Application value of intraoperative soleus H-reflex monitoring in assessment of endoscopic interlaminar approach under general anesthesia

English Keywords:Interlaminar approach  H-reflex  Percutaneous transforaminal endoscopic discectomy  Intraoperative monitoring

English Abstract:

  【Abstract】 Objectives: To investigate the H-reflex in evaluating the change of the function of S1 nerve root in the different operation steps of endoscopic interlaminar approach for L5/S1 disc herniation under general anesthesia, and to identify the application value of H-reflex in intraoperative monitoring spinal endoscopic surgery under general anesthesia. Methods: Fourteen patients with unilateral L5/S1 disc herniation(S1 nerve root injury) were included in this study(male/female, 7/7; age, 25-53 years old; height 160-177cm), and all patients underwent percutaneous endoscopic interlaminar approach for L5/S1 disc herniation under general anesthesia. Bilateral soleus H-reflexs were recorded at pre-operation, intra-operation(channel placement, nerve root exposure, removal of nucleus pulposus and endoscope system exit) and post-operation. The latency and the baseline-to-negative amplitude of H-reflex were measured. The results were analyzed by SPSS 12.0. 　Results: The H-reflex recorded after anesthesia and placing the intraoperative position was defined as the baseline parameter. The amplitude of H-reflex on the involved side reduced significantly during the nerve root exposure(P<0.05), especially in the separation of adhesive nerve root[falling by an average of (43.9±20.5)%, P<0.05], and then the amplitude recovered, but still was statistically significant difference compared with the baseline value(P<0.05). At the end of surgery, the H-reflexes of all patients were preserved, but still lower than the baseline value which decreased by (15.1±9.0)%(P<0.05). At the second day after surgery, all patients had significantly improved VAS score(preoperative vs. postoperative: 6.4±1.3 vs. 0.6±0.6, P<0.05), and there was no difference of the amplitudes of H-reflex on the involved side in 12 patients between the pre-and post-operation(P>0.05). In this study, two patients had significant reduced H-reflex(more than 85%) during the operation, and the partial recoveries of the H-reflex in these patients were found after stopping the operation for several seconds. All these two patients had no obvious sensory or motor dysfunction after surgery. Conclusions: In this study, the amplitude of soleus H-reflex can reflect the function of S1 nerve root during the different operation steps of endoscopic interlaminar approach under general anesthesia effectively. Therefore, the clinical application of H-reflex monitoring technology can provide additional and reliable methods to protect the nerve root during the spinal endoscopy surgery under general anesthesia.