Exploring the Phantom Phenomenon from a Psychophysiological Perspective

ABSTRACT

The purpose of this investigation was to examine historical perspectives regarding causal mechanisms of phantom limb pain while considering contemporary evidence that suggests the phantom phenomenon is more than a physiological event. Fifty participants who had experienced lower extremity limb amputation, and who had received prosthetic rehabilitation, completed four instruments designed to measure the primary predictor variables of physical, social, and emotional satisfaction, demographic variables, and criterion variables that included personal well-being and phantom pain. The Trinity Amputation and Prosthetic Experience Scales (TAPES) were used to assess the primary predictor variables. The demographic variables were measured using a supplement to the TAPES inventory. Personal well-being was operationally defined by scores on the Beck Depression Inventory II (BDI-II), and the remaining criterion variable, phantom pain, was measured by specific questions from an additional supplement to the TAPES inventory. Demographic variables were eliminated as significant predictors of general well-being or phantom pain. Physical, social, and emotional experiences of amputation were interrelated and represented 68% of common variance with general well-being. Physical, social, and emotional experiences of amputation were relatively statistically equal in predicting levels of general wellbeing. Relationships among physical, social, and emotional satisfaction, general well-being, and phantom pain were statistically significant where p < 0.05. Regression analysis revealed 75% common variance between TAPES and phantom scores and depression scores. Social experience was revealed to be the only significant variable as a predictor of phantom pain in the absence of depression. The results call into question traditional methods of phantom pain management and suggest that psychological strategies that improve social and emotional experiences need to be investigated as alternatives or augmentations to traditional physical approaches.

INTRODUCTION

When limb amputation becomes necessary it is reasonable to expect that the victim of limb loss will have significant and complex issues to resolve. The pain associated with disease or trauma has been replaced and sometimes coupled with the pain of surgery, and the psychological implications of the affliction have become psychological implications of body image and body damage(1). One of these issues of immense complexity and profuse suffering is that of experiencing the phantom limb(2). Also, the degenerative effect that pain can have on the immune system is of formidable concern(3). Each of the aforementioned represents 2 a potential compromise to personal well-being and can exist within the continuum of physical, social, and emotional experience as either a catalyst or a culmination. If proportions of influence among major categories of experience, general wellbeing, and pain phenomena can be determined, future identification of causal mechanisms of phantom pain might be more easily identified and managed.

THE PHANTOM PHENOMENON

Phantom limb pain is one of the most fascinating and complex clinical pain syndromes. The experience of the phantom limb is not always described as painful, yet the sensation of the missing limb being intact after amputation is extremely prevalent. Phantom limb sensation has been shown to be present in 65% of amputees 6 months after amputation, and in 60% at 2-year and 7-year intervals(2). The majority of amputees report phantom limb sensation immediately after surgery. It is typically described as a tingling feeling in which the original shape of the amputated extremity is perceived. The phantom limb reacts the same when moving, sitting, and lying down, and the tendency for the missing extremity to feel present has caused some amputees to step out of bed expecting their foot to touch the floor, or to reach out to grasp an object with a missing hand. With time the shape of the phantom extremity begins to change and there is sometimes a "telescoping" effect in which the foot or hand begins to recede back into the body until it seems to be attached right at the stump. In some cases the phantom foot or hand subsequently disappears. It has been suggested that the central nervous system produces the phantom in response to lack of normal input and that it manifests as a neural substrate of our perception of body position(2). About 50% of amputees experience phantom pain classified as chronic or severe(4). Phantom limb pain is described as cramping, shooting, burning, or crushing and is reported periodically to frequently in those who experience it. The pain may vary with respect to quality and intensity. Rather than simply feeling the shape of the absent extremity, those who suffer phantom limb pain sometimes report the feeling that the appendage is contorted. Phantom pain can be triggered by emotional upsets as well as bodily functions(2). Phantom pain may endure long after the tissue damaged from disease and surgery has healed and "trigger zones" may spread to healthy areas of the body(2).

