Utility of somatosensory- and motor-evoked potential change thresholds in surgical treatment for thoracic spinal stenosis based on different pathologies.

BACKGROUND CONTEXT: Thoracic spinal stenosis (TSS) is secondary to different pathologies that differ in clinical characteristics and surgical outcomes. PURPOSE: This study aimed to determine the optimal warning thresholds for combined somatosensory-evoked potentials (SSEP) and motor-evoked potentials (MEP) for predicting postoperative neurological deterioration in surgical treatment for TSS based on different pathologies. Additionally, we explored the correlation between SSEP/MEP monitoring and postoperative spinal neurological function. STUDY SETTING: Retrospective study. PATIENT SAMPLE: Two hundred and five patients. OUTCOME MEASURES: We obtained perioperative modified Japanese Orthopedic Association (mJOA) scores to assess spinal neurological function. METHODS: The data collected in this study included demographic data, intraoperative neurophysiological monitoring (IONM) signals, and perioperative neurological function assessments. To determine the optimal IONM warning threshold, a receiver operating characteristic (ROC) curve was used. Additionally, Pearson correlation analysis was conducted to determine the correlation between IONM signals and clinical neurological conditions. RESULTS: A total of 205 consecutive patients were eligible. Forty-one patients had thoracic disc herniation (TDH), 14 had ossification of the posterior longitudinal ligament (OPLL), 124 had ossification of the ligamentum flavum (OLF), and 26 had OPLL+OLF. The mean mJOA scores before surgery and 3 months after surgery were 7.0 and 7.9, respectively, resulting in a mean mJOA recovery rate (RR) of 23.1%. The average postoperative mJOA RRs for patients with TDH, OPLL, OLF, and OPLL+OLF were 24.8%, 10.4%, 26.8%, and 11.2%, respectively. Patients with OPLL+OLF exhibited a more stringent threshold for IONM changes. This included a lower amplitude cutoff value (a decrease of 49.0% in the SSEP amplitude and 57.5% in the MEP amplitude for short-term prediction) and a shorter duration of waveform change (19.5 minutes for SSEP and 22.5 minutes for MEP for short-term prediction). On the other hand, patients with TDH had more lenient IONM warning criteria (a decrease of 49.0% in SSEP amplitude and 77.5% in MEP amplitude for short-term prediction; durations of change of 25.5 minutes for SSEP and 32.5 minutes for MEP). However, OPLL patients or OLF patients had moderate and similar IONM warning thresholds. Additionally, there was a stronger correlation between the SSEP amplitude variability ratio and the JOA RR in OPLL+OLF patients, while the correlation was stronger between the MEP amplitude variability ratio and the JOA RR for the other three TSS pathologies. CONCLUSIONS: Optimal IONM change criteria for prediction vary depending on different TSS pathologies. The optimal monitoring strategy for prediction varies depending on TSS pathologies.

Variability of somatosensory evoked potential and motor evoked potential change criteria in thoracic spinal decompression surgery based on preoperative motor status.

