Hemithyroidectomy, does the indication influence the outcome?

PURPOSE

Hemithyroidectomies are mainly performed for two indications, either therapeutically to relieve compression symptoms or diagnostically for suspicious nodule(s). In case of the latter, one could consider the approach to be rather extensive since the majority of patients have no symptoms and will have benign disease. The aim of this study is to investigate the complication rates of diagnostic hemithyroidectomy and to compare it with the complication rates of compressive symptoms hemithyroidectomy.

METHODS

Data from patients who had undergone hemithyroidectomy either for compression symptoms or for excluding malignancy were extracted from a well-established Scandinavian quality register (SQRTPA). The following complications were analyzed: bleedings, wound infections, and paresis of the recurrent laryngeal nerve (RLN). Risk factors for these complications were examined by univariable and multivariable logistic regression.

RESULTS

A total of 9677 patients were included, 3871 (40%) underwent surgery to exclude malignancy and 5806 (60%) due to compression symptoms. In the multivariable analysis, the totally excised thyroid weight was an independent risk factor for bleeding. Permanent (6-12 months after the operation) RLN paresis were less common in the excluding malignancy group (p = 0.03).

CONCLUSION

A range of factors interfere and contribute to bleeding, wound infections, and RLN paresis after hemithyroidectomy. In this observational study based on a Scandinavian quality register, the indication "excluding malignancy" for hemithyroidectomy is associated with less permanent RLN paresis than the indication "compression symptoms." Thus, patients undergoing diagnostic hemithyroidectomy can be reassured that this procedure is a safe surgical procedure and does not entail an unjustified risk.

Necessity of Routinely Testing the Proximal and Distal Ends of Exposed Recurrent Laryngeal Nerve During Monitored Thyroidectomy

OBJECTIVES

Intraoperative neuromonitoring (IONM) is a useful tool to evaluate the function of recurrent laryngeal nerve (RLN) in thyroid surgery. This study aimed to determine the necessity and value of routinely testing the proximal and distal ends of RLN.

METHODS

In total, 796 patients undergoing monitored thyroidectomies with standardized procedures were enrolled. All 1346 RLNs with visual integrity of anatomical continuity were routinely stimulated at the most proximal (R2p signal) and distal (R2d signal) ends after complete RLN dissection. The EMG amplitudes between R2p and R2d signals were compared. If the amplitude of R2p/R2d ratio reduction (RPDR) was over 10% or loss of signal (LOS) occurred, the exposed RLN was mapped to identify the injured point. Pre- and post-operative vocal cord (VC) mobility was routinely examined with video-laryngofiberscope.

RESULTS

Nerve injuries were detected in 108 (8%) RLNs, including 94 nerves with incomplete LOS (RPDR between 13%-93%) and 14 nerves with complete LOS. The nerve injuries were caused by traction in 80 nerves, dissecting trauma in 23 nerves and lateral heat spread of energy-based devices in 5 nerves. Symmetric VC mobility was found in 72 nerves with RPDR ≤50%. The occurrence of abnormal VC mobility (weak or fixed) was 14%, 67%, 100%, and 100% among the different RPDR stratifications of 51%-60%, 61%-70%, 71%-80%, and 81-93%, respectively. Of the 14 nerves with complete LOS, all showed fixed VC mobility. Permanent VC palsy occurred in 2 nerves with thermal injury.

CONCLUSION

Routinely testing the proximal and distal ends of exposed RLN helps detect unrecognized partial nerve injury, elucidate the injury mechanism and determine injury severity. The procedure provides accurate information for evaluating RLN function after nerve dissection and should be included in the standard IONM procedure.

Warning criterion to predict recurrent laryngeal nerve injury with percentage reduction of the amplitude of V2/R2d in neuromonitoring thyroidectomy

OBJECTIVE

To evaluate the contribution of amplitude reduction compared vagal stimulation at the end of thyroid dissection (V2) to the most distal RLN stimulation during thyroidectomy in predicting postoperative vocal cords paralysis (VCP).

