Phantom limb pain is a phenomenon that affects amputees. Most patients report mild and intermittent symptoms of pain in the non-existing limb, but the pain can become a severely impairing experience for some.
Pharmacologic treatment for phantom limb pain
The available pharmacological treatment for phantom pain leaves much to be desired. A large meta-analysis using the Cochrane database evaluated 6 categories of medications, including opioids, anticonvulsants, NMDA receptor antagonists, antidepressants, anesthetics, and calcitonin. Results were variable with modest and short-lived improvements at best, and significant side effects resulting from almost all of the medications. There was no stand-out best mediation for pain control, and, in practice, each patient could stand to benefit from a tailored pain control regimen based on individual pain response coupled with attention to side effects.
Non-pharmacologic treatments for phantom limb pain
Given the persistence of phantom limb pain among some amputees, alternatives to side-effect-inducing pharmacologic treatments are desirable. There are a number of approaches to the non-pharmacologic management of phantom limb pain.
Physical therapy for phantom limb pain is focused on motor training and the use of prosthetic devices. Physical therapy requires patient involvement and cooperation, and has been shown to be effective for some patients.
Cognitive approaches to the management of phantom limb pain are typically used as an adjunct to other pharmacological and non-pharmacologic treatments. Potentially augmenting the positive effects of other treatments, cognitive therapy has not been found to produce negative effects in management of phantom limb pain.
Mirror therapy is an interesting mix of physical therapy and cognitive therapy that “tricks” the brain into perceiving control of the amputated limb through the use of mirrors while moving the opposite (intact) limb. Mirror therapy does require patient cooperation, and it has shown promising preliminary results.
Transcutaneous electrical nerve stimulation
Transcutaneous electrical nerve stimulation (TENS) is a method that employs directly stimulating the painful limb with electrical pulses applied to the painful stump as a means of reducing the long-term phantom limb pain. With promising results, TENS is a non-invasive treatment without documented side effects.
Deep brain stimulation
Deep brain stimulation (DBS) involves implanting electrodes in the brain and stimulating with electrical signals in order to lessen the symptoms. The use of DBS is most well known in association with Parkinson disease, but its use for neuropathic pain control has been documented, with mixed results among relatively small sample sizes. This is the most invasive intervention for management of phantom limb pain, and it has not shown overwhelming success, although it can certainly be an effective option for the right patient.
The future of phantom limb pain therapy: selecting the right therapy for each patient
The current explanation for phantom limb pain is rooted in the neuroplasticity and reorganization of the brain that occurs after amputation, making the perception of pain in the brain regions that perceive peripheral pain hyperactive. However, not all amputees experience the same degree of phantom limb pain and not all of them respond to treatment in the same way. Perhaps the effective treatment of phantom limb pain lies in identifying distinctive features of brain activity that could make individual patients more or less responsive to carefully selected treatment modalities, whether pharmacological, electrical, implantable, or rehabilitative.
Lenggenhager B, et al. Phantom limbs: pain, embodiment, and scientific advances in integrative therapies. Wiley Interdiscip Rev Cogn Sci. 2014 Mar;5(2):221-231.
Alviar MJ, et al. Pharmacologic interventions for treating phantom limb pain. Cochrane Database Syst Rev. 2011 Dec 7;(12):CD006380.