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Phantom Limb
SUMMARY
Phantom phenomena are experienced by almost all amputees following amputation. Most patients feel that the missing limb is still there, and some may have vivid sensations of shape, length, posture, and movement. These non-painful phantom sensations rarely pose any clinical problem. Between 60 and 80% of all amputees also have painful sensations referred to the missing limb. Phantom limb pain is often intermittent, and in most patients the frequency and intensity of pain attacks decline with time. However, in 5–10% of patients severe pain persists. Chronic pain involving the stump develops in a similar number of patients.
The mechanisms underlying pain in amputees are not fully understood, but factors in both the peripheral and central nervous system play a role. Preamputation pain increases the risk for phantom pain, but most studies on perioperative analgesic interventions have shown negative results. Postamputation pain may be very difficult to treat, and there is little evidence from randomized trials to guide clinicians in treatment. Until more clinical data become available, guidelines analogous to the treatment regimens used for other neuropathic pain conditions are probably the best approximation. In general, treatment should be non-invasive. Medications may include tricyclic antidepressants, anticonvulsants, and perhaps opioids. Other medications may be tried in a specialist center. Treatments such as physical therapy, mirror therapy, sensory discrimination training, and transcutaneous electrical nerve stimulation may be tried.
Introduction
The phenomenon of phantom limbs has probably been known since antiquity, but the first medical descriptions were not published until the 16th century. Authors such as Ambroise Paré, René Descartes, Aaron Lemos, and Charles Bell were similar in their descriptions of the clinical characteristics of phantom limbs but differed when it came to explaining the phenomenon. Historically, Silas Weir Mitchell (1829–1914) is credited with coining the term “phantom limb.” More than anyone else, Mitchell brought phantom limbs to the attention of the medical community. In his “Injuries of Nerves and Their Consequences” (1872), he presented the results from clinical studies of amputees and approached phantom limbs physiologically, experimentally, and therapeutically (for historical review see ).
In modern times, World War II and the Vietnamese, Israeli, Iraqi ( ), Yugoslavian, and Afghani wars have been responsible for many sad cases of traumatic amputations in otherwise healthy people. Land mine explosions in Cambodia still result in many amputations ( ), and during the civil war in Sierra Leone, the opposing factions performed limb amputations to terrorize the enemy ( ). In Western countries, the main reasons for amputation are diabetes and peripheral vascular disease in elderly people and, less often, tumors.
Amputation is followed by phantom sensations, painful or not, in almost all patients. In some patients the missing limb becomes the site of severe pain, and although much research has been done on the subject, no major treatment advances in phantom pain have taken place. Phantom phenomena may occur following amputation of body parts other than limbs, but the present chapter focuses on the clinical characteristics, mechanisms, treatment, and possible preventive measures for phantom pain after limb amputation.
Definition and Classification
It is useful to distinguish among several elements of the phantom complex:
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Phantom pain: painful sensations referred to the missing limb
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Phantom sensation: any sensation of the missing limb except pain
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Stump pain: pain referred to the amputation stump
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Stump contractions: spontaneous movement of the stump ranging from small jerks to visible contractions
There is overlap among these elements, and in the same individual, phantom pain, phantom sensations, and stump pain often co-exist.
Clinical Characteristics
Phantom Pain
Prevalence
The prevalence of phantom pain shows great discrepancy in the literature. Early studies report figures in the range of 2–4% ( ), but most recent studies agree that 60–80% of patients experience phantom pain following amputation ( Table 64-1 for details). This variation may be ascribed to differences in study populations, research design, and cutoff levels for phantom pain. Studies based on medical records of pain and analgesic requirements are likely to underestimate the prevalence ( ).
