Phantom Limb Pain and Phantom Sensation

What is phantom sensation and phantom pain and how do they differ from residual limb pain?

Amputees may experience different types of strange limb sensations after the amputation, some painful and others not painful. The two painful conditions are referred to as phantom limb pain and residual limb pain. The sensation that is not particularly painful, but is disturbing, is known as phantom sensation.

Phantom sensation or phenomena is experienced by most if not all amputees with a much lower incidence in people with congenital limb deficiency. With this phenomenon, the amputee still feels sensations coming from the limb even though it was amputated. These strange sensations include numbness, tingling, temperature changes or pressure in the missing limb. Others may feel as though part of the limb that is no longer present itches or has a muscle cramp. Individuals may even feel that the limb moves whether it is volitional or uncontrollable. Unfortunately, it is unclear what causes phantom limb sensation. It is felt to be attributable to some type of continued representation of the prior limb within the nervous system. The length of time phantom sensation lasts is different for everyone; for some it only lasts a few months, while in others it may reduce in intensity but last for 20 or more years.

Often a different phantom sensation, known as telescoping, may occur. With telescoping, phantom sensation tends to shrink as if the limb is getting shorter much like the way a telescope brings objects that are far away closer. The amputee will feel as if the feet or hands are now moving closer to the body, with the overall size of the limb shrinking. This phenomenon of telescoping is more common in upper limb amputees than lower limb amputees.

What is Phantom Limb Pain?

Phantom limb pain is not the same as phantom sensation. Phantom limb pain is an unpleasant sensory experience whereby the new amputee feels burning or shooting pain in part of the limb that was amputated. Some phantom limb pain even feels like an achy squeezing sensation. Like phantom sensation, many researchers and medical professionals believe that the phantom pain comes from some abnormal sensory processing within the nervous system. In fact, there is a strong correlation between people who have phantom sensation and phantom pain.

Variable reports of how common this condition is range anywhere from 55-85 percent and possibly higher. Fortunately, phantom pain tends to improve with time with only 3 percent of people reporting an increase in pain.

Many believe the incidence of phantom pain increases if the part of the limb that was amputated had a significant amount of pain for a long period of time before the amputation. Because of this, it is felt that traumatic amputees who experience pain for a brief period tend to have a lower incidence of phantom limb pain compared to patients with PVD or infections. Individuals with PVD or infections may go many months with chronic and poorly treated pain. It is therefore recommended that one way to prevent phantom limb pain from occurring is by treating pain adequately with a nerve block or epidural before the planned amputation as well as treating pain adequately. Despite this treatment philosophy, a good medical study some years ago did not demonstrate any significant difference in phantom pain relief when comparing oral pain medication to nerve blocks before amputation.

Treatment for phantom pain involves many different types of interventions and many should be used simultaneously and aggressively. One of the first things that can help with phantom limb pain involves desensitization as described already for phantom sensation. Even compression socks placed over the residual limb may help dissipate some of the more severe pain. Often, amputees will state that their phantom pain comes on during emotional or physical stress. Therefore, stress reduction strategies have been used to help treat phantom limb pain. In fact, biofeedback has been reported to reduce this pain sensation by 20-30 percent and is advantageous since medications or injections are not involved. Additionally, amputees can perform meditation and breathing exercises in many different situations without exposing themselves to possible side effects that may come from taking a pill.

The use of a TENS unit may also be helpful in controlling some of the phantom pain. TENS (Transcutaneous Electrical Nerve Stimulation) works by sending small electrical impulses in certain areas of the residual limb. By doing this, larger sensory nerves are stimulated that dampen the painful signals carried by smaller pain-carrying nerves. Unfortunately, the typical medications like anti-inflammatories and morphine-like drugs used in other pain conditions are often not effective for this type of pain syndrome. Many physicians, therefore, may not recommend their use. Surprisingly, other drugs such as those used for seizures, depression or high blood pressure have been used for phantom sensation since these medicines tend to work on the chemicals in the nerves that are responsible for transmitting pain. Interventional procedures such as epidural or nerve blocks that instill pain-relieving medications around the peripheral nerves or spinal cord may also be used to treat phantom pain. Some of these procedures involve placing implanted pumps and catheters around the nervous system that release anesthetic or pain relieving medications over an extended period of time in order to provide longer-lasting relief. Some implantable devices may use a low level of electricity instead of medication to help reduce the amount of pain. Some clinicians also offer neurosurgical procedures that attempt to reduce pain; however, this aggressive procedure should only be undertaken after various non-surgical treatments have been tried and proven unsuccessful.

Residual limb pain is pain that persists or develops in the part of the limb that was not amputated. This usually occurs at the very end of the amputation site. The incidence of stump pain tends to be highest in days following surgery but then decreases or goes away just like any other surgical pain. Pain within the residual limb can have many causes and some can create significant problems if they are not detected early. Therefore, it is important that an amputee with residual limb pain be examined by a physician so that the underlying cause can be treated. In addition, this visit can help distinguish residual limb from phantom pain. The causes of residual limb pain are many and listed in the table below. Although all of these can affect normal function and the use of a prosthesis, certain ones like an infection or worsening PVD could put the residual limb at risk as well as the health of the amputee. A few will be discussed in more detail.