BACKGROUND CONTEXT: Combined somatosensory- and motor-evoked potential (SSEP and MEP) changes for predicting prognosis in thoracic spinal surgery have been variably reported. PURPOSE: We aimed to explore the validity of combined SSEP and MEP for predicting postoperative motor deficits (PMDs) in thoracic spinal decompression surgery (TSDS) and identify a relatively optimal neurophysiological predictor of PMDs in patients based on preoperative motor status. STUDY SETTING: Retrospective study. PATIENT SAMPLE: A total of 475 patients were analyzed. OUTCOME MEASURES: A reduction in muscle strength by more than or equal to one manual muscle testing (MMT) grade postoperatively compared with the preoperative MMT grade was identified as PMDs. Postoperative motor deficits were detected by comparing the preoperative and postoperative physical examination findings in short- and long-term follow-up visits. METHODS: All patients were divided into two subgroups according to preoperative motor status. The following data were collected: (1) demographic data; (2) IONM (intraoperative neuromonitoring) data; and (3) postoperative motor outcomes. Binary logistic regression analysis was performed to assess the efficacy of IONM change to predict PMDs. A receiver operating characteristic curve (ROC) was used to establish optimal IONM warning criteria. RESULTS: Ninety-eight patients had severe preoperative motor deficits (Group S), and 377 patients did not (Group N). MEP and SSEP change was effective for predicting PMDs in the short term (p<.01) and long term (p<.01) for TSDS patients. In Group N, the cutoff values for predicting PMDs in the short term were a decrease of 65% in SSEP amplitude and 89.5% in MEP amplitude of the baseline value. Furthermore, the cutoff values for predicting PMDs in the short term were durations of change of 24.5 minutes for SSEP and 32.5 minutes for MEP. In Group S, however, the cutoff values for predicting PMDs in the short term were a decrease of 36.5% in SSEP amplitude and 59.5% in MEP amplitude of the baseline value. Moreover, the critical values for predicting short-term PMDs were durations of change of 16.5 minutes for SSEP and 17.5 minutes for MEP. CONCLUSIONS: The optimal IONM changes for prediction vary depending on preoperative motor status. Combined SSEP and MEP are excellent for predicting PMDs in TSDS.

Value of multi-channel somatosensory evoked potentials recording in patients undergoing scoliosis correction surgery.

PURPOSE: We aimed to investigate the value of intraoperative multi-channel recording of somatosensory evoked potentials (SSEPs) in patients undergoing posterior instrumentation surgery with fusion. METHODS: This study included 176 patients with scoliosis who underwent posterior correction surgery from January 2019 to June 2020. Among them, 88 patients underwent routine SSEPs monitoring via single-channel (Cz'-Fpz) cortical recording (control group), while the remaining 88 patients underwent multi-channel (Cz'-Fpz and C3'-C4') SSEPs monitoring in the cortex. Chi-square and Fisher's exact tests were used to analyze the influence of age, spinal deformity classification, and Cobb angle on waveform differentiation and the success rate of SSEPs monitoring. RESULTS: Univariate analysis revealed that age, type of scoliosis, and Cobb angle exerted significant effects on the success rate of intraoperative SSEPs monitoring, and the SSEPs waveform differentiation rate was poorest among patients with congenital scoliosis. Intraoperative monitoring results indicated that the success rate of single-channel SSEPs monitoring was 90.9%, while that of multi-channel monitoring was 98.9% (P < 0.05). Among the intraoperative alarm cases, the incidence of adverse events after single-channel SSEPs monitoring was 66.7%, while the incidence of adverse events after multi-channel SSEPs monitoring was only 28.6%. CONCLUSION: Multi-channel cortical SSEPs monitoring can effectively and accurately evaluate the function of the posterior column of the spinal cord. Use of multi-channel SSEP monitoring may help to improve the success rate of monitoring and reduce the incidence of postoperative adverse events in patients with congenital scoliosis.

Multimodal Neuroelectrophysiological Monitoring Combined with Robot-Assisted Placement of a Transiliac-Transsacral Screw for the Treatment of Transforaminal Sacral Fractures.

