Complex regional pain syndrome (CRPS), is an inflammatory disorder that impacts a number of physiologic systems, in particular the nervous, immune, vascular, and integumentary systems. While a definitive mechanism may be lacking, usually a limb, what there are various functional changes that are responsible for the clinical features of this syndrome. These in turn are what determine the various treatments, all of which are incorporated with rehabilitation, the ultimate aim of which is to achieve restoration of function. This paper will highlight the causes, symptoms, and treatments for this uncommon disorder.
Complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy (RSD), is a regional, post-traumatic, neuropathic pain problem that most often affects one or more limbs. Weir Mitchell identified a pattern of clinical signs and symptoms in Civil War casualties and first described CRPS in the 1860s. The severe chronic pain that followed was noted to be more prevalent when the limb injury involved a major peripheral nerve (Rho, 2002). The dramatic nature of its presentation, limited understanding of its mechanisms, and frequent lack of response to treatment has led to clinical confusion and misunderstanding in the past. Research into CRPS and the comprehension of the condition have grown extensively in the past 20 years, although total understanding remains incomplete (Bruehl, 2015).
Complex regional pain syndrome is a chronic pain condition that most often affects one limb, usually after an injury. CRPS is believed to be caused by damage to, or malfunction of, the peripheral and central nervous systems. CRPS is characterized by prolonged or excessive pain and changes in skin color, temperature, and/or swelling of the affected area. “CRPS is divided into two types: CRPS-I and CRPS-II. Individuals without a confirmed nerve injury are classified as having CRPS-I. CRPS-II is when there is an associated, confirmed nerve injury” (NINDS, 2018, p.1).
It is unclear why some individuals develop CRPS while others with similar trauma do not. In more than 90 percent of cases, the condition is triggered by a clear history of trauma or injury. The most common triggers are fractures, sprains/strains, soft tissue injury, limb immobilization surgery, or some other minor injuries and procedures. CRPS is an abnormal response that magnifies the effects of the injury. Some people respond excessively to a trigger that causes no problem for other people, such as what is observed in people who have food allergies (NINDS, 2018).
CRPS is distinguished from other chronic pain conditions by the presence of signs indicating prominent autonomic and inflammatory changes in the region of pain. In its most severe form, patients present with a limb displaying extreme hyperalgesia and allodynia (normally non-painful stimuli such as touch or cold are experienced as painful), obvious changes to skin color, skin temperature, and sweating relative to the unaffected side, edema and altered patterns of hair, skin, or nail growth in the affected region, reduced strength, tremors, and dystonia (Bruehl, 2015).
The diagnosis is clinical, most investigations are only performed to exclude other diagnoses. In these investigations they look for features that include symptoms and signs that have no other cause. These symptoms and signs are split into five categories: Sensory in which they look for allodynia (pain sensed with a non-painful stimulus), hyperalgesia (increased pain sensed with a painful stimulus), and hyperaesthesia (increased sensitivity felt with a stimulus). Vasomotor where they look for changes in skin color and temperature. Sudomotor where oedema, and sweating are primary symptoms. Motor where they look for weakness within the motor system, tremor, and dystonia. And the last category is trophic where they look for changes in the skin, hair, or nails (Palmer, 2015).
The pathophysiology of complex regional pain syndrome is not completely clear since there is a possibly of multiple mechanisms. These mechanisms include inflammation and changes in the brain and sympathetic, peripheral, and spinal nervous systems, aggravated by immobility (Palmer, 2015). The central nervous system undergoes functional and structural changes in people with persistent pain and these changes are very important in CRPS. These persistent changes in the central nervous system lead to central sensitization, a process in which the excitability of neurons in the spinal cord are increased. Another manifestation of central nervous system dysfunction in CRPS is impaired motor function. Impaired motor function is common after most injuries, but with most injuries, it generally resolves as the patient recovers. In CRPS however, susceptible patients develop certain movement disorders (Marinus, et al., 2011).
Functional restoration is the main form of treatment for CRPS, it involves various methods, most of which are physical in nature. The manner in which these physical methods are applied to patients with CRPS is quite different from the rehabilitation measures that are used for the treatment of other related injuries. The most frequently used technique is called stress loading; it is an active exercise requiring stressful use of the affected extremity with minimal joint motion (Stanton-Hicks, 2018). The most important part of a stress loading program is the active functional use of the extremity that uses basic principles of exercise physiology all of which are impacted by CRPS. Increasing a patient’s flexibility by the foregoing measures and focusing on the muscle dysfunction that is an inevitable accompaniment of CRPS is a fundamental goal of treatment (Stanton-Hicks, 2018).
There are many medications that have been reported to be helpful in CRPS, but only a few that have been tested in double-blind, randomized, controlled trials. At this time, a balanced approach based on observation, consideration of possible mechanisms, and the use of the best current information to treat these mechanisms, is the most productive clinical approach (Harden, 2001). Although monotherapy (the use of a single drug to treat a disease or condition) is the ideal, in practice the use of multiple medications is often employed. This requires a knowledgeable guess as to the mechanisms responsible for the condition, and then combining drugs that make sense together (Harden, 2001).
While a considerable number of advances in clinical management and research have taken place during the past 20 years. The mechanisms underlying the pain syndrome remain far from one’s understanding, even though more and more of the pathophysiology are beginning to take shape (Stanton-Hicks, 2018). The full range of CRPS is still unknown and the goal for the future is to learn more about this syndrome and find more ways to help those who have it, along with preventative techniques for those with a pre-existing injury.