He Phantom limb pain Is an alteration of the corporal consciousness, derived most of the time from unilaterally located alterations in the cerebral hemispheres.
It is a complex phenomenon, described extensively in the literature but of which we do not have a convincing explanation or conclusive treatments.
It is experienced by 80% of those who have undergone amputation of a limb, although it is now known that these sensations may appear after the amputation of any appendix.
The feeling you have is that the amputated limb is still connected to the body and is working with the rest of it. According to various studies, between 70% and 100% of the amputees report experiencing non-painful exteroceptive sensations (eg itching, the shape and movement of the fingers...) coming from the phantom limb. For 60-85% of these patients, these sensations are painful and involve exaggerated feelings of tingling, itching, burning, pressure, cramps, pruritus and numbness.
The phenomenon is associated with the previous integration of the limb to the corporal scheme and with the rapidity of the amputation. For example, patients who gradually lose their fingers for leprosy do not experience this phenomenon, whereas if the residual stump is amputated the experience appears. Therefore, it must be taken into account that this phenomenon does not occur with absent members congenitally.
Throughout the years of investigation, the following factors or relevant parameters have been identified: the severity of the initial lesion, the duration and intensity of the pain prior to amputation, the age of the patient (very little prevalent in children under 6 years).
Historical aspects
Ambroise Paré describes in 1551 the different phenomena related to the persistence of sensory perception after the amputation of a limb.
However, it is not until 1871, when the term"Phantom limb pain"begins to be used to describe the symptoms of soldiers in the American Civil War after the amputation of a limb.
Differences between sensation and pain of the phantom limb
It is important to differentiate between phantom limb sensation and phantom limb pain. As for the sensation it is a non-painful perception of the continued presence of the amputated limb and its appearance reaches almost 100% during the first month after the amputation.
On the other hand, pain is the painful sensation originating in the amputated portion of the limb. The incidence is close to 85%, although it usually decreases with the passage of the months partially. Its incidence and severity increase in proximal amputations and in cases of poor analgesic control prior to amputation.
The likelihood of phantom limb pain is greater after amputation of a limb with chronic pain, and in many cases the pain is similar to that experienced in the limb before amputation. This type of pain is less likely in children and almost unknown in congenital amputations.
The sensations of the phantom limb may appear right after limb amputation or late, but usually appears within the first week amputation. There is usually a reduction in frequency as well as pain crises, but pain may persist for years.
Pathophysiology of the phantom limb
The severity of the pain of amputees and their detailed description of these sensations suggest the existence of certain physiological mechanisms that constitute the neurobiological basis of the phantom limb.
The intensity of pain depends on peripheral and central factors. However, the influence of psychological factors on their evolution and intensity must be taken into account, since the perception of pain intensity is closely related to the emotional states and levels of anxiety, stress and depression experienced by the patient. During this period. In addition, such chronic pain seems to modify the personality of the patients.
Among the peripheral factors we highlight the influence of:
- Muscle tension.
- The superficial blood flow.
- Ectopic discharge.
With respect to muscle tension , Thanks to techniques such as Electromyography , It has been observed that the changes produced in this one precede changes in the painful sensations of spasms and compression in the phantom limb that can last several seconds.
Many people who have been amputated have stated that the pain diminishes with activities that reduce muscle contraction of the residual limb and increases with activities that raise the overall levels of contraction.
Therefore, some of the treatments performed so far are aimed at reducing muscle tension in the residual limb, influencing pain.
With respect to Superficial blood flow in a limb , Studies have been carried out that have found that the nerve endings of the stump remain sensitive to the stimuli; That the decrease in blood flow in the extremity causes a decrease in its temperature (lower in the distal extremity than in opposite points) and that the activation rates increase when the nerve endings become cold.
Kristen et al. Observed that amputees with phantom limb pain present alterations in temperature in the residual limb compared to others without amputations.
Other studies demonstrated the existence of an inverse relationship between the intensity of phantom limb pain and the temperature in the residual limb, compared with that of the intact limb only in people who described the pain as burning, throbbing, and tingling.
It was seen that in people who described pain as such, a relationship was found between the blood flow in the stump and the intensity of pain and a relationship between the immediate change in pain intensity when blood flow varied.
Through techniques such as Thermography It has been shown that this decrease in blood flow is not associated with generalized sympathetic system hyperactivity. Since this decrease in temperature is limited to the limb amputated. The intact member maintains its temperature.
In addition, by means of sympathetic blocking procedures (interruption of nerve transmission for a more or less long period of time), there have been reductions in the intensity of burning pain of the phantom limb, but not the pain described with adjectives different from those previously seen . These two are reasons that confirm that the cause of the phantom pain can be vascular.
Other treatments used may be the use of beta-blockers such as Propanolol , Which dilate peripheral blood vessels and reduce short-term pain.
If we look for a relationship between muscle tension and blood flow, we can conclude that the former appears to be mediated by the latter. That is, the increase in muscle tension seems to be mediated by the decrease in superficial blood flow.
Finally, the production of Ectopic discharge (Discharges that occur outside the place in which they should be produced), neuromas or benign tumors that arise after amputating a limb. Although, it must be taken into account that the formation of a neuroma and the appearance of phantom pain depend on the type of amputation, the stimulation of the stump and the person's predisposition to neuropathic pain. These discharges may be caused by stimulation of the stump, or spontaneously.