Objective: This study aimed to evaluate the safety and efficacy of the fixation of transforaminal sacral fractures using TiRobot-assisted transiliac-transsacral (TITS) screws under multimodal neuroelectrophysiological monitoring (MNM). Methods: From January 2019 to May 2021, 22 patients (17 male and 5 female patients) with transforaminal sacral fractures who were treated with closed reduction and placement of TiRobot-assisted TITS screws under MNM were retrospectively evaluated. The average age of the patients was 43.32 ± 11.40 years (range: 19-63). The patients received MNM, including somatosensory-evoked potentials (SEPs), motor-evoked potentials (MEPs), and electromyographic monitoring (EMG), prior to surgery, during closed reduction and the placement of the guidewire and TITS screw, and at the end of surgery. The operation was adjusted according to the MNM results. Results: Overall, 22 TITS screws were inserted in 22 patients, including 5 TITS screws in the S1 body and 17 TITS screws in the S2 body. The average time needed for screw placement was 27.95 ± 6.84 mins, and the average frequency of X-ray fluoroscopy exposures was 31.00 ± 5.56 for each patient. Anterior ring fixation was performed in 4 patients using an external fixator, in 5 patients using cannulated screws, and in 13 patients using reconstruction plates. The mean follow-up time was 14.46 ± 2.46 months (12-20 months). Tornetta and Matta radiographic outcomes were excellent in 10 patients, good in 9 patients, fair in 2 patients, and poor in 1 patient. The proportion of excellent and good ratings was 86.36%. At the final follow-up, the average Majeed score was 82.18 ± 14.52, with clinical outcomes that were excellent in 9 patients, good in 9 patients, fair in 1 patient, and poor in 3 patients. The proportion of excellent and good ratings was 82.82%. Preoperatively, the amplitude of the SEP on the injured side was lower than that on the contralateral side before reduction in 9 patients (>50%). In this study, no screw was mistakenly inserted into the sacral canal, and no surgical site infection occurred. Conclusion: MNM combined with TiRobot assistance can safely implant TITS screws and can effectively identify the neurological function of patients under anesthesia and reduce iatrogenic nerve injury.

Diagnostic Value of Multimodal Intraoperative Neuromonitoring by Combining Somatosensory-With Motor-Evoked Potential in Posterior Decompression Surgery for Thoracic Spinal Stenosis.

Background: Intraoperative neuromonitoring (IONM) has become an increasingly essential technique in spinal surgery. However, data on the diagnostic value of IONM in predicting impending postoperative neurological deficits (PONDs) for patients who underwent posterior decompression surgery for thoracic spinal stenosis (TSS) are limited. Furthermore, patients who are at the highest risk of waveform changes during the surgery remain unknown. Our purpose was to (1) assess the diagnostic accuracy of IONM by combining somatosensory-evoked potential (SSEP) with motor-evoked potential (MEP) in predicting PONDs for patients who underwent the surgery and (2) identify the independent risk factors correlated with IONM changes in our study population. Methods: A total of 326 consecutive patients who underwent the surgery were identified and analyzed. We collected the following data: (1) demographic and clinical data; (2) IONM data; and (3) outcome data such as details of PONDs, and recovery status (complete, partial, or no recovery) at the 12-month follow-up visit. Results: In total, 27 patients developed PONDs. However, 15, 6, and 6 patients achieved complete recovery, partial recovery, and no recovery, respectively, at the 12-month follow-up. SSEP or MEP change monitoring yielded better diagnostic efficacy in predicting PONDs as indicated by the increased sensitivity (96.30%) and area under the receiver operating characteristic (ROC) curve (AUC) value (0.91). Only one neurological deficit occurred without waveform changes. On multiple logistic regression analysis, the independent risk factors associated with waveform changes were as follows: preoperative moderate or severe neurological deficits (p = 0.002), operating in the upper- or middle-thoracic spinal level (p = 0.003), estimated blood loss (EBL) ≥ 400 ml (p < 0.001), duration of symptoms ≥ 3 months (p < 0.001), and impairment of gait (p = 0.001). Conclusion: Somatosensory-evoked potential or MEP change is a highly sensitive and moderately specific indicator for predicting PONDs in posterior decompression surgery for TSS. The independent risks for IONM change were as follows: operated in upper- or middle-thoracic spinal level, presented with gait impairment, had massive blood loss, moderate or severe neurological deficits preoperatively, and had a longer duration of symptoms. Clinical Trial Registration: [http://www.chictr.org.cn]; identifier [ChiCTR 200003 2155].

A Loading Dose of Dexmedetomidine With Constant Infusion Inhibits Intraoperative Neuromonitoring During Thoracic Spinal Decompression Surgery: A Randomized Prospective Study.

