Mirror therapy for Complex Regional Pain Syndrome (CRPS)—A literature review and an illustrative case report

1 Introduction

Complex Regional Pain Syndrome (CRPS) is a relatively rare form of chronic pain that involves the extremities primarily. After learning about the patient (referred to as “Anna” here) described below, the authors became interested in this problem and also the therapy that Anna received. This review begins with a case presentation, then a description of the syndrome CRPS and its diagnosis and ultimately, an evaluation of the medical literature concerning mirror therapy for chronic pain.

2 Case description

The local ethics committee does not require prior approval of anonymous case report-publications. The patient gave her consent to her pain problem being described anonymously in this case report.

The patient, Anna, is a 42 year old female who has suffered since childhood from back pain. She later developed an abdominal pain diagnosed as “neuropathic” following a laparoscopy and subsequently a facial pain problem diagnosed as “neuropathic” following nasal septum surgery. Anna has an evident predilection for pain problems following trauma and these have been classified as “neuropathic”.

In 2001 Anna twisted her right ankle and foot suffering a rupture of a small muscle to the first toe and then developed a tarsal tunnel syndrome. Despite frequent contact with the healthcare system for pain, Anna did not have appropriate investigation and diagnosis until 3.5 years after the injury. During that time she developed CRPS signs and symptoms in the right lower extremity.

When seen in the Pain Clinic in Falun Hospital, Sweden in 2006, Anna presented on crutches with a swollen, painful foot with alternating periods of pale or of purplish blue skin discoloration. Course hair growth and thickened skin were described. Anna had restricted range of motion of the ankle and foot joints with allodynia to touch and hyperalgesia over the whole foot and lower leg.

Anna had been previously active socially and also physically as an aerobics instructor, but after the ankle injury in 2001 she had a very restricted lifestyle with minimal social and physical activity and a fear of anything or anyone coming in contact with her right foot.

In Falun, Anna had trials of high dose opioids, neuroleptics, and antidepressive medications. She also had trials of ketamine infusions but all with little effect. Spinal cord stimulation was considered but not tried for fear of producing a local pain problem at the insertion site and/or implantation site for the generator due to her previous responses to trauma.

In 2010, Anna was referred to the Pain Center at the Uppsala Academic Hospital, Sweden for evaluation and treatment. She subsequently was admitted for a three week multidisciplinary treatment programme. At discharge, Anna had begun weight bearing on the right foot, took part in water gymnastics and had decreased her use of pain medications. Anna attributes this mostly to the beneficial effects of mirror therapy. She now has full weight bearing and is returning to a full life. Anna continues with water exercises, mirror therapy, and works with a physiotherapist regularly. She uses oral ketamine irregularly for flare-ups.

3 Complex Regional Pain Syndrome – CRPS

CRPS is a syndrome characterized by burning pain and hyper-sensivity in the involved extremity accompanied by changes in the skin appearance, in skin temperature and in sweating. Motor function changes are also seen frequently. Patients develop a “protective zone” around the involved extremity to prevent aggravation of symptoms by contact. CRPS is often precipitated by a fracture or other trauma and it is estimated that 1% of all fractures will evolve into CRPS [1]. The syndrome can also be preceded by a nerve injury, by a reason for immobilization, or by other seemingly minor traumas. According to the taxonomy of the International Association for the Study ofPain (IASP), the symptoms are often not proportional to the initiating event and are not often restricted to a peripheral nerve receptor field if nerve injury is the precipitating cause [2]. Exactly how CRPS evolves is not clearly defined or understood.

The syndrome is not common and an exact prevalence is not known. CRPS can be both under-and over-diagnosed due to the lack of clear criteria, poor knowledge of the syndrome and/or that minor symptoms at the onset are not reported by patients. A Dutch study reported the incidence to be 26/100,000 population per year and that women are affected three times more often than men [3].

CRPS has been previously described as Reflex Sympathetic Dystrophy, Sudeck’s Atrophy, and Causalgia. A consensus on the name CRPS and diagnostic criteria came first in 1994 when the IASP taxonomy for pain was published [2]. Those criteria have good sensitivity but poor specificity which could lead to over diagnosis of the syndrome [4]. New diagnostic criteria, the Budapest criteria [5] were subsequently established after an international consensus meeting in 2003 and have been shown to have somewhat better specificity. The Budapest criteria have different interpretations for clinical use than for research use. It is suggested that the clinical criteria are more practical for clinical use due to their sensitivity but that the Budapest research criteria are better for research because of their better specificity i.e. lower inclusion of non-CRPS cases. But one should also bear in mind that the original criteria from 1994 can still be used for both clinical diagnosis and for research.

4 Budapest criteria of CRPS for clinical use, IASP 2003

1. Continued pain, which is disproportionate to any inciting event.

2. Must report at least one symptom in three of the four following categories:

   1. Sensory: reports of hyperesthesia and/or allodynia.

   2. Vasomotor: reports of temperature asymmetry and/or skin colour changes and/or skin colour asymmetry.

   3. Sudomotor: reports of oedema and/or sweating changes and/or sweating asymmetry.

   4. 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 the time of evaluation in two or more of the following four categories:

   1. Sensory: evidence of hyperalgesia (to pinprick) and/or allodynia (to light touch and/or deep somatic pressure, allodynia to innocuous cold (25 °C) or innocuous warm (40 °C), and/or joint movement).