PHANTOM PAIN AND THE BRAIN

The experience of the phantom limb is realistic to the limb loss patient because the same brain processes that are present when the body is intact remain present after amputation(5). The research of Ronald Melzack describes the body as being unitary with an integrated quality that includes the "self" and the incorporation of a neural network that can be changed by sensory experience although the "body-self" is genetically determined. Melzack describes experiences of the body as having a quality of self, thereby influencing the individual's perception and response to pain. Historically, there has been controversy in determining the causal mechanisms of the phantom limb. The major problem is the attempt to identify a single problem as the entire explanation when it is more likely that there are a variety of contributing factors. Recent research in psychological science emphasizes a progression from the periphery to the central nervous system as a means of explaining the phantom limb phenomenon(2). However, more than 40 types of therapy to address phantom limb pain have been described, with a success rate of about 15%(2). This is understandably frustrating to the individual who suffers limb loss. It is more frustrating to the individual who has experienced disease and pain resulting in amputation only to experience little or no relief once the amputation is performed. This low success rate is indicative of predominant confusion regarding the mechanisms that underlie phantom limb pain.

Psychological evidence suggests that perceptual experience is influenced by past history and current state of mind(5). In other words, state of mind, or emotion, under certain circumstances may determine responses to pain or pain sensation thresholds. Phantom limb pain perplexes the investigation by beginning as signals of serious body damage and may persist, spread, and increase in intensity to the point that it becomes a malady in its own right because the pain may become worse than the original injury that caused it. Evidence reveals that prolonged pain can have deleterious effects resulting in immunosupression due to extended periods of stress, anxiety, or depression(3).

PAIN, STRESS, AND IMMUNOLOGIC COMPROMISE

It has been determined that the consequences of stress on the immune system can be delineated, that there are measurable differences in the immune systems in both humans and animals under conditions of stress, and that individual patterns of affective, behavioral, and cognitive responses significantly influence reaction to stress and physiologic consequences(6,7). Whether the stress in question is classified as a major or minor event also may play an important role in the immune response. The stress-pain connection may be a reciprocal event. Not only does pain produce stress, which contributes to immunologic consequences, but also prolonged stress may produce a predisposition to chronic pain. This is supported by research investigating the stress responses of individuals suffering from temporomandibular pain, fibromyalgia, and unrestorative sleep(8-10). Stress has been identified as a predictor of both pain and depression, and life-stress and depression have been associated with experiences of chronic pain(11,12). Specific to the phantom phenomenon, there is evidence that the impact of stress on pain intensity suggests a connection between the long-term emotional memory of amputation and the occurrence of phantom pain(13).

Other examples of stress producing pain with physiological consequences include work-related stress and musculoskeletal pain with catecholamine compromises, elevated blood pressure, increased heart rate, and psychosomatic symptoms(14); chronic psychoemotional stress and reduced pain thresholds(15); stress producing injury and resulting prolonged chronic pain(16); posttraumatic stress disorder, alterations of HPA axis, and chronic pain(17); and the development of pain in pain-free subjects after prolonged mental stress(18).

Degenerative disease processes along with major stress producing constructs such as bereavement have been shown to have significant influences on immunologic responses. Increments in CD4 cell counts of HIV patients in a controlled bereavement support group were associated with lower levels of stressors, while higher levels of grief were associated with negative physiologic response(19).

DEPRESSION AND DISABILITY

Depression is defined as a state of low mental vitality or dejection and is a generic term that has been used to explain a variety of disorders. Situational and biological depression may present interactively or exclusively in related or unrelated phenomena. Depression in the elderly is generally reported differently than the depression of middle-aged or younger counterparts specifically with increased somatic concerns and less guilt. Hypochondriasis, psychotic depression, and pseudodementia are more prevalent with age. Physical illnesses, sociological considerations, and other psychological concerns may also play an interactive role. Many times depression is used as a barometer to determine personal well-being. The following themes are consistent in many individuals diagnosed as depressed(20):

1. Depressed mood most of the day nearly every day.

2. Markedly diminished interest or pleasure in all or almost all activities most of the day.

3. Significant weight loss or weight gain.

4. Insomnia or hypersomnia nearly every day.

5. Psychomotor agitation or retardation nearly every day.

6. Fatigue or loss of energy nearly every day.

7. Feelings of worthlessness or excessive or inappropriate guilt.

8. Diminished ability to think or concentrate.

9. Recurrent thoughts of death, suicidal ideation, or a suicide attempt.

The aforementioned characteristics have remained static over time for determining depression and were utilized as a basis for diagnosis in the Diagnostic and Statistical Manual of Mental Disorders (3rd Ed.), [DSM-III]. The newer version, DSM-IV-TR, no longer states a requirement of the presence of five of these characteristics; however the same qualities remain inherent in determining higher and lower levels of depression as well as depressive symptoms as defined by the more recent manual.

