Radiographic findings of unilateral epidural block.

In 236 consecutive lumbar epidural anesthesia patients, epidurography was performed in seven patients who developed unilateral loss of cold sensation to clarify the cause of unilateral block. Epidurography demonstrated the epidural catheter tip location in the anterior epidural space in four patients (57%) and in the transforaminal passage in three patients (43%). In all seven patients, successful bilateral epidural anesthesia was obtained by a second puncture using another catheter. Our results showed that the most frequent cause of unilateral epidural blockade was the misplacement of the catheter into the anterior epidural space.