Current Understanding of Phantom Pain and its Treatment

Abstract

Background: Phantom limb pain (PLP), defined as a painful sensation in a portion of the body that has been amputated, occurs in upwards of 80% of limb amputees and can significantly impact a patient's quality of life. First hypothesized in 1551, the disease has been poorly understood for much of this time. Still today, the exact etiology of the condition is yet to be elucidated. In the periphery, PLP resembles the neuronal changes seen in other neuropathic pain conditions. However, in the central nervous system (CNS), imaging studies suggest changes unique to PLP, such as cortical reorganization. Despite a growing understanding of its underpinnings, a mechanism-based treatment is not yet available. Rather, a plethora of treatment methodologies are available with varying levels of supporting evidence and many treatments being utilized based on efficacy seen in non-PLP patients.

Objectives: In this review, we provide a thorough summary of the current literature regarding PLP's etiology, diagnosis, treatment, and attempts to prevent the development of PLP following amputation.

Study design: A narrative review.

Methods: This was a narrative review conducted after an extensive and thorough review of available literature on the topic from a variety of sources.

Results: Current evidence supports a central reorganization process with potential amplification of aberrant peripheral inputs as the etiology of PLP. This conclusion is supported by functional neuroimaging as well as the failure of peripherally focused treatments. Treatment of PLP remains difficult due to varying response rates to therapies. Nonetheless, there are several treatment modalities that have proven effective in the majority of patients tested, ranging from noninvasive systemic pharmacotherapy to more invasive neuromodulation, such as spinal cord stimulation. While opioid therapy remains the most evidence-based treatment, the newer neuromodulation techniques appear to be superior in symptom reduction with minimal side effects.

Limitations: Evidence for the treatment of PLP is largely restricted to uncontrolled case reports and/or small single-site uncontrolled case series. Some research is further hampered by the presence of confounding factors such as concurrent treatment regimens.

Conclusions: While PLP remains a difficult-to-treat condition, practitioners can greatly improve the quality of life of patients suffering from the condition with a wide range of developing treatments. For pain intractable to traditional pharmacologic treatment, neuromodulation therapies have proven to be highly effective with minimal side effect profiles.

Keywords: Cortical Reorganization; Deafferentation; Mirror Therapy; Neuropathic; Phantom Limb Pain.