Depression may vary in depth from neurosis to psychosis. There are many variables that can result in the affliction of a depressive state, and various circumstances of life situations may determine how depression is handled, as well as how it should be treated. For instance, sexual abuse early in life may set the stage for the predisposition to a depressed state due to low self-esteem. Likewise, attachment styles that are developed in infancy and early childhood may influence the method by which individuals cope with depressive symptoms. Major depression might also be genetically determined.

Individuals who are diagnosed as depressed may exhibit depression in any or all stages of the life cycle. Furthermore, depression may be manifested prior to, during, or just after major life events. Onset of disability is a salient example of major life events that produce depression.

AMPUTATION AND WELL-BEING

Among individuals with various types of disabilities, those who experience limb amputation display more indecisiveness, thoughts of death, and thoughts of self-harm(21). Restriction of activity is interrelated with public self-consciousness, depression, reluctance to go out in public and feelings of vulnerability(21,22). Perceived social stigma has been found to contribute significantly to depression(23). Those who experience amputation exhibit a broad spectrum of psychological responses that range from extreme despair to feelings of relief after eliminating the source of pain.

Perceptual changes after amputation are a potential source of emotional despair. Magnetic source imaging has revealed that organizational and perceptual changes correlate with the number of sites from which painful stimuli can evoke referred sensation. Phantom limb pain can mediate depressive symptoms, especially when the phantom limb is evoked by unrelated body functions(24). Modification of the sense of self, sense of loss, awareness of mortality, loss of confidence, disfigurement, loss of balance, guilt, and phantom limb sensations are among the traumatic effects of amputation that can cause this population to have a bleak outlook for the future(25).

SUMMARY

The connection among physical experience, physiological response, and psychological outcome is well established. Physical identity is a construct in which appearance, competence, and limitations combine to develop a sense of self and depend heavily on the individual's capability to function physically(26). Pain processing in the brain, the role of pain and stress in immunological decrement, and depressive tendencies are considered as catalysts for disturbing physical identity and evoking the phantom limb. The study at hand investigated physical, social, and emotional life experiences as a continuum that when disrupted contributed to a relationship between distress and phantom pain. Specifically, each category in the life experience continuum was measured against the criterion variables of distress and phantom pain to determine the relative predicting power of each category.

METHOD

SAMPLE AND SELECTION

The sample comprised 50 individuals who had experienced surgical removal of a lower-extremity, had received prosthetic management, and were capable of ambulation with their prostheses. There were 13 females and 37 males. Forty participants had transtibial amputations and 10 participants had transfemoral amputations. Thirty-five participants had amputations due to disease, 12 due to trauma, and 3 were congenital. Age range of participants was 32 years to 80 years with M=56.6. The qualifying criteria were that each patient (a) had a lower extremity amputation, (b) was 21 years of age or older, (c) had received and had been using a prosthesis, (d) was capable of ambulating with his or her prosthesis, and (e) had been ambulating with his or her prosthesis for at least 3 months. Each participant completed four instruments including: (a) the Trinity Amputation and Prosthetic Experience Scales (TAPES)(27), (b) the TAPES demographic survey, (c) The Beck Depression Inventory II (BDI-II)(28), and (d) the TAPES phantom pain survey.

TAPES

The TAPES instrument was developed to better understand the experiences of those who suffer limb loss from a multidimensional perspective. The occurrence of limb loss produces many challenges, the most obvious being that of learning to use a prosthetic limb. This obvious physical challenge leads to social and psychological adjustments as well. Research supports TAPES as an instrument that allows indepth examination of physical, social, and emotional functioning by asking questions directly related to issues of postamputation experience and specific issues regarding prosthesis use. TAPES is a 54-item multidimensional self-report instrument that investigates psychosocial issues, activity restriction, and qualitative satisfaction with a prosthetic device. Factor analysis regarding psychometric evaluation of TAPES was used by its developers to reveal subscales including adjustment, restriction, and satisfaction in each of the domains of inquiry. Each subscale crossed the boundaries of the major continuum and provided the impetus for this study. Specifically, extraneous influences represented by the various subscales and measured as psychosocial, activity, and satisfaction issues are purported to be influences affecting depression measures after rehabilitation. Furthermore, studies regarding clinical depression after amputation have revealed a range of 21% to 35% of all limb loss patients(27), providing incentive for investigation into the postamputation-rehabilitation-depression continuum.

DEMOGRAPHIC SURVEY

The demographic survey included a variety of questions regarding personal information about the participants and was provided as a means of assessing variances among demographic variables as they pertained to amputation experiences and relationships with well-being and phantom pain. Information included but was not limited to age, gender, months elapsed since amputation, amputation level, and diagnostic category. For the purpose of this study nominal variables were not included in the primary analysis. The interval variables of age and months elapsed since amputation were included in the primary analysis to maintain At least a 10:1 ratio between participants and variables examined.

