Jan Chambers, President of the National Fibromyalgia & Chronic Pain Association met recently at the University of Michigan with Dan Clauw, MD, Professor of Anesthesiology, Medicine (Rheumatology) and Psychiatry, as well as the Director of the Chronic Pain and Fatigue Research Center at the University of Michigan. This is her report of that discussion.
As a world renowned fibromyalgia researcher, Dr. Clauw has helped elevate fibromyalgia science by overseeing unique studies, including the first fMRI investigations for this disorder. In the December 2009 American Journal of Medicine (supplement) article, Fibromyalgia: an overview, Dr. Clauw discusses changes in the scientific view of the possible pathogenisis of FM. He mentions that fibromyalgia is a diagnosis given to individuals with chronic widespread musculoskeletal pain which no alternative cause, such as tissue inflammation or damage, can be identified. Dr. Clauw then goes on to explain that FM is now thought to be, at least in part, a disorder of central pain processing that is known to heighten the response to painful stimuli (hyperalgesia) and painful responses to nonpainful stimuli (allodynia).
Abnormalities in central pain processing may also be partly responsible for symptoms experienced in several chronic pain disorders that co-exist with FM, which are a product of genetic and environmental factors. FM along with other aberrational pain processing disorders including irritable bowel syndrome, temporomandibular disorder, chronic low back pain, and certain other chronic pain disorders appears to reflect deficiencies in serotonergic and noradrenergic, but not opioidergic (opioid receptor), transmission in the central nervous system. In this article Dr. Clauw explains that the heightened state of pain transmission may also be attributed to increases in pro-nociceptive neurotransmitters such as glutamate and substance P. He acknowledges that although the overlapping symptomatology between fibromyalgia and related disorders may present diagnostic challenges, proper examination and observation can help physicians make an accurate diagnosis. In the past few years, a greatly improved understanding of the mechanism underlying fibromyalgia and related spectrum of diseases has fostered rapid advances in the therapy of these chronic pain disorders by both pharmacologic and nonpharmacologic interventions.
Jump forward to the March 2014 Practical Pain Management (PPM) journal article by Editor in Chief, and well known pain expert, Forest Tennant, MD, DrPH. There he discusses centralized pain syndrome and how doctors can both diagnose and treat it. In his article, Translating Chronic Pain Research into Practice: Chronic Pain and the Brain, Dr. Tennant mentions the recent discovery that pain caused by a peripheral nerve injury can imprint in the central nervous system (centralized pain) and ranks as one of the great advances in pain management. Dr. Tennant acknowledges ongoing debates about this theory, but he explains that these brain changes appear to be the result of chronic pain and not the cause. He points out that centralized pain is often accompanied by symptoms of hyperarousal of the sympathetic nervous system, which can be used to help guide diagnosis and treatment of centralized pain.
He mentions that the changing landscape of chronic pain research has yielded new ways to describe pain. The International Association for the Study of Pain (IASP) defines chronic pain as
- ongoing or recurrent pain that lasts beyond the normal course of acute illness or injury, or
- more than 3 to 6 months, and
- which adversely affects the individual’s well being.
The IASP also gives their simpler chronic or persistent pain definition as, “pain that continues when it should not.” The National Institute of Neurological Disorders and Stroke (NINDS) defines central pain syndrome as a neurological condition caused by damage to, or dysfunction of, the central nervous system (CNS), which includes the brain, brainstem, and spinal cord. This syndrome can be caused by stroke, multiple sclerosis tumors, epilepsy, brain or spinal cord trauma, or Parkinson’s disease.”
In his article, Dr. Tennant points out that these familiar terms should not be confused with the recently used description of centralized pain (CP) or central sensitization. In reality, all perceived pain is centralized.