Table 64-1
Reported Prevalence of Phantom Pain, Phantom Sensation, and Stump Pain
| AUTHOR | YEAR | NO. OF AMPUTEES | AMPUTEES WITH PHANTOM PAIN (%) | AMPUTEES WITH PHANTOM SENSATIONS (%) | AMPUTEES WITH STUMP PAIN (%) |
|---|---|---|---|---|---|
| Ewalt et al | 1947 | 2284 | 2 | 95 | — |
| Henderson and Smyth | 1948 | 300 | 4 | — | — |
| Parkes | 1973 | 46 | 61 | — | 13 |
| 1978 | 73 | 67 | 100 | 43 | |
| 1980 | 133 | 30 | 54 | 17 | |
| Jensen et al | 1983 | 58 | 72 | 84 | 57 |
| Sherman and Sherman | 1983 | 764 | 85 | — | 58 |
| 1991 | 124 | 59 | 41 | 5 | |
| Houghton et al | 1994 | 176 | 78 | 82 | — |
| Wartan et al | 1997 | 526 | 55 | 66 | 56 |
| Montoya et al | 1997 | 32 | 50 | 81 | 44 |
| Nikolajsen et al | 1997a | 56 | 75 | — | — |
| Wilkins et al | 1998 | 33 | 49 | 70 | 70 |
| Ehde et al | 2000 | 255 | 72 | 79 | 74 |
| Kooijman et al | 2000 | 72 | 51 | 76 | 49 |
| Lacoux et al | 2002 | 40 | 33 | 93 | 100 |
| Wilkins et al | 2004 | 14 | 67 | 93 | — |
| Ephraim et al | 2005 | 914 | 80 | — | 68 |
| Hanley et al | 2006 | 57 | 62 | — | 57 |
| Richardson et al | 2006 | 52 | 79 | 100 | 52 |
| Schley et al | 2008 | 96 | 45 | 54 | 62 |
| Bosmans and Geertzen | 2010 | 85 | 32 | — | — |
| Desmond and Maclachlan | 2010 | 141 | 43 | — | 43 |
The prevalence of phantom pain is probably not influenced by age in adults, gender, side or level of amputation, and cause (civilian versus traumatic) of the amputation ( ). However, a recent prospective study of 85 amputees showed that female gender and upper limb amputation were associated with a higher risk for phantom pain ( ). Phantom pain is less frequent in very young children and congenital amputees ( ), but phantom pain develops in older children and adolescents almost to the same extent as in adults ( ).
Onset and Duration
Prospective studies in patients undergoing amputation mainly because of peripheral vascular disease have shown that the onset of phantom pain usually occurs within the first week after amputation ( ). The appearance of phantom pain may, however, be delayed for months or even years ( ). described a 58-year-old man who had undergone left below-knee amputation at the age of 13. Eight months before the diagnosis of diabetes, he began to complain of a typical diabetic neuropathic pain in the phantom leg, which was followed by a similar complaint in the intact limb. In a retrospective study of individuals who either were born limb deficient or underwent amputation before the age of 6 years, found that the mean time for the onset of phantom pain was 9 years in the group of congenital amputees and 2.3 years in the group of individuals with early amputations.
It is not possible to give exact descriptions of the time course of phantom pain because no prospective studies with long-term (many years) follow-up exist. Prospective studies show that the prevalence of phantom pain decreases only slightly during a maximum follow-up period of 3.5 years ( ). However, the severity and frequency of phantom pain attacks show a gradual decrease with time in most patients. In a retrospective survey of 526 veterans, phantom pain had disappeared in 16%, decreased markedly in 37%, remained similar in 44%, and increased in 3% of the respondents reporting phantom pain ( ).
Intensity, Frequency, Localization, and Character
Although phantom pain is seen in 60–80% of amputees, the number of patients with severe pain is substantially smaller, in the range of 5–10%. In a prospective study of lower limb amputees, the mean intensity of pain 6 months after amputation was 22 (range, 3–82) on a visual analog scale (VAS, 0–100) 6 months after amputation ( ). Similar results were reported in another prospective study ( ). Houghton and co-workers retrospectively asked 176 amputees to recall on a VAS (0–10) how much phantom pain they had postoperatively at 6 months and at 1, 2, and 5 years after amputation; mean scores were 4, 3, 3, 2, and 1, respectively ( ).