BDI-II

The BDI-II was developed to identify depressive disorders based on the criteria of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV). The BDIII was appropriate for this study because it addresses four items pertinent to the mental processes of those who experience amputation: (a) agitation, (b) feelings of worthlessness, (c) concentration difficulty, and (d) loss of energy. It is a survey designed to indicate the presence and degree of depressive symptoms rather than an instrument for clinical diagnosis. Appropriateness of the BDI-II was further supported because the intent was to investigate relationships among multidimensional postamputation experiences, depressive symptoms, and phantom pain, not diagnose for the purpose of clinical treatment. The BDI-II is a 21-item self-report instrument designed for individuals at least 13 years of age.

PHANTOM PAIN SURVEY

Two specific questions from the TAPES phantom pain inventory were used to analyze phantom pain in the 50 participants. The two questions were as follows:

1. Do you experience phantom limb pain?

2. How much did phantom limb pain interfere with your normal lifestyle during the last week?

The questions were scored on a Lichert scale and entered into a regression analysis with the TAPES, BDI-II, and demographic variables.

DATA ANALYSIS

Data analysis was performed using SPSS 11.0(29) for windows. Frequency distributions, descriptive statistics characterizing distribution, dispersion, and central tendency values as well as parametric and non-parametric tests were used to analyze the data.

Pearson r correlation analyses, which determined the significance of bivariate relationships among the interval level data, were used to examine the relationships between each predictor variable represented by the subscale scores on the TAPES instrument, the interval level demographic variables, the BDI-II scores, and the phantom pain scores. Each of the primary predictor variables, represented by the subscale measures on the TAPES instrument, along with the continuous demographic variables of age and months elapsed since amputation, were entered into a regression analysis. The TAPES scores, BDI-II scores, and phantom pain scores were entered into a multiple regression analysis. Backward regression analysis provided a determination of the individual values of the significant variables. An analysis of variance (ANOVA) was a product of the regression analysis that measured significant differences, not attributed to chance, between the means of the variables. Other products of the regression analysis, the independent t tests, determined the proportion each predictor variable contributed to the criterion variables and produced beta values that measured the proportions of statistical significance for the primary variables.

Figure 1. Bar graph of raw data distributions for sum of the TAPES scores.

Table 1. Pearson r bivariate correlation analysis of all primary variables.

RESULTS

Raw data distributions for scores on each subscale of the TAPES instrument revealed a symmetrical distribution for each category (Figure 1). The distribution of scores on the BDI-II was negatively skewed with a mean of the combined scores of 9.56, a median score of 7, and a skewness value of .901 (Figure 2). Sixty-eight percent of participants (34 where N=50) reported some degree of phantom pain. The Pearson r correlation analysis revealed significant values for each bivariate relationship among the primary predictor variables and the criterion variables of depression and phantom pain where p < 0.05 (Table 1). The regression analysis determined that significant degrees of common variance existed between each primary predictor variable and the depression variable. Age and "months elapsed since amputation" were revealed not to be statistically significant and were eliminated from the regression analysis. Stepwise regression analysis automatically eliminated the continuous demographic variables and revealed substantial common variances between the primary predictor variables measured by the TAPES instrument and the criterion variable of depression. Multiple regression analysis revealed substantial common variance between the TAPES and phantom pain scores and the BDI-II scores.

Figure 2. Bar graph of raw data distributions for scores on the BDI-II.

Table 2. Model summary of stepwise regression of primary predictors and depression variable.

The social experience variable was revealed as the variable sharing the majority of common variance with depression at 55%. The emotional experience variable explained 8% of common variance with depression, and the physical experience variable contributed the least common variance of the predictor variables to depression at 5%. Clustered together, the predictor variables and the depression variable shared 68% common variance. Table 2 provides the model summary for the stepwise regression analysis of the primary predictors and the depression criterion. Figure 3 provides a visual illustration of the linearity among the primary predictors and the depression criterion.

Figure 3. Scatterplot of sum of TAPES and BDI-II scores.

Table 3. ANOVA from regression analysis of non-eliminated variables.

