False Negative and Positive Motor Evoked Potentials in One Patient: Is Single Motor Evoked Potential Monitoring Reliable Method?

Abstract

A case report and literature review. To report a false negative and delayed positive motor-evoked potential (MEP) in 1 patient. An unreliable MEP can result in fatal outcomes because surgeons have recently begun to depend on the MEP for intraoperative decision-making. We report a case of a false MEP during scoliosis surgery that showed false negative and positive MEPs during a series of operations. A 23-year-old man with a history of spondyloepiphyseal dysplasia presented with severe kyphoscoliosis. The initial neurologic examination did not reveal any neurologic abnormalities. Surgical correction and fusion were performed with transcranial MEP monitoring. During the entire procedure, the MEP did not reveal any signs of cord injury. However, lower limb paralysis and paresthesia was observed when the patient awakened. After 2 additional surgical procedures to recover the neurologic deficit, the MEP did not show any signs of cord injury but the patient's neurologic status had recovered slightly. At postoperative day 8, the neurologic status recovered, and a third operation was performed to fix the long rods. However, there were abnormal amplitudes in both lower limbs but the patient's neurologic status was almost normal. From our experience of false negative and positive MEP in 1 patient, it is concluded that undesirable events can occur with use of MEP in scoliosis or other spinal surgery. Therefore, we warn the surgeons too heavily rely on the MEP monitoring, and propose a further prospective study as well as use of alternative method that can improve the reliability of single MEP.