It has long been accepted that CRPS can spread from its initial presenting site to other (sometimes remote) areas of the body. For most people with CRPS, the prospect of their condition spreading is understandably their greatest fear.
The exact mechanism behind the spread of CRPS remains unclear but there are two studies that have been published in the last 20 years which purport to examine whether there is any obvious pattern to this spread.
Before considering the results of these studies, it is worth taking a moment to consider the types of terminology often used in describing the spread of CRPS:
- Contiguous Spread – refers to the (usually) gradual enlargement of the area originally affected, commonly moving up the limb or body.
- Contralateral or Mirror Image Spread – refers to the appearance of symptoms on the opposite side of the body in an area closely matching the location of the area originally affected.
- Independent Spread – refers to the appearance of symptoms in an area distant to and non-contiguous from the area originally affected.
- Ipsilateral Spread – refers to spread on the same side of the body as the area originally affected.
- Diagonal Spread – refers to the appearance of symptoms in the limb diagonally opposite to the one originally affected.
As mentioned above, there are principally two studies to consider. However, identifying patterns between these studies is virtually impossible. In addition to very small sample sizes, each study had somewhat different objectives and criteria.
The results of the larger study were published in the Journal of Neural Transmission in 2011 and involved a retrospective study of 185 people with CRPS. However, this study seems to have considered the spread of CRPS to other limbs only and not contiguous spread or independent spread. The results were summarised as follows:
“We set out to determine patterns of spread of CRPS and the factors that are associated with spread. Our results show that CRPS usually affects one limb but in some cases it spreads to another limb, most often in a contralateral (53%) or ipsilateral (32%) pattern and usually without secondary trauma. A diagonal pattern of spread was nearly always triggered by a new trauma. Spontaneous spread and spread after a separate trauma followed different patterns.”
Of interest, this study did identify that the “median interval between the occurrence in the first and second limb was 21 months.”
In a much smaller study published way back in 2000, 27 patients were studied retrospectively. It was reported that:
“Three patterns of spread were identified. ‘Contiguous spread (CS)’ was noted in all 27 cases and was characterized by a gradual and significant enlargement of the area affected initially. ‘Independent spread (IS)’ was noted in 19 patients (70%)…’Mirror-image spread (MS)’ was noted in four patients (15%)…Only five patients (19%) suffered from CS alone; 70% also had IS, 11% also had MS, and one patient had all three kinds of spread.”
Can we learn anything useful from these studies?
The only areas where the studies overlap seems to be in relation to mirror-image spread, but even there the percentage of those affected differed wildly; 49% (2011) and 15% (2000). The sample size in both studies was extremely low, particularly in the study published in 2000. Perhaps that goes some little way to accounting for the considerable disparity in those results.
Despite the tiny sample size of only 27, perhaps the two most worrying statistics appear in the results of the 2000 study:
“Contiguous spread was noted in all 27 cases and was characterized by a gradual and significant enlargement of the area affected initially” [my emphasis].
“Independent spread was noted in [70% of] patients”.
Even treating those figures with caution, for anybody with CRPS they will make terrifying reading.
Clearly, attaining a better understanding of both the nature and mechanism of the spread of CRPS is hugely important. Identifying patterns (if any) in that spread will be fundamental to achieving such an understanding. A large scale, multi-centre study examining patterns of spread is long overdue.