The difference of intraoperative free-run electromyography monitoring between percutaneous endoscopic lumbar discectomy via a transforaminal and via an interlaminal

Aim: Transforaminal percutaneous endoscopic lumbar discectomy (TF-PELD) is usually performed under local anesthesia because the patient should be conscious to prevent nerve root injury. However, some patients cannot tolerate intraoperative pain and require intravenous analgesia, or must be converted to surgery under general anesthesia (GA). If PELD under GA can be performed safely, it is more convenient and comfortable for both the patient and surgeon.Methods: A total of 49 cases (mean age, 53 years) were examined. PELD was performed under GA with free-run electromyography (f-EMG) monitoring. Clinical outcomes were assessed according to the visual analogue scale score (VAS) and the Oswestry disability index (ODI). All patients were monitored with f-EMG.Results: VAS decreased from 7.7 to 1.1 and ODI from 62.3% to 20.5%. A true-positive was observed in one of 27 TF-PELD cases. Care during the procedure is necessary to avoid the risk of severe neurological injury. A false-negative was observed in one of 22 interlaminar (IL)-PELD cases. This patient complained of aggravated numbness for 6 months after surgery. False-positives were recorded in 2 cases of IL-PELD with a train wave just after removal of the herniated discs.Conclusion: F-EMG monitoring during PELD under GA was useful to identify nerve root damage. TF-PELD under GA requires f-EMG to ensure safety. On the contrary, IL-PELD does not necessitate f-EMG