In 2005, there were 1.6 million people living with limb loss in the US, 60% to 85% of whom suffer from phantom limb pain.1 Phantom limb pain refers to a variety of nociceptive perceptions – ranging from a slight, tingling to a sharp, throbbing pain – perceived in a limb or organ that is physically not present.1 Risk factors associated with phantom limb pain include pain before the amputation, cause of amputation, prosthesis use, and years since amputation.1 Commonly classified as neuropathic, phantom limb pain is presumably related to damage of the central and peripheral neurons.2 As a basic mechanism, the neuromatrix theory proposes that a network of neurons extending into widespread areas of the brain, defined as the neuromatrix, composes the “anatomical substrate of the physical self.”3 Following amputation of an extremity, abnormal impulses can change the neuromatrix pattern, which causes conversion of normal input to pain sensation, i.e. phantom limb pain.3 Although the neuromatrix and other theories provide some insight into the mechanisms of phantom limb pain, a rigorous understanding eludes researchers. Considering that 3.6 million people will live with limb loss in the US by 2050, it is essential to develop therapeutic approaches to attenuate this condition perioperatively.1
Many studies on phantom limb pain focus on methods to prevent postoperative problems via perioperative epidural infusions.4,5 For example, Jahangiri et al found that perioperative epidural infusion of diamorphine, clonidine, and bupivacaine is safe and effective in reducing the incidence of phantom limb pain based on a controlled study of 24 patients undergoing lower limb amputation.5 Of more relevance, there is also a growing literature on the effects of different anesthetic techniques on phantom limb pain.
Ong et al investigated the effects of epidural, spinal, and general anesthesia on pain after lower limb amputation. The study included a cross-sectional survey of 150 patients evaluated 1 to 24 months after their lower limb amputation.6 In the week after surgery, patients receiving epidural anesthesia and patients receiving spinal anesthesia reported significantly less pain than patients receiving general anesthesia.6 After 14 months, there was no difference in stump pain, phantom limb sensation, or phantom limb pain between patients who received epidural anesthesia, those who received spinal anesthesia, and those who received general anesthesia.6 Based on their findings, Ong et al concluded that patients receiving either epidural or spinal anesthesia may experience reduced phantom limb pain in the first week after amputation.6
Ugur et al performed a retrospective study to evaluate the effects of different anesthesia types on phantom limb sensation and phantom limb pain. The researchers mailed a questionnaire to patients who underwent lower extremity amputation between 1996 and 2003 at Erciyes University Hospital.7 In total, 40 patients who received general anesthesia and 27 patients who received spinal anesthesia completed the questionnaire.7 65% of patients in the general anesthesia group and 33% of patients in the spinal anesthesia group experienced phantom limb pain after surgery – representing a statistically significant difference.7 The incidence of phantom limb sensation was 77% for the general anesthesia group and 74% for the spinal anesthesia group, showing no significant difference.7 The researchers concluded that the incidence of phantom limb pain was lower for patients receiving spinal anesthesia.7
The aforementioned studies investigate the effects of general, spinal, and epidural anesthetic techniques on phantom limb pain. However, these studies do not look at the effects of peripheral nerve block. In a more recent study, Sahin et al retrospectively compared the effects of general anesthesia, spinal anesthesia, epidural anesthesia, and peripheral nerve block on postoperative incidence of phantom limb sensation and phantom limb pain.7 The study included 92 patients for 1 to 24 months after surgery, and a standardized questionnaire assessing phantom limb sensation, phantom limb pain, and stump pain postoperatively on a numerical scale of 0 to 10.7 Sahin et al found that patients who received epidural anesthesia and peripheral nerve block perceived significantly less pain in the week after surgery compared to patients who received general anesthesia and spinal anesthesia.7 However, there was no difference in phantom limb pain, phantom limb sensation, or stump pain among the groups after about 14 to 17 months.7
Overall, the literature suggests that some anesthetic techniques – i.e. peripheral nerve blocks and epidural anesthesia – may attenuate phantom limb pain in the first week after amputation, but not in the long run. As researchers continue to elucidate the neurological and physiological mechanisms of phantom limb pain, clinicians may be able to develop improved techniques to reduce symptoms after surgery.
References:
1) Sahin SH, Colak A, Arar C, et al. A retrospective trial comparing the effects of different anesthetic techniques on phantom pain after lower limb amputation. Curr Ther Res Clin Exp. 2011;72(3):127–137.
2) Flor H: Phantom-limb pain: characteristics, causes, and treatment. Lancet Neurol. 2002;1(3):182–9. 10.1016/S1474-4422(02)00074-1.
3) Hill A. Phantom limb pain: a review of the literature on attributes and potential mechanisms. J Pain Symptom Manage. 1999;17:125–142.
4) Nikolajsen L, Ilkjaer S, Christensen JH, et al. Randomised trial of epidural bupivacaine and morphine in prevention of stump and phantom pain in lower-limb amputation. Lancet. 1997;350:1353–1357.
5) Jahangiri M, Jayatunga AP, Bradley JW, Dark CH. Prevention of phantom pain after major lower limb amputation by epidural infusion of diamorphine, clonidine and bupivacaine. Ann R Coll Surg Engl. 1994;76:324 –326.
6) Ong BY, Arneja A, Ong EW. Effects of anesthesia on pain after lower-limb amputation. J Clin Anesth. 2006;18:6000 – 6004.
7) Ugur F, Esmaoglu A, Akin A, et al. Does spinal anesthesia decrease the incidence of phantom pain? Pain Clinic. 2006;18:187–193.
