[Ketamine infusion therapy for refractory neuralgia in spinal disease: report of two cases]

We report two cases of refractory pain in a spinal disease. One case was a 60-year-old male who presented intractable pain in bilateral upper extremities after anterior fusion (C5/6, 6/7) for cervical spondylosis. The other was a 63-year-old female who also had intractable pain in the left anterio-lateral chest wall with no remarkable past history. Both cases were refractory to nonsteroidal anti-inflammatory drugs (NSAIDs) or minor tranquilizer or local anesthesia with bupivacaine. However, their pain was significantly relieved by the intravenous administration of a test dose (5mg) of ketamine which is a noncompetitive blocker of N-methyl-D-aspartate (NMDA) receptors. As for case 1, the effect of the injection of the test dose lasted, so continuing infusion therapy of ketamine was cancelled. In case 2, recurrence of the pain was recognized gradually. She underwent continuing infusion therapy of 2mg/kg of ketamine, and it brought about continued pain relief. We conclude that ketamine infusion therapy should also be considered for therapy of refractory neuralgia in spinal disease.