Continuous Intraoperative Monitoring Research Articles

Technical Instructions for Continuous Intraoperative Neural Monitoring in Thyroid Surgery

Technical Instructions for Continuous Intraoperative Neural Monitoring in Thyroid Surgery

Modification of the Surgical Strategy for the Dissection of the Recurrent Laryngeal Nerve Using Continuous Intraoperative Nerve Monitoring.

Modification of the Surgical Strategy for the Dissection of the Recurrent Laryngeal Nerve Using Continuous Intraoperative Nerve Monitoring.

Continuous intraoperative recurrent laryngeal nerve monitoring during thyroid surgery. The Greek experience

Introduction: Recurrent laryngeal nerve injury is a serious complication of thyroid surgery. The anatomic dissection and visual identification of the inferior laryngeal nerve is the standard of care to avoid this complication. The intermittent intraoperative nerve stimulation technique has failed to improve nerve safety. The continuous recurrent laryngeal nerve monitoring is a promising new technique, currently under study to evaluate its feasibility and safety outcomes. We present our experience of applying this method in a private thyroid surgery clinic in Greece

Modification of the Surgical Strategy for the Dissection of the Recurrent Laryngeal Nerve Using Continuous Intraoperative Nerve Monitoring.

The aim of this study was to describe first experiences and changes in management using continuous intraoperative neuromonitoring (C-IONM) in thyroid and parathyroid surgery. Retrospective analysis of patients who underwent surgery with C-IONM since 2012. Surgical maneuvers were modified when electrophysiologic events occurred. Patients with persistent loss of signal (LOS) underwent postoperative laryngoscopy. One hundred and one patients (of 1586 neck surgeries) were included and 19 had events: In 13 these were temporary (resolved before end of surgery) and led to intraoperative modifications in surgical approach; in all cases traction was released, and in 8, recurrent laryngeal nerve (RLN) approach was changed [superior approach (2), inferior approach (2), both (4)]. Six patients had persistent LOS (5.9%, present at end of procedure), with RLN palsy (RLNP) on postoperative day 1: In three, LOS occurred at electrode placement on the vagus nerve, leading to distal placement of the electrode allowing ipsilateral dissection under continuous monitoring; all three had complete recovery at 6months. In the three other patients, LOS occurred on the RLN: one probable thermal, one traction lesion and one accidental section of the anterior RLN branch. The RLN recovered within 6months in two patients, and in the third, RLNP persisted after 6months (1/101=1%). C-IONM provides real-time evaluation of the RLN function, allowing for adaptation of surgical maneuvers to prevent RLNP. It seems particularly useful in difficult cases like redo neck surgery, invasive thyroid cancer and intrathoracic or large goiter. Care should be given at electrode placement on the vagus nerve.

Opportunities and challenges of intermittent and continuous intraoperative neural monitoring in thyroid surgery.

The number of thyroid operations and there radically continues to rise in the western hemisphere, bringing prevention of recurrent laryngeal nerve (RLN) palsy to the fore. Overall, the incidence of RLN palsy is fairly low but continues to prompt litigation for malpractice. In an effort to diminish transient, and more importantly permanent, RLN palsy rates, intraoperative neuromonitoring (IONM) has been advocated as a risk minimization tool. Recent meta-analyses of studies, many of which were limited by poor study design and the sole use of intermittent nerve stimulation, were unable to demonstrate superiority of IONM over mere anatomic RLN dissection. This is where continuous IONM (CIONM) comes into play: this technology enables the surgeon to (I) identify impending nerve injury as it unfolds; (II) release distressed nerves by reversing causative surgical maneuvers; and (III) verify functional nerve recovery after intraoperative loss of the electromyographic signal. Despite this superiority, CIONM is not devoid of methodological limitations, which need to be accounted for. This review summarizes the current key achievements of IONM; outlines opportunities for improvement regarding clinical implementation; and suggests areas of future research in this rapidly evolving field.