Regarding the central factors, studies have been carried out on the reorganization of the primary somatosensory cortex after amputation and the suppression of afferent impulses in adult animals.
Ramachandran et al. Observed that in a patient with a phantom limb who claimed that he had an itchy hand on his amputated hand, by scratching the patient on the face with a cotton swab, they verified that the patient's itching sensation diminished.
This explanation is supported by the existence in people of a cortical map of body representation where there is a univocal correspondence between motor and somatosensory aspects (Penfield Homunculus).
In this map is represented each part of the body in function of its importance sensorimotor, that is to say, the lips or the hands have more cortical representation than the trunk, for that reason they are more sensible.
If a person loses an arm or a leg, their representation on that map ceases to receive information from that effector, however, that area may be invaded by the adjacent representation. For example, if a hand is amputated, the adjacent representation is that of the face. Thus the stimulation of the face can make a hand feel (ghost).
Birbaumer et al. Suggest that in some amputees, cortical reorganization and phantom limb pain may be maintained by peripheral impulses, while in others, intracortical changes are more important.
In short, a complete explanatory model of the onset of phantom limb pain should include both peripheral and central factors as well as to assume that nociceptive memories established prior to amputation can effectively activate phantom limb pain.
The development of this somato-sensorial nociceptive memory, responsible for the perpetuation of pain, depends on aspects such as:
- The pain and stress caused by it before the amputation.
- The time that passed between the pain and the amputation (the smaller this one, the greater probability of perpetuation of the picture).
- Intensity of pain prior to amputation and the existence of more complex nerve impulses in situations related to the moment of pain (odors, visions of injuries...).
- This, together with the triggered anxiety can give rise to the syndrome of chronic post-traumatic pain.
Treatment of phantom limb pain
The treatment of this pain picture continues to be a challenge, since they remain pathologies of difficult analgesic control. In recent years, greater emphasis has been placed on pain prevention, avoiding the creation of the somato-sensory memory that I mentioned earlier.
In the preoperative period, patients should be informed by informing them that after amputation they should expect a phantom sensation, which is normal and is not harmful. In the postoperative period, they should examine the stump regularly, controlling its appearance, sensation and function. In addition, a way to prevent is by placing a functional and esthetic prosthesis, as soon as possible.
Phantom limb pain has been involved from different perspectives, but the analysis of the consequences of these treatments on patients shows the ineffectiveness of those that do not influence the underlying mechanisms.
Thus, patients who learn to control blood flow in the phantom limb can relieve their burning pain, and those who learn to control muscle tension control spasmodic phantom pain.
As for the Pharmacological treatment , It has been found that the long-term effectiveness of opioids, NMDA receptor antagonists, anticonvulsants, Antidepressants , Calcitonin and anesthetics that influence pain, functionality, mood, sleep, quality of life, satisfaction and adverse effects are not very clear.
Inside of the Neuropsychological treatment Useful techniques have been described Biofeedback And hypnosis in the treatment of amputated patients who did not present significant psychiatric alterations.
Sherman reports that patients with spasmodic pain benefit from biofeedback of muscle tension and patients with burning pain benefit from temperature biofedback.
On the other hand, Ramachandran, based on his theory about what happens in patients with phantom limb pain, creates a mirror box. This box contains a mirror located in the center, when the patient inserts his limb without amputating, can see the reflection of his arm in the mirror, and thus feel that the member is present despite being amputated. The patient moves the arm, and through the use of visual feedback and by eliminating potentially painful positions, is able to give feedback to the brain and relieve the pain it feels.
The underlying explanation is that the brain decodes the new information automatically, without the patient needing to believe it. Given the incongruity that the brain receives, it resolves it by discarding the signals coming from the amputated limb, so that the memory footprint of the phantom limb is swept away by the new information that enters the visual pathway.
Ramachandran recommends that for this technique to be effective, exercises should be repeated daily for a minimum of 5 to 10 minutes, for a minimum of three weeks. In this way it would be giving an over-learning phenomenon with which the old and painful information would be gradually deleted from the memory of the brain by new visual information that the member is healthy.
It would be a virtual reality that offers a signal of external visual feedback, which extinguishes the previous memory footprint.
On the other hand also makes use of techniques of treatment of muscular rehabilitation like muscular enhancement, postural hygiene, analgesic electrotherapy, massages and tactile stimulation.
conclusion
As you can see the lines of research on phantom limb pain have been diverse, trying to respond to this phenomenon so peculiar that it affects the majority of people who have undergone an amputation. Thus, we have studied the pathophysiological, psychological aspects involved, as well as intervention strategies aimed at the palliative treatment of pain.
However, there is still a way to go and a possible approach would be to have these patients to assist in the design of future interventions...
Bibliography
- Flor, H., Birbaumer, N. and Sherman, R.A. (2001). Phantom limb pain. Revista Española del Dolor, vol. 8, p. 327-331.
- Ford AH, Shannon C. Phantom pain. In: Abrams BM, Benzon HT, Hahn MB, et al, editors. Practical treatment of pain, third edition. Madrid: Harcourt-Mosby; 2002. p. 223-34.
- Nikolajsen L, Ilkjaer S, Kroner K, et al. The influence of reamputation pain on postamputation stump and phantom pain. Pain Sep 1997; 72: 393-405.
- Olarra, J. and Longarela, A. (2007). Phantom limb sensation and residual limb pain after 50 years of amputation. Revista Española del Dolor, vol. 6, p. 428-431.
- Image source.