Subdural injection of a local anesthetic with steroids: complication of epidural anesthesia.

We describe the unintentional injection of a small amount of local anesthetic with steroids into the subdural space during an attempted lumbar epidural injection for low back pain. When small volumes of local anesthetic are injected into the subdural space, a patchy and unilateral block of greater magnitude than expected will result. When larger volumes of local anesthetic are injected, a massive motor and sensory block can occur due to the small confines of this space. Accidental subdural injection must be recognized early and treated appropriately to avoid serious complications, especially in an outpatient setting.