The regression analysis for the TAPES, BDI-II, and phantom pain scores revealed 75% common variance between TAPES and phantom pain and BDI-II. Significant F ratios produced by the ANOVA indicated that the hypothesis of a correlation among physical, social, and emotional experience, phantom pain, and depression should be accepted (Table 3). Figure 4 provides a 3-dimensional visual representation of the scores for each variable. Independent t tests produced beta values that revealed proportions of significance of the TAPES variables and phantom pain variable to be relatively equal as statistically significant predictors of personal well-being as defined by the BDI-II scores (Table 4). When the physical, social, and emotional experience variables were entered into a multiple regression analysis with phantom pain as the dependent variable, social experience was the only variable retained as a significant predictor of phantom pain (Table 5).

Figure 4. 3-D scatterplot of TAPES, BDI-II, and phantom pain scores.

Table 4. Proportions of significance from Independent t tests.

Table 5. Multiple regression with depression absent and phantom pain representing the dependent variable.

DISCUSSION

The research hypothesis for this study was as follows: Individuals who suffer limb loss will report relationships among postamputation experience as measured by the TAPES instrument, distress as measured by the BDI-II, and phantom pain. The research hypothesis was directional in that depression and phantom pain scores were expected to decline as predictor variable scores increased. The null hypothesis assumed that there would be no statistically significant relationships among selfreported measures of unsatisfactory postamputation experience, depression, and phantom pain. Beta and t values supported the rejection of the null hypothesis with 95% certainty that a Type II error, rejection of the null hypothesis when it is in fact true, had not occurred.

The literature supports the concept of physical, social, and emotional experience contributing to the whole of well-being. Support between the literature and this study was reciprocal. The study confirmed inferences in the literature pertaining to the importance of an undisrupted continuum of positive experiences in the physical, social, and emotional realms, and the literature anticipated the findings of this study; the "whole" of well-being is best predicted by an undisrupted continuum that includes the three aforementioned domains of experience. The literature overwhelmingly supports that multidimensional approaches to health care are beneficial, and the results of this study confirmed the claims of the literature. Statistical analysis determined that the physical, social, and emotional realms were overlapping and intermingling. Each domain of experience shared common variance with the others, yet values supported the ideology that while all are important, under specific circumstances, each domain is not equally important. This became apparent when the depression and phantom pain variables were entered into the regression equations with the primary predictor variables. The social component emerged as the category most likely to predict predisposition to depressive symptoms as well as being the only significant predictor of phantom pain in the absence of depression. Furthermore, the results demonstrated that individuals were more predisposed to phantom pain as severity of depressive symptoms increased.

The presence of disease, amputation surgery, and disability in general represent disruptions of the physical domain. At face value, it would be reasonable to conclude that isolation of the experiences in the physical domain would preclude psychological disturbance. Since psychological disturbance has been shown to increase risk for pain syndromes, it would appear that drug treatment would effectively manage most occurrences of phantom pain. However, results of the study indicate that upon occurrence of disease and physical detriments that follow, disruption spreads from the physical realm into social and emotional realms of experience. Disease and amputation are physical processes that invade the social and emotional realms. Not only are a disease cause and psychological effect implied, but interaction between physical and mental processes have been substantiated to the following extent. Disease and pain cause psychological disturbance, psychological disturbance can cause pain and disease, and stress-producing pain can result in physiological compromises. Those who experience disease are at risk for stress-produced physiological decrements, and those who experience psychological detriments in the social or emotional realms are at risk for deleterious physical effects. The results of this study indicate that as phantom pain begins to assume a social and emotional identity in addition to a physical identity, treatment success begins to decline.

The concept of a physical, social, and emotional continuum that is overlapping and mutually contingent has been statistically tested and revealed to be a dynamic force that significantly influences personal well-being. Microcomponents of the primary categories have been established by prior studies and in many cases have been shown to originate in a primary domain and influence other domains, or exist simultaneously in multiple domains. The results of this study have revealed another continuum that includes personal experience, well-being, and phantom pain, and suggest that traditional drug therapies for the treatment of phantom pain might in fact be less successful when depressive symptoms are not present.

CONCLUSIONS

The purpose of this study was to investigate relationships among physical, social, and emotional experiences of amputation, personal well-being, and phantom pain. A significant negative correlation was revealed between physical, social, and emotional experiences of amputation and well-being. A significant negative correlation was revealed between well-being and phantom pain. Finally, a significant negative correlation was revealed between social experience and phantom pain. While the relationships between variables could not within the chosen design be confirmed as causal, the overwhelming significance indicators support the need for consideration of non-traditional approaches in the treatment of those who experience amputation and specifically those predisposed to phantom pain.

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