We present the cases of two patients who suffered severe lower extremity injuries and subsequently developed phantom limb pain (PLP) that was refractory to high dose opioids and adjunctive pain medications. Both patients were receiving large doses of oral methadone, IV hydromorphone via a patient-controlled analgesia delivery system, and adjunctive medications including tricyclic antidepressants, nonsteroidal anti-inflammatory medications, and anti-epileptics. Despite these treatments, the patients had severe PLP. Upon induction of the oral N-methyl-D-aspartate receptor antagonist memantine, both patients had a profound reduction in their PLP without any apparent side effects from the medication.

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. Four months later, subjects returned for repeated perineural catheter insertion (“crossover”), and received an ambulatory infusion with the alternate solution. Subjects were followed for up to one year. Results By chance, all 3 subjects received saline during their initial infusion and reported little change in their PLP. One subject did not receive crossover treatment; but, the remaining 2 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 (pre-treatment: continuous PLP rated 10/10; post-treatment: no PLP at baseline with average of 1 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.

Questions from patients concerning a disease process known as erythromelalgia, its diagnosis, symptoms, and treatments are answered to help patients and caregivers understand the disease and its treatment. The responses from the author are intended to educate patients about their disease and make them more effective self-advocates.

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