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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 30  |  Issue : 1  |  Page : 43-48

Efficacy of motor imagery (mirror visual feedback) in complex regional pain syndrome: A study


1 Department of Pain, ESI Institute of Pain Management, Kolkata, West Bengal, India
2 Department of Physical Medicine and Rehabilitation, ESI Institute of Pain Management, Kolkata, West Bengal, India

Date of Web Publication7-Jan-2016

Correspondence Address:
Dr. Subrata Goswami
Flat No. 16, Doctors' Block, 3A Maharani Swarnamoyee Road, Kolkata - 700 009, West Bengal
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-5333.173466

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  Abstract 

Introduction: Complex regional pain syndrome (CRPS) is a chronic painful and disabling condition, often triggered by a minor injury. It is characterized by sensory disturbances, vasomotor and sudomotor dysfunction, motor abnormalities and maladaptive neuroplasticity. An integrated multimodal multidisciplinary treatment approach is recommended. Other than pharmacological and interventional management the use of visual illusion created by mirror has also been reported. It is a neuro-rehabilitation technique designed to re-modulate cortical mechanism of pain. Aim: To assess the effectiveness of mirror visual feedback (MVF) and establish it as a therapeutic measure in CRPS. Materials and Method: Ten patients of CRPS had been treated with Motor Imagery through MVF method for 2 weeks, where reflection of unaffected side seems to visually superimpose on the felt location of the affected one. The pre-post data of this study were collected prior and at the end of 2 weeks of treatment. Data Analysis: Done using a paired "t" test. Results: Results shows significant improvement (P < 0.05) in resting and movement pain and swelling. Conclusion: The study can be considered as an important document for establishing MVF as a treatment of choice for the patients with CRPS.

Keywords: Complex regional pain syndrome (CRPS), mirror visual feedback (MVF), motor imagery.
Key Message: Motor imagery through mirror visual feedback method is effective in reducing pain and swelling in chronic regional pain syndrome.


How to cite this article:
Goswami S, Sarkar B, Mukherjee D. Efficacy of motor imagery (mirror visual feedback) in complex regional pain syndrome: A study. Indian J Pain 2016;30:43-8

How to cite this URL:
Goswami S, Sarkar B, Mukherjee D. Efficacy of motor imagery (mirror visual feedback) in complex regional pain syndrome: A study. Indian J Pain [serial online] 2016 [cited 2020 May 31];30:43-8. Available from: http://www.indianjpain.org/text.asp?2016/30/1/43/173466


  Introduction Top


Complex regional pain syndrome (CRPS) is a debilitating painful condition associated with sensory, motor, autonomic, skin, and bone abnormalities. [1],[2],[3],[4] However, the causes of CRPS are unknown; [5] it frequently results from work-related trauma or surgery thoughthere is typically a discrepancy between the severity of symptoms and severity of inciting injury. In 9% of the cases, there is no precipitating history of trauma. [3]

In CRPS, there is interplay between central and peripheral pathophysiologies. [1] Some studies concludethat an initial noxious stimulus in the periphery results in a state of hyperexcitability in spinal cord neurones. In sympathetically-mediated pain, the nociceptive input is maintained by an interaction between primary afferents and sympathetic efferents through an adrenergic mechanism. [6],[7] In sympathetically independent pain, the maintaining nociceptive input arises from other causes such as ongoing activity in a neuroma.Widespread alteration in sensory perception and peripheral (autonomic and somatosensory) changes in CRPS must be viewed as manifestation of changes in the brain. [8] It is also hypothesized that disorganized cortical representation may lead to the experiencing of peripheral pain. [9]

CRPS is characterized by sensory disturbances such as spontaneous pain, allodynia, hyperalgesia, vasomotor abnormalities such asskin color changes, temperature abnormalities, sudomotor disturbances such as sweating, edema, and motor disturbances such as weakness, tremor, muscle spasm,and decreasedrange of movement.

An integrated multimodal multidisciplinary treatment approach is recommended, tailored to individual patients with the primary aimsof reducing pain, restoring function and enabling patients to manage their condition,and improving their quality of life. [10],[11] The four pillars of care (education, pain relief, physical rehabilitation, and psychological interventions), which address these aims have equal importance. [1]

Simple medicines such as nonsteroidal anti-inflammatory drugs(NSAIDs) often donot produce any remarkable effect in pain relief; so after 3-4 weeks neuropathic pain medicines are considered according to the Neuropathic Pain Guidelines. Antidepressants (amitriptyline, nortriptyline, duloxetine) and anticonvulsants (gabapentine, pregabaline) have been shown to be effective to some extent. [12] In interventional therapy intravenous regional anesthesia, sympathetic block and spinal cord stimulation had been tried. [12] Therapeutic approaches such as desensitization, general exercises and functional activities, relaxation techniques, splinting, and modalities such astranscutanious electrical nerve stimulation (TENS)can also be usedas an adjunct. [1]