Phantom pain is usually intermittent and only a few patients are in constant pain. Episodes of pain attacks are most often reported to occur daily or at daily or weekly intervals ( ). In a survey of 141 upper limb amputees, found that the duration of pain attacks was seconds or a few minutes in 43% of amputees, several minutes to hours in 20%, and of longer duration in the rest of the amputees.
Phantom pain is primarily localized to the distal parts of the missing limb. In upper limb amputees, pain is normally felt in the fingers and palm of the hand, and in lower limb amputees, pain is generally experienced in the toes, foot, or ankle ( ). The reason for this clear, but the vivid phantom experience of distal limb parts is not clear. Perhaps the larger cortical representation of the hand and foot as opposed to the lesser representation of the more proximal parts of the limb may play a role.
The character of phantom pain is often described as shooting, pricking, and burning. Other terms used are stabbing, pricking, pins and needles, tingling, throbbing, cramping, and crushing. Some patients have vivid descriptions such as “a hammer is slammed at my calf” and “ants are crawling around inside my foot” ( ).
The following case is illustrative of a person with severe phantom limb pain:
A 55 -year-old man lost his arm at the age of 32 years because of an explosion accident at work. After the amputation, he had severe constant pain localized in the phantom hand and fingers. The phantom arm was extended in front of the thorax, occasionally with the perception of voluntary and involuntary painful movements of the hand ( Fig. 64-1 ). The pain waxed and waned, and during instances of severe pain the phantom moved involuntarily to the dorsum. The amputee described his pain as follows: “The pain is always there. I have a constant burning sensation in my hand and a feeling that my fingers are being crushed. It feels as if somebody is ripping off my fingernails and like sand is running through my veins. A frequent nightmare is that a wolf is eating my arm. I only sleep 1 or 2 successive hours.” Tricyclic antidepressants, anticonvulsants, including gabapentin and pregabalin, and opioids had been tried, but the patient experienced either a lack of analgesic effect or intolerable side effects. Physical examination revealed amputation of the right arm and sensory abnormalities in the amputated area. The patient had several trigger zones in the neck and the amputation stump from where referred phantom pain could be elicited. Findings on neurological examination were otherwise normal.
Preamputation Pain and Phantom Pain
Some retrospective studies, but not all, have pointed to preamputation pain as a risk factor for phantom pain ( ). The hypothesis is that preoperative pain may sensitize the nervous system, which explains why some individuals may be more susceptible to the development of chronic pain. For example, Houghton and colleagues found a significant relationship between preamputation pain and phantom pain in the first 2 years after amputation in vascular amputees, but in traumatic amputees, phantom pain was related to preamputation pain only immediately after the amputation ( ). The relationship between preamputation pain and phantom pain has been confirmed in prospective studies ( ). In the study by Nikolajsen’s group, a relationship between preoperative pain and phantom pain was found 1 week and 3 months after the amputation, but not later in the course. However, phantom pain never developed in some patients with severe preoperative pain, whereas it did develop in others with only modest preoperative pain ( ).
The complexity of the relationship between preamputation pain and phantom pain is supported by the notion that phantom pain develops in patients with traumatic amputations, some of whom never experienced pain before the amputation, to the same extent as in patients with long-standing preamputation pain who undergo amputation for medical reasons. In addition, Lacoux and associates examined 40 upper limb amputees who had lost their limbs following injury by a machete, axe, or gunshot during the civil war in Sierra Leone. About half the amputees (56%) lost their limbs at the time of injury (primary), whereas the remainder had an injury and subsequent amputation at the hospital on average 10 days after the injury (secondary). It is reasonable to assume that the latter group suffered from severe pain between the two events. However, there was no correlation between the development of phantom pain and whether the amputation was primary or secondary ( ).
