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Preamputation Mirror Therapy May Prevent Development of Phantom Limb Pain: A Case Series

Hanling, Steven R., MD; Wallace, Scott C., MD; Hollenbeck, Kerry J., MD; Belnap, Brian D., DO; Tulis, Matthew R., MD

doi: 10.1213/ANE.0b013e3181b845b0
Pain Medicine: Case Report
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We report the cases of 4 patients who performed daily mirror therapy for 2 wk before undergoing elective limb amputation. One patient experienced no phantom limb pain (PLP). Two patients experienced rare episodes of mild PLP without effect on their participation in physical therapy (PT) or their quality of life. One patient reported daily, brief episodes of moderate PLP without effect on his participation in PT or his stated quality of life. These results indicate that preoperative mirror therapy may improve postamputation PT compliance and decrease the incidence of PLP. Future prospective studies are needed to confirm the results of this case series.

Published ahead of print November 16, 2009

From the Department of Anesthesiology, Naval Medical Center San Diego, San Diego, California.

Accepted for publication July 8, 2009.

Published ahead of print November 16, 2009

This article is the view of the authors and not the United States Navy.

Address correspondence and reprint requests to Steven R. Hanling, MD, Department of Anesthesiology, Naval Medical Center San Diego, 34800 Bob Wilson Dr., San Diego, CA 92134. Address e-mail to steven.hanling@med.navy.mil.

Mirror therapy has been successfully used to treat phantom limb pain (PLP),1 but there are no reports in the literature describing the use of preoperative mirror therapy to prevent the development of PLP. We report 4 patients who performed mirror therapy before undergoing limb amputation, the majority of whom experienced little to no PLP, no decrease in their stated quality of life, and remained fully engaged in physical therapy (PT) postoperatively.

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CASE DESCRIPTION

Case 1

A 22-year-old man in the armed forces experienced traumatic injury to his right ankle from the explosion of an improvised explosive device (IED). Multiple limb salvage procedures were performed over the next 16 mo. Pain prohibited the patient's ability to gain function in his traumatized extremity. Elective right below the knee amputation (BKA) was performed. The perioperative pain management plan consisted of epidural analgesia and morphine patient-controlled analgesia (PCA). Before the amputation, the patient underwent 14 sessions of mirror therapy.

While hospitalized, the patient did very well, denying PLP. He was discharged home on postoperative day (POD) 5. Discharge pain medications included OxyContin 40 mg by mouth (PO) 2 times/d (BID), gabapentin 300 mg PO BID, and Percocet 1 tablet PO every 4 to 6 h as needed (PRN). Follow-up 1 mo after surgery revealed mild stump pain and no PLP. The patient noted that he was fully able to participate in his postoperative PT regimen.

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Case 2

A 22-year-old man in the armed forces experienced traumatic injury to his bilateral lower extremities secondary to an IED explosion. After 9 mo of limb salvage procedures, intense rehabilitation and pain management, elective left BKA was performed to improve function. The pain management plan included epidural analgesia, intraoperative dexmedetomidine and ketamine infusions, and hydromorphone PCA. Before the amputation, the patient underwent 14 sessions of mirror therapy.

In the immediate postoperative period, the patient reported no significant pain. On POD 4, he complained of unbearable stump pain that was unresponsive to fentanyl, hydromorphone, and ketamine boluses. Of note, he denied PLP. He was transferred to the surgical intensive care unit for a ketamine infusion. During 5 days in the intensive care unit, he continued to deny PLP.

The patient was discharged home on POD 11. His pain medications included methadone 15 mg PO 3 times/d (TID), hydromorphone 2–4 mg PO every 6 h PRN, pregabalin 300 mg PO BID, acetaminophen 975 mg PO TID, amitriptyline 50 mg PO daily at bedtime, memantine 15 mg PO BID, and tizanidine 4 mg PO TID.

Follow-up 1 mo after surgery revealed moderate (4/10 visual analog scale [VAS] score) stump pain and “rare and mild” episodes of PLP. The patient noted that he was fully able to participate in his postoperative PT regimen.

