How are bone scans used in the diagnosis and treatment
By Angela Mailis-Gagnon MD, MSc, FRCPC (PhysMed)
The three-phase bone scan has been used since the mid-1970s
to diagnose CRPS. An intravenous(IV) injection of a particular
radiolabelled substance that has a special tendency to concentrate
in the bones is administered and a technician takes images
of the body part in question, looking for the initial phase
of "blood flow." Immediately, he will look again
for the second phase of "blood pool." Finally, approximately
2 hours later, images will show the concentration of the radiolabelled
material in the actual bones; this is the "delayed phase."
There has been a characteristic pattern of activity in the
involved limb, which in the early 1980s was described as "pathognomonic"
-a sign or symptom upon which a diagnosis can be made- of
CRPS. However, these were retrospective studies, which
looked at patients who first had the bone scan for suspected
CRPS and then the data were analyzed. These studies could
not tell how many of these patients who had a limb trauma,
but no CRPS symptoms, had an abnormal bone scan as well.
CRPS has been reported fairly frequently after a fracture;
however, in one study mentioned in the recent volume of Progress
in Pain Research and Management1, only 16 percent of the patients
diagnosed with CRPS 8 weeks after trauma had the characteristic
bone scan pattern.
A meta-analysis of 19 published papers related to CRPS
combined the data from all these studies and used special
calculations to give an overall idea how well abnormalities
in the scan correspond to those who have clinical evidence
of CRPS. In only half the cases, the bone scan pattern
was pathognomonic of CRPS.1 Furthermore, as the disease
progresses, the changes in the bone scan go away.
Interestingly, about 12 years ago, a patient of mine who
had all the symptoms and signs of CRPS I had a surgical
sympathectomy (considered an appropriate type of surgery for
the syndrome at that time). Her three-phase bone scan before
the surgery was absolutely normal; after the procedure, the
radiologist told me that, according to the bone scan pattern,
she had "florid CRPS." Intrigued by this, we followed
a number of patients before and after sympathectomy.2 and
proved that sympathectomy itself produces a pathognomonic
CRPS bone scan.
In my line of work, CRPS I is a common diagnosis, representing
14 percent of all patients with neuropathic pain referred
to my clinic (unpublished data from a very recent analysis
of 784 consecutive patients who attended my program). Frequently
patients are referred to me because of a "CRPS bone
scan." Many of these people don't have symptoms any more,
but the bone scan is still active. Other patients are sent
to me because of an abnormal bone scan (done in the process
of regular follow-up), but they have no other symptoms. "CRPS
bone scan" can occur also in the healthy leg, not the
one with the CRPS! Obviously this is due to the abnormal
and excessive weight bearing demands on the good limb when
the patient favors the leg with symptoms. In other cases,
I have seen a few patients with factitious disorder imitating
CRPS (these emotionally-disturbed individuals may ligate
the arm or the leg creating the picture of CRPS), and
some have a "CRPS bone scan," which becomes
normal when they stop ligating the limb. Finally, I have a
significant number of patients with florid symptoms and signs
of CRPS and a negative or unclear three-phase bone scan.
On the other hand, several studies have shown that typical
CRPS bone scans can be seen in patients with diabetes
and diabetic neuropathy.3
In my view, the value of a three-phase bone scan in the diagnosis
of CRPS is very limited. A three-phase bone scan neither
makes nor excludes the diagnosis of CRPS by itself. I
always teach my students: "Never treat a test result,
treat the patient." In other words, a pathognomonic "CRPS
bone scan" can confirm a diagnosis of CRPS only when
my patient has the clinical signs and symptoms of CRPS.
1. Progress in Pain Research and Management , CRPS/RSD: Current
diagnosis and management, pg 152-154) published by the International
Association for the Study of Pain, 2005,
2. Mailis A et al. Alterations of the three phase bone scan
after sympathectomy. Clin J Pain, 10:146-155, 1994.
3. Mailis A. Is Diabetic Autonomic Neuropathy protective again
Reflex Sympathetic Dystrophy? Clin J Pain, 1995;11:76-84).
Angela Mailis-Gagnon MD, MSc, FRCPC (PhysMed) is the Medical
Director, Comprehensive Pain Program, Toronto Western Hospital,