Inspired by King et al 2021.[1]
EA – electroacupuncture
key to acronyms
PLP – phantom limb pain
fMRI – functional magnetic resonance imaging
I have always had a fascination for referred pain, and I guess PLP is the ultimate in referred pain as the condition results in pain being experienced in a part of the body that no longer exists.
PLP – the ultimate referred pain
My first experience with the subject was rather academic – I had the opportunity to stand in for Jacky Filshie at the 1st international conference on PLP, which was held in Oxford a little over 20 years ago. I joined a pre-conference consensus meeting with a host of famous professors from all around the world including Ron Melzack and Pat Wall, who are immortalised by the first elucidation of the gate theory of pain.[2] I mentioned this briefly is a previous blog, which has a reference to some contemporary updates to this theory.[3]
At the time Ron Melzack proposed something he called the body self–neuromatrix to explain phantom limb phenomena as well as other aspects of the pain experience.[4]
body self–neuromatrix
The paper that inspired this blog is a case report describing a local plus dorsal segmental EA approach to a patient with quite severe PLP. The patient, who was in his 30’s, suffered significant trauma to his left side when he was hit by a car. This resulted in a high transfemoral amputation, and he subsequently experienced PLP as a stabbing pain, fizzing and dull ache in his phantom foot and cramping and aching in his phantom limb and toes. He rated the severity of PLP on average as 7/10 and at worst as 9/10. His sleep was affected by the PLP, and he slept for no more than 2 hours at a time.
He was taking gabapentin at a dose of 900mg 3 times a day and zopiclone 3.75mg at night, but this gave very little relief and considerable side effects including loss of concentration, reduced alertness, and increased fatigue.
A Cochrane review on PLP in 2016 found conflicting evidence for a pain relieving effect of gabapentin, and no effect on function, depression scope or sleep quality.[5] The review on gabapentin for chronic neuropathic pain in adults found that some patients achieved good pain relief in post herpetic neuralgia and diabetic neuropathy with doses between 1800mg and 3600mg per day.[6] There was limited evidence in other forms of neuropathic pain.
The lead author of the highlighted case report is a specialist amputee physiotherapist, and she found extensive scarring in the patient’s residual limb but no sign of neural tethering or neuroma formation. She suggested trying EA to the patient who was very sceptical at first.
Sessions were performed weekly for the first 6 weeks and then fortnightly for a further 6 weeks. Within 2 sessions there was a reduction in pain and improvement in sleep, but the frequency and duration of pain did not reduce until 6 to 8 sessions.
By 12 months the PLP had reduced to no more than 1 hour on 1 night in the week, and sleep was normal the rest of the time. The dose of gabapentin was gradually reduced over the first 6 weeks, and by 12 months the patient was off all drugs.
This was a very good result in a neuropathic pain condition, and I cannot help wondering whether the main effect was central or peripheral in this case. Both approaches were used, and of course the peripheral pair of needles would potentially mediate both local and central (segmental and general) effects. I have used a very similar peripheral approach in a case of chronic lower limb PLP, which was clearly neuroma related. I could reproduce phantom sensation on needling close to the sciatic neuroma, but the effect was short-lived. Interestingly, whilst there was no long-term effect on background PLP, EA did settle down an iatrogenic exacerbation of PLP following injection of dextrose in a clinical trial. My interpretation was that the EA mainly affected the central integration of pain (‘wind up’ or amplification) rather than altering the presumed peripheral ectopic neural activity in the neuroma where the sciatic nerve had been transected.
We have published several papers on PLP in Acupuncture in Medicine over the last decade or so. These include case reports of success with manual acupuncture,[7] scalp acupuncture,[8] and mirror point acupuncture.[9] There is even a case where the fMRI signature of needling a prosthetic limb was studied.[10]
There was also a feasibility trial on a Delphi consensus derived manual acupuncture protocol that estimated the need for 85 patients per group in any subsequent trial.[11–13] That would take a while to recruit in the absence of an active war zone with ubiquitous mine fields.