Background: The effect of a bolus dose of dexmedetomidine on intraoperative neuromonitoring (IONM) parameters during spinal surgeries has been variably reported and remains a debated topic. Methods: A randomized, double-blinded, placebo-controlled study was performed to assess the effect of dexmedetomidine (1 µg/kg in 10 min) followed by a constant infusion rate on IONM during thoracic spinal decompression surgery (TSDS). A total of 165 patients were enrolled and randomized into three groups. One group received propofol- and remifentanil-based total intravenous anesthesia (TIVA) (T group), one group received TIVA combined with dexmedetomidine at a constant infusion rate (0.5 µg kg-1 h-1) (D1 group), and one group received TIVA combined with dexmedetomidine delivered in a loading dose (1 µg kg-1 in 10 min) followed by a constant infusion rate (0.5 µg kg-1 h-1) (D2 group). The IONM data recorded before test drug administration was defined as the baseline value. We aimed at comparing the parameters of IONM. Results: In the D2 group, within-group analysis showed suppressive effects on IONM parameters compared with baseline value after a bolus dose of dexmedetomidine. Furthermore, the D2 group also showed inhibitory effects on IONM recordings compared with both the D1 group and the T group, including a statistically significant decrease in SSEP amplitude and MEP amplitude, and an increase in SSEP latency. No significance was found in IONM parameters between the T group and the D1 group. Conclusion: Dexmedetomidine delivered in a loading dose can significantly inhibit IONM parameters in TSDS. Special attention should be paid to the timing of a bolus dose of dexmedetomidine under IONM. However, dexmedetomidine delivered at a constant speed does not exert inhibitory effects on IONM data.

The Prognostic Value of Intraoperative Neuromonitoring by Combining Somatosensory- and Motor-Evoked Potentials for Thoracic Spinal Decompression Surgery in Patients with Neurological Deficit.

STUDY DESIGN: Retrospective study. OBJECTIVE: To explore a relation between somatosensory- and motor-evoked potential (SEPs, MEPs) and corresponding thoracic cord function for thoracic spinal decompression surgery (TSDS) in patients with neurological deficit. SUMMARY OF BACKGROUND DATA: Although SEPs and MEPs monitoring has been developed as an essential technique in spinal surgery. There are limited data on the reliability of using SEPs and MEPs for TSDS and its prognosis. METHODS: One hundred twenty patients underwent TSDS in our hospital, 91 patients completed the trial. All the patients were divided into three subgroups according to the changes of MEPs and SEPs: neither SEPs nor MEP deteriorated -. Simply MEP deteriorated and both SEPs and MEP deteriorated -. Bispectral (BIS) was used to monitor the depth of sedation, which ranged from 40 to 60 by varying the infusion speed of anesthetics. The pre- and postoperative spinal function was assessed by muscle strength and Japanese Orthopaedic Association (JOA) score at three time points:1) before surgery; 2) immediately after general anesthesia recovery; 3) after 3-month follow-up. RESULTS: Sixty-nine cases showed neither SEPs nor MEP deteriorated -, 10 cases showed only MEP deteriorated, and 12 cases showed both SEPs and MEP deteriorated -. The patients in the group where neither SEPs nor MEP deteriorated had the best recovery of the extremity muscle strength, the shortest recovery time (8.10 ±â€Š1.60, P < 0.05), and toe movement time (8.50 ±â€Š1.60, P < 0.05). There is a strong correlation between SEPs variability ratio at T4 time point and JOA recovery ratio (JOA RR) in the 3-month follow-up. CONCLUSION: Combined SEPs and MEPs monitoring are important for TSDS in patients with neurological deficit and it is helpful for evaluating postoperative prognosis. It is more accurate to record SEPs at T4 time point to predict the patients' prognosis.Level of Evidence: 3.

Alarm Value of Somatosensory Evoked Potential in Idiopathic Scoliosis Surgery.

