In the following case report, a posterior lower lumbar surgical procedure done on a Spondylolisthesis (L5/S1) patient resulted in a transient loss of motor evoked potentials despite the patient had no neurological injury?. The motor loss was occurred after epidural injection of 2.4mg of morphine?. The authors believe it could be due to the pressure caused by the injection would have compressed cauda equina?.
Even a small injection of this kind could lead to evoked potential changes should be noted. Though the TcMEP recovered after 1h, care must be taken to make sure prolonged compression does not take place!.
A 7-year-old girl having posterior spinal fusion for Grade 3 anterior spondylolisthesis at the L5/S1 level was administered 2.5 mg of morphine in 10 ml saline via the caudal epidural route before surgery.Motor-evoked responses were markedly diminished in her lower limbs for 1 h following this but returned spontaneously. She suffered no neurological injury. The cause for this is postulated to be transient cauda equina compression from the volume of injectate. This complication of caudal injection has not been reported before. The possible mechanisms for this are discussed. We believe that significant L5/S1 spondylolisthesis should be considered a contraindication to the use of caudal epidural injections.