Mastoid Epidermoid Tumor and Associated Dural Arteriovenous Fistula with Venous Sinus Occlusion

Dural arteriovenous fistula (DAVF) is an abnormal vascular connection between arterial and venous channels within dura mater. Although DAVFs have been linked to other types of intracranial tumors, this is the first case reporting the association between DAVF and an epidermoid tumor. A middle-aged patient with chronic headache presented with Borden type II DAVF draining into the right transverse sigmoid junction and was also found to have an epidermoid tumor over the right mastoid. The patient underwent staged embolization of the fistula through both transvenous and transarterial routes. Continuous intraoperative venous pressure monitoring confirmed marked reduction in intracranial venous pressure, and the patient's symptoms completely resolved. However, the fistula still remained. The residual DAVF was then surgically disconnected, and the epidermoid tumor was resected in the same procedure. This case demonstrates a DAVF can be associated with an epidermoid tumor. Tumor can compromise the venous outflow, which can then lead to intracranial venous hypertension and development of the DAVF. Venous pressure monitoring offers an objective method to verify resolution of venous hypertension, which might correlate with resolution of clinical symptoms.

O179 Intraoperative blink reflex in microvascular decompression for hemifacial spasm. A case report and proposal of a new method to monitor the efficiency of decompression

Objectives To report the utility of blink reflex (BR) monitoring in microvascular decompression (MVD) for hemifacial spasm (HFS). Methods We report a case of a 64-year-old patient with HFS who underwent MVD with continuous intraoperative neurophysiological monitoring (IONM) of motor, sensory and auditory evoked potentials. The abnormal muscle response (AMR) was monitored with stimulation of zygomatic and buccal branch (zAMR, bAMR) and recording from representative muscles innervated by all facial nerve (FN) branches. Additionally the BR was utilized to monitor the FN functionality. Results Before incision, a similar to AMR-spread phenomenon (BR-spread) was observed when the supraorbital branch of trigeminal nerve was stimulated to elicit BR. Both AMRs (zAMR, bAMR) disappeared during MVD, indicating sufficient FN decompression. Concurrently a similar disappearance from BR-spread and FN-MEPs was observed. During closing all responses (AMRs, BR-spread, FN-MEPs) reappeared. The HFS was clinically present right after the surgery but the patient was relieved from the symptoms a few hours later. Discussion The BR-spread and FN-MEPs showed an AMR-like pattern during MVD. The reappearance of AMRs predicted the immediate but not the long term outcome of HFS-MVD. The BR and FN-MEPs are not reliable to monitor the FN integrity in HFS-MVD due to decompression depended responses. We propose further research to investigate the benefits of BR in HFS-MVD. Conclusions The BR-spread is potentially an alternative IONM tool to determine whether the MVD of HFS is sufficient. Significance A new IONM method is proposed to monitor HFS-MVD.

Contralateral R1 and R2 components of the laryngeal adductor reflex in humans under general anesthesia

To demonstrate that under total intravenous general anesthesia (TIVA), the contralateral R1 (cRI) and contralateral R2 (cR2) components of the laryngeal adductor reflex (LAR) can be reliably elicited; to determine effects of topical anesthesia and inhalational anesthesia on the LAR; and to discuss how this technique may be utilized to continuously monitor the vagus nerve reflex arc. Case series. Vocal fold mucosa was electrically stimulated via endotracheal tube surface-based electrodes to elicit a LAR. Responses were recorded using the endotracheal tube electrode contralateral to the simulating electrode for each side. Twenty-one patients (31 nerves at risk), aged between 28 to 84 years, who underwent thyroid and cervical spine surgeries (4 males, 17 females) were included. cR1 responses were reliably elicited in all patients, and cR2 responses were obtained in 14 patients (66.6%). Mean cR1 latencies ± standard deviation were 22.5 ± 2.5 milliseconds (ms) (left) and 23.4 ± 3.3 ms (right). Mean cR1 amplitudes were 237.9 ± 153.9 microvolts (uV) (left) and 265.0 ± 226.5 uV (right). Mean R2 latencies were 59.8 ± 4.9 ms (left) and 61.8 ± 7.9 ms (right). Intraoperative reversible cR1 amplitude decreases correlated temporally with surgical maneuvers stretching or compressing the RLN or internal branch of the superior laryngeal nerve (iSLN). Inhalational anesthetic agents abolished cR2 and minimized cR1 at mean alveolar concentrations > 0.5. Topical lidocaine significantly reduced LAR amplitude. LAR cR1 and cR2 responses are present in humans under TIVA and may afford some airway protection against aspiration under anesthesia. They are inhibited by inhalational anesthetics and topical lidocaine. Continuous intraoperative iSLN and RLN monitoring are possible using surface-based endotracheal tube electrodes alone to stimulate and record cR1 responses. 4. Laryngoscope, 127:E443-E448, 2017.

