Abstract
Background
Definition and Characteristics
PLP describes pain that patients perceive as coming from an amputated limb as if it were still contiguous with the body. It is distinct from pain at the actual site of the amputation (stump pain). Patients usually experience PLP as occurring in the distal part of the phantom limb and can describe it as feeling “burning,” “tingling,” “sharp,” and “cramping.” Uncomfortable perceptions of limb distortion (such as retraction into the stump) are also reported. PLP is most commonly seen after limb amputation, but similar syndromes can occur with the removal of other body parts including breasts, testicles, eyes, and tongue.
Epidemiology
PLP occurs in 50%–80% of patients after amputation, but is severe in 5%–10% of cases. Risk factors for developing PLP include: tumor-related amputations, chronic limb pain prior to amputation, and significant pain the day of amputation. Despite this, meticulous perioperative analgesia with epidural anesthesia has not been clearly shown to prevent PLP.
Pathophysiology
Both central and peripheral mechanisms are believed to mediate PLP and are incompletely understood. Amputation can lead to reorganization of the somatosensory cortex with “remapping” of the location of amputated limb into the mouth and chin areas. For these patients stimulation of the mouth or ipsilateral face can cause sensations, including pain, that seem be originating from the phantom limb. Central sensitization from preexisting chronic limb pain as well as ectopic discharges from the stump neuroma are also implicated.
Therapy
While both drug and non-drug therapies have been investigated, treatment of phantom limb pain remains poorly studied and is largely empiric. Due to the complex nature of PLP and its therapies, a multi-disciplinary approach to treatment is mandatory including pain specialists, physiatrists, physical and occupational therapists, and psychologists.
Drug treatment: Most clinicians approach PLP as a neuropathic pain syndrome. A few small controlled trials have shown positive results with gabapentin, ketamine, and opioids but not with tricyclic antidepressants. Despite this, there is insufficient evidence to judge the superiority or inferiority of any drug therapy for PLP, and most clinicians empirically use the full range of adjuvant analgesics along with opioid therapy if needed in its management. Non-drug treatments: Nonpharmacologic therapies have also been investigated. These include myoelectrical prostheses, transelectrical nerve stimulation, and mirror therapy. In small studies, the regular use of a myoelectric prosthesis (a prosthesis with electrodes embedded in the socket that stimulate nerves in the stump), has been demonstrated to alter cortical reorganization and reduce pain. For those patients for whom a myoelectric prosthesis is not possible, transelectrical nerve stimulation (a TENS unit) to the stump can have a similar affect. A newly investigated approach is mirror therapy. Mirror therapy involves the placement of mirrors to create the illusion of an intact limb (patients visually perceive that they have an intact limb where their stump is). Patients are taught to move both the real and the illusory limb with the hypothesis that this increases control of the brain over the phantom limb and leads to a decrease in PLP. In one small controlled study 100% of patients who underwent mirror therapy had a decrease in pain.
Footnotes
Fast Facts and Concepts are edited by Drew A. Rosielle M.D., Palliative Care Program, University of Minnesota Medical Center–Fairview Health Services, and are published by the End of Life/Palliative Education Resource Center at the Medical College of Wisconsin. For more information write to: rosi0011@umn.edu. More information, as well as the complete set of Fast Facts, are available at EPERC: 
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