1例63岁男性患者行开颅血肿清除术后因颅内感染给予头孢哌酮钠舒巴坦钠3 g、1次/8 h联合多黏菌素B 50万U、1次/12 h静脉滴注，5 d后加用多黏菌素B 5万U、1次/d鞘内注射。用药前患者左、右下肢肌力分别为3、4级。第4次鞘内注射硫酸多黏菌素B后约20 min，患者出现双下肢无力，约9 h后双下肢肌力均降至1级。考虑患者的下肢肌无力可能与鞘内注射多黏菌素B有关，停用鞘内注射及静脉滴注用多黏菌素B，改为头孢哌酮钠舒巴坦钠2 g、1次/6 h联合万古霉素1 g、1次/12 h静脉滴注。5 d后，患者左、右下肢肌力分别恢复至3级和4级。“,”A 63-year-old male patient received IV infusions of cefoperazone sodium and sulbactam sodium 3 g once per 8 hours and polymyxin B 500 000 units once per 12 hours for intracranial infection after removal of hematoma by craniotomy. Five days later, intrathecal injection of polymyxin B 50 000 units once daily was added. Before treatments, the patient′s muscle strength of left and right lower limbs were grade 3 and 4, respectively. About 20 minutes after the 4th intrathecal injection of polymyxin B, the patient developed weakness of both lower limbs. About 9 hours later, his muscle strength of both lower limbs decreased to grade 1. Myasthenia of lower limbs was considered to be related to intrathecal injection of polymyxin B. Intrathecal injection and IV infusion of polymyxin B were both stopped and replaced by IV infusions of sulbactam sodium 2 g once per 6 hours and vancomycin 1 g once per 12 hours. Five days later, the patient′s muscle strength of left and right lower limbs recovered to grade 3 and grade 4, respectively.