Safety, Utility, and Clinical Results of Continuous Intraoperative Electrophysiologic Monitoring in 1.5T iMRI-Guided Surgery.

To show that the combined use of intraoperative high-field MRI (iMRI) and electrophysiologic monitoring (IOM) is feasible, safe, and beneficial for patients. The setup, surgical, imaging, and clinical results of 110 patients with eloquent intracranial lesions with the combined use of 1.5T iMRI and IOM were analyzed. 187 iMRI scans were performed with IOM needles in place, resulting in a total experience of using >4000 electrodes in the iMRI. No complication (ferromagnetic or relevant heating/burning of skin) was caused by the combined use of both technologies. Surgically induced severe postoperative sensorimotor deficits were seen in 11.8%. The surgeon's estimation of a "complete resection" proved to be true postoperatively in 90.3%. If the resection was stopped due to worsening of IOM, postoperative MRI revealed residual disease to be located in direct vicinity of eloquence in 27 of 28 cases, but not in other parts of the resection cavity. Of these patients, only 7% (2 of 28) had relevant new deficits after 3 months. In 82 patients (74.5%), the resection was continued after the iMRI scan, whereas in only 18 patients (16.4%) the resection was already completed at this point. The combined use of IOM and 1.5T iMRI is feasible and safe. The complementary use of both technologies might result in more radical resections at comparable surgically induced neurologic deficits. If available and indicated, the combined use of IOM and iMRI should be performed on a routine basis.

Facial nerve sparing surgery for large vestibular schwannomas.

Nowadays, there is a general trend in vestibular schwannoma (VS) surgery favoring near-total or subtotal tumor resection (NTR/STR) with facial nerve (FN) function preservation rather than gross total resection (GTR) with high risk of FN damage. The surgical technique of FN sparing in large VS includes patient-tailored image-guided craniotomy, continuous intraoperative neurophysiological monitoring (INM), intracapsular wide tumor debulking, and only final extracapsular dissection with FN course identification and brainstem decompression. A small amount of residual tumor along the FN is accepted in order to not damage the nerve. Postoperative radiosurgery workup is then recommended. NTR/STR resection with FN function sparing is a valid option for large VS.

Continuous intraoperative neural monitoring in thyroid surgery: a Mexican experience.

Intraoperative continuous neural monitoring (C-IONM) during thyroid surgery has been recognized as a useful tool to identify and confirm recurrent laryngeal nerve integrity. The aim of the present study is to analyze electromyographic features and thresholds for normal vocal fold function in our initial experience with C-IONM in thyroid surgery. C-IONM was utilized in 57 patients who underwent thyroid surgery between July 2012 and December 2015. EMG parameters were analyzed looking for potential predictors of postoperative vocal fold dismotility. There were 54 females (94.7%) and 3 males (5.3%) with a mean age of 46.7±11.6years. C-IONM was successfully registered in 89 of 107 nerves at risk (83.1%). Mean basal amplitude was 727.31±471.25μV and mean final amplitude was 650.27±526.87μV (P = 0.095, CI 95% 13.83-167.91). Mean basal latency was 5.23±1.42 mS and mean final latency was 5.18±1.50 mS (P = 0.594, CI 95% 0.39-0.24). Four patients had transient postoperative vocal fold paresis. None of these four patients had loss of signal (LOS), three had transient decrease in amplitude, and one had a normal registry throughout the operation. C-IONM is a useful tool to identify patients in whom intraoperative RLN is at risk during surgery. Final amplitude above 500μV and no LOS is associated with RLN integrity and normal postoperative vocal fold function.

