Study on Microsurgical Anatomy of External Branch of Superior Laryngeal Nerve Related to Carotid Endarterectomy.

OBJECTIVE: To explore the methods of protecting the external branch of the superior laryngeal nerve during carotid endarterectomy through microsurgical anatomic study of the external branch of the superior laryngeal nerve in cadaveric specimens. METHODS: A total of 30 cadaveric specimens (60 sides) were dissected to measure the thickness of the external branch of the superior laryngeal nerve. A triangular area was exposed, bounded by the lower border of the digastric muscle superiorly, the medial edge of the sternocleidomastoid muscle laterally, and the upper border of the superior thyroid artery inferiorly. The probability of the occurrence of the external branch of the superior laryngeal nerve in this area was observed and recorded. The distance among the midpoint of the external branch of the superior laryngeal nerve in this area with the tip of the mastoid process and the angle of the mandible as well as the bifurcation of the common carotid artery was measured and recorded. RESULTS: Among 30 specimens of cadaveric heads (60 sides) examined 53 external branches of the superior laryngeal nerve were observed while 7 were absent. Of the 53 branches observed, 5 were located outside the anatomic triangle region mentioned above, while the remaining 48 branches were located within the anatomic triangle region with a probability of ~80%. The thickness of the midpoint of the external branches of the superior laryngeal nerve within the anatomic triangle region was 0.93 mm (0.72-1.15 mm [±0.83 SD]), located 0.34 cm [-1.62-2.43 cm (±0.96 SD)] posterior to the angle of the mandible, 1.28 cm (-1.33 to 3.42 cm (±0.93 SD)] inferiorly; 2.84 cm (0.51-5.14 cm±1.09 SD) anterior to the tip of the mastoid process, 4.51 cm (2.82-6.39 cm±0.76 SD) inferiorly; 1.64 cm [0.57-3.78 cm (±0.89 SD)] superior to the bifurcation of the carotid artery. CONCLUSIONS: During carotid endarterectomy procedure, using the cervical anatomic triangle region, as well as the angle of the mandible, the tip of the mastoid process, and the bifurcation of the carotid artery as anatomic landmarks, is of significant clinical importance for protecting the external branches of the superior laryngeal nerve.

Intermediate results of 306 recurrent laryngeal nerve sections for spastic dysphonia.

Recurrent laryngeal nerve section for spastic dysphonia was first performed in 1975 because prior forms of treatment had failed. Virtually every patient has had a detailed postoperative follow-up which includes a tape recording and a self-assessment questionnaire. The majority of patients remain free of spasticity at this medium-term follow-up. In some, spasticity recurred with less than preoperative severity. A small percentage of patients have a persistent breathy phonation. The first group is treated with vocal fold lateralization procedure using the CO2 laser; the second, with Teflon. When needed, voice therapy is also given. This paper provides a basis for diagnosis, indications for surgery, primary and secondary surgical techniques, encountered problems, and medium-term follow-up results.

Long-term follow-up of recurrent laryngeal nerve avulsion for the treatment of spastic dysphonia.

Long-term follow-up of 3 to 7 years is reported on 18 patients who had undergone recurrent laryngeal nerve avulsion (RLNA) for the treatment of adductor spastic dysphonia (SD). Data on neural regrowth after previous recurrent laryngeal nerve section (RLNS) are presented in 2 of these 18 patients. We introduced RLNA as a modification of standard RLNS to prevent neural regrowth to the hemiparalyzed larynx and subsequent recurrence of SD. We have treated a total of 22 patients with RLNA, and now report a 3- to 7-year follow-up on 18 of these 22 patients. Resolution of symptoms was determined by routine follow-up assessment, perceptual voice analysis, and patient self-assessment. Sixteen of 18, or 89%, had no recurrence of spasms at 3 years after RLNA as determined at routine follow-up. Two of the 16 later developed spasms after medialization laryngoplasty for treatment of weak voice persistent after the avulsion. This yielded a total of 14 of 18, or 78%, who were unanimously judged by four speech pathologists to have no recurrence of SD at the longer follow-up period of 3 to 7 years. Two of these 4 patients were judged by all four analysts to have frequent, short spasms. The other 2 were judged by two of four analysts to have seldom, short spasms. Three of 18 patients presented with recurrent SD after previous RLNS. At the time of subsequent RLNA, each patient had evidence of neural regrowth at the distal nerve stump as demonstrated by intraoperative electromyography and histologic evaluation of the distal nerve stump. One remained free of SD following RLNA, 1 was free of spasms at 4 years after revision avulsion but developed spasms after medialization laryngoplasty, and the final patient developed spasms 3.75 years after revision RLNA. Medialization laryngoplasty with Silastic silicone rubber was performed in 6 of 18, with correction of postoperative breathiness in all 6, but with recurrence of spasm in 3. Spasms resolved in 1 of these with downsizing of the implant. We conclude that RLNA represents a useful treatment in the management of SD in patients not tolerant of botulinum toxin injections.