METHODS

Patients with intact preoperative RLN function who underwent monitored thyroidectomy between August 2017 and April 2018 were included. We routinely tested the exposed RLN at the lowest proximal end (R2p signal) and the most distal end near the laryngeal entry point (R2d signal), and then routinely detected the vagal nerve at the horizontal plane of the inferior pole of thyroid with 2mA stimulation current. The cut-off value was calculated with Receiver Operating Characteristic curve. Rates of specificity, sensitivity, negative predictive value, positive predictive value (PPV) for V2/R2d and R2p/R2d were compared.

RESULTS

Percentage reduction of the amplitude of V2/R2d ranged from 34.8% to 76.7%. Twenty-two (1.5%) nerves developed temporary VCP, in which one nerve with VCP showed no significant amplitude reduction at the end of the surgery. There was no permanent or bilateral VCP. Sensitivity, specificity, PPV, NPV, and accuracy for the amplitude reduction of V2/R2d> 60% were 95.5%, 99.8%, 99.9%, 98.2%, respectively, for R2p/R2d were 99.5%, 99.2%, 63.6%, 99.9%, 97.7%, respectively.

CONCLUSION

Percentage reduction of the amplitude of V2/R2d is a reliable and practical warning criterion for RLN injury. When the amplitude reduction> 60% surgeons should consider the possibility of postoperative VCP and correct some surgical maneuvers.

Efficacy of Transcartilaginous Electrodes for Intraoperative Neural Monitoring During Thyroid Surgery

Objectives.

This study was conducted evaluate the efficacy of electromyography (EMG) using transcartilaginous (TC) electrodes through the thyroid cartilage and perichondrium.

Methods.

We prospectively collected EMG data from intraoperative neuromonitoring (IONM) of 54 nerves at risk in 38 patients during thyroidectomy. We followed standardized IONM procedures in all operations. EMG signals from both endotracheal tube (ET) electrodes and TC needle electrodes were recorded simultaneously. We compared the characteristics of the EMG signals and the efficacy of both methods.

Results.

Significantly higher mean EMG amplitudes were recorded by TC electrodes than by ET electrodes in all four-step procedures (V1-R1-R2-V2, P<0.001). Loss of signal (LOS) occurred in five patients in ET electrodes, but in only two patients in TC electrodes. Postoperative laryngoscopy revealed recurrent laryngeal nerve palsy in the two patients who showed LOS from both the ET and TC electrodes, and vocal cord movement was intact in the other three patients. Therefore, the positive predictive values of LOS in ET and TC electrodes were 40% and 100%, respectively.

Conclusion.

EMG recording using TC needle electrodes is feasible and effective, making it a good alternative technique for IONM.

Correlation Between Electrophysiological Changes and Outcomes of Vocal Cord Function in 1764 Recurrent Laryngeal Nerves with Visual Integrity During Thyroidectomy

Background: The correlation between the injured recurrent laryngeal nerve (RLN) with incomplete loss of signal (LOS) and the outcomes of vocal cord function is still not well understood. This large cohort validation study was aimed to evaluate the effectiveness of the warning criterion, the reduction of the R2p/R2d ratio, in neuromonitoring during thyroidectomy. Methods: A total of 1108 consecutive patients (1764 nerves) with normal vocal cord function undergoing monitored thyroidectomy were included. Standardized intraoperative neuromonitoring procedures were strictly followed, after complete dissection of RLN, the exposed RLN was routinely stimulated at the lowest proximal end (R2p signal) and the most distal end near the laryngeal entry point (R2d signal). If the reduction of the R2p/R2d ratio (([R2d - R2p]/R2d) × 100%) reached >20%, the whole exposed RLN would be checked to pinpoint the injured area of the nerve. Results: Visual anatomical integrity of the RLN was ensured in all 1764 nerves. Eighteen nerves had complete LOS, and the other 97 nerves had incomplete LOS where the reduction of the R2p/R2d ratio ranged from 21% to 84%. Postoperative temporary vocal cord paralysis (VCP) was noted in 11 (61.1%) RLNs with complete LOS and 16 (16.5%) RLNs with incomplete LOS, where the reduction of the R2p/R2d ratio ranged from 63% to 84%. The positive predictive value of a R2p/R2d ratio >63% for postoperative VCP was 79.4%. Conclusions: Testing and comparing the R2p and R2d signals were useful to detect RLN neurophysiologic injury, elucidating the mechanism of nerve injury and predicting vocal cord function. Determining R2p-R2d was found to be essential and can be applied in routine neuromonitoring thyroidectomy.