Tiroidektomi esnasında rekürren laringeal sinirin yaralanma mekanizmaları ve devamlı intraoperatif sinir monitorizasyonunun cerrahi strateji üzerine etkisi

Objective: To evaluate the mechanisms of recurrent laryngeal nerve (RLN) injury during thyroidectomy and the impact of continuous intraoperative nerve monitoring (C-IONM) on surgical strategy. Material and Methods: The data of 364 consecutive patients who underwent total or hemithyroidectomy between June 2014 and January 2016 were evaluated prospectively. All patients underwent thyroidectomy by using C-IONM. The mechanisms of RLN injury and the outcomes of the patients with combined events (CE) and loss of signal (LOS) were evaluated. Results: Combined events (CE) occurred in 6 (1.6%) of these 364 patients. The reduced electromyographic (EMG) amplitude and prolonged latency recovered in all patients intraoperatively by the reversal of the medial traction maneuver. Loss of signal (LOS) occurred in 7(1.9%) patients. The mechanisms of LOS was ligation of the anterior branch of the nerve in 1 (14.3%) patient and traction in 4(57%) patients. The probable mechanism of LOS was traction or transection in 2 (28.6%) patients in whom LOS occurred during the dissection of the intrathoracic portion of large substernal goiter. Of these 7 patients, LOS recovered intraoperatively after 20 minutes of waiting in 1(14.3%) patient. In the remaining 6 (85.7%) patients, unilateral vocal cord paralysis (VCP) was verified on the postoperative laryngoscopic examination. The overall temporary and permanent unilateral VCP rates were 1.6% (n=6) and 0.8% (n=3), respectively in these 364 patients. No bilateral VCP was recorded. Continuous intraoperative nerve monitoring (C-IONM) prevented bilateral VCP in 1 (0.3%) patient. Conclusion: The major advantage of C-IONM is to alert the surgeon for imminent RLN injury. Combined event (CE) is a pathognomonic sign of impending nerve injury that may progress to LOS. This situation enables the surgeon to adverse (reverse) the surgical maneuver before permanent damage to the nerve sets in. Continuous intraoperative nerve monitoring (C-IONM) can also immediately spot RLN injury during thyroidectomy. This property of C-IONM gives the surgeon the opportunity for an early corrective action to release the affected nerve promptly. In case of permanent LOS, staged thyroidectomy could be planned to prevent bilateral VCP.

Facial Nerve Function and Quality of Resection in Large and Giant Vestibular Schwannomas Surgery Operated By Retrosigmoid Transmeatal Approach in Semi-sitting Position with Intraoperative Facial Nerve Monitoring.

Large and giant vestibular schwannomas pose a real problem in their management. The preservation of facial nerve function may limit tumor resection despite the use of intraoperative monitoring of the facial nerve. In Algeria, vestibular schwannomas represent 5% of all intracranial tumors operated on, 80.5% of which are large or giant. From January 2010 to December 2015, 151 large and giant vestibular schwannomas were operated in our department. Tumor diameter was between 30 and 60mm. The most common presenting symptom was hearing loss, which was observed in 41.66% of all our patients. All patients were operated in the semi-sitting position with opening of the posterior wall of the internal auditory canal and under continuous intraoperative facial nerve function monitoring. Tumor resection was total in 126 patients. Anatomic preservation of the facial nerve was the reason for nontotal resection in 25 patients. The facial nerve was anatomically preserved in 149 patients. Two years after surgery, the facial nerve function was grade I-II House-Brackmann (H-B) score in 124 cases (82%),grade III-IV H-B score in 21 cases (14%), and grade V-VI H-B score in 06 cases (04%). The status and the improvement of postoperative facial nerve function depend on 4 factors: anatomic preservation of nerve,stimulation threshold, cystic form, and the presence of train activity. The development of anesthesia techniques and microsurgery and the systematic use of intraoperative monitoring of the facial nerve have allowed us to move from a life preservation era to another era of preservation of function.

