Introduction
Phantom limb pain (PLP) is aphenomenon that amputees of both upper and lower limbs (UL and LL) may suffer. People that have this pain often feel it in the missing limb as if it is there. PLP is very common, occurring in approximately 80% of amputees.Out of this, 75-85% experience PLP immediately after the injury (1). It is very important to understand the etiology of this phenomenon before starting the research. A theory called proprioceptive memory might be the reason why amputees have PLP. This theory states that “individuals with intact limbs have typical proprioceptive sensation, meaning that they are aware of the presence and position of all four limbs” (1).Surprisingly, even if a patient loses his/her limb, these sensations remain intact, so the personexperiences sensation the same as before the amputation in terms of cold, hot, pressure or sense of position(1). Proprioceptive memory is the memoryof everything related to the limb (position, sensation) that is saved in the brain (subconscious). With the frequent usage of this information, consolidation occurs, so with repetition the task becomes easier as we age (time factor). In the case of PLP, these memories are still the same and do not change at all. That is why the person can feel the limb as if it is not amputated (1). A method of changing these memories is by visual feed-back with a conventional treatment named mirror therapy (MT) (1). This method focuses on using visual feed-back in order to trick the brain about the presence of the residual limb (amputated limb) (2). MT was first introduced by Ramachandran and Rogers-Ramachandran who used it with UL amputees. Then it was used by Chan et al with LL amputees. The treatment is very simple and involves the use of a simple mirror box or any mirror which is also of lowcost to decrease the PLP instead of expensive medications that may have various side effects. The treatment is explained to the patientas follows: move both your intact limb and the amputated one in synchronized and similar patterns.
This approach can be used at home and it can aid patients with financial problems in dealing with their condition. In order to set the mirror box at home, all that is needed is a solid stand-alone mirror on a table of similar length in front of the patient (2). Sitting is recommended for safety issues (2).Another type of mirror box comes packed like the one shown in the video (4).
It is important that the patient sees the intact limb from a specific angle to be able to see the reflection of the intact limb only. Then the patient is asked to initiate the movement ofboth limbs- seeing the reflection of the intact limb would give the patient the feeling that the amputated limb has come alive back again(1). The visual feed-back from the mirror was proven by Holmes and Spence to be effective in four aspects (3):
PLP can affect the life of amputees negatively leading to problems in their personal life and their working environment. A story of a sergeant that hadhis LL amputated due to an explosion in Afghanistan describes the effect of PLP on his life as follows: The daily pain that he suffered prevented him from sleeping and affected his relationship with his wife and children. His patience was less when dealing with his children than it used to be, and he had the desire to be alone most of the time (11). The purpose of this study is to prove the effectiveness of mirror therapy in treating phantom limb pain in amputees.
Literature Review
In this part several cases will be mentioned through which evidence will be supplied on the efficiency of mirror therapy for amputees.
The first clinical trialwas performed by Chan et al and included 22 patients that were distributed into 3 groups: mirror therapy, conventional therapy and mental visualization therapy. The sessions of each group took about 15 minutes daily for 4 weeks. At the end of the 4 weeks, the 2 groups of conventional therapy and mental visualization were merged with the mirror therapy group whereas the mirror therapy group continued the same program for another next 4 weeks making a total of 8 weeks of continuous mirror therapy. The results of the 18 subjects that completed the study were as follows: All the mirror therapy group members experienced a decrease in PLP. As for the nine that joined the mirror therapy group from the 2 other groups, 89% of them had a decrease in PLP. Also all the subjects reported an increase in the ROM of the previously frozen phantom limb (1).