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Case 3

A 22-year-old man in the armed forces experienced traumatic injuries to his right lower extremity from an IED. The patient underwent multiple limb salvage procedures over the next 4 mo. Pain control and high-level function were difficult to achieve despite multiple combinations of pain medications. An elective right BKA was performed. The pain management plan included femoral and sciatic nerve catheter placement, intraoperative ketamine and dexmedetomidine infusions, and hydromorphone PCA. Before the amputation, the patient underwent 14 sessions of mirror therapy.

The patient did well postoperatively. He reported moderate (4/10 VAS score) stump pain and a single brief episode of mild PLP that quickly resolved without intervention. He was discharged to home on POD 4. Discharge pain medications included morphine sulfate containing 15 mg PO TID, morphine immediate release (IR) 15 mg PO every 6 h PRN, methadone 5 mg PO BID, celecoxib 200 mg PO BID, and gabapentin 800 mg PO TID.

Follow-up 1 mo after surgery revealed moderate (4/10 VAS score) stump pain and “brief and mild” episodes of PLP. The patient noted easy termination of the PLP with one 15-mg morphine IR tablet. He noted that he was fully able to participate in his postoperative PT regimen.

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Case 4

A 27-year-old active duty man in the armed forces experienced traumatic injury to his right ankle after a 3-story fall. He developed chronic wound infections despite IV antibiotics and underwent multiple limb salvage procedures over the course of 14 mo.

During the patient's recovery, pain management was complicated by the development of neuropathic pain in his right ankle. In addition to multimodal medication therapy, a lumbar sympathetic block was performed in the preoperative period, which provided a temporary decrease in his pain.

Because of intolerable pain and decreased function, an elective BKA was performed. Perioperative pain management included epidural analgesia and morphine PCA. Before the amputation, the patient performed 14 sessions of mirror therapy.

The patient did well in the postoperative period. He reported moderate (4/10 VAS score) stump pain and no PLP. He was discharged from the hospital on POD 6. Discharge pain medications included morphine sulfate containing 30 mg PO BID, oxycodone IR 5 mg PO every 4–6 h PRN, and pregabalin 300 mg PO BID.

Follow-up 1 mo after surgery revealed daily brief episodes of moderate phantom heel pain and persistent mild-to-moderate stump pain. The patient expressed that the brief episodes of phantom pain were tolerable and did not affect his quality of life or rehabilitation efforts.

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DISCUSSION

PLP occurs in up to 72% of limb amputees.2 The incidence may be higher after traumatic loss or presence of a preexisting painful condition in the limb than after planned surgical amputation of a nonpainful limb.3 Phantom pain appears immediately in 75% of patients, but the appearance may be delayed by a few weeks in the other 25%.3 PLP, sometimes of great severity, may be present only for a few days or weeks, but it may persist for years or even decades.

Conventional pain treatments have been unsuccessful in treating PLP.4–6 These include local anesthetic medication through neuraxial or peripheral nerve catheters, opioids, α-2 antagonists, nonsteroidal antiinflammatory drugs, and N-methyl-d-aspartic acid antagonists. However, Ramachandran and Rogers-Ramachandran7 demonstrated the potential of using a mirror to treat PLP in patients with upper limb amputations. In their study, the patients had already undergone upper limb amputation when they participated in mirror therapy. Mirror therapy consisted of the patients placing their intact arm into a box with a mirror down the midline, so that when viewed from slightly off center, it would give the appearance of having 2 intact arms. By using a series of arm movement exercises, some patients experienced a reduction in PLP. A recent randomized, sham-controlled trial by Chan et al.1 comparing mirror therapy with mental imagery and covered-mirror therapy showed promising results. One hundred percent of patients in the mirror therapy group reported reductions in pain. Only 17% of the covered-mirror therapy control group and 0% of the mental imagery group had reduction in pain. Furthermore, 89% of patients who underwent mirror therapy after failing both mental imagery and covered-mirror therapy had a reduction in pain.1

The mechanism behind mirror therapy's effect on PLP is yet to be clearly defined. Phantom pain has been associated with expansion of the amputated limb's sensory or motor cortex map into nearby cortical structures, i.e., the elbow projection growing into the area previously represented by the amputated hand.8 (Fig. 1) Mirror image therapy is thought to reverse this cortical remapping and alleviate pain. Other postulates include: 1) activation of mirror neurons in the contralateral brain hemisphere,7 2) active sprouting of new neurons that leads to cortical remapping,6 and 3) modulation of pain pathways in the amputated limb through visually perceived movement of the amputated limb.7 A recent study shows that the motor homunculus may actually stay intact after amputation and perhaps the remapping occurs at the levels of the spinal motor neuron.9 We have provided an illustration of the many sites with possible connections to the development of PLP (Fig. 2).

