A prospective study of Intraoperative Neuromonitoring during Selective Endoscopic Discectomy™ compared with a matched patient sample without neuromonitoring

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Josh Thai


Address:

John Porter M.D.


Address:

Anthony T. Yeung M.D.


Address:

Citation: J. Thai, J. Porter & A. T. Yeung : A prospective study of Intraoperative Neuromonitoring during Selective Endoscopic Discectomy™ compared with a matched patient sample without neuromonitoring . The Internet Journal of Minimally Invasive Spinal Technology. 2008 Supplement I - to IJMIST Vol 1 No 2

Abstract

Introduction: Intraoperative neuromonitoring is commonly utilized in spine surgeries to decrease the risk of nerve injury. There is nothing in the literature, however, defining its role in foraminal endsocopic surgery. We prospectively studied intraoperative neuromonitoring in percutaneous endoscopic surgery to answer the question: Is Intraoperative Neuromonitoring useful in SED™ cases? What information does it yield, if any? Materials and Method: 100 consecutive patients undergoing Lumbar Selective Endoscopic Discectomy™ (SED) were monitored intraoperatively. A control group of similarly matched patients was also evaluated. In the study group, changes in the patient's pre and post operative nerve conduction velocity were measured. The averaged waveforms are marked for latency and amplitude, then saved as a baseline to be compared with subsequent recordings as the surgery progresses. EMG monitoring with audio correlation to the waveforms displayed on the oscilloscope's screen provided a 'live' neuromonitoring modality that provided immediate feedback to the surgeon. Results: Continous EMG monitoring was effective in warning the surgeon about the proximity of the spinal nerve, but it did not correlate with good or adverse clinical results. The incidence of post-op dysesthesia was similar in the two groups. Clinical review of all patients reporting any amount of transient dysesthesia was correlated with patho-anatomy visualized during the procedure. Mild temporary dysesthesia common in patients with an extensive inflammatory membrane undergoing radiofrequency ablation. When large furcal nerves or autonomic nerves were seen in the foramen, the severity of dysesthesia went up with ablation of the inflammatory membrane. Dysesthesia can occur even when no Emg activity and no adverse post-op effects were demonstrated. It was often delayed for several days and even weeks post-op. Neuromonitoring with continuous EMG was helpful by giving the surgeon feedback that instruments were in the vicinity of the spinal nerve. There was no correlation, however, between post-op dysesthesia and recordings of EMG irritability. Conclusion: The causes of dysesthesia remains elusive, and, while it is speculated to be due to nerve trauma, it is not associated with surgical trauma to the nerve in selective endoscopic discectomy™. Patient feedback during surgery utilizing dilute local anesthetic and visualization of the spinal nerve was sufficient to avoid surgical nerve complications.

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