team recently conducted the first functional brain imaging study of children with RSD. As noted by the leading investigator Alyssa Lebel, MD, Pain Medicine and Neurology, the images show that pain may change the circuitry of the brain. Lebel hopes to relate future RSD studies to other chronic pain conditions, like arthritis, fibromyalgia and headaches, to understand how chronic pain impacts many aspects of brain function and how treatments can restore normal patterns of brain activity.
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