Another study performed by G.Lorimer et al included 22 patients that were randomly assigned into 3 groups: mirror therapy, a control group and a group that received mental imagery of movement. The participants received the treatment for a period of 4 weeks for a period of 15 minutes daily. The results were: (6/6) of the mirror therapy group and (1/6) of the control and (0/6) in the mental imagery group reported a decrease in pain. Some limitations of the study were bias and the pain scale was not well defined;also no information wasobtained on 20% of the participates that dropped out which made the final results weak. (3)
Another study that was done by Ramachandran et.al, discussed a case of a 42 year old male patient (the name was changed to DS for privacy issues), that had a left brachial plexus avulsion in a motor cycle accident at the age of 19. As a consequence, DS's left arm was amputated to the mid-humerus. He underwent an examination 11 and 23 years post amputation. During the examinations, DS reported his symptoms as a vivid and excruciatingly painful phantom that he couldn't move no matter how hard he tried. According to DS it was as if the actual paralysis of the limb prior to amputation was transferred to the phantom along with the pain, what is scientifically called learned paralysis. Ramachandran et al hypothesized that the continuous mismatch between the motor command and the visual feed-back from the paralyzed arm (both prior to amputation and the phantom) was the source of the pain. DS mental and neurological status was fully normal except for a Horner syndrome in his left eye. In the first attempt to match the motor command with the visual, Ramachndran et al used a mirror visual feed-back technique. The mirror was placed parasagittal on a table in front of the patient, DS placed his intact hand on the right side of the mirror,and then he viewed the reflection of the intact hand so that it was optically superimposed on the left location of the phantom. DS was asked to perform symmetrical movements of both hands at the same time to give the illusion that his phantom is moving also. The results of the first trial weresurprising for both the researchers and DS. The repeated movements of both the upper limbs caused the sensation of the phantom elbow, wrist and proximal palm to disappear completely and permanently along with the pain. The second trial aimed at eliminating the residual pain and phantom sensation in the fingers. In this trial Ramachandran et al used the mirror visual feedback therapy but this time it was incorporated with the use of minimizing (shrinking) and magnifying lenses. The reason for using this technique was that when using the minimizing lens, DS reported the feeling of shrinkage of the limb phantom sensation with a decrease in pain;this led Ramachandran to perform an experimental design. In this design,twoexperimental sessions were run separated by a 2-hour lunch break. Each session consistedof 18 trials, 12 with the minimizing lens and 6 with the magnifying lens. Each trial lasted for 20 seconds followed by the removal of the lens and a 30 s intertrial interval in which the lenses were randomly interleaved. At the end of the 2 sessions an additional experiment was carried out in which a 4-fold minimizing lens wasused instead of the 2-fold lens that wasused previously. Pain scale ratings of between 1-10 were obtained before and after each trial. The results were the following: The pain on two of the trials increased from 8 to 14 or 15 (how can this be when the top number in the scale is 10?) but on most of the trials (10) the pain decreased to 2 and remained with using the mirror, but returned back to 8 after some time of removing the mirror indicating that the usage of the minimizing lens reduced the pain remarkably while the magnifying ones caused the pain to either increase or remain the same as illustrated in the graph (5).
Another was performed by M.Machlachan et al, which aimed at proving that mirror therapy is effective for PLP in people with lower limb amputations. The subject was a 32 year old patient called Alan whowas admitted to have fluid drainedfrom his leg. During the procedure, complications occurred leading to amputation of his hip to save his life. After the operation he spent a period of one month in which he was in the ICU. He only recognized his amputation after 5 weeks followingthe surgery. Alan's PLP started after he became fully conscious- he felt that twoof his toes were crossed.Alan reported that the pain tended to worsen as the day progressed. In the early morning he experienced pins and needles sensation in the toes. This progressed to being painful but bearable around lunch time. Building to severe pain in the late afternoon, he felt a full phantom leg except that it wasa foot shorter that the other leg. The phantom was raised of the bed in the position of back-stroke (extension?) of the lower leg. The phantom felt asif it was in a cast from the thigh down the toes. Alan was on neuronin for a week and was referred to PT for daily TENS. However, the treatment (TENS) was stopped due to an increase in pain. Maclachan et al offered a new treatment method “for phantom pain using the mirror reflection of your leg”. This mirror therapy was explained to Alan and he was informed that it might not have any effect on the pain just the control of the limb. The treatment protocol was as follows:
First 5 days:
Daily morning+ afternoon with one therapist at each session, with mirror.
Weekend:Daily morning + afternoon on his own, with mirror
Second 5 days:
Daily morning or afternoon with one therapist at each session, with mirror
2-3 times daily on his own each day with mirror
Weekend: 3-4 times daily on his own with mirror
Third 5 days:
2-3 times daily on his own without mirror.