Independent effects of denervating the cricothyroid muscle and stenting on the anterior cricoid split: canine model.

The anterior cricoid split (ACS) has gained in popularity since its introduction in 1980, for the treatment of the difficult to extubate child. The procedure allows a successful extubation and avoids a tracheotomy about 75% of the time. How the ACS allows extubation remains poorly understood. Animal research has shown that in the canine model the ACS results in a gap in the cricoid cartilage with a subjective increase in the subglottic space (Senders and Eisele, 1978). This gap in the cricoid cartilage develops whether or not an endotracheal tube stent is used. This experiment was designed to quantitatively evaluate the effect of the ACS on the subglottic space with or without the use of the stent, and to evaluate the effect of the cricothyroid muscle on the ACS procedure. The results show that the ACS does result in an increase in the subcricoid space, and that the use of an endotracheal tube stent does result in a larger increase. The cricothyroid muscle has a strong immediate effect on the gap in the cricoid cartilage, which is eliminated by sectioning the external laryngeal nerve. The long-term effects of sectioning the external laryngeal nerve on the gap in the cricoid cartilage were not conclusive.

Unilateral vocal fold paralysis: a review of the current methods of surgical rehabilitation.

This review article discusses the surgical treatment of patients suffering from unilateral vocal fold paralysis who have already been assessed and considered appropriate candidates for surgery. There are currently three main methods of surgical rehabilitation; injection medialisation; laryngeal framework surgery; re-innervation procedures.

A clear map of the lower cranial nerves at the superior carotid triangle.

BACKGROUND: The lower cranial nerves must be identified to avoid iatrogenic injury during skull base and high cervical approaches. Prompt recognition of these structures using basic landmarks could reduce surgical time and morbidity. METHODS: The anterior triangle of the neck was dissected in 30 cadaveric head sides. The most superficial segments of the glossopharyngeal, vagus and its superior laryngeal nerves, accessory, and hypoglossal nerves were exposed and designated into smaller anatomic triangles. The midpoint of each nerve segment inside the triangles was correlated to the angle of the mandible (AM), mastoid tip (MT), and bifurcation of the common carotid artery. RESULTS: A triangle bounded by the styloglossus muscle, external carotid artery, and facial artery housed the glossopharyngeal nerve. This nerve segment was 0.06 ± 0.71 cm posterior to the AM and 2.50 ± 0.59 cm inferior to the MT. The vagus nerve ran inside the carotid sheath posterior to internal carotid artery and common carotid artery bifurcation in 48.3% of specimens. A triangle formed by the posterior belly of digastric muscle, sternocleidomastoid muscle, and internal jugular vein housed the accessory nerve, 1.90 ± 0.60 cm posterior to the AM and 2.30 ± 0.57 cm inferior to the MT. A triangle outlined by the posterior belly of digastric muscle, internal jugular vein, and common facial vein housed the hypoglossal nerve, which was 0.82 ± 0.84 cm posterior to the AM and 3.64 ± 0.70 cm inferior to the MT. CONCLUSIONS: Comprehensible landmarks can be defined to help expose the lower cranial nerves to avoid injury to this complex region.

Incidence of cranial nerve injuries after carotid eversion endarterectomy with a transverse skin incision under regional anaesthesia.

OBJECTIVES: The objective of this prospective study was to evaluate the incidence and distribution of cranial nerve injuries after carotid eversion endarterectomy (EEA) performed under regional anaesthesia using a transverse skin incision. PATIENTS AND METHODS: The study included 165 patients and 180 carotid arteries. All patients had a standard pre-operative assessment performed by a neurologist and ENT specialist. All carotid endarterectomies were performed by the eversion technique under regional anaesthesia. RESULTS: Ten cranial nerve injuries were observed. Seven patients had injuries of the marginal mandibular branch of the facial nerve, two patients had lesions of the hypoglossal nerve, and one patient had an injury of the recurrent laryngeal nerve. Eleven patients developed hoarseness without cranial nerve injury. Injuries of the marginal mandibular branch recovered after 3-8 months (mean 5.2 months). Both hypoglossal nerve injuries recovered after 4 months. The patient with the recurrent laryngeal palsy had no improvement after 19 months. Patients with hoarseness secondary to laryngeal haematoma recovered within 1 month. CONCLUSION: The incidence of cranial nerves injury after carotid EEA under regional anaesthesia is comparable to that reported for conventional carotid surgery. Postoperative hoarseness is most frequently due to laryngeal haematoma.