Usefulness of intraoperative nerve monitoring in esophageal cancer surgery in predicting recurrent laryngeal nerve palsy and its severity

BACKGROUND

Recurrent laryngeal nerve (RLN) palsy is a critical postoperative complication in esophageal cancer surgery. However, intraoperative prediction of its occurrence and severity is difficult. In this prospective study, we evaluated the usefulness of intraoperative nerve monitoring (IONM) in predicting RLN palsy and its severity.

METHODS

Twenty patients who underwent subtotal esophagectomy with 3-field lymph node dissection were enrolled. Intraoperative electromyography (EMG) amplitudes of the vocal cords were measured by IONM at RLN and vagus nerve (VN) stimulation. Comparison was made between the vocal cords with RLN palsy and those without palsy and additionally between the vocal cords with transient RLN palsy and those with persistent palsy.

RESULTS

Among 40 vocal cords in 20 patients, 26 were intact and 14 were paralyzed. Seven had transient, six had permanent palsy. The mean EMG amplitude of intact vocal cords was significantly larger than that of paralyzed ones at VN (506 ± 498 µV vs. 258 ± 226 µV, p = 0.022) and RLN stimulation (642 ± 530 µV vs. 400 ± 308 µV, p = 0.038). The cut-off value for postoperative palsy were 419 µV [positive predictive value (PPV): 48.0%, negative predictive value (NPV): 84.6%] at VN and 673 µV (PPV: 44.8%, NPV: 90.9%) at RLN stimulation. The mean EMG amplitude of persistently paralyzed vocal cords tended to be small, compared with that of recovered ones at both VN (168 ± 173 µV vs. 336 ± 266 µV, p = 0.11) and RLN (244 ± 223 µV vs. 536 ± 344 µV, p = 0.051) stimulation.

CONCLUSION

The absolute EMG amplitude of IONM might be helpful to predict the occurrence and severity of RLN palsy after esophageal surgery although the predictive value is low.

Intermittent intraoperative nerve monitoring in thyroid reoperations: Preliminary results of a randomized, single-surgeon study

BACKGROUND

The purpose of this study was to evaluate whether intermittent intraoperative nerve monitoring (IONM) could reduce the incidence of recurrent laryngeal nerve (RLN) paralysis in thyroid reoperations.

METHODS

Enrolled patients were randomly assigned into the nerve integrity monitor (NIM) group and the control group.

RESULTS

The incidence of temporary RLN paralysis and permanent RLN paralysis was 12.2% and 4.9% in the NIM group compared with 7.0% and 2.3% in the control group (p = .658 and p = .966, respectively). The incidence of surgeon-related paralysis, tumor-related paralysis, and scar-related paralysis was 4.9%, 7.3%, and 4.9% in the NIM group compared with 4.7%, 2.3%, and 2.3% in the control group, respectively (p = 1, p = .575, and p = .966, respectively).

CONCLUSION

Intermittent IONM could not provide additional benefits to reduce the incidence of temporary RLN paralysis and permanent RLN paralysis in thyroid reoperations. It could not reduce the incidence of paralysis caused by unintentional injuries. © 2016 Wiley Periodicals, Inc. Head Neck 38: E1993-E1997, 2016.

Loss of signal in recurrent nerve neuromonitoring: causes and management

During recurrent laryngeal nerve (RLN) neuromonitoring in thyroid surgery, laryngeal electromyography (EMG) amplitude may be correlated with the number of muscle fibers participating in the polarization and these might be correlated with the function of RLN. If RLN is severely injured during the operation, most nerve fibers do not transmit nerve impulse and substantial decrease of EMG amplitude or loss of signal (LOS) will occur. True LOS at the end of an operation often indicates a postoperative fixed vocal cord, and the surgeon should consider the optimal contralateral surgery timing in patients with planned bilateral thyroid operation to avoid the disaster of bilateral vocal cord palsy. However, LOS recovery and false LOS may occur and may lead to an unnecessary 2(nd) operation. Therefore, a reliable modality for intraoperative LOS evaluation and management would afford the surgeon real-time information that could help guide surgical procedure and planning. The updated causes, algorithm, and management of LOS during RLN neuromonitoring are reviewed and summarized.