Transient Spinal Segmental Myoclonus during Neuraxial Anesthesia: A Report of Two Cases

We report here two cases of transient spinal segmental myoclonus occurred during neuraxial anesthesia. One case was an 82-year-old woman, who was scheduled to undergo surgery for abdominal aortic aneurism, was indwelled epidural catheter the day before surgery. A quick, involuntary muscle jerk of the lower limbs began 30 minutes after giving a test dose bolus injection of mepivacaine via the epidural catheter. Despite removal of the epidural catheter, the involuntary muscle jerk persisted and ceased spontaneously five hours after injection of mepivacaine. The other case was a 33-year-old woman who underwent an emergency Caesarean section under a combined spinalepidural anesthesia. Involuntary muscle jerk of the upper limbs began 76 minutes after the intrathecal administration of hyperbaric bupivacaine during immediate post-operative period. The involuntary muscle contraction ceased four hours after injection of bupivacaine without any treatment. In both cases, no abnormal findings were detected in the spinal cord in MRI and/or CT. The involuntary muscle jerk observed in those two patients was diagnosed spinal segmental myoclonus by neurologists. The unusual effect of local anesthetics to the spinal cord neurons during neuraxial anesthesia was suspected as the cause of myoclonus. Although the spinal myoclonus caused by neuraxial anesthesia is quite rare and its etiology is unclear, anesthesiologists should be aware of this bizarre and stressful complication.本稿の要旨は日本麻酔科学会 中国・四国支部第50回学術集会（高松市，2013年）で発表した