Continuous intraoperative vagus nerve stimulation for monitoring of recurrent laryngeal nerve during minimally invasive esophagectomy.

For squamous cell carcinoma of the esophagus, extended mediastinal lymphadenectomy especially around the bilateral recurrent laryngeal nerves (RLN) is associated with high risk of nerve injury. This does not only result in hoarseness of voice, increase the chance of pulmonary complications, but would also affect the quality of life of patients in the long term. Methods to improve safety of lymphadenectomy are desirable. Continuous intraoperative nerve monitoring (CIONM) based on a system using vagus nerve stimulation was tested. In thyroidectomy, this system has been shown to be useful. Our patient cohort was unselected, with the intent to perform bilateral RLN dissection undergoing video-assisted thoracoscopic (VATS) esophagectomy. Intermittent nerve stimulation for mapping and CIONM were employed to monitor left RLN nodal dissection, while only intermittent stimulation was used for the right RLN. CIONM has the potential to aid RLN dissection. The learning curves for the placement technique of CIONM, the threshold level and the interpretation of myographic amplitude and latency have been overcome. With the availability of nerve mapping and CIONM, more aggressive and thorough nodal dissection may be possible with less fear of RLN injury.

Left recurrent laryngeal nerve dissection. Both CIONM & Ball-tip Monopolar Stimulator Probe were used for recurrent laryngeal nerve dissection. CIONM, continuous intraoperative nerve monitoring

Left recurrent laryngeal nerve dissection. Both CIONM & Ball-tip Monopolar Stimulator Probe were used for recurrent laryngeal nerve dissection. CIONM, continuous intraoperative nerve monitoring

Continuous Intraoperative Nerve Monitoring during Thyroid Surgery: Realistic Utility

Continuous Intraoperative Nerve Monitoring during Thyroid Surgery: Realistic Utility

An optimized abnormal muscle response recording method for intraoperative monitoring of hemifacial spasm and its long-term prognostic value

BackgroundIntraoperative electrophysiological monitoring is used to determine whether decompression is sufficient during microvascular decompression (MVD) for hemifacial spasm (HFS). However, the real offending vessel is sometimes neglected by the neurosurgeons. Here, we reported our experience in using optimized abnormal muscle response (AMR) monitoring and continuous intraoperative monitoring for MVD. MethodsThis study included 2161 HFS patients who underwent MVD using traditional (1023 patients) and optimized (1138 patients) methods. Modified AMR monitoring was adopted in our study, with the zygomatic branch of the facial nerve stimulated and the temporal branch, buccal branch, marginal mandibular branch and cervical branch of the facial nerve detected for AMR. These cases were analyzed retrospectively with emphasis on the postoperative outcomes and intraoperative findings. The therapeutic effect was evaluated at day 1, month 3 and year 1 after operation. ResultsThe relief rate at day 1, month 3 and year 1 after operation for patients who employed optimized AMR recording method was 95.1%, 97.4% and 99.3%, comparing with 92.2%, 95.0% and 97.8% in traditional method. There was significant difference in achieved immediate remission and recovery rate during 12-month follow-up between the two groups (P < 0.05). The modified intraoperative monitoring showed the sensitivity of AMR disappearance to judge the relief at day 1, month 3 and year 1 after HFS operation was 95.7%, 96.3% and 97.3%, respectively; the specificity was 44.6%, 43.3% and 50.0%, respectively; the accuracy was 93.1%, 94.9% and 97.4%, respectively. ConclusionsOur findings demonstrated that the optimized method could improve the positive detection rate of AMR and accuracy of decompression effect prediction. The evaluation for the decompression effect by optimized intraoperative monitoring can increase the immediate remission rate and reduce the delayed recovery rate.

