The NMDA-receptor antagonist ketamine abolishes neuropathic pain after epidural administration in a clinical case

A 14-year-old male patient developed severe right limb pain after traumatic sciatic nerve injury. His pain was diagnosed as neuropathic pain (complex regional pain syndrome, type II). He did not respond to any conventional therapy for limb pain including non-steroidal anti-inflammatory drugs, antidepressants, anticonvulsants, continuous epidural administration of local anesthetics and psychotherapy. Following continuous epidural administration of a very low dose of ketamine, an N-methyl- d-aspartic acid (NMDA) receptor antagonist, 25 μg/kg per h for 10 days, complete pain relief was obtained without any side-effects. There has been no recurrence of pain for 8 months after discontinuation of epidural ketamine. The symptoms related to dysfunction of the sympathetic nervous system still remained after complete pain relief. We discuss pain mechanisms, pain relief and the use of ketamine in this case.