Intraoperative Loss of Tibialis Anterior Transcranial Electrical Motor Evoked Potentials Predicted Postoperative Footdrop.

BACKGROUND: Footdrop secondary to L5 root injury is a rare complication associated with lumbar surgery. It is unclear whether intraoperative neuromonitoring can detect such an injury.

CASE DESCRIPTION: A 54-year-old man who had had bilateral chronic L5 radiculopathy underwent L4-S1 lumbosacral decompression and fusion. During surgery, the patient lost transcranial electrical motor evoked potentials (tceMEPs) from the left tibialis anterior (TA) at the time of L5-S1 intervertebral cage placement. Neither intraoperative free-run electromyography nor somatosensory evoked potentials detected any changes. In addition, contralateral TA tceMEPs remained stable. Postoperatively, the patient presented with left-sided footdrop that has persisted for >1 year.

CONCLUSIONS: Intraoperative TA tceMEPs could detect L5 root iatrogenic injury.