Is It Real False Negative Finding in Motor Evoked Potential Monitoring during Corrective Surgery of Ankylosing Spondylitis? A Case Report.

We performed L1 posterior vertebral columnar resection and posterior correction for Andersson's lesion and thoracolumbar kyphosis in an ankylosing spondylitis patient during motor evoked potential (MEP) monitoring. We checked MEP intra-operatively, whenever a dangerous procedure for neural elements was performed, and no abnormal findings were seen during surgery. After the operation, we examined neurologic function in the recovery room; the patient showed a progressive neurologic deficit and no response to MEP.