Deconstructing Complex Regional Pain Syndrome
by Robert J. Schwartzman, MD
| Dr. Robert Schwartzman is internationally known and respected for his work in studying
Complex Regional Pain Syndrome (CRPS) and helping patients who suffer the pain and
distress of the disease. It is through Dr. Schwartzman’s efforts to understand the
pathophysiology of CRPS that we are closer to referring to this troublesome syndrome (a
collection of symptoms and signs) as a disease. Control of the disease, rather than just
symptom control, depends on this knowledge and understanding. |
— Peter A. Moskovitz, MD |
 Complex regional pain syndrome (CRPS) results from damage to
C-fibers and A-delta fibers that innervate soft tissue and bone in the great majority of
instances. It may also occur after direct nerve injury and in approximately 10% of
patients after damage in CNS pathways (stroke, head and spinal cord trauma, and multiple
sclerosis).
Nociceptive pain occurs from potential or tissue destructive stimuli. It is mediated by
high threshold unmyelinated C-fibers or thinly myelinated A-delta fibers whose primary
neurons reside in the dorsal root ganglion.1 As pain is signalled through
specific afferent nociceptive pathways, direct projections of these fibers activate: 1)
the discriminative pain system (location, intensity and quality of stimulus); 2) the
affective system (the unpleasantness of the stimulus); 3) the autonomic nervous system
(sympathetics); 4) the motor system (nocifensor reflexes); and 5) the immune system.2
Approximately 50% of patients have been casted and CRPS is rarely seen following
complete nerve transection.3 Harden and Bruehl applied factor analysis to 123
patients with CRPS who met International Association for the Study of Pain Criteria (IASP)
and determined that signs and symptoms cluster into four distinct subgroups: 1)
abnormalities in pain processing (allodynia, hyperalgesia and hyperpathia); 2) skin color
and temperature changes (differential blood flow); 3) edema (neurogenic), vasomotor and
sudomotor dysregulation; and 4) a motor syndrome.4
Incidence of CRPS
The incidence of CRPS after injuries varies in different studies, but the most recent
representative population based study shows an incidence of 40.4 for females and 11.9 for
males per 100,000 person years at risk.5 The female to male ratio is
approximately 4:1; the average age at onset is between 37 to 64 years of age. Bone
fractures, sprains, soft trauma and surgical procedures are the most common initiating
events.6,7 After one year, most of the signs and symptoms are well established
and only increase moderately with disease duration.8 There is an increase in
many of the discriminative components of the McGill Pain Questionnaire but no change in
affective pain measures. Dynamic and static mechanoallodynia, loss of surround inhibition,
after discharge, cold allodynia, as well as skin color and temperature change, were
prevalent within the first five years and significantly worsened over time.
Please refer to the March 2010 issue for the complete text. In the event you need to order a back issue, please click here.
— March 2010
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