Continuous Intraoperative Monitoring of Temporal Lobe Epilepsy Surgery

Background/Aims: The monitoring of interictal epileptiform discharge rates (IEDRs) all along anterior temporal lobe resections (ATLRs) has never been reported. Here the effect of ATLR on continuous IEDR monitoring is described. Methods: IEDRs computed automatically during entire interventions were recorded in 34 patients (38.2%, 13/34 depth; 61.8%, 21/34 scalp electrodes only). Monitorings were invalidated when burst suppression occurred or if initial IEDRs were <5. Results: Monitoring was successful for 69.2% (9/13) of the patients with depth recordings and for 4.8% (1/21) of the patients with scalp recordings. Burst suppressions precluded it in 30.8% (4/13) of the depth and in 57.1% (12/21) of the scalp recordings. Initial IEDRs were <5 for 38.1% (8/21) of the scalp recordings. Significant IEDR decreases were observed in 8/10 patients with successful monitoring. These decreases started with resection of the superior temporal gyrus. IEDRs decreased further with amygdalohippocampectomy in 3/5 patients. At the 12-month follow-up, all patients with IEDR decreases remained seizure free; both patients without did not. Conclusion: IEDR monitoring was possible with depth, but not with scalp electrodes. IEDR decreases started with resection of the superior temporal gyrus. A larger patient cohort is necessary to confirm the high predictive values of IEDR monitoring that could become a tool for surgery customization.

Early permanent disappearance of abnormal muscle response during microvascular decompression for hemifacial spasm: a retrospective clinical study.

The objective of this study is to explore the cause of early abnormal muscle response (AMR) disappearance during microvascular decompression for hemifacial spasm and the clinical outcomes of these patients. Three hundred seventy-two patients received microvascular decompression (MVD) under intraoperative electrophysiological monitoring in Nanjing Drum Tower Hospital in 2014; the characteristic AMR of HFS was observed in 359 patients during the operation. And the 359 patients were divided into two groups based on whether AMR had remained before the beginning of the decompression procedure for offending vessels. Thirty-three patients who showed a permanent disappearance of AMR before the beginning of decompression were regarded as group I. Dural opening and the succeeding CSF drainage produced a permanent disappearance of AMR in 13. During the dissection of lateral cerebellomedullary cistern, a permanent disappearance of AMR was found in 20 patients. Thirty-two patients were cured immediately; delayed resolution (7days after surgery) was found in one patient. No complications were observed and no recurrence was found during the follow-up period in the 33 patients. In the other 326 patients (group II), AMR disappeared temporarily before the beginning of the decompression procedure for offending vessels in 42 patients. After decompression, AMR disappeared completely in 305 patients. Two hundred sixty-seven patients were cured immediately and 57 patients got a delayed resolution (2days to 45weeks after surgery). The two left did not get a complete abolition of spasm. Three cases of hearing loss, one hoarseness, and nine delayed facial paralysis were observed. The reason of early abnormal muscle response disappearance may be that the degree of neurovascular compression was not serious; these patients were more likely to get an immediate cure. Continuous intraoperative electrophysiological monitoring of AMR is necessary.

Continuous intraoperative neural monitoring of the recurrent nerves in thyroid surgery: a quantum leap in technology.

The continuous intraoperative neural monitoring (CIONM) technique is increasingly acknowledged as a useful tool to recognize impending nerve injury and to abort the related manoeuvre to prevent nerve injury during thyroid surgery. CIONM provides valuable real-time information constantly, which is really useful during complex thyroid surgeries especially in the settings of unusual anatomy. Thus, CIONM overcomes the key methodological limitation inherent in intermittent nerve monitoring (IINOM); which is allowing the nerve to be at risk in between the stimulations. The clinically important combined electromyographic (EMG) event, indicative of impending recurrent laryngeal nerve (RLN) injury, prevents the majority of traction related injuries to the anatomically intact RLN enabling modification of the causative surgical manoeuvre in 80% of cases. These EMG changes can progress to loss of EMG signal with postoperative vocal cord palsy (VCP) if corrective action is not taken. As a further extension, CIONM also helps to identify intraoperative functional nerve recovery with restitution of amplitude to ≥50% of initial baseline; this allows continuing of resection of contralateral side. CIONM facilitates for early corrective action before permanent damage to the nerve has been done. CIONM is a recent but rapidly evolving technique, constantly being refined by various studies focusing on improvement in its implementation and interpretation, as well as on the elimination of the technical snags.