Another issue concerns the extent to which pain experienced before the amputation may survive as phantom pain. Striking case reports show that phantom pain may mimic preamputation pain in both character and localization ( ). In a retrospective study by , 68 amputees were questioned about preamputation pain and phantom pain from 20 days to 46 years after amputation. Fifty-seven percent of those who had experienced preamputation pain claimed that their phantom pain resembled the pain that they had before the amputation. The number of patients with similar descriptions of preamputation pain and phantom pain was much lower, however, in two prospective studies ( ).
In the study by Nikolajsen’s group, the character and localization of pain were recorded before and at specific intervals after the amputation. Although 42% of patients claimed that their phantom pain was similar to the pain that they experienced before the amputation, the actual similarity when comparing pre- and postamputation descriptions of pain was not higher in patients who claimed similarity than in those who found no similarity between phantom pain and preamputation pain ( ). Thus, retrospective memories about pain should be judged carefully. It is likely that pain experienced preoperatively may survive as phantom pain in some patients, but this is not the case in the vast majority of patients.
Psychological Factors
Amputation of a limb is a traumatic experience in most patients, and many amputees exhibit a range of psychological symptoms such as depression, anxiety, self-pity, and isolation. In a survey of 914 amputees, depressive symptoms were shown to be a significant predictor of the intensity of phantom pain ( ). As with other chronic pain conditions, coping strategies are important for the experience of pain ( ). Passive coping strategies, especially catastrophizing, are associated with phantom limb pain ( , ). Other psychosocial factors, as, for example, social support, also play an important role in the adjustment to phantom pain ( , ).
Others have looked at pain-related disability and rehabilitation ( ). The impact on working life is especially relevant for amputees who become handicapped at a young age. examined the occupational situation of people with lower limb amputations in The Netherlands and found that amputees who experienced a long delay between the amputation and return to work had difficulty finding suitable jobs and had fewer opportunities for promotion.
Other Modulating Factors
Phantom pain may be modulated by several other internal and external factors, such as attention, distress, coughing, urination, and manipulation of the stump. It is unclear whether the use of a functionally active prosthesis as opposed to a cosmetic prosthesis reduces phantom pain ( ).
Both experimental and clinical studies have shown a significant genetic contribution to the development of chronic pain, including neuropathic pain after nerve injury ( ). However, an inherited component is not always a feature of phantom pain. described a case in which five members of a family sustained traumatic amputation of their limbs. The development of phantom pain was unpredictable despite the individuals being first-degree relatives.
It has been claimed that phantom pain may be provoked by spinal anesthesia in lower limb amputees ( ). However, prospectively investigated 23 spinal anesthetics in 17 patients, and phantom pain developed in only 1 patient but resolved in 10 minutes.
Phantom Sensations
Phantom sensations are more frequent than phantom pain and are experienced by nearly all amputees (see Table 64-1 for details). Phantom sensations rarely pose any major clinical problem. The two phenomena are strongly correlated. In a study by Kooijmann’s group, phantom pain was present in 36 of 37 upper limb amputees with phantom sensations but in only 1 of 17 without phantom sensations ( ).
As with phantom pain, non-painful sensations usually appear within the first days after amputation ( ). The amputee frequently wakes up from anesthesia with a feeling that the amputated limb is still there. Immediately after amputation, the phantom limb often resembles the preamputation limb in shape, length, and volume. Over time the phantom fades, but sensation in the distal parts of the limb remains. For example, upper limb amputees may feel hand and fingers, and lower limb amputees may feel foot and toes.
A common position of the phantom in upper limb amputees is that the fingers are clenched in a fist, whereas the phantom limb of lower limb amputees is commonly described as toes flexed ( ). In some cases, phantom sensations are very vivid and include feelings of movement and posture; in other cases, only suggestions of the phantom are felt. Telescoping (shrinkage of the phantom) is reported to occur in about one-third of patients. The phantom gradually approaches the amputation stump and eventually becomes attached to it. Sometimes it may even be experienced within the residual limb ( Fig. 64-2 ). It has been postulated that phantom pain prevents or retards shrinkage of the phantom, but Montoya and co-workers failed to find such a relationship: 12 of 16 patients with phantom pain and 5 of 10 patients without pain reported telescoping ( ).
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