Neurophysiological Basis of Rehabilitation in Patients with Complex Regional Pain Syndrome-Type I (CRPS-I) and chronic Low Back Pain (LBP)

Complex Regional Pain syndrome type I (CRPS-I) is the current term used for a
disorder of the extremities characterized by an increased sensitivity for pain
(hyperalgesia) and the phenomenon that non-painful tactile stimulation is
experienced as painful (allodynia). Apart from that there are movement
impairments, swelling, changes in temperature and color in the affected limb.
Relevant to the current study are also the decreased tactile acuity and
disturbed muscle tone (dystonia) observed in CRPS-I. No agreement exists about
the aetiology and supporting mechanisms of CRPS-I. In recent years, the role of
the central nervous system has gained increasing attention. The assumption is
that the somatosensory cortex and emotional circuits have an important
contribution. Up to now, the only available non-invasive therapy was
physiotherapy. Recently, it has been shown that pain-related fear might have
an role in CRPS-I, and that exposure in vivo treatment (EXP) targeting this
fear yields positive results.
The results support the hypothesis that 1. the experienced pain is influenced
by pain-related fear and the negative meaning assigned to particular stimuli.2.
EXP reduces activation of fear-related brain areas during normal touch. 3. EXP
leads to a restructuring of sensorimotor circuits by removing touch and
movement-related fear.

Another type of pain is low back pain (LBP), which affects 70% to 85% of
general population, but usually heals within 12 weeks in 90% of patients. The
rest of the patients suffer from intractable, chronic LBP despite no evident
organic abnormality (Deyo et al., 2001). Research shows that also in these
patients cognitive and behavioural aspects of pain are important and related to
physical performance and self-reported disability (Vlaeyen et al., 2000).
Several studies have demonstrated the success of EXP in this patient group: EXP
resulted in improvements in pain-related fear, catastrophizing, performance of
daily relevant activities, and in pain intensity (De Jong et al., 2005; Vlaeyen
et al., 2002; Leeuw et al., 2008; Woods et al., 2008).
This will be the very first study to compare different types of chronic pain in
terms of brain activity and effects of treatment. Comparing patients with
CRPS-I versus patients with LBP will reveal commonalities across the different
types of chronic pain, but also unique aspects. This information will further
help us understand how EXP works and whether the effect of EXP is general or
specific per chronic pain type.

The goal of this study is to investigate the effect of Exposure in vivo on the
brain areas involved in the processing of harmless tactile stimuli in CRPS-I
and LBP patients (touch or warmth in CRPS; touch in LBP) and the processing of
visual pictures of movements or activities that might be experienced as
threatful, as well as its influence on tactile discrimination thresholds and a
lifting task, respectively.

Patients diagnosed with CRPS-I, LBP and healthy controls will take part in a
magnetic resonance imaging (MRI) study, additional diagnostic tests and a
psychophysical experiment to establish the tactile discrimination threshold.
These measurements will be carried out both before, during, after the
rehabilitation treatment (EXP) and at six month follow-up. Anatomical,
diffusion- and T2*-weighted MR images will be acquired. The study will consist
of a 4x3 split plot design (pre, during, post treatment and follow-up; and
CRPS-I, LBP and healthy controls).

Each participant will be measured four times for this study (before start of
the treatment, during and after the treatment program, and at six months
follow-up) Each session will last about 3 hours and consists of a diagnostic
part (90 minutes), a psychophysical experiment (30 minutes) and an MRI
measurement (60 minutes). No mentally taxing or stressful tasks are involved,
although the tactile stimulations might be experienced as unpleasant (though
unharmful) and the visual pictures might be experienced as threatful.
Participants will be asked to wear a motion sensor on both arms during seven
days around the time of the pre and post Measurement. Wearing the Actiwatch
does not interfere with normal daily activities. The patients are further asked
to fill out a diary with short questions about their symptoms, which also forms
part of the treatment for patients not included in the study.
Up till now there are no known damaging effects for MRI measurements - in
contrast to X-rays. MRI-scans pose no heath threat because it does not use
ionising radioation but magnetic fields and radio waves. However, the scanner
does produce loud noise. Participants get ear-plugs and a head Phone to reduce
sound levels.
The magnetic field aligns the molecular spins; the participant doesn*t notice
this and the effect passes as soon as the participant is taken out of the
scanner bore. Scanning could cause the bodily temperature to rise by tenths of
a degree. There are some counter-indications for MRI scanning, such as having a
pacemaker, or metal splinters in the body.
Some aspects can make the MRI measurement less comfortable for some
participants, such as:
Pain: the scanning itself does not cause any pain, but the fact that the
participant has to spent about 40 minutes lying still on his/her back can be
uncomfortable fors ome people. The researcher will fixate the head of the
participant before the measurement, and will make sure that the participant is
as comfortable as possible.
Claustrophobia: claustrophobia is an exclusion criterion, but also
non-claustrophobic participants can experience the scanner bore as scary, even
though only the head is actually inside the bore. If a participant experiences
a first claustrophobic episode during the measurement, the measurement will be
stopped .