頚椎症性脊髄症による難治性疼痛に対するケタミンの使用経験―ケタミンの有効性と課題について

Ketamine Treatment for Severe Neuropathic Pain with Cervical Spondylotic Myelopathy. A Case Report

Ⅰ．はじめに

　難治性疼痛の発生機序の1つとして，シナプスにおけるNMDA受容体（N-methyl-D-aspartate receptor）の発現が関与していると報告されている．ケタミンはNMDA受容体のイオンチャネルを遮断することにより除痛効果を呈する^9,17)．今回われわれは頚椎症性脊髄症治療後に残存した難治性疼痛に対しケタミンが有効であった1例を経験したので，文献的考察を加えて報告する．

　This 60-year-old man with cervical spondylosis experienced bilateral arm pain and weakness. After anterior cervical fusion and posterior decompression at a local hospital his symptoms worsened and he was admitted to our hospital. On admission he manifested bilateral motor weakness,neuropathic pain,and numbness below the C5 level. Radiological findings showed spinal cord compression at the C4 to C7 level. He again underwent posterior decompression and anterior fusion. Although his paresis was improved,his severe neuropathic pain and numbness persisted. Because treatment with NSAIDs,clonazepam,and gabapentin failed to control his symptoms we administered ketamine (NMDA receptor antagonist) because his symptoms were alleviated upon ketamine test challenge. His severe symptoms improved and there were no complications. However,upon cessation of ketamine treatment they reappeared. Therefore,we continued daily ketamine treatment for 6 months,after which we changed to codeine phosphate. His symptoms were controlled without any complications. Ketamine is useful for the control of severe neuropathic pain,however,as long-term ketamine administration is inadvisable,we suggest that treatment be tailored to each patient's particular clinical status.