In this treatment Alan was asked to perform these exercises:
After implementing the program, Alan reportedthe following: the bending and pushing down exercises were easier than lifting and straightening He started to control the phantom limb on the fourth week. In terms of sensation, he reported that he had no sensation of the crossed toes that he previously complained of and the phantom pain was minimal. On a scale of 0-10 (where 0 = no pain and 10 = excruciatingly painful) Alan gave a score of 5-9 of the phantom pain and 0-2 of the stump pain. By the end of the third week his phantom missing info whereas the stump pain was 1. Another scale of control (where 0% means no control and 100% means absolute control) was given to Alan. His initial score was 0% but after 3 weeks it came to 25-30%. The position of the phantom limb was still the same (the phantom felta foot shorter that the intact leg) but now he can straighten the phantom limb so that it is not bent upwards from behind as he felt previously. As a result of the treatment the crossed toe sensation doesn't come back to Alan even if he bangs his stump- only a pain sensation is felt in his phantom calf. It is noteworthy that Alan was on medication the whole period prior totreatment (3weeks) and a silicon dressing of the stump was used. It can be concluded that the sense of control over the phantom limb has a great role in reducing the PLP and is beneficial in the remapping of the somatosensory cortex thus coordinating the visual and motor feed-back synchronicity. (6)
The last case exploredthe possibility of making mirror therapy accessible to patients at home. In this case the patient's name was changed to Jonathan for confidentiality purposes. Jonathan is a 35 year old man who had an above knee amputation on the left lower limb as a consequence of a motor vehicle accident that occurred on 2006. After surgery, his phantom pain started immediately and it took the characteristics of being sharp and shooting and as if the limb hadfallen asleep. Jonathan's pain varied in intensity (none to severe) and it was managed with vicodin every 4-6 hours as needed. PT started 1 month after surgery. Jonathan had several programs for pain in conjunction with PT which included attending a chronic pain clinic in September 2006 for medical evaluation. He was prescribed Effexor XR 150 for pain and depression. Vicodin was also prescribed for pain management. Jonathan was treated at home by a pain physiologist and underwent a standard pain management protocol that included relaxation techniques (diaphragmatic breathing, progressive muscle relaxation).
After the treatment he experienced a modest response and returned to work on a part-time basis.The actual PT program started in December 2006 in the indoor environment and was mostly focused on weight training. After all these treatments, Jonathan report of pain wasn't encouraging andhe reported an increase inpain by 2007. He also stopped some medications (pregbalin) and changed to Neurontin and trileptal on a specific dose. Due to financial limitations Jonathan's prosthesis wasn't producedoptimally which led to more residual limb pain during ambulation. The last treatment that Jonathan received before the application of mirror therapy was another in-house pain physiologist for specialized treatment for phantom pain on Feb 2007. His PLP was (4/10) with pain medication which caused him undesirable cognitive side effects (fuzziness). Jonathan noted that mentally flexing his phantom would cause temporary relief of symptoms, so he started his own imagery practice for 20 minutes for the past 3 months. Jonathan was evaluated fora total of five 60 minutespsychologysessions during the 3 months ofhome delivery mirror therapy. Jonathan was provided with every detail of mirror therapy including educational material. He was also told that mirror therapy had only been used for upper limb amputees and he expressed his interest in the treatment. A25-minute CD of diaphragmatic breathing and progressive muscle relaxation techniques, which he was already familiar with,was provided to him. He purchased a simple full-length mirror (4ft long and 1.5 ft. wide) for only $10. The mirror was placed longitudinally against a coffee table and he positioned his intact limb in front of the mirror so that it appeared that both legs wereintact.
Jonathan followed a non-structured protocol designed by himself. Some of the movements include dorsiflexion, plantarflexion, rotation of the ankle and touching his big toe on the mirror and so on. He did the treatment by himself at home three times a week for 20-30 min per session. The results of the treatment were the following: The diaphragmatic breathing exercises caused a decrease of the tingling sensation and a decrease in his anxiety. Jonathan reported that he increased the frequency of the therapy in the past 2 weeks to 30 min daily. He reported a decrease in pain, increase in control and enjoyedthe practice. Before the follow-up session by threedays, vicodin was stopped. Threemonths after the initial evaluation, his PLP was resolved and nerve pain was managed. He reported an improvement in mood and decrease in anxiety. Jonathan reported that even if the PLP returned, he is now able to control it by consistently practicing mirror therapy. These results indicate a direct correlation between the frequency of mirror therapy and pain intensity (7.) Please refer to avideo of a similar case in references (8).
Conclusion
From the studies mentioned above, we can see that in almost all of the cases the patients that received mirror therapy reported a decrease in PLP and phantom sensation and also reported more control ofthe limb. One of the studies included a subject that talked about using mirror therapy in the home setting. This information is very crucial for physical therapists since our aim is to reduce the suffering of patients at all times. This case discussed the ability of the patient to control his/her own symptoms without referring to physical therapy for advice which can lower the load on the system. It is our mission as physical therapists to make exercises and tasks as easy and accessible as possible for the patient and that what makes mirror therapy a very good treatment. Additional benefits include: improving the patient's morale, returning back to one's occupationand normal activities of daily living, and reducing the use of medications thus protecting the internal organs and reducing the financial burden on the patient. The explanation of the therapy is easy and doesn't require a specific protocol only some active participationofthe patient and persistence. The period of exercising is very short - about 20 min - which plays a role in preventing boredom during exercise making the treatment more effective and efficient. In conclusion, the evidence shows that mirror therapy is effective in the treatment of PLP.
