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The use of intraoperative neuromonitoring (IONM) is getting more common in thyroidectomy. The data obtained by the usage of IONM regarding the laryngeal nerves’ anatomy and function have provided important contributions for improving the standards of the thyroidectomy. These evidences obtained through IONM increase the rate of detection and visual identification of recurrent laryngeal nerve (RLN) as well as the detection rate of extralaryngeal branches which are the most common anatomic variations of RLN. IONM helps early identification and preservation of the non-recurrent laryngeal nerve. Crucial knowledge has been acquired regarding the complex innervation pattern of the larynx. Extralaryngeal branches of the RLN may contribute to the motor innervation of the cricothyroid muscle (CTM). Anterior branch of the extralaryngeal branching RLN has always motor function and gives motor branches both to the abductor and adductor muscles. In addition, up to 18% of posterior branches may have adductor and/or abductor motor fibers. In 70–80% of cases, external branch of superior laryngeal nerve (EBSLN) provides motor innervation to the anterior 1/3 of the thyroarytenoid muscle which is the main adductor of the vocal cord through the human communicating nerve. Furthermore, approximately 1/3 of the cases, EBSLN may contribute to the innervation of posterior cricoarytenoid muscle which is the main abductor of ipsilateral vocal cord. RLN and/or EBSLN together with pharyngeal plexus usually contribute to the motor innervation of cricopharyngeal muscle that is the main component of upper esophageal sphincter. Traction trauma is the most common reason of RLN injuries and constitutes of 67–93% of cases. More than 50% of EBSLN injuries are caused by nerve transection. A specific point of injury on RLN can be detected in Type 1 (segmental) injury, however, Type 2 (global) injury is the loss of signal (LOS) throughout ipsilateral vagus-RLN axis and there is no electrophysiologically detectable point of injury. Vocal cord paralysis (VCP) develops in 70–80% of cases when LOS persists or incomplete recovery of signal occurs after waiting for 20 min. In case of complete recovery of signal, VCP is not expected. VCP is temporary in patients with incomplete recovery of signal and permanent VCP is not anticipated. Visual changes may be seen in only 15% of RLN injuries, on the other hand, IONM detects 100% of RLN injuries. IONM can prevent bilateral VCP. Continuous IONM (C-IONM) is a method in which functional integrity of vagus-RLN axis is evaluated in real time and C-IONM is superior to intermittent IONM (I-IONM). During upper pole dissection, IONM makes significant contributions to the visual and functional identification of EBSLN. Routine use of IONM may minimalize the risk of nerve injury. Reduction of amplitude more than 50% on CTM is related with poor voice outcome.
The use of thyroidectomide intraoperative nerve monitoring (IONM) is increasing. IONM has obtained many data on the anatomy and nerve injuries of the larynx nerve, and they have made a significant contribution to the increase in thyroidectomy standards. These evidence: Recurren increases the detection of the laryngeal nerve (RLN), the visual identification. The most common anatomical variation of RLN increases the detection rate of the extra-alaringeal branches. The non-recurrent guarantees the early detection and preservation of the laryngal nerve. Important data on Larinxin complex engine inervation has been obtained. RLN or extralaringeal RLN branches may contribute to the motor inertia of the cryothyroid muscle. The front branch of the extra-ingular RLNs has a constant motor function and provides motor fiber to both the abductor and adductor muscles. In addition, up to 18% of the rear branches may also contain adductor and/or abductor motor fiber. SLSE provides motor inervation to the main addictor of the vocal cord through the human conjunctive nerve by 70% to 80% to the thyro-arythenoid muscle 1/3 front. In approximately 1/3 of cases, SLSE also contributes to the posterior krikoaritenoid muscle inervation, which is the main abductor muscle of the ipsilateral vocal cord. The major component of the upper ozephageal sphincterine is the motor inervation of the cryopharyngeal muscle, in addition to the pharyngeal plexus, which is usually contributed to RLN and/or SLSE. The most common cause of 67-93% of RLN injuries is traction trauma. More than 50% of SLSE injuries are nerve cuts. In the case of RLN injury, the situation where a specific injury point on the nerve is type 1 (segmental) signal loss, and when there is no electrophysically detectable injury point after injury, it is type 2 (global) signal loss throughout the ipsilateral vagus-RLN axis. If the signal loss develops, the signal loss persists when 20 minutes are expected, or if the signal improves incomplete, the 70%-80% vocal cord paralysis (VCP) develops, the complete signal improvement does not develop, the VCP does not develop. In patients with incomplete signal healing, VCP is temporary and no permanent VCP is observed. In 15% of RLN injuries there are visual changes, while IONM RLN can estimate 100% of injuries. IONM can prevent bilateral VCP. Continuous IONM (C-IONM) is a method superior to the interval IONM where the functional integrity of the vagus/RLN axis is assessed in real time. During the upper pol disection, IONM contributes significantly to the visual and functional determination of SLSE. Routine use of IONM can minimize the risk of nerve injury. A decrease of more than 50% in the cryothyroid muscle amplitude is associated with the poor sound results of the patient. (SETB-2021-05-159)
Alan : Sağlık Bilimleri
Dergi Türü : Ulusal
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