Possible Causes of Residual Limb Pain in Amputees

• Skin Problems and Infection
• Poorly fitting prosthesis
• Poor blood supply to the limb (worsening PVD)
• Nerve pain due to diabetes or other condition (Neuropathy)
• Neuroma formation
• Heterotopic bone formation
• Poor tissue coverage at the end of the bone
• Adherent scar tissue Sciatica Arthritis

Following surgery, healing tissue may scar down over the end of the residual limb. This tissue can become painful, particularly if it is not mobilized when symptoms first begin. This is one of the reasons it’s recommended to begin massaging the residual limb shortly after surgery when cleared by the physicians. The adherent scar not only can cause residual limb pain but also can prevent a prosthesis or socket from fitting or working properly, particularly when the muscles are contracting inside of the socket. A physical or occupational therapist, in the case of an upper limb amputee, can assist in wound care as well as instruction on gentle massage to prevent this from occurring.

Neuromas often form after an amputation. These benign (non-cancerous) growths are collections of nerve endings that form underneath the skin. They develop as a result of the nerves in the limb being cut either by trauma or the amputation. It is the body’s way of trying to reinnervate the limb, but unfortunately there is no place for the nerves to go. They subsequently collect in a bundle of tissue and become very sensitive. There are various treatment options for this painful condition. One is to have anesthetic and corticosteroid injected around the neuroma site. Many times modification of the prosthetic socket will help remove any pressure on the neuroma. Some advocate surgery to remove the neuroma, but unfortunately there is a high rate of reoccurrence when this treatment is used.

Heterotopic bone formation can also occur within the residual limb. This condition involves the development of an excess amount of bone that forms abnormally around the end of the amputated limb, creating pressure points when the amputee puts the prosthesis on. Fortunately, this bone formation is not very common in adults with amputations but occurs more often in growing children with amputations. If severe, this bone can be surgically removed, but this is more successful when the heterotopic bone has matured and stopped growing.

Poor tissue coverage at the end of the residual limb can cause the amputee to feel pain when the prosthesis is put on. This is why surgeons prefer to use muscle to cover up the end of the bone so that a nice cushion is placed at the end of the limb so the person can put weight on it when wearing a prosthesis. People who have disarticulations at various joints such as the knee or ankle are better able to tolerate a large amount of load without a muscle covering up the end of the amputation. This is one of the biggest advantages of having a disarticulation. Too much pressure, even in a normally formed and cushioned amputated limb, can create pain particularly if the socket of the prosthesis does not fit appropriately. One way to test whether a socket fits well (particularly for the above-knee amputee) is to use a small amount of clay or putty rolled into a small ball. This ball is then put into the bottom of the socket and the amputee dons the prosthesis. A good fitting socket will not smash the ball of putty. If the clay ball is flattened, then too much pressure is being placed at the end of the residual limb. The residual limb should instead only slightly flatten the ball, indicating that total contact is present. This is optimal for proper prosthesis fitting.

There is another way to see where there are excessive pressure points on the residual limb. Crayon or lipstick could be marked onto the liner or sock that is worn over the residual limb. The amputee puts on the prosthesis and wears it for a brief period of time, then the prosthesis is removed and the socket is inspected. The marks made can possibly indicate too much pressure. These areas then can be relieved by having the prosthetist make adjustments to the socket. An amputee should not try to fix his own socket or prosthesis.

Why is it important to know about phantom sensation?  

It is important that the rehabilitation team discuss phantom sensation with the individual before and after amputation. These sensations can be quite real and vivid for the amputee, but the amputee may not want to mention the sensation since they may be labeled as having a psychological problem. If counseled, the amputee can be informed that these sensations are normal and to be expected, thereby allaying any anxiety or distress that phantom sensation may produce after having an amputation. The other important reason to discuss and constantly remind the amputee of this phenomenon is for safety issues. Often the new amputee will wake up at night or be in a semi-alert state due to pain medication. He may fail to remember that the sensation of having the limb underneath him is indeed only the phantom sensation. When he tries to step on the amputated side he will fall, which can result in devastating consequences with injury to the residual limb as well as the individual.

What can be done to treat phantom sensation?

In general, no treatment is absolutely necessary if the phantom is not bothersome to the amputee. However there are strategies that can help reduce these strange sensations. Techniques used to decrease the feeling of phantom sensation are to stimulate the end of the residual limb as soon as possible following surgery. This stimulation is often referred to as desensitization and involves repetitively touching and massaging the end of the amputee with the hand. In this way the nervous system and brain can begin to adjust to the new residual limb. Another great way to desensitize the limb is to touch the end of the residual limb with materials of different textures. For example a hand towel can be lightly stroked across the skin. Although this may be irritating at first, it should improve rapidly and the residual limb will get “tougher” while the phantom limb sensation may improve. Some patients also report that wearing a prosthesis can alleviate the phantom sensation. IPOPs therefore may be used to reduce phantom sensation, but this may not help everyone. It is very important that extreme care be taken to avoid injury to the surgical wound, especially right after surgery, so that the incision does not open leading to infection.