Most people who've had a limb removed report that it sometimes feels as if the amputated limb is still there. This painless phenomenon, known as phantom limb sensation, may rarely occur in people who were born without limbs.
Phantom limb sensations may include feelings of coldness, warmth, or itchiness or tingling — but should not be confused with phantom pain. Similarly, pain from the remaining stump of an amputated limb is not phantom pain. By definition, phantom pain feels as if the pain comes from a body part that no longer remains.
Characteristics of phantom pain include:
- Onset within the first few days of amputation
- Comes and goes or is continuous
- Often affects the part of the limb farthest from the body, such as the foot of an amputated leg
- May be described as shooting, stabbing, boring, squeezing, throbbing or burning
- Sometimes feels as if the phantom part is forced into an uncomfortable position
May be triggered by pressure on the remaining part of the limb or emotional stress
The exact cause of phantom pain is unclear, but it appears to originate in the spinal cord and brain. During imaging scans — such as magnetic resonance imaging (MRI) or positron emission tomography (PET) — portions of the brain that had been neurologically connected to the nerves of the amputated limb show activity when the person feels phantom pain.
Many experts believe phantom pain may be at least partially explained as a response to mixed signals from the brain. After an amputation, areas of the spinal cord and brain lose input from the missing limb and adjust to this detachment in unpredictable ways. The result can trigger the body's most basic message that something is not right: pain.
Studies also show that after an amputation the brain may remap that part of the body's sensory circuitry to another part of the body. In other words, because the amputated area is no longer able to receive sensory information, the information is referred elsewhere — from a missing hand to a still-present cheek, for example.
So when the cheek is touched, it's as though the missing hand also is being touched. Because this is yet another version of tangled sensory wires, the result can be pain.
A number of other factors are believed to contribute to phantom pain, including damaged nerve endings, scar tissue at the site of the amputation and the physical memory of pre-amputation pain in the affected area.
It's still unknown why some people develop phantom pain after an amputation while others do not. Some factors that may increase your risk of phantom pain include:
- Pain before amputation. Some researchers have found that people who had pain in a limb before amputation are likely to have it afterward, especially immediately after amputation. This may be because the brain holds on to the memory of the pain and keeps sending pain signals, even after the limb is removed.
- Stump pain. People who have persistent stump pain usually have phantom pain, too. Stump pain can be caused by an abnormal growth on damaged nerve endings (neuroma) that often results in painful nerve activity.
- Poor-fitting artificial limb (prosthesis). Talk to your doctor to be sure you're putting your artificial limb on correctly and that it fits properly. If you think your artificial limb may not fit properly, or is causing pain, talk to your doctor.
Because the risk of developing phantom pain is higher for people who have experienced pain in the limb before amputation, some doctors recommend regional anesthesia (spinal or epidural) in the few hours or days leading up to amputation. This may reduce pain immediately following surgery and reduce the risk of lasting phantom limb pain.