A case-report of a 53-year-old man with severe low back pain with subdural dislocation (between the dura and arachnoidea spinalis) of an epidural catheter has been presented. The injection of 10 ml of 0.25% bupivacaine wih 2.5 mg of morphine every 8 hours via epidural catheter provided excellent low back pain relief. After five and half months the same injection caused unexpected progressive loss of strength and sensation in both lower extremities, distal part of the trunk, paraesthesia in the upper right extremity and mild dyspnea within several minutes after the injection. X-ray control after injecting 3 ml of ioversol revealed the ventral subdural malposition of a catheter with spreading the radiopaque contrast medium up to Th3 level. The diagnosis of subdural block must be considered in patients with unusual presentation even after long-lasting successful epidural pain management. A radiopaque contrast medium radiograph may adequately demonstrate subdural placement in some cases, although computed tomography or magnetic resonance image should be performed if any doubt arises.

        Key words: subdural block, epidural catheter, low back pain, chronic pain.