The use of visual illusions created by a mirror, often referred to as mirror therapy, was first introduced by Ramachandran VS,Rogers-Ramachandran. [13] Over the last few years, the use of mirror therapy has been reported in a number of studies. Some of these studies have focused on the use of mirror therapy in patients with pain syndrome such as phantom limb pain, [14] brachial plexus avulsion, [15] and CRPS. [16],[17],[18],[19] Other studies have focused on the use of mirror therapy for motor training after stroke. [20],[21],[22],[23] More recently, mirror therapy has also been applied during rehabilitation following hand surgery. [24]

Mirror therapy is a neurorehabilitation technique designed to remodulate the cortical mechanism of pain. In this, the patients perform movement of the unaffected limb while watching its mirror reflection superimposed over the (unseen) affected limb, thus creating a visual illusion of the affected limb movement. [25] The visual illusion of the affected limb movement generates positive feedback to the motor cortex and would restore the integrity of cortical mechanism, which might in turn interrupt with the pain cycle and restore function in the affected limb.

Although mirror therapy has been successfully used in different cases, still there is a paucity of enough literature to unanimously prove its effectiveness in CRPS resistant to neuropathic medicines and other adjunct therapy.

Aims and objectives

  1. To see the effectiveness of motor imagery through mirror visual feedback (MVF) in CRPS.
  2. To establish mirror therapy as a low-cost, home-based, easy-to-use, patient-delivered therapeutic technique.



  Materials and Methods Top


Ten patients with CRPS who came to a government institute of pain management from July 2015 to November 2015 were included in the study.

After obtaining necessary clearance from the institutional ethical committee, informed written consent was taken from each patient before participation.

The patients fulfilled the following inclusion criteria:

  1. Age between 18 years and60 years.
  2. Symptoms and signs of CRPS as per the Budapest Criteria. [26]
  3. History of CRPS for more than 3 months.
  4. Patients on neuropathic medicines for at least the last 2 months.
  5. CRPS less than 1-year-old.
  6. Patients with features of significant amount of swelling, pain, and functional inability in the terminal body parts (hands or feet) [Figure 1] and [Figure 2].
Figure 1: Complex regional pain syndrome affecting the left hand


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Figure 2: Complex regional pain syndrome affectingthe right foot


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Patients were excluded on the basis of following criteria:

  1. Inflammatory condition.
  2. Infection or cellulitis.
  3. Radiculopathy or distribution of pain in a single nerve.
  4. Neuropathic pain from nerve entrapment or nerve injury, neuritis, or plexitis.
  5. Peripheral nerve disease.
  6. Unhealed fracture.
  7. Vascular conditions such as deep vein thrombosis, vascular insufficiency, lymphedema, erythromelalgia.
  8. Compartment syndrome.
  9. Thoracic outlet syndrome.
  10. Bilateral symptoms.


Patients included in the study were provided with mirror therapy where previous neuropathic medicines were continued.

Mirror visual feedback therapy

Patients were asked to sit comfortably keeping a mirror perpendicular to the midline of the body with the unaffected side in front of the reflecting surface of the mirror and the affected side hidden behind the mirror. The affected limb should be relaxed and rested on a support surface behind the mirror throughout the period of therapy. Patients were asked to look at the mirror and assume the mirror image of the unaffected side as the affected body part. The patients were asked to do pain free range of movements of the unaffected body parts in different directions in front of the mirror. By seeing the mirror image, patients were asked to imagine the affected limb to bemoving in a pain-free manner. The whole procedure was properly demonstrated to all the patients and it was made sure that they understood [Figure 3] and [Figure 4].
Figure 3: Motor imagery using themirror visual feedback method


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Figure 4: Motor imagery using themirror visual feedback method close-up view


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MVF therapy was given to the patients in a 2 min on-off schedule (2 minof exercise and 2 min of rest) for 20 min, twice a day, 7 days a week in a home-based environmentfor 2 weeks. [27]

The following data had been collected for analysis prior to the treatment (MVF) had started (pre) and at the end of 2 weeks of therapy (post).

Dependent variables

  1. Pain at rest: It ismeasured by the visual analog score (VAS). The pain of patients wasevaluated at resting condition between 0 (no pain)and 10 (highest pain the patient can imagine).
  2. Pain on movement: It ismeasured by VAS. The pain of patients wasevaluated during movement and weight-bearing between 0 (no pain) and 10 (highest pain the patient can imagine).
  3. Swelling of the affected limb: It is measured by a measuring tape [making a figure of "8" where loops were surrounding the circumference of the body part and the cross ("X") was situated at the dorsum of the hand or footwhere the swelling was maximum].


Data had been analyzed using a "paired t-test."

Statistical analysis

We considered the following:

Event 1: When the patient is at rest.

μ1 as mean score of pain (VAS) prior to the start of the treatment.

μ2 as mean score of pain (VAS) aftertreatment.