   2. Vasomotor: evidence of temperature asymmetry and/or skin colour changes and/or skin colour asymmetry.

   3. Sudomotor/oedema: evidence of oedema and/or sweating changes and/or sweating asymmetry.

   4. Motor/trophic: evidence of decreased range of motion and/or motor dysfunction (weakness, tremor, dystonia) and/or trophic changes (hair, nails, skin).

4. There is no other diagnosis that better explains the signs or symptoms.

The diagnostic criteria are based on the clinical findings from those with the syndrome. CRPS is divided into two categories depending on whether the symptoms follow injury to a major nerve (CRPS type 2) or on whether there is no evidence for a nerve injury (CRPS type 1). This distinction may not seem to be so obvious and many say that a distinction is not necessary as treatments and prognosis are the same.

If Anna’s symptoms and signs are reviewed in the context of the above criteria, it can be concluded that she fulfilled the first criterion, that her condition evolved from a twisting injury and subsequent immobilization and her signs and symptoms following this were out of proportion to the injury. Anna fulfilled criterion 2 in that she had allodynia and hyperesthesia, changes in skin colour, oedema, and decreased motor function. Clinically, Anna even fulfilled criterion 3 with confirmation on examination of the symptoms under criterion 2. We can also assume that Anna also fulfilled criterion 4 since no other cause to explain her problem could be found. All of this is in the context of someone who had the propensity to develop pain problems diagnosed as “neuropathic” after accidental and surgical trauma.

5 Treatment of CRPS

A variety of treatments for CRPS have been studied including neural blockade, spinal cord stimulation, pharmacotherapy, physiotherapy, and cognitive/behavioural therapies. Presently, the optimum treatment should be multidisciplinary with the focus on mobilization of the affected limb [1,2,5]. Some say that the treatment should not be painful but on the other hand, fear of pain and fear of movement in CRPS need to be addressed in treatment and need to be explored with the patient [6].

It must be emphasized that all other of the proposed treatments for CRPS are to help patients increase the movement and use of the affected body part and that the foundation of treatment is mobilization.

6 Outcome of CRPS

The prognosis for patients with CRPS varies between studies. In a study by de Mos et al. [7], 68% of the patients previously diagnosed with CRPS fulfilled the outlined diagnostic criteria at the time of follow-up 2–11 years after the initiating event. They found also that a poorer prognosis was associated with a history of an injury other than a fracture, with an injury to the upper extremity and with persistent coldness of the extremity.

On the other hand, a more optimistic outcome was seen in a study by Geertzen et al. where 72% of their patients could continue working after treatment [8]. The general consensus is that the earlier that treatment is initiated, the better the prognosis. Delays in both diagnosis and treatment are associated with poorer outcomes and much of the delay is due to limited knowledge of the syndromes and limited knowledge ofpossible therapies in the medical community. Some demographic information from Harden et al. [5] on the incidence and frequency of CRPS after knee replacement surgery shows spontaneous improvement with time.

One theory about CRPS holds that immobility and protection of a body part are contributing factors and this is supported by the finding that there are changes in the cortical representation of the affected body part in CRPS patients [9]. Many patients experience that the affected body part is not their own, a common phenomenon after stroke, often called a “neglect symptom”. In the case of CRPS, it is usually referred to as a “neglect-like syndrome” and there is ongoing discussion of this phenomenon in the literature. Many of the treatment methods used currently are based on these ideas; for example, mirror therapy.

7 Mirror therapy

Mirror therapy is a treatment method that was first introduced by Ramachandra and Rogers-Ramachandra in 1996 [10]. This therapy originated with the use of mirror images to study the effects of visual input/feedback on phantom limb sensations and on phantom limb pain.

In this method, the affected body part is hidden and the patient concentrates on the mirror image of the unaffected contralateral body part during activity. This gives an illusion that fools the brain into thinking that the injured body part is well and can move normally. There are two methods of using this type of treatment. In one, the patient places the affected limb in a “mirror box” to hide it from sight. The unaffected limb is then viewed in a mirror. The other method is to have the patient at an angle to the mirror so that only the unaffected limb is seen in the mirror. In both cases, the patient then begins to move both limbs in the same way so that the affected body part does similar movements to the unaffected.

8 Literature review of mirror therapy for CRPS

The aim of this focused review was to document the present knowledge about CRPS and mirror therapy as a treatment for CRPS. The questions asked were:

1. can mirror therapy impact pain in the extremity with CRPS?

2. can mirror therapy impact function in the extremity affected by CRPS?

9 Conclusions

The patient Anna in the case study had had more than 6 years suffering from a severe CRPS before mirror-therapy was added to her treatment regimen. Mirror-therapy clearly had beneficial effects in Anna’s case in spite of a long history of apparently treatment-resistant CRPS.

The results of this literature review indicate that mirror therapy is an appropriate treatment alternative for decreasing pain and improving motor function both when mirror therapy is the main focus of treatment to facilitate active movement/mobilization of the limb and when used as part of multidisciplinary treatment. The majority of studies indicate the importance of starting treatment as early as possible after the injury for the best effect. Symptoms that have continued for more than about 2 years respond less to treatment. However, there are reports, such as the present case, that indicate that “one should never give up”.

Highlights

• A patient with long-standing CRPS of the lower extremity, improved with mirror therapy.

• Review of CRPS signs and symptoms and the now accepted diagnostic criteria.

• Review of mirror therapy for pain and rehabilitation of CRPS, phantom limb, and stroke.

• Review and evaluation of the published literature for mirror document effects in good quality studies.