BACKGROUND: Somatosensory evoked potential (SSEP) monitoring is performed to examine postoperative clinical findings when a monitoring event was noted intraoperatively and to ascertain the alarm threshold for intraoperative neural damage. METHODS: The tibial SSEP of both lower limbs was recorded intraoperatively in patients with idiopathic scoliosis. Change of SSEP amplitude as opposed to the baseline was categorized into 4 levels: decrease <40%, decrease of 40%-50%, decrease of 50%-60%, and decrease >60%. Postoperative neurologic function of patients was examined and compared with SSEP data. RESULTS: The baseline amplitude before incision was significantly different from the amplitude after spine exposure. An amplitude reduction of >60% during scoliosis correction procedures was observed in 6 legs, and 4 of them had postoperative deterioration in motor status. As the measure of threshold for alarm, an amplitude reduction of >50% compared with baseline resulted in more false-positive outcomes compared with amplitude attenuation of >60%. CONCLUSIONS: Compared with the traditional SSEP baseline before skin incision, the baseline acquired after spine exposure results in more accurate monitoring. A >60% decrease in SSEP amplitude could be a more suitable alarm threshold.

[Baseline and alert level of somatosensory evoked potential monitoring in scoliosis surgery].

OBJECTIVE: To explore the choice of timing for baseline and alert levels of somatosensory evoked potential (SEP) monitoring during scoliosis surgery. METHODS: From March 2011 to December 2014, a total of 113 patients with kyphoscoliosis deformity were monitored intraoperatively by SEP. There were 52 males and 61 females with a mean age of (20 ± 15) years. All the patients were recorded preoperativeandintraoperative SEPs on double lower limbs. Latency and amplitude of SEPs were recorded after anesthesia and vertebral laminae exposure respectively and compared with each other. Intraoperative SEPs were compared to baseline as SEP after exposure and divided into 4 groups of A (<40%), B (40%-50%), C (50%-60%) and D (>60%) according to the reduced amplitude. Nerve functions were recorded during follow-ups. RESULTS: Significant statistical difference existed between SEPs post-anesthesia and SEPs after vertebral laminae exposure (P < 0.01). Compared with SEP post-anesthesia, the latency of SEP after exposure was prolonged with (3.28 ± 1.72) ms (left lower limb) and (3.30 ± 2.09) ms (right lower limb) and amplitude decreased with 0.17(0.39) µV (left lower limb) and 0.19(0.40) µV (right lower limb). There was a positive relationship of impaired nerve function between groups C and D (P < 0.05). CONCLUSION: Adopting SEP waveform after exposure as a baseline can improve the accuracy of SEP monitoring during scoliosis surgery. Intraoperative alarm with a reduced amplitude over 50% as the standard may be too sensitive. Alert with a reduced amplitude of over 60% reduces the false positive rate of alarm.

A Rare Complication of Spine Surgery: Guillain-Barré Syndrome.

OBJECTIVE: Since little has been reported about Guillain-Barré syndrome (GBS) after spine surgery, we sought to determine some of the clinical features and the management of the condition. METHODS: A total of 4 cases of GBS after spine surgery were included. The medical charts of the patients were reviewed to obtain demographic and clinical details. All the patients underwent neurologic and electrophysiologic examinations and were followed up after surgery. RESULTS: The onset of symptoms about GBS was 2-7 days after the operation. Neurologic evaluation showed weaknesses of upper and lower extremities and repeal of tendon reflexes. The patients exhibited typical clinical symptoms and signs of GBS and electromyographic findings. Lumbar puncture was performed in 2 cases, and cerebrospinal fluid examination showed albuminocytological dissociation. All the 4 patients were diagnosed as GBS on the basis of typical clinical, laboratory, and electrophysiologic findings. Intravenous immunoglobulin was instituted. At follow-up, one patient needed ventilator support; one patient could transfer from bed to chair; one walked with assistive devices; and the remaining patient had residual minor neurologic deficits. CONCLUSIONS: These cases warn surgeons to be alert to the association of GBS and spine surgery. On the basis of our experience, we recommend consideration of this rare diagnosis in patients with paralysis after spine surgery.