Ramachandran’s mirror box
Going back to the international consensus meeting in Oxford some 20 years ago, I remember being intrigued when listening to Ramachandran describe the use of his mirror box in PLP.[14] I subsequently heard him on BBC Radio 4 talking about mirror therapy, synaesthesia and how rare cases can inform our understanding of the brain. Just today I spotted a systematic review of mirror therapy in PLP including 11 trials and 491 patients with amputations.[15] The review found a large effect for mirror therapy over controls.
In summary, I would be in favour of going for local plus regional and contralateral segmental EA to catch all possible therapeutic advantage, and consider doing the whole thing with a vertical mirror so the patient can see his or her phantom being treated.
References
1 King H, Forrester M. Electroacupuncture For Alleviation Of Phantom Limb Pain. J Rehabil Med Clin Commun 2021;4:1000063. doi:10.2340/20030711-1000063
2 Melzack R, Wall PD. Pain Mechanisms: A New Theory. Science 1965;150:971–8. doi:10.1126/science.150.3699.971
3 Zhang Y, Liu S, Zhang YQ, et al. Timing Mechanisms Underlying Gate Control by Feedforward Inhibition. Neuron 2018;99:941-955.e4. doi:10.1016/j.neuron.2018.07.026
4 Melzack R. From the gate to the neuromatrix. Pain 1999;Suppl 6:S121–6. doi:10.1016/S0304-3959(99)00145-1
5 Alviar MJM, Hale T, Dungca M. Pharmacologic interventions for treating phantom limb pain. Cochrane Database Syst Rev 2016;10:CD006380. doi:10.1002/14651858.CD006380.pub3
6 Wiffen PJ, Derry S, Bell RF, et al. Gabapentin for chronic neuropathic pain in adults. Cochrane Database Syst Rev 2017;6:CD007938. doi:10.1002/14651858.CD007938.pub4
7 Bradbrook D. Acupuncture treatment of phantom limb pain and phantom limb sensation in amputees. Acupunct Med 2004;22:93–7. doi:10.1136/aim.22.2.93
8 Tseng C-C, Chen P-Y, Lee Y-C. Successful treatment of phantom limb pain and phantom limb sensation in the traumatic amputee using scalp acupuncture. Acupunct Med 2014;32:356–8. doi:10.1136/acupmed-2014-010556
9 Davies A. Acupuncture treatment of phantom limb pain and phantom limb sensation in a primary care setting. Acupunct Med 2013;31:101–4. doi:10.1136/acupmed-2012-010270
10 Lee I-S, Jung W-M, Lee Y-S, et al. Brain responses to acupuncture stimulation in the prosthetic hand of an amputee patient. Acupunct Med 2015;33:420–4. doi:10.1136/acupmed-2015-010785
11 Trevelyan EG, Turner WA, Robinson N. Developing an acupuncture protocol for treating phantom limb pain: a Delphi consensus study. Acupunct Med 2015;33:42–50. doi:10.1136/acupmed-2014-010668
12 Trevelyan EG, Turner WA, Robinson N. Acupuncture for the treatment of phantom limb pain in lower limb amputees: study protocol for a randomized controlled feasibility trial. Trials 2015;16:158. doi:10.1186/s13063-015-0668-3
13 Trevelyan EG, Turner WA, Summerfield-Mann L, et al. Acupuncture for the treatment of phantom limb syndrome in lower limb amputees: a randomised controlled feasibility study. Trials 2016;17:519. doi:10.1186/s13063-016-1639-z
14 Ramachandran VS, Rogers-Ramachandran D. Synaesthesia in phantom limbs induced with mirrors. Proc Biol Sci 1996;263:377–86. doi:10.1098/rspb.1996.0058
15 Wang F, Zhang R, Zhang J, et al. Effects of mirror therapy on phantom limb sensation and phantom limb pain in amputees: A systematic review and meta-analysis of randomized controlled trials. Clin Rehabil Published Online First: 24 July 2021. doi:10.1177/02692155211027332
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