Phantom limb is the term for abnormal sensations perceived from a previously amputated limb. The abnormal sensations may be painful or nonpainful in nature. It is presumed to be due to central and peripheral nervous system reorganization as a response to injury. Phantom limb pain is often considered to be a form of neuropathic pain, a group of pain syndromes associated with damage to nerves.
Description
Phantom limb syndrome was first described by Ambroise Pare in 1552. Pare, a French surgeon, noticed this phenomenon in soldiers who felt pain in their amputated limbs. Mitchell coined the term "phantom limb" in 1871. Phantom limb syndrome can be subdivided into phantom limb sensation and phantom limb pain. Stump or residual limb pain refers to pain that may persist at the residual site of amputation and may be grouped under phantom limb syndrome as well.
The onset of pain after amputation usually occurs within days to weeks, although it may be delayed months or years. Pain may last for years, and tends to be intermittent rather than constant. Pain may last up to 10–14 hours a day and can vary in severity from mild to debilitating The abnormal "phantom" sensations and pain are usually located in the distal parts of the missing limb. Pain and tingling may be felt in the fingers and hand, and in the lower limbs, in the toes and the feet.
Demographics
The incidence of phantom limb pain is estimated in 50–80% of all amputees. Phantom limb sensation is more frequent and occurs in all amputees at some point. There is no known association with age, gender, or which limb is amputated. Studies have shown a decreased incidence of phantom limb syndrome in those born without limbs versus actual amputees.
Causes and symptoms
The exact etiology of phantom limb pain is unknown. Phantom limb is thought to be secondary to the brain plasticity and reorganization. The human brain has an enormous capacity to alter its connections and function in response to everyday learning or to the setting of injury. These processes of reorganization may occur in retained nerves in the amputated limbs, the spinal cord, or various parts of the brain, including the thalamus and the cerebral cortex. Although phantom pain is presumably a result of a response to amputation injury, phantom limb pain may occur in nonamputees with spinal cord damage causing loss of sensation. This suggests that the phantom limb phenomenon may be a result of damage to pathways responsible for painful sensation in general. Research studies in primates and patients with limb amputation have shown that after amputation, the area of the brain that is responsible for processing the sensations from the missing limb are taken over by areas neighboring the missing limb.
Patients may feel a variety of sensations emanating from the absent limb. The limb may feel completely intact despite its absence. Nonpainful sensations may include changes in temperature, itching, tingling, shock-like sensations, or perceived motion of the phantom limb. The limb may feel as if it is retracting into the stump in a phenomenon called telescoping. Painful sensations include burning, throbbing, or stabbing in nature. Touching the remaining stump may elicit sensations from the phantom. The quality of the pain may change over time and may not remain constant. Patients may also feel pain from the retained stump itself. Stump pain is often associated with phantom limb sensations and may be related in etiology.
Diagnosis
The diagnosis of phantom limb is a clinical one. A history of previous limb amputation and the subsequent symptoms of abnormal sensations from the missing limb are key to the diagnosis. Spinal cord damage affecting pathways mediating sensation may also be associated with phantom limb. There are no imaging or clinical tests useful in diagnosing phantom limb.
Treatment team
The treatment team for phantom limb pain may involve the participation of neurologists, pain specialists, physical therapists, neurosurgeons, or rehabilitation specialists. Neurologists and pain specialists may help in prescribing medications to treat the phantom limb pain. Physical therapists may help to facilitate and maintain mobility. Neurosurgeons may perform surgery to place electrical nerve stimulators in the spinal cord or lesion procedures to help treat the pain.
Treatment
There are few controlled clinical studies on phantom limb treatment, and therefore no consensus on the best treatment. Treatment is directed towards the management of painful symptoms. Nonpainful symptoms rarely require treatment. Treatment for phantom limb pain involves the use of medications, nonmedical, electrical, and surgical therapy.
Medical treatment of phantom limb pain involves agents typically used for neuropathic pain. Medications such as anticonvulsants, muscle relaxants, and antidepressants may be tried. Opiate medications have also been used. Ketamine, an anesthetic agent, or calcitonin has been shown to be effective in some clinical studies.
Various electrical and nonmedical treatments may be tried. Trancutaneous electrical nerve stimulation (TENS) and biofeedback may be used. Massage, ultrasound, and acupuncture modalities may be tried as well. Training patients to discriminate sensory signals in the stump appears to be helpful in reducing pain. In research studies, allowing individuals to see a reflection of the normal, intact limb moving in the position of the amputated limb helped alleviate symptoms of phantom limb pain.
Surgical treatments for phantom limb pain are limited in benefit. Lesions of various pain centers in the spinal cord and brain can be performed, and may provide short-term relief on most occasions.
Recovery and rehabilitation
Prospective studies of phantom pain show that in two years, many amputees will experience a reduction of symptoms. Physical and occupational therapists may help in the treatment of phantom limb pain by maintaining range of motion and mobility.
Clinical trials
There are ongoing clinical trials conducted by the National Institutes of Neurological Disorders and Stroke (NINDS) studying touch perception in patients with upper limb amputation.
Prognosis
The prognosis for phantom limb varies from individual to individual. Medical treatment shows the most benefit in treating symptoms. Some studies show that in a two-year period, many amputees will experience a reduction or disappearance of their phantom limb pain. The results of the studies are somewhat limited due to the heterogeneity of the populations studied.
Special concerns
Phantom limb may have a chronic course and may lead to feelings of depression or anxiety. These feelings may require treatment by a psychiatrist. Patients with phantom limb should continue to be active and participate in community and social activities. There are various support groups for amputees.
BOOKS
Ramachandran, V. S., and Sandra Blakeslee. Phantoms in the Brain: Probing the Mysteries of the Human Mind. New York: William Morrow, 1998.
"Phantom Pain." Chapter 16. In Practical Management of Pain, 3rd edition, edited by P. Prithvi Raj. St. Louis, MO: Mosby 2000.
PERIODICALS
Flor, H. "Phantom-limb Pain: Characteristics, Causes, and Treatment." Lancet Neurology 1 (2002): 190–195.
Hill, A. "Phantom Limb Pain: A Review of the Literature on Attributes and Potential Mechanisms." Journal of Pain and Symptom Management 17 (February 1999): 125–142.
Nikolajsen, L., and T. S. Jensen. "Phantom Limb Pain." British Journal of Anaesthesia 87 (2001): 107–116.
OTHER
National Institutes of Neurological Disorders and Stroke (NINDS). Pain: Hope Through Research. NIH Publication No. 01-2406. Bethesda, MD: NINDS, 2001.
ORGANIZATIONS
American Chronic Pain Association. P.O. Box 850, Rocklin, CA 95677-0850. (916) 632-0922 or (800) 533-3231; Fax: (916) 632-3208. ACPA@pacbell.net. <http://www.theacpa.org>.
American Pain Foundation. 201 North Charles Street, Suite 710, Baltimore, MD 21201. (410) 783-7292 or (888) 615-7246; Fax: (410) 385-1832. info@painfoundation.org. <http://www.painfoundation.org>.
The Pain Relief Foundation. Clinical Sciences Centre, University Hospital Aintree, Lower Lane, Liverpool, L9 7AL, UK. 0151.529.5820; Fax: 0151.529.5821. pri@liv.ac.uk. <http://www.painrelieffoundation.org.uk/index.html>.
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