Vascular disease, trauma, congenital disorders and cancer are common causes of amputation and limb loss. Phantom limb pain emanates from the area where a limb has been lost or amputated. There is some correlation with pre-amputation pain and the development of phantom limb pain after amputation. Onset of pain usually occurs soon after amputation or years later. Typically intermittent, the pain can range in severity from mild to severe. In most cases, the pain diminishes over time. If it persists for longer than six months, chances of spontaneous recovery are poor. Phantom limb pain tends to occur more frequently in upper limb amputees than lower limb amputees and is more common in women then men.
The actual mechanisms behind phantom limb pain are undetermined. A complex series of neuroplastic changes is thought to cause the condition. Peripheral nervous system changes eventually are joined by more central nervous system changes in the spinal cord and the recruitment of cortical elements of the brain, causing a cortical “reorganization”. The role of “mirror neurons” in the brain is suspected to play a role in the development of phantom limb pain as well. Stress, anxiety and depression are thought to contribute to the development and persistence of symptoms.
Tingling, pins and needles sensations and throbbing or piercing pain are common symptoms of phantom limb pain. The perception of burning in the toes is described by many leg amputees with this condition.
In establishing the diagnosis of phantom limb pain, the physician attempts to rule out stump pain or residual limb pain, which usually presents with milder pain. The skin is inspected for wounds or infection. Sensation is tested looking for an exaggerated response to a stimulus that ordinarily is not painful. The joint above the amputation is examined for any physical abnormality. A CBC blood test, or complete blood count, may be drawn and sent to a lab to rule out infection. Ultrasound can be used to look for neuromas, which can be a source of pain. A psychiatric consult can be ordered if the involvement of anxiety and depression are suspected as triggers.
The management of phantom limb pain can be divided into three main categories: pharmacologic therapy, invasive procedures including surgery and adjuvant therapy. Medication uses to treat phantom limb pain include tramadol, opioids, tricyclic antidepressants, anticonvulsants, sodium channel blockers, NMDA receptor antagonists and ketamine. Procedures include nerve blocks, neurectomy, stump revision, rhizotomy, cordotomy, sympathectomy and CNS stimulation including deep brain stimulation. Adjuvant therapy can include transcutaneous nerve stimulation, biofeedback, ultrasound, physical therapy and cognitive behavioral therapy. Psychiatric treatment of significant anxiety and depression, if present, may be beneficial as well.