Phantom Pain

The Five Senses and Beyond: The Encyclopedia of Perception - Jennifer L. Hellier 2017


Phantom Pain

Phantom pain is the pain and sensations that are felt at the location of a missing limb or organ as though that missing body part could still experience sensations. Most of the time, these sensations are felt in an amputated limb or portion of a limb. It is sometimes associated with feelings that the amputated limb is still a part of the body. Phantom pain can also occur in individuals who were born without limbs. Sensations caused by phantom pain are not limited only to pain; other common sensations are pressure, touch, tingling, burning, and movement, to name a few.

Risk Factors and Symptoms

There are some risk factors associated with phantom pain, especially in amputees. If an individual experiences preamputation pain, he or she is more likely to feel pain in the amputated limb after the procedure. In part, this could be due to the nervous system “remembering” the pain and continuing to send pain signals. Stump pain caused by neuromas (abnormal outgrowths of nerve endings resulting in nerve pain) can also have phantom pain or sensations associated with it. An ill-fitting prosthetic replacement can create phantom pain in the amputated limb as well. Individuals who have bilateral limb amputations, lower limb amputations, or other pain are at risk for phantom pain.

Phantom pain can happen anywhere from a few days after amputation up to a few weeks after amputation. It is a neuropathic pain, caused by malfunctioning of the nervous system rather than a real injury. This is because the limb in which the pain is felt is no longer connected to the patient’s body. Paresthesias are often associated with phantom pain. Patients with phantom pain rarely have persistent pain; rather they feel pain in their phantom limb intermittently. Approximately 50 to 80 percent of amputees experience phantom pain at some point after amputation (Virtual Medical Center, 2009). Persistent pain in the phantom limb only occurs in approximately 5 percent of amputees (Virtual Medical Center, 2009). In most amputees, phantom pain disappears after two years postamputation.

Pathophysiology

The mechanisms behind phantom pain are still not well known, but it is currently being studied. One known cause of phantom pain is a neurological condition called neuromas. There are two different types of neuromas that are linked to phantom pain: tumor and traumatic. Since the amputation damages the nerve fibers, abnormal nerve growth occurs to try to compensate for the missing portions. This causes extreme pain in patients. Other theories on possible causes of phantom pain are based on neurological pathways and mechanisms.

Management

Since the causes of phantom limb pain are still not completely understood, it is difficult to treat phantom pain. Additionally, each individual reacts differently to the pain and to the various treatments available, so there is no cure-all for phantom pain. Multiple types of treatments can be used to manage phantom pain, including medicine, surgical therapies, and alternative therapies. Analgesics, a broad class of painkiller that works with the peripheral and central nervous systems, can be used to treat this disorder, but they do not ease pain in most patients. Anticonvulsants and tricyclic antidepressants have been proven to work more effectively at treating phantom pain and neuropathic pain in general.

Chronic phantom pain can be treated by surgical placement of a deep-brain stimulator. In deep-brain stimulation, the location of the misfiring neurons involved with phantom pain within the brain is determined using positron emission tomography scans and magnetic resonance imaging. Once the location has been determined, surgeons open the skull and stimulate this region on the brain with electrodes until the patient feels the most relief from the pain. The electrode is then left in the brain and secured so that the patient continues to get relief while going about his or her life. A pulse-generator is connected to continue the stimulation and is implanted below the skin above the collarbone.

Alternative therapies to treat phantom limb pain include mirror-box therapy and acupuncture. Mirror-box therapy is one of the most well-known alternative treatments for phantom limb pain. In mirror-box therapy, the stump from the amputated limb and the intact limb are placed in a box with a mirror that reflects the intact limb as though it is the phantom limb. The patient then undergoes various exercises while watching the mirrored image. This can trick the brain into believing that the phantom limb is clenching, unclenching, or doing a variety of other things.

Lastly, acupuncture can be provided, where very small, fine, sterilized needles are stuck into the skin at certain locations. Acupuncture is thought to stimulate the central nervous system to release endorphins, which often act as natural pain relievers. This relief of endorphins helps to counteract the pain felt at the amputated limb.

Riannon C. Atwater

See also: Central Nervous System; Homunculus; Nociception; Sensory Receptors; Somatosensory Cortex; Somatosensory System

Further Reading

Mayo Clinic. (2011). Diseases and conditions: Phantom pain. Retrieved from http://www.mayoclinic.org/diseases-conditions/phantom-pain/basics/symptoms/con-20023268

Virtual Medical Center. (2009). Phantom limb pain. Retrieved from http://www.myvmc.com/diseases/phantom-limb-pain/#Symptoms