Читать книгу Pearls and Pitfalls in Head and Neck Surgery - Группа авторов - Страница 7
ОглавлениеThyroid and Parathyroid Glands
Cernea CR, Dias FL, Fliss D, Lima RA, Myers EN, Wei WI (eds): Pearls and Pitfalls in Head and Neck Surgery. Basel, Karger, 2012, pp 2–3
DOI: 10.1159/000338528
1.1 How to Avoid Injury to the Inferior Laryngeal Nerve
Robert L. Ferrisa Ralph P. Tufanob
aUniversity of Pittsburgh Cancer Institute Hillman Cancer Center, Pittsburgh, Pa., and bDepartment of Otolaryngology- Head and Neck Surgery, Johns Hopkins University, Baltimore, Md., USA
P E A R L S
• Identifying the inferior laryngeal nerve (ILN) in primary thyroid surgery.
• Avoiding injury at Berry’s ligament.
• Identifying the ILN in reoperative surgery.
• Dissecting the ILN.
P I T F A L L S
• The nonrecurrent ILN.
• The inferior thyroid artery (ITA) as a landmark for the ILN.
• The branching ILN.
• How to avoid traction on the ILN.
• Pitfalls in neuromonitoring of the ILN.
• The challenge of goiter surgery (mediastinal and aberrant ILN course).
Introduction
The ILN contains motor and sensory fibers and contains 2-4 times as many adductor fibers as abductor fibers [1]. The right ILN usually runs underneath the right subclavian artery and common carotid artery to enter and run obliquely in the central compartment. The left ILN recurs around the ligamentum arteriosum and runs in the tracheoesophageal (TE) groove. A nonrecurrent ILN occurs more frequently on the right (0.63%) than the left (0.04%) [2, 3]. The ILN goes deep to the inferior constrictor muscle and this area represents the distal-most exposure of the ILN in the surgical field [4].
Practical Tips
Identifying the ILN in Primary Thyroid Surgery. The identification of the ILN lateral to a medially retracted thyroid lobe is most commonly used for routine cases and where limited access techniques are used (endoscopic and robotic). Identification of the ILN inferior to the thyroid gland may be advantageous for large goiters, but may still need to be carefully re-identified distally to avoid parathyroid gland devascularization. Identification of the ILN superiorly at the most distal course of the ILN may be helpful for large substernal goiters, but is technically more challenging than the other approaches.
Avoiding Injury at Berry’s Ligament. Berry’s ligament is tough, well vascularized, and anchors the thyroid lobe to the trachea. The course of the ILN in this area is variable as it may run underneath, over, or within the ligament. Branching of the ILN may also be readily apparent in this area and all branches must be accounted for before transection of Berry’s ligament [5]. ILN monitoring may be useful to protect all motor branches.
Identifying the ILN in Reoperative Surgery: The inferior approach to finding the ILN is best for reoperative cases. This area is typically free of significant scarring. Skeletonizing the common carotid artery on the right and left allows room to work medial and deep to the artery to identify the recurrent laryngeal nerves on both the right and left.
Dissecting the ILN. There should be minimal traction on the ILN when dissecting. This can be best accomplished with fine tip dissectors along the fascia of the ILN. At no time should a nerve hook be utilized.
The Nonrecurrent ILN. This entity occurs in approximately 0.5% of cases, and is virtually always present only on the right side where it coexists with a retroesophageal, anomalous right subclavian artery. The nonrecurrent ILN has a more oblique or transverse course and may have variable association with the inferior or superior thyroid artery. The extremely rare occurrence of a left-sided nonrecurrent ILN is associated with right-sided aortic arch (situs inversus).
The ITA as a Landmark for the ILN. To identify the ILN, many surgeons use the ITA which crosses over the nerve as it courses through the TE groove and the ligament of Berry. However, an important pitfall is that approximately one third of ILN may lie either anterior to or integrally associated with the branches of the ITA. Thus, the ITA is not a reliable landmark for avoiding ILN injury.
The Branching ILN. In the majority of cases (60-70%), the ILN runs in the TE groove. However, the ILN may branch near the cricothyroid insertion in up to one third of the cases. Motor branches are at risk laterally or even anteriorly to the trachea, particularly with large or posterior nodules. The ILN is usually dorsolateral to the ligament of Berry; however, the branched nerve fibers may also pass posteromedially or even through this ligament.
Finding the ILN during Excision of Intrathoracic Goiters. The orientation and relationship of the goiter to surrounding structures such as the ILN may be demonstrated by a preoperative CT scan. In intrathoracic goiters, the ILN is usually in the TE groove. However, when the intrathoracic portion of the goiter involves the posterior mediastinum (<5%), the nerve may be displaced anteriorly. Occasionally, retrograde dissection of the ILN may be necessary near the ligament of Berry.
Pitfalls of Neuromonitoring. Although a number of thyroid surgeons employ routine intraoperative ILN monitoring, the tube may be dislodged and anatomic variation may prevent utility of stimulation or passive monitoring, neither of which have been demonstrated to lower rates of nerve injury. The use of loupe magnification (2.5-3.5×) helps to optimize visualization and minimize risk of trauma to the ILN.
Avoiding Stretch Injury to the ILN. The most common form of ILN injury is neuropraxia, or traction on the ILN. Overly aggressive rotation of the laryngotracheal complex or dissection and shearing using a clamp near its insertion at the cricothyroid membrane may contribute to ILN traction injury. This type of injury may be permanent, and is avoided by careful surgical technique and gentle handling of tissues. Avoiding persistent and prolonged rotation of the laryngotracheal complex will also avoid kinking or traction injury at the cricothyroid membrane insertion of the ILN.
References
1 Gacek RR, Malmgren LT, Lyon MJ: Localization of adductor and abductor motor nerve fibers to the larynx. Ann Otol Rhinol Laryngol 1971;86: 771.
2 Edwards JE: Congenital malformations of the heart and great vessels. Malformation of the aortic arch system; in Gould SE (ed): Pathology of the Heart. Springfield, Charles C. Thomas, 1953.
3 Henry JF, Audiffret J, Denizot A: The nonrecurrent inferior laryngeal nerve: review of 33 cases, including two on the left side. Surgery 1988;104: 977.
4 Randolph GW: Surgery of the Thyroid and Parathyroid Glands. Philadelphia, Saunders, 2003.
5 Kandil E, Abdelghani S, Friedlander P, Alrasheedi S, Tufano RP, Bellows CF, Slakey D: Motor and sensory branching of the recurrent laryngeal nerve in thyroid surgery. Surgery 2011;150:1222–1227.
6 Ardito G, Revelli L, D’Alatri L, Lerro V, Guidi ML, Ardito F: Revisited anatomy of the recurrent laryngeal nerves. Am J Surg 2004;187:249–253.
7 Steinberg JL, Khane GJ, Fernandes CM, Nel JP: Anatomy of the recurrent laryngeal nerve: a redescription. J Laryngol Otol 1986;100:919–927.
Robert L. Ferris, MD, PhD, FACS
UPMC Endowed Professor of Head and
Neck Oncology Surgery
Vice-Chair for Clinical Operations & Chief,
Division of Head and Neck Surgery
Associate Director for Translational
Research Co-Leader
Cancer Immunology Program
University of Pittsburgh Cancer Institute
200 Lothrop Street
Pittsburgh, PA 15213 (USA)
E-Mail ferrrl@upmc.edu
