Date Presented 04/04/19
Mirror therapy has demonstrated positive results for decreasing phantom limb pain in individuals with amputations. Transcranial direct current stimulation (tDCS), a form of noninvasive brain stimulation, is a cost-effective means of altering cortical excitability and may enhance the effects of mirror therapy. Results from a case study with a lower-extremity amputation revealed no adverse effects with decreases in phantom limb pain. Future studies are warranted.
Primary Author and Speaker: Anna Boone
Contributing Authors: Scott Frey
BACKGROUND: Phantom limb pain (PLP) occurs in up to 80% of the millions of individuals worldwide who have sustained a limb amputation (Ziegler-Graham, MacKenzie, Ephraim, Travison, & Brookmeyer, 2008). Effects of PLP can be devastating to an individual’s occupations, relationships, and quality of life (Trevelyan, Turner, & Robinson, 2016). Mirror therapy has demonstrated positive effects on pain outcomes in clients with amputations. Mirror therapy is conducted by placing a mirror in midline and the intact limb creates an illusory limb in place of the amputated limb. Transcranial direct current stimulation (tDCS) alters cortical excitability and may enhance the effects of mirror therapy. The purpose of the study was to evaluate the combined effect of tDCS and mirror therapy in an individual six years post lower extremity amputation.
DESIGN: An exploratory case study design was used with outcome data gathered pre-intervention, post-intervention, and at 1-week follow-up. An individual was recruited through physician referral meeting the following inclusion criteria: unilateral amputation, minimum of 3 pain episodes/week, current rating of at least 20 mm on a 100-mm visual analog scale (VAS), age 18-75, and pain interference with daily life activities. Exclusion criteria included contraindications for tDCS.
METHOD: The participant completed 10, 45-minute intervention sessions on consecutive weekdays. Each session began with 20 minutes of 1.5 mA anodal tDCS with the anode over the primary motor cortex contralateral to the amputation and the cathode over the ipsilateral supraorbital region. Following tDCS, the participant completed 15 minutes of mirror therapy. Outcome data were gathered via a 100-mm VAS for PLP and residual limb pain at the beginning and end of each intervention session and at 1-week follow-up. The 100-mm VAS was also used to gather reports of the daily average of pain. The impact of pain on everyday life was assessed via the PROMIS Pain Interference questionnaire at pre-intervention, mid-intervention, post-intervention, and at 1-week follow-up. The tDCS Sensation Questionnaire was used to monitor sensations and adverse effects of tDCS.
RESULTS: The participant completed 100% of intervention sessions and experienced decreases in average daily PLP per the 100-mm VAS with a change score of 23-mm at mid-intervention, a change score of 33 mm at post-intervention, and a change score of 49 mm at one week follow-up. Daily average ratings of residual limb pain were highly variable; however, current ratings of residual limb pain consistently decreased from pre-session ratings to post-session ratings. There was no effect on the impact of pain on everyday life per the PROMIS Pain Interference measure with a change score of zero from pre-intervention to post-intervention. At one week follow-up there was a change score of 2 in the PROMIS Pain Interference raw score for PLP. The participant experienced no adverse effects as evidenced by a score of zero on the tDCS questionnaire.
CONCLUSION: Results suggest that the intervention format is well-tolerated by the participant. While limited in external validity, current change scores indicate that mirror therapy used in conjunction with tDCS may lead to positive effects for decreasing PLP in lower extremity amputees. Further studies should replicate these findings within a larger sample and explore the dosage effect of mirror therapy and tDCS. Additionally, future study designs should include an inactive (sham) tDCS and mirror therapy group compared to an active tDCS and mirror therapy group to better isolate the respective contributions of tDCS and mirror therapy.
References
Ziegler-Graham, K., MacKenzie, E. J., Ephraim, P. L., Travison, T. G., & Brookmeyer, R. (2008). Estimating the prevalence of limb loss in the United States: 2005 to 2050. Archives of Physical Medicine and Rehabilitation, 89(3), 422-429.
Trevelyan, E. G., Turner, W. A., & Robinson, N. (2016). Perceptions of phantom limb pain in lower limb amputees and its effect on quality of life: A qualitative study. British Journal of Pain, 10(2), 70-77.
