Return of motor evoked potentials after knee flexion in the setting of high-grade spondylolisthesis.

PURPOSE: To present a case of loss of motor-evoked potentials (MEPs) to the left foot in the supine position after a partial reduction and instrumented fusion from L4 to pelvis which was managed successfully without revision or removal of implants.

METHODS

We report a patient with high-grade spondylolisthesis who demonstrated loss of motor-evoked potentials after posterior spinal fusion and transfer to supine position. The patient's knees were flexed to 90° and signals were immediately restored. Systemic steroids were administered and circumferential fusion was delayed 21 days. Anterior-interbody cage was placed without complication.

RESULTS

She was discharged on post-operative day 2. At 7 months, she is pain free and doing well with plans to return to gymnastics completely.

CONCLUSIONS

Knee flexion can be instituted when encountering a neuromonitoring signal change following posterior spinal fusion for spondylolisthesis as a means to alleviate acute nerve stretch injury and may in some cases prevent the need to lessen the correction.

LEVEL OF EVIDENCE: IV.