Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3745_Библиотеки_им_академика_М_И_Перельмана

superior laryngeal and glossopharyngeal nerves, the marginal mandibular branch of the facial nerve, and the greater auricular and cervical sensory branches (Fig. 29.1).

The hypoglossal (XIIth) nerve descends into the neck between the internal carotid artery and the internal jugular vein. It then crosses the internal and the external carotid artery approximately 2–4 cm above the carotid bifurcation to enter the root of the tongue. It is a purely motor nerve, innervating all of the intrinsic muscles of the tongue and three extrinsic muscles: the styloglossus, hyoglossus and genioglossus. The function of the nerve is assessed by measuring tongue muscle activity. Patients are asked to engage in tasks requiring tongue strength, mobility and range of motion, namely to stick out their tongue, to move it from side to side, to raise it to the nose or lower it to the chin and to lick their lips [9]. Injury to the hypoglossal nerve, which can happen during dissection of a high bifurcation, can be avoided by following the ansa hypoglossi up to its junction with the hypoglossal nerve and by dividing the sternocleidomastoid artery and vein separately, since the nerve may be adherent to the posterior surface of these vessels [7]. Division of the ansa hypoglossi, which supplies motor innervation to the infrahyoid muscles, will not be clinically overt. However, it should be spared if possible, because it can be invaluable in cases of future laryngectomy/laryngoplasty. In contrast, injury to the hypoglossal nerve is a serious complication, causing deviation of the protruding tongue to the ipsilateral side, while the relaxing tongue deviates to the contralateral side. Inarticulate speech and clumsy mastication will also ensue, whereas bilateral injury may cause life-threatening airway obstruction.

The superior laryngeal nerve arises from the vagus (Xth) nerve near the jugular foramen and passes diagonally behind the internal and external carotid artery before dividing into an internal sensory branch, supplying sensation to the mucosa of the larynx and an external motor branch, supplying innervation to the cricothy­roid muscle and the inferior pharyngeal constrictor. Assessment of the superior laryngeal nerve is done by asking the patient to produce tones of the upper range for about 15 s [9]. Injury to the superior laryngeal nerve can occur if the clamp is placed away from the origin of the external carotid artery and will cause voice fatigue and loss of high-pitch phonation.

mistaken for the ansa hypoglossi and severed erroneously. The recurrent laryngeal nerve is motor to all of the muscles of the larynx except for the cricothyroid muscle, and sensory to the mucosa below the vocal cords. Assessment of its function can be made by laryngoscopy as well as by asking the patient to produce sounds of the lower range [9]. In cases of recurrent laryngeal nerve injury, laryngoscopy will reveal paral­ysis of the ipsilateral vocal cord in a median or paramedian position, resulting in hoarseness and loss of effective cough mechanism. However, it should be noted that postoperative hoarseness does not necessarily imply damage to the recurrent laryn­geal nerve. Injury of the vocal cords during intubation, with subsequent oedema or haematoma formation, is a fairly frequent cause of postoperative hoarseness [18, 20]. [Q3: A] Differential diagnosis will be made by indirect laryngoscopy.

It should also be noted that vocal cord paralysis of degenerative aetiology is sometimes seen in elderly people. It is therefore recommended that all people scheduled for carotid endarterectomy should undergo preoperative examination of the vocal cords by indirect laryngoscopy. [Q1: C] Such an examination is of the utmost importance in patients with a history of thyroidectomy or contralateral endarterectomy. Preoperative evaluation should be completed with examination of the IXth and XIIth cranial nerves in order to document possible pre-existing cranial nerve deficits.

In the great majority of cases, cranial nerve injuries are caused by blunt trauma, due to excessive retraction. Less common causes are injuries by forcers, electro­cautery or the application of arterial clamps. Therefore, most of the cranial nerve injuries are transient and complete recovery occurs within 6 months and usually within 4–6 weeks [9, 11, 14, 18]. Thus, follow-up examination is recommended at 2 months to verify recovery and, in cases of persistent paralysis, at 6 months. [Q4: C] Extended follow-up will identify the small subset of patients with delayed (>6 months) complete nerve recovery.