Figure 1.

Figure 1.

Figure 2.

Figure 2.

In our patient population, the loss of motor and sensory function before amputation is common and can occur weeks to months before amputation. Therefore, cortical changes may occur before amputation. In patients undergoing elective surgical amputation after prolonged limb salvage attempts, preoperative mirror therapy may help to favorably influence cortical remapping and reduce the severity and/or incidence of PLP.

The 4 patients in our case series experienced multiple lower extremity limb salvage surgeries and chronic pain for 4–17 mo before elective amputation. Despite multimodal oral pain medications and regional and neuraxial techniques, the patients were still in moderate to severe pain and unable to improve function in the affected extremity. Therefore, elective lower extremity amputations were performed.

Daily mirror therapy was instituted preoperatively for 2 wk before the patient's amputation. Mirror therapy consisted of observing the unaffected leg reflected in a mirror positioned in the midline to block the view of the affected leg for 30 min (Fig. 3). All patients completed 5–6 mirror therapy sessions supervised by a physical therapist. The patients confirmed completion of independent mirror therapy sessions at each PT appointment.

Figure 3.

Figure 3.

Two weeks of mirror therapy was based on the observation that clinical changes can occur almost immediately and single nerve blocks have resulted in rapid changes of the affected limb's cortical representation.10 More specifically, 12 days of constraint-induced movement therapy showed lasting cortical reorganization in stroke patients with hemiparesis.11 It is possible that a longer period of training may be needed for patients with prolonged periods of injury before amputation. In a study on the effect of learning Braille on cortical remapping in congenitally blind patients, it was noted that enlarged hand representation did not occur until the third week of therapy.12 Perhaps in select patients, we will need to consider either doubling the daily training duration or lengthening the number of days of training. However, it should be noted that the final decision to perform 14 days of mirror therapy training was made in conjunction with the patients. Without proof of efficacy, 14 days was as long as they were willing to wait after making the difficult decision to proceed with amputation.

At 4 wk postoperatively, 1 patient reported no residual limb pain or PLP, 2 patients described mild stump pain and mild PLP, and 1 patient reported moderate residual limb pain with brief moderate episodes of PLP. It is notable that all of our patients were at high risk for the development of PLP because of their prolonged courses of limb salvage surgeries and chronic moderate to severe pain but experienced minimal PLP. Of greater significance, all of our patients remained fully functional in PT and reported no decrease in quality of life as a result of their PLP. The likelihood that these results would occur by chance seems minimal given both the high-risk patient population in this report and the high incidence of PLP.

Although these outcomes are modest, even a small improvement in the ability to prevent PLP could have a dramatic impact on the long-term prognosis of amputees, whether due to trauma, metabolic conditions, tumor, or peripheral vascular disease. The implications for combat veterans and the international community may be significant. The World Health Organization estimates that 60–70 million land mines are buried in the ground as a result of regional conflicts, and more than 250 million land mines are stockpiled globally.13 The Centers for Disease Control estimates that 1200 persons are injured by land mines each month and approximately one-third require an amputation.14

We cannot definitively state that preoperative mirror therapy reduces PLP because of the wide variability in anesthetic care in our small sampling of patients. However, preoperative mirror therapy is the 1 common treatment modality in this group of 4 patients who underwent elective BKA and whose PLP did not limit rehabilitation or quality of life. Further prospective studies of preoperative mirror therapy in patients undergoing surgical amputation, specifically in conjunction with functional magnetic resonance imaging studies of the brain, are warranted.

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ACKNOWLEDGMENTS

The authors acknowledge Dr. Ramachandran, Director of the University of California San Diego's Center for Brain and Cognition, for his work with the Comprehensive Combat Casualty Care Center at Naval Medical Center San Diego and for his encouragement and guidance in the pursuit of effective treatments for phantom pain.

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REFERENCES

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