Labor Epidural Intolerance Due to a Congenitally Narrowed Spinal Canal.

Reports exist of severe upper back pain of unknown etiology after administration of large volumes into the epidural space. We present a case of an otherwise healthy parturient who developed severe upper back and neck pain after receiving only a small volume of epidural medication. Magnetic resonance imaging revealed a congenitally narrowed spinal canal because of short pedicle syndrome. Epidural injectate occupies and compresses a percentage of the spinal canal and its neuronal contents. This may result in pain and epidural intolerance when continued injectate reaches a critical point, a threshold that is lower with shortened pedicles or congenital spinal stenosis. We believe a similar mechanism may explain the pain that patients sometimes experience after administration of large epidural volumes.