Hannah Reckmeyer

Background:  Phantom limb pain (PLP) is a condition that has been recognized for centuries, yet its pathophysiology has remained poorly understood. Fortunately, research in recent decades has shed light on this debilitating condition and its treatment methods, including transcranial direct current stimulation (tDCS). PLP is defined as the perception of painful sensations in the missing portion of a limb following limb loss, and it affects 80-90% of amputees in the US, totaling over 2 million individuals.¹ The leading theory regarding the cause of PLP is the cortical remapping theory (CRT), which suggests the somatosensory areas of the cortex associated with the amputated limb become infringed upon by neighboring regions, leading to the perception of PLP. ^{2, 3}

Research objectives: This investigation hypothesized tDCS is an effective treatment in reducing PLP.

Methods:  To evaluate the effectiveness of tDCS in treating PLP, a review was conducted using the MeSH database and PubMed search engine. Key terms included “tDCS treatment phantom limb pain,” “phantom limb pain treatment,” “PLP neuromodulation treatment,” and “tDCS treatment amputee symptoms”. The review was limited to clinical trials and reviews conducted within the past 5 years.

Results:  The results of the review suggest that tDCS can affect cortical plasticity and remapping by modulating the excitability of neurons in the brain.^{4, 5, 6} Participants in the studies tended to report a reduction in phantom limb sensation, including pain, although the duration of relief varied across studies, with most only evaluating relief from PLP within a 4-week timeline.^{4, 5} Factors such as location, duration, intensity, frequency, and other variables may contribute to the effects of tDCS as well. The review also highlighted several areas that require further exploration. For instance, future studies could benefit from standardizing the duration of short and long-term treatments, as PLP can often persist for years or decades. Investigating the effects of tDCS beyond a 4-week study could provide valuable insights. Furthermore, studies suggest that tDCS may have beneficial effects on other conditions in patients with PLP, such as depression, cognitive changes, and other phantom sensations.^{5, 6} Investigating the potential uses of tDCS for addressing amputation-related symptoms, beyond just PLP, appears to be a valuable pursuit. Lastly, some studies explored the use of tDCS in combination with other treatments, such as mirror therapy. Results suggested a decrease in phantom symptoms and supported continued research in this field.

Conclusions:  Overall, while much of the evidence provided supports the claims that tDCS reduces PLP, the scope, effective duration, and the amplification of impact when combined with other treatments of tDCS are yet to be fully explored. Therefore, future research should focus on these innovative directions to enhance our understanding and treatment of PLP.

Works Cited:

1. Stankevicius A, Wallwork SB, Summers SJ, Hordacre B, Stanton TR. Prevalence and incidence of phantom limb pain, phantom limb sensations and telescoping in amputees: A systematic rapid review. Eur J Pain. 2021;25(1):23-38. doi:10.1002/ejp.1657
2. Urits I, Seifert D, Seats A, et al. Treatment Strategies and Effective Management of Phantom Limb-Associated Pain. Curr Pain Headache Rep. 2019;23(9):64. Published 2019 Jul 29. doi:10.1007/s11916-019-0802-0
3. Kaur A, Guan Y. Phantom limb pain: A literature review. Chin J Traumatol. 2018;21(6):366-368. doi:10.1016/j.cjtee.2018.04.006
4. Kikkert S, Mezue M, O’Shea J, et al. Neural basis of induced phantom limb pain relief. Ann Neurol. 2019;85(1):59-73. doi:10.1002/ana.25371
5. Bocci T, De Carolis G, Ferrucci R, et al. Cerebellar Transcranial Direct Current Stimulation (ctDCS) Ameliorates Phantom Limb Pain and Non-painful Phantom Limb Sensations. Cerebellum. 2019;18(3):527-535. doi:10.1007/s12311-019-01020-w
6. Miuli A, Spano MC, Lorusso M, et al. Transcranial direct current stimulation for Phantom Limb Pain circuitopathy: Efficacy and safety in a patient with a cardiac defibrillator. Clin Neurophysiol. 2020;131(1):345-346. doi:10.1016/j.clinph.2019.09.018
7. Culp CJ, Abdi S. Current Understanding of Phantom Pain and its Treatment. Pain Physician. 2022;25(7):E941-E957.
8. Hanyu-Deutmeyer AA, Cascella M, Varacallo M. Phantom Limb Pain. In: StatPearls. Treasure Island (FL): StatPearls Publishing; September 4, 2022.
9. Collins KL, Russell HG, Schumacher PJ, et al. A review of current theories and treatments for phantom limb pain. J Clin Invest. 2018;128(6):2168-2176. doi:10.1172/JCI94003
10. Segal N, Pud D, Amir H, et al. Additive Analgesic Effect of Transcranial Direct Current Stimulation Together with Mirror Therapy for the Treatment of Phantom Pain. Pain Med. 2021;22(2):255-265. doi:10.1093/pm/pnaa388
11. Gunduz ME, Pacheco-Barrios K, Bonin Pinto C, et al. Effects of Combined and Alone Transcranial Motor Cortex Stimulation and Mirror Therapy in Phantom Limb Pain: A Randomized Factorial Trial. Neurorehabil Neural Repair. 2021;35(8):704-716. doi:10.1177/15459683211017509
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