Comparison of stimulating dissector and intermittent stimulating probe for the identification of recurrent laryngeal nerve in reoperative setting

Thyroid cartilage needle vs. endotracheal tube electrodes in EBSLN monitoring during thyroidectomy

During thyroidectomy, both needle electrodes (NE) and endotracheal tube electrodes (ETE) can be used. Incomplete contact of the endotracheal tube electrode with the vocal cords, endotracheal tube electrode may hinder an optimal outcome and even result in an inability to obtain an electromyography wave while neuromonitoring the external branch of the superior laryngeal nerve (EBSLN). There is no study that compares NE and ETE for EBSLN monitoring. Therefore, this study compares NE and ETE recordings during EBSLN monitoring. Twenty-six consecutive patients undergoing total thyroidectomy were included in this study. Intraoperative neuromonitoring was performed simultaneously with both NEs and ETEs. Pre-resection (V1, R1, and S1) and post-resection (V2, R2, and S2) amplitudes and latencies were recorded for both types of electrodes. The Mann-Whitney U test was used for statistical analysis. Twenty-one women and five men were included, and 52 nerves at risk were evaluated. The mean amplitudes for right S1 (314 vs. 168 µV, p = 0.009) and right S2 (428 vs. 161 µV, p: 0.001) and for left S1 (346 vs. 229 µV, p: 0.017) and left S2 (413 vs. 229 µV, p: 0.009) were statistically higher for the NE group. All amplitudes obtained using NEs, except on the left for V1, R1, V2, and R2, were statistically higher than those obtained using ETEs. There was no loss of signal or vocal cord palsy in the patients. There were no needle-related complications. EBSLN monitoring using NE is a safe alternative to ETE. With NE, higher amplitudes were obtained. Level of evidence: Level 3.

Recurrent Laryngeal Nerve Monitoring: Nuts and Bolts

Intraoperative neuromonitoring (IONM) of the laryngeal nerves has become an important tool for neck endocrine surgery. In this article, the authors review the current evidence behind its use in neck endocrine procedures. The subtypes of IONM, including intermittent IONM, continuous vagal IONM (vagal-CIONM), and laryngeal adductor reflex CIONM, will be discussed. Finally, the authors review recent advances in IONM, and how standardization of outcomes reporting will help minimise conjecture regarding the usefulness of IONM.

Recent Developments of Intraoperative Neuromonitoring in Thyroidectomy

At present, intraoperative neuromonitorization (IONM) with surface electrode-based endotracheal tube (ETT) is a standard method in thyroidectomy and can be performed either intermittently IONM (I-IONM) or continuously IONM (C-IONM). Despite the valuable contribution of I-IONM to the thyroidectomy, it still has limitations regarding the recording electrodes and stimulation probe. New approaches for overcoming the limitations of I-IONM and developing the method are taking attention. Most of the technical issues of IONM with surface electrode-based ETT are related with inadequate contact of electrodes to the vocal cords. Nowadays, efficiency of various recording electrodes is under investigation. Recording electrodes such as needle electrodes applied to thyroarytenoid or posterior cricoarytenoid muscle (PCA), surface electrodes applied to the PCA, and needle or adhesive electrodes applied to the tracheal cartilage or skin, can make safe recordings similar to the ETT electrodes. Despite their invasiveness, needle electrodes record higher electromyography (EMG) amplitudes than tube electrodes do. Adhesive surface electrodes make safe EMG recordings, although amplitudes of these electrodes are usually lower than those of the tube electrodes. These different types of electrodes are less affected by tracheal manipulations and amplitude changes are lower compared to the tube electrodes.

During C-IONM, an additional stimulation probe is applied to the vagus nerve after dissecting the nerve circumferentially. Recently, without applying a probe, a new continuous monitorization method called laryngeal adductor reflex CIONM (LAR-CIONM) using sensorial, central, and motor components of LAR arch which is an automatic, primitive brainstem reflex protecting the tracheoesophageal tree from foreign body aspiration, has been implemented. Afferent track of LAR communicates laryngeal mucosa to the brainstem by internal branch of the superior laryngeal nerve and efferent track reaches larynx through recurrent laryngeal nerve. Total outcome of LAR activation is the closure of laryngeal entry by bilateral vocal cord adduction. In LAR-CIONM, a stimulus is given by an electrode from one side of surface electrode-based ETT and amplitude response of the LAR at the vocal cord is followed on the operation side. Recently, it has been reported that real-time EMG response can be obtained with stimulation probe cables applied to dissectors or energy devices during the dissection through I-IONM.