Treating intractable phantom limb pain with ambulatory continuous peripheral nerve blocks: a pilot study

Abstract

Background: There is currently no reliable treatment for phantom limb pain (PLP). Chronic PLP and associated cortical abnormalities may be maintained from abnormal peripheral input, raising the possibility that a continuous peripheral nerve block (CPNB) of extended duration may permanently reorganize cortical pain mapping, thus providing lasting relief.

Methods: Three men with below-the-knee (2) or -elbow (1) amputations and intractable PLP received femoral/sciatic or infraclavicular perineural catheter(s), respectively. Subjects were randomized in a double-masked fashion to receive perineural ropivacaine (0.5%) or normal saline for over 6 days as outpatients using portable electronic infusion pumps. Four months later, subjects returned for repeated perineural catheter insertion and received an ambulatory infusion with the alternate solution ("crossover"). Subjects were followed for up to 1 year.

Results: By chance, all three subjects received saline during their initial infusion and reported little change in their PLP. One subject did not receive crossover treatment, but the remaining two subjects reported complete resolution of their PLP during and immediately following treatment with ropivacaine. One subject experienced no PLP recurrence through the 52-week follow-up period and the other reported mild PLP occurring once each week of just a small fraction of his original pain (pretreatment: continuous PLP rated 10/10; posttreatment: no PLP at baseline with average of one PLP episode each week rated 2/10) for 12 weeks (lost to follow-up thereafter).

Conclusions: A prolonged ambulatory CPNB may be a reliable treatment for intractable PLP. The results of this pilot study suggest that a large, randomized clinical trial is warranted.

Figure 1

Effects of ambulatory perineural normal saline (placebo) and ropivacaine (“active”) infusions on phantom limb pain severity and incidence (within the previous week, or since the previous time point, whichever was less). Pain severity indicated using a Numeric Rating Scale of 0–10, with 0 equivalent to no pain and 10 equivalent to the worst imaginable pain. Data are expressed as means. “X-over”: crossover treatment with ropivacaine.