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RLN injury, https://www.ncbi.nlm.nih.gov/books/NBK560832/ - Coggle Diagram
RLN injury
Care
Care must be taken in identifying the RLN, which may be found laterally on the thyroid (rather than posterior) or stretched anteriorly over a nodule.
The RLNs should then be identified. The course of the right RLN is more oblique than the left RLN. The nerves can be most consistently identified at the level of the cricoid cartilage.
The inferior thyroid vessels are dissected, skeletonized, ligated, and divided as close to the surface of the thyroid gland as possible to minimize devascularization of the parathyroids (extracapsular dissection) or injury to the RLN.
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Intraoperative RLN and external laryngeal nerve monitoring techniques are being increasingly used during thyroid and parathyroid surgery.
Both continuous monitoring using endotracheal tube electrodes and intermittent monitoring by periodic stimulation and laryngeal palpation are used
Currently, adequate RLN monitoring includes (a) stimulation of the vagus nerve prior to any dissection in the tracheoesophageal groove; (b) stimulation of the RLN prior to resecting the thyroid; (c) stimulation of the most proximally exposed portion of the RLN after the ligament of Berry has been completely divided; and (d) stimulation of the vagus nerve after complete hemostasis has been achieved on that side of the neck prior to closing or going on to the opposite lobe.
TTT
If the injury is recognized intraoperatively, most surgeons advocate primary reapproximation of the perineurium using nonabsorbable sutures.
The primary treatment options for recurrent laryngeal nerve injury include voice therapy or surgery.
Less serious RLN injuries in which there is no definite transection of the nerve can usually be monitored for around six months with voice therapy
Type 1 thyroplasty involves making an external incision to place an implant that permanently moves the affected vocal cord medially.
After a period of conservative treatment, vocal fold medialization techniques can be implemented. This moves the affected vocal cord closer to the unaffected vocal cord, creating improved contact.
Injection laryngoplasty is when the affected vocal cord is injected with a material, filling the vocal cord and moving it medially. These injectables can include carboxymethylcellulose, hyaluronic acid derivatives, collagen derivatives, calcium hydroxyapatite, or autologous fat/fascia
Arytenoid adduction is a procedure that involves placing a permanent suture through the muscular portion of the arytenoid cartilage. This pulls the affected vocal cord medial to correct vocal cord paralysis secondary to RLN injury. The procedure is often utilized in conjunction with other corrective procedures
Anatomy
The left RLN arises from the vagus nerve where it crosses the aortic arch, loops around the ligamentum arteriosum, and ascends medially in the neck within the tracheoesophageal groove.
The right RLN arises from the vagus at its crossing with the right subclavian artery. The nerve usually passes posterior to the artery before ascending in the neck, its course being more oblique than the left RLN
Along their course in the neck, the RLNs may branch, and pass anterior, posterior, or interdigitate with branches of the inferior thyroid artery necessitating identification of the RLN before the arterial branches can be ligated
The right RLN may be nonrecurrent in 0.5% to 1% of individuals and often is associated with a vascular anomaly. Nonrecurrent left RLNs are rare but have been reported in patients with situs inversus and a right-sided aortic arch.
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The RLNs innervate all the intrinsic muscles of the larynx, except the cricothyroid muscles, which are innervated by the external laryngeal nerves.
Effect of injury
Injury to one RLN leads to paralysis of the ipsilateral vocal cord, which comes to lie in the paramedian or the abducted position.
The paramedian position resultsin a normal but weak voice, whereas the abducted position leads to a hoarse voice and an ineffective cough.
Bilateral RLN injurymay lead to airway obstruction, necessitating emergency tracheostomy,or loss of voice.
If both cords come to lie in an abducted position, air movement can occur, but the patient has an ineffective cough and is at increased risk of repeated respiratory tract infections from aspiration.
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At the conclusion of the operation, if there is suspicion of an RLN injury, direct laryngoscopy is diagnostic
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If paralysis of the cords is not permanent, function may return 1 to 2 months after injury
With bilateral RLN injury, the chance of a successful extubation is poor
Unilateral vocal cord paralysis is typically iatrogenic in origin,25 following surgery to the thyroid, parathyroid, carotid, or cardiothoracic structures
the left vocal cord is more commonly involved secondary to the longer course of the recurrent laryngeal nerve (RLN) on that side, which extends into the thoracic cavity.
When anterior approaches to the cervical spine are performed, however, the right RLN is at an increased risk, because it courses more laterally to the tracheoesophageal complex.
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