Event 2: When the patient is on movement.

μ3 as mean score of pain (VAS) prior to the start of the treatment.

μ4 as mean score of pain (VAS) aftertreatment.

Event 3: When the patient is having swelling.

μ5 as mean score of swelling (cm) prior to the start of the treatment.

μ6 as mean score of swelling (cm) aftertreatment.

Event 1

Null Hypothesis:μ1= μ2.

Alternative Hypothesis:μ1 > μ2.

It is a study where scores have been recorded before treatment and after treatment. The number of samples was only 10 and so we applied the paired t-test.

Event 2

Null Hypothesis:μ3= μ4.

Alternative Hypothesis:μ3 > μ4.

It is a study where scores have been recorded before treatment and after treatment. The number of samples was only 10 so we applied the paired t-test.

Event 3

Null Hypothesis:μ5= μ6.

Alternative Hypothesis:μ5> μ6.

It is a study where scores have been recorded before treatment and after treatment. The number of samples was only 10 and so we applied the paired t-test.

Statistically analyzed output for Event 1



Since the P value wasless than the level of significance (5%), we rejected the null hypothesis and concludedthat after application of the motor imagery the mean reduction in resting pain score wasstatistically significant [Diagram 1].



Statistically analyzed output for Event 2:



Since the P-value was less than the level of significance (5%), we rejected the null hypothesis and concludedthat after application of the motor imagery the mean reduction in movement pain score wasstatistically significant [Diagram 2].



Statistically analyzed output for Event 3:



Since the P value wasless than the level of significance (5%), we rejected the null hypothesis and concludedthat after application of the motor imagery, the mean reduction in swellingwasstatistically significant [Diagram 3].




  Result Top


We evaluated all the patients at the time of presentation (day 0) and after 2 weeks (day14). Pain score (VAS) at restand on movement and swelling wastaken in centimeters. All the statistical analyses showed significant difference between prevalues and postvalues where P < 0.05.


  Discussion Top


In the above study,motor imagery using MVF method has been proven to be effective in relieving resting and movement pain and reducing swelling in patients with CRPS.

In MVF therapy, the centrally processed congruent visual feedback from moving the unaffected limb provided by the mirror, which appears to originate from the dysfunctional and painful side, acts to establish the normal pain free relationship between sensory feedback and motor intention, restore the integrity of central processing, and consequently results in a rapid resolution of thestate of pain and restoration of function of the affected limb. [28]

A number ofsmall studies and case reports have found mirror therapy of benefitin patients withCRPS but the underlying mechanism of pain reduction during mirror therapy is not very clear since in the literature, several hypotheses have been described.

The important role of the convergence of different signals on to a complex "neuromatrix" in the construction of body image has long been emphasized by Melzack. [29]

Rock and Victor also found that vision dominates touch and proprioception; if an object was foundto merely look large using a lens while it was being palpated, it also felt large. Rock coined the phrase "visual capture" to describe the phenomenon. [30]

The discovery of mirror neurons in the frontal and parietal lobes by Rizolatti in the early 1990s [31] has provided us with more concrete evidences of how motor imagery is effective. Mirror neurons fire when merely watching another individual performing the movement. These areas are rich in motor command neurons, each of which fires to orchestrate a sequence of muscle twitches to produce simple skilled movements. [29]

When the patient looks at the visual reflection of the unaffected hand, however, he/she sees that there is no external object causing the pain in the optically resurrected limb; so his/her brain rejects the pain signals as spurious. It is a matter of how different signals are weighted and integrated or gate each other in the construction of body image even without seeing it moved and how they might provide partial relief. [28]

The alleviation ofpain with MVF has also been studied using brain imaging, showing that the degree of phantom pain correlates well with the degree of maladaptive reorganization of somatosensory pathways and this reorganization is partially reversed by MVF with the corresponding reduction of pain. [31]


  Conclusion Top


The study has concluded that the motor imagery using the MVF method might be effective inCRPS.

Limitation

  • Small sample size.
  • Study was only of 2 weeks' duration. Long-term follow-up data will be a better future plan.
  • Limitation of resources and technologies [as procedures such aspositron emission tomography (PET) scan or functional magnetic resonance imaging (FMRI)werenot available],which act as a direct evidence of changes in the cortex.
  • We have analyzed only two dependent variables of pain and swelling. More variables can be taken such as color change in the skin, skin temperature, range of motion, and function.
  • There is future scope of researches, which can see the effectiveness of mirror therapy in comparison with neuropathic medicines and adjunct therapeutic procedures.


Acknowledgement

We sincerely acknowledge the help from Dr. Pradip Kumar Bhattacharjee, Director of ESIInstitute of Pain Management(IPM), for his kind permission, Mr. Gopesh Chandra Talukdar, Consulting Statistician for data analysis, and Mr. Debankan Bhattacharya forhis sincere technical assistance during this study.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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