Complex
Regional Pain Syndrome
Complex
Regional Pain Syndrome (CRPS) is a problem dealt with, not infrequently, in
personal injury litigation, and as the name implies, it is comlplex. In this,
the first of three articles covering this topic, I wish to look at the
diagnostic criteria for this particular problem. In the second and third
articles I will cover the development or prognosis of the problem and then the
possible methods of treatment.
Because
the knowledge base concerning CRPS is continually growing, the result has been
that there have been several changes in the diagnostic criteria for the
syndrome. There was a recent monograph published on this subject which has
brought together the latest research evidence on this matter entitled “CRPS:
Current Diagnosis and Therapy” published in 2005 by the International
Association for the Study of Pain. The following article, quotations are from
that publication unless otherwise indicated.
“Widespread
pain following injury has long been an enigma in medicine particularly when, to
the patient and physician alike, its extent seems disproportionate to the
nature of the precipitating injury.” (p19) This is the problem that we
frequently have to face up to, and providing an explanation about this is one
of the challenges to the pain expert when instructed to assess such a case.
CRPS is one of the best know examples of this phenomenon, although not
necessarily unique.
CRPS is, as the name
implies, a syndrome. This is a collection of symptoms (what the patient
reports) and signs (what the doctor finds on examination), but behind which
there is not a clearly unified pathological process. It is usually
precipitated by comparatively minor trauma (in most instances), and frequently
immobilisation .
Along with the pain is
the development of a variety of changes which would often be associated with
abnormalities of the sympathetic nervous system (hence the former diagnosis of
reflex sympathetic dystrophy), namely changes in the blood supply, giving rise
to alterations in the colour and temperature of the limb, changes in sweating,
changes in appearance of the limb which becomes swollen, shiny and hairless.
Finally there are changes to the muscles, in particular muscle wasting.
I
would like firstly to discuss nomenclature, as there are different terms, which
are being used loosely. “CRPS has been known by many names such as
algodystrophy, mineures, mimocausalgia, sympathalgia, post-traumatic spreading
neuralgia, and most commonly reflex sympathetic dystrophy (RSD) and causalgia.”
(p45)
In
other words, RSD and CRPS are synonymous, but those practitioners who are up to
date with the current nomenclature (which has been in current use since it was
first published in the Classification of Chronic Pain: Descriptions of Chronic
Pain Syndromes and Definition of Pain Terms, 2nd ed., Seattle IASP
Press 1994) would normally refer only to CRPS, although they may use the
postscript of I or II to clarify the potential aetiology, CRPS II being
associated with a known nerve injury, unlike CRPS I, in which there is no known
nerve injury.
“The
general definition of the syndrome is that CRPS describes an array of painful
conditions that are characterised by a continuing (spontaneous or evoked)
regional pain that is seemingly disproportionate in time or degree to the usual
course of any known trauma or other lesion. The pain is regional (not in a
specific nerve territory or dermatome) and usually has a distal predominance
(i.e. tends to involve the hands or feet) of abnormal sensory, motor, sudomotor
(sweating), vasomotor (control of blood vessels), and/or trophic findings. The
syndrome shows variable progression over time.
The
modified clinical diagnostic criteria for CRPS are:
1) Continuing
pain which is disproportionate to the inciting event
2) Must
report at least one symptom in three of the four following categories
(a) Sensory: Reports of
hyperaesthesia and/or allodynia
(b) Vasomotor: Reports of
temperature asymmetry and/or skin colour changes and/or skin colour asymmetry
(c) Sudomotor/oedema: Reports
of oedema and/or sweating asymmetry
(d) Motor/Trophic: Reports of
decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia)
and/or trophic changes (hair, nails, skin)
3) Must
display at least one sign at time of evaluation in two or more of the following
categories:
(a) Sensory:
Evidence of hyperalgesia (to pinprick) and/or allodynia (to light touch and/or
deep somatic pressure and/or joint movement).
(b) Vasomotor:
Evidence of temperature asymmetry and/or skin colour changes
(c) Sudomotor/oedema:
Evidence of oedema and/or sweating changes and/or sweating asymmetry.
(d) Motor/Trophic:
Evidence of decreased range of motion and/or motor dysfunction (weakness,
tremor, dystonia) and/or trophic changes (hair, skin, nails)
4) There
is no other diagnosis that better explains the signs and symptoms” (p55)
There
has been a change in the taxonomy of CRPS. The consensus group which has
defined the criteria for CRPS, which have changed over the years, is aware that
there is a group of patients who would previously have been considered as
having CRPS, but fall outside the current new diagnostic criteria. “Another
subtype of CRPS was added by the consensus group out of concern that lowering
the sensitivity would leave some previously diagnosed cases without any applicable
pain diagnosis: CRPS-NOS (not otherwise specified) defined as “partially meets
CRPS criteria, not better explained by any other condition” (pp56-7)
This
first article has covered the basic diagnosis of CRPS. In the next article I
will consider the clinical course of this particular syndrome.
Dr
George R Harrison
Consultant
in Pain Management
University Hospital Birmingham
corgigas@blueyonder.co.uk
