from the AMA Guides to the Evaluation of Permanent Impairment, 6th edition, page 450

Complex regional pain syndrome is a challenging and controversial concept. It is difficult to diagnose accurately, and epidemiological studies indicate that most such diagnoses are made within a workers’ compensation context. Therefore, this is a particularly challenging diagnosis to rate. The hallmark of this condition is a characteristic burning pain that is present without stimulation or movement, that occurs beyond the territory of a single peripheral nerve, and that is disproportionate to any suspected inciting event. The pain is associated with specific clinical findings, including signs of vasomotor and sudomotor dysfunction and, later, trophic changes of all tissues from skin to bone.


The International Association for the Study of Pain (IASP) created the diagnoses of CRPS type I to replace the diagnosis of RSD, and CRPS type II to replace causalgia. Historically, sympathetic nervous system dysfunction was thought to be a cause of symptoms, and the term RSD reflects that. Causalgia was considered similar to RSD except it followed an unambiguous lesion of a peripheral nerve, either a major mixed nerve in the proximal extremity (major causalgia) or of a purely sensory branch more distally (minor causalgia). Currently, CRPS I is considered when clinically appropriate signs and symptoms are present in the limb without nerve injury, and CRPS II is considered when appropriate signs and symptoms are present in the clinical setting of an unambiguous injury to a specific peripheral nerve.


Since a subjective complaint of pain is the hallmark of this diagnosis, and since all of the associated physical signs and radiologic findings can be the result of disuse, an extensive differential diagnostic process is necessary. Differential diagnoses that must be ruled out include disuse atrophy, unrecognized general medical problems, somatoform disorders, factitious disorder, and malingering. A diagnosis of CRPS may be excluded in the presence of any of these conditions, or any other conditions which could account for the presentation. This exclusion is necessary due to the general lack of scientific validity for the concept of CRPS, and due to the reported extreme rarity of CRPS (any of the differentials would be far more probable).


Because accurate diagnosis of CRPS is difficult, the diagnostic approach should be conservative, and supported by objective findings. The diagnosis of CRPS has not been scientifically validated as representing a specific and discrete health condition. The diagnostic process is itself unreliable, as competing diagnostic protocols and definitions are continuously being introduced and utilized. There is no gold standard diagnostic feature which reliably distinguishes the diagnosis of CRPS from presentations that clearly are not CRPS. Scientific findings have actually indicated that whenever this diagnosis is made, it is

probably incorrect. A diagnosis of CRPS may create a dilemma for the evaluator with regard to a specific injury. Specifically, a lack of proportionality between a clinical presentation and any suspected inciting event is inherent to the concept of CRPS. Therefore, an evaluator must determine if there is relationship between CRPS and the injury in question.


Complex regional pain syndrome may be rated only when: (1) the diagnosis is confirmed by objective parameters (specified later in this section), (2) the diagnosis has been present for at least 1 year (to ensure accuracy of the diagnosis and to permit

adequate time to achieve MMI), (3) the diagnosis has been verified by more than 1 physician, and (4) a comprehensive differential diagnostic process (which may include psychological evaluation and psychological testing) has clearly ruled out all other differential diagnoses. Emphasis is placed on the differential diagnostic process because accurate diagnosis of

CRPS is difficult and because even objective findings have been demonstrated to lack diagnostic validity.


The taxonomy and criteria, which were adopted by the IASP Committee for Classification of Chronic Pain of the International Association for the Study of Pain (IASP), have contributed to progress in understanding the syndrome. These substantial efforts finally provided standardized diagnostic criteria, improved clinical communication and homogeneity of research, and provided the promise of results that could be compared across studies. These criteria have been examined both in terms of external and internal validation. The IASP criteria, while sensitive, lack specificity, that is, they would identify patients as having CRPS when they do not. As a result of validation studies, proposed modified research diagnostic criteria were developed. A formal international consensus resulted in the criteria shown in Table 15-24.


Signs are objective evidence of disease perceptible to the examiner, as opposed to symptoms, which are subjective sensations of the individual. The examiner should provide objective evidence of the reported findings (eg, photographic documentation, temperature measurements) whenever possible. The presence or absence of the objective factors shown in Table 15-25 should be noted.


In CRPS I, neither the initiating causative factor nor the symptoms involve a specific peripheral nerve structure; therefore, impairment is based on Table 15-26, Complex Regional Pain Syndrome (Type I). In CRPS II a specific sensory or mixed nerve structure is involved; therefore, the rating is based on Table 15-21 Peripheral Nerve Impairment – Upper Extremity Impairments. With CRPS II the severity of CRPS is first determined using Table 15-26 Complex Regional Pain Syndrome (Type 1). 

The steps in assessing CRPS type 1 impairment are as follows:

  1. Determine if CRPS is a ratable diagnosis—that the diagnosis has been confirmed (Table 15-24 Diagnostic Criteria for Complex Regional Pain Syndrome), the diagnosis has been present for at least 1 year, the diagnosis has been verified by more than 1 physician, and a comprehensive differential diagnostic process has clearly ruled out all other differential diagnoses.
  2. Determine the number of objective diagnostic criteria points (Table 15-25 Objective Diagnostic Criteria Points for Complex Regional Pain Syndrome).
  3. Assess adjustment factors, as described in Section 15.3.
  4. The classification of severity is based on the number of objective diagnostic criteria points and assessment of adjustment factors, as described in Section 15.3. A minimum of 4 points is required for a class 1 rating, 6 points for a class 2 rating, and 8 points for a class 3 or 4 rating. If there are 3 points or less, the rating for pain complaints may be based on Chapter 3, Pain, as applicable.
  5. Using Table 15-7 Functional History Adjustment Modification, Table 15-8 Physical Examination Adjustment Modification, and Table 15-9 Clinical Studies Adjustment Modification, identify the grade modifier number for each adjustment factor that is determined to be reliable. The process differs from that used for DBIs. Average the grade modifier numbers and use this
  6. information to define the class number in Table 15-26 Complex Regional Pain Syndrome (Type 1) – Upper Extremity Impairments. If that class number is not supported by the objective diagnostic criteria points, the highest class specified
  7. by those points is selected. For example, if an individual has grade modifiers that ultimately resulted in assignment to class 2 but the objective diagnostic criteria points were only 4, the individual would be assigned to class 1. Using clinical judgment, select the appropriate grade within the class. Since the adjustment factors are used to define the class, they cannot be used to determine the grade within the class. The physician may use clinical judgment to decrease or increase the grade within the assigned class and must explain in detail the rationale for any adjustments.


The rating for CRPS is a “stand alone” approach. If impairment is assigned for CRPS, no additional impairment is assigned for pain from Chapter 3, nor is the CRPS impairment combined with